Techniques for History-Matching and Forecasting Tight Oil Reservoirs Compared

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTEC 208352, “Assessment of Rate-Normalization and Pressure-Deconvolution Techniques To History-Match and Forecast Production of Tight Oil Reservoirs Using a Physics-Based Rate-Time Model,” by Leopoldo M. Ruiz Maraggi, SPE, Larry W. Lake, SPE, and Mark P. Walsh, SPE, The University of Texas at Austin. The paper has not been peer reviewed. Rate transient analysis (RTA) is used routinely to analyze the production history of unconventional wells. Specifically, it is used to determine the time at the end of linear flow (time to depletion), estimate drainage volume, and predict the estimated ultimate recovery (EUR) of wells. RTA uses a rate-normalization technique to characterize how the well rate changes with a changing bottomhole flow pressure. However, rate normalization approximates a more-general technique known as pressure deconvolution. The complete paper evaluates and compares the performance of rate normalization and pressure deconvolution for both synthetic and tight oil examples. Overview The complete paper first presents the solution of the single-phase slightly compressible fluid-diffusivity equation for a certain set of idealized conditions. Second, the concepts of time superposition, convolution, deconvolution, and rate normalization are presented. Third, a numerical regularized exponential basis function inverse scheme is proposed for use in deconvolution. Fourth, the comparison of the rate-normalization and pressure-deconvolution techniques for a synthetic case are presented. Finally, the two methods are evaluated for tight oil wells. This synopsis will not include the many equations involved in these processes or detailed discussions thereof; instead, it concentrates on the work flow that the authors have developed, specifically its application to synthetic cases.