Download - Ench week02
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Week 2
Review of week 1o class project
o reserve reading
Tectonic setting of sedimentary basins
Basin analysis exampleo Gulf of Suez Rift Basin (Alsharhan, 2003; Lindquist, 1998)
Tectonic setting of sedimentary basins (continued)
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Review of week 1
Course objectives and scope
Petroleum geology and basin analysiso class project
Plate tectonics and basin formation
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Course Schedule and ContentClass Topic
Sept 14
Week 1
Introduction to Course and Material
Review and discussion of concepts
Sept 21
Week 2
Example of basin analysis: Gulf of Suez Rift Basin
Basins I: description of basins, plate tectonics, basin classification and
tectonic setting
Sept 28
Week 3
Basins II: basin classification (continued), basin models of subsidence
and sedimentation
Oct 5
Week 4
Basin Fill I: Stratigraphy and sedimentology; tools used, dating and
correlation
Oct 12
Week 5
Basin Fill II: Facies models, basin mapping; sequence s tratigraphy
Oct 19
Week 6
Basin Fill III: Sequence stratigraphy (continued), seismic stratigraphy
Oct 26
Week 7
Due Today: Selection of basin/petroleum system for main class
project
Basins III: Regional and global stratigraphic cycles
Nov 2
Week 8
Mid Term Exam (tentative)
Review selected basin example
Nov 9
Week 9
Petroleum System I: The petroleum system
Nov 16
Week 10
Student seminars
Petroleum System II: Field size distribution, play concepts
Nov 23
Week 11
Student seminars
Selected geologic topic: Carbonate models: basin fill and sequence
stratigraphy
Nov 30
Week 12
Student seminars
Carbonate models (continued): sequence stratigraphy, reservoir
development
Dec 7
Week 13
Student seminars
Basin modeling software demonstration
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What is Basin Analysis
Basin analysis involves making an interpretation of the formation, evolution, architecture and fill of a sedimentary basin by examining geological variables associated with the basin.
Basin analysis provides a foundation for extrapolating known information into unknown regions in order to predict the nature of the basin where evidence is not available.
A basin model is built on a framework of geological surfaces that are correlated within the basin. This stratigraphic framework can be expressed in terms of rock type (lithostratigraphy), fossil content (biostratigraphy), age (chronostratigraphy), or rock properties such as seismic velocity (seismic stratigraphy).
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(after Mial, 2000)Methods of
AnalysisGlobal Stratigraphic
Hierarchy
magnetic reversalsearthquake first
motions
deep seismicregional stratigraphy
biogeography
basin modelsbackstripping
geohistory analysis
radiometric datingpaleontology
sequence stratigraphy
seismic stratigraphyseismic facies
regional well datalithofacies analysis
paleocurrent analysis
sequence analysis
analysis of core or outcrop
sea floor spreading
plate positioneustatic sea level
plate and terrane interaction
plate margin typebasin generation
unconformity bounded stratigraphic sequences
depositional systems tracts
depositional systems
lithofacies assemblage
individual lithofaciessmall scale
large scale
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Geoscience Effort in Basin Analysis
Basin analysis for exploration can be described as the integration of the following 3 components
Controls on development of the sedimentary basinplate tectonic and paleogeographic history
Stratigraphy and sedimentology of the basinbasin fill
The petroleum systemsource, maturity, migration, trap, seal
Significant geoscience effort is required to prepare each of these components of the basin analysis; multidisciplinary approach
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Class project
Selection of basin/petroleum system for main class project by October 26
o select basin and petroleum system and have prepared references
o references required in standard format; AAPG
o only one student per basin/petroleum system; first come - first served
Integrate the 3 components of basin analysis for petroleum exploration through research of publicly available information (journals, books, government publications)
1. Controls on development of the sedimentary basin; plate tectonic and paleogeographic history
2. Stratigraphy and sedimentology of the basin; basin fill
3. The petroleum system; source, maturity, migration, trap, seal
Present paper to class according to schedule
Written paper due no later than Dec 14
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Class project continued
Source of information and references to begin:o USGS website
o summary spreadsheet provided by Dr. McNamara
Desktop/Basin Analysis/world hydrocarbon volumes.xls
Reserve reading: Gallagher library material
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Tectonic Basin Classification
(Einsele, 2000, Table 1.1)
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Plate Tectonic Model
(http://pubs.usgs.gov/publications/text/Vigil.html)
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Crustal Hotspots
(http://pubs.usgs.gov/publications/text/world_map.html)
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Basin types: example tectonic setting
(Einsele, 2000, Ch 1)
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Tectonics and Sediment Fill
(Einsele, 2000, Fig 1.5)
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Isostasy
The state of gravitational equilibrium between the
lithosphere and the asthenosphere of the Earth such
that lithospheric plates "float" at a given elevation
depending on their thickness. The balance between the
elevation of the lithospheric plates and the
asthenosphere is achieved by the flowage of the
denser asthenosphere.
