9/13/2010

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Surface Production OperationsENPE 505

Hassan Hassanzadeh

EN B204M

hhassanz@ucalgary.ca

2

Review of Fluid Properties

• describe various properties of reservoir

fluids and utilize these properties in

common production engineering

calculations.

Learning objectives

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3

Reservoir fluid properties

• classification of reservoirs fluids• density• gas compressibility factor• gas formation volume factor• isothermal gas compressibility• gas viscosity• oil gravity• gas-oil ratio• oil formation volume factor• isothermal oil compressibility• oil density• oil viscosity• surface tension• water formation volume factor• gas solubility in water• brine viscosity• water isothermal compressibility

4

P-T Diagram

Cricondentherm

Cricondenbar

Quality lines

Critical

point

Pre

ssu

re

Temperature

Liquid

Gas

5%

50%

70%

90%

100%

30%

Two-phase

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5

Oil Reservoirs

• Ordinary black oil• Low-shrinkage crude oil• High-shrinkage (volatile) crude oil• Near-critical crude oil

Properties exhibited by the crude oil, including physical properties, composition, GOR, appearance, and pressure-temperature phase diagrams.

Critical

point

Pre

ssure

Temperature

Saturated

oil reservoir

Undersaturated

oil reservoir

6

Gas Reservoirs

• Retrograde gas-condensate

• Near-critical gas-condensate

• Wet gas

• Dry gas

Pre

ssure

critical

point

Temperature

Two-phase

GOR: 60000-100000

API: above 60

Color: like waterwet gas

dry gas

GOR: above 100000

API:

Color:

GOR: 8000-70000 SCF/STB

API: above 50

Color: Liquid is water-whiteretrograde

gas reservoir

Reserv

oir

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7

n = number of moles of gas, lb-moleR = the universal gas constant which, for the above units, has thevalue 10.730 psia ft3/lb-mole °R

Properties of natural gases

ZnRTpV =

ZRT

pM

V

m

M

ZRT

V

mZRT

VM

mp

==

=

=

ρ

p = absolute pressure, psiaV = volume, ft3

T = absolute temperature, °R

M = molecular weight, lb/lb-mol

volumeIdeal

volumeActual=Z

Z

P

T=cte1

8

Properties of natural gases

∑=

=N

i

iiave MyM1

( )( )( )( )mole-SCF/lb 4.379

7.14

4606073.1011=

+==

SC

SCSC

p

ZnRTV

Mave = apparent or average molecular weight of a gas mixtureMi = molecular weight of the ith component in the mixtureyi = mole fraction of component i in the mixture

97.28

ave

Air

ave

Air

g

g

M

M

M===

ρ

ργ

Average MWAverage MW

Standard volume per moleStandard volume per mole

Specific gravitySpecific gravity

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9

Gas mixtures

• Compressibility factor from pseudocritical

properties ppc and Tpc

Sutton correlation (0.57< γ<1.68)

26.30.1318.756 ggpcp γγ −−=20.745.3492.169 ggpcT γγ −+=

pcpr ppp /=

pcpr TTT /=

10

Pseudo-critical properties of gases

Standing-Katz Compressibility Factor Chart

0.5 1.8Gas gravity

300

400

500

600

700

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11

Correction for impurities

Wichert and Aziz correction method for CO2 &H2S (1972 )

( ) ( )[ ] ( )4

2

5.0

2

6.1

22

9.0

22 15120 SHSHCOSHCOSH yyyyyy −++−+=ε

( )( )εε

SHSHpc

pcpc

pcpcpcyyT

TppTT

22 1 ,

−+

′=

′−=′

Wichert and Aziz correlation have an absolute error 0f 0.97% over154<p(psia)<7026 & 40<T(oF)<300Good for mole % of CO2<54.4% & H2S<73.8%

Carr-Kobayashi-Burrows correction for N2, CO2 & H2S (1954)

222

222

170600440'

25013080

NSHCOpcpc

NSHCOpcpc

yyypp

yyyTT

−++=

−+−=′

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Gas formation volume factor

It relates the volume of gas in the reservoir to the volume

on the surface (SC). It is generally expressed in either ft3/SCF or bbl/SCF.

