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PETE 310

Lecture # 15

Properties of Black Oils

Definitions

(pages 224-240)

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Phase Diagram of aBlack Oil Reservoir

Temperature

Pressure

Initial ReservoirConditions

CPPath of Production

Separator Conditions

25%

50%75%

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Properties of Black Oils Needed for

Reservoir Engineering Calculations:

Formation Volume Factor of oil Bo

Total Formation Volume Factor of oil Bt

Solution Gas oil Ratio Rs

Coefficient of Isothermal Compressibility Co

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Properties of Black Oils Needed for

Reservoir Engineering Calculations:

Coefficient of isobaric thermal expansion bo Oil Viscosity mo Interfacial Tension

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Learning Goals

Understand the behavior of those PVTproperties (Bo,Rs,) vs P and type of

fluid (now)Evaluate PVT properties from (later)

Field data

Laboratory studies Correlations

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Definitions

Specific gravity of a liquid

API gravity

),(),(

11

11

TPTP

w

oo

1355.141

o

oAPI

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Definitions

Formation Volume Factor of Oil

Gas out ofSolution

Reservoir (P,T)

Surface (Ps,Ts)

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Definitions

Volume of Oil + Dissolved gasBo = at Reservoir Pressure & Temp.

Volume of Oil entering Stock

tank at Tsc, Psc

Units = Reservoir barrels (bbl)/Stock tank barrels(STB)

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General Shape of Bo

Bo

Reservoir Pressure

Pb

Reservoir T = constant

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Solution Gas Oil Ratio (Rs)

How much gas is dissolved in the oilvolume per volume basis

Rs depends upon pressure

Units [= ] SCF gas /STB oil

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General Shape of Solution GasOil Ratio (Rs)

Rs

Reservoir Pressure

Pb

Reservoir T = constant

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Total Formation Volume Factor Bt

Hg

Oil Bob

Hg

GasOil Bo

Bg(Rsb-Rs)

Pb

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Definition of Bt

Also called Two-phase formationvolume factor

ssbgot RRBBB

Units

bbl/STB + bbl/SCF * (SCF/STB)

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General Shape of Bt

Bo,

Bt

Reservoir Pressure

Pb

Reservoir T = constant

Bt=Bo

Bt

Bo

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Separator

gas

gas gas

Decreasing Pressure

Separatorgas

Separatorgas

gas

Standard

Conditions Separatorgas

Separatorgas

oiloil oiloil

oil

STB

STB STB STB

Standard

Conditions

Bg =

Rv=

Bo=

Rs=

P

2P1

P4

P3

Reservoir

Definition of Oil & Gas PVT Properties

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The Coefficient of IsothermalCompressibility of Oil

Provides Instantaneous change ofvolume with P at constant T

AT

AAo

P

V

V

TPC

1

,

Also with molar volumeand specific volume

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Coefficient of ThermalExpansion

SpecificV

olume

Temperature

V

P

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Oil Viscosity

Viscosity is a measure of the resistanceto flow exerted by a fluid

This is called dynamic viscosity and hasunits of

centipoise = g mass / 100 sec cm

Kinematic viscosity is viscosity / density,units are in

centistokes = centipoise /g/cc

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Needs of Crude Oil Viscosity

Calculation of two-phase flow

Gas-lift and pipeline design

Calculate oil recovery either fromnatural depletion or from recoverytechniques such as waterfloodingand gas-injection processes

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Variation of Oil Viscosity

O

ilViscosity

T = constant

Pb

Single Phase FlowTwo Phase Flow

Gas Out ofSolution