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7/30/2019 geology of petroluem systems
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Geology ofPetroleum Systems
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Petroleum Geology
Objectives are to be able to:
Discuss basic elements of Petroleum Systems
Describe plate tectonics and sedimentary basins
Recognize names of major sedimentary rock types
Describe importance of sedimentary environmentsto petroleum industry
Describe the origin of petroleum
Identify hydrocarbon trap types
Define and describe the important geologiccontrols on reservoir properties, porosity andpermeability
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Outline
Petroleum Systems approach
Geologic Principles and geologic time
Rock and minerals, rock cycle, reservoir
properties Hydrocarbon origin, migration and
accumulation
Sedimentary environments and facies;stratigraphic traps
Plate tectonics, basin development, structuralgeology
Structural traps
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Petroleum System - A Definition
A Petroleum System is a dynamic hydrocarbonsystem that functions in a restricted geologicspace and time scale.
A Petroleum System requires timely
convergence of geologic events essential tothe formation of petroleum deposits.
These Include:
Mature source rock
Hydrocarbon expulsionHydrocarbon migrationHydrocarbon accumulationHydrocarbon retention
(modified from Demaison and Huizinga, 1994)
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Cross Section Of A Petroleum System
Overburden Rock
Seal Rock
Reservoir Rock
Source Rock
Underburden Rock
Basement Rock
Top Oil Window
Top Gas Window
Geographic Extent of Petroleum System
Petroleum Reservoir (O)
Fold-and-Thrust Belt
(arrows indicate relative fault motion)
Essential
Elements
of
Petroleum
System
(Foreland Basin Example)
(modified from Magoon and Dow, 1994)
O O
Sed
imentary
BasinFill
O
Stratigraphic
Extent ofPetroleum
System
Pod of Active
Source Rock
Extent of Prospect/FieldExtent of Play
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Basic Geologic Principles
Uniformitarianism
Original Horizontality
Superposition Cross-Cutting Relationships
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Cross-Cutting Relationships
Angular Unconformity
A
B
C
D
E
F
G
HIJ
K
IgneousDike
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Disconformity An unconformity in which the beds above and below
are parallel
Angular Unconformity An unconformity in which the older bed intersect the
younger beds at an angle
Nonconformity An unconformity in which younger sedimentary
rocks overlie older metamorphic or intrusiveigneous rocks
Types of Unconformities
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Correlation
Establishes the age equivalence of rocklayers in different areas
Methods:
Similar lithology
Similar stratigraphic section
Index fossils
Fossil assemblages Radioactive age dating
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0
50
100
150
200
250
300
350
400
450
500
550
600
0
10
20
30
40
50
60
Cryptozoic
(Precambrian)
Phanerozoic
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Pennsylvanian
Mississippian
Devonian
Silurian
Ordovician
Cambrian
Millionsofyearsago
Millions
ofyearsago
Billions
ofyearsago
0
1
2
3
4
4.6
Paleocene
Eocene
Oligocene
Miocene
Pliocene
PleistoceneRecent
Quate
rnary
period
Tertiary
period
Eon Era Period Epoch
Geologic Time Chart
Paleo
zoic
Mesozoic
Ce
nozoicEra
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Rocks
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Classification of Rocks
SEDIMENTARY
Rock-forming
process
Sourceof
material
IGNEOUS METAMORPHIC
Molten materials indeep crust andupper mantle
Crystallization(Solidification of melt)
Weathering anderosion of rocks
exposed at surface
