PDA

View Full Version : Calculation of RF in an undersaturated oil reservoir



LOST
12-09-2009, 02:17 PM
Dear engineers,
I want to calculate Recovery Factor of an oil field,
For this I must have Cw. Cf
How can I calculate Cw (compressibility factor) with following information:

Ca(calcium): 2000 ppm
Na(sodium): 218000 ppm
Wt: 73.6 pcf
pH: 6.4
Pr: 4219 psi @ 2877m Reservoir pressure.

and for Cf (rock compressibility):
porosity = 0.2

and final, can I use this formula for RF:

RF= Ce*Dp*(Boi/Bo)
Ce: effective compressibility
Dp: Pi-P
Bo: OFVF

thank you

ivan_aljeburi
12-10-2009, 02:39 PM
Hi bro

1. You can calculate water compressibility using Cw charts for isothermal compressibility or by using an empirical correlation ignoring water salinity.

2. Formation compressibility can be calculated using two methods : Hall and Newman

Hall
Cf=(1.782/porosity^0.438) x 10-6 in psi-1

Newman's method take into account type of the reservoir rock (sandstone, limeston)
My advice is to use Hall

3. You can use this formula just to calculate RF until pressure reaches Pb. In other words you should use Bo(pb) in that equation.

LOST
12-10-2009, 07:44 PM
Thank you IVAN,
Is there any equation for Cw calculation using salinity of water?

vinomarky
12-11-2009, 02:20 PM
This is all of course pure expansion drive - assuming no water support.....

ivan_aljeburi
12-11-2009, 05:54 PM
You can use some PVT softwares... i think you have some equations in "Reservoir Engineering Handbook" by Tarik Ahmed.. you can download this book from

Best regards

LOST
12-12-2009, 08:29 AM
thank you for your kind attention.
would you please tell me how to calculate RF up to some abandonment pressure.
using this additional data:
Oil API: 21
Psat: 2490 psi

ahmedm
12-16-2009, 10:34 PM
my friend,

for api you can use the equation for gas-in-solution drive api equation
for cf you can use hall's correlation
and for cw you can use graph correlation inputs are temp, press and salinity



i did some summary on pvt correlations i will try to upload it

thanks

LOST
12-17-2009, 11:01 AM
THANK U DEAR AHMED,
i am waiting for that

LOST
12-19-2009, 03:58 PM
Hi bro

1. You can calculate water compressibility using Cw charts for isothermal compressibility or by using an empirical correlation ignoring water salinity.

2. Formation compressibility can be calculated using two methods : Hall and Newman

Hall
Cf=(1.782/porosity^0.438) x 10-6 in psi-1

Newman's method take into account type of the reservoir rock (sandstone, limeston)
My advice is to use Hall

3. You can use this formula just to calculate RF until pressure reaches Pb. In other words you should use Bo(pb) in that equation.


what is the meaning of this equation?
Cf=(1.782/porosity^0.438) x 10-6 in psi-1

it means that when porosity increases, Cf decreases. is it true?
but more porose rocks must have more Cf.!!!!!!!!!!!!!!!!!????

ivan_aljeburi
12-21-2009, 08:22 PM
Yes, exactly...But keep in mind that Cf is a critical issue when you have samll porosity, because in small changes of porosity Cf will rapidly change.