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.

Shale gas plays a far-reaching role for meeting the worldlyincreasingenergy demand; however, shale gas development exhibits variable situationsfor a same geological formation at different sedimentary locations,for example, Wufeng-Longmaxi shale. This work introduced threeshale gas parameter wells-target strata of Wufeng-Longmaxishale-aiming to explore the diversity of reservoir characteristicsand its implication. Herein, the mineralogy, lithology, organic mattergeochemistry, and trace element analyses of the Wufeng-Longmaxiformation in the southeast Sichuan Basin were evaluated in detail.Meanwhile, this work analyzed the deposit source supply, originalhydrocarbon generation capacity, and sedimentary environment of Wufeng-Longmaxishale. The results show that abundant siliceous organisms may be involvedin the shale sedimentation process in the YC-LL2 well. Besides, thehydrocarbon generation capacity of shale in the YC-LL1 well is betterthan that in the YC-LL2 and YC-LL3 wells. Moreover, the Wufeng-Longmaxishale in the YC-LL1 well was formed in a strongly reducing and hydrostaticenvironment, while that in the YC-LL2 and YC-LL3 wells is in a relativelyweakly redox environment with poor conditions to preserve organicmatter. Hopefully, this work offers salutary information for developmentof shale gas from a same formation but sedimented from different locations.

Shed structures are an important engineering method for mountain highways to resist rockfall impacts. Research on the rockfall impact response is very important to the design of rockfall disaster protection structures to shed cave structures. To explore the impact difference caused by different rockfall shapes, five mortar ellipsoids were fabricated with different shapes by 3D printing the falling stone mould. Laboratory experiments were carried out to study the impact effect of five different shapes of falling stones on the sand cushion. Different shapes of rockfall correspond to different impact forces. The tip ellipsoid (D1 and D2) is the smallest, the sphere (D3) is the second, and the flat ellipsoid (D4 and D5) is the largest. The fitting analysis of the impact force results of the laboratory experiment showed that the impact of the falling height on the impact force was relatively independent and did not change with the shape of the falling rock. Then, based on the impact force of the sphere falling rock, a calculation formula of the impact force with the introduction of the shape factor was obtained, and it was compared and verified with the test results from other studies. To study the applicability of the formula in the actual engineering scale, a numerical model was established by ANSYS. After verifying the reliability of the numerical model, the impact process of a large energy level was simulated. According to the simulation results, the rationality of the formula proposed in this paper is further verified, which guides the actual rockfall impact prevention and control engineering.