Practical use of well test deconvolution

Abstract

Abstract Deconvolution transforms variable rate pressure data into a constant rate initial drawdown with a duration equal to the total duration of the test. It yields directly the corresponding pressure derivative, normalized to a unit rate. It is not a new interpretation method, but a new tool to process pressure and rate data in order to obtain more pressure data to interpret with conventional techniques. Although deconvolution has received much attention since 2001 following the publication of a stable algorithm by von Schroeter, Hollaender, and Gringarten, its use by practicing engineers is still limited. One reason is limited access to the algorithm, which had only recently become available in commercial well test analysis software products. The other is concerns on how deconvolution should be used and how reliable it is. As a result, few examples of practical applications of well test deconvolution are available in the literature. This paper illustrates various uses of deconvolution in tests of short and long durations. Examples include DST's with erroneous rates, which deconvolution is able to correct; and data from permanent downhole pressure gauges in vertical and horizontal wells, where deconvolution shows compartmentalization and recharge from other layers, which could not be seen in the original data. Recommendations on how to perform deconvolution and how to verify deconvolution results are also provided. It is hoped that this paper will encourage well test interpreters to use deconvolution confidently as part of the well test analysis process.