the meso-cenozoic tectonics and petroleum potential of ...acr/migrated/beringresources/articles...

www.elsevier.com/locate/rgg

The Meso-Cenozoic tectonics and petroleum potential of West Siberia

V.A. Kontorovich *

Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia

Received 21 October 2008

Abstract

The relationship between the petroleum potential of the West Siberian province and the Mesozoic to Cenozoic tectonic processes is analyzed.The studies were based on structural and isopach maps of seismogeologic megacomplexes compiled from generalized geological and geophysicaldata on the province at the Trofimuk Institute of Petroleum Geology and Geophysics as well as on the results of interpretation of regionalseismic CDP (common depth point) profiles. The main stages of formation of structures of different ranks and faults have been established.It is shown that the petroleum potential of the province was determined mainly by its structure and tectonic processes at the Cenozoic stageof evolution. At that time, the Koltogory–Urengoi megatrench formed, which became the main zone of hydrocarbon generation, as well aslarge positive structures—petroleum accumulation zones. Also, disjunctions originated, which served as channels for hydrocarbon migrationfrom the oil source rocks of the Bazhenovo Formation to the main Neocomian and Aptian–Albian–Cenomanian petroleum reservoirs of theprovince.© 2009, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Keywords: structure; tectonic elements; faults; disjunctions; time sections; regional seismic profiles; petroleum potential; Jurassic; Neocomian; Aptian–Albian;Cenomanian; Turonian; Cenozoic; Koltogory–Urengoi megatrench; West Siberian petroliferous province

Introduction

This paper deals with analysis of the relationship betweenthe petroleum potential of the West Siberian Basin andMesozoic to Cenozoic tectonic processes, in particular, thedisjunction formation.

Structural-tectonic constructions and study of the tectonicevolution of sedimentary basins are based on analysis ofstructural maps of stratigraphic reference levels and isopachmaps of sedimentary complexes. Structural maps reflect themodern structure of different stratigraphic levels, whereasisopach maps allow for the assessment of tectonic processesfor different stages of regional evolution.

Though the systematic study of the geologic structure ofWest Siberia has been carried out for more than 50 years, thelast large regional summary of geological and geophysical dataon this territory dates back to 1975, published as a monograph(Kontorovich et al., 1975). In the last three decades, a giantvolume of geological and geophysical data was accumulated.Their summary, analysis, and comprehension can open up a

new stage in the history of the West Siberian petroleumprovince (PP).

Such regional generalization works are currently carried outat the Trofimuk Institute of Petroleum Geology and Geophys-ics, Novosibirsk, in cooperation with specialists of manyscientific and industrial geological institutions.

In the context of this research, a new generation ofelectronic structural and isopach maps of sedimentary com-plexes was compiled, which takes into account all availablegeological and geophysical information (Kontorovich et al.,2001). These materials and results of interpretation of regionalseismic CDP profiles in the West Siberian Basin served as abasis for the reported studies.

Petroleum-promising and seismogeologic megacomplexes

At the early stages of study of the West Siberian Basin,Gurari et al. (1966) noted that the largest petroleum accumu-lations occurred in the deposits overlain by extending refer-ence shale members (seals) that were differentiated intoregional, zonal, and local seals. Somewhat later, Karogodin

Russian Geology and Geophysics 50 (2009) 346–357

* Corresponding author.E-mail address: [email protected] (V.A. Kontorovich)

1068-7971/$ - see front matter D 2009, IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

doi:10.1016/j.rgg.200 0 09. 3. 12

(1974) and Kontorovich et al. (1981) recognized an additionalclass of seals, megaregional.

Four petroleum-promising megacomplexes overlain bymegaregional seals in the roof are recognized in the WestSiberian sedimentary cover: Jurassic, Neocomian, Aptian–Al-bian–Cenomanian, and Turonian–Danian. They are subdi-vided into petroleum-promising complexes by zonal and localshale members.

The Jurassic megacomplex is overlain by the BazhenovoFormation and coeval strata (Upper Jurassic, Volgian); theNeocomian one, by the Koshai member of the Alym Forma-tion (Lower Cretaceous, Aptian); the Aptian–Albian–Cenoma-nian megacomplex, by the Kuznetsov Formation (UpperCretaceous, Turonian); and the Turonian–Danian megacom-plex, by the Talitsa Formation (Paleocene, Danian).

