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PETE 310

Properties of Black Oils

Definitions

(pages 224-240)

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Recall…. Black Oil Phase Diagram

Temperature

       P      r      e      s      s      u      r      e

Initial ReservoirConditions

CPPath of Production

Separator Conditions

25%

50%75%

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A Reservoir Engineer Questions

How much oil is in the reservoir?

How can I get it out?

How fast?

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Oil Properties Used in Reservoir

Engineering…

Formation Volume Factor of oil Bo

Total Formation Volume Factor of oil Bt

Solution Gas oil Ratio Rs

Coefficient of Isothermal CompressibilityCo

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Oil Properties Used in …Production,

EOR, Transportation…

Thermal Expansion Coefficient (EOR  –Steam flooding) bo

Interfacial Tension (EOR)Oil Viscosity mo (EOR, transportation,

production)

NOTE: Density is related to Bo

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Learning Goals

Understand the behavior of those PVT

properties (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

T P 

T P 

w 

o 

o   

    

5.1315.141

o 

o API 

  

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Definitions

Formation Volume Factor of Oil

Gas out of 

Solution

Pressure Decreasing

Reservoir P & T

Surface P & T

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Definitions

Units [= ]

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

PscTsc,atTankStockEnteringOilofVolume

T&PReservoiratGasDissolvedOilofVolume Bo 

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General Features of Bo

At reservoir T( constant )

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Solution Gas Oil Ratio (Rs)

How much gas is dissolved in the oil

volume per volume basis

Rs depends upon pressure, temperature

and oil type

Units [= ]

SCF gas /STB oil

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General Features of Rs

At 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 formation volume

factor

ssbgot  R R B B B

Units…

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

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General Shape of Bt

   B   o ,

   B   t

Reservoir Pressure

Pb

Reservoir T = constant

Bt=Bo

Bt

Bo

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       S     e     p     a     r     a      t     o     r

     g     a     s

gas gas

Decreasing Pressure

       S     e     p     a     r     a      t     o     r     g     a     s

       S     e     p     a     r     a      t     o     r     g     a     s

gas

StandardConditions S

     e     p     a     r     a      t     o     r     g     a     s

       S     e     p     a     r     a      t     o     r     g     a     s

oiloil oiloil

oil

STB

STB STB STB

StandardConditions

Bg =

Rv=

Bo

= Rs=

P

2

P1

P4

P3

Reservoir

Definition of Oil & Gas PVT Properties

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The Coefficient of Isothermal

Compressibility of Oil

Provides Instantaneous change of volume

with P at constant T

 AT 

 A Ao

P

V 

V 

T PC 

1

,

alternatively using molar volume

and specific volume

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Coefficient of Thermal Expansion 

   S  p  e  c   i   f   i  c   V

  o   l  u  m  e

Temperature

V

P

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Oil Viscosity

Viscosity is a measure of the resistance to flow

exerted by a fluid

This is called dynamic viscosity and has units of centipoise = g mass / 100 sec cm

Kinematic viscosity is viscosity / density, units

are incentistokes = 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 from natural

depletion or from recovery techniques

such as waterflooding and gas-injection

processes

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Variation of Oil Viscosity

   O

   i   l   V   i  s  c  o  s   i   t  y

T = constant

Pb

Single Phase FlowTwo Phase Flow

Gas Out ofSolution