diagenesis and reservoir-quality evolution of paralic, shallow …172262/fulltext01.pdf ·...

ACTA

UNIVERSITATIS

UPSALIENSIS

UPPSALA

2008

Digital Comprehensive Summaries of Uppsala Dissertationsfrom the Faculty of Science and Technology 448

Diagenesis and Reservoir-QualityEvolution of Paralic, ShallowMarine and Fluvio-lacustrineDeposits

Links to Depositional Facies and SequenceStratigraphy

OSAMA AHMED HLAL

ISSN 1651-6214ISBN 978-91-554-7237-5urn:nbn:se:uu:diva-8986

�� !"� !##" �� #$## %� �&� �� %�� % '&��&�( )&� �� *�� +��&(

��

�� , �( !##"( �� -��./�� +�� % '�� 0&��* �� 1��.�� ( 2�3� � �� 1�� 0�4�� 0��&�( �� ( �� 55"( �6 ��( ��( 7089 :;".:�.665.;!<;.6(

2�3�� %�� 4�� &� �� % �� % �� &�� % �� % ��4�� ( )&�� &�� &�� &�� & �� %�� 4�� &� �� %�� %�� &� ��.��%�� & �� &�� $ =�> ��.*��&�� =��> �� % �� &�� =��> �� % ��. �� .�� =��> �� %�� (+�� %�� %�� &� �� % �� %�

�� % �� % �&�� % �� 4�� &��* �� %��.�� (�� &�� &�� *��&� �&� �� % �� %�� 4�� &� ��$ =�> �� =�� 4�� 3�� >� �� .�� %� ��4�� &� �� =�(�( �� %�� %�� 10> �� 4�� &� �� %�� % �&� �� &��&�� 0)� =��> �� &� %�� % �� &� �� % %��*�3 �� &�� %� �� 4�� =��> �� 3��?�� % %��*�3 �� &� %�� 0) �� *&�� 3�� &� �� )0) �� =��> %�� % ��&�� &� )0) �� =�> %�� % �� &�� .�� .�� &�� &� )0) �&� � �&� �0)�� * �&� �� %�� )0 �� 10� =��> �� *��& =@�",

�.'�8A .��(6B � .6(5B> �� 1�.��C�3�� =@�",

�.'�8A .�#("B �

.:(�B> �� & )0) �� 0) �� =��> �� 4��? ��*�&� �� &� �0) �� *�� &� �� % �� .��&��C�&�� =��> �� % ��.�� &� )0) �� &� � �&��0) �� &� �� % ��&��C�&�� &� %�� =��> �&�� 4��? �� &� �� % 4��?��*�&�� &�� % �� %��.�� ( )&��%�� &� �� % �� &� �� % �� %�� 4�� &�� *��%��& � �� &�� (

� �� 0�� &��* �� %��.�� 4�� 4�� &�

�� ! � �� "�� ! #��$ %&! �� ! �"'()*+&��! ��

D ,�� &�� !##"

7009 ��6�.�!�57089 :;".:�.665.;!<;.6��$�$��$��$��.":"� =&��$CC��(3�(��C��E��A��$�$��$��$��.":"�>

Dedicated to:

Parents, brothers and sisters And

My wife and my daughter

List of Papers

This thesis is based on the following papers, which will be referred to in the following text by their Roman numerals.

� Hlal, O., Morad, S., and El-Khoriby, E. (2008) Diagenetic

evolution of aggradational and progradational fan-delta Arenites: Evidence from the Abu Alaqa group (Miocene), Gulf of Suez, Egypt. Journal of Petroleum Geology, In review.

�� Hlal, O., Morad, S., Brazil, F., and Pereira, E. (2008) Diagenetic and reservoir-quality evolution of shoreface sand-stones in sequence stratigraphic context: The Ponta Grossa Formation (Devonian), Paraná Basin, Brazil. SedimentaryGeology, In review.

�� Hlal, O., Annersten, H., and Morad, S. (2008) Mössbauer study of diagenetic Fe-rich minerals in Devonian clastic rocks of the Ponta Grossa Formation, Paraná Basin, Brazil. ClayMinerals, In review.

�V Hlal, O., Morad, S., and López-Blanco, M. (2008) Linking

the distribution of carbonate cement to sequence stratigraphy of delta complex sandstones: evidence from the Roda sand-stone Formation (Eocene), South-Pyrenean Foreland Basin, NE Spain. Sedimentary Geology, To be submitted.

V Hlal, O., Luo, J., Morad, S., Salem A., Yan, S., Zhang, X.,

and Xue, J., (2008) The diagenetic and reservoir-quality evo-lution of fluvial and lacustine-deltaic sandstones: evidence from Jurassic and Triassic sandstones of the Ordos Basin, Northwestern China, Journal of Petroleum Geology, In re-view.

Contents

Introduction.....................................................................................................9

Aims of the study ..........................................................................................14

Sequence Stratigraphy of Paralic, Shallow Marine and Fluvio-lacustrine Deposits ........................................................................................................16

Parasequences and marine flooding surfaces ...........................................17 Problems with stacking patterns...............................................................18 Systems tracts...........................................................................................19

Methodology.................................................................................................23

Important eogenetic alterations linked to sequence stratigraphy ..................26

Important mesogenetic alterations linked to sequence stratigraphy .............30

Reservoir quality evolution and conceptual predictive models within depositional facies and sequence stratigraphy ..............................................34

Model 1: summary model for distribution of diagenetic alterations and reservoir-quality evolution of progradational and aggradational sequences..................................................................................................................35

Figure 9: Simplified cartoons showing the most typical diagenetic features in the aggradational and progradational fan delta sequences........................36

Model 2: summary model of the diagenetic evolution of shoreface sandstone (paper II) ..................................................................................37 Model 3: summary model of impact of diagenetic modifications on reservoir quality of delta complex sandstone sandstones (paper IV) .......40 Model 4: summary model of impact of diagenetic modifications on reservoir quality of Jurassic and Triassic fluvial and lacustrine deltaic sandstones (paper V) ................................................................................42

Summary of the papers .................................................................................46 Paper I Diagenetic evolution of aggradational and progradational fan-delta Arenites: Evidence from the Abu Alaqa group (Miocene), Gulf of Suez, Egypt...............................................................................................46

Paper II Diagenetic and reservoir-quality evolution of shoreface sandstones in sequence stratigraphic context: The Ponta Grossa Formation (Devonian), Paraná Basin, Brazil ...........................................46 Paper III Mössbauer study of diagenetic Fe-rich minerals in Devonian clastic rocks of the Ponta Grossa Formation, Paraná Basin, Brazil .........47 Paper IV Linking the distribution of carbonate cement to sequence stratigraphy of delta complex sandstones: evidence from the Roda sandstone Formation (Eocene), South-Pyrenean Foreland Basin, NE Spain.........................................................................................................48 Paper V The diagenetic and reservoir-quality evolution of fluvial and lacustine-deltaic sandstones: evidence from Jurassic and Triassic sandstones of the Ordos Basin, Northwestern China ...............................49

Concluding Remarks.....................................................................................50

Summary in Swedish ....................................................................................52

Acknowledgements.......................................................................................54

References.....................................................................................................57

9

Introduction

Diagenesis and sequence stratigraphy have been formally treated as isolation from each other to unravel and predict reservoir quality dis-tribution successfully during the past three decades. Recently, it has been demonstrated that the spatial and temporal distribution of diagenetic alterations such as extensive calcite and dolomite cementa-tion can be closely related to key sequence stratigraphic surfaces (Tay-lor et al., 1995; Morad et al., 2000; Ketzer et al., 2003a; Ketzer et al., 2003b; Al-Ramadan et al., 2005). The interplay between sequence stratigraphy and diagenesis en-ables the prediction of spatial and temporal distribution of diagenetic alterations, and thus of post-depositional evolution of reservoir quality of sandstones. This study approach may also provide important insight into the formation of diagenetic baffles and barriers for fluid flow, which can act as reservoir compartments and seals. Unraveling diagenetic changes in a sequence stratigraphic framework has gained significant interest in recent years and has been thoroughly applied fairly extensively to carbonate rocks (Read and Horbury 1993; Tucker 1993; Moss and Tucker, 1996). Although the relationships between diagenetic alterations and changes in the relative sea level in clastic rocks are gaining increasing attention (Taylor et al., 1995, 2000; Loomis and Crossey, 1996; South and Talbot, 2000; Ketzer et al., 2002; Al-Ramadan et al., 2005), the linkages are less straightforward, and thus not fully explored yet (Ketzer et al., 2003). Diagenetic altera-tions in clastic rocks that are relatively well constrained within se-quence stratigraphy include the distribution of carbonate cements and clay minerals (Taylor et al., 1995; Morad et al. 2000; Ketzer et al., 2002; 2003a; Al-Ramadan et al., 2005). In these studies, extensive early diagenetic carbonate cementation was linked to surface. The sequence stratigraphy approach can provide useful information on the diagenetic evolution of siliciclastic deposits which is complex and controlled by several inter-related parameters (Fig. 1), including

10

Figure 1: Diagenesis is controlled by a complex array of interrelated parameters. Modified after Stonecipher et al. (1984).

Figure 2: A triangular plot of extrabasinal and intrabasinal grains. The latter grains are incorporated in sand during transgressive events. Modified after Zuffa 1980).

11

changes in:Detrital composition, particularly the proportion of extrabasinal and intrabasinal grains (Fig. 2; Garzanti, 1991; Amorosi, 1995; Zuffa et al., 1995, Ketzer et al., 2002), which is strongly con-trolled primarily by the tectonic setting of the basin, paleoclimatic conditions, source rocks, and changes in relative sea level. (ii) Pore-water chemistry (Fig. 3), which can shift between meteoric, marine and brackish composition (Mckay et al. 1995, Morad at al 2000). Regression may leads to subaerial exposure of at least part of the shelf and concomitant flushing of shoreface and deltaic sediments by meteoric waters. Conversely, transgression renders pore waters to be dominated by marine composition. (iii) Residence time of sediments under certain geochemical condi-tions (Fig. 3; Wilkinson 1989, Taylor et al 1995, Morad 2000). For instance rapid rise in relative sea level would ensure prolonged marine pore water diagenesis. Conversely, rapid fall in relative sea level re-sults in meteoric-water diagenesis, which would be controlled by cli-matic conditions. (iv) Abundance and type of organic matter (Cross, 1988; Fig. 4).

The depositional environments exert considerable controls on the diagenetic evolution of sedimentary sequences. These controls are most prominent during eodiagenesis being related to variations in pore water chemistry, sedimentation rates, types and amounts of organic-matter, degree of bioturbation, as well as to the textural characteristics (grain size, sorting), and architecture of the depositional facies. Facies architecture refers mainly to the thickness, geometry of sediment bod-ies, and sand/mud ratio, which control in turn, the extent and pattern of fluid flow. Variations in rates of sedimentation control the amounts of organic matter, degree of sediment reworking by bioturbation, and the residence time of sediments at the sediment-water or sediment-air interface (extent of near-surface eogenetic alterations). Pore waters in paralic and shallow marine environments have chemical compositions that are strongly influenced by the depositional waters, being ranging from largely meteoric, mixed marine-meteoric (i.e., brackish), and marine compositions, variations in depositional facies, (i.e. shoreface) have impact on the primary porosity and per-meability values, and on the mass flux and rates of diagenetic reac-tions.

12

Figure 3: A sketch showing the influence of changes in the relative sea level (RSL) on porewater composition in shelf and ramp sediments. A fall in RSL results in the incursion of meteoric waters and a basinward shift of the mixing zone. The opposite is true when a ris in RSL occurs, where porewaters in the shelf or ramp sediments become dominantly marine and the mixing zone is shifted landward. Modified after Morad et al. (2000) and Ketzer at al (2003b).

13

Figure 4: Growth model of carbonate (calcite or dolomite) concretion along various hypothetical pathways related to rate of sedimentation (i.e. rate of concretion burial below the sediment-water interface) and precipitation in the various geochemical zones of diagenesis. Slow sedimentation rates (path A) results in more extensive cementation (i.e. formation of continuously cemented sediment layer owing to longer residence time below the seafloor and prolonged time span of derivation of dissolved calcium and carbon from the overlying seawater. Modified after Wilkin-son et al. (1987). Diagenetic regimes used in this summary are sensu Morad et al. (2000; modified after Choquette and Pray, 1970), and include (i) eo-diagenesis, which occurs at near-surface and shallow-burial conditions (0-2 km of burial depth and <70ºC) and during which pore water chemistry is controlled by surface waters, (ii) mesodiagenesis (> 2 km and >70ºC), which is mediated by evolved formation waters, and (iii) telodiagenesis, which occurs during uplift, erosion and incursion of meteoric waters.

