PETE 310PETE 310

Lecture # 15Lecture # 15Properties of Black Oils Properties of Black Oils

DefinitionsDefinitions(pages 224-240)(pages 224-240)

Phase Diagram of a Phase Diagram of a Black Oil ReservoirBlack Oil Reservoir

Temperature

Pres

sure

Initial Reservoir Conditions

CPPath of Production

Separator Conditions

25%50%75%

Properties of Black Oils Needed for Properties of Black Oils Needed for Reservoir Engineering Calculations:Reservoir Engineering Calculations:

– Formation Volume Factor of oil Formation Volume Factor of oil BoBo

– Total Formation Volume Factor of oil Total Formation Volume Factor of oil BtBt

– Solution Gas oil Ratio Solution Gas oil Ratio RsRs

– Coefficient of Isothermal Compressibility Coefficient of Isothermal Compressibility CoCo

Properties of Black Oils Needed for Properties of Black Oils Needed for Reservoir Engineering Reservoir Engineering Calculations:Calculations:

– Coefficient of isobaric thermal expansion Coefficient of isobaric thermal expansion oo

– Oil Viscosity Oil Viscosity oo

– Interfacial TensionInterfacial Tension

Learning GoalsLearning Goals

Understand the behavior of those Understand the behavior of those PVT properties (Bo,Rs,…) vs P and PVT properties (Bo,Rs,…) vs P and type of fluid type of fluid (now)(now)

Evaluate PVT properties from Evaluate PVT properties from (later)(later)– Field dataField data– Laboratory studiesLaboratory studies– CorrelationsCorrelations

DefinitionsDefinitions

Specific gravity of a liquidSpecific gravity of a liquid

API gravityAPI gravity

),(),(

11

11

TPTP

w

oo

1355.141

o

o API

DefinitionsDefinitionsFormation Volume Factor of OilFormation Volume Factor of Oil

Gas out of Gas out of SolutionSolution

Reservoir Reservoir (P,T)(P,T)

Surface Surface (Ps,Ts)(Ps,Ts)

Definitions Definitions

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

Volume of Oil entering Volume of Oil entering Stock Stock

tank at Tsc, Psctank at Tsc, PscUnits = Reservoir barrelsUnits = Reservoir barrels (bbl)(bbl) /Stock tank barrels/Stock tank barrels (STB)(STB)

General Shape of BoGeneral Shape of Bo

BoBo

Reservoir PressureReservoir PressurePbPb

Reservoir T = constantReservoir T = constant

Solution Gas Oil Ratio (Rs)Solution Gas Oil Ratio (Rs)

How much gas is dissolved in How much gas is dissolved in the oil volume per volume the oil volume per volume basisbasis

Rs depends upon pressureRs depends upon pressureUnits [= ] SCF gas /STB oilUnits [= ] SCF gas /STB oil

General Shape of Solution General Shape of Solution Gas Oil Ratio (Rs)Gas Oil Ratio (Rs)

RsRs

Reservoir PressureReservoir PressurePbPb

Reservoir T = constantReservoir T = constant

Total Formation Volume Total Formation Volume Factor BtFactor Bt

HgHg

OilOil BBobob

HgHg

GasGas

OilOil BBoo

BBgg(R(Rsbsb-R-Rss))

PPbb

Definition of BtDefinition of Bt

Also called Two-phase Also called Two-phase formation volume factorformation volume factor

ssbgot RRBBB

Units…Units…

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

General Shape of BtGeneral Shape of BtBo

, Bt

Bo, B

t

Reservoir PressureReservoir PressurePbPb

Reservoir T = constantReservoir T = constant

Bt=BoBt=BoBtBt

BoBo

Sep

arat

or g

as

gas gas

Decreasing Pressure

Sep

arat

or g

as

Sep

arat

or g

as

gas

StandardConditions S

epar

ator

gas

Sep

arat

or g

as

oiloil oiloil

oil

STB

STBSTB STB

StandardConditions

Bg =

Rv =

Bo= Rs=

P2 P1

P4 P3 Reservoir

Definition of Oil & Gas PVT PropertiesDefinition of Oil & Gas PVT Properties

The Coefficient of The Coefficient of Isothermal Isothermal

Compressibility of OilCompressibility of OilProvides Instantaneous Provides Instantaneous

change of volume with P at change of volume with P at constant Tconstant T

AT

AAo PV

VTPC

1,

Also with molar volume Also with molar volume and specific volumeand specific volume

(Use in Steam Injection Processes)(Use in Steam Injection Processes)

Coefficient of Thermal Coefficient of Thermal ExpansionExpansion

Oil ViscosityOil Viscosity

Viscosity is a measure of the Viscosity is a measure of the resistance to flow exerted by a fluidresistance to flow exerted by a fluid

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

Kinematic viscosity is viscosity / Kinematic viscosity is viscosity / density, units are in density, units are in centistokes = centipoise /g/cccentistokes = centipoise /g/cc

Needs of Crude Oil Needs of Crude Oil ViscosityViscosity

Calculation of two-phase flowCalculation of two-phase flowGas-lift and pipeline designGas-lift and pipeline designCalculate oil recovery either Calculate oil recovery either

from natural depletion or from from natural depletion or from recovery techniques such as recovery techniques such as waterflooding and gas-waterflooding and gas-injection processesinjection processes

InjectionWell

Separation andStorage Facilities Production Well

1 2Oil Zone Oil Bank /Miscible Front

2

HC GasInjectionfrom Pipelineor Recycle

1

InjectionWell

Separation andStorage Facilities Production Well

11 22Oil Zone Oil Bank /Miscible Front

2

HC GasInjectionfrom Pipelineor Recycle

1

Variation of Oil Viscosity Variation of Oil Viscosity O

il Vi

scos

ityO

il Vi

scos

ity

T = constantT = constant

PPbb

Single Phase FlowSingle Phase FlowTwo Phase FlowTwo Phase Flow

Gas Out of Gas Out of SolutionSolution