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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?