petroleum geology.pptx
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Petroleum Geology
Fundamental of petroleum Engineering coursePeyman Maroufi
Petroleum Engineering departmentSoran university
What is petroleum
What is petroleum
Petroleum is a mixture of naturally occurring hydrocarbons which may exist in the solid, liquid, or gaseous states, depending upon the conditions of pressure and temperature to which it is subjected.
Whereas natural gas contains a few lighter hydrocarbons, both crude oil and tar deposits may consist of a large number of different hydrocarbons.
1) Liquid Hydrocarbons: Crude oil or Petroleum2) Gas Hydrocarbons: Natural Gas: methane,
butane, propane, etc.3) Solid Hydrocarbons: Tars and Asphalt
What is petroleum
Virtually all petroleum is produced from the earth in either liquid or gaseous form, and commonly, these materials are referred to as either crude oil or natural gas, depending upon the state of the hydrocarbon mixture.
Petroleum consists chemically of approximately 11 to 13 wt % hydrogen and 84 to 87 wt % carbon.
Traces of Oxygen, Sulfur, Nitrogen, and Helium may be found as impurities in crude petroleum.
Although all petroleum is constituted primarily of carbon and hydrogen, the molecular constitution of crude oils differs widely.
Non hydrocarbon Components of Petroleum
Petroleum also contain compounds:1) Sulfur Compounds.
2) Nitrogen
3) Oxygen
4) Little metals
Common non hydrocarbon constituents of petroleum are:
1) Nitrogen (
2) carbon dioxide
3) hydrogen sulfide (
Chemistry of Petroleum
Resins and Asphaltenes
The chemicals in petroleum are classified as:1) Paraffins2) Naphthenes3) Aromatics4) Resins-asphaltenes
Resins and asphaltenes are large molecules, primarily hydrogen and carbon, with one to three sulfur, oxygen, or nitrogen atoms per molecule.
The basic structure is composed of rings, primarily aromatic, with from three to ten or more rings in each molecule. The non hydrocarbon atom can be a part of the ring structure or can be located in links connecting the rings.
The color of petroleum is determined largely by the quantity of resins and asphaltenes present, although the greenish cast of some crude oils is probably due to the presence of molecules containing six or more rings.
Composition of petroleum
Average and Range of Hydrocarbon series molecules in Crude Oil
Origin of petroleum
The theories of the origin of petroleum may be classified as:
1) Organic
2) Inorganic
Origin of petroleum
Origin of petroleum:
1) Organic theories:The organic theories assume that petroleum evolved from decomposition of vegetable and animal organisms that lived during previous ages.
2) Inorganic theories:The inorganic theories attempt to explain the formation of petroleum by assuming chemical reaction among water, carbon dioxide and various inorganic substances such as carbides and carbonates, in the earth.
Origin of petroleum
The organic theory of petroleum origin (most accepted)
Over many years, pressure, temperature, bacteria, and other reactions caused these dead organisms to change into oil and gas.
Ancient seas covered much of the present land area millions of years ago
Over the years, rivers flowing down to these seas carried large volumes of mud and sedimentary materials ( containing small plants and animals) into the sea.
The buildup of thousands of feet of mud and sediment layers over the sea floor.
The sea floors were slowly sink and squeezed to form the sedimentary rocks (the sandstones and shales, and the carbonates)
The rocks where oil and gas were formed are known as the source rock.
Origin of petroleum
The Origin and Habitat of Petroleum
Accumulation of Oil and Gas The accumulation of economic volumes of petroleum (oil and/or gas) in the
subsurface requires that several essential geological elements and processes be present at specific time and space.
The essential elements of a petroleum system include the following:
1) Source rock
2) Reservoir rock
3) Migration
4) Traps
The Origin and Habitat of Petroleum
To have a petroleum accumulation it is necessary to have source rock and a reservoir or storage bed
Source rock:
Source rocks generate and expel petroleum when sufficient thermal energy is imparted to the sedimentary organic matter (kerogen) to break chemical bonds. This heating is induced usually by burial by overburden rock.
Reservoir rock:
A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids.
A suitable reservoir rock is porous and permeable. That is , the pores interconnect so that fluids can migrate through the rock.
Sedimentary rocks are the most common reservoir rocks because they have more porosity than most igneous and metamorphic rocks and
The Origin and Habitat of Petroleum
Migration of petroleum :The movement of hydrocarbons from their source into reservoir rocks.
1) Primary migration
2) Secondary migration
The Origin and Habitat of Petroleum
1) Primary migration:The movement of newly generated hydrocarbons out of their source rock is primary migration, also called expulsion.
2) Secondary migration:The further movement of the hydrocarbons into reservoir rock in a hydrocarbon trap or other area of accumulation is secondary migration.
The Origin and Habitat of Petroleum
Traps
If nothing stops oil from rising, it will reach surface. A natural barrier, or trap, must exist for a petroleum
accumulation to form.
Trap:A configuration of geologic features where oil and gas (petroleum) can be barred from further movement.
Traps
As oil and gas are lighter than the ground water which permeates the porous rocks below the water table, it is evident that the upward movement of petroleum must be restricted in order that accumulations exist at depth
Traps
The closure of the trap is the distance between the crest and the spill point (lowest point of the trap that can contain hydrocarbons).
