Average Reservoir Pressure in a Material Balance

[Chee Koh Peh]

Guys,

I performing a few material balances at the moment and I am estimating SBHP from some individual well buildup tests (the usual method), however some of the buildup tests do not look valid.

Has anyone performed a material balance for an oil reservoir using FBHP? I know Fekete pioneered the FBHP Gas Material balance? Has this been extended to oil reservoirs?

Otherwise has anyone had any experience or attempted to work backwards from FBHP to a SBHP, yes this is very unusual, and fraught with danger, but a long shot!

Thanks

Chee Koh Peh

[vinomarky]

I believe that the Fekete FAST FMB (flowing material balance) approach also can be applied to oil - I've only ever applied it to gas though so can not say definitively.

Edit: Found the following info in the FAST RTA Help docs;
F.A.S.T. RTA™ can be used in both oil and gas reservoirs. All analyses (typecurves, analytical models) can be used in RTA if the fluid system in the reservoir is single phase. For oil, that means it must be undersaturated or the pressure above the bubble point. Multiphase oil systems can be analyzed using the Numerical Model. In oil reservoirs, PVT properties and relative permeability data are extremely important: These include Formation Volume Factor (FVF), viscosity, compressibility and bubble point pressure. For multiphase oil systems, user defined relative permeability and PVT properties (if available) should be entered into the Advanced Properties section in RTA. When analyzing oil reservoirs in F.A.S.T. RTA™, it is important to have good flowing pressure data.

[darcyoil]

I just did an FMB on oil (must admit I had excellent PVT data), using Fekete's RTA software, and I got to within 2% of volumetric estimates. Not bad!!!! Pretty much matched on Blasingame and Agarwal-gardner as well

[Chee Koh Peh]

Darcy Oil,

Was this for a single well of a field?

If for a field how did you average the flowing bottom hole pressure within the field?

Thanks

Chee Koh Peh

[ahmedm]

interesting ..........

i think in this case use the volumetrics till you have more pressure data
ask for RFT for the new wells for example
maybe you can use the available data so far
you can juist try several pressure decline curves till you get resonable number (recovery mechanism , how it should look
if you have aquifer lets say)
you can play around till you get a number you can go with


hope this can give you a start point to go with

Ahmed Al-Alawi

[Shakespear]

Have you seen this?

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[darcyoil]

Chee Koh Peh: It was a one-well pool. But if you have more well, switch on the bubble map and you'll see if there is significant overlapping of drainage radii or not.

[mubeshar786]

Dear Bro
I am doing graduation thesis and my title is "Flowing Material Balance for the evaluation of gas reservoir". The problem is Its really hard to find some material on it. Can you please share some material relating FMB for gas reservoir (any kind of material). It will be very helpful for me. I shall be very thankful to you.

[vinomarky]

[link Point to another website Only the registered members can access] 3/4 of the way down the page there is a Flowing Material Balance section

And a video;

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[Shakespear]

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

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

[Chee Koh Peh]

Shakespear and Vinomarky....You beat me to it! Great references.......

Dear mubeshar786,

Yes the Flowing Material Balance works with single phase i.e. all fluids or gas, and you need to have PSS flow (i.e. stabilized boundary dominated flow) as you cannot calculate OOIP OGIP if flow is still transient.

Fekete notes and papers are the leading edge in this technique and should give you a sound theoretical basis.

Personally what I like about Fekete is the ability to model PSS Aquifer effects. The overestimation of gas reserves (P/Z Plot) due to mistaking the early time data as volumetric depletion is more common than you think. As a reserve auditor, in the absence of Fekete software,, I would use 60-65% RF for proved (P1) gas reserves, unless the client could show me conclusive evidence that no Aquifer exists. Another thing to note is that gas reservoirs under waterdrive can be very rate sensitive and this can mask the effect of the Aquifer....


Rgrds

Chee Koh Peh....

[mubeshar786]

Dear vinomarky
Thank you very much for your sharing. It was really a great material.