A multi-scale and multi-mechanism coupled model for carbon isotope fractionation of methane during shale gas production

作者：Jun Wang, Fangwen Chen, Wenbiao Li, Shuangfang Lu, Shengxian Zhao, Yongyang Liu, Ziyi Wang · 发表于：Petroleum Science · 年份：2025 · DOI：10.1016/j.petsci.2025.03.034 · 被引用次数：14 · 研究领域：Hydrocarbon exploration and reservoir analysis、Atmospheric and Environmental Gas Dynamics、Methane Hydrates and Related Phenomena

Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells. Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale, complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions, and complex and variable production regimes of shale gas wells. Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production, with the fractionation characteristics of each stage associated with the pore structure, gas in place (GIP), adsorption/desorption, and gas production process. This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques. A reservoir-scale carbon isotope fractionation (CIF) model applicable to the production process of shale gas wells was developed for the first time in this research. In contrast to the traditional model, this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ 13 C 1 data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production. The results indicate that the diffusion and adsorption/desorption properties of rock, bottom-hole flowing pressure (BHP) of gas well, and multi-scale...