14

Aims of the study

The aims of this thesis are to: (i) unravel the impact of diagenetic al-terations on the spatial and temporal distribution of reservoir quality and heterogeneity of shallow marine, deltaic, and fluvio-lcustrine de-posits, (ii) link the distribution of diagenetic alterations to the se-quence stratigraphic framework, and (iii) elucidate parameters control-ling the diagenetic evolution of siliciclastic and hybrid arenites. Four siliciclastic successions representing different depositional facies have been studied for the purpose of this work (Fig. 5), including: (i) Middle to Upper Miocene Abu Alaqa group of aggradational and progradational fan-delta deposits from Gulf of Suez, Egypt, (ii) Middle to Upper Devonian The Ponta Grossa Formation, Paraná Basin, from Brazil (shoreface sand-stones), (iii) Lower Eocene Roda sandstone Formation (delta complex) from South-Pyrenean Foreland Basin, NE Spain, and (iv) Jurassic and Triassic Yanchange and Yan`an Formations (fluvio-lacustrine sand-stones), Yanchang oil field, Ordos Basin, China. Diagenetic studies were conducted on sandstones samples collected from cemented and poorly lithified sandstones within systems tracts and, when possible, along key sequence stratigraphic surfaces in these four successions.

15

Figure 5: Location map of the studied cases.

16

Sequence Stratigraphy of Paralic, Shallow Marine and Fluvio-lacustrine Deposits

Sequence stratigraphy is an informal chronostratigraphic methodology that uses a hierarchy of stratal surfaces to subdivide the stratigraphic record. This methodology allows the identification of coeval facies and documents the time-transgressive nature of lithostratigraphic units. The key concept in sequence stratigraphy is that sedimentary suc-cessions are composed of two chief ingredients: sediment (preserved as rock) and hiatus (preserved as discontinuities or stratal surfaces). This notion is directly related to Walther`s Law, which states that ge-netically related facies (i.e. facies which occur in laterally adjacent environments) will occur conformably in vertical successions. Where a vertical succession contains transition between facies, which are not genetically related (e.g. from upper shoreface sandstone to offshore mudstone), Walter’s Law dictates that the transition must represent a depositional discontinuity (i.e. a period of erosion or no deposition). Recognition and correlation of these surfaces is the basis of sequence stratigraphy. The controls on sequence development are fairly simple: sediment accumulates at a given point where there is space (accommodation) and provided that sediment is available (e.g. Vail et al. 1977, Jervey, 1988, Posamentier et al.1988, Galloway 1989). The internal organiza-tion of sequences is also influenced by spatial variations in subsi-dence/uplift and the basin margin physiography, such as presence or absence of a shelf break (sensu Van Wagoner et al. 1990). All poten-tial controls on sequence development, such as tectonic subsi-dence/uplift and climate, act directly or indirectly to change one or more of these factors (Fig. 6). The sequence stratigraphy tool is used to correlate genetically re-lated sedimentary successions bounded at top and base by unconfor-mities or their stratal patterns are interpreted to form in response to the interaction of eustatic change of sea level, compaction, sediment sup-ply and tectonic subsidence (Van Wagoner et al., 1990). Sequence

17

stratigraphic units are recognized on a number of temporal scales from parasequences, which may represent tens of thousands of years, to sequences, which record timescales ranging from tens of thousands to millions years or more.

Figure 6: Sediment accommodation space and its relationship to eustatic sea-level and tectonic uplift and subsidence. Marine accommodation space created during a rise in relative sea-level has been partially filled with sediment (yellow and dark-grey), whereas the non-marine accommodation space created during the rise in relative sea level has been totally filled with sediment (yellowish-green). Modi-fied after Angela Coe et al. (2003).

Parasequences and marine flooding surfaces A parasequence is a relatively conformable succession of genetically related beds bounded by marine flooding surfaces (Van Wagoner et al. 1988). Parasequences in siliciclastic systems are usually prograda-tional being deposited when rates of sediment flux exceeds accommo-dation creation. Marine flooding surface, which bounds the top of the parasequences, forms as rate sediment flux is outpaced by the addition of accommodation. The deepening referred to in the Van Wagoner (1988) definition is recorded by a landwards facies shift, i.e. from a proximal to a lower energy distal depositional environment. The facies shift is usually abrupt, but the flooding event may be represented by a thin retrogradational interval at the top of the parasequence (Arnott 1996, 2007). Rapid and gradual landwards facies shifts are usually accompanied by a reduction in grain size, changes in sorting, sedimen-tary structures, degree and type of bioturbation and bioclast concentra-

18

tions (e.g. Kidwell 1989, Krawinkel and Seyfried 1996). The identifi-cation of a flooding surface in prodelta or on the coastal plain is often more difficult than in the shoreface, where there is more facies con-trast (Van Wagoner et al. 1990). Parasequences are often grouped into parasequence sets, which are defined as successions of genetically related parasequences forming a distinctive stacking pattern bounded by major marine flooding sur-faces and their correlative surfaces (Van Wagoner et al. 1988), Parasequences may be arranged/stacked in an overall shallowing up-wards motif referred to as forestepping) or overall deepening upwards (backstepping).

Problems with stacking patterns The stacking pattern within sedimentary packages depends on the rates of accommodation creation versus rate of sediment supply. Pro-gradational, aggradational and retrogradational parasequence sets de-fine the characteristics of systems tracts (e.g. Posamentier et al. 1988). As a result, specific stacking patterns are linked to discrete segments of the relative sea level curve. Recently, it has been demonstrated that due to spatial and temporal variations in sediment flux and accommo-dation development, various facies stacking patterns may develop contemporaneously. Gawthorpe et al. (1997) provided an example of this facies variations based on field studies and computer simulation. In a syn-rift setting, sediment flux varied by an order of magnitude and subsidence rates by a factor of up to five, between fault segments-an along-strike distance of around 10 km. The facies variations re-sulted in the contemporaneous development of progradational, aggra-dational and retrogradational stacking patterns (Fig. 7). The formation of sequence boundaries and onset of forced regres-sion occur at the same time as normal regression or even retrograda-tion. Designating systems tracts in such a scenario is a risky business. However, a rapid rise in relative sea level would generally be recorded in all parts of the basin as a landwards facies shift, since sediment flux is likely to occur at slower rates. For this reason, major marine flood-ing surfaces provide a robust framework for correlation and facies prediction.

19

Figure 7: Depositional architecture as a function of accommodation volume and sediment supply. Modified after Galloway (1989).

Systems tracts Systems tracts are linkage(s) of contemporaneous depositional sys-tems (Brown and Fisher, 1977), and are the primary constituents of sequences. Systems tracts have characteristic stratal geometries, stack-ing patterns, their positions relative to each other and within the se-quence and their bounding surfaces.

20

Difficulties encountered in recognizing sequence boundaries and correlative surfaces have led to the appearance of new schemes, de-veloped from the poor genetic sequence stratigraphic model. There exist at least two such schemes genetic stratigraphy (Galloway, 1989), and allostratigraphy. Systems tracts are recognized and defined by the nature of their boundaries and by their internal geometry (Emery and Myers, 1996). Three main systems tracts can be usually distinguished as a result of one relative sea-level cycle (Posamentier et al. 1988). (1) Lowstand systems tract (LST), which is formed by forced (i.e., fall in eustatic sea level) rather than normal regression (Posamentier et al., 1992), is comprised of: (i) deep water turbidite systems, which are represented by basin-floor and slope fans, and (ii) lowstand wedge comprised of fluvial deposits within incised valleys and shelf edge deltas, which have aggradational and/or progradational parasequence sets (Fig. 7). The LST is deposited between the lower sequence boundary (abrupt relative sea level fall) and the beginning of relative sea level rise, which is represented on the shelf by the first marine transgression and formation of transgressive surface, possibly repre-sented by a ravinement surface, which is a conglomeratic lag formed by wave and current reworking shelf sediments (Fig. 8). (2) Transgressive systems tract (TST), which is deposited during a rapid rise in the relative sea level, and is bounded below by the trans-gressive surface and above by the maximum flooding surface (MFS). (3) Highstand systems tract (HST), which is deposited during stable high and slowly falling relative sea level, is bounded below by MFS and above by the upper sequence boundary. The HST is comprised of initial aggradational and later, as the accommodation created by rise in the relative sea level diminishes, progradational parasequence sets (Fig. 7). Commonly, the HST is partly preserved owing to erosion during the next cycle of fall in relative sea level, and formation of up-per sequence boundary.

21

Figure 8: The four system tracts including lowstand (LST), transgressive (TST), highstand (HST), and forced regressive system tracts (FRST).

Two other system tracts which are not included in the original Exxon scheme: (1) Forced regression systems tract (FRST), which has been proposed (Plint, 1988; and Hunt and Tucker, 1992; 1995) to be deposited during relative sea-level fall, when incision and bypass occur on the alluvial- and coastal plain, whereas deposition occurs on the submerged parts of the shelf. FRST includes erosion based (detached), as well as gradually based (attached) deposits. The FRST is bounded below ei-ther by a marine ravinement surface of erosion formed during regres-sion or by a conformable surface. Above, the FRST is bounded at top

22

by a SB and/or a Transgressive surface. Therefore, LST is restricted to the interval of lowest point of relative sea-level position to the begin-ning of the transgression. (2) Regressive system tract (RST), which formed between two rapid rises in relative sea-level separated by a slow rise. The RST is bounded below by a maximum flooding surface, and consists of pro-grading wedge. Other key sequence stratigraphy surfaces, which enable us to tie sedimentary successions into packages with genetic and chronostrati-graphic significance, applied in this paper include: (1) marine flooding surfaces (FS), which are surfaces that separate younger from older strata, and across which there is evidence of an abrupt increase in ei-ther marine; (2) transgressive surface (TS) is the marine flooding sur-face marking the lower boundary of the TST deposits; (3) maximum flooding surface (MFS), which is indicated by condensed section due to sediment starvation, represents the point of maximum landward advance of the strandline.

23

Methodology

Facies description was preformed for the purpose of construction of depositional facies and sequence stratigraphic framework. Whenever possible, samples were collected from both outcrops and subsurface cores along, above and below key sequence stratigraphic surfaces in-cluding, amalgamated transgressive surface/sequence boundary, maximum flooding surface and parasequence boundary and within the highstand and transgressive systems tracts (sensu van Wagoner et al., 1990). Thin sections were prepared for all samples subsequent to vac-uum impregnation with blue epoxy. Modal analyses of the arenites were preformed by counting 300 points in each thin section. Scanning electron microscope (SEM) was used to study crystal habits and par-agenetic relationships among diagenetic minerals in representative samples. The chemical composition of minerals was determined in thin sections coated with a thin layer of carbon using a Cameca BX50 mi-croprobe equipped with three spectrometers and a back scattered elec-tron detector (BSE).was used to determine the chemical compositions and paragenetic relationships of different cement types. The opera-tions conditions were: 20 KV acceleration voltage, 5 nA (for carbon-ates) to 15-nA (for feldspars) measured beam current, and 10 �m beam diameter. The standard and count times used were wollastonite (Ca, 10 s), MgO (Mg, 10 s), strontianite (Sr, 10 s), MnTiO3 (Mn, 10 s), and hematite (Fe, 10 s). Analytical precision was better than 0.1% for all elements. Conventional petrographic examination was com-plemented by Cathodoluminescence (CL) petrography to study zona-tion in various carbonate cements (paper IV and V). The operating conditions were 12–16 kV accelerating voltage, 300-350 μA beam current and 0.2–0.1 Torr vacuum pressure. Stable carbon and oxygen isotope analyses were carried out on carbonate-cemented arenites representative of the various depositional environments and systems tracts in order to determine the geochemi-cal conditions, pore waters composition and temperature of precipita-tion. For the purpose of oxygen and carbon isotope data, bulk samples were powdered (< 200 mesh) and reacted with 100% phosphoric acid

24

at 25ºC for one hour for calcite, at 50ºC for 24 hours for Fe-dolomite/ankerite and siderite-cemented samples were reacted at 50ºC for 96 hours (e.g. Al-Aasm et al., 1990). The evolved CO2 gas was analysed for carbon and oxygen isotopes in a SIRA-12 mass spec-trometer. The phosphoric acid fractionation factors used were 1.01025 for calcite (Friedman and O`Neil, 1977), 1.01060 for Fe-dolomite/ankerite and 1.010454 for siderite (Rosenbaum and Sheppard, 1986). The isotopic data are presented in the normal � nota-tion relative to V-PDB. The ratio of 87Sr/86Sr isotopes were analysed for siderite, calcite, and Fe-dolomite/ankerite-cemented samples using the methods of Schulz et al. (1989). The 87Sr/86Sr isotope ratios were analyzed using an automated Finnigan 261 mass spectrometer equipped with 9 fara-day collectors. Some of calcite-cemented samples from different sys-tems tracts were washed with distilled water and then reacted with dilute acetic acid in order to avoid silicate leaching. Correction for isotope fractionation during the analyses was made by normalization to 86Sr /88Sr = 0.1194. The mean standard error of mass spectrometer performance was ±0.00003 for standard NBS-987. Orientated, < 2 �m clay fractions were separated from nine sam-ples subsequent to gentle crushing and subjected to X-ray diffraction (XRD) analysis using SIEMENS–D5000 equipment. The samples were analysed subsequent to air drying, saturation with ethylene gly-col, and heating to 550°C for 6 hours. Total organic carbon (TOC) was measured in Brazil paper to aid the sequence stratigraphic analy-ses. Mudstone samples with a regular spacing of 30 cm were collected from all wells for the purpose of TOC analyses. Silty sandstone inter-vals were sampled with a spacing of 50-100 cm. All samples were pulverized an agate mortar, heated to 1350°C and flushed with O2, and analysed in LECO SC-444 equipment. Relative weight of organic car-bon is measured from CO2 and SO2 counts in an infrared detector. Inorganic carbon content was carefully removed from samples by re-petitive addition of 0.5N HCl (under warming). Spectral gamma-ray (uranium, potassium and thorium) measurements were carried out on the same samples for which TOC analyses were performed. A stan-dard duration of two minutes was selected for each measurement. Mössbauer spectroscopy is a useful tool for studying the distribu-tion of Fe-bearing minerals and their oxidation state in sediments and sedimentary rocks to elucidate the diagenetic conditions (Suttill et al., 1982; Görlich et al., 1989; Hornibrook and Longstaffe 1996: Robin-son, 2000). Mössbauer spectroscopy was used (paper III) to investi-gate horizons containing abundant Fe-rich minerals in siliciclastic.