A specific feature of megaregional seals is that they are allcomposed of marine transgressive shale members of persistentthickness, which formed in the epochs of tectonic quiescenceand were widespread in vast areas of West Siberia. One mightsuggest that by the time of their formation, the surfaces ofthese seals were planed and, hence, could be used forpaleostructural and paleotectonic reconstructions.

It is also important that these deposits have abnormally lowacoustic properties; therefore, the most powerful reflectingseismic horizons are confined to these geologic benchmarks(Fig. 1).

The reflecting benchmark horizons recognized in thesection of the Meso-Cenozoic sedimentary cover are mappedby many researchers throughout the West Siberian Basin butare differently indexed by geologists working in differentregions. The accepted indices and stratigraphic occurrence ofseismic benchmark horizons are listed in Table 1.

By the presence of regional seismic benchmarks, fiveseismogeologic megacomplexes are recognized in the sectionof the Meso-Cenozoic sedimentary cover, which generallycorrespond to petroleum-promising megacomplexes: Jurassic,Berriasian–Aptian, Albian–Turonian, Coniacian–Danian, andCenozoic. The difference in the names of petroleum-promisingand seismogeologic megacomplexes is explained by the factthat the former contain shale members at the base. Forexample, the Koshai member of the Alym Formation occursat the base of the Aptian–Albian–Cenomanian complex.Seismic benchmark horizons are localized in the roofs of shaleseals and, hence, in the roofs of seismogeologic megacom-plexes. This is obviously of little significance. But in the oilcontext, this reservoir–confining-bed relationship seems morelogical. All the above seismic benchmarks are reliably tracedthroughout West Siberia, including the Kara Sea water area.

Figure 2 shows time sections along the Reg110D andn881006 profiles, which evidence the identical geologicstructures of the basin on the continent (Reg110D) and in theKara Sea (n881006).

Fig. 1. Seismogeologic megacomplexes (fragment of time section along regional profile 4, Salym district). Hereafter: 1, reflecting seismic horizons; 2, faults.

V.A. Kontorovich / Russian Geology and Geophysics 50 (2009) 346–357 3477

Meso-Cenozoic tectonic processes. Stages of structure formation

At the Jurassic stage, preceding the formation of thesedimentary cover, Paleozoic deposits, which in the most areaof West Siberia had undergone folding in the Hercynian, weresubjected to rifting in the Early Triassic. Afterwards, therewas a gap in sedimentation in a great part of the basin area,as evidenced from the absence of Late Triassic deposits fromthe southern and central regions of the geosyneclise.

The tectonic-activity stage was in the Early Jurassic, i.e.,at the same time as the Kimmerian Orogeny. Concurrent withthe overall subsidence of weakened suprarift zones where thepre-Jurassic basement was mainly composed by basalts, therewas a tendency toward a relative uplift in the macroblockswhere the basement was repesented by Devonian and Carbon-iferous carbonate and terrigenous rocks. At that time, the axialpart of the West Siberian geosyneclise was localized in thezone of the Koltogory–Urengoi graben-rift, i.e., where it istoday, which determined the formation of the supra-riftdepression of the Koltogory–Urengoi megatrench, in whichthe maximum thickness of Jurassic sediments accumulated.

The macroblocks of the pre-Jurassic basement are localizedalong the edges of the Koltogory–Urengoi megatrench. Inplan, they correspond to modern first-order positive, such asthe Nizhnevartovsk, Kaimysov, and Aleksandrovskoe arches,Middle Vasyugan megabar, etc. The macroblocks are cut bynumerous faults into rather monolithic erosional-tectonic in-liers corresponding in size to third- and fourth-order struc-tures—local domes and arches (hereafter, we use theclassification proposed at the Trofimuk Institute of PetroleumGeology and Geophysics (Kontorovich, 1999; Kontorovichet al., 2004)).

Though the macroblocks and local erosional-tectonic inliersof the basement generally tended to grow throughout theJurassic, these processes were the most active in the EarlyJurassic and Aalenian. As the sedimentary cover formed, the

intensity of vertical tectonic movements was significantlyreduced. By the Bajocian, the basin paleorelief was almostcompletely leveled: The Bajocian paleorelief lacked largeuplifted and subsided zones.

