Basic geology for Oil Exploration

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Cefoga

Basic Geologyfor Oil

Exploration

Basic Geologyfor Oil

Exploration


Cefoga

GENERALITIESSEDIMENTARY ROCKSSOURCE ROCKSRESERVOIRS AND SEALSHYDROCARBON TRAPS AND MIGRATIONPETROLEUM SYSTEM

SummarySummarySummary


CefogaEarth componentsEarth components

Atmosphere

Crust

Mantle

Core

Inner Core


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

%


CefogaRock- mineral componentsRock- mineral components

Silica (SiO2)

Quartz

Silicates (SiO4 + Al, Ca, Na, K, Mg …)

Feldspars

Amphiboles and pyroxenes

Micas

SILICA AND SILICATES


Cefoga

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


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


CefogaRock cycleRock cycle

MAGMATIC ROCKS

METAMORPHIC ROCKS

SEDIMENTARY ROCKS

Fusion

Erosion

Magma

Cooling and crystallization

SolidTransformation

SEDIMENTS

Diagenesis


CefogaRocks and hydrocarbonRocks and hydrocarbon

Sedimentary rocks are the only family of rocks where hydrocarbons can occur


CefogaLithologyLithology

Standard reprensatation of rock faciès

SandstoneLimestone

Clay, Shale


Cefoga


SummarySummary


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)


CefogaSedimentary Rocks

Classification

Sedimentary Rocks

Classification

CLASTIC (sandstone)

CARBONATE (limestones, dolomite)

EVAPORITES (salt)


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


CefogaClastic Rocks formation Clastic Rocks formation


CefogaCarbonates RocksCarbonates Rocks

J. Guillemot 1988

Limestone Dunham’s Classification


CefogaCarbonates Rocks formationCarbonates Rocks formation

Chemical precipitation or Biochemical formation


CefogaEvaporites RocksEvaporites Rocks

Conti

nenta

lCo

astal

Suba

queo

us

Sulfate Salt

Continental sebkha

Coastal sebkha

Crystalline, laminated,Turbidites

Displacive Halite

Chevron Halite


CefogaEvaporites Rocks formationEvaporites Rocks formation


CefogaSediment diagenesisSediment diagenesis

Sediments

(loose)

Sedimentary Rocks

(Consolidated)

Pressure, Temperature

Water circulation, biological factors

Ex : Sand Sandstones

Progressive transformation

Consequence of burial (subsidence)


CefogaMargin typesMargin types

Geological Society of America


CefogaMargin typesMargin types

M. T. Halbouty in AAPG mem. 40, 1986


CefogaSedimentary Bassin exempleSedimentary Bassin exemple

A. Perrodon and J. Zabeck, 1990

Paris Bassin


Cefoga


SummarySummary


CefogaSource Rock - DefinitionSource Rock - Definition

Rock Containing a few pourcentage of organic matter which eventually be transformed in hydrocarbon


CefogaKerogen typesKerogen types

TYPE I :

TYPE II :

TYPE III :

From lacustrine algae

From marine zoo or phyto plancton

From continental plants


Cefoga

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


Cefoga

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


Cefoga

Organic-richSource Rock

Thermally MaturedOrganic Matter Oil

The Origin of PetroleumThe Origin of Petroleum


Cefoga


SummarySummary


Cefoga

A rock in which oil and gas accumulates

Two main types :- clastic rocks- carbonate rocks

Reservoir rocks - DefinitionReservoir rocks - Definition


Cefoga

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


Cefoga

Good Porosity = Lots of Space for Petroleum

Pores(blue)

Porosity influencePorosity influence


Cefoga

Pore-Filling Cement Reduces Quality

= Less Space for Petroleum

Cement(pink)

Cement influenceCement influence


Cefoga

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


Cefoga


SummarySummary


CefogaSecondary MigrationSecondary Migration

hydrocarbons move through a permeable rocks toward the earth’surface

= SECONDARY MIGRATION


CefogaMigration and trappingMigration and trapping

Migrating hydrocarbons may encounter an impermeable layer before reaching earth’surface

= TRAPPING (Accumulation)


Cefoga

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


Cefoga

American Petroleum Institute, 1986

Salt DomeFault

Unconformity

Pinchout

Anticline

Hydrocarbon Trap examplesHydrocarbon Trap examples


Cefoga

2480

120° F120° F

350° F350° FGenerationGeneration

MigrationMigration

Seal RockSeal Rock

ReservoirRockReservoirRock

OilOil

WaterWater

Gas CapGas Cap

EntrapmentEntrapmentAccumulationAccumulation

Source Rock

Source Rock

SynthesisSynthesis


Cefoga

• 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


Cefoga

•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)


CefogaIn Situ PhasesIn Situ Phases


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


Cefoga


SummarySummary


CefogaPetroleum system - descriptionPetroleum system - description

Source Rock (+ organic matter)

Maturation (burial)

+

=

Generating Sub-system

Reservoir Seal

Trap

+

=

Trapping Sub-system

Migration


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


Cefoga

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


Cefoga

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’


Critical Moment = Time of Expulsion/MigrationCritical Moment = Time of Expulsion/Migration

Petroleum System at Critical MomentPetroleum System at Critical Moment


Cefoga

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’


Present-Day Petroleum SystemPresent-Day Petroleum System


Cefoga

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


GenerationGeneration

Time of Expulsion and Migration. (Trap must already exist)

Top oil window

Burial History ChartBurial History Chart


Cefoga


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


Cefoga

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


Cefoga

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

Engineering

Basic geology for Oil Exploration