Abstract During the hydraulic stimulation of shale gas reservoirs the pore pressure on pre-existing faults/fractures can be raised sufficiently to cause reactivation/slip. There is some discrepancy in the literature over whether this interaction is beneficial or not to hydrocarbon extraction. Some state that the interaction will enhance the connectivity of fractures and also increase the Stimulated Reservoir Volume. However, other research states that natural fractures may cause leak-off of fracturing fluid away from the target zone, therefore reducing the amount of hydrocarbons extracted. Furthermore, at a larger scale there is potential for the reactivation of larger faults, this has the potential to harm the well integrity or cause leakage of fracturing fluid to overlying aquifers. In order to understand fault reactivation potential during hydraulic stimulation a series of analogue tests have been performed. These tests were conducted using a Bowland Shale gouge in the Angled Shear Rig (ASR). Firstly, the gouge was sheared until critically stressed. Water was then injected into the gouge to simulate pore fluid increase as a response to hydraulic stimulation. A number of experimental parameters were monitored to identify fracture reactivation. This study examined the effect of stress state, moisture content, and mineralogy on the fault properties. The mechanical strength of a gouge increases with stress and therefore depth. As expected, a reduction of moisture content also resulted in a small increase in mechanical strength. Results were compared with tests previously performed using the ASR apparatus, these showed that mineralogy will also affect the mechanical strength of the gouge. However, further work is required to investigate the roles of specific minerals, e.g. quartz content. During the reactivation phase of testing all tests reactivated, releasing small amounts of energy. This indicates that in these basic conditions natural fractures and faults will reactivate during the hydraulic stimulation if critically stressed. Furthermore, more variables should be investigated in the future, such as the effect of fluid injection rate and type of fluid.

中文翻译：

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断层泥性质对水力增产过程中断层再活化的作用 使用模拟故障的实验研究

摘要 在页岩气藏水力增产过程中，原有断层/裂缝的孔隙压力会升高到足以引起再活化/滑移。关于这种相互作用是否有利于碳氢化合物提取，文献中存在一些差异。一些人指出，相互作用将增强裂缝的连通性并增加增产储层体积。然而，其他研究表明，天然裂缝可能会导致压裂液从目标区域泄漏，从而减少提取的碳氢化合物量。此外，在更大范围内，较大断层有可能重新活动，这有可能损害井的完整性或导致压裂液泄漏到上覆含水层。为了了解水力增产过程中的故障再激活潜力，已经进行了一系列模拟测试。这些测试是在斜角剪切钻机 (ASR) 中使用 Bowland 页岩凿进行的。首先，将凿子剪切到临界应力。然后将水注入凿井以模拟作为对水力刺激的响应的孔隙流体增加。监测了许多实验参数以识别裂缝再激活。本研究考察了应力状态、水分含量和矿物学对断层特性的影响。凿孔的机械强度随着应力和深度的增加而增加。正如预期的那样，水分含量的降低也会导致机械强度的小幅增加。结果与之前使用 ASR 设备进行的测试进行了比较，这些表明矿物学也会影响凿岩的机械强度。然而，需要进一步的工作来研究特定矿物的作用，例如石英含量。在测试的重新激活阶段，所有测试重新激活，释放少量能量。这表明在这些基本条件下，如果受到严重压力，自然裂缝和断层将在水力增产过程中重新激活。此外，未来应该研究更多变量，例如流体注入速率和流体类型的影响。这表明在这些基本条件下，如果受到严重压力，自然裂缝和断层将在水力增产过程中重新激活。此外，未来应该研究更多变量，例如流体注入速率和流体类型的影响。这表明在这些基本条件下，如果受到严重压力，自然裂缝和断层将在水力增产过程中重新激活。此外，未来应该研究更多变量，例如流体注入速率和流体类型的影响。