This paper describes a new method for estimating averagereservoir pressure from long pressure buildup data based onthe classical Muskat plot. Current methods for estimatingaverage reservoir pressure require a priori information aboutthe reservoir and assume homogeneous reservoir properties, oremploy empirical extrapolation techniques.The new method applies to heterogeneous reservoirs andrequires no information about reservoir or fluid properties.The idea of the method is to estimate from the pressurederivative the first few eigenvalues of the pressure transientdecay modes. These values are characteristic of the reservoirand fluid properties, but not of the pressure history or welllocation in the reservoir. The smallest eigenvalue is used toextrapolate the long time behavior of the transient to estimatethe final reservoir pressure. The second eigenvalue can beused to estimate the quality of the estimate.Numerical tests of the method show that it estimatesaverage reservoir pressure accurately, even when the reservoiris heterogeneous or when partial flow barriers are present.Examples with real data show that the behavior predicted bythe theory is actually observed.We expect the method to have value in reservoir limitstesting, in making consistent estimates of average reservoirpressure from permanent down-hole gauges, and incharacterizing complex reservoirs.
展开▼
