Basics of Petroleum GeologyBasics of Petroleum Geology

Presented By:Presented By:

Shahnawaz MustafaShahnawaz Mustafa

The science of petroleum geologyThe science of petroleum geology

•• ChemistryChemistryGeochemistry is a major component of petroleum Geochemistry is a major component of petroleum geologygeology

•• Detailed knowledge of the mineralogical Detailed knowledge of the mineralogical composition of rocks composition of rocks –– reservoir quality.reservoir quality.composition of rocks composition of rocks –– reservoir quality.reservoir quality.

•• PorePore--fluid chemistryfluid chemistry

•• PhysicsPhysicsGeophysics contributes to:Geophysics contributes to:

•• Understanding the structures involved in trapping: Understanding the structures involved in trapping: folds, faultsfolds, faults

•• Understanding the wells: wireline logs, lithology, Understanding the wells: wireline logs, lithology, porosityporosity

•• BiologyBiology•• Biochemistry: transformation of plant and animal Biochemistry: transformation of plant and animal tissues into kerogen and through to oil and gas.tissues into kerogen and through to oil and gas.

•• Study of fossil life: PaleontologyStudy of fossil life: Paleontology•• Study of fossil life: PaleontologyStudy of fossil life: Paleontology

Formation of an oil accumulationFormation of an oil accumulation

Burial of adequate organic source material.Burial of adequate organic source material.

�� most petroleum is derived from the accumulation of trillions of most petroleum is derived from the accumulation of trillions of individual microindividual micro--organisms.organisms.

Burial to the appropriate depths.Burial to the appropriate depths.

depths of 2depths of 2--6 km and temperatures of 606 km and temperatures of 60--160º C.160º C.�� depths of 2depths of 2--6 km and temperatures of 606 km and temperatures of 60--160º C.160º C.

Presence of a reservoirPresence of a reservoir--quality rock.quality rock.

a porous storage space. Sandstone and limestones are the a porous storage space. Sandstone and limestones are the most common reservoir rocks. To be a reservoir they must most common reservoir rocks. To be a reservoir they must have:have:

�� PorosityPorosity, to hold the hydrocarbons, to hold the hydrocarbons

�� PermeabilityPermeability, to allow fluid flow, to allow fluid flow

Presence of an adequate sealPresence of an adequate seal

�� A seal is an impermeable bed (such as a shale or a bed of salt) A seal is an impermeable bed (such as a shale or a bed of salt) that sits on top of the trap and prevents the hydrocarbons rising that sits on top of the trap and prevents the hydrocarbons rising any further.any further.

Presence of a trapPresence of a trapPresence of a trapPresence of a trap

�� In order to prevent the hydrocarbons rising to the surface and In order to prevent the hydrocarbons rising to the surface and escaping they must be caught in a confined space, termed a escaping they must be caught in a confined space, termed a trap. i.e. the source, reservoir and seal must be arranged in such trap. i.e. the source, reservoir and seal must be arranged in such a way that the petroleum is trapped.a way that the petroleum is trapped.

Organic MatterOrganic Matter

When an organism (plant or animal) dies, it is When an organism (plant or animal) dies, it is normally oxidized normally oxidized

Under exceptional conditions: organic matter is buried Under exceptional conditions: organic matter is buried Under exceptional conditions: organic matter is buried Under exceptional conditions: organic matter is buried and preserved in sedimentsand preserved in sediments

The composition of the organic matter strongly The composition of the organic matter strongly influences whether the organic matter can produce influences whether the organic matter can produce coal, oil or gas.coal, oil or gas.