Sedimentation, burialand lithification
Rocks under hightemperatures
and pressures indeep crust
Recrystallization due toheat, pressure, or
chemically active fluids
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The Rock Cycle
Magma
Metamorphic
Rock
SedimentaryRock
Igneous
Rock
Sediment
Heat and Pressure
Weathering,Transportationand Deposition
a
n
i
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Siltstone, mudand shale~75%
Sedimentary Rock Types
Relative abundanceSandstone
and conglomerate~11%
Limestone anddolomite
~13%
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Quartz Crystals
Naturally OccurringSolid
Generally Formed byInorganic Processes
Ordered InternalArrangement of Atoms(Crystal Structure)
Chemical Compositionand Physical PropertiesFixed or Vary WithinA Definite Range
Minerals - Definition
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Average Detrital Mineral
Composition of Shale and Sandstone
Mineral Composition Shale (%) Sandstone (%)
Clay Minerals
Quartz
Feldspar
Rock Fragments
Carbonate
Organic Matter,Hematite, andOther Minerals
60
30
4
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The Physical and Chemical Characteristics
of Minerals Strongly Influence theComposition of Sedimentary Rocks
Quartz
Feldspar
Calcite
Mechanically and Chemically Stable
Can Survive Transport and Burial
Nearly as Hard as Quartz, butCleavage Lessens Mechanical StabilityMay be Chemically Unstable in SomeClimates and During Burial
Mechanically Unstable During Transport
Chemically Unstable in Humid ClimatesBecause of Low Hardness, Cleavage, andReactivity With Weak Acid
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Some Common Minerals
Silicates
Oxides Sulfides Carbonates Sulfates Halides
Non-Ferromagnesian(Common in Sedimentary Rocks)
AnhydriteGypsum
HaliteSylvite
AragoniteCalciteDolomiteFe-DolomiteAnkerite
PyriteGalenaSphalerite
Ferromagnesian(not common in sedimentary rocks)
HematiteMagnetite
QuartzMuscovite (mica)Feldspars
Potassium feldspar (K-spar)OrthoclaseMicrocline, etc.
PlagioclaseAlbite (Na-rich - common) throughAnorthite (Ca-rich - not common)
OlivinePyroxene
AugiteAmphibole
HornblendeBiotite (mica)
Red = Sedimentary Rock-Forming Minerals
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The Four Major Components
Framework Sand (and Silt) Size Detrital Grains
Matrix
Clay Size Detrital Material
Cement
Material precipitated post-depositionally,
during burial. Cements fill pores and replaceframework grains
Pores
Voids between above components
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Norphlet Sandstone, Offshore Alabama, USA
Grains are About =< 0.25 mm in Diameter/Length
PRF KF
P
KF = PotassiumFeldspar
PRF = Plutonic RockFragment
P = Pore
Potassium Feldspar isStained Yellow With a
Chemical Dye
Pores are ImpregnatedWith Blue-Dyed Epoxy
CEMENT
Sandstone Composition
Framework Grains
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Scanning Electron MicrographNorphlet Formation, Offshore Alabama, USA
Pores Provide the
Volume to ContainHydrocarbon Fluids
Pore Throats RestrictFluid Flow
PoreThroat
Porosity in Sandstone
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Secondary Electron Micrograph
Jurassic Norphlet SandstoneHatters Pond Field, Alabama, USA (Photograph by R.L. Kugler)
Illite
SignificantPermeabilityReduction
NegligiblePorosityReduction
Migration ofFines Problem
High IrreducibleWater Saturation
Clay Minerals in Sandstone Reservoirs
Fibrous Authigenic Illite
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Secondary Electron Micrograph
Jurassic Norphlet Sandstone
Offshore Alabama, USA (Photograph by R.L. Kugler)
Occurs as ThinCoats on DetritalGrain Surfaces
Occurs in SeveralDeeply BuriedSandstones WithHigh ReservoirQuality
Iron-RichVarieties ReactWith Acid
~ 10m
Clay Minerals in Sandstone Reservoirs