25

The total porosity and permeability of selected sandstones from the transgressive and highstand systems tracts (paper II) were calculated using image analysis software. The calculation of permeability using this software was based obtaining the pore perimeter (pp), porosity (�) and pore area (PA) and then using the equation of Kozeny-Carman, which was modified by Mowers and Budd (1996), as fol-lows: K = �3/c(1- �)(4pp/�PA)2. The constant c was assumed to be 5, which is a typical value for sandstones (Mowers and Budd, 1996). The helium porosity and air permeability were measured for core plugs at a confining pressure of 100 and 400 psi, respectively (paper V). Prior to measurements, the plugs were examined carefully for hair-thin microfractures and cleaned in an oil extractor and dried in a vacuum oven at 60°C for 24 hours.

26

Important eogenetic alterations linked to sequence stratigraphy

The main eogenetic alterations in the paralic, shallow marine and fluvio-lacustrine deposits are carbonates (e.g. calcite, dolomite, and siderite), kaolinite, Pseudomatrix, grain-coating and ooidal berth-ierine, ooidal goethite, mechanically infiltrated clay, glauconite, and pyrite. Calcite cement occurs commonly as coarse to poikilotopic spar in progradational braid-delta fan sequences, particularly along the topsets (marine flooding surfaces) (paper I), HST and TST (paper II), along deltaic parasequence boundaries of the early HST (paper V). Microcrystalline and equigranular mosaic calcite are more abun-dant in the aggradational than progradational arenites, particularly below the marine erosional surfaces (i.e. sequence boundaries). Cal-cite cement occurs as syntaxial calcite overgrowths around crinoid fragments in some of the arenites from the progradational and aggra-dational sequences (paper I), Vadose calcite cement was formed in the fluvial, floodplain sediments as evidenced by the presence of rhizocretionary calcite intraclast in the channel lag deposits. The cal-cite intraclasts were derived by erosion of floodplain sediments dur-ing channel migration. calcite occurred in sandstones closely associated with organic-rich lacustrine and pro-deltaic mudstones at parasequence boundaries of the early HST(paper V). Continuously cemented beds occur in the upper parts of the (TST), particularly along the (PB) and the (MFS). Conversely, incomplete carbonate cementation (i.e. non- concretions) occurs in sandstone beds of the (RST) (paper IV).

Dolomite occurs as syntaxial overgrowth and as discrete, rhombic crystals in arenites of the progradational fan delta sequences. Zoned dolomite and detrital, partly dissolved dolomite, is more commonly encountered in the progradational than aggradational sequences (paper I) Coarse-crystalline dolomite being a more common encountered feature in arenites from the aggradational than in the progradational sequences. Microcrystalline dolomite (5-10 μm) occurs as pore-filling aggregates and as grain coatings, particularly in the aggradational lags of (MFS) (paper I)

Siderite occurs as small crystals arranged along traces of mica cleavage planes, mainly in the fine-grained deltaic sandstones (paper

27

V) which are rich in mica and pseudomatrix. Siderite occurs also as flattened rhombs. EMP analysis revealed that siderite is chemically zoned, with less magnesian cores (MgCO3 = 1.3-3.7%; av. 2.3%) than rims (MgCO3 = 17.7 %). Siderite occurred in siltstones and very fine-grained sandstones that are closely associated with organic-rich lacustrine and pro-deltaic mud-stones at parasequence boundaries of the early HST (paper V). Siderite most common in the TST deposits (paper II) occurs as scattered ooid-like spher-ules as discrete distorted rhombs, as aggregate of tiny, rise-like crystals that fill the pore space locally or occurs within strongly expanded mica grains. Euhedral siderite crystals in the silty and sandy mudrocks (paper II) occur as scattered patches (ca 30 �m across) with hollow center. the �18O V-PDB values of siderite (-11.8‰ to -5.8‰) indicate temperatures of ca 30-65ºC BSE im-aging revealed that siderite crystals are zoned mainly in terms of variations in the Mg contents. The siderite spherules display alternating zones of Mg-rich and Mg-poor siderite. Although inconsistently, the outer zones of side-rite rhombs in both the TST and HST sandstones, are more enriched in Mg than the cores. The �18O values of the siderite cements do not display sys-tematic variation with respect to systems tracts and key sequence strati-graphic surfaces.

Kaolinite is greater extent of dissolution and kaolinitization of detrital feldspar, mica and mud intraclasts in the HST than in the TST sandstones (paper II) is attributed to the incursion of under-saturated meteoric waters during fall in the relative sea level under humid climatic conditions in the Jurassic fluvial sandstones (paper V). Kaolinite is most common in poorly-lithified sandstones of RST and TST (paper IV), which occurs as scatter patches composed of booklets and vermicular crystals that have replaced partly to completely muscovite, K-feldspar and mud intraclasts.

Pseudomatrix (i.e. matrix formed by pseudoplastic deformation and squeezing of mud intraclasts between the rigid feldspar and quartz grains), occur in the LST and HST sandstone (paper II), fluvial channel TST (paper V).

Berthierine occurs as thin coatings around detrital grains, ooids, and grain replacive. The grain-coating berthierine/chlorite occurs as continuous or discontinuous, single or multiple layers that are thin (5 to 15 �m) or absent at grain-to-grain contacts. The berthierine coatings are composed of boxwork-like, tiny crystals (about 1-2 �m across) being, in some cases, covered by coarser-crystalline patches that resemble rosette-like, Fe-rich chlorite (ca 5 �m in size), which may extend to fill the adjacent pores. The grain-coating berthierine/chlorite varies in abundance from scarce, being coating a small fraction of the grains in (HST), to widespread, and being coating major por-tions to most grains (TST) (paper II). Berthierine ooids occur as beds show-ing cross bedding or are scattered in mudrocks of (TST), particularly along TS and MFS (paper II). The ooids are overall ovoidal in shape and range in size from ca 250 �m to 1 mm, being lacking nucleus or have a nucleus com-

28

posed of silt- or sand-sized, framework silicate grains surrounded by a cortex of relatively poorly-distinguishable, 5–10 �m thick laminae of cryptocrystal-line berthierine. Ooids in some of the sandy siltstones and mudstones, which are extensively cemented by microcrystalline siderite, are arranged concen-trically presumably owing to circular bioturbation.

Goethite occurs as cement and as ooids being most common and most abundant in the TST sediments particularly below MFS (paper II). Pore-filling goethite occurs as scattered patches (400-800 �m across) and as small circular shaped, patches with hollow center or as local, extensive cement patches. Goethite ooids occur as concentric laminae (ca 5-15 �m thick) around silt and sand-sized goethite grains. Goethite was identified by XRD analyses, and the EMP analyses revealed that goethite contains small amounts of Al (Al2O3 = < 1.1 wt.%). Goethite ooids and cement were pre-sumably formed at or immediately below the seafloor from oxygenated pore waters, which implies that the bottom waters were oxygenated too (Claypool and Kaplan, 1974; Irwin et al., 1977; Curtis et al., 1986; Curtis, 1987; Postma, 1993). Dissolved iron needed for the formation of diagenetic goe-thite was presumably derived by diffusion of dissolved iron from the suboxic and anoxic geochemical zones that underlie the oxic zone below the seafloor (Gehring, 1989), in a manner similar to the formation of Fe-Mn nodules on the modern abyssal seafloor. In some cases, the texture of diagenetic goe-thite, such as the tiny, circular forms, may suggest the role of bacteria in their precipitation (Ghiorse, 1984; Konhauser, 1998). Mechanically infiltrated clay occur nearly exclusively in the HST sandstones (paper II), display textural properties indicative of an origin as infiltrated clays, such as the tangential arrangement of these clay flakes and their presence along grain-to-grain contacts (Morad and De Ros, 1994; Mo-rad et al 2000). Clay infiltration occurs in subaerially exposed sand as a con-sequence of percolation of surface waters that are rich in suspended mud. Subaerial exposure of shallow marine sand is anticipated to occur during fall in the RSL and concomitant progradation of the HST shoreface sand (Ketzer et al., 2003b). The original composition of the infiltrated and inherited clays is unknown, but is commonly presumed to be dominantly smectitic in com-position (De Ros et al, 1994). Glaucony is a widespread greenish mineral in marine environments. It occurs as grains or pellets, which are spheroidal, irregular, or lobate in shape (Triplehorn, 1966; Jeans et al., 1982). Glaucony peloids, which are yellow-ish brown to deep green in color and lack internal cracks are more common in the aggradational (i.e. sequence boundaries) than progradational se-quences, being most abundant along the marine regressive surfaces (i.e. se-quence boundaries) (paper I). Glaucony (light- to dark-green in color) occurs in trace amounts (< 1%) as sand-sized, flake-like grains and, less commonly, as pelloids (paper II). The flake-like glauconite grains have similar size, shape and distribution pattern as the associated mica grains and commonly

29

enclose remnants of biotite. Most glauconite was formed by the replacement of biotite grains, which is evidenced by the similar shape and size of glauco-nite to those of biotite as well as by the presence of biotite remnants within the glauconite grains (Ketzer et al., 2003b). Pyrite occurs mainly (up to ca 2%) in the carbonate-cemented sandstones and in mudstones in the TST and MFS. (paper II). Pyrite occurs in the shore-face (paper II) as: (i) framboids (ca 10-20 �m cross) and local pore-filling aggregates of discrete (5-10 �m across), euhedral crystals, and (ii) scattered, small (ca 10-30 �m in size) euhedral crystals within mica grains that have been pervasively replaced by berthierine and/or siderite. Pyrite occurs as framboids in trace amounts (trace to 1%; 0.2%) that are scattered within calcite and dolomite cements (paper I) and within chambers of foraminifera. pyrite is more common in progradational braid-delta fan sequences, particu-larly along the topsets MFS (paper I). Pyrite is more common in the TST than in the RST sediments (paper IV). Pyrite in the RST and LST sediments is often partly oxidized (Paper IV).

30

Important mesogenetic alterations linked to sequence stratigraphy

The main mesogenetic alterations in the paralic, shallow marine and fluvio-lacustrine deposits are Fe-dolomite/ankerite, illite, quartz overgrowths, al-bite, dickite, and chlorite. Pore-filling and grain-replacing Fe-dolomite and, less abundant, ankerite occur as coarse, rhombic to poikilotopic crystals. These carbonates occur in variable amounts (nil to 15%) being slightly more abundant in the HST than in the TST shoreface sandstones (paper II). There are no systematic varia-tions in the chemical and isotopic compositions of Fe-dolomite/ankerite in the TST and HST sandstones (paper II). The �18O V-PDB values of bulk Fe-dolomite/ankerite (-10.8‰ to -9.6‰) suggest precipitation at narrow tem-perature range (55-70ºC) (paper II). The slightly to considerably higher 87Sr/86Sr ratios of the Fe-dolomite/ankerite cements in the TST and HST sandstones (0.708910 to 0.709640) than that of ambient seawater (0.7078-0.7083; Veizer et al., 1999) is attributed to derivation from 87Sr/86Sr from the mesogenetic dissolution and alteration of K-feldspar and mica, which are known to be enriched in radiogenic strontium (paper II). Ankerite occurs as blocky saddle crystals (100-350 μm) that fill the intergranular pores and replace detrital feldspars and pseudomatrix. Ankerite also occurs within ex-panded biotite grains Paper V). Ankerite is more abundant in the fluvio-deltaic, Triassic sandstones than in the fluvial Jurassic sandstones (paper V). Fe and Mg needed for ankerite cementation were possibly derived internally from dissolution of volcanic fragments, biotite and grain coating smectitic clays and iron-oxide pigment, and externally by diffusive transfer from adja-cent mudrocks (Boles and Franks, 1979). The oxygen isotopic values of ankerite are extremely low (av. �18O V-PDB = -15‰ and -19‰, respectively), which indicate either precipitation from highly 18O-depleted waters of mete-oric origin or at elevated temperatures. The temperature for ankerite precipi-tation (98-127oC) such temperatures agree well with the maximum tempera-tures reached during mesodiagenesis (105-124oC) (paper V). The emplace-ment of oil has retarded the precipitation of ankerite, which is more abundant in the water-saturated reservoirs (paper V).

