Supercritical carbon dioxide (SC-CO₂) fracturing can form more complex fracture network and avoid reservoir damage, making it a lucrative alternative to hydraulic fracturing in shale gas reservoirs. This study establishes a two-dimensional dynamic filtration model of SC-CO₂ fracturing, which considers stress sensitivity, fluid adsorption, dynamic changes of fluid physical parameters, and coupled fracture propagation. According to the established model, the dynamic filtration of fracture elements and matrix pressure variation in fracture propagation are simulated and analyzed. And the influence of dynamic and static filtration model, constant and variable SC-CO₂ physical parameters, and fluid types in the filtration areas on the calculation results, as well as the effects of stress sensitivity and fluid adsorption on the filtration process are analyzed. The results show that during the fracturing process, fracture elements’ average filtration rate gradually drops and finally becomes stable, while the cumulative filtration volume increases nearly linearly. The static filtration model of uncoupled fracture propagation or the simplification of fluid in the filtration areas to SC-CO₂ single phase provides the reduction of calculation results, while constant SC-CO₂ physical parameters or the fluid simplification to the methane (CH₄) single phase have the opposite effect. Stress sensitivity can accelerate the filtration, while fluid adsorption can slow down the filtration. The influence of stress sensitivity is maximal at the middle stage of fracturing, while the influence of fluid adsorption weakens with time. This study's findings have important guiding significance for the optimal design and field application of SC-CO₂ fracturing in shale gas reservoirs. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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页岩气藏超临界二氧化碳压裂滤失规律数值研究

超临界二氧化碳（SC-CO ₂）压裂可以形成更复杂的裂缝网络并避免储层损坏，使其成为页岩气储层水力压裂的有利可图的替代方案。本研究建立了SC-CO ₂压裂二维动态渗滤模型，考虑应力敏感性、流体吸附、流体物理参数动态变化、耦合裂缝扩展等因素。根据建立的模型，对裂缝扩展过程中裂缝要素的动态渗滤和基质压力变化进行了模拟分析。以及动态和静态过滤模型、恒定和可变SC-CO _{2 的影响}分析了物理参数、过滤区流体类型对计算结果的影响，以及应力敏感性和流体吸附对过滤过程的影响。结果表明，在压裂过程中，压裂单元的平均滤失率逐渐下降并最终趋于稳定，而累积滤失量几乎呈线性增加。非耦合裂缝扩展的静态过滤模型或过滤区流体简化为 SC-CO ₂单相提供了计算结果的减少，而恒定的 SC-CO ₂物理参数或流体简化为甲烷（CH ₄) 单相有相反的效果。应力敏感性可以加速过滤，而流体吸附可以减慢过滤。压裂中期应力敏感性影响最大，流体吸附影响随时间减弱。该研究成果对页岩气藏SC-CO ₂压裂优化设计及现场应用具有重要指导意义。© 2021 化学工业协会和 John Wiley & Sons, Ltd.