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The premise of this research is the concept , development , and application of an approximate relation for the material balance of abnormally -pressured gas reservoirs . The approximation is formulated directly from the rigorous material balance for the case of an abnormally -pressured gas reservoir .
The primary assumption in this derivation is that WGp <1 or Ce (p ) (pi -p ) <1 . Further , we can proceed by assuming that W is either constant or some arbitrary function . If we assume W=constant , then the following form results :
At first glance there may be concern that this approximation is not sufficiently valid for field applications however , we have shown this relation to be an extraordinarily accurate approximation of the rigorous material balance .
This result is suited not only for use as a characteristic model , but also for use as a data analysis mechanism (i .e . , this result is used to develop a suite of analysis plots , plotting functions , a type curve , etc . ) .
In this work we provide the following new results :
1 ) A suite of 6 (six ) plotting functions based on the p /z -Gp2 material balance model .
2 ) A suite of 4 (four ) p /z -Gp performance plots which are used to calibrate analysis .
3 ) A new type curve in terms of a dimensionless pressure function (pD= (pi /zi -p /z ) /pi /zi ) versus a dimensionless cumulative production function (GpD=Gp /G ) , where the type curve solution is based on the new p /z -Gp^2 (a quadratic material balance ) model . |
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