Density-based rate-time production analysis of unconventional gas reservoirs under gas slippage and desorption

Accounting for gas-slippage and desorption effects is a critical step towards the reliable analysis of production performance in unconventional gas systems. This study demonstrates how to account for gas slippage and gas desorption effects in gas reservoirs using a density-based approach of analysis - an approach recently proposed for analyzing unsteady state flow of natural gas reservoirs. Gas-slippage and gas desorption models are incorporated into the original density-based approach by modifying the definitions of depletion-driven variables which are the basis of the density-based type of analysis. The proposed modification of the original approach successfully enables associated analysis techniques to be applicable to natural gas reservoirs with gas slippage and absorbed gas. Results indicate that by modifying the definitions of the depletion-driven variables, the density approach can effectively and successfully capture the effects from gas slippage and desorption. It is shown that gas flow rate can be successfully predicted by rescaling liquid solution with the modified density-based variables. This work illustrates the methodology required to do so and its application to production data prediction analysis for unconventional assets.