Petroleum productions

1. INTRODUCTION TO PETROLEUM
ENGINEERING (PET2201)
Introduction to Hydrocarbon
Reservoir
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2. ROCKS
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3. Rock Cycle
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4. Types of Rocks
 Igneous
 Crystalline solid due to cooling of magma
 Example: Granite, Basalt
 Metamorphic
 Any rock: Due to rock minerals’ instability and out of
equilibrium with a new environmental conditions
 Example: Slate, Marble
 Sedimentary
 Secondary rock: Due to accumulation of small pieces broken
off of pre-existing rocks that compacted and cemented
together
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5. Types of Sedimentary Rocks
 Clastic
 Due to accumulations of clasts which is little pieces of broken
up rock which have compacted and cemented. Example
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6. Types of Sedimentary Rocks
 Chemical
 Due to repeated to flooding and evaporation of standing water
leaving behind thick deposit of dissolved minerals
 Example: Gypsum, Dolomite
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7. Types of Sedimentary Rocks
 Organic
 Due to accumulation of sedimentary debris, such as bits of
calcium from animal bones, shells etc. caused by organic
processes
 Example: Coal, Coquina
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8. Reservoir Rocks
 Mostly sedimentary rocks
 Due to pore-spaces in the accumulated sediments being sufficiently
large to permit the storage of hydrocarbons
 However, metamorphic and igneous reservoir rocks are possible
(fractured reservoirs): if these rock formations are mechanically
fractured by tectonic forces, then the space created by the natural
fractures can allow for hydrocarbon storage
 Major Types
 Sandstones (Clastic Sedimentary Rock)
 Carbonate (Dolomite, Limestone)
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9. Sandstone
 Dune Sandstone
 Formed by wind in both desert and coastal environments
 Only clay- and silt-sized particles are suspended in the air
 Composed of very-well-sorted fine sand and can be excellent
reservoir rock
 Ancient dune sandstones form extensive subsurface sandstone
reservoirs that cover large areas
 Shoreline Sandstone
 Series of buried shoreline sandstones that are oil and gas reservoirs
in the South Texas coastal plain
 The Yegua-Jackson beach sands of Eocene age are located inland,
and the Frio-Vicksburg beach sands of Oligocene age are located
on the Gulf of Mexico side
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10. Sandstone
 Delta Sandstone
 A delta is a mass of sediments deposited by a river flowing into a body of
water, such as a lake or ocean
 The river often bifurcates or divides into numerous channels, called
distributaries, on the delta
 The distributaries are located on low-lying swamps and marshes that are
covered with river water during floods
 Two important processes occur on a delta;
 The river deposits sediments, a constructive force
 Waves erode the sediments, a destructive force
 Ancient deltas are good environments for the formation and
accumulation of gas and oil
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11. Reservoir types
A constructive delta (a) is shaped by river deposition. Wave erosion is
relatively minor. The Mississippi River Delta is an example. A
destructive delta (b) is shaped by wave erosion. It hardly protrudes
from the shoreline. The Niger River Delta and the Nile River Delta 11

12. Reservoir types
Figure 6: Map of present-day and ancient shorelines and their ages
on the Niger River Delta, Nigeria. (Modified from Burke, 1972.) 12

