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ABSTRACT: In response to the escalating greenhouse gas emissions and climate change problem, promising solutions have emerged in the form of Carbon Capture and Storage (CCS) projects, offering potential avenues for mitigating environmental impact. This study explores the behavior of CO2 storage reservoirs and associated fault reactivation mechanisms using three-dimensional (3D) numerical modeling using Distinct Element Code (3DEC). The critical role of the reservoir-caprock interface is highlighted by the vertical displacement measurements from numerical simulation. Proximity to the reservoir-seal contact point correlates with maximum deformation magnitudes of 0.052 m, while the surface level (Z = 0 m) is subject to less significant deformation (0.01 m), indicating favorable reservoir stability. Aligning closely with previous 2D analyses, further parametric studies with real-world data and prolonged observations would be beneficial for validating modeling assumptions. 1. BACKGROUND For the past couple of decades, CO2 Capture and Storage (CCS) has been consistently recommended and employed in response to the intensified greenhouse gases emission problem. In practice, in a CO2 reservoir, increasing pressure resulting from injection can lead to crack propagation and damage to borehole and seal rock through various mechanisms (Rutqvist, 2012; Zoback & Gorelick, 2012). As pressure builds within the reservoir due to CO2 injection, it can induce stresses in the surrounding rock mass, potentially exceeding the rock's strength. This can lead to the initiation and propagation of fractures, particularly in zones of pre-existing weaknesses such as faults or joints. Large amounts of pressure can cause deformation and compaction of the reservoir rock, leading to subsidence or heave around the borehole. This can result in borehole instability, including casing failure, collapse, or even blowouts. Furthermore, if the seal rock (caprock) above the reservoir is not sufficiently impermeable or strong, increased pressure from CO2 injection can cause it to fracture or deform, compromising its ability to contain the injected CO2. This can lead to CO2 leakage pathways, allowing the gas to migrate towards the surface or into underground rock layers, posing environmental and safety risks. Hence, such a promising solution in the form of CCS requires a safe and efficient storage site design to avoid above-described injection- or sequestration-induced damage that may ultimately lead to the gas leakage.
Mortazavi et al. (Sun,) studied this question.