The above fact is evidenced from the development ofLower Jurassic deposits only within depression zones and theirabsence from large positive structures, whereas the Bajocian–Bathonian and Upper Jurassic deposits formed throughout theWest Siberian Basin. The only exception is the occasional,most contrasting erosional-tectonic inliers of the basement inthe periclinal parts of large first-order positive structures,which continued to develop actively up to the Volgian. Amongsuch blocks are the Krivolutsk and Mezhov granite massifs,whose pre-Jurassic deposits are overlain by the BazhenovoFormation.

The Jurassic tectonic processes were accompanied by theactive formation of disjunctions. Since the most intensevertical movements date from the Early Jurassic and Aalenian,most of the faults that formed at this stage die out in the basalhorizons of the sedimentary cover.

The Berriassian–Aptian stage was a stage of tectonicquiescence, with its peak coinciding in time with the accumu-lation of the Bazhenovo Formation. In the late Volgian, thequiescence gave way to another episode of tectonic activity.At that time, in the southern and central regions of WestSiberia, only small uniform erosional-tectonic inliers of thepre-Jurassic basement exhibited the inherited tendency forgrowth. This phenomenon took place on the background ofthe regional undercompensated downwarping of the basin thatstarted in the Late Jurassic, which led to the shift of its axisfar westward.

At this stage, third- and fourth-order positive structures—local domes and arches—formed above the local blocks of thebasement in the relief of the Jurassic roof. The growth oferosional-tectonic inliers and, hence, the formation of localuplifts in the Jurassic strata were most active at the early stages

Table 1Indexation and stratigraphic occurrence of seismic horizons accepted in different regions

Indexation accepted in the Khanty-Mansi and Yamal-Nenets Autonomous Districts and Tyumen’ Region

Indexation accepted in the Tomsk, Novosibirsk,and Omsk Regions

Stratigraphic occurrence

A B2 Bottom of sedimentary cover

B Roof of the Bazhenovo Formation and itsanalogs, Upper Jurassic, Volgian

IIa Bottom of the Bazhenovo Formation and itsanalogs, Upper Jurassic, Volgian

M III Koshai member of the Alym Formation and itsanalogs, Lower Cretaceous, Aptian

G IV Kuznetsov Formation, Upper Cretaceous, Turonian

S V Talitsa Formation, Paleogene, Early Paleocene,Danian

T Lower Jurassic roof

348 V.A. Kontorovich / Russian Geology and Geophysics 50 (2009) 346–3577

Fig.

2.

Com

pari

son

of w

ave

fiel

ds i

n th

e co

ntin

enta

l ba

sin

(Pro

f. R

eg11

0D)

and

in t

he K

ara

Sea

wat

er a

rea

(Pro

f. n

8810

06).


of formation of the Neocomian complex, mainly in theBerriassian–Valanginian.

As evident from the fragment of time section along theprofile crossing the Gerasimovka and West Ostanino localuplifts (Fig. 3), the anticlinal structures formed precisely abovethe erosional-tectonic inliers in the Bazhenovo Formation.

No large positive and negative structures existed in theAptian relief of the Jurassic roof at that time. The existenceof local uplifts and the absence of large tectonic structuresfollow from two facts: (1) the Neocomian clinoforms are notaffected by the modern first-order positive and negativestructures; (2) at the early stages of study of the clinoformcomplex it was noted that the Achimov sand beds with betterreservoir properties occur on the eastern slopes of local uplifts,whereas the western slopes are formed by fine-grainedcalcareous sandstones. This is due to the presence of smallpaleostructures in the Bazhenovo Formation relief, whichhampered the transport of coarse-grained terrigenous material.

The above conclusions are unambiguously confirmed bypaleoreconstructions made after seismic time sections.

Two composite time sections and a series of paleosectionsshown in Fig. 4 are constructed along the profiles crossinglarge positive and negative tectonic structures and reflect thedynamics of changes in the basin structure. The regionalprofile Reg IX crosses the Kaimysov dome, Nyurol’kamegabasin, and Pudino mesoarch. The time section along theprofile Reg I runs along the line Nizhnevartovsk dome–Kol-togory mesotrough–Aleksandrovskoe dome–eastern framingof the plate. The paleosections reflecting the area structure inthe Aptian (Fig. 4, a) unambiguously confirm the absence oflarge positive and negative structures from the relief ofJurassic deposits at that time.

