Pore pressure variations owing to fluid injection-extraction from deep sedimentary basins can potentially trigger shear slipping along pre-existing faults. We use a coupled two-phase flow and geomechanical model to better understand the physical processes associated with simultaneous injection of $$\hbox {CO}_{2}$$ CO 2 and production of $$\hbox {CH}_{4}$$ CH 4 . The model considers permeability changes induced by deformation and slip-dependent friction of the sliding fault. The simulation results show that a sudden stress drop associated with fault reactivation occurs after 46 days of simultaneous fluid injection-extraction. The gas production rate instantaneously decreases as a result of the pressure drawdown applied at the wellbore and then approaches a relatively stable state that cumulatively produces coalbed methane of $$5.90 \times 10^{7}\,\hbox {kg}$$ 5.90 × 10 7 kg . A sensitivity study shows that the arrangement of well operations affects the fault slip timing and corresponding sliding distance, as well as the cumulative gas production. Increasing production-injection or injection-production cycle number advances the timing of fault reactivation and reduces the maximum slip. More cycles result in higher peak production and hence promote the corresponding cumulative gas production, which significantly improves methane productivity efficiency. The results of this study demonstrate the importance of well operations on fault reactivation and cumulative methane production during $$\hbox {CO}_{2}$$ CO 2 -enhanced coalbed methane recovery.

中文翻译：

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多相流和孔隙力学耦合建模用于井操作对断层滑动和甲烷生产

由于流体从深层沉积盆地注入-抽取而引起的孔隙压力变化可能会触发沿预先存在的断层的剪切滑动。我们使用耦合的两相流和地质力学模型来更好地理解与同时注入 $$\hbox {CO}_{2}$$ CO 2 和生产 $$\hbox {CH}_{4 相关的物理过程}$$ CH 4 。该模型考虑了由滑动断层的变形和滑动相关摩擦引起的渗透率变化。模拟结果表明，在 46 天同时进行流体注入-抽取后，会出现与断层重新激活相关的突然应力下降。由于井筒压力下降，产气率瞬间下降，然后接近相对稳定的状态，累积产生 5.90 美元的煤层气 \times 10^{7}\，\hbox {kg}$$ 5.90 × 10 7 kg 。敏感性研究表明，井作业安排影响断层滑动时间和相应滑动距离，以及累计产气量。增加生产注入或注入生产周期数会提前故障重新激活的时间并减少最大滑移。更多的循环导致更高的峰值产量，从而促进相应的累积产气量，从而显着提高甲烷生产效率。这项研究的结果证明了在 $$\hbox {CO}_{2}$$ CO 2 增强煤层气回收期间井操作对断层再活化和累积甲烷产量的重要性。敏感性研究表明，井作业安排影响断层滑动时间和相应滑动距离，以及累计产气量。增加生产注入或注入生产周期数会提前故障重新激活的时间并减少最大滑移。更多的循环导致更高的峰值产量，从而促进相应的累积产气量，从而显着提高甲烷生产效率。这项研究的结果证明了在 $$\hbox {CO}_{2}$$ CO 2 增强煤层气回收期间井操作对断层再活化和累积甲烷产量的重要性。敏感性研究表明，井作业安排影响断层滑动时间和相应滑动距离，以及累计产气量。增加生产注入或注入生产周期数会提前故障重新激活的时间并减少最大滑移。更多的循环导致更高的峰值产量，从而促进相应的累积产气量，从而显着提高甲烷生产效率。这项研究的结果证明了在 $$\hbox {CO}_{2}$$ CO 2 增强煤层气回收期间井操作对断层再活化和累积甲烷产量的重要性。增加生产注入或注入生产周期数会提前故障重新激活的时间并减少最大滑移。更多的循环导致更高的峰值产量，从而促进相应的累积产气量，从而显着提高甲烷生产效率。这项研究的结果证明了在 $$\hbox {CO}_{2}$$ CO 2 增强煤层气回收期间井操作对断层再活化和累积甲烷产量的重要性。增加生产注入或注入生产周期数会提前故障重新激活的时间并减少最大滑移。更多的循环导致更高的峰值产量，从而促进相应的累积产气量，从而显着提高甲烷生产效率。这项研究的结果证明了在 $$\hbox {CO}_{2}$$ CO 2 增强煤层气回收期间井操作对断层再活化和累积甲烷产量的重要性。