Course Objectives:

1) To introduce you to petroleum geology, specifically the origins and typesof hydrocarbons and the locations of hydrocarbon (sedimentary basins,reservoirs, traps, seals).

2) To introduce you to exploration techniques; seismics and interpretation, well logs and interpretation, new technologies (Satellite techniques)

Useful Sources:

Elements of Petroleum Geology by Richard Selley, Academic Press, 1998

Geology and Geochemistry of oil and gas by George Chilingar, Elsevier Publication, 2005

Dynamic Earth

Dimensions of Earths Dynamics Multidimensional

Dimensions of Earths Dynamics - Temporal

Diagram of geological time scale

630EdiacaranNeoproterozoic

Proterozoic

542Cambrian488Ordovician444Silurian416Devonian

359Carboniferous (Mississippian/Pennsylvanian)

300PermianPaleozoic

251Triassic

200Jurassic145.5CretaceousMesozoic

65.5Paleogene (Paleocene/Eocene/Oligocene)

23.0Neogene(Miocene/Pliocene/Pleistocene/Holocene)

CenozoicPhanerozoic

Start, MillionYears Ago

PeriodEraEon

Table of Geologic Time Scale

Gabro Intrusive Igneous Rock Rock forming Minerals in Gabro: pyroxene, plagioclase, amphibole, and olivine

Thin section under microscope

Geology in a descending view

Rocks and Minerals

Gabro forming Minerals

Rock is a naturally occurring aggregate of minerals.

A Mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.

Rock Types

Igneous Metamorphic Sedimentary

Rocks

Rocks....

Igneous Rocks: are formed when molten magma cools off.

Igneous RocksPlutonic (Intrusive) Rocks: Form when magma cools and crystallizes slowly within the Earths crust (Granite) Volcanic (Extrusive) Rocks: Form when magma reachesthe surface (Pumice and Basalt)

Basalt (Igneous Volcanic)The tracks in the rock indicate the way of the lava flow

Rocks....

Rocks....Metamorphic Rocks: Rocks which have been modified in their original compositions bymeans of heat, pressure and chemical alterations applied to them

Foliated metamorphic rocks: have a layered or banded appearance that is produced by exposureto heat and directed pressure; Gneiss, Phyllite, Schist

Non-foliated metamorphic rocks: Do not have a layered or banded appearance; Marble, Quartzite

Metamorphic Rocks

Gneiss Marble

Sedimentary Rocks: are formed by the accumulation of sediments

Sedimentary Rocks (Classification based on the source of their Sediments)

Clastic: Form from rocks that have been broken down into fragments by weathering and erosion followed by transportation; Breccia, Conglomerate, Sandstone, Shale

Chemical: Form when dissolved materials precipitate from solution; Rock Salt (Halite), Limestone

Organic: Form from the accumulation of plant or animal debris; Coal

Sedimentary Rocks cover 75-80% of the Earth's land area and are the most Important group of rocks in Petroleum Geology

Rocks....

Sandstone Shale

Iron Ore (Hematite) BrecciaSedimentary Rocks

Minerals: Rock forming elements are called minerals

Minerals(Chemical

Classification)

Silicates

Carbonates

Sulfates

Halides

Oxides

Sulfides

Phosphates

Elements

Organics

Isosilicates; Fayalite (Fe2SiO4)Sorosilicates; Epidote

Cyclosilicates; Benitoite (BaTi(Si3O9)Inosilicates; Enstatite ( MgSiO3)

Phyllosilicates; Kaolinite(Al2Si2O5(OH)4)

Tectosilicates; Quartz (SiO2)

Minerals

The main minerals in sedimentary rocks

QuartzFeldsparMicaCalciteDolomiteSiderite

Pyrite

various heavy and clay minerals; Illite

Mineral Identification Approaches

X-ray diffraction

Scanning electron microscopePolarising microscope

Physical visual properties

HardnessColorLustreSpecific weight

Crystal Structure

Hydrocarbons: substance made of hydrogen and carbon (among other elements)

Reservoir: Reservoirs are the porous and permeable rocks that contain commercial deposits of hydrocarbons.

Source Rock: Mature rock being capable of hydrocarbon production.

Cap Rock: An impermeable rock which prevents the hydrocarbon discharge from the reservoir.

Generation and Migration: How oil is generated and how it migrates to reservoir.

Oil trap: A place where oil is commercially accumulated (trapped).

Porosity: Fraction of void space (opening) in the rock, =Vv / Vt (Ratio of void volume / total volume)

Effective Porosity: Fraction of the total volume in which fluid flow is effectively taking place (excluding dead-end pores or non-connected cavities)

Permeability (K): is a measure of the ability of rock to transmit fluids (milidarcy)

Basic definitions in Petroleum Geology:

grain size coarse high permeabilityfine low permeability

sorting good high porositypoor low porosity

It is very important (and also very difficult) to determine the ratio of effective to total porosity. Total porosity is fairly easy to measure, but may not tell much about the amount of HC that can be produced.

