A Calculation Method for Material Balance of Shale Gas Reservoirs under Abnormally High Pressure Considering Modified BET Adsorption

doi:10.3969/j.issn.1006-6535.2022.02.011

Abstract

Abstract: Langmuir isothermal adsorption equation is usually used to characterize the amount of adsorbed gas in the material balance equation of shale gas, while the application conditions of Langmuir isothermal adsorption equation are not suitable for shale gas reservoirs under abnormally high pressure. To address the problems about the calculation of single-well recoverable reserves in shale gas reservoirs under abnormally high pressure, based on the basic principle of the material balance equation, a modified BET adsorption model was introduced to characterize the adsorption characteristics of shale gas with consideration of the triple effects (multilayer adsorption, supercritical adsorption and abnormally high pressure) of shale gas, and a material balance equation was established for shale gas reservoirs under abnormally high pressure considering the modified BET adsorption factor. The application of the study results to the analysis of single wells in actual blocks proved that the linear correlation coefficient of the model established in this paper was higher, and the model can not only calculate the controlled reserves of gas wells, but also calculate the free gas content and adsorbed gas content in the gas release range. According to the calculation results of this equation and the geological conditions of the actual reservoir, the construction conditions considered by the model in this paper are closer to the actual reservoir conditions. The study results play an important guiding role in the production management of shale gas reservoirs under abnormally high pressure.

Key words: shale gas reservoirs under abnormally high pressure, material balance calculation method, modified BET adsorption, multilayer adsorption, supercritical adsorption, dynamic forecast

CLC Number:

TE349

Zhang Chengwei, Cheng Shiqing, Zhou Wen, Zhang Teng, Jiang Ke, Zhu Lang, Xu Hao. A Calculation Method for Material Balance of Shale Gas Reservoirs under Abnormally High Pressure Considering Modified BET Adsorption[J]. Special Oil & Gas Reservoirs, 2022, 29(2): 77-82.

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