basic geology for oil exploration
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Geoscience Training Center
Cefoga
Basic Geologyfor Oil
Exploration
Basic Geologyfor Oil
Exploration
Geoscience Training Center
Cefoga
GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummarySummary
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CefogaEarth componentsEarth components
Atmosphere
Crust
Mantle
Core
Inner Core
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CefogaEarth crust componentsEarth crust components
46,6
27,72
8,135 3,63 2,83 2,59 2,09 1,41
05
10152025
3035404550
O Si Al Fe Ca Na K Mg Other
%
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CefogaRock- mineral componentsRock- mineral components
Silica (SiO2)
Quartz
Silicates (SiO4 + Al, Ca, Na, K, Mg …)
Feldspars
Amphiboles and pyroxenes
Micas
SILICA AND SILICATES
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Calcium Sulphate (Anhydrite, Gypsum)
Chlorides (Halite, Sylvite)
EVAPORITE MINERALS
Sulphides, Oxides, phosphates …OTHERS
Calcite (CaCO3)
Dolomites (Mg, Ca(CO3)2 )
CARBONATES
Rock- mineral conponentsRock- mineral conponents
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CefogaEarth crust rocksEarth crust rocks
MAGMATIC ROCKS
Formed by cooling and crystallization of magma
MAGMATIC ROCKS
Formed by cooling and crystallization of magma
SEDIMENTARY ROCKS
Formed in surface by mechanical, chemical or biochemical processes, then buried at moderate depth
SEDIMENTARY ROCKS
Formed in surface by mechanical, chemical or biochemical processes, then buried at moderate depth
METAMORPHIC ROCKS
Formed by transformation of magmatic or sedimentary rocks
METAMORPHIC ROCKS
Formed by transformation of magmatic or sedimentary rocks
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CefogaRock cycleRock cycle
MAGMATIC ROCKS
METAMORPHIC ROCKS
SEDIMENTARY ROCKS
Fusion
Erosion
Magma
Cooling and crystallization
SolidTransformation
SEDIMENTS
Diagenesis
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CefogaRocks and hydrocarbonRocks and hydrocarbon
Sedimentary rocks are the only family of rocks where hydrocarbons can occur
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CefogaLithologyLithology
Standard reprensatation of rock faciès
SandstoneLimestone
Clay, Shale
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GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummary
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CefogaSedimentary Rocks
Characteristics
Sedimentary Rocks
CharacteristicsGRAINS
Mineralogy, Granulometry, Sorting, Morphology
MATRIXBinder (contemporaneous with sedimentation)Cement (secondary binding material), Mineralogy
PORES (Void space)Porosity (percentage of void volum), type of porosityEffective porosity (interconnected voids)Permeability (ability to led a fluid circulate)
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CefogaSedimentary Rocks
Classification
Sedimentary Rocks
Classification
CLASTIC (sandstone)
CARBONATE (limestones, dolomite)
EVAPORITES (salt)
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CefogaClastic Rocks Clastic Rocks
Grain size
Lutites Arenites RuditesSands
Very Fine
Fine
Medium
Coarse
Very Coarse
Granules
Gravel
PebblesClay Silt
Mudstone Siltstone Sandstone Conglomerats
Loos
eCo
nsod
ilated
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CefogaClastic Rocks formation Clastic Rocks formation
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CefogaCarbonates RocksCarbonates Rocks
J. Guillemot 1988
Limestone Dunham’s Classification
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CefogaCarbonates Rocks formationCarbonates Rocks formation
Chemical precipitation or Biochemical formation
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CefogaEvaporites RocksEvaporites Rocks
Conti
nenta
lCo
astal
Suba
queo
us
Sulfate Salt
Continental sebkha
Coastal sebkha
Crystalline, laminated,Turbidites
Displacive Halite
Chevron Halite
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CefogaEvaporites Rocks formationEvaporites Rocks formation
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CefogaSediment diagenesisSediment diagenesis
Sediments
(loose)
Sedimentary Rocks
(Consolidated)
Pressure, Temperature
Water circulation, biological factors
Ex : Sand Sandstones
Progressive transformation
Consequence of burial (subsidence)
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CefogaMargin typesMargin types
Geological Society of America
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CefogaMargin typesMargin types
M. T. Halbouty in AAPG mem. 40, 1986
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CefogaSedimentary Bassin exempleSedimentary Bassin exemple
A. Perrodon and J. Zabeck, 1990
Paris Bassin
