In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO₂ injection well (IW) and CH₄ production well (PW) are established, aiming to explore the behavior of free gases after CO₂ is injected into the depleted Wufeng–Longmaxi shale. The results indicate the free CH₄ or CO₂ content in the shale fractures/matrix is invariably heterogeneous. The CO₂ involvement facilitates the ratio of free CH₄/CO₂ in the matrix to that in the fractures declines and tends to be stable with time. Different combinations of IW–PWs induce a difference in the ratio of the free CH₄ to the free CO₂, in the ratio of the free CH₄/CO₂ in the matrix to that in the fractures, in the content of the recovered free CH₄, and in the content of the trapped free CO₂. Basically, when the IW locates at the bottom Wufeng–Longmaxi shale, a farther IW–PWs distance allows more CO₂ in the free phase to be trapped; furthermore, no matter where the IW is, a shorter IW–PWs distance benefits by getting more CH₄ in the free phase recovered from the depleted Wufeng–Longmaxi shale. Hopefully, this work is helpful in gaining knowledge about the shale-based CO₂ injection technique.

在这项工作中，开发了一种新型的热-液压-机械（THM）耦合模型，其中嵌入了储层性质的真实地质参数。因此，建立了9种CO ₂注入井（IW）和CH ₄生产井（PW）方案，目的是探索将CO ₂注入贫化五峰—龙马溪组页岩后的游离气行为。结果表明，页岩裂缝/基质中游离CH ₄或CO ₂含量始终是非均质的。CO _2的参与促进了游离CH ₄ / CO ₂的比率随着时间的推移，基质中的裂缝逐渐减少并趋于稳定。IW–PW的不同组合会导致游离CH ₄与游离CO ₂的比率，基质中的游离CH ₄ / CO ₂的比率与裂缝中的游离CH ₄的比率之间的差异。 CH ₄和捕获的游离CO ₂的含量。基本上，当IW位于Wufeng–Longmaxi页岩底部时，更远的IW–PWs距离可以捕获更多自由相中的CO ₂。此外，无论IW在哪里，获得更多的CH _4都会缩短IW–PW的距离从枯竭的五峰—龙马溪页岩中回收的游离相。希望这项工作有助于获得有关基于页岩的CO ₂注入技术的知识。