31

Illite occurs in various textural habits (mat-like, fibrous or lath-like crystals that form rims around framework grains, platelet-like, fila-mentous, booklets-like and honeycomb-like) mainly in the HST shore-face sandstone (paper II), RST than in the TST sandstones (paper IV),and in all facies of Jurassic and Triassic fluvio-lacustrine sandstones during rapid subsidence to depths of 3700-4400 m (paper V). Illite formed by various processes including transformation of a clay precursor, pre-cipitation from porewaters (authigenesis), replacement kaolinite and feldspar (e.g. Worden and Morad, 2003). Grain-coating illite that var-ies widely in thickness (paper II) and occurs within embayed surfaces of sand grains are interpreted to be originally inherited clay coatings (Pittman et al., 1992). The original composition of the infiltrated and inherited clays is unknown, but is commonly presumed to be domi-nantly smectitic in composition (De Ros et al, 1994).The chemical composition and XRD properties of illite (paper II) suggest that the Devonian sandstone were subjected to fairly deep burial diagenesis. Illite in the water zone (paper V) occurs; however, as better developed than in the oil-saturated zone, filaments up to 40 μm long that are ar-ranged perpendicular to the grain surface. The formation of consider-able amounts of filamentous, permeability-deteriorating illite was re-tarded because of: (i) the replacement of eogenetic kaolinite by the more stable dickite, and (ii) the resistance of detrital K-feldspars to-wards albitization due to the low maximum temperatures reached (105-124°C), and to the short residence time at these temperatures. Conversely, these burial-temperature conditions were sufficient to cause pervasive albitization of the moderately calcic plagioclase grains.

Quartz overgrowths are more abundant in the HST sandstones ow-ing to the less abundant and less extensive grain-coating berth-ierine/chlorite than in the TST sandstones (paper II). Silica needed for the formation of quartz overgrowths was presumably derived inter-nally from the intergranular dissolution of quartz grains in the sand-stones (Walderhaug, 1994; Walderhaug and Bjørkum, 2003). Chemi-cal compaction of the Devonian sandstones is manifested by inter-granular pressure dissolution of quartz grains, sutured and straight in-tergranular contacts which was frequently enhanced by the presence of grain-coating illitic clay and muscovite grains (Oelkers et al., 1996). Pressure dissolution has obviously acted as an internal source of silica needed for the formation of quartz overgrowths (Worden and Morad, 2000). Quartz cement (trace to 7%; av. 2% paper V), which occurred during rapid subsidence to depths of 3700-4400 m occurs as syntaxial overgrowths on detrital quartz and as prismatic outgrowths when the quartz grains are coated with thick clay layers. The outgrowths are comprised of a single crystal or a number of blocky crystals that com-

32

pletely fill adjacent pore space. Trace amounts of quartz cement occur as microcrystals that are closely associated with diagenetic illitic clays. Quartz overgrowths are most abundant in sandstones which are poor in carbonate cement and in grain-riming, illite or chlorite (paper V). Quartz is also more abundant in the water-saturated than in the oil-saturated sandstones. Oil emplacement retarded cementation by quartz and carbonate but had little influence on dickite, illite and chlorite formation (paper V). Retardation of quartz cementation was also due to the presence of chlorite fringes around detrital quartz grains. The albitized grains are composed of numerous euhedral crystals (2-10 μm) arranged parallel to each other and to traces of twinning and cleavage planes of the detrital feldspars. Albite occurs in both the HST and TST sandstones (paper II). Albitization of plagioclase (paper II and V) has been inferred to commence during mesodiagenesis at tem-peratures greater than about 70ºC (e.g. Saigal et al., 1988; Morad et al., 1990) and becomes more extensive with further increase in tempera-ture (Boles, 1982). The Ca and Al released from the albitization of plagioclase have presumably been used in the formation of carbonate cement and clay minerals, respectively (e.g. Boles, 1982; Morad et al., 1990). The small extent of K-feldspar albitization is probably due to the formation of small amounts of illite, which is the typical sink of released K+ , and hence the driving kinetic factor of the reaction (Mo-rad et al., 1990). Some of the albitized plagioclase contains a thin layer of euhedral albite overgrowths (paper V). There is no variation in the amounts of albitized plagioclase grains between the water-saturated and oil-saturated sandstones, but albitized K-feldspar grains occur al-most exclusively in the water-saturated sandstones (paper V). Dickite occurs mainly in the HST sandstones (paper II). The con-version of thin crystals of kaolinite into thicker, blocky dickite, which is a dissolution-reprecipitation process (MackAuloy et al, 1994) occur-ring during mesodiagenesis (Ehrenberg et al., 1993; Morad et al., 1994; Lanson et al., 2002), is common in the HST sandstones Thus, this conversion process in the Devonian shoreface sandstones suggests that eogenetic kaolinite was destabilized during burial and increase in temperature. The conversion is suggested to be aided by incursion of acidic fluids (MacAuly et al, 1994; Morad et al, 1994). In the fluvial Jurassic sandstones (paper V); kaolinite is etched and replaced by blocky dickite. Replacement of kaolinite by dickite is more extensive in the coarser-grained, permeable sandstones than in fine-grained, less permeable sandstones. Intercrystalline microporosity is more abundant in the dickite (up to 70%) than in poorly- or well-crystallized kaolinite patches (paper V).

Chlorite occurs as a grain coating which composed of box-work-like with the chlorite crystals attached perpendicular to the grain

33

surface, platelet-like, rosettes, and honeycombs textures in the TST and HST (paper II). The grain-coating berthierine/chlorite varies in abun-dance from scarce, being coating a small fraction of the grains (in HST sandstones), to widespread, being coating major portions to most grains (in TST sandstones) (paper II). Chlorite that covers layers of grain coating and ooidal berthierine has presumably been formed by direct precipi-tation from the pore waters and not by chloritization of berthierine (paper II). The grain-coating berthierine and chlorite have halted the precipitation of quartz overgrowths (paper II). Mössbauer spectroscopy (paper III) re-vealed that iron is dominated by Fe2+ (>85%). Fe2+ replaces Mg2+ whereas Fe3+ replaces Al3+ in the octahedral sites. Fe-rich chlorite occurs as partial to extensive grain rims that are comprised of pseudo-hexagonal crystals arranged perpendicular to the surfaces of frame-work grains (paper V). Chlorite fringes are more abundant in the del-taic channel and delta front facies (trace to 16%; av. 3%) than in the fluvial sandstones (trace to 3%; av. 1% paper V). Chlorite fringes were formed by successive replacement of smooth layers of precursor, grain-coating smectitic clays (paper V) through intermediate phases of mixed-layer chlorite/smectite (C/S) that, in some cases, have the typi-cal honeycomb texture of corrensite. Chloritization of smectite oc-curred most extensively in the deltaic sandstones (paper V) that were enriched in biotite and volcanic rock fragments, which acted as sources of Fe and Mg. Additional sources of Fe and Mg include fine crystalline, grain coating iron-oxide pigment.

34

Reservoir quality evolution and conceptual predictive models within depositional facies and sequence stratigraphy

Linking the distribution of diagenetic alterations with the depositional facies and in a sequence stratigraphic framework, i.e., at sequence and parasequence boundaries, transgressive and maximum flooding sur-faces, and within systems tracts of paralic, shallow marine, and fluvio-lacustrine deposits which is based on the results from this thesis is of profound importance in deciphering the spatial and temporal distribu-tion of diagenetic alterations and of their impact on reservoir quality evolution. Prediction of reservoir quality in paralic and shallow ma-rine deposits is usually complicated by the generally greater influence of diagenetic modifications on porosity than on permeability. The depositional environments and facies in paralic and shallow marine exert considerable controls on the diagenetic evolution of clas-tic sequences. These controls are mostly take place during eodiagene-sis being related to variations in pore water chemistry, degree of bio-turbation, organic-matter contents, as well as to the textural and archi-tecture of the sedimentary sequence. The sediment refers mainly to the thickness, spatial and temporal inter-relationships (i.e., geometry of sediment bodies) and ratio sand and mud, which in turn controls the extent and pattern of fluid flow. Variations in sedimentation rate con-trol sediment reworking by bioturbation and the residence time of sediments at the sediment-water or sediment-air interface. The latter exert profound control on the amounts of organic matter and extent of near-surface eogenetic alterations.

35

Model 1: summary model for distribution of diagenetic alterations and reservoir-quality evolution of progradational and aggradational sequencesThe distribution of diagenetic alterations and of their impact on reser-voir-quality evolution of the coarse-grained, deltaic progradational and aggradational sequences (Fig. 9) were controlled by: (i) the car-bonate-grain rich composition of the arenites, (ii) the overall arid, pa-leo-climatic conditions, (iii) the shallow estimated maximum burial depth (ca 1 km) reached by the successions, and (iv) variations in the rates of changes in relative sea level versus rates of sediment supply, which had an impact on changes in pore water chemistry. The carbon-ate grains have played a dual role in reservoir-quality evolution. These grains were subjected to dissolution and formation of moldic pores, which had limited impact on permeability enhancement owing to the poorly connected nature of these pores. Dissolution of the carbonate grains is expected to have contributed to porosity deterioration through re-precipitation as carbonate cement. Moreover, these grains have acted as nuclei for the precipitation of carbonate cement, which hence induced further deterioration to reservoir quality. The arid cli-matic conditions resulted had resulted in the formation of gyp-sum/anhydrite, which was in some cases been replaced by calcite dur-ing near-surfaces diagenesis. The sulfate released from this replace-ment reaction was reduced into sulfide, as evidenced by the presence of framboidal pyrite in the vicinity of calcitized gypsum. The formation of trace amounts of syntaxial quartz and K-feldspar overgrowths around quartz and K-feldspar grains, respec-tively, have had little or no impact on reservoir quality evolution of the arenites. The origin of trace amounts of euhedral quartz over-growths, which are engulfed by, and hence pre-date, early diagenetic dolomite in both the progradational and aggradational sequences is enigmatic. The only viable way to form near-surface quartz over-growths is through the process of silcrete formation, which typically occurs under arid to semi-arid climatic conditions (Abdel-Wahab et al., 1998). However, the absence of opal and chalcedony suggests that the quartz overgrowths do not likely represent part of silcrete devel-opment. The formation of burial diagenetic quartz overgrowths re-quires depths > ca 2 km and temperatures > 70ºC (cf. McBride, 1989; Worden and Morad, 2000), which have not been reached by the stud-ies sequences. However, the relatively small amounts of quartz grains in most of the studied arenites coupled with the common presence of

36

Figure 9: Simplified cartoons showing the most typical diagenetic features in the aggradational and progradational fan delta sequences.

abundant early diagenetic carbonate cements, may have been another limiting factor for the formation of greater amounts of quartz over-growths. The sources of K, Al and Si ions needed for the formation of early diagenetic K-feldspar overgrowths are not immediately clear. K+ could have been derived from seawater, whereas K+, Al3+ and Si4+ could be derived from partial dissolution of mica and K-feldspar grains (cf. De Ros, 1998). Palygorskite, which covers, and hence post-dates, dolomite ce-ment in the arenites is suggested to be of telogenetic origin. The close association between palygorskite and dolomite suggest that dolomite

37

provided a localized source of Mg needed for the formation of paly-gorskite, which is enhanced by the arid climatic conditions in the Sinai Peninsula.