Porosity measurements

Well logs; Sonic, Neutron, and Density

Seismics: density decreases with increasing porosity

Direct measurements of cores: in lab

Basic porosity types in carbonate rocks (from Weber, 1996).

Permeability

Hydraulic Conductivity; Ability of fluids to pass througha porous medium

Intrinsic Permeability

Measuring permeability: Very difficult to measure,Yet very critical

Interpretation of permeability

Can be measured by applying Darcys law on the material. such experiments can be conducted by creating a hydraulicgradient between two points, and measuring the flow rate.

Reservoir parameters:Reservoir grain size and shape

Fluids Properties :Viscosity, SW

Represents a property of the porous reservoir only,specifically the size of the pore openings

1- Can be measured in drill holes with Drill Stem Tests (DST) 2- Estimated with log response3- measured directly on core samples with Permeameters

Structural Geology and its effect on source rocks physical properties (e.g. Porosity)

Fault - France Fault Types

Structural Geology; Another aspect of dynamic Earth

Rotational ShearTypical Anticline and Syncline

Structural Trap

Migration of fluids along a normal fault at Gebel Zeit, Egypt has resulted in a hydrocarbon seep adjacent to the granite outcrop (from Hunt, 1979 after Link, 1952).

Structural Geology; Another aspect of dynamic Earth

Kerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks.

It is insoluble in normal organic solvents because of the huge molecular weight.

The soluble portion is known as bitumen.

When heated to the right temperatures in the Earths crust, some types of kerogen release crude oil or natural gas (hydrocarbons).

When such kerogens are present in high concentration in rocks such as shale, and have not been heated to a sufficient temperature to release their hydrocarbons,they may form oil shale deposits.

Oil is generated in the source rock as part of the solid kerogen becomes liquidand can therefore hydraulically fracture its way out of the source rock

The generated oil migrates out of the source rock (primary migration) into a reservoirrock within which it can migrate (secondary migration) towards a place where itcan accumulate (trap)

Reservoir rocks have porosity (storage) and permeability (transmissibility)

Principles

Schematic structures of oil-generating and gas-generating organicmatter (after Hunt, 1979).

Principles

Outcrop of Ordovician oil shale (kukersite), Northern Estonia.

Clay minerals are important in petroleum geology because they formclaystones which are seals for hydrocarbon traps.

Clays within sandstone reservoirs can affect hydrocarbon production by

reducing the porosity and permeability of reservoirs

helping or hindering sandstone cementation

swelling

moving during production.

Common clay minerals are illite, kaolinite, smectite, chlorite and glauconite

Principles

Clays have higher porosities than sands when deposited but very lowhydraulic conductivity (they do not release water quickly due to their structural nature

Except kaolinite, the clay minerals are radioactive, usually because of potassium.

A source rock is a claystone or carbonate rock containing organic matter, usually 1.5 to 20% depending on type

Different types of organic matter give different types of hydrocarbons

Hydrocarbon gas can be generated from organic material by bacteria at shallow depths to give biogenic gas accumulations

Most hydrocarbons are generated by thermal maturation at depths below those where bacteria can survive, usually hotter than about 50C and mostly deeper than 1 kilometre

Hydrocarbons are cooked out of the source rock, oil before gas, as it is buried and becomes hotter

Principles

Relative yields of oil and gas from different kerogen types (after Hunt, 1979)

Diagenesis: Any physical, chemical or biological changes to a sediment after deposition is called diagenesis. These changes take place in relatively low pressure and temperature conditions.The end product of this stage is Kerogen

Catagenesis: When temperature and pressure increases, Kerogens thermodynamic structure changes accordingly which leads to maturation. Thermal degradation and cracking of Kerogen during maturation results in hydrocarbon production.

Metagenesis: As temperature increases, considerable amount of methane is produced while production of hydrocarbon from Kerogen is terminated.

Principles

Relative quantities of hydrocarbons in fine-grained, non-reservoir rocks. Areas under the curves are proportional to masses as carbon (after Hunt, 1979).

Maturation and oil generation

Organic maturity through time; Yellow and red colours indicate that maturation issufficient for oil generation (from the University of Columbia Maturation of the Smackover Formation web site).

End of the Early Cretaceous (100 Ma) End of the Palaeogene (24 Ma)

Exploration Techniques

Geophysics

Geochemistry

Geology

SeismicMagneticElectric

Drilling: : will be covered in drilling lecture

Advanced New Techniques: Remote Sensing

Electromagnetic (EM)Gravity

Gas GeochemistryOrganic Geochemistry

PaleontologySedimentologyStratigraphy

Alteration Geochemistry

Any Questions?