Abstract A numerical model was developed to simulate heat extraction and flow behaviour of fractures under deep geological conditions by incorporating a real fracture morphology induced by supercritical carbon dioxide (ScCO2) injection. 3-D scanning technology was used to generate the geometry of the fracture in the model in order to provide a realistic reflection of the tortuous and rough fractures induced by ScCO2 fracturing. The fracture exhibits a tortuosity of 1.44 and a JRC (Joint Roughness Coefficient) of 14.6. The flow characteristics along the ScCO2-induced fracture was evaluated under different in-situ stresses and at high-temperature of 100 °C, by integrating coupled thermal-hydraulic (TH) processes into the model. In addition, the influence of shearing on aperture alteration and flow enhancement was evaluated using the model. The model accurately simulates the permeability characteristics at 100 °C and under varying confining pressures (20–60 MPa) and injection pressures (1–8 MPa) with more than 87% accuracy compared with the corresponding experimental results. The results indicate a non-linear pressure gradient over the highly varying aperture profile along the fracture. Furthermore, the orientation of flow channels and the streamline network heavily depends upon the aperture profile. The fluid injected at 20 °C into a narrow, tortuous fracture is heated to 100 °C while flowing along a distance 63% of the fracture length towards the outlet, whereas the heat transfer efficiency is decreased by 26% with the increase of injection pressure from 1 MPa to 8 MPa. The increase in confining pressure up to 60 MPa results in reduction of fracture permeability by 90% due to stress-induced fracture closure. Shearing of the fracture surface by 5% results in increments in mean aperture, outlet flowrate and average fracture permeability by 44%, 45% and 113%, respectively.

中文翻译：

---

高温高压条件下超临界二氧化碳诱导裂缝的孔径相关流动特性研究：数值研究

摘要 通过结合超临界二氧化碳 (ScCO2) 注入诱导的真实裂缝形态，开发了一个数值模型来模拟深部地质条件下裂缝的抽热和流动行为。3-D 扫描技术用于在模型中生成裂缝的几何形状，以便真实反映 ScCO2 压裂引起的曲折和粗糙裂缝。裂缝表现出 1.44 的曲折度和 14.6 的 JRC（接头粗糙度系数）。通过将耦合热液 (TH) 过程集成到模型中，在不同的地应力和 100 °C 的高温下评估了沿 ScCO2 诱导的裂缝的流动特性。此外，使用该模型评估了剪切对孔径改变和流动增强的影响。该模型准确模拟了 100 °C 和不同围压 (20-60 MPa) 和注入压力 (1-8 MPa) 下的渗透率特征，与相应的实验结果相比，准确率超过 87%。结果表明在沿裂缝高度变化的孔径剖面上存在非线性压力梯度。此外，流动通道和流线网络的方向在很大程度上取决于孔径轮廓。在 20 °C 下注入狭窄曲折裂缝的流体被加热到 100 °C，同时沿裂缝长度的 63% 的距离流向出口，而随着注入压力的增加传热效率降低 26%从 1 兆帕到 8 兆帕。由于应力诱导裂缝闭合，围压增加至 60 MPa 导致裂缝渗透率降低 90%。裂缝表面剪切 5% 导致平均孔径、出口流量和平均裂缝渗透率分别增加 44%、45% 和 113%。