Model 2: summary model of the diagenetic evolution of shoreface sandstone (paper II) Sandstones of the various systems tracts and below key sequence stratigraphic surfaces have fairly characteristic, yet variable diagenetic evolution pathways (Fig. 10), which is underlining the profound im-pact of the rates of changes in the relative sea level and rates of sedi-ment supply of the distribution of eogenetic and, consequently, mesogenetic alterations (cf. Taylor et al., 1995; Amorosi, 1995; Mo-rad et al., 2000; Ketzer et al., 2002, 2003a). Eogenetic alterations in the TST sediments, particularly below the TS and MFS, which are accomplished under low sedimentation rates, include the formation of: (i) goethite ooids and cement under oxic conditions at and immedi-ately below the seafloor, (ii) grain-coating, grain-replacing and ooidal berthierine, siderite spheroids, from sub-oxic pore waters, (iii) glauco-nite, primarily by the replacement of mica grains under weakly reduc-ing conditions (Curtis, 1987), presumably in the suboxic, nitrate re-duction zone of Froelich et al. (1979), and (iv) pyrite in the bacterial-sulfate reduction, yet small amounts of siderite that engulf pyrite may have been formed in the methanogenesis zone. Eogenetic alterations in the HST sandstones, which were accom-plished during fall in the relative sea level (i.e. progradation), include the notable formation of: (i) limited amounts of discontinuous, grain-coating berthierine, presumably owing to the short residence time of the sediment to form the precursor Fe-rich clay minerals, such as odi-nite, and (ii) dissolution and kaolinitization of feldspars and, to smaller extent, mica, which is attributed to the flux of under-saturated meteoric waters during fall in the relative sea level. Eogenetic kaolin-ite is engulfed by siderite, Fe-dolomite and quartz overgrowths. Cal-cite, Fe-dolomite/ankerite and siderite cementation has occurred at various temperatures in the TST and HST sandstones. Mesogenetic alterations in the HST sandstones are similar to those in the TST sandstones, except for the extensive and widespread conver-sion of kaolinite into dickite and formation of considerable amounts of quartz overgrowths in the former sandstones. Silica needed for the formation of quartz overgrowths was presumably derived internally

38

Figure 10: Simplified cartoons showing the most typical diagenetic features in sandstones from the highstand systems tracts (HST), transgressive systems tracts (TST), and along the amalgamated transgressive surface/sequence boundary (TS/SB) and the maximum flooding surfaces (MFS). The HST sandstones are, over-all, characterized by larger amounts of kaolin, illitic clays and syntaxial quartz over-growths than the other sandstones. The latter sandstones are characterized by larger amounts of berthierine and siderite. Glauconite, which is mostly restricted to the MFS, was formed by the replacement of mica grains.

39

from the intergranular dissolution of quartz grains in the sandstones. Eogenetic grain-coating berthierine, which was subjected to partial chloritization during mesodiagenesis, retarded the precipitation of quartz overgrowths (cf. Ehrenberg, 1993; Bloch et al., 2002). Other mesogenetic alterations include: (i) further cementation of the sand-stones by grain-replacing, poikilotopic calcite, which post-dates me-chanical and chemical compaction as well as by quartz overgrowths, and (ii) albitization of plagioclase grains.Telogenetic alterations in the TST and HST sandstones include the dissolution and kaolinitization of framework silicates, primarily feld-spars. In contrast to eogenetic kaolinite, the telogenetic kaolinite does not display evidence of conversion into dickite. The distinction be-tween intragranular and moldic porosity of telo- and mesogenetic ori-gins is difficult. However, moldic pores partly filled with diagenetic quartz or Fe-dolomite cements are considered to be of mesogenetic origin.

40

Model 3: summary model of impact of diagenetic modifications on reservoir quality of delta complex sandstone sandstones (paper IV) A summary model of the various systems tracts and below key sequence stratigraphic surfaces and related reservoir-quality evo-lution of spatial and temporal variations in the provenance and changes in the relative sea level have had strong impact on the detrital composition and rates of sediment supply, which were, in turn, the main parameters controlling the distribution of diagenetic alterations.

Calcite cement occurs as concretions along the PB of the RST and lower part of the TST, being more and more coalesced into con-tinuously cemented layers towards the MFS, and below the TS (Fig. 11, 12, and 13).

Figure 11: Photograph showing that cement occurs as concretions, which are coa-lesced into continuously cemented layers particularly at PB.

41

Figure 12: Photograph showing that cement occurs as concretions, which are coa-lesced into continuously cemented layers particularly at MFS.

Figure 13: Photograph showing scattered concretions below SB and within the RST.

42

The concretions show no systematic variations in the texture

of calcite cement. Formation of microcrystalline calcite cement at shallow depths below the seafloor is suggested to be sourced by diffu-sion of Mg2+, Ca2+ and HCO3- from the overlying seawater. Cementa-tion was enhanced by the residence time of the sediments near the seafloor. Sandstones display various degree of mechanical compac-tion, which is evidenced by fracturing of bioclasts and bending of the mica grains and low-grade, micaceous metamorphic rock fragments. Evidence of chemical compaction includes intergranular pressure dis-solution of quartz grains and rare stylolites in sandstones that contain small amounts of carbonate cements. Mechanical and chemical com-paction has, in most of the arenites, been more important than cemen-tation in the destruction of intergranular porosity. Secondary porosity is rare in the studied arenites and has resulted mainly from the dissolu-tion of coarse-crystalline calcite. Calcite cement dissolution and pres-sure dissolution of carbonate grains indicate that the diagenetic evolu-tion of the studied arenites has involved considerable cement redistri-bution. Most porosity and permeability in the Roda sandstones are anticipated to be related to tectonic fracturing.

Model 4: summary model of impact of diagenetic modifications on reservoir quality of Jurassic and Triassic fluvial and lacustrine deltaic sandstones (paper V) In addition to the impact of facies, the porosity and permeability of the Triassic and Jurassic reservoirs are controlled to variable extents by: (i) chemical and mechanical compaction, (ii) type, abundance and distribution pattern of the cementing minerals, (iii) the extent of te-logenetic dissolution of framework grains and calcite cement, (iv) the amount as well as the degree of alteration and compaction pattern of micas, particularly biotite, mud intraclast and rock fragments, and (v) oil emplacement. Permeability and, to a smaller extent, porosity in-crease with increase in grain size However, the correlation of porosity and permeability with grain size, and hence depositional facies, is overprinted by the various diagenetic alterations induced to the sand-stones during various stages of burial and uplift. Thus, the wide range of permeability encountered for each porosity value is attributed to variations in grain size as well as in the amounts and distribution pat-

43

tern of interstitial clay minerals (chlorite, kaolin, illite and pseudoma-trix). Clay minerals are rich in micro-pores (Hurst and Nadeau, 1995), and thus induce a smaller lowering of porosity compared to perme-ability. Variations in the amounts of intragranular pores that are poorly connected to the open, intergranular pore system, have induced an increase in porosity but do not enhance permeability of the sand-stones. The overall small amounts of eogenetic cements rendered compac-tion to be more important than cementation in reducing porosity and permeability. Determination of the depositional intergranular porosity is difficult (Bloch and McGowen, 1994), but assuming a value of 40%, the average porosity loss due to compaction is about 22% (4-30%) in the fluvial sandstones and 25% (4-34%) in the deltaic sand-stones. This accounts partly for the lower porosity, and permeability in the deltaic sandstones than in the fluvial sandstones. The slightly greater loss of porosity and permeability due to compaction in the del-taic compared to the fluvial sandstones is partly attributed to the higher content of ductile grains such as mica, argillaceous rock frag-ments and mud intraclast. However, the Triassic sandstones also have an average higher TTI index, and thus a greater diagenetic loss of po-rosity and permeability than the Jurassic sandstones. Overall, sand-stones that contained evenly distributed patches of eogenetic carbon-ate cement suffered relatively little compaction compared to sand-stones that were poor in such cement. The intergranular pressure dissolution (enhanced by mica and illitic clay coatings) and concomitant local precipitation of dissolved silica as quartz overgrowths induced an additional loss of porosity and per-meability. The expansion of abundant biotite grains, particularly in the deltaic sandstones, due to their eogenetic alteration into smectite and/or precipitation of microcrystalline carbonate along traces of its cleavage planes caused efficient choking of adjacent pore throats. Hence, detrital mica induced partial deterioration to both porosity and permeability by alteration and expansion and by the enhancement of intergranular pressure dissolution of quartz grains. The average original porosity loss due to cementation is similar in the fluvial and deltaic sandstone (8%; range 2-26%). However, the precise role of cementation on reservoir quality is fairly complex due to the presence of several types of cements with various textural prop-erties and occurrence habits. Carbonates are the most important ce-ments that caused deterioration of both permeability and porosity and, to a less extent, quartz overgrowths. Eogenetic carbonate cementation,

44

particularly in the Triassic sequence; tend to occurs along parase-quence boundaries in the deltaic facies of the early HST. The forma-tion of laterally cemented layers, and thus potential reservoir barriers in field scale, is possibly favored in the late TST and early HST to-ward the MFS. Mesogenetic carbonates occur as less pervasive ce-ment than the eogenetic type I calcite, but are more frequent, more homogeneously distributed, and hence have a greater influence on porosity-permeability loss in the sandstones. Carbonate cements are more abundant, and, hence, have a greater control on porosity and, particularly permeability of the deltaic sandstones than of the fluvial sandstones. A higher overall content of carbonate cement accounts partly for the considerably lower reservoir quality of the delta-front and pro-delta sandstones compared to the delta-plain sandstones. Chlorite rims around quartz grains retarded the precipitation of quartz overgrowths and hence prevented a greater loss of primary in-tergranular porosity. However, extensive chlorite rims in the fine-grained sandstones caused a local blockage of the pore throats, and by virtue a permeability reduction. The clay minerals induced an increase in microporosity, which is verified by the high values of water satura-tion in the oil zone (av. 26%). In the absence of quartz overgrowths, the intergranular pores that are lined by chlorite were, particularly in some of the water-saturated sandstones, filled partially to extensively by mesogenetic ankerite. The illitization of intergranular kaolinite, and hence further deterioration of permeability, was inhibited due to the earlier transformation of kaolinite into dickite which is more resistant to illitization, due to its better ordered crystal structure (Morad et al., 1994). The retardation of kaolinite illitization was also due to the only small degree of albitization of K-feldspar grains, which usually are the most important sources of potassium ions (Morad et al., 1990). The precise role of telogenetic dissolution of detrital grains and carbonate cement on porosity and permeability is difficult to quantify. The dissolution of feldspar (mainly plagioclase) is, however, more common in the coarse-grained Jurassic fluvial sandstones than in the finer-grained deltaic sandstones. As there is no telogenetic precipita-tion of quartz, plagioclase kaolinitization is accompanied by a 50% molar volume reduction, and hence induces a maximum increase in average porosity by about 2%. Obviously, these telogenetic modifica-tions on reservoir quality were only important for the second migra-tion phase, which occurred during the Miocene (Zhao et al., 1996), since the initial oil generation and migration occurred much earlier.

46

Summary of the papers

Paper I Diagenetic evolution of aggradational and progradational fan-delta Arenites: Evidence from the Abu Alaqa group (Miocene), Gulf of Suez, Egypt Progradational (braid delta) and aggradational (fan delta) arenites of the coarse-grained fan sequences of the Abu Alaqa Group (Miocene), the Gulf of Suez, Egypt are extensively cemented by early-diagenetic calcite (micro-, equant, coarse to poikilotopic spar) and dolomite rhombs (grain-replacing and pore/void-filling). Minor amounts of diagenetic pyrite, quartz and K-feldspar overgrowths, and glaucony occur too. The �18OV-PDB (dolomite = -2.2‰ to +1.7‰; calcite = -7.0‰ to +3.3‰) and �13CV-PDB (dolomite = -4.5‰ to +0.6‰; calcite = -4.5‰ to +1.4‰) values suggest precipitation from pore waters that ranged from marine to meteoric in composition. Carbonate cement, pyrite and glaucony are most abundant in the progradational braid-delta fan sequences, particularly along the topsets (marine flooding surfaces), where dominate over coarse spar and poikilotopic calcite. Cementation by the latter calcite and the formation of moldic porosity by the dissolution of framework carbonate grains are most abundant in the aggradational fan deltas sequences, which are being attributed to the incursion of meteoric waters during sea-level lowstand.

Paper II Diagenetic and reservoir-quality evolution of shoreface sandstones in sequence stratigraphic context: The Ponta Grossa Formation (Devonian), Paraná Basin, Brazil This petrographic and geochemical study aims at linking the dis-tribution of diagenetic alterations to sequence stratigraphic framework of shoreface sandstones of the Ponta Grossa Formation (Devonian),

47

Paraná Basin, Brazil, in order to achieve better elucidation and predic-tion of diagenetic- and reservoir-quality evolution pathways. Early, near-surface, grain-coating and ooidal berthierine, ooidal goethite, grain-coating micro-quartz, glauconite, pyrite and siderite are most abundant in the transgressive system tracts (TST), particularly below the transgressive (TS) and maximum flooding surface (MFS). Near-surface diagenetic alterations in the highstand systems tract (HST) sandstones include, in addition to the formation of berthierine and siderite, the formation of grain-coating, infiltrated illitic clays as well as dissolution and kaolinitization of feldspars, which are attributed to meteoric waters percolation during fall in the relative sea level. Petrographic observations and the wide ranges of � 18OV-PDB values of siderite (-11.9‰ to -5.8‰), calcite (-11.5‰ to -5.4‰) and to, smaller extent, of Fe-dolomite/ankerite (-10.8‰ to -9.6‰) in the TST and HST deposits suggest that carbonate cementation occurred: (i) at various temperatures ranging from near surface to burial diagenesis, and (ii) from pore waters ranging from dominantly marine composi-tion to evolved basinal brines. Other burial diagenetic alterations in the sandstones include chemical compaction, cementation by quartz overgrowths, albitization of plagioclase, and transformation of kaolin-ite into dickite (mainly in the HST sandstones). The formation of grain-coating berthierine has inhibited the formation of extensive quartz overgrowths, and hence contributed to reservoir-quality preser-vation. Telogenetic alterations include dissolution and kaolinitization of framework silicates. This study demonstrates that the spatial and temporal distribution of diagenetic alterations is better elucidated when linked to the se-quence stratigraphic framework of the shoreface sandstones.