The above conclusion was drawn first of all for structuresformed above the erosional-tectonic inliers of the pre-Jurassicbasement, which complicate larger tectonic structures in the

modern relief of the Bazhenovo Formation. The more con-trasting were the protrusions in the Jurassic, the more intenselythey developed in the Neocomian. In the northern regions ofWest Siberia, where contrasting erosional-tectonic inliers werevirtually lacking (they were all overlain by a very thick unitof Triassic and Jurassic terrigenous deposits), positive struc-tures almost did not form at this stage.

One of such “rootless” (not confined to the basement inlier)structures is the Central Urengoi mesoarch, in which theUrengoi petroleum field is localized. At the same time, localblocks within the Etypur and Vyngapur mesoarches, Northerndome, etc. showed a slight tendency for growth.

In the Berriassian–Aptian, large isometric depressions, suchas the Kara, Antipayuta–Tadebeyakh, and Bol’shaya Khetamegasyneclises, began to form in the relief of the BazhenovoFormation in the extreme north of the basin.

Thus, the performed analysis showed that the Berriassian–Aptian stage of evolution was the main in the formation ofrelatively small third- and fouth-order tectonic structures inthe Jurassic and Neocomian deposits. At that time, mainlyvertical tectonic movements took place, in which smallmonolithic blocks of the pre-Jurassic basement were involved.By the end of the Aptian, almost all third- and fourth-orderstructures had already formed in the paleorelief of theBazhenovo Formation in the southern and central regions ofWest Siberia. These were domes, arches, depressions, andtroughs. They were not united into large tectonic structures oflower ranks, and their hypsometric position relative to eachother was far from the modern one.

Analysis of seismic materials shows that the Berriassian–Aptian evolution of the province was accompanied by activefaulting. Disjunctions cut the Bazhenovo Formation and dieout in the Neocomian. This is observed, e.g., in the southernpart of the Kaimysov dome, in the Aleksandrovskoe mesoarch.Since rather monolithic inliers of the pre-Mesozoic basement,corresponding in size to third- and fourth-order structures,underwent vertical tectonic movements at this stage, theformed disjunctions are short and differently aligned.

The Albian–Turonian stage. The Late Cretaceous proc-esses virtually did not affect the modern tectonic structure ofthe southern and central parts of the study region—there wereno active vertical tectonic motions at this stage. The paleosec-tions leveled along the upper boundary of the KuznetsovFormation (Fig. 4, b) evidence that the Jurassic paleorelief didnot significantly differ from the Aptian one in the Turonian.

In the southern and central parts of the basin, the Turonianpaleorelief of the Bazhenovo Formation and Koshai memberlacked large positive structures similar to the Kaimysov,Nizhnevartovsk, Aleksandrovskoe, and Northern domes, Ety-pur and Vyngapur mesoarches, Chasel’ka megaarch, etc.Large troughs and depressions were also lacking.

By the Turonian, the Yamal–Kara regional depressioncomplicated by the Kara, Antipayuta, Tadebeyakh, andBol’shaya Kheta megasyneclises had already been formed.Note that by the time of the accumulation of the KuznetsovFormation in the relief of the Bazhenovo Formation, theMessoyakha ridge had acquired its modern contours.

Fig. 3. Fragment of time section along profile 841232. The Gerasimovka andWest Ostanino areas.


The Cenozoic (post-Turonian) stage of tectonic activityexerted the greatest effect on the modern architecture of theWest Siberian megasyneclise. Two crucial regional processestook place at that time: intense subsidence of the central partof the basin relative to the plate framing and formation of theKoltogory–Urengoi megatrench, the largest suprarift depres-sion crossing almost the entire basin from south to north, inthe structural plans of Jurassic and Cretaceous horizons.

