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Stress Shadow Effects and Microseismic Events during Hydrofracturing of Multiple Vertical Wells in Tight Reservoirs: A Three-dimensional Numerical Model
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.jngse.2020.103684 Yang Ju , Yang Li , Yongliang Wang , Yongming Yang
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.jngse.2020.103684 Yang Ju , Yang Li , Yongliang Wang , Yongming Yang
Abstract Optimizing hydrofracturing schemes for multiple vertical wells is crucial for developing complex fracture networks that facilitates the transport of unconventional hydrocarbon resources in tight reservoirs. The stress shadow effect that occurs between multiple wells has a significant effect on the development of fracture networks. However, the influence of fracturing schemes, including fracturing sequences and well spacing, on stress shadow effects are poorly understood. In this study, a three-dimensional (3D) numerical model based on actual reservoir data was developed to explore these influences. The simulation considers hydromechanical coupling and leak-off effects and employs the adaptive finite element–discrete element method to achieve high-precision solutions and reliable 3D fracture propagation paths. Typical fracturing cases were simulated to address the differences between sequential and simultaneous fracturing, the effects of different well spacing in sequential fracturing, and the optimization of the number of multiple vertical wells required to maximize fracturing efficiency. Our results indicate that the 3D fractured areas produced in simultaneous fracturing are much smaller than those produced in sequential fracturing. For sequential fracturing, the fractured areas of three vertical wells were larger than the fractured areas of five vertical wells. In the sequential fracturing of three wells, the fractured areas were almost unchanged because the well spacing was large enough to sufficiently weaken the stress shadow effect, thus inducing almost constant fractured areas in each fracturing sequence. Using the computed stress difference and fractured areas, we defined an area ratio to quantify the stress shadow effect, which reflects the feasibility of various fracturing schemes. It is easier to induce more microseismic events during simultaneous fracturing than during sequential fracturing, and the cumulative magnitude of simultaneous fracturing is higher; furthermore, the cumulative magnitude of sequential fracturing of the three wells was lower than that of the five wells, reflecting weak stress shadow effects.
中文翻译:
致密油藏多口直井水力压裂过程中的应力影效应和微地震事件:三维数值模型
摘要 优化多口垂直井的水力压裂方案对于开发复杂的裂缝网络至关重要,这有利于致密油藏中非常规油气资源的输送。多井间发生的应力阴影效应对裂缝网络的发育有显着影响。然而,压裂方案,包括压裂序列和井距,对应力阴影效应的影响知之甚少。在本研究中,开发了基于实际储层数据的三维 (3D) 数值模型来探索这些影响。模拟考虑了流体力学耦合和泄漏效应,并采用自适应有限元-离散元方法来实现高精度解和可靠的 3D 裂缝扩展路径。模拟了典型压裂案例,以解决顺序压裂和同步压裂之间的差异、不同井距对顺序压裂的影响以及最大化压裂效率所需的多口直井数量的优化。我们的研究结果表明,同时压裂产生的 3D 裂缝面积远小于顺序压裂产生的 3D 裂缝面积。连续压裂方面,3口直井压裂面积大于5口直井压裂面积。3口井序贯压裂时,由于井距足够大,充分削弱了应力阴影效应,裂缝面积几乎没有变化,从而在每个压裂序列中产生几乎恒定的裂缝面积。使用计算的应力差和压裂面积,我们定义了一个面积比来量化应力阴影效应,这反映了各种压裂方案的可行性。同时压裂比序贯压裂更容易诱发更多的微震事件,同时压裂累积震级更高;此外,3口井连续压裂累计量级低于5口井,应力影效应较弱。
更新日期:2020-12-01
中文翻译:
致密油藏多口直井水力压裂过程中的应力影效应和微地震事件:三维数值模型
摘要 优化多口垂直井的水力压裂方案对于开发复杂的裂缝网络至关重要,这有利于致密油藏中非常规油气资源的输送。多井间发生的应力阴影效应对裂缝网络的发育有显着影响。然而,压裂方案,包括压裂序列和井距,对应力阴影效应的影响知之甚少。在本研究中,开发了基于实际储层数据的三维 (3D) 数值模型来探索这些影响。模拟考虑了流体力学耦合和泄漏效应,并采用自适应有限元-离散元方法来实现高精度解和可靠的 3D 裂缝扩展路径。模拟了典型压裂案例,以解决顺序压裂和同步压裂之间的差异、不同井距对顺序压裂的影响以及最大化压裂效率所需的多口直井数量的优化。我们的研究结果表明,同时压裂产生的 3D 裂缝面积远小于顺序压裂产生的 3D 裂缝面积。连续压裂方面,3口直井压裂面积大于5口直井压裂面积。3口井序贯压裂时,由于井距足够大,充分削弱了应力阴影效应,裂缝面积几乎没有变化,从而在每个压裂序列中产生几乎恒定的裂缝面积。使用计算的应力差和压裂面积,我们定义了一个面积比来量化应力阴影效应,这反映了各种压裂方案的可行性。同时压裂比序贯压裂更容易诱发更多的微震事件,同时压裂累积震级更高;此外,3口井连续压裂累计量级低于5口井,应力影效应较弱。