CO₂驱油封存过程中断层滑移与泄漏风险的数值模拟研究

Numerical Simulation Study on Fault Slip and Leakage Risk during CO₂ Enhanced Oil Recovery and CO₂ Storage

摘要: 针对致密油藏CCUS-EOR开发过程中CO₂高压注入可能诱发断层滑移与泄漏的问题，本文构建了流体流动–固体力学多场耦合数值模型，系统研究了不同注入距离与注入流量条件下断层稳定性及CO₂封存安全性。通过引入断层滑移系数与渗漏系数，对断层临界滑移行为及CO₂泄漏风险进行了定量评价。结果表明：注入点距断层距离是控制断层稳定性与封存安全性的关键因素，当注入距离小于100 m时，孔隙压力扰动易诱发断层再激活并形成CO₂泄漏通道；当注入距离大于400 m时，断层基本保持稳定，封存安全性显著提高。降低注入流量可有效缓解孔隙压力累积与应力集中，明显减小断层滑移幅度，并延缓或抑制CO₂沿断层的非线性泄漏过程。断层滑移主要发生于注入初期，整体呈对数型增长特征，而CO₂泄漏量随时间表现为先加速后趋缓的演化规律。研究表明，协同优化注入距离与注入流量是保障CCUS-EOR工程安全运行与实现CO₂长期稳定封存的关键技术途径。

Abstract: To address the potential risks of fault slippage and leakage induced by high-pressure CO₂ injection during CCUS-EOR development in tight oil reservoirs, this study establishes a multi-field coupled numerical model integrating fluid flow, solid mechanics, and rock damage. The stability of faults and the security of CO₂ storage were systematically investigated under varying injection distances and flow rates. By introducing fault slip and leakage coefficients, the critical slip behavior and leakage risks were quantitatively evaluated. The results indicate that the injection distance is the primary factor controlling fault stability and storage integrity. When the injection distance is less than 100 m, pore pressure perturbations readily trigger fault reactivation, creating pathways for CO₂ leakage. Conversely, fault stability is maintained and storage security is significantly enhanced when the distance exceeds 400 m. Furthermore, reducing the injection flow rate effectively mitigates pore pressure buildup and stress concentration, thereby decreasing the magnitude of fault slip and inhibiting nonlinear leakage processes. Observations show that fault slippage primarily occurs during the initial injection stage, following a logarithmic growth pattern, while the CO₂ leakage rate evolves from an initial acceleration to a subsequent deceleration over time. This research suggests that the synergistic optimization of injection distance and flow rate is a critical technical strategy for ensuring the safe operation of CCUS-EOR projects and achieving long-term CO₂ sequestration.