Authigenic Chlorite
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Secondary Electron Micrograph
Carter SandstoneNorth Blowhorn Creek Oil Unit
Black Warrior Basin, Alabama, USA
Significant PermeabilityReduction
High Irreducible WaterSaturation
Migration of FinesProblem
(Photograph by R.L. Kugler)
Clay Minerals in Sandstone Reservoirs
Authigenic Kaolinite
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100
10
1
0.1
0.01 0.01
0.1
1
10
100
1000
2 6 10 14 2 6 10 14 18
Pe
rmeability(m
d)
Porosity (%)
Authigenic Illite Authigenic Chlorite
(modified from Kugler and McHugh, 1990)
Effects of Clays on Reservoir Quality
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Dispersed Clay
Clay Lamination
Structural Clay(Rock Fragments,
Rip-Up Clasts,Clay-Replaced Grains)
fe
fe
fe
ClayMinerals
Detrital QuartzGrains
Influence of Clay-Mineral
Distribution on Effective Porosity
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Diagenesis
CarbonateCemented
OilStained
Diagenesis is the Post-Depositional Chemical andMechanical Changes thatOccur in Sedimentary Rocks
Some Diagenetic Effects IncludeCompactionPrecipitation of CementDissolution of Framework
Grains and Cement
The Effects of Diagenesis MayEnhance or Degrade ReservoirQuality
Whole Core
Misoa Formation, Venezuela
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Fluids Affecting Diagenesis
Precipitation
Subsidence
CH4,CO2,H2S
Petroleum
Fluids
Meteoric
Water
MeteoricWater
COMPACTIONAL
WATER
EvapotranspirationEvaporation
Infiltration
Water Table
Zone of abnormal pressure
Isotherms
(modified from from Galloway and Hobday, 1983)
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Thin Section Micrograph - Plane Polarized Light
Avile Sandstone, Neuquen Basin, Argentina
Dissolution of
Framework Grains
(Feldspar, for
Example) and
Cement may
Enhance the
Interconnected
Pore System
This is CalledSecondary Porosity
Pore
Quartz Detrital
Grain
Partially
Dissolved
Feldspar
(Photomicrograph by R.L. Kugler)
Dissolution Porosity
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Hydrocarbon Generation,
Migration, and Accumulation
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Organic Matter in Sedimentary Rocks
Reflected-Light Micrograph
of Coal
Vitrinite
Kerogen
Disseminated Organic Matter inSedimentary Rocks That is Insolublein Oxidizing Acids, Bases, andOrganic Solvents.
VitriniteA nonfluorescent type of organic materialin petroleum source rocks derivedprimarily from woody material.
The reflectivity of vitrinite is one of the
best indicators of coal rank and thermalmaturity of petroleum source rock.
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Interpretation of Total Organic Carbon (TOC)
(based on early oil window maturity)HydrocarbonGenerationPotential
TOC in Shale(wt. %)
TOC in Carbonates(wt. %)
Poor
Fair
Good
Very Good
Excellent
0.0-0.5
0.5-1.0
1.0-2.0
2.0-5.0
>5.0
0.0-0.2
0.2-0.5
0.5-1.0
1.0-2.0
>2.0
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Schematic Representation of the Mechanism
of Petroleum Generation and Destruction
(modified from Tissot and Welte, 1984)
Organic Debris
Kerogen
Carbon
Initial Bitumen
Oil and Gas
Methane
Oil Reservoir
MigrationThermal Degradation
Cracking
Diagenesis
Catagenesis
MetagenesisProgre
ssiveBurialan
dHeating
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Incipient Oil Generation
Max. Oil Generated
Oil Floor
Wet Gas Floor
Dry Gas Floor
Max. Dry GasGenerated
(modified from Foster and Beaumont, 1991, after Dow and OConner, 1982)
VitriniteReflectance(Ro)%
Weight%
CarboninKero
gen
SporeColo
rationIndex(S
CI)
Pyr
olysisT
(C)
max
0.2
0.3
0.40.5
4.0
3.0
2.0
1.3
1
2
3
4
56
789
10
430
450
465
65
70
75
80
85
90
95
0.60.70.80.91.01.2
OIL
WetGas
DryGas
Comparison of Several Commonly Used
Maturity Techniques and Their Correlation
to Oil and Gas Generation Limits