Traps
Classification of Hydrocarbon Traps
1) Structural traps : Structural traps are traps that are formed because of a deformation in the rock layer that contains the hydrocarbons.
a) Anticlinal traps: an upward fold in the layers of rock
b) Fault traps: A fault trap occurs when the formations on either side of the fault have been moved into a position that prevents further migration of petroleum.
c) diapiric traps: produced by intrusion of salt or mud diapirs
2) Stratigraphic traps: result when a depositional bed changes from permeable rock into fine-grain impermeable rock
Traps
Traps
The Origin and Habitat of Petroleum
GENERATION, MIGRATION, AND TRAPPING OF HYDROCARBONS
Types of Rocks
β’ Igneous Rocksβ about 20% of all rocksβ they are the product of the cooling of molten magma intruding from below the mantle of the crust.
β’ Metamorphic rocksβ about 14% of all rocksβ originate from mechanical, thermal, and chemical changes of igneous rocks
β’ Sedimentary Rocksβ about 66% of all rocksβ they are important to the study of petrophysics and petroleum reservoir engineering.
Sediments and Sedimentary Rocks
What are sediments?β’ Sediment - loose, solid particles originating from:
β Weathering and erosion of pre-existing rocksβ Chemical precipitation from solution, including secretion by
organisms in water
Sediments and Sedimentary Rocks
What is a Sedimentary Rock?Sedimentary rocks are types of rock that Sediments after they are deposited may be buried and undergo physical and chemical change resulting in a solid rock.
Sediments and Sedimentary Rocks
The three most common sedimentary rocks associated with petroleum reservoirs are:
1) sandstone
2) shale
3) limestone.
Sedimentary Rock Types
Siltstone, mudand shale
~75%
β’ Relative abundanceSandstone
and conglomerate~11%
Limestone anddolomite
~13%
Physical properties of Hydrocarbons
Physical properties of Hydrocarbons
Physical properties of Hydrocarbons
ViscosityDensitySpesific gravityAPI
Physical properties of Hydrocarbons
Density:
Density is an extremely important property of matter.
The density of a fluid (or any other form of matter) is the amount of mass
per unit volume.
Dimensions: Units :πππ3 ;
πππ3 ;
πππ
ππ‘ 3
Density is highly variable in gases and increases nearly proportionally to the pressure level. Density in liquids is nearly constant. at Β°C and atm:
β’ Water: 1000 kg/m3;β’ Mercury: 13546 kg/m3;β’ Air: 1.23 kg/m3;β’ Paraffin: 800 kg/m3.
π=πππ π π£πππ’ππ
=ππ
Physical properties of Hydrocarbons
Specific gravity: Specific gravity, denoted by SG.
Specific gravity is defined as the ratio of the density of a fluid to the density of
some standard fluid at a specified temperature and pressure.
Commonly standard fluid for liquids is Water and for gasses is Air.
ππΊπππ =ππ ππ
ππ΄ππ
ππΊ ππππ’ππ=π ππππ’ππ
ππ€ππ‘ππ
Specific gravity for gases
Specific gravity for liquids
Physical properties of Hydrocarbons
Specific gravity of gases:
ππΊπππ =ππ ππ
ππ΄ππ
P=14.7 psi = 101.325 kPa =1atmat T= 60 Β°F = 15 Β°F = 288.15 Β°K
ππ΄ππ=1.225πππ3 =0.076
ππππ‘3
ππΊπππ =ππ ππ
0.076ππππ‘3
Physical properties of Hydrocarbons
Specific gravity of Crude Oil:
ππΊπ=ππ
ππ€ππ‘ππ
P=14.7 psi = 101.325 kPa =1atmat T= 60 Β°F = 15 Β°F = 288.15 Β°K
ππ€ππ‘ππ=999πππ3 =62.4
ππππ‘ 3
ππΊπ=ππ
62.4ππππ‘3
The specific gravity of crude oils ranges from about 0.75 to 1.01.
Physical properties of Hydrocarbons
The American Petroleum Institute gravity, or API gravity Although the density and specific gravity are used extensively in the petroleum
industry, the API gravity is the preferred gravity scale.
This gravity scale is precisely related to the specific gravity by the following
expression:
π΄ππΌ ππππ£ππ‘π¦=141.5ππΊπ
β131.5
Conversely, ππΊπ=141.5
π΄ππΌ ππππ£ππ‘π¦+131.5
Physical properties of Hydrocarbons
API gravity, is a measure of how heavy or light a petroleum liquid is compared to water.
Crude oil is classified as light, medium or heavy, according to its measured
API gravity.
Light crude oil is defined as having an API gravity higher than 31.1 Β°API (less than
870 kg/m3)
Medium oil is defined as having an API gravity between 22.3 Β°API and 31.1 Β°API (870
to 920 kg/m3)
Heavy crude oil is defined as having an API gravity below 22.3 Β°API (920 to
1000 kg/m3)
Extra heavy oil is defined with API gravity below 10.0 Β°API (greater than 1000 kg/m3)
Crude Oils
Light CrudePalo Pinto Field
North Texas
Light CrudePalo Pinto Field
North Texas
Heavy CrudeHumble Oil FieldSouthwest Texas
Heavy CrudeHumble Oil FieldSouthwest Texas
Physical properties of Hydrocarbons
Viscosity:
The viscosity of a fluid is a measure of the internal fluid friction (resistance) to
flow.
If the friction between layers of the fluid is small, i.e., low viscosity, an applied
shearing force will result in a large velocity gradient.
As the viscosity increases, each fluid layer exerts a larger frictional drag on the
adjacent layers and velocity gradient decreases.
Symbols: o, g, w
Units: cpRange and typical values
0.25 to 10,000 cp, Black oil0.5 to 1.0 cp, Water0.012 to 0.035 cp, Gas
Physical properties of Hydrocarbons