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

• Igneous Rocks– about 20% of all rocks– they are the product of the cooling of molten magma intruding from below the mantle of the crust.

• Metamorphic rocks– about 14% of all rocks– originate from mechanical, thermal, and chemical changes of igneous rocks

• Sedimentary Rocks– about 66% of all rocks– they are important to the study of petrophysics and petroleum reservoir engineering.

Sediments and Sedimentary Rocks

What are sediments?• Sediment - loose, solid particles originating from:

– Weathering and erosion of pre-existing rocks– 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%

• 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 :𝑘𝑔𝑚3 ;

𝑔𝑐𝑚3 ;

𝑙𝑏𝑚

𝑓𝑡 3

Density is highly variable in gases and increases nearly proportionally to the pressure level. Density in liquids is nearly constant. at °C and atm:

• Water: 1000 kg/m3;• Mercury: 13546 kg/m3;• Air: 1.23 kg/m3;• Paraffin: 800 kg/m3.

𝜌=𝑚𝑎𝑠𝑠𝑣𝑜𝑙𝑢𝑚𝑒

=𝑚𝑉

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.

𝑆𝐺𝑔𝑎𝑠=𝜌𝑔 𝑎𝑠

𝜌𝐴𝑖𝑟

𝑆𝐺 𝑙𝑖𝑞𝑢𝑖𝑑=𝜌 𝑙𝑖𝑞𝑢𝑖𝑑

𝜌𝑤𝑎𝑡𝑒𝑟

Specific gravity for gases

Specific gravity for liquids

Physical properties of Hydrocarbons

Specific gravity of gases:

𝑆𝐺𝑔𝑎𝑠=𝜌𝑔 𝑎𝑠

𝜌𝐴𝑖𝑟

P=14.7 psi = 101.325 kPa =1atmat T= 60 °F = 15 °F = 288.15 °K

𝜌𝐴𝑖𝑟=1.225𝑘𝑔𝑚3 =0.076

𝑙𝑏𝑓𝑡3

𝑆𝐺𝑔𝑎𝑠=𝜌𝑔 𝑎𝑠

0.076𝑙𝑏𝑓𝑡3

Physical properties of Hydrocarbons

Specific gravity of Crude Oil:

𝑆𝐺𝑜=𝜌𝑜

𝜌𝑤𝑎𝑡𝑒𝑟

P=14.7 psi = 101.325 kPa =1atmat T= 60 °F = 15 °F = 288.15 °K

𝜌𝑤𝑎𝑡𝑒𝑟=999𝑘𝑔𝑚3 =62.4

𝑙𝑏𝑓𝑡 3

𝑆𝐺𝑜=𝜌𝑜

62.4𝑙𝑏𝑓𝑡3

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:

𝐴𝑃𝐼 𝑔𝑟𝑎𝑣𝑖𝑡𝑦=141.5𝑆𝐺𝑜

−131.5

Conversely, 𝑆𝐺𝑜=141.5

𝐴𝑃𝐼 𝑔𝑟𝑎𝑣𝑖𝑡𝑦+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 °API (less than

870 kg/m3)

Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API (870

to 920 kg/m3)

Heavy crude oil is defined as having an API gravity below 22.3 °API (920 to

1000 kg/m3)

Extra heavy oil is defined with API gravity below 10.0 °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