Both of these processes are reflected in time sections(Fig. 4). As noted above, the time sections were obtainedalong the profiles Reg I and Reg IX crossing the Nyurol’kamegabasin and Koltogory mesotrough, which complicate theKoltogory–Nyurol’ka megatrench. The profile Reg I runs fromnorth to south up to the eastern framing of the West Siberiangeosyneclise, and the profile Reg IX runs from northwest tosoutheast.

Analysis of these materials confirms the earlier statements:1. The thickness of the regional post-Turonian (first of all,

Cenozoic) deposits decreases east- and southeastward, i.e., the

regional axial part of the West Siberian Basin submergesrelative to the plate framing. That is why in the modernstructural plans of Jurassic and Cretaceous horizons, thePudino mesouplift lies hypsometrically much higher than theKaimysov dome, and the Aleksandrovskoe dome, higher thanthe Nizhnevartovsk one (Fig. 4).

2. The Jurassic and Cretaceous stratigraphic units lackedlarge tectonic structures up to the accumulation of the TalitsaFormation. Large positive structures such as the Nizhnevar-tovsk, Aleksandrovskoe, and Kaimysov domes and Pudinomesoarch appeared as a result of the formation of theKoltogory–Urengoi suprarift megatrench (including the Nyu-rol’ka megabasin and Koltogory mesotrough) as late as theCenozoic.

In northern regions of West Siberia, e.g., in the Nadym–Purpetroliferous area, where the Koltogory–Urengoi megatrenchis significantly wider, positive tectonic structures are rathersmall and of distinct linear shape—the ratio of the axis lengthsis not 1 : 3 (which is sufficient to recognize linear structures)

Fig. 4. Paleosections leveled along the upper boundary of the Koshai member (al, Alym Formation, Lower Cretaceous, Aptian) (a), Kuznetsov Formation (kz) (UpperCretaceous, Turonian) (b), and Talitsa Formation (tl) (Early Paleocene, Danian) (c) and modern section (d) along regional profiles IX and I; bg, Bazhenovo Formation.


but reaches 1 : 10. Almost all rather large positive structuresare localized in the zone of the Koltogory–Urengoi graben-rift,are oriented parallel to its axis, and formed mainly in theCenozoic. At that stage, the Etypur, Vungapur, and CentralUrengoi mesoarches, Chasel’ka megaarch, Northern dome,etc. formed.

The above fact is confirmed by Fig. 5 showing a moderndepth section and paleosections along W–E-striking regionalprofile 23 in the Yamal-Nenets Autonomous District. Thesections indicate that the suprarift depression zone (MiddlePur megabasin) and the largest regional positive structure(Northern dome) (both are reflected in the Volgian paleoreliefof the pre-Jurassic basement) were lacking in the relief of theBazhenovo Formation and Cretaceous horizons up to the endof the Turonian. These tectonic structures acquired theirmodern appearance as late as the Cenozoic. The time section(Fig. 2) shows that the Arctic structures bearing the Kruzen-shtern and Bovanenkovo petroleum fields formed at the sametime. The Leningrad field in the Kara Sea is also localized ina Cenozoic faulted structure.

Note that owing to the formation of a suprarift depression(Koltogory–Urengoi megatrench) in the Cenozoic, the mostsubsided part of the modern West Siberian Basin, which waslocalized in the cis-Uralian zone in the Neocomian, againshifted into the center of the basin.

The Cenozoic formation of the Koltogory–Urengoi mega-trench was accompanied by active faulting. Disjunctions cutalmost the entire Meso-Cenozoic sedimentary cover. At thattime, high-amplitude disjunctions of N–NE strike appeared at

the edges of the suprarift depression and on the slopes ofadjacent positive structures. They formed a regional system offaults extending for hundreds of kilometers from the MiddleVasyugan megabar and Kaimysov dome in the south to theMessoyakha ridge and farther northward.

To sum it up, the formation of oil and gas traps and,correspondingly, the petroleum potential of the West SiberianBasin took place mainly at the Berriassian–Aptian and,particularly, post-Turonian stages of its evolution.

In the Berriassian–Aptian, local domes (main oil traps)formed in Jurassic (first of all, Upper Jurassic) and Neocomianstructures in the southern and central parts of the basin.