Paper III Mössbauer study of diagenetic Fe-rich minerals in Devonian clastic rocks of the Ponta Grossa Formation, Paraná Basin, Brazil Redox potential of pore waters exerts prime control on the formation of diagenetic Fe-rich minerals in sediment, and thus has profound im-pact of the geochemistry of sediments and sedimentary rocks. This study aims to utilize the Mössbauer analytical techniques to highlight the oxidation states of the diagenetic Fe-rich minerals (primarily side-rite, berthierine/chlorite, and goethite) and of bulk host Devonian, shoreface-offshore siliciclastic deposits of the Ponta Grossa Forma-

48

tion, the Parana Basin, Brazil. The distribution pattern and redox states of the Fe-rich minerals and of bulk host rocks are linked to se-quence stratigraphic framework of the succession. Minerals that form in contrasting redox pore waters conditions, such as goethite and side-rite may coexist, reflecting progressive but incomplete reduction of Fe3+ during shallow sediment burial below the seafloor. The redox reactions between mineral and pore waters in the Devonain succession were influenced by sedimentations rates and organic-matter content, which were in turn controlled by rates of changes in the relative sea level. Chlortization of berthierine, which is known to occur during burial diagenesis, did not involve noticeable changes to the Fe2+/Fe3+ ratio.

Paper IV Linking the distribution of carbonate cement to sequence stratigraphy of delta complex sandstones: evidence from the Roda sandstone Formation (Eocene), South-Pyrenean Foreland Basin, NE Spain Calcite cementation in delta complex sandstones of the Roda Sand-stone Formation (Eocene), which was promoted by the presence of abundant carbonate grains, displays various patterns, including: (i) continuously cemented layers, (ii) stratabound concretions, and (iii) concretions scattered throughout the sandstone beds. Variations in the cement-distribution pattern are attributed to variations in the rates of changes in the relative sea level relative to the rates of sediment sup-ply (i.e. the sequence stratigraphic context). Continuously cemented sandstone beds occur in the upper parts of the transgressive systems tract (TST), particularly along the parasequences boundaries (PB) and below the maximum flooding surfaces (MFS) and was presumably enhanced by prolonged residence time of the sediment below the sea-floor. Such carbonate cemented horizons can act as baffles for fluid flow, and may hence induce reservoir compartmentalization and re-gional seals to sandstone successions. Conversely, concretionary cal-cite cementation occurs in sandstone beds of the regressive systems tract (RST) and is attributed to the short residence time below the sea-floor owing to high rates of sediment supply relative to the rates of accommodation creation.

49

Paper V The diagenetic and reservoir-quality evolution of fluvial and lacustine-deltaic sandstones: evidence from Jurassic and Triassic sandstones of the Ordos Basin, Northwestern China The reservoir quality of Jurassic and Triassic fluvial and lacustrine deltaic sandstones of the intracratonic Ordos Basin (NW China) is strongly influenced by facies and various types of diagenetic modifi-cations. The fluvial sandstones have higher average He-porosity and air permeability (14.8% and 12.7 mD, respectively) than the deltaic sandstones (9.8% and 5.8 mD, respectively). In addition to extensive mechanical compaction, eodiagenesis (220-97 Ma; depth � 2000 m; T < 70oC) resulted in silicate dissolution and kaolinite formation in the Jurassic fluvial sandstones, and in smectite infiltration and minor cal-cite and siderite cementation in the Triassic fluvio-deltaic sandstones. Pervasive eogenetic carbonate cementation (> 20 vol. %) in the deltaic facies occurred along parasequence boundaries. Mesodiagenesis (97-65 Ma), which occurred during rapid subsidence to depths of 3700-4400 m, resulted in the albitization of plagioclase and crystallization of dickite, quartz overgrowths, chlorite, illite, ankerite (�

13C V-PDB = -

2.4‰ to +2.6‰; �18O V-PDB = -21.5‰ to -10‰) and calcite (�13

C V-PDB = -4.7‰ to +3.7‰; �18O V-PDB = -21.8‰ to -13.4‰). Oil emplacement retarded cementation by quartz and carbonate but had little influence on dickite, illite and chlorite formation. Retardation of quartz cemen-tation was also due to the presence of chlorite fringes around detrital quartz grains. Dickitization of eogenetic kaolinite together with the short residence time at maximum burial temperatures (105-124oC), have retarded the albitization of K-feldspars and illite formation, and hence prevented severe permeability destruction. Meteoric-water telo-diagenesis, which occurred subsequent to uplift (Eocene to the end of Neogene) to depths shallower than 2 km (T < 70oC), has resulted in slight dissolution of carbonate and feldspars, and in the formation of kaolinite.

50

Concluding Remarks

Constraining the distribution of diagenetic alterations in a sequence stratigraphic context allows a better elucidation and prediction of the spatial and temporal distribution of reservoir quality and heterogene-ity. Linking diagenetic alterations and their impact on reservoir quality to depositional facies and sequence stratigraphy in four basins have revealed that:

. The diagenetic alterations and related reservoir quality evolution pathways of paralic and shallow marine sandstones are closely linked to sequence stratigraphy, depositional facies, paleo-climatic conditions, and burial history of the sandstones. . Carbonate cement (micro-crystalline and equant calcite spars dominate over poikilotopic calcite), pyrite and glaucony are most abundant in progradational braid-delta fan sequences, particularly along the topsets (MFS). Cementation by coarse spar calcite and dolomite, and the formation of moldic porosity by the dissolution of framework carbonate grains are most common in the aggradational fan deltas sequences. . Eogenetic kaolinitization of framework silicates is largely re-stricted to the HST sandstones, whereas telogenetic kaolinite occurs in the HST and TST paralic sandstones. . Formation of grain-coating, infiltrated illitic clays as well as dis-solution and kaolinitization of feldspars are attributed to meteoric waters percolation during fall in the relative sea level. . Formation of goethite ooids in the TST sediments, being presuma-bly aided by low sedimentation rate, is concluded to be encountered during marine transgression. . Formation of glaucony, siderite spherules, and extensive grain coatings, grain-replacing and ooidal berthierine is more common in the TST than in the HST sediments, particularly below the TS and MFS, being enhanced by low sedimentation rates.

51

. The formation of grain-coating berthierine has inhibited the for-mation of extensive quartz overgrowths, and hence contributed to reservoir-quality preservation. . Grain coating chlorite in fluvio-lacustrine sandstones is attributed to chloritization of infiltrated smectitic clays. . Cementation by mesogenetic calcite and Fe-dolomite/ankerite oc-cur in both TST and HST sandstones by nucleation around eogenetic carbonate cements. . Syntaxial quartz overgrowths are most extensive in the HST sand-stones owing to the absence of extensive, grain coating berthierine. . The greater amounts of micro-porosity in the TST sandstones than in the HST sandstones are related to the greater amounts of berth-ierine/chlorite in sandstones. . Mössbauer spectroscopy study revealed that there is little or no changes encountered in the Fe2+/ Fe3+ ratio during conversion of berthierine into chlorite. In summary, this study shows that the distribution of diagenetic al-terations in siliciclastic deposits is controlled by complex array of inter-related parameters. Nevertheless, linking diagenesis to deposi-tional facies and sequence stratigraphy of paralic, shallow marine and fluvio-lacustrine deposits has important implications for better prediction of the reservoir quality ahead of exploration drilling in aquifers and oil reservoirs as well as recovery, and should applied to other depositional settings and basins.

52

Summary in Swedish

Diagenes och utveckling av reservoarkvaliteten hos paraliska, grundhavs-, och fluviolakustrina avsättningar: Kopplingar till avsättningsfacies och sekvensstratigrafi Sammanfattning Att koppla avsättningsfacies med sekvensstratigrafi hos sandstenar ger möjlighet till bättre förutsägelser vad gäller den rumsliga och temporala fördelningen av diagenetiska förändringar, och därmed utvecklingen av reservoarkvaliteten. Den här avhandligen visar att detta tillvägagångssätt är möjligt eftersom avsättningsfacies och sekvensstratigrafi innehåller användbar information om parametrar som kontrollerar ytnära diagenes, såsom förändringar i: (i) porvattenkemin, (ii) residenstiden hos sediment under vissa geokemiska villkor, (iii) detritisk sammansättning och andel extra- och intrabassängkorn, samt (iv) typ och mängd av organiskt material. Bevis från fyra fallstudier har möjliggjort utvecklingen av konceptuella modeller för fördelningen av diagenetiska förändringar och för deras påverkan på utvecklingen av reservoarkvaliteten hos sandstenar avsatta i paraliska, grundhavs-, och fluviolakustrina miljöer. Diagenetiska förändringar kan i en kontext begränsad till avsättningsfacies och sekvensstratigrafi diskuteras enligt följande: (i) karbonatcement (mikrokristallin och jämnstor kalcit dominerar över poikilotopisk), pyrit och glaukonit är vanligast i prograderande braided-fan deltasekvenser, särskilt längs maximum flooding surface (MFS) och parasekvensgränser i highstand systems tracts (HST) hos deltafacies, (ii) cementering med grovkristallin kalcit, dolomit och bildning av moldisk porositet genom upplösning av karbonatkorn är vanligast i de ytligt aggregerade fan-deltasekvenserna, (iii) eogenetisk kaolinitisering av silikater är huvudsakligen begränsad till de fluviala och paraliska HST-sandstenarna, medan teleogenetisk kaolinit också återfinns i transgressive systems tracts (TST)-sandstenarna, (iv)

53

bildning av götit-ooider i TST-sedimenten, (v) bildning av glaukonit, siderit-sfärer, samt omfattande bertierit, mer i TST- än i HST-sedimenten, särskilt under den transgressiva havsytan (TS) och MFS, (vi) kalcit- och Fe-dolomit/ankerit-cementering förekommer både i TST- och HST-sandstenarna, (vii) syntaxiella kvartsöverväxningar är mest omfattande i HST-sandstenarna på grund av ofullständig kornpåväxt av bertierit/klorit, (viii) en större andel mikroporositet hos TST-sandstenarna jämfört med HST-sandstenarna kan relateras till den större mängden bertierit/klorit i de ursprungliga sedimenten, samt (ix) kloritmantlar runt kvartskornen motverkade avsättningen av kvartsöverväxning och hindrade därmed en större förlust av primär intergranulär porositet hos de fluviolakustrina sandstenarna. Att reducera fördelningen av diagenetiska förändringar till en kontext av avsättningsfacies och sekvensstratigrafi utgör med andra ord ett kraftfullt hjälpmedel vid prospektering efter gas och olja.

54

Acknowledgements

First, I would like to thank my supervisor professor Sadoon Morad. I am deeply grateful for having been introduced to such an inspiring field as Diagenesis and Sequence Stratigraphy. Professor Morad is thanked for his patient endless revisions of my manuscripts and for being a good and very encouraging supervisor who has the ability to be both critical and positive at the same time. He taught me the ardu-ous work of science and encouraged me to explore ideas and new lines of work, which I will always carry with me. I would also like to thank the Libyan Government represented by the Higher Education section for granting a postgraduate studies at Uppsala University. I also acknowledge the NordForsk for granting some courses in Norway. I gratefully acknowledge Vale do Rio Doce Company, Brazil for providing us with drill core samples. The Yanchang Petroleum Exploration Academic Institute thanked for pro-viding part of the petrophysical data and formation-water isotopic data. Zhidan Petroleum Exploration and Development Headquarters also thanked for kindly provided access to the cores. I would like to express my gratitude to the European Science Foundation for financial supports related to traveling and accommodation for the EGU (Euro-pean Geosciences Union) that I attended in Vienna 2007 and also to Wallenbergstiftelsen for their financial supports to attend the EGU 2008.

