depletion drive calculations

7/25/2019 Depletion Drive Calculations

1/17

DEPLETION DRIVE CALCULATIONS

Depletion drive is the oil recovery mechanism herein the prod!ction o" the oil

its reservoir roc# is achieved $y the e%pansion o" the ori&inal oil vol!me ith a

ori&inal dissolved &as'

This drivin& "orm may also $e re"erred to $y the "olloin&

vario!s terms(

sol!tion &as drive)

dissolved &as drive)

internal &as drive'

In depletion drive reservoir* the principal so!rce o" ener&y is a res!lt o" &as li$er

"rom the cr!de oil and the s!$se+!ent e%pansion o" the sol!tion &as as the rese

press!re is red!ced' As press!re "alls $elo the $!$$le point press!re* &as $!$$le

li$erated ithin the microscopic pore spaces' These $!$$les e%pand and "orce the

oil o!t o" the pore space


2/17

Depletion drive cont,'

Solution gas drive reservoir.


3/17

Characteristics o" depletion drive reservoir

Pressure behavior: The reservoir press!re declines rap

contin!o!sly'Water production: The a$sence o" a ater drive means ther

little or no ater prod!ction ith the oil d!rin& the entire prod

o" the reservoir'

A depletion drive reservoir is characteri-ed $y a rapidly increa

oil ratio "rom all ells* re&ardless o" their str!ct!ral position'

reservoir press!re has $een red!ced $elo the $!$$le point

&as evolves "rom sol!tion thro!&ho!t the reservoir'


4/17

DD contin,

This drivin& mechanism is represented mathematically $y

DDI / N 01t 2 1ti34A

5here DDI is termed the depletion-drive index.

Segregation Drive. Se&re&ation drive 0&as6cap drive3 is the mechanism

displacement o" oil "rom the "ormation is accomplished $y the e%pansion

ori&inal "ree &as cap' This drivin& "orce is descri$ed $y

SDI / 7N m 1ti 01& 2 1&i341&i84A

here SDI is termed the segregation-drive index.


5/17

Water Drive.

5ater drive is the mechanism herein the displacement o" the oil is ac

$y the net encroachment o" ater into the oil -one' This mechanism is

$y the third term o" E+!ation

9969: or(5DI / 05e 25p 134A

here 5DI is termed the water-drive index.

Expansion drive index

;or !ndersat!rated oil reservoirs ith no ater in"l!%* the principal so

ener&y is a res!lt o" the roc# and "l!id e%pansion as represented $y the


6/17

Injected water drive index: The relative e""iciency o" the ater in


7/17

Note that "or a depletion drive reservoir !nder press!re maintenance op

&as in


8/17

Bt= Bo+ (Rsi Rs) Bg


9/17

Example1A com$ination6drive reservoir contains 9= >>ST1 o" oil initially in

place' The ratio o" the ori&inal &as6cap vol!me to the ori&inal oil vol!m

estimated as ='?@' The initial reservoir press!re is === psia at 9@=B;' Tprod!ced 9 >>ST1 o" oil* 99== >>sc" o" =': speci"ic &ravity &as*

ST1 o" ater $y the time the reservoir press!re dropped to ?:== psi' Th

PVT is availa$le(


10/17

Cont.

The "olloin& data is also availa$le(

Si / =' ?=* c / 9' @ 9=2 psi29* c" / 9 9=2 psi29

Calc!late(

0a3 the c!m!lative ater in"l!%)

0$3 the net ater in"l!%)

0c3 the primary drivin& indices at ?:== psi'


11/17

Solution

1eca!se the reservoir contains a &as cap* the roc# and "l!id e%

can $e ne&lected* i'e'* set c" and c / =' ;or ill!stration p!rpo

hoever* the roc# and "l!id e%pansion term ill $e incl!ded incalc!lations'

Part A. Cumulative water inlux

Step !. Calc!late c!m!lative &as6oil ratio Rp(


12/17

Solution cont..

Arranging MMB equation solve fo e.


13/17

Ne&lectin& the roc# and "l!id e%pansion term* the c!m!lative in"l!% is 9F*F== $$l'

Part B. Net water infux

!et "ater in#ux =epB"= $11%&'1 % = *,,l

Part C. Primary recovery indexes

Step 1. Calculate t-e parameter A , using Equa10

A = 1ex+21.+ + (11 1$) .0&3 = 1%41


14/17

Step ". Calc!late DDI* SDI* and 5DI $y applyin& E+!a$ove


15/17

Example &

The 1i& 1!tte "ield is a com$ination6drive reservoir' The c!rreservoir press!re is estimated at ?@== psi' The reservoir prodata and PVT in"ormation are &iven $elo(


16/17

eg& The "olloin& additional in"ormation is availa$le(

Vol!me o" $!l# oil -one / 9==*=== ac6"t

Vol!me o" $!l# &as -one / ?=*=== ac6"t

Calc!late the initial oil in place'


17/17

depletion drive calculations

Documents