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Reservoirrock
Seal
Migration route
Oil/watercontact (OWC)
Hydrocarbon
accumulationin thereservoir rock
Top of maturity
Source rock
Fault(impermeable)
Generation, Migration, and
Trapping of Hydrocarbons
C S ti Of A P t l S t
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Cross Section Of A Petroleum System
Overburden Rock
Seal Rock
Reservoir Rock
Source Rock
Underburden Rock
Basement Rock
Top Oil Window
Top Gas Window
Geographic Extent of Petroleum System
Petroleum Reservoir (O)
Fold-and-Thrust Belt
(arrows indicate relative fault motion)
Essential
Elements
of
Petroleum
System
(Foreland Basin Example)
(modified from Magoon and Dow, 1994)
O O
Sedimentary
B
asinFill
O
Stratigraphic
Extent ofPetroleum
System
Pod of Active
Source Rock
Extent of Prospect/FieldExtent of Play
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Hydrocarbon Traps
Structural traps
Stratigraphic traps
Combination traps
Structural Hydrocarbon Traps
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Structural Hydrocarbon Traps
Salt
Diapir
Oil/Water
Contact
GasOil/Gas
Contact
Oil
ClosureOilShale Trap
Fracture Basement
(modified from Bjorlykke, 1989)
Fold Trap
OilSalt
Dome
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Oil
Sandstone Shale
Hydrocarbon Traps - Dome
Gas
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Fault Trap
Oil / Gas
Stratigraphic Hydrocarbon Traps
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Oil/Gas
Oil/Gas
Oil/Gas
Stratigraphic Hydrocarbon Traps
Uncomformity
Channel Pinch Out
(modified from Bjorlykke, 1989)
Unconformity Pinch out
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AsphaltTrap
Water
Meteoric
Water
Biodegraded
Oil/Asphalt
Partly
Biodegraded Oil
Hydrodynamic Trap
Shale
Oil
Water
Hydrostatic
Head
(modified from Bjorlykke, 1989)
Other Traps
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Heterogeneity
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Reservoir Heterogeneity in Sandstone
Heterogeneity May
Result From:
Depositional Features
Diagenetic Features
(Whole Core Photograph, Misoa
Sandstone, Venezuela)
Heterogeneity
Segments Reservoirs
Increases Tortuosity of
Fluid Flow
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Reservoir Heterogeneity in Sandstone
Heterogeneity Also May
Result From:
Faults
Fractures
Faults and Fractures may
be Open (Conduits) or
Closed (Barriers) to Fluid
Flow
(Whole Core Photograph, Misoa
Sandstone, Venezuela)
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Bounding
Surface
Bounding
Surface
Eolian Sandstone, Entrada Formation, Utah, USA
Geologic Reservoir Heterogeneity
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Scales of Geological Reservoir Heterogeneity
FieldWide
Interwe
ll
Well-Bore
(modified from Weber, 1986)
Hand Lens orBinocular Microscope
Unaided Eye
Petrographic or
Scanning ElectronMicroscope
Determined
From Well Logs,Seismic Lines,StatisticalModeling,
etc.
10-100'sm
10-100'smm
1-10'sm
100'sm
10'sm
1-10 km
100's m
Well WellInterwellArea
ReservoirSandstone
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Scales of Investigation Used inReservoir Characterization
Gigascopic
Megascopic
Macroscopic
Microscopic
Well Test
Reservoir ModelGrid Cell
Wireline LogInterval
Core Plug
GeologicalThin Section
Relative Volume
1
1014
2 x 1012
3 x 107
5 x 102
300 m
50 m
300 m
5 m 150 m
2 m
1 m
cm
mm - m
(modified from Hurst, 1993)
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Stages In The Generation ofAn Integrated Geological Reservoir Model
Log AnalysisWell Test Analysis
Core Analysis
Regional GeologicFramework
DepositionalModel
DiageneticModel
IntegratedGeologic Model
Applications Studies
Model TestingAnd Revision
StructuralModel
FluidModel
(As Needed)
(As Needed)
Geologic Activities
Reserves EstimationSimulation