Meyer Gabriel G, Shahin Ghassan, Cordonnier Benoît, Violay Marie
Laboratory of Experimental Rock Mechanics, School of Architecture, Civil & Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
European Synchrotron Radiation Facility, Grenoble, France.
Nat Commun. 2024 Sep 5;15(1):7753. doi: 10.1038/s41467-024-52092-0.
Geothermal projects utilizing supercritical water (≥400 °C) could boost power output tenfold compared to conventional plants. However, these reservoirs commonly occur in crustal areas where rocks are semi-ductile or ductile, impeding large-scale fractures and cracking, and where hydraulic properties are largely unknown. Here, we explore the complex permeability of rocks under supercritical conditions using mechanical data from a gas-based triaxial apparatus, high-resolution synchrotron post-mortem 3D imagery, and finite element modeling. We report a first order control of strain partitioning on permeability. In the brittle regime, strain localizes on permeable faults without necessarily increasing sample apparent permeability. In the semi-ductile regime, distributed strain increases permeability both in deformation bands and the bulk, leading to a more than tenfold permeability increase. This study challenges the belief that the brittle-ductile transition (BDT) marks a cutoff for fluid circulation in the crust, demonstrating that permeability can develop in deforming semi-ductile rocks.
利用超临界水（≥400°C）的地热项目相比传统电厂，发电量可提高十倍。然而，这些储层通常位于地壳区域，那里的岩石具有半延性或延性，阻碍大规模裂缝和破裂的形成，并且其水力特性很大程度上未知。在此，我们使用基于气体的三轴装置的力学数据、高分辨率同步加速器死后三维成像以及有限元建模，探索超临界条件下岩石的复杂渗透率。我们报告了应变分配对渗透率的一级控制。在脆性状态下，应变集中在渗透性断层上，但不一定会增加样品的表观渗透率。在半延性状态下，分布式应变会增加变形带和整体的渗透率，导致渗透率增加超过十倍。这项研究挑战了脆性-延性转变（BDT）标志着地壳中流体循环截止点的观点，表明在变形的半延性岩石中可以形成渗透率。
