The Geomechanical and Fault Activation Modeling during CO2 Injection into Deep Minjur Reservoir, Eastern Saudi Arabia
大量二氧化碳排放到大气中是全球变暖的主要原因之一。控制大气中CO2浓度水平的最可行方法是捕获并永久封存多余的CO2在地下地质储层中。注入CO2会导致孔隙压力增加，监测孔隙压力上升至关重要，以防止储层的潜在失效以及储存的CO2泄漏到盖层，然后返回大气中。本文考虑沙特阿拉伯东部Minjur砂岩储层，建立耦合地质力学模型并进行相应的稳定性分析。
在地质力学模拟过程中，考虑了穿过Minjur和Marrat层的断层。在整个储层没有断层和有断层的情况下，计算了注入引起的孔隙压力和地面隆起剖面。采用莫尔-库仑破坏准则进行稳定性分析。目前的研究中，在没有地质断层的情况下，孔隙压力的过度增加使储层更接近破坏包络线。但在存在地质断层的情况下，储层达到破坏包络线，断层被激活。开发的地质力学模型根据储层孔隙压力和储层应力的大小，提供了CO2安全注入参数的估计值。
Abstract:
The release of large quantities of CO2 into the atmosphere is one of the major causes of global warming. The most viable method to control the level of CO2 in the atmosphere is to capture and permanently sequestrate the excess amount of CO2 in subsurface geological reservoirs. The injection of CO2 gives rise to pore pressure buildup. It is crucial to monitor the rising pore pressure in order to prevent the potential failure of the reservoir and the subsequent leakage of the stored CO2 into the overburden layers, and then back to the atmosphere. In this paper, the Minjur sandstone reservoir in eastern Saudi Arabia was considered for establishing a coupled geomechanical model and performing the corresponding stability analysis.
During the geomechanical modeling process, the fault passing through the Minjur and Marrat layers was also considered. The injection-induced pore-pressure and ground uplift profiles were calculated for the case of absence of a fault across the reservoir, as well as the case with a fault. The stability analysis was performed using the Mohr–Coulomb failure criterion. In the current study, the excessive increase in pore pressure, in the absence of geological faults, moved the reservoir closer to the failure envelope, but in the presence of geological faults, the reservoir reached to the failure envelope and the faults were activated. The developed geomechanical model provided estimates for the safe injection parameters of CO2 based on the magnitudes of the reservoir pore pressure and stresses in the reservoir.