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GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummary
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CefogaSource Rock - DefinitionSource Rock - Definition
Rock Containing a few pourcentage of organic matter which eventually be transformed in hydrocarbon
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CefogaKerogen typesKerogen types
TYPE I :
TYPE II :
TYPE III :
From lacustrine algae
From marine zoo or phyto plancton
From continental plants
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DiagenesisRo = 0.5%
Ro = 2.0%
Catagenesis60° to 120°2 to 4 km
depth
Metagenesis
KK44
KK33
KK22
KK11
KK
KK
Oil Phase-Out
OilOil GasGas
OilOil GasGas
OilOil GasGas
ConCon GasGas
GasGas
Hydrogen rates
KerogenOnset of Oil Generation
Horsfield and Rullkotter, 1994
Burial to Greater and
Hotter Depths
Source Rocks- MaturationSource Rocks- Maturation
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During burial, Temperatures and pressures rise. Chemical reactions generates the liquid and gas hydrocarbons found in the source rocks
Catagenesis / MetagenesisCatagenesis / Metagenesis
CATAGENESIS = generation of oil = OIL WINDOW
METAGENESIS = generation of gas = GAS WINDOW
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Organic-richSource Rock
Thermally MaturedOrganic Matter Oil
The Origin of PetroleumThe Origin of Petroleum
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GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummary
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A rock in which oil and gas accumulates
Two main types :- clastic rocks- carbonate rocks
Reservoir rocks - DefinitionReservoir rocks - Definition
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Porosity : space between rock grains in which oil accumulates
Permeability : passage-ways between pores through which oil and gas moves
Saturation : ratio of fluid volume by pore volume
Porosity : space between rock grains in which oil accumulates
Permeability : passage-ways between pores through which oil and gas moves
Saturation : ratio of fluid volume by pore volume
Reservoir rocks - characteristicsReservoir rocks - characteristics
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Good Porosity = Lots of Space for Petroleum
Pores(blue)
Porosity influencePorosity influence
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Pore-Filling Cement Reduces Quality
= Less Space for Petroleum
Cement(pink)
Cement influenceCement influence
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A rock through which oil and gas cannot move effectively (Non-permeable rocks)
Most common lithologies :
Shales
Saline rocks
Possibly very compact sandstone or limestone (with no porosity)
Seal rocks - DefinitionSeal rocks - Definition
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GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummary
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CefogaSecondary MigrationSecondary Migration
hydrocarbons move through a permeable rocks toward the earth’surface
= SECONDARY MIGRATION
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CefogaMigration and trappingMigration and trapping
Migrating hydrocarbons may encounter an impermeable layer before reaching earth’surface
= TRAPPING (Accumulation)
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Structure visible at the surface Seepage
Structural Traps Stratigraphic Traps
+ + + ++ + + +
Crystalline basement of substratum of the sedimentary sequence
1 Anticlinal
1
11
2 Horst
2
3 Flank if salt or shale dome
3
33
33
6 Erosional pinch-out
66
7 Lens (sand or sandstone)
7
4 Trap against fault
4
5 Sedimentary pinch-out
5
8 Reef
8
TrapsTraps
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American Petroleum Institute, 1986
Salt DomeFault
Unconformity
Pinchout
Anticline
Hydrocarbon Trap examplesHydrocarbon Trap examples
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2480
120° F120° F
350° F350° FGenerationGeneration
MigrationMigration
Seal RockSeal Rock
ReservoirRockReservoirRock
OilOil
WaterWater
Gas CapGas Cap
EntrapmentEntrapmentAccumulationAccumulation
Source Rock
Source Rock
SynthesisSynthesis
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• Largest North American field • More than 8 billion barrels recoverable• Largest North American field • More than 8 billion barrels recoverable
Barrow Arch
Barrow Arch
Sea LevelSea Level
10,00010,000
20,00020,000
30,00030,000
Brooks Range
Beaufort Sea
SealReservoirReservoir
KitchenKitchen
Anticlinal TrapAnticlinal Trap
120°F
unconformityunconformity
SouthSouth NorthNorth
American Association of Petroleum Geologists, 1990
Prudhoe Bay Oil Field (1968)Prudhoe Bay Oil Field (1968)
Anticlinal/Unconformity Combination Trap