Basic components of organic Basic components of organic matter in sedimentsmatter in sediments

•• PROTEINSPROTEINS

•• CARBOHYDRATESCARBOHYDRATES

•• LIPIDS (Fats)LIPIDS (Fats)•• LIPIDS (Fats)LIPIDS (Fats)

•• LIGNINLIGNIN

All of these + Time + Temperature + All of these + Time + Temperature + Pressure = Pressure = KEROGENKEROGEN

Types of KerogenTypes of Kerogen

•• Type IType I : algal kerogen: algal kerogen–– “best” oil source“best” oil source–– LipidLipid--richrich

•• Type IIType II: herbaceous : herbaceous kerogenkerogenkerogenkerogen–– Good oil sourceGood oil source–– Includes zooplankton Includes zooplankton (sapropelic)(sapropelic)

•• Type IIIType III: woody : woody kerogen (coaly)kerogen (coaly)–– Good gas sourceGood gas source

OIL FORMATIONOIL FORMATION

The Petroleum SystemThe Petroleum System

The Source RockThe Source Rock

•• A type of rock A type of rock which contains which contains organic matter organic matter and is capable and is capable to generate the to generate the to generate the to generate the hydrocarbons.hydrocarbons.

•• Best example of Best example of source rock is source rock is shale.shale.

The Reservoir RockThe Reservoir Rock

•• A reservoir rock A reservoir rock is that kind of is that kind of rock which can rock which can hold the hold the hydrocarbons.hydrocarbons.hydrocarbons.hydrocarbons.

•• Most common Most common examples of examples of reservoir rocks reservoir rocks are sandstone are sandstone and Carbonates and Carbonates (limestone and (limestone and dolomite).dolomite).

The Reservoir Rock: DolomiteThe Reservoir Rock: Dolomite

•• This is an example of This is an example of an important reservoir an important reservoir rock type. rock type.

•• Fossils have been Fossils have been hollowed out by the hollowed out by the hollowed out by the hollowed out by the chemical conversion chemical conversion of limestone to of limestone to dolomite, creating dolomite, creating pore spaces so large pore spaces so large that they are that they are sometimes called sometimes called ““cavernous porositycavernous porosity””

The SealThe Seal

•• The seal or cap rock The seal or cap rock is an impermeable is an impermeable rock which don’t rock which don’t allow the allow the hydrocarbons to hydrocarbons to hydrocarbons to hydrocarbons to escape from the escape from the reservoir rock. reservoir rock.

•• Common examples Common examples of cap rocks are, of cap rocks are, chalks , shales, clays chalks , shales, clays etc.etc.

The TrapThe Trap

•• A subsurface obstacle to flow of petroleum A subsurface obstacle to flow of petroleum to the earth’s surface.to the earth’s surface.

•• Classified (broadly) intoClassified (broadly) into

Structural TrapsStructural TrapsStructural TrapsStructural Traps

Examples: folds and faults.Examples: folds and faults.

Stratigraphic TrapsStratigraphic Traps

Examples: pinch out and unconformity trapsExamples: pinch out and unconformity traps

Structural TrapsStructural Traps

Stratigraphic trapsStratigraphic traps

Migration ProcessesMigration Processes

•• Primary Migration:Primary Migration:involves the involves the expulsion of expulsion of petroleum from petroleum from the source rocks to the source rocks to reservoir rock.reservoir rock.the source rocks to the source rocks to reservoir rock.reservoir rock.

•• Secondary Secondary Migration:Migration: involves involves the the movement of movement of petroleum through petroleum through permeable layers permeable layers (carrier beds) to (carrier beds) to the trapthe trap..

Reservoir Porosity and Reservoir Porosity and PermeabilityPermeability

There are two fundamental There are two fundamental physical properties that a physical properties that a good reservoir must good reservoir must have: have: have: have: (1)(1) porosityporosity, or , or sufficient sufficient void space to contain void space to contain significant petroleumsignificant petroleum..

(2) (2) permeabilitypermeability, , the the ability of petroleum to ability of petroleum to flow through these voidsflow through these voids..

Types of porosityTypes of porosity

Reservoir properties are to be confirmed through

• Direct methods (Core)• Direct methods (Core)

• Indirect method (logs)

Presence of Oil/Gas is confirmed through(1) Logs (2) Cuttings/cores (3) Testing

Seal Integrity is the most important factor for preservation of hydrocarbon in pools