2_oil prop

8/19/2019 2_OIL PROP

1/38

BLACK OIL

PROPERTIES

8/19/2019 2_OIL PROP

2/38

Black Oil Properties

Important in Reservoir Engineering andProduction Engineering Calculations

Formation Volume Factor of Oil, B oSolution Gas-Oil Ratio, R sTotal Formation Volume Factor, B t Coe icient of Isot!ermal compressi"ilit#, c oOil Viscosit#, µ oInterfacial Tension, σ o

8/19/2019 2_OIL PROP

3/38

Solution Gas-Oil Ratio

T!e $uantit# of %gas& dissolved in %oil& atreservoir conditions

Treat as a t'o-component s#stem (ctuall# %gas& and %oil& consist of man#components, and composition of eac! p!asec!anges as pressure declines)

* ""l of oil at reservoir conditionsSplits into stoc+ tan+ oil and gas at standard

conditions

8/19/2019 2_OIL PROP

4/38

Solution Gas-Oil Ratio

e nition

.nits / scf0ST1

stock tank atsurfaceat producedoilof volumeconditionsstandardatsurfaceat producedgasof volume

= s R

8/19/2019 2_OIL PROP

5/38

Behavior of B o ith Pressure

8/19/2019 2_OIL PROP

6/38

Li!ui" Speci#c Gravit$% o

T!e ratio of t!e densit# of a li$uid to t!edensit# of 'ater at t!e same 2P,T3)

(PI gravit#

5.1315.141

−γ = o API

8/19/2019 2_OIL PROP

7/38

E&a'ple

T!e densit# of a stoc+-tan+ oil at 45 o F is6*)76 l"m0cu)ft) Calculate t!e speci cgravit# and (PI gravit#)

Speci c Gravit#

8217.037.62

25.51==

ρρ

=γ wo

o

8/19/2019 2_OIL PROP

8/38

E&a'ple

(PI gravit#

AP7.405.131

8217.0

5.141

5.1315.141

o

o API

=−=

−γ

=

8/19/2019 2_OIL PROP

9/38

Oil (or'ation )olu'e (actor

T!e volume of reservoir li$uid 2atreservoir 2P,T33 re$uired to produce one"arrel of stoc+-tan+ oil

.nits / res) ""l0ST1

Volume of reservoir oil is al'a#s "iggert!an stoc+-tan+ #ield

Reservoir li$uid contains dissolved gas)

8/19/2019 2_OIL PROP

10/38

Oil (or'ation )olu'e (actor

Value of B o a ected "#Evolution of dissolved gas 'it! reducedpressureE8pansion of li$uid 'it! reduced pressureS!rin+age of li$uid as temperature falls

T!e last t'o e ects are small, and tend too set eac! ot!er)

8/19/2019 2_OIL PROP

11/38

Behavior of B o ith Pressure

("ove t!e "u""le point pressure, B o increases slig!tl# as pressure is reduced

E8pansion of li$uid 2no gas evolved31elo' t!e "u""le point pressure, B odecreases

S!rin+age of oil as dissolved gas evolves (t atmosp!eric pressure, B o ≈ *)

8/19/2019 2_OIL PROP

12/38

Total (or'ation )olu'e (actor

9ot 'idel# used no'ada#sFound in some older ReservoirEngineering applications

( ) s sb g ot R R B B B −+=

8/19/2019 2_OIL PROP

13/38

Coe*icient of Isother'alCo'pressi+ilit$ of Oil

C!ange in volume per unit volume per psi

For li$uids, oil compressi"ilit# is almostconstant

T o P

V V

c

∂∂−= 1

8/19/2019 2_OIL PROP

14/38


Oil a"ove t!e "u""le point pressure, c o issmall and almost constant

Slig!tl# compressi"le li$uid

Separate varia"les and integrate

∫ ∫ −=

∂∂

−=2

1

2

1

1

V

V

p

p

o

T o

V

dV dP c

P V

V c

8/19/2019 2_OIL PROP

15/38


For c o small

( )

( )( )12121

212

e!p

ln

p pcV V

V V p pc

o

o

−−=−=−

( )( ) ( )

12

12

1

1212

11e!p

p pV V

V c

p pc p pc

o

oo

−−−≈

−−≈−−

8/19/2019 2_OIL PROP

16/38

Belo the Bu++le Point

:it! decreasing pressure, gas evolves andt!e li$uid s!rin+s

∂∂−

∂∂−=

T

s g

T

o

oo P

R B

P B

Bc

1

h f

8/19/2019 2_OIL PROP

17/38

Behavior of c o at ConstantTe'perature

8/19/2019 2_OIL PROP

18/38

8/19/2019 2_OIL PROP

19/38

Coe*icient of )iscosit$ of Oil

Increase in temperature causes decreasein viscosit#

ecrease in pressure ("ove "u""le point< decrease in viscosit#1elo' "u""le point< increase in viscosit#

