A methodology for identifying and estimating desorption from Devonian shale gas production data is presented. The methodology can be used regardless of whether independent information about the existence of adsorbed gas is available. Several example cases are presented which indicate that, in certain situations, the presence of the desorption mechanism can be detected from a history match of production data.The accuracy of the parameter estimates used to describe the desorption process is also examined. Results indicate that the desorption parameters cannot be estimated accurately from production data; however, production fore.., casts based on history matches that include the effects of desorption are found to be more accurate than when desorption is not taken into account.

The feasibility of detecting and accurately estimating gas desorption parameters from a history match of Devonian shale well-test pressure data is examined. Both drawdown and buildup tests are analyzed, and based on the results of these analyses a desorption-specific well-test design is proposed. The results from a simulated desorptionspecific test suggest that it is possible to characterize gas desorption from a well test with reasonable accuracy, even when the effects of desorption are partially masked by wellbore storage and skin effects.