I would like to thank Dr De Ros (Federal University of Rio Grande Sul, Porto Alegre, Brazil) for his help and kind support during the entire period of this work. I would like to extend my thanks to Profes-sor Wojtek Nemec, Dr David Gomez, Dr Alaa Salem, Dr Essam Elku-rabi, Fatima Brazil, Dr Egberto, Dr Miguel Lopez, Dr Miguel Caca, and Dr William Halland. I also thank staff members of the Department of Earth Sciences, Upp-sala University for providing inspiring working environment. Drs. Hemin Koyi, Ala Aldahan, Örjan Amcoff, Per Nysten, Peter Lazor, Håkan Sjöström, Tore Eriksson, and Christopher Talbot. Special thanks go to Kersti Gløersen for many administrative help and to Hans Harryson for help with the EMP analysis. I would like thank Dr. J.D.

55

Martín-Martín for help with the interpretation of XRD of clay miner-als. Thanks are also to the staff of the Library of the Department of Earth Sciences, Uppsala University for being so co-operative in mat-ters related to literature. I am also very grateful to Anna, Taher, Johan, and Leif for all the help with printing and technical issues. Sincere thanks go to all my colleagues and friends at the depart-ment Ashour Abouessa, Muftah Khalifa, Sebastian Willman, Yasser Abdu, Mohamed El-ghali, Khalid Al-Ramadan, Howri Mansubeg, Masoumeh Kordi, Faramarz Nilfouroushan, Zurab Chemia, Hesam Kazemeini, Ismail Nazli, Sofia Winell, Tuna Eken, Zuzana Ko-nopkova, Peter Dahlin, Kristina Zarins, Sara Sundberg, Erik Ogenhall, Anna Ladenberger, Farag Elkhutari, Lijam Hagos, Zemichael, Alireza Malemir and Mattias Lindman. I have many wonderful friends outside the academia, who helped me, supported me and made me feel at home in Uppsala. In particular I would like to thank Emin Poljarevic, Usama Hegazy, Akram Bas-sam, Yousry Abdelrahman, Giorgis Isaac, Mohamed Ramadan, and Mohamed Issa, for sharing good time, continuous support, and for their interest in my research work. At Al- Fath University, there were many professors from whom I learned a lot including Dr. Abdalla Attiqa, the former chairman of Geology Department, Dr. Ali El-Makhrouf, Dr. Omar Hammuda, and Dr. Ali Sbeta for their concern and support. Also I acknowledge Dr. Mabrouk Busrewil, Dr. Khalid Oun, Dr. Zuhair Hafi, Dr. Salem Lagha, Dr. Abd-Alatef Al-Najjar, and, my friend Dr. Amer Borgan for all good time we spend together when I was as a teacher assistant and interesting talks, although the times when the topic concerned geology were, as I recall, very few. Thanks to you all. Many thanks go to Khairi Abogassa, Ahmed Agded, Mohamed Elrutab, Hakeem Mugber, Osama Elalij, Najib Elrutab, Rabee Hlal, Milad Sraab, Adel Elrjbani, Fathi Alsaadi, Bashir Hlal, Khalid Alsu-dani, Abobaker Tnesha, Milad Ben Rhuma, Ali Elrutab, Aiad Al-Zetreni, Salah Abdelgaleel, Mohseen Elrutab, Hisham Elosta, Adel Elrabiea, and so many others, in Libya and thus, too many to list, for their support, friendship and their help in many things. Finally, I wish to thank my very dear family for the enormous sup-port and sympathy that you all have provided during this time. I am especially grateful to my wife Amira Elalij and my little daughter Em-tenan for their patience and giving me a full and rich life outside of-fice hours.

57

References

Abdel-Wahab, A., Salem, A.M. and Mcbride, E.F. (1998) Quartz cement of meteoric origin in silcrete and nonsilcrete sandstones, Lower Carboniferous, western Sinai, Egypt. journal of African Earth Sciences, 27, 277-290. Al-Aasm, I.S., Taylor, B.E. and South, B. (1990) Stable isotope analysis of multiple carbonate samples using selective acid extraction. Chemical Geology, 80, 119-125. Al-Ramadan, K., Morad, S., Proust, J.N. and Al-Asam, I. (2005) Distribution of diagenetic alterations in siliciclastic shoreface deposits within a sequence stratigraphic framework: evidence from the Upper Jurassic, Boulonnais, NW France. Journal of Sedimentary Research, 75, 943-959. Amorosi, A. (1995) Glaucony and sequence stratigraphy: a concep-tual framework of distribution in siliciclastic sequences. Journal of Sedimentary Research, B65, 419-425. Arnott, R. W. C. (2007) Stratal architecture and origin of lateral ac-cretion deposits (LADs) and conterminuous inner-bank levee deposits in a base-of-slope sinuous channel, lower Isaac Formation (Neopro-terozoic), East-Central British Columbia. Canada Marine and Petro-leum Geology, 24, 515-528. Arnott, R. W. C. (1996) Questioning The Concept Of Relative Sea Level. American Association of Petroleum Geologists, 80, A6- A6. Bloch, S., and Mcgowen, J.H. (1994) Influence of depositional envi-ronment on reservoir quality prediction. In: Wilson, M.D., (Ed.): Res-ervoir quality assessment and prediction in clastic rocks. SEPM Short Course, 30, 41-58. Bloch, S., Lander, R.H., Bonnell, L. (2002) Anomalously high po-rosity and permeability in deeply buried sandstone reservoirs: origin and predictability. American Association of Petroleum Geologists, 86, 301-328. Boles, J.R. and Franks, S.G. (1979) Clay diagenesis in the Wilcox sandstones of southern Texas: implications of smectite diagenesis on sandstone cementation. Journal of Sedimentary Petrology, 49, 55-70.

58

Boles, J.R. (1982) Active albitization of plagioclase, Gulf Coast Ter-tiary. American Journal of Science, 282, 165-180. Brown, L.F., and Fisher, W.L. (1977) Seismic stratigraphic interpre-tation of depositional systems: examples from Brazil rift and pull-apart basins. American Association of Petroleum Geologists, 26, 213-248. Choquette, P.W., and Pray, L. (1970) Geologic nomenclature and classification of porosity in sedimentary carbonates. American Asso-ciation Petroleum Geologists Bulletin, 54, pp. 207–250 Claypool, G.E., and Kaplan, I.R. (1974) The origin and distribution of methane in marine sediments, In: I.R. Kaplan (Eds.) Natural Gases in Marine Sediments Plenum Press, New York, pp. 97-139. Coe, A.L. (2003) The Sedimentary Record of Sea-Level Change, in Coe A. (ed.), Cambridge University Press, Cambridge, 286p. Cross, T.A. (1988) Controls on coal distribution in transgressive-resgressive cycles, Upper Cretaceous, Western Interior, U.S.A. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G.S.C., Posamentier, H.W., Ross, C.A., and Van Wagoner, J.C. (eds.), Sea-level changes: an inte-grated approach, SEPM Society for Sedimentary Geology Special Publication, 42, 371-380. Curtis, C.D. (1987) Mineralogical consequences of organic matter degradation in sediments: Inorganic/organic diagenesis. In: J.K. Leg-gett and G.G. Zuffa (Eds.), Marine Clastic Sedimentology. Graham and Trotman, London, pp. 108-123. Curtis, C.D., Coleman, M.L., and Love, L.G. (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions. Geochimica et Cosmo-chimica Acta, 50, 2321-2334. De Ros, L. F. (1998) Heterogeneous generation and evolution of diagenetic quartzarenites in the Silurian-Devonian Furnas Formation of the Paraná Basin, southern Brazil. Sedimentary Geology, 116, 99-128. De Ros, L.F., Sgarbi, G.N.C. and Morad, S. (1994) Multiple authi-genesis of K-feldspar in sandstones: evidence from the Cretaceous Areado Formation, São Francisco Basin, central Brazil. Journal of Sedimentary Research, A64, 778-787. Ehrenberg, S.N. (1993) Preservation of anomalously high porosity in deeply buried sandstones by grain-coating chlorite: examples from the Norwegian continental shelf. American Association of Petroleum Ge-ologists, 77, 1260-1286. Ehrenberg, S.N., Aagaard, P., Wilson, M.J., Fraser, A.R. and Duthie, D.M.L. (1993) Depth-dependant transformation of kaolinite to dickite in sandstones of the Norwegian continental shelf. Clay Min-erals, 28, 325-352.

59

Emery, D., and Myers, K.J. (1996) Sequence Stratigraphy. London: Blackwell Science, 297 pp. Friedman, I. and O'Neil, J.R. (1977) Compilation of stable isotopic fractionation factors of geochemical interest: US Geological Survey, Professional Paper 440-KK, 12 p. Froelich, P.N., Klinkhammer, G.P., Bender, M.L., Luedtke, N.A., Heath, G.R., Cullen, D., Dauphin, P., Hammond, D., Hartman, B., Maynard, V. (1979) Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis. Geo-chimica et Cosmochimica Acta, 43, 1075-1090. Gallowy, W.E. (1989) Genetic dtratigraphic sequence in basin analy-sis I: architecture and genesis of flooding surface bounded deposi-tional units. American Association of Petroleum Geologist, 73, 125-142. Garzanti, E. (1991) Non-carbonate intrabasinal grains in arenites: their recognition, significance, and relationship to eustatic cycles and tectonic setting. Journal of Sedimentary Petrology, 61, 959-975. Gawthorpe, R.L., Hurst, J.M. and Sladen, C.P. (1990) Evolution of Miocene footwall derived coarse grained deltas. Gulf of Suez, Egypt: Implications for Exploration. American Association of Petroleum Ge-ologists, 74, 1077-1086. Gawthorpe, R.L., Sharp, I., Underhill, J.R., and Gupta, S. (1977) Linked sequence stratigraphic and structural evolution of propagating normal faults. Geology, 25, 795-798. Gehring, A.U., (1989) The formation of geothitic ooids in condensed Jurassic deposits in northern Switzerland. In: E.D. Young and W.E.G. Taylor (Eds.), Phanerozoic Ironstones. Gaological Society of London, Special Publication, 46, 133-139. Ghiorse, W.C. (1984) Biology of iron- and manganese-depositing bacteria. Annual Reviews in Microbiology, 38, 515-550 Görlich K., Görlich E.A., Tomala K., Hrynkiewicz A.Z. and Pham Quoc Hung (1989) 57Fe Mössbauer study of a sediment column in the Gdansk Basin, Baltic Sea. paleoenvironmental application. Marine Geology, 88, 49–69. Hornibrook E.R.C. and Longstaffe F., (1996) Betrhierine from the lower Cretaceous Clearwater Formation, Alberta, Canada. Clays and Clay Minerals, 44, 1-21. Hunt, D. and Tucker, M.E., (1992), Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall. Sedimentary Geology, 81, 1-9. Hurst, A. and Nadeau, P.H. (1995) Clay microporosity in reservoir sandstones: an application of quantitative electron microscopy in petrophysical evaluation. American Association of Petroleum Geolo-gists, 79, 563-573.

60

Irwin, H., Coleman, M.L., and Curtis, C.D. (1977) Isotopic evi-dence for source of diagenetic carbonates formed during burial of or-ganic-rich sediments. Nature, 269, 209-213. Jeans, C.V., Merriman, R.J., Mitchell, J.G. and Bland, D.J., (1982) Volcanic clays in the Cretaceous of Southern England and Northern Ireland. Clay Minerals, 17, 105-156. Jervey, M.T. (1988) Quantitative geologic modeling of siliciclastic rock sequences and their seismic expression. In: Wilgus, C.K., Hast-ings, B.S., Kendall, C.G.S.C., Posamentier, H.W., Ross, C.A., and Van Wagoner, J.C. (eds.), Sea-level changes: an integrated approach, SEPM Society for Sedimentary Geology Special Publication, 42, 47-69. Ketzer, J.M. and Morad, S. (2006) Predictive distribution of shallow marine, low-porosity (pseudomatrix-rich) sands tones in a sequence stratigraphic framework-example from the Ferron sandstone, Upper Cretaceous, USA. Marine and Petroleum Geology, 23, 29-36. Ketzer, J.M., Holz, M., Morad, S. and Al-Aasm, I.S. (2003a) Se-quence stratigraphic distribution of diagenetic alterations in coalbear-ing, paralic sandstones: Evidence from the Rio Bonito Formation (early Permian), southern Brazil. Sedimentology, 50, 855-877. Ketzer, J.M., Morad, S. and Amorosi, A. (2003b) Predictive diagenetic clay-mineral distribution in siliciclastic rocks within a se-quence stratigraphic framework. In: Clay Mineral Cements in Sand-stones (Ed. by R.H. Worden and S. Morad), Blackwell. Oxford, Inter-national Association of Sedimentologists, Special Publication, 34, 42- 59. Ketzer, J.M., Morad, S., Evans, R. and Al-Aasm, I.S. (2002) Dis-tribution of diagenetic alterations in fluvial, deltaic, and shallow ma-rine sandstones within a sequence stratigraphic framework: Evidence from the Mullaghmore Formation (Carboniferous), NW Ireland. Jour-nal of Sedimentary Research, 72, 760-774. Kidwell, S.M. (1989) Stratigraphic condensation of marine transgres-sive records: origin of major shell deposits in the Miocene of Mary-land. The Journal of Geology, 97: 1-24. Konhauser, K. O., (1998) Diversity of bacterial iron mineralization. Earth-Science Reviews, 43, 91-121 Krawinkel, H. and Seyfried, H. (1996) Sedimentologic, pa-laeoecologic, taphonomic and ichnologic criteria for high-resolution sequence analysis: a practical guide for the identification and interpre-tation of discontinuities in shelf deposits. Approaches to sequence stratigraphy. R-Group and A. Van de Weed Andrew. Amesterdam, Neterlands, Elsevier. 102, 1-2: 79-110.