At the post-Turonian stage, the largest Koltogory–Urengoidepression formed, which is the main seat of hydrocarbon(HC) generation and large positive structures, the main zonesof HC accumulation. In the basin north, most of the modernHC traps appeared. It is in the Cenozoic that the BazhenovoFormation, the main source of hydrocarbons in West Siberia,became part of the main petroleum accumulation zone, andthe coefficient of HC migration reached its maximum (Kon-torovich et al., 1975). This proves that it is the post-Turonianstage that mainly determined the formation of the unique WestSiberian PP.

Disjunctive tectonics and petroleum potential

The formation of disjunctions was directly related to theintensity of tectonic processes at different stages of the

Fig. 5. Modern depth section and paleosections leveled along the upper boundary of the Kuznetsov Formation (Turonian) (a) and Koshai member (Aptian) (b) andalong regional profile 23 (Yamal-Nenets Autonomous District) (c).


regional evolution. The length and characteristics (shift,displacement, amplitude, etc.) of faults are determined mainlyby the sizes of blocks undergoing tectonic processes andmovements.

Analysis of Meso-Cenozoic tectonic processes showedthree main stages of tectonic activity accompanied by theformation of disjunctions: Early Jurassic, Berriassian–Valang-inian, and post-Turonian (Cenozoic). These disjunctions per-mit the recognition of the main classes of faults penetratinginto: (1) Jurassic deposits (Hettangian–Aalenian faulting); (2)Lower Cretaceous horizons (Berriassian–Valanginian fault-ing); (3) Cenozoic deposits (Late Paleocene faulting).

Faults penetrating into Jurassic deposits. As notedduring analysis of Jurassic tectonic processes, Paleozoicmonolithic erosional-tectonic inliers tended to grow in theEarly Jurassic and Aalenian. This process was accompaniedby the formation and renewal of their faults.

Mapping of disjunctions in Paleozoic blocks composed ofrocks of different compositions and ages is of paramountimportance for constructing models of HC pools and discov-ering petroleum-promising objects in the petroliferous horizonof the zone of contact of Paleozoic and Mesozoic deposits.Figure 3 shows a fragment of time section along the profilecrossing the Gerasimovka petroleum field, where an HC poolis localized in Carboniferous disintegrated clay-siliceousrocks.

Jurassic faults not related to erosional-tectonic inliers arealso widespread in West Siberia. Since the most active Jurassictectonic processes took place in the Hettangian–Aalenian,these faults usually die out in the basal part of the sedimentarycover and seldom penetrate into the Bajocian and overlyingdeposits.

In the context of petroleum potential, mapping of thesefaults is of interest mainly for revealing incised valleys—linear depression zones in graben-like troughs, which mighthave been the basements of paleorivers in the Early Jurassic.A classical example of such objects is the Talaya petroliferouszone in the Krasnoleninsk arch.

Figure 6 shows a time section along the profile crossingthe Novonadezhdinsk incision, in which the Lower Jurassicand Aalenian deposits might be petroliferous.

It is obvious that Early Jurassic and Aalenian faults couldnot have influenced the formation of HC pools in UpperJurassic, Neocomian, and Aptian–Albian–Cenomanian depos-its bearing the main petroleum resources of West Siberia.

Faults penetrating into the Neocomian and Cenozoic. Inthe West Siberian PP, most of HC pools are localized in UpperJurassic (in the south) and Cretaceous deposits. Geochemicalstudies of hydrocarbons, in particular, the research into the oilsource rocks–oil relationship (Kontorovich et al., 1999) carriedout at the Trofimuk Institute of Petroleum Geology andGeophysics in the recent decade, showed that more than 80%of the West Siberian petroleum resources are geneticallyrelated to the siliceous-clayey rocks of the Bazhenovo Forma-tion.

In most part of West Siberia, the Bazhenovo Formationdeposits are overlain by thick shales serving as a reliable seal

preventing hydrocarbons from migration from oil source rocksinto Cretaceous sand horizons. This suggests that it isdisjunctions that might have been migration channels. Notethat Gurari et al. (1966) put forward a similar hypothesis.

Berriassian–Aptian faults might have formed at the stagewhen the Bazhenovo Formation, the main generator ofhydrocarbons, was localized at relatively small depths. By thetime when oil source rocks became part of the main petroleumformation zone, these faults had probably been healed andcould not serve as migration channels. At the same time,Berriassian–Aptian faults often serve as tectonic screens forUpper Jurassic HC pools.

