voidage factor calculation for water injection optimization

[ahmedj9579]

Dear PET friend
Actually we have one oil well that produce with water injection in order to maintain reservoir pressure.(one oil producer and one water injector).
After 8 year producing without injection, the Pr decrease dramatically, so we start injection water from another well. after 4 year injection (water BT), we start produce water and oil and in the same time the Pr increase again.
I need to optimize the injection rate of the injector well, so please could you help me to calculate the voidage factor in order to replace this loss of pressure (practical method).
Best regards

[Shakespear]

Are you using reservoir simulation ?

Also look at this

[link Point to another website Only the registered members can access]

[ahmedj9579]

thank you very much.
actually we didn't use any simulation, but could we perform some curve to deduct this isuue?
like Pr vs cumuls oil in excel?

[DAH7542]

This is a very simple case since you have just one pair of injector/producer. The required injection rate to keep the reservoir pressure the same over time must satisfy a Voidage Replacement Ratio (VRR) equal to 1:

Voidage = total fluid withdrawal = qw*Bw + qo*Bo + (GOR - Rs)*qo*Bg
Replacement = water injection + natural water influx = qi*Bw + We
VRR = Replacement / Voidage

So you only need to figure out what the aquifex influx is and then calculate the injection rate (qi) required to replace the total withdrawals or Voidage, i.e., you have to solve for qi given a VRR = 1.

The previous methodology can be readily applied. However, there is another method much more simple. It's actually a rule of thumb that is widely applied in the company I work for. This rule of thumb states that the require cummulative injection volume per year must be 10% of the Pore Volume under waterflooding.

I've calculated required injection rates using both methodologies and they provide similar results.

As a third suggestion, if you have a numerical simulator you could specify a well control for pressure maintenance, in ECLIPSE this can be done by using the keyword GPMAINT (see Reference Manual).

[ahmedj9579]

Many thanks, but with this equation we supposed that we still with the same reservoir pressure that we deal with actually? right?
means, i need to idntify how much should i injected to return back to the same initial reservoir pressure?
Is it possible?
regards

[ahmedj9579]

dear DAH7542, i didn't recognise your second suggestion : [there is another method much more simple. It's actually a rule of thumb that is widely applied in the company I work for. This rule of thumb states that the require cummulative injection volume per year must be 10% of the Pore Volume under waterflooding.]
How can i get Pore volume under waterflooding?
regards

[DAH7542]

Dear ahmedj9579, you can get an estimated value of pore volume under waterflooding from different sources, including:

1. Traditional mapping and/or volumetric calculations
2. Interwell Tracer Test (take a look at "ZEMEL, B. Tracers in the oil field. Elsevier, 1995" and "SPE 7076")
3. Simulation

[ahmedj9579]

thank you very much, do you have an excell sheet of this VRR for water injection surveillance?
this will be very helpfull.
many thanks for your support

[ahmedj9579]

dear Pet people could you please help me to modelize using MBAL software one producer and one injector from the same tank.
i need step to follow because im not familiraze with this software.
my target is the Optimum water injection rate that i need in order to maintain reservoir presssure / produce more.
many thanks

[vinomarky]

Sorry to say, but it's all fairly simple. Unless you are doing delicate pressure balance for gas/oil/water rim stabilization etc, you simply want to inject as much water as you can without (a) fracturing your reservoir or (b) causing oil to be pushed outside of the producer gathering pattern. Maintaining voidage ratio of 1 etc is fine as a minimum, but if you can inject more, you should - your production will then increase and your VRR will settle back to approach 1.0 again.