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....