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•Largest “lower-48” field•More than 5 billion barrels recoverable•Largest “lower-48” field•More than 5 billion barrels recoverable
Sea LevelSea Level1,0001,000
2,0002,0003,0003,000
120°F
Seal
ReservoirReservoir
KitchenKitchen
Unconformity TrapUnconformity Trap
unconformityunconformity
WestWest EastEast
Seal
American Association of Petroleum Geologists, 1990
East Texas Oil Field (1930)East Texas Oil Field (1930)
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CefogaIn Situ PhasesIn Situ Phases
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CefogaConclusionConclusion
CONDITION FOR HC ACCUMULATION
Presence of a source rock which must be mature
Presence of reservoir rocks
Presence of seals
Presence of traps
Adequate timing between trap formation and Hydrocarbons generation and formationAdequate timing between trap formation and Hydrocarbons generation and formation
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GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM
SummarySummary
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CefogaPetroleum system - descriptionPetroleum system - description
Source Rock (+ organic matter)
Maturation (burial)
+
=
Generating Sub-system
Reservoir Seal
Trap
+
=
Trapping Sub-system
Migration
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CefogaPetroleum system - timingPetroleum system - timing
Depth
(z)
TemperatureT0
T = T0 + g.z
DiagenesisCatagenesis
Metagenesis
Dry Gas Zone
1 - Primary Migration 2 - Secondary Migration 3 - Dismigration
Immature Zone
Oil Zone
Wet Gas Zone
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TeapotOwens
Pod of ActiveSource Rock
Just
Big Oil
Hardy Lucky
Immature Source Rock
Raven
Marginal
250 Ma
A A’
Critical MomentCritical Moment
Magoon and Dow, 1994
Rese
rvoir
Roc
k
David
Deer-Boar Petroleum SystemDeer-Boar Petroleum System
Zero Edge ofReservoir
Rock
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OverburdenSealReservoirSource
STRATIGRAPHICEXTENT OF
PETROLEUM SYSTEM
Trap Trap
Essential elements of petroleum
systemPOD OF ACTIVE SOURCE ROCK
Basement
Underburden Sedi
men
tary
basi
n-fil
l
GEOGRAPHIC EXTENT OF PETROLEUM SYSTEM250 MaTrap
Petroleum accumulationTop of oil windowBottom of oil windowLocation for burial history chart
A A’
Magoon and Dow, 1994
Critical Moment = Time of Expulsion/MigrationCritical Moment = Time of Expulsion/Migration
Petroleum System at Critical MomentPetroleum System at Critical Moment
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Basement
GEOGRAPHIC EXTENT OF PETROLEUM SYSTEM Present-Day
STRATIGRAPHICEXTENT OF
PETROLEUM SYSTEM
Petroleum accumulationTop of oil windowBottom of oil window
Trap TrapTrap
SealReservoirSourceUnderburden
Overburden
A A’
Magoon and Dow, 1994
Present-Day Petroleum SystemPresent-Day Petroleum System
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400 300 200 100
Paleozoic Mesozoic Cen.
P NKJTPMD P Lith
olog
y
RockUnit
Dep
th (K
m)
Sour
ceR
eser
voir
Seal
Ove
rbur
den
1
2
3
Placer FmGeorge Sh
Boar Ss
Deer ShElk Fm
Top gas window
Critical MomentCritical Moment
ThickFm
R
Magoon and Dow, 1994
GenerationGeneration
Time of Expulsion and Migration. (Trap must already exist)
Top oil window
Burial History ChartBurial History Chart
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Magoon and Dow, 1994
Inventory of AccumulationsInventory of Accumulations
FieldName
Datediscovered
Reservoirrock
APIGravity( API)
Cumulative oil production(x10 bbl)
Remainingreserves
(x10 bbl)
HardyLuckyMarginalTeapot
1989199019901992
Boar SsBoar SsBoar SsBoar Ss
29151821
855129
Big oilRavenOwensJust
1954195619591966
Boar SsBoar SsBoar SsBoar Ss
32313334
310120110160
9012193689706534
o 6 6
Deer-Boar Petroleum SystemDeerDeer--Boar Petroleum SystemBoar Petroleum System
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1 2
400 300 200 100
Paleozoic Mesozoic Cenozoic
D M P P TR J K Pε N
Geologic Time-Scale
Petroleum System Events
Source RockReservoir RockSeal RockOverburdenTrap FormationGeneration, Migration,and Accumulation
PreservationCritical Moment1. Western North Slope
2. East-central North Slope
Bird, 1994
North Slope, Alaska
Petroleum System Events ChartPetroleum System Events Chart
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Spill PointSpill PointSpill PointSpill Point
Seal RockSeal Rock(Mudstone)(Mudstone)Reservoir RockReservoir Rock
(Sandstone)(Sandstone)Migration fromMigration from‘Kitchen’‘Kitchen’
1) Early Generation
2) Late Generation
Gas displaces all Gas displaces all oiloil
Gas beginning to Gas beginning to displace oildisplace oil
Displaced oil Displaced oil accumulatesaccumulates
Petroleum SystemPetroleum SystemPetroleum System
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