Mortazavi Ali, Maratov Torekeldi
School of Mining & Geosciences, Nazarbayev University, 53 Kabanbay Batyr Ave., Nur-Sultan 010000, Kazakhstan.
ACS Omega. 2024 Jul 17;9(30):32513-32524. doi: 10.1021/acsomega.3c08859. eCollection 2024 Jul 30.
Due to extensive industrialization and ongoing fossil fuel consumption, CO emissions have significantly contributed to climate change and rising greenhouse gas levels. The collection and storage of CO in subsurface geological formations have been proposed as a feasible alternative. The well-documented In Salah storage site is the subject of the chosen case study. For the numerical analysis, a two-dimensional finite element simulation of fault reactivation processes was conducted in the context of the CO storage. The goal of this research is to conduct a mechanistic numerical analysis of a typical CO storage condition. The selected analysis domain is 4 km (width) × 2 km (depth) and includes all important domains and formations (overburden, main caprock, lower caprock, and underburden) of the In Salah site. The simulation results indicate that the influence of fault reactivation under 32 MPa of base injection pressure results in peak vertical deformation of 0.044 m in the caprock and a vertical displacement magnitude of 0.015-0.020 m at the surface level ( = 0 m). The derived vertical deformation findings at the surface level are in agreement with the data obtained from the in situ InSAR monitoring system in 2009. The effects of the changes in the fault dip angle, key caprock mechanical parameters, and in situ stress ratio on the displacement profile are evaluated within the parametric study. In comparison to the benchmark numerical run, the scenario ratio of = 0.5 led to a significant reduction in the displacement. The simulation in which the fault dip angle was 30° produced a more pessimistic result with a larger displacement field. This could be an indication of heightened fault reactivation risks associated with low-angle faults in storage sites with strong horizontal stress regimes due to the combined effect of increased shear stress and reduced inherent frictional resistance on the fault plane. Considering that a vertical fault dip angle (90°) and an additional three 20 m long vertical fractures above the reservoir produced similar vertical displacement observed with the fault dipping at a 60° angle, this indicated that the vertical faults in the vicinity of the storage site pose limited safety risks to the integrity of the sealing rock.
由于广泛的工业化以及持续的化石燃料消耗，一氧化碳排放对气候变化和温室气体水平上升起到了显著作用。将一氧化碳收集并存储于地下地质构造中已被提议作为一种可行的替代方案。有充分记录的因萨拉（In Salah）存储地点是所选案例研究的对象。为进行数值分析，在一氧化碳存储的背景下对断层再活化过程进行了二维有限元模拟。本研究的目标是对典型的一氧化碳存储条件进行机理数值分析。所选分析区域为4千米（宽）×2千米（深），涵盖了因萨拉地点的所有重要区域和地层（上覆岩层、主要盖层、下部盖层以及下伏岩层）。模拟结果表明，在32兆帕的基础注入压力下，断层再活化的影响导致盖层的峰值垂直变形为0.044米，地表水平（z = 0米）处的垂直位移量为0.015 - 0.020米。在地表水平得出的垂直变形结果与2009年从因萨拉干涉合成孔径雷达（InSAR）现场监测系统获得的数据一致。在参数研究中评估了断层倾角、关键盖层力学参数以及原地应力比的变化对位移剖面的影响。与基准数值运行相比，应力比为0.5的情况导致位移显著减小。断层倾角为30°的模拟产生了更悲观的结果，位移场更大。这可能表明，在水平应力较强的存储地点，由于断层平面上剪切应力增加和固有摩擦阻力减小的综合作用，与低角度断层相关的断层再活化风险增加。鉴于垂直断层倾角（90°）以及储层上方另外三条20米长垂直裂缝产生的垂直位移与断层倾角为60°时观察到的相似，这表明存储地点附近的垂直断层对密封岩石的完整性构成的安全风险有限。