13. Requirement for Hydrocarbon Reservoir
1. The Source Rock
2. Migration Path
3. The Cap Rock
4. The Reservoir Quality Rock
5. The Trap
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14. The Source Rock
 Organic-rich sedimentary rock where catagenesis converts dead
organic material, predominantly dead algae and zooplankton, into
kerogen and eventually hydrocarbons due to subsurface heat and
pressure
 It is a fine grained sediment that in its natural setting, has
generated and released enough hydrocarbons to form a commercial
accumulation of oil and gas.
 Clay or carbonate organic rich muds deposited under low energy,
reducing conditions.
 The most important factor: temperature.
 The action of heat on the insoluble organic matter (kerogen)
contained in source rocks leads to the formation of hydrocarbons.
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15. The Migration Path
 Pathway where mature oil and gas migrate from the source rock to
the trap.
 During the migration process, buoyancy is the dominant force
acting on the hydrocarbons.
 The transfer from source rocks to reservoir rocks is called primary
migration.
 Movement of petroleum within the porous and permeable
reservoirs beds is known as secondary migration.
 The primary cause of movement of fluids is compaction.
 The more permeable silt and sand bodies within compacting muds
are the main channels of fluid migration.
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16. The Cap Rock and Reservoir Rock
 The Cap Rock
 An impermeable rock that prevents lighter oil and gas from
migrating vertically away from the trap and towards the
surface
 The Reservoir Rock (Discussed)
 A rock that has sufficient reservoir quality to allow for
commercial hydrocarbon accumulations:
 sufficiently high porosity to allow for the storage of hydrocarbon in
commercial volumes;
 sufficiently high permeability to allow for the subsurface transport of
hydrocarbon at commercial production rates
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17. The Trap
 Definition
 A specific geological structure that keeps the hydrocarbon in
place over geological time (i.e., provides four-way closure to
the oil and gas).
 Traps can either be
 Stratigraphic in nature, where the trapping mechanisms are
dominated by the layering of sedimentary rocks, or
 Structural in nature, where the trapping mechanisms are
dominated by the folding and faulting of the rocks.
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18. Stratigraphic Traps
 Chiefly due to lateral variation in the lithology of the reservoir
rock, or a break in its continuity. A permeable reservoir rock
changes to a less permeable or to an impermeable rock.
 Facies changes, unconformities, and buried erosional or
constructive surfaces such as reefs, hills and other related
geologic phenomena forms basic requirement
 Two common types:
 Pinchout
 Truncated (Uncorfomity)
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19. Stratigraphic Traps
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20. Structural Traps
 Due to local structural deformation such as folding and/or
faulting of the rock layers
 The largest proportion of total proven reserves
 Faulting can also produce traps by juxtaposing a reservoir
against an impervious stratum.
 Draping or compaction over a buried hill, carbonate reef also
produces traps on a smaller scale.
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21. Structural Traps
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22. FLUIDS
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23. Types of Hydrocarbons/Reservoir Fluid
 Major Classification: Crude Oil and Gas
 Gas: Predominantly methane but with other lighter hydrocarbons
 Crude Oil: Complex mixture with large number of several types
of hydrocarbon and inorganic impurities, but can be classified into:
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24. Crude Oil Major HC Content
1. Paraffinic (or alkane series) hydrocarbons
2. Naphthenic (or saturated cyclic) hydrocarbons
3. Aromatic (or cyclic) hydrocarbons
4. Asphaltene hydrocarbons
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25. Type of Crude Oil Based HC Content
Crude oil can be referred to as:
1. Paraffinic if Kw≥12.5
2. Naphthenic or Aromatic if 12.5≤Kw≥10
3. Highly Aromatic if Kw<10
Whitson correlated the Watson Characterization Factor
𝐾𝑤=4.5579𝑀𝑜
0.15178
𝛾𝑜
−0.84573
KW is Watson Characterization Factor, oR1/3
Mo is the molecular weight of the mixture, lbm/lbm-mol
ϒo is the specific gravity of the mixture, dimensionless
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26. Type of Reservoir
Reservoirs can be classified by the fluid (hydrocarbon)
behavior under reservoir temperature and pressure before
after the beginning of production:
1. Undersaturated Black Oil (Low Shrinkage)
2. Saturated Black Oil (Low Shrinkage)
3. Undersaturated Volatile Oil (High Shrinkage)
4. Gas Condensate
5. Wet Gas Reservoir
6. Dry Gas
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27. Type of Reservoir
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FLUID TYPE DOMINANT PHASE IN
RESERVOIR
PHASES AT SEPARATOR
PRESSURE AND
TEMPERATURE
Black oil Liquid Liquid and Gas
Volatile oil Liquid Liquid and Gas
Retrograde gas Gas Liquid and Gas
Wet gas Gas Liquid and Gas
Dry gas Gas Gas

