The sorption-corrected multiwell deconvolution method to identify shale gas reservoir containing sorption gas

Abstract

In the analysis of the pressure data acquired from a shale gas reservoir, the rate-normalized pressure (RNP) method has been widely used in the shale gas industry due to its simplicity. However, for sharply varying production rate and shut-in of a well, and for pressure-interfered data at a well, the RNP method gives erroneous results in evaluation of the reservoir characteristics. Meanwhile, the deconvolution method can overcome the limit of the RNP method for sharply varying data. However, because the deconvolution method is only applicable to a linear relationship in the pressure-rate data, it is not possible to analyze the pressure data acquired from adsorbed gas-contained shale gas reservoir. This data shows a nonlinear relationship because of the compressibility of desorbed gas which is a strong function of pressure.In this study, we newly proposed the sorption-corrected multiwell deconvolution method for correctly identifying the shale gas reservoir containing the adsorbed gas. This method was suggested to analyze not only sharply varying production rate but also pressure-interfered data acquired from the multiwell. With the use of this method, we evaluated and compared the effective permeability and the estimated ultimate recovery (EUR) of shale reservoir with RNP method that is currently applied in shale gas industry. From the results, it was concluded that the sorption-corrected multiwell deconvolution method was found to be an excellent methodology comparing to RNP method for analyzing pressure-interfered shale gas production data containing the adsorbed gas.