Such a case is observed, e.g., in the south of the Kaimysovdome, where many HC pools are localized in tectonicallyscreened traps. Figure 7 shows an amplitude-filtered timesection along the profile crossing the Pavlovsk structural-tec-tonic trap hosting an oil pool of the Horizon J1 of theVasyugan Formation.

The formation of Cenozoic faults took place when oilsource rocks were in the main petroleum formation zone andthe coefficient of HC migration reached its maximum (Kon-

Fig. 6. The Novonadezhdinsk incision.

Fig. 7. Fragment of time section along profile 910466. The Pavlovsk structure-tectonic trap.


torovich et al., 1975). Probably, it is these faults that servedas channels for HC migration from the Bazhenovo Formationinto overlying Cretaceous horizons.

The distribution pattern of open petroleum pools in WestSiberia suggests that most of Cretaceous petroleum fields arelocalized in the central and northern parts of the Koltogory–Urengoi megatrench, which underwent extremely active ver-tical tectonic movements in the Cenozoic.

The above hypothesis is corroborated by the fact that theoverwhelming majority of HC pools in the Neocomian andAptian–Albian–Cenomanian deposits are stratified.

As mentioned above, the sedimentary megacomplexes towhich the main West Siberian petroleum accumulations areconfined become progressively younger in passing from southto north. In the south of the West Siberian Basin, in the Tomskand Novosibirsk Regions, Jurassic (first of all, Upper Jurassic)deposits seem to be the most petroliferous. In the center ofWest Siberia, in the Khanty-Mansi Autonomous District, mostpetroleum-promising megacomplex is the Neocomian,whereas in the northern and Arctic regions of the province,the Aptian–Albian–Cenomanian.

The results of these studies suggest that this distribution ofpetroleum pools is related mainly to the intensity of theformation of Cenozoic faults.

In southern West Siberia, in the zone where the Koltogory–Urengoi megatrench is the narrowest and formed least ac-tively, the Jurassic deposits have the highest petroleumpotential. The scarce Neocomian petroleum pools of thisregion are confined to suprarift depressions and are compli-cated by faults cutting Jurassic and Cretaceous deposits. Figure8 shows a time section crossing the South Aleksandrovskoestructure in the western part of the Aleksandrovskoe dome, inthe zone of its junction with the Koltogory mesotrough. Thefaults penetrating into Cenozoic deposits justified the deepdrilling in this area to search for HC pools in the Neocomiandeposits. In 2005, a prospecting borehole revealed the Danen-berg stratified petroleum field.

In general, the southern regions of West Siberia show adifferent pattern. The time section presented in Fig. 9 crossesthe Igol’skoe–Talaya petroleum field (one of the largest fieldsin the southeast of the basin), in which an HC pool isconcentrated in the Upper Jurassic deposits of the horizon J1.The section shows that the Upper Jurassic trap, which formedno later than the Valanginian, is not complicated by faults,and the behavior of Cretaceous and Cenozoic reflectinghorizons evidences an extremely low tectonic activity in thisarea in post-Valanginian time.

In the near-Ob’ and northern regions of West Siberia, whereCenozoic faulting was much more active, HC pools arelocalized mainly in Neocomian and Aptian–Albian–Cenoma-nian deposits and are differentiated by both complexes andtypes of fluids.

Figure 10 shows time sections crossing the Samotlorpetroleum field in the Khanty-Mansi Autonomous District andthe Urengoi and South Russian fields in the Yamal-NenetsAutonomous District.

The time section running across the Samotlor field unam-biguously shows faults cutting almost the entire sedimentarycover. The most uplifted part of the field, recognized in therelief of the reflecting horizon M in the Koshai member ofthe Alym Formation, corresponds to the depression zone inthe structural plan of the Jurassic roof (reflecting horizon B).This indicates that the uplift is not inherited but resulted fromyoung tectonic processes.