61

Lanson, Beufort, D., Berger, G., Bauer, A., and Cassagnabere, A., (2002) Authigenic kaolin and illitic mineralsduring burial diagenesis of sandstones: a review. Clay Minerals, 37, 1-22. Lindsay, J.F., Kennar, J.M., Southgate, P.N. (1993) Application of sequence stratigraphy in an intracratonic setting, Amadeus basin, cen-tral Australia. In: H. W. Posamentier; C.P. Summerhayes; B.U. Haq; G.P. Allen (eds.), Sequence stratigraphy and facies associations. Ox-ford, Blackwell, IAS – Special Publication, 18, 605-632. Loomis, J.L., and Crossey, L.J. (1996) Diagenesis in a cyclic, re-gressive siliciclastic sequence: the Point Lookout Sandstone, San Juan Basin, Colorado. In: Crossey, L.J., Loucks, R., and Totten, M.W. (eds.), Siliciclastic diagenesis and fluid flow: concepts and applica-tions, SEPM Society for Sedimentary Geology Special Publication, 55, 23-36. McAulay, G. E., Burley, S. D., Fallick, A. E., and Kusznir, N. J. (1994) Palaeohydrodynamic fluid flow regimes during diagenesis of the Brent Group in the Hutton-NW Hutton reservoirs; constraints from oxygen isotope studies of authigenic kaolin and reverse flexural mod-elling. Clay Minerals, 29, 609-626. McBride, E.F. (1989) Quartz cement in sandstones: a review. EarthSciences Reviews, 26, 69-112. McKay, J.L., Longstaffe, F.J. and Plint, A.G. (1995) Early diagene-sis and its relationship to depositional environment and relative sealevel fluctuations (Upper Cretaceous Marshybank Formation, Al-berta and British Columbia). Sedimentology, 42, 161-190. Morad, S., and De Ros, L.F. (1994) Geochemistry and diagenesis of Stratabound calcite cement layers within the Rannoch Formation of the Brent Group, Murchison Field, North Viking Graben (northern North Sea) - comment. Sedimentary Geology, 93, 135-141. Morad, S., Ben Ismail, H., De Ros, L.F., Al-Aasm, I.S., and Ser-rhini, N-E. (1994) Diagenesis and formation water chemistry of Tri-assic reservoir sandstones from southern Tunisia. Sedimentology, 41, 1253-1272. Morad, S., Bergan, M., Knarud, R., and Nystuen, J.P. (1990) Al-bitization of detrital plagioclase in Triassic reservoir sandstones from the Snorre field, Norwegian North Sea. Journal of Sedimentary Pe-trology, 60, 411-425. Morad, S., Ketzer, J.M. and De Ros, L. F. (2000) Spatial and tem-poral distribution of diagenetic alterations in siliciclastic rocks: impli-cations for mass transfer in sedimentary basins. Sedimentology, 47, 95-120. Moss, S.J., and Tucker, M.E. (1995) Diagenesis of Barremian-Aptian platform carbonates (the Urgonian Limestone Formation of SE

62

France): near-surface and shallow-burial diagenesis. Sedimentology, 42, 853-874. Mowers, T.T., Budd, D.A. (1996) Quantification of porosity and permeability reduction due to calcite cementation using computer-assisted petrographic image analysis technique. American Association of Petroleum Geologists, 80, 309-322. Oelkers, E.H., Bjørkum, P.A. and Murphy,W.M. (1996) A petro-graphic and computational investigation of quartz cementation and porosity reduction in North Sea sandstones. American Journal of Sci-ence, 296, 420-452. Pittman, E.D., Larese, R.E. and Heald, M.T. (1992) Clay coats: occurrence and relevance to preservation of porosity. In: Origin, Diagenesis, and Petrophysics of Clay Minerals in Sandstones (Ed. by D.W. Houseknecht and E.D. Pittman), Society for sedimentary Geol-ogy Special Publication, 47, 241-255. Plint, A. G. (1988) Sharp-based shoreface sequences and "offshore bars" in the Cardium Formation of Alberta; their relationship to rela-tive changes in sea level. In: Sea level changes: an integrated approach (Ed. by C.K. Wilgus, B.S., Hastings, H. Posamentier, J. Van Wagoner, C.A. Ross and C.G.St.C. Kendall), Society for sedimentary Geology Special Publication, 42, 357-370. Posamentier, H.W. and Allen, G.P. (1999) Siliciclastic sequence stratigraphy-concepts and applications. Society for sedimentary Geol-ogy, Concepts in Sedimentology and Paleontology, 7, 210. Posamentier, H.W., Jervey, M.T. and Vail, P.R. (1988) Eustatic controls on clastic deposition I- conceptual framework. In: Sea level changes: an integrated approach (Ed. by C.K. Wilgus, B.S., Hastings, H. Posamentier, J. Van Wagone, C.A. Ross and C.G.St.C. Kendall), Society for sedimentary Geology Special Publication, 42, 109-124. Postma, D. (1993) The reactivity of iron oxides in sediments: A ki-netic approach. Geochimica et Cosmochimica Acta, 57, 5027–5034. Read, J.F., and Horbury, A.D. (1993) Eustatic and tectonic controls on porosity evolution beneath sequence-bounding unconformities and parasequences disconformities on carbonate platforms In: Horburt, A.D., and Robinson, A.G., (Eds.), Diagenesis and basin development, American of Petroleum Geologists Studies in Geology, 36, 155-197. Robinson, S.G. (2000) Early diagenesis in an organic-rich turbidite and pelagic clay sequence from the Cape Verde Abyssal Plain, NE Atlantic: magnetic and geochemical signals. Sedimentary Geology, 143, 91-123. Saigal, G.C., Morad, S., Bjørlykke, K., Egeberg, P.K. and Aa-gaard, P. (1988) Diagenetic albitization of detrital K-feldspar in Ju-rassic, Lower Cretaceous, and Tertiary clastic reservoir rocks from

63

offshore Norway, I. Textures and origin. Journal of Sedimentary Pe-trology, 58, 1003-1013. Salem, A. Abdel-Wahab, A. and McBride, E. F. (1998) Diagenesis of shallowly buried cratonic sandstones, southwest Sinai, Egypt. Sedimentary Geology, 119, 311-335. Schulz, J.L., Boles, J.R., Tilton, G.R. (1989) Tracking calcium in the San Juaquin basin, California: a strontium isotopic study of carbonate cements at North Cole Levee. Geochimica et Cosmochimica Acta, 53, 1991-1999. South, D.L., and Talbot, M.R. (2000) The sequence stratigraphic framework of carbonate diagenesis within transgressive fan-delta de-posits, Sant Llorenc Del Munt fan-delta complex, SE Ebro Basin, NE Spain. Sedimentary Geology, 183, 179-198. Stonecipher, S.A., R.D. Winn, Jr., and M.G. Bishop. (1984) Diagene-sis of the Frontier Formation, Moxa Arch: a function of sandstone geometry, texture and composition, and fluid flux, in D.A. McDonald and R.C. Surdam, eds., Clastic Diagenesis: American Association of Petroleum Geologists, 37, 289-316. Suttill R.J., Turner P. and Vaughan D.J. (1982) The geochemistry of iron in Recent tidal-flat sediments of the Wash area, England: a mineralogical, Mössbauer, and magnetic study. Geochimica et Cos-mochimica Acta, 46, 205-217. Taylor, K.G., Gawthorpe, R.L. and Van Wagoner, J.C. (1995) Stratigraphic control on laterally persistent cementation, Book Cliffs, Utah. Journal of Geological Society of London, 152, 225-228. Taylor, K.G., Gawthorpe, R.L., Curtis, C.D., Marshall, J.D. and Awwiller, D.N. (2000) Carbonate cementation in a sequence strati-graphic framework: Upper Cretaceous sandstones, Book Cliffs, Utah-Colorado. Journal of Sedimentary Research, 70, 360-372. Triplehorn, D.M. (1966) Morphology, internal structure and origin of glauconites pellets. Sedimentology, 6, 247–266. Tucker, M. E. (1993) Carbonate diagenesis and sequence stratigra-phy. Sedimentology Review 1: 51-72. Vail, P.R., Mitchum, R.M., and Thompson, S. (1977) Seismic stratigraphy and global changes of sea level, part 3: relative changes of sea level from coastal onlap. In: Payton, C.E. (ed.), Seismic strati-graphy - applications to hydrocarbon exploration, American Associa-tion of Petroleum Geologists, 26, 63-81. Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. and Rahma-nian, V.D. (1990) Siliciclastic Sequence Stratigraphy in Well Logs, Cores, and Outcrops. American Association of Petroleum Geologists Methods Exploration Series, 7, 55. Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., Vail, P.R., Sarg, J.F., Loutit, T.S. and Hardenbol, J. (1988) An overview

64

of the tundamentals of sequence stratigraphy and key definitions. In: Wilgus, C.K., et al., (Eds), Sea Level Changes: An Integrated Ap-proach, Scoiety of Economic paleontologists and Mineralogists, Spe-cial Publication 42, 39-46. Veizer, J., Ala, D., Azmy, K., Bruckschen, P., Buhl, D., Bruhn, F., Carden, G.A.F., Diener, A., Ebneth, S., Godderis, Y., Jasper, T., Korte, C., Pawellek, F., Podlaha, O. and Strauss, H. (1999). "87Sr/86Sr, �13C and �18O evolution of Phanerozoic seawater". Chemi-cal Geology , 161, 59-88. Walderhaug, O. (1994) Temperature of quartz cementation in Juras-sic sandstones from the Norwegian continental shelf-evidence from fluid inclusions. Journal of Sedimentary Research, A64, 311-323. Walderhaug, O. and Bjørkum, P.A. (2003) The effect of stylolite spacing on quartz cementation in the Lower Jurassic Stø Formation, southern Barents Sea. Journal of sedimentary Research, 73, 146-156. Wilkinson, M. (1989) Discussion: Evidence for surface reaction-controlled growth of carbonate concretions in shales. Sedimentology, 36, 951-953. Worden, R.H. and Morad, S. (2000) Quartz cementation in oil field sandstones: a review of the key controversies. In: Quartz cementation in sandstones (Ed. by R. H. Worden and S. Morad), International As-sociation for Sedimentologists Special Publication, Blackwell Publish-ing, Oxford, 29, 1-20. Worden, R.H., and Morad, S. (2003) Clay minerals in sandstones: controls on formation, distribution and evolution. In: R.H. Worden and S. Morad (Eds.), Clay Minerals Cements Sandstones, Interna-tional Association for Sedimentologists Special Publication, Black-well Publishing, Oxford, 34, 3-41. Zhao, M., Ahrendt, H., Wemmer, K. and Behr, H. (1996) Silu rian-Devonian and Jurassic thermal events in the Ordos Basin, China: indi-cations from K-Ar dating on illites. Acta Geologica Sinica, 9, 435-446. Zuffa, G.G. (1980) Hybrid arenites: their composition and classification. Journal of Sedimentary Petrology, 50, 21-29.Zuffa, G.G., Cibin, U. and Di Giulio, A. (1995) Arenite petrography in sequence stratigraphy. The Journal of Geology, 103, 451-459.

Acta Universitatis UpsaliensisDigital Comprehensive Summaries of Uppsala Dissertationsfrom the Faculty of Science and Technology 448

Editor: The Dean of the Faculty of Science and Technology

A doctoral dissertation from the Faculty of Science andTechnology, Uppsala University, is usually a summary of anumber of papers. A few copies of the complete dissertationare kept at major Swedish research libraries, while thesummary alone is distributed internationally through theseries Digital Comprehensive Summaries of UppsalaDissertations from the Faculty of Science and Technology.(Prior to January, 2005, the series was published under thetitle “Comprehensive Summaries of Uppsala Dissertationsfrom the Faculty of Science and Technology”.)

Distribution: publications.uu.seurn:nbn:se:uu:diva-8986

ACTA

UNIVERSITATIS

UPSALIENSIS

UPPSALA

2008

diagenesis and reservoir-quality evolution of paralic, shallow …172262/fulltext01.pdf ·...

Documents