$

8/19/2019 2_OIL PROP

20/38

Oil )iscosit$ at ConstantTe'perature

8/19/2019 2_OIL PROP

21/38

Initial Reservoir Pressure

(t initial pressure reservoir isSaturated< P r ≤ P ".ndersaturated< P r = P "

Saturated< free gas present in a gas cap)Initial Pressure > Saturation Pressure.ndersaturated / no free gas)

8/19/2019 2_OIL PROP

22/38

,n"ersaturate" Reservoir

Production trends, P r = P "Initiall# all gas dissolved in oilSingle p!ase li$uid containing all availa"le gasenters 'ell"ore

(s oil travels to surface gas evolvesProduced GOR > initial dissolved GOR >constantPressure declines rapidl# 2e8pansion of li$uid3

8/19/2019 2_OIL PROP

23/38


Production trends, P r ≤ P " (t t!e "u""le point, rst "u""le of gas evolvesInitiall#, gas does not ;o' / small "u""les%stic+& to sides of t!e poresOil entering 'ell"ore contains less dissolvedgas t!an initialProducing GOR falls slig!tl#)

8/19/2019 2_OIL PROP

24/38


Production trends, P r ≤ P " (s pressure continues to decline, gas "u""lescoagulate to form large "u""les, and gas;o's)

Gas ;o's more easil# t!an oil / GORincreases)Reservoir pressure declines slo'l#< gas inreservoir e8pands and maintains pressure)

8/19/2019 2_OIL PROP

25/38

Black Oil Pro"uction

8/19/2019 2_OIL PROP

26/38

Black Oil Pressure ecline

8/19/2019 2_OIL PROP

27/38

.ote

?ig! gas compressi"ilit# is a great sourceof energ# storage in t!e reservoir:it! oil removal, gas e8pands to ll up

void left 'it! onl# a small pressuredecline)It is "etter to +eep t!e gas in t!e reservoirt!an to remove it)

8/19/2019 2_OIL PROP

28/38

Esti'ation of (lui" Properties

Production a"ove "u""le pointProducing GOR ≈ constant > R s"Pressure declines rapidl#

1elo' "u""le pointProducing GOR increases rapidl#Pressure declines slo'l#

Can estimate R s" and "u""le pointpressure

8/19/2019 2_OIL PROP

29/38

Bubble Point Pressure

8/19/2019 2_OIL PROP

30/38

)olatile Oils

Same trends as for 1lac+ Oil ("ove "u""le point, pressure does notdecrease as rapidl#

C!ange of slope in pressure decline at"u""le point di icult to detect)1u""le point pressure !ard to identif#

8/19/2019 2_OIL PROP

31/38

Retro/ra"e Gas

("ove de' pointProducing GOR constant

1elo' de' pointProducing GOR increases "ecause li$uids are left in t!e

reservoir)e' point pressure cannot "e determined from

pressure decline data9o apprecia"le c!ange in slope at de' point)

8/19/2019 2_OIL PROP

32/38

Reservoir (lui" Stu"ies

etermine1u""le-point pressureFormation volume factor of oil

Solution gas-oil ratioTotal formation volume factorCoe icient of isot!ermal compressi"ilit# of oilOil viscosit#

@-factorFormation volume factor of gasGas viscosit#

8/19/2019 2_OIL PROP

33/38

Reservoir (lui" Stu"ies

Variation of separator conditions todetermine

Separator gasStoc+ tan+ gasStoc+ tan+ oil

8/19/2019 2_OIL PROP

34/38

Proce"ures

Composition measurementFlas! vaporiAation

i erential vaporiAation

Separator tests Viscosit# measurement

8/19/2019 2_OIL PROP

35/38

Sa'plin/

O"taining a representative reservoirli$uid sample is di icult '!en t!ereservoir is saturated

1ottom-!ole sampleSample o"tained at "ottom-!ole 2P,T3

Separator samplesSeparator oil and gas samples are recom"ined in t!e%correct& ratio

8/19/2019 2_OIL PROP

36/38

Co'position

i icult to determine e8act compositionof !undreds of di erent c!emical speciesin crude oilCompositions of C* / C4 usuall#determined?eavier components lumped in a CBpseudo-component)

8/19/2019 2_OIL PROP

37/38

8/19/2019 2_OIL PROP

38/38

(lash )apori0ation

2_oil prop

Documents