The time sections crossing the Urengoi and South Russianpetroleum fields evidence that the amplitudes of these upliftssignificantly increase upsection. The most contrasting upliftsare recognized in the structural plan of the reflecting horizon Gof the Kuznetsov Formation. The latter initially resembled aleveling surface, which indicates that both the Urengoi andthe South Russian structures resulted from post-Turoniantectonic processes. The wave fields of these structures alsounambiguously testify to their disturbance by abundant Ceno-zoic faults.

Conclusions

The relationship between the petroleum potential of theWest Siberian province and Mesozoic to Cenozoic tectonicprocesses was analyzed. The studies were based on structuraland isopach maps of seismogeologic megacomplexes com-

Fig. 8. Time section along profile A040114 (Danenberg multistratal petroleumfield in Neocomian sediments).


piled from generalized geological and geophysical data on theprovince at the Trofimuk Institute of Petroleum Geology andGeophysics as well as on the results of interpretation ofregional seismic CDP profiles.

The main stages of formation of structures of differentranks and faults and the fault depths have been established.

It is shown that the petroleum potential of the province isdetermined mainly by its structure and tectonic processes at

Fig. 9. Seismic profile of the Igol’skaya–Talaya petroleum field (A) and its fragment (B) (horizon J1 of the Vasyugan Formation, Upper Jurassic, Oxfordian).


the Cenozoic stage of evolution thanks to unique combinationof geological such as:

– formation of the Koltogory–Urengoi megatrench, themain zone of hydrocarbon generation, and large positivestructures—petroleum accumulation zones;

– submergence of the Bazhenovo Formation, the mainsource of hydrocarbons in the basin, which then migrated togreat depths in the main petroleum accumulation zone;

– origin of faults, which served as channels for hydrocarbonmigration from the oil source rocks of the Bazhenovo

Fig. 10. Seismic profile of the Samotlor (A), Urengoi (B), and South Russian (C) petroleum fields. 1. Reflecting seismic horizons. 2. Faults. 3. Hydrocarbon pools.


Formation to the main Neocomian and Aptian–Albian–Ceno-manian petroleum reservoirs of the province.

References

Gurari, F.G., Kontorovich, A.E., Ostryi, G.B., 1966. The role of disjunctionsin the formation of petroleum pools in the Jurassic and Cretaceous depositsof the West Siberian Lowland. Geologiya Nefti i Gaza, No. 2, 5–11.

Karogodin, Yu.N., 1974. The Rhythmic Character of Sedimentation andPetroleum Potential [in Russian]. Nedra, Moscow.

Kontorovich, A.E., Nesterov, I.I., Salmanov, F.K., Surkov, V.S., Tro-fimuk, A.A., Erv’e, Yu.G., 1975. Geology of West Siberian Oil and Gas[in Russian]. Nedra, Moscow.

Kontorovich, A.E., Fotiadi, E.E., Demin, V.I., Leontovich, V.B., Ras-tigin, A.A., 1981. Prediction for Petroleum Fields [in Russian]. Nedra,Moscow.

Kontorovich, A.E., Danilova, V.P., Kostyreva, E.A., Melenevskii, V.N.,

Moskvin, V.I., Fomin, A.N., Makhneva, E.N., 1999. Oil source formations

in West Siberia: old and new visions of the problem, in: Organic

Geochemistry of West Siberian Oil Source Rocks [in Russian]. Izd. SO

RAN, Novosibirsk, pp. 10–12.Kontorovich, V.A., 1999. The Jurassic tectonic evolution of the southeastern

regions of West Siberia. Geologiya Nefti i Gaza, Nos. 1–2, 7–16.Kontorovich, V.A., Belyaev, S.Yu., Kontorovich, A.E., Krasavchikov, V.O.,

Kontorovich, A.A., Suprunenko, O.I., 2001. Tectonic structure and

evolution of the West Siberian geosyneclise in the Mesozoic and Cenozoic.

Geologiya i Geofizika (Russian Geology and Geophysics) 42 (11–12),

1832–1845 (1740–1753).Kontorovich, V.A., Belyaev, S.Yu., Kontorovich, A.E., 2004. Criteria for the

classification of platform structures, in: Geology, Geophysics, and Exploi-

tation of Petroleum Fields [in Russian]. VNIIOENG, Moscow, pp. 47–58.


the meso-cenozoic tectonics and petroleum potential of ...acr/migrated/beringresources/articles...

Documents