Gravimetric methods are used for monitoring the migration of CO₂ stored in the reservoir. Reservoir permeability is crucial for injectivity and potentially important for gravity changes associated with CO₂ storage. Nevertheless, its effects on gravity changes have not been investigated systematically. After conducting numerical simulations of CO₂ injection and storage using models with varying permeability conditions (50–1000 mD), we calculated surface gravity changes. Results show that two mechanisms affect gravity decrease, related to differences in CO₂ density and in CO₂ spatial patterns. Under low‐permeability conditions, gravity decrease is minimal during injection because of increases in pressure and the resulting relative high density of CO₂. Gravity decrease is enhanced after injection ceases because of the pressure release and resulting CO₂ expansion. These effects are strong at shallow depths, at which CO₂ is near the critical point and highly compressible. Under higher permeability conditions, rapid spreading of the CO₂ plume causes smaller gravity reduction rate after some decades of injection. After injection ceases, upward CO₂ migration because of buoyancy and plume spreading increase gravity above the injection zone. The time required for gravity change detection depends on permeability. Detection during injection can be made earlier under higher permeability conditions and under lower permeability conditions after injection ceases. These points suggest that permeability affects the feasibility of gravimetric methods. Moreover, designing monitoring programs based on permeability and depth conditions is necessary for successful monitoring. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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与CO2地质封存有关的储层渗透率对重力变化影响的数值研究：对重力监测可行性的启示

重量法用于监测储层中CO ₂的迁移。储层渗透率对于注入性至关重要，对于与CO ₂储存相关的重力变化也可能具有重要意义。然而，其对重力变化的影响尚未得到系统的研究。在使用具有变化的渗透率条件（50–1000 mD）的模型进行CO ₂注入和储存的数值模拟后，我们计算了表面重力变化。结果表明，两种影响重力下降的机制与CO ₂密度和CO _2的差异有关空间格局。在低渗透率条件下，由于压力增加以及由此产生的相对较高的CO ₂密度，在注入过程中重力的降低最小。由于压力释放和导致的CO ₂膨胀，在注射停止后重力降低会增强。这些影响在CO ₂接近临界点且高度可压缩的浅深度很强。在较高的渗透率条件下，注入几十年后，CO ₂羽流的快速扩散会导致重力减小率降低。停止注射后，向上的CO ₂由于浮力和羽状流扩散而引起的迁移增加了注入区上方的重力。重力变化检测所需的时间取决于渗透率。可以在较高渗透率条件下和注入停止后在较低渗透率条件下更早地进行注入过程中的检测。这些观点表明，渗透率会影响重量法的可行性。此外，基于渗透率和深度条件设计监测程序对于成功监测是必要的。©2020年化学工业协会和John Wiley＆Sons，Ltd.