Carbon sequestration involves long-term containment of CO₂ in ideally sealed reservoirs. However, CO₂ migration can weaken rocks and faults by geochemical alteration, elevate risks of seismic hazards, and loss of inventory. Recent studies show that CO₂ bleaching can alter the iron oxide grain coating of sand-sized quartz in sandstones, which may impose a significant influence on frictional stability and permeability evolution of faults in sandstones. This study investigates the influence of iron oxide grain coatings via coupled shear-flow experiments on uncoated, hematite-coated, and CO₂-transformed goethite-coated synthetic sand gouge. Shear strength, frictional stability, healing/relaxation, and shear-parallel permeability are measured in velocity-stepping and slide-hold-slide loading modes. Hematite-coated sand exhibits the highest shear strength, followed by goethite-coated and uncoated sand. All samples, both coated and uncoated, show similar residual shear strength. Frictional stability measurements suggest hematite-coated sand may undergo potential seismic slip (negative (a − b) values); goethite-coated sand is aseismic (positive (a − b) values) but features higher frictional healing and relaxation. Shear-parallel permeability enhances during initial shear in all samples, followed by a sharp decline after the peak strength, except for goethite-coated sand, for which permeability reduction is moderate. SEM characterizations pre- and post-shear suggest that the competitive liberation, transport, and clogging of coating particles and shear-produced wear products can be an important mechanism in permeability evolution.

碳固存涉及在理想密封的储层中长期封闭CO ₂。但是，CO _2的迁移会通过地球化学改变而削弱岩石和断层，增加地震危险的风险以及库存的损失。最近的研究表明，CO ₂漂白可以改变砂岩中砂状石英的氧化铁晶粒涂层，这可能对砂岩断层的摩擦稳定性和渗透性演化产生重大影响。本研究通过耦合剪切流实验研究了氧化铁晶粒涂层对未涂层，赤铁矿涂层和CO _2的影响-转变针铁矿涂层的合成砂凿。剪切强度，摩擦稳定性，愈合/松弛和剪切平行磁导率在速度步进和滑动保持滑动加载模式下进行测量。赤铁矿涂层的砂表现出最高的剪切强度，其次是针铁矿涂层和未涂层​​的砂。所有涂覆和未涂覆的样品均显示出相似的残余剪切强度。摩擦稳定性测量表明，赤铁矿覆盖的砂层可能会发生潜在的地震滑动（负（a-b）值）；针铁矿覆盖的砂具有抗震性（正（a-b）值），但具有较高的摩擦恢复性和松弛性。在所有样品的初始剪切过程中，剪切平行渗透率均得到增强，峰值强度后急剧下降，除了针铁矿覆盖的砂（渗透率降低程度适中）外。