Laboratory tests were conducted in a triaxial load frame with acoustic emission and transmission capability to investigate mechanisms that might be initiating the microseismicity experienced in CO₂ injection operations. Although often related to reactivation of mapped faults or local fracturing due to reduced injectivity, the case of the Illinois Basin – Decatur Project is used here to illustrate the need for better understanding of what triggers microseismic events in relatively large permeability, good reservoir candidates. There, microseismicity has occurred in the CO₂ storage target formation, the Mt. Simon sandstone, as well as in the underlying Precambrian basement. The microseismicity in the Mt. Simon sandstone occurred ahead of CO₂ plume arrival and at relatively low injection pressure conditions, well below the fracturing pressure at the injection well. A hypothesis is suggested for the occurrence of such events in the field, whereby critically stressed planes are activated by the passage of the pressure front at injection start; these faults are small and thus not visible in the seismic survey. In order to test this hypothesis, sandstone plugs were prepared by two different methods to incorporate a fracture plane, which we attempted to reactivate by pore pressure pulses. The reactivation was successful at low pressure for a fracture created in the laboratory at reservoir conditions but was unsuccessful except at a much higher pore pressure in a saw-cut artificial fracture. The results suggest that tortuous, rough stress-induced fractures may be easier to reactivate because of the higher probability that sections are already favorably oriented with respect to critical shear stress at a low pore pressure increase. Saw-cut fractures may close completely under isotropic stress loading and may be difficult to activate unless exactly oriented with respect to critical shear stress at a low pore pressure increase. Acoustic emission accompanying fracture reactivation was also recorded and analyzed. This revealed a different event distribution energy between creating and reactivating the fracture.

在具有声发射和传输能力的三轴载荷框架中进行了实验室测试，以研究可能引发CO ₂注入操作中发生的微地震的机理。尽管由于注入量的降低，通常与断层的活化或局部压裂有关，但这里以伊利诺伊盆地迪凯特项目为例，说明需要更好地了解在较大渗透率，良好储层候选条件下触发微地震事件的原因。在那里，在CO ₂储存目标的形成Mt中发生了微地震。西蒙砂岩以及下前寒武纪地下室。山的微震性。西蒙砂岩发生在CO _2之前羽流到达并在相对较低的注入压力条件下，远低于注入井的压裂压力。对于在现场发生这样的事件，提出了一种假设，即在注射开始时通过压力前沿的传递来激活临界应力平面。这些断层很小，因此在地震勘探中不可见。为了验证这一假设，我们通过两种不同的方法制备了砂岩塞，以结合裂缝面，我们试图通过孔隙压力脉冲来激活裂缝面。对于在实验室中在储层条件下产生的裂缝，低压在低压下成功进行了重新活化，但除锯齿状人工裂缝中的孔隙压力高得多外，均未成功进行。结果表明，曲折，粗应力引起的裂缝可能更容易重新活化，因为在较低的孔隙压力增加下，各部分已经相对于临界剪切应力有利地定向了。锯齿状裂缝可能在各向同性应力作用下完全闭合，并且可能难以激活，除非在孔隙压力低的情况下相对于临界剪应力精确定向。还记录并分析了伴有骨折再激活的声发射。这揭示了在创建和重新激活裂缝之间存在不同的事件分配能量。锯齿状裂缝可能在各向同性应力作用下完全闭合，并且可能难以激活，除非在孔隙压力低的情况下相对于临界剪应力精确定向。还记录并分析了伴有骨折再激活的声发射。这揭示了在创建和重新激活裂缝之间存在不同的事件分配能量。锯齿状裂缝可能在各向同性应力作用下完全闭合，并且可能难以激活，除非在孔隙压力低的情况下相对于临界剪应力精确定向。还记录并分析了伴有骨折再激活的声发射。这揭示了在创建和重新激活裂缝之间存在不同的事件分配能量。