In this paper, we present a new deconvolution method that removes the dependency of the deconvolved constant-rate drawdown responses to the initial reservoir pressure. As is well known, particularly the late-time portions of the deconvolved responses from the recent pressure-rate (p-r) deconvolution algorithms are dependent on the initial reservoir pressure. A small error in the initial reservoir pressure could make a significant difference in the late-time portions of the deconvolved responses that can easily lead to an incorrect interpretation model, particularly misinterpretation of the boundaries. The new method presented is based on pressure-derivative data rather than pressure data that are used in all published deconvolution algorithms. Using pressure-derivative data in deconvolution leads to a nonlinear least-squares objective function that is different from those used in the earlier deconvolution methods and eliminates the dependency of the deconvolved responses to the initial reservoir pressure. Hence, the new method minimizes incorrect interpretation due to an error or uncertainty in the initial reservoir pressure.

We apply the new method to both simulated and field pressure-transient data sets. The results show that the new method offers a significant advantage over the earlier deconvolution methods for pressure transient test interpretation in cases where the initial reservoir pressure is unknown or uncertain.