(http://www.glossary.oilfield.slb.com)
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Case Study: Gulf of Suez Rift Basin
Alsharhan, A.S., 2003. Petroleum geology and potential
hydrocarbon plays in the Gulf of Suez rift basin, Egypt:
Am. Assoc. Petroleum Geol. Bull., v. 87, p. 143-180.
The 3 components of basin analysis
o tectonic and paleogeographic setting
o basin fill
o petroleum system
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Basin analysis by Alsharhan, A.S., 2003
Geographic setting
Lithostratigraphy
o Prerift, synrift, postrift
Tectonic development
o rifting and subsidence, deep troughs
Petroleum System
o heat flow
o maturation
o organic content
Hydrocarbon Traps
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Geography, Surface Geology, Oil Fields
Gulf of Suez
30 to 80 km wide
320 km long
40-60m water depth
240 discoveries
80 fields
1000 exploration wells
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Basin Analysis
The specific tools used in this basin analysiso Lithostratigraphic units
o stratigraphy: measured stratigraphic sections, subsurface cores, electric
logs
o age: electric logs tied to microfaunal and palynological studies of ditch
samples; pollen and spores used to date Paleozoic-L. Cret Nubian
sandstone
o plate tectonics
o eustatic sea level curves
o subsidence rates
o heat flow
o source rock maturity- TOC, Ro, Van Krevelen
What has not been included?
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Integrated Tectonics, Sedimentation, Sea Level
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Evolution of Gulf of Suez Basin: Paleozoic
Deposition of Paleozoic terrestrial clastics over Precambrian crystalline basement;
significant periods of uplift and unconformity
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Permian-Triassic (Prerift)
Local subsidence, minor transgression; fluvial and marine shales and sandstones
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Early Cretaceous (Synrift)
Rifting, graben system via block faulting, depressions filled with non-marine
sandstone and shale
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Middle Cretaceous to Miocene (Synrift)
Normal faulting, subsidence of graben system, marine incursion; marine sandstones
and limestones; capped by thick salt deposits
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Pliocene-Holocene (Postrift)
Basin margins uplifted, non-marine sand wedge fills marine basin area
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Note interbedded
source, reservoir and
seal lithologies
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Synrift Lithostratigraphic Units
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Geothermal Gradient and Hot Spot Areas
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Hydrocarbon Traps and Trapping Mechanism
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Total Organic Content (weight %)
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Source Areas and Migration Paths
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Traps and Seals
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Conclusion: Gulf of Suez Rift Basin
Integrated picture covering differing geoscience
disciplines
Simple basin geohistory, basin fill, petroleum system
covered
Missing: seismic facies, sequence stratigraphy, cross
sections, well logs, subsidence model, quantitative
backstripping
some of these may be covered in reference material
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(after Miall, 2000)Methods of
AnalysisGlobal Stratigraphic
Hierarchy
magnetic reversalsearthquake first
motions
deep seismicregional stratigraphy
biogeography
basin modelsbackstripping
geohistory analysis
radiometric datingpaleontology
sequence stratigraphy
seismic stratigraphyseismic facies
regional well datalithofacies analysis
paleocurrent analysis
sequence analysis
analysis of core or outcrop
sea floor spreading
plate positioneustatic sea level
plate and terrane interaction
plate margin typebasin generation
unconformity bounded stratigraphic sequences
depositional systems tracts
depositional systems
lithofacies assemblage
individual lithofaciessmall scale
large scale
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Tectonics: Principles, Models and Cycles
Basin modelso basin formation
o The “Wilson Cycle”
o classification system and examples
Tectonism and Sedimentationo components of basin models
o extensional basins
o supracrustal loading
o basement tectonics
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Basin Forming Processes
Crustal Stress Environmentso extensional (extensional basins)
o contractional (convergent, compressional basins)
o shear (pull-apart basins)
Extension:o heating of the lithosphere from below
o thinning of crust
o stretching of crust
Convergence:o local loading with accompanying subsidence due to stacking of thrust
slices/nappes
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Three Principal Stress Environments Under Which Sedimentary Basins Are Produced
(Miall, 2000, Fig 7.1)
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Plate Boundaries
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Thickness of Continental Crust From Seismic Velocity
(Allen and Allen, 1990, Fig 1.3)
(values in km/s); 8.1 km/s marks base of
crust)
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Mechanisms of Basin Subsidence
Thermal cooling and
subsidence
Changes in
crustal/lithospheric thickness:
thinning of crust followed by
faulting, subsidence
Loading to cause deflection or
flexural deformation
(Allen and Allen, 1990, Fig 1.12)
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The Wilson Cycle (handout)
The cycle of opening and closing of ocean basinso Oceanic crust cools as it ages, becoming more dense and
gravitationally unstable with respect to substratum – oceanic crust gets
consumed
References:o Wilson, J. T., 1966, Did the Atlantic close and then re-open?, Nature,
211(5050), 676-681
o Ancient Environments and the Interpretation of Geologic History, by
Lynn S. Fichter and David J. Poche, 3rd edition, 2001, Prentice Hall
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The “Wilson Cycle”
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Basin Models and Classification
There are 6 major basin typeso oceanic basins
o rifted continental margins
o arc-trench systems
o suture belts
o intracontinental basins
o strike-slip or transform related basins
These have been classified in different ways by
different authors.
