MODELING OF LEAKAGE THROUGH FAULT-ZONE STRUCTURES IN CO2 GEOLOGICAL STORAGE
断层与目标地质二氧化碳储存区的交叉对储存完整性有重要影响。本项目研究了由于流体超压引起的潜在泄漏路径，以确保注入的二氧化碳能够长期封闭。本文提出了与地质力学模块耦合的数值流动模拟方法，旨在确定CO2在沿断层向上的运移程度、泄漏的驱动机制以及对应的孔隙压力和应力变化。
本研究使用了CMG（2017年版）来建立双重介质模型，以准确考虑断层伤害带中的裂缝渗流。数值模拟分为三个步骤进行，逐步增加复杂性，并确保模拟结果的准确性。第一步是通过重现文献中已发表的结果来验证我们的模拟结果。第二步是模拟一个包括垂直封堵断层的简单几何模型。最后一个模型则包括了一个类似于路易斯安那州北部潜在二氧化碳储存点实际特征的断层。
针对这三种情况的研究结果表明，处于休眠状态的裂缝伤害带在考虑地质力学后会变为传导状态，从而导致CO2通过已开裂的裂缝进入上覆岩层进行运移。此外，伤害带沿线的有效应力普遍会随着较高的裂缝渗透率和孔隙压力增加而降低。
Abstract
Faults intersecting target geological CO2 storage zones have important implications for storage integrity. Potential leakage pathways due to fluid over-pressurization are investigated in this project to ensure long-term containment of injected CO2. Numerical flow simulations coupled with a geomechanical module are presented in this work with the purpose of determining the extent of CO2 up-fault migration, the driving mechanisms of leakage and the corresponding response of quantified pore pressure and stress variations.
This study uses dual-continuum models performed by using CMG (2017) to correctly account of flow through fractures in a fault damage zone. Numerical simulations were performed in three steps by gradually adding layers of complexity while ensuring the correctness of simulation results. As the first step, we verify our results by reproducing results published in the literature. In the second step, a simple geometry model including a vertical fault which is laterally sealing was simulated. The last model includes a fault resembling a real feature in a potential CO2 storage site in north Louisiana. Results for the three cases of study, where the initially dormant fractures of the damage zone become conductive with the inclusion of geomechanics, show migration of CO2 through the opened cracks into the overlying formations. Also, effective stresses along the damage zone show a generalized reduction with higher fracture permeabilities and increments in pore pressure.
