Mortar Dynamic Coupled Model For Calculating Interface Gas Exchange Between Organic And Inorganic Matters Of Shale

Shale gas has revolutionized the world energy in recent years. In this work, a mortar dynamic coupled model (MDCM) is successfully built for simulating gas transport from molecular motion in nanopores to highly permeable fractures. Results show that the production duration of MDCM can reach about tenfold that of a single medium model, which affords a microscale explanation for the long tail production. We also propose a two-stage process in the variation of the mass-exchange-rate with the pressure difference of organic matter and inorganic matter: it is nonlinear in Stage I, while shows a linear relationship in Stage II. Combined with theoretical analyses, numerical simulations and dimensional analyses, an effi-cient and practical relation for calculating the interface gas exchange in tail production is obtained. The relation offers a valuable tool for the gas transport properties in fractured shale and is finally validated by a gas expansion experiment. Better performance can be obtained in terms of accuracy and precision than the current model. These results stress the need for a change of paradigm from statistic to dynamic trans scale transport. The new insights into transport in the long-term shale gas production suggest new leads for the industry. (c) 2021 Elsevier Ltd. All rights reserved.