Classification systemso Einsele (2000), Chapter 1
o Miall (2000), Chapter 9
o Allen and Allen (1990), Chapter 1
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Basin Models and Classification
Sedimentary basins classified in terms of 3 criteria:o 1. the type of crust on which the basin rests (continental, oceanic,
transitional)
o 2. the position of the basin relative to plate margins (within plate or
margin of plate)
o 3. where the basin lies close to a plate margin, the type of plate
interaction occurring during sedimentation (divergent, convergent,
transform)
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Basin Classification System (Einsele, 2000)
1 32
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Basin Category: Continental Interior
Continental or interior sag basins
Continental or interior fracture basins
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Continuum: Sags to Passive Margins
(Allen and Allen, 1990, Fig 3.31)
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Basin Category: Passive Margin, Oceanic Sag
Passive Margin
Oceanic Sag and Fault Bounded Basins
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Basin Category: Subduction Related
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Basin Category: Collision Related
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Strike-slip Basins
Strike-slip basins can occur:o oceanic and continental transforms
o continental extension undergoing rifting
o convergent plate boundaries of orogenic belts
Basins associated with strike-slip deformation are
generally small and complex compared to rifts,
passive margins and foreland basins.
Lateral movement takes place between adjacent
crustal or lithospheric blocks
Movement is rarely pure lateral; usually oblique
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Transform and Transcurrent Faults
transform fault: strike slip fault that is deep seated and
between plates (interplate); plate boundary fault
system linking other boundary types; boundary
parallel movement o examples: ocean ridge transform faults, plate boundary transform faults,
trench linked strike-slip faults
transcurrent fault: strike slip fault that is confined to
the crust and within a plate (intraplate) (Allen and
Allen, 1990, p 116)o examples: indent linked faults bounding continental blocks in collision
zone; intracontinental strike-slip faults separating terranes of differing
tectonic styles
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Classification of Strike-slip Faults
(Allen and Allen, 1990, Table 5.2)
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Strike-slip Faults
transcurrent fault
(Allen and Allen, 1990, Fig 5.2)
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Basin Category: Strike-slip
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Basin Classification System (Miall, Ch 9)
1. Divergent Margin Basins1. rift basins
2. ocean margin rises and terraces
3. aulacogens and failed rifts
2. Convergent Margin Basins1. trenches and subduction complexes
2. forearc, intra-arc, backarc, foreland, satellite basins
3. Transform and transcurrent-fault basins1. basins in braided fault systems (wrench complexes)
2. fault termination basins
3. pull apart basins
4. transrotational basins
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Basin Classification System (continued)
4. Basins developed during continental collision and
suturing1. peripheral basins on downgoing plate
2. remnant ocean basins
3. hinterland foreland, strike-slip and graben basins; intermontane basins
5. Intraplate basins1. cratonic basins floored by continental crust
2. oceanic islands, sea mounts, plateaus floored by oceanic crust
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Basin Classification (Kingston et al, 1983)
(Allen and Allen, 1990, Table 1.11)
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Use of Basin Classification Systems
Basin models represent prototypes of tectonically
controlled basins; every basin will differ from these
models
There are no type basins which can be used as a model for
any other basin
Within a single, broad tectonic setting the development of
basins will exhibit great variation
Over time, sedimentary basins evolve from one type to
another, further complicating sedimentary and tectonic
history
Tectonic classification of a basin may have no bearing on
petroleum potential of the basin
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Basin Classification: Summary
Reviewed common classification systems as presented
in Miall (2000), Einsele (2000) and Allen and Allen
(1990).
Sedimentary basins classified in terms of 3 criteria:o 1. the type of crust on which the basin rests (continental, oceanic,
transitional)
o 2. the position of the basin relative to plate margins (within plate or
margin of plate)
o 3. where the basin lies close to a plate margin, the type of plate
interaction occurring during sedimentation (divergent, convergent,
transform)
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1st and 2nd Order Cycles of Sea Level Change
(Vail et al, 1977)