Abstract

Transport of gas in a shale reservoir may be greatly different from that in a conventional reservoir. This is primarily due to shale's small pore size, extremely-low permeability and presence of adsorbed gas. It is also because the low permeability formation matrix is intervened with highly conductive hydraulic fractures. Although some of the involved mechanisms such as gas molecule slippage (Klingenberg effect) and non-Darcy flow (Forchheimer effect) have been extensively studied since early pioneering works decades ago, there is still a need for improved fundamental understanding and proper quantification. This paper clarifies some of the confusions floating around the topic of non-Darcy gas flow. A comprehensive model of gas transport in shale reservoirs, including contributions due to gas molecule slippage, inertial forces and gas desorption is constructed directly from the fundamental laws of mass, momentum and energy conservation. The model is then applied to simulate production from hydraulically fractured shale gas reservoirs.

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