( )( )( )( )( )

/SCFft 02827.046060

7.14

,

, 33

p

zT

p

TZ

pT

Tzp

p

nRTz

p

nRTz

SCFV

ftVB

ressc

resressc

sc

scsc

res

resres

sc

resg =

+====

In terms of bbl/SCF we have

SCF

bbl

p

ZT

ft

bbl

p

ZTBg 00504.0

615.5

1

SCF

ft 02827.0

3

3

==

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Isothermal compressibility

• The change in volume with pressure for gases under

isothermal conditions is called isothermal gas

compressibility.

at isothermal condition we have p

Z

p

ZnRTV ×== constant

T

gdp

dV

Vc

−=

1

pV

dp

dZ

ZV

pp

ZnRT

dp

dZ

Zp

ZnRT

p

ZnRT

dp

dZ

p

nRT

dp

dV 11112

−=

−

=−=

pdp

dZ

Zdp

dV

V

111−=

dp

dZ

Zpcg

11−=

pcg

1=For an ideal gas .

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Gas viscosity

• The Lee-Gonzalez-Eakin Method (1966)

( )

( ) ( )

XY

MTX

TMTMK

ZTpM

XKY

g

2.04.2

01.0/9865.3

19209/02.04.9

/104935.1

10exp

5.1

3

4

−=

++=

+++=

×=

×=

−

−

ρ

ρµ

ρ, in g/cc, p, in psia, T, in oR

9/13/2010

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Review of crude oil properties

Pressure (psia)

pb0

600

0 35002500

600 SCF/STB

RS

Initia

l pre

ssu

re

Solution gas oil ratioSolution gas oil ratio

From Lab data or Correlations

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Solution gas oil ratio

• Standing correlation (Beggs)

psia.in p F,in

0125.000091.0

pp ,1018

o

b

204.1

=

−=

≤

×=

T

APITY

pR

g

Ygsg

γ

Absolute error 4.8%

130<pb<7000 psia100<T<258 oF

20<GOR<1425 SCF/STB16.5<API<63.80.59<γ<0.951.024<Bo<2.05 bbl/STB

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Formation volume factor

From Lab data or Correlations

2500

pressure

Bo

1.4 bbl/STB

3500 psia

Initia

l pre

ssu

re

Bu

bb

le p

oin

tp

ressu

re

0

1.00

Standing correlation (Beggs)

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Oil formation volume factor

Standing correlation (Beggs)

( )[ ]ppcBB

T

T .RF

FB

boobo

o

g

s

o

−=

>

=

≤+

=

+=

exp

pbpfor

psia.in p F,in

pp 251

000147.0972.0

o

b

5.0

175.1

γ

γ

Absolute error 1.17%

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19

31x10-6<co <6600x10-6 psi-1, 500<p<5300 , psia, 763<pb<5300 psia

78<T<330 oF, 1.5<GOR<1947 SCF/STB, 6<API<52, 0.58<γ<1.2

Isothermal oil compressibility

T

op

V

Vc

∂

∂−=

1

( )

bpp ),ln(262.0)ln(455.0

)ln(390.0)ln(395.0)ln(43.1664.0ln

<+

++−−−=

APIR

Tppc

sob

bo

VillenaVillena--LanziLanzi

Vasquez & BeggsVasquez & Beggs

( ) ( ) b

5 pp ,10/143361.1211802.175 >×−+−+= pAPITRc gsobo γ

126<p<9500 , psia, 78<T<330 oF, 9.5<GOR<2199 SCF/STB,

15.3<API<59.5, 0.511<γ<1.351, 1.006<Bo<2.226 bbl/STB

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Oil viscosity

pb

Oil v

isco

sity

pressure

Egbogah’s correlation for dead oil bpp ≤

Beggs and Robinson correlation for live oil

9/13/2010

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21

Oil viscosity

Vasquez and Beggs for bpp >

22

Review of formation water properties

McCain correlation for Bw

9/13/2010

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Review of formation water properties

McCain correlation for Solution gas water ratio

( )285854.00840655.010

−−= ST

swp

sw

R

R

24

Water isothermal compressibility

Osif correlation p>pb:

McCain correlation p<= pb:

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25

Formation water viscosity

McCain correlationB

w AT=1µvalid for p<=15000 psia and 86<T<167 ºF.

26

Formation brine properties

• Fresh water S<1,000 ppmm

• Slightly saline water 1,000<S<3,000

• Moderately saline water 3,000<S<10,000

• Highly saline water 10,000<S<35,000

• Sea water 35,000

• Saturated saline water 300,000