28. Classification of Reservoir Fluid
Reservoir Fluid (Hydrocarbon) can be classified further using:
 Gas–Oil Ratio: This is the volume of dissolved gas measured in
standard cubic feet (SCF) to the volume of oil measured in stock
tank barrels (STB)
 Oil Formation Volume Factor (FVF): This is the corresponding
volume of oil at reservoir conditions (RB for reservoir barrels) of
temperature and pressure divided by the stock tank volume of oil
(STB)
 Stock Tank Gravity of Separator Oil: Stock tank gravity is a
measure of specific gravity and is reported in °API
 Colour of Separator Liquid
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29. Classification of Reservoir Fluid
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30. DEFINITIONS & UNITS OF FLUID PROP.
• Definition and units of fluid properties commonly encountered in the
oil and gas industry
PRESSURE
• Fluid properties depend on pressure, temperature, and composition
• Pressure is defined as normal force divided by the area to which it is
applied
• Some common units of pressure include pounds/in2 or psi, pascals
(Newtons/m2), atmospheres, and bars
TEMPERATURE
• It is a measure of the average kinetic energy of a system
• The most commonly used temperature scales are the Fahrenheit and
Celsius scales
• The relationship between these scales is

31. DEFINITIONS & UNITS OF FLUID PROP
• Some applications, such as equations of state, require the use of
absolute temperature expressed in Kelvin or Rankine degrees
• The relationship between these scales is
•

32. DEFINITIONS & UNITS OF FLUID PROP

33. DEFINITIONS & UNITS OF FLUID PROP
COMPOSITION
• The composition of a fluid refers to the types and amounts of molecules
that comprise the fluid
• The relative amount of each component in a mixture may be expressed
in such units as volume fraction, weight fraction, or molar fraction
• The symbols xi and yi are often used to denote the mole fraction of
component i in the liquid and gas phases, respectively
• The mole fraction of component i in a gas mixture is
• The mole fraction of component i in an oil mixture is

34. DEFINITIONS & UNITS OF FLUID PROP
SPECIFIC GRAVITY
• Gas specific gravity is calculated at standard conditions using air
density as the reference density
• Where, Ma is apparent molecular weight;
• Gas density is calculated from the ideal gas equation of state as;
• Oil specific gravity is calculated at standard conditions using the
density of freshwater as the reference density

35. DEFINITIONS & UNITS OF FLUID PROP
SPECIFIC GRAVITY
• The American Petroleum Institute characterizes oil in terms of API
gravity, which is calculated from oil specify gravity γo at standard
temperature and pressure by the equation
• If specific gravity γo greater than 1, the oil is denser than water and API
less than 10
• If specific gravity γo less than 1, the oil is less dense than water and API
greater than 10
• Heavy oils with API less than 20 do not contain much gas in solution
and have a relatively large molecular weight and specific gravity γo
• Light oils with API greater than 30 typically contain a large amount of
volatile hydrocarbons in solution with a relatively small molecular
weight and specific gravity γo

36. DEFINITIONS & UNITS OF FLUID PROP
GAS-LIQUID RATIO (GLR)
• This is the ratio of a volume of gas divided by a volume of liquid at the
same temperature and pressure
• Two commonly used GLR are gas–oil ratio (GOR) and gas–water ratio
(GWR)
• The GWR is the ratio of gas volume to water volume at the same
temperature and pressure
• GOR is the ratio of gas volume to oil volume at the same temperature
and pressure
VISCOSITY
• Viscosity is a measure of resistance of a fluid to shearing
• Fluids like honey and heavy oil have a very high viscosity, while fluids
like water have a relatively low viscosity

37. DEFINITIONS & UNITS OF FLUID PROP
• In the oil industry, viscosity is often expressed in centipoise (cP)
• One centipoise (1 cp) equals 1 millipascal second (1 mPa.s = 0.001
Pa.s)
FORMATION VOLUME FACTOR (FVF)
• The volume of oil swells when gas is dissolved in the oil
• The FVF for oil, Bo, expresses this swelling as a ratio of the swollen
volume to the volume of the oil phase at a reference condition, usually
the stock tank pressure and temperature
• An example of a unit for oil FVF in oil field units is RB/STB where RB
refers to reservoir barrels and STB refers to stock tank barrels or it could
be rm3/sm3
• For example, an FVF of 1.5 RB/STB means that for every barrel of oil
produced to the stock tank, 1.5 barrels were taken from the reservoir

38. DEFINITIONS & UNITS OF FLUID PROP
• The 0.5 barrel volume difference represents the volume of oil phase lost
as volatile species escaped from the liquid phase during the reduction in
pressure from the reservoir up through the well to the separator and stock
tank
• FVF for oil usually ranges from 1 to 2 RB/STB. FVF for water is
usually about 1 RB/STB because gas is much less soluble in water than
in oil.
• Gas FVF varies over a wider range than oil FVF because gas volume is
more sensitive to changes in pressure