Hydraulic fracturing in shale gas formations involves the injection of large volumes of aqueous fluid deep underground. Only a small proportion of the injected water volume is typically recovered, raising concerns that the remaining water may migrate upward and potentially contaminate groundwater aquifers. We implement a numerical model of two-phase water and gas flow in a shale gas formation to test the hypothesis that the remaining water is imbibed into the shale rock by capillary forces and retained there indefinitely. The model includes the essential physics of the system and uses the simplest justifiable geometrical structure. We apply the model to simulate wells from a specific well pad in the Horn River Basin, British Columbia, where there is sufficient available data to build and test the model. Our simulations match the water and gas production data from the wells remarkably closely and show that all the injected water can be accounted for within the shale system, with most imbibed into the shale rock matrix and retained there for the long term.

中文翻译：

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页岩气形成中水与气流动的数值模拟，重点关注水力压裂液的去向

页岩气地层的水力压裂涉及在地下深处注入大量的含水流体。通常只回收注入水量的一小部分，这引起了人们对剩余水可能向上迁移并可能污染地下水蓄水层的担忧。我们在页岩气地层中实现了水和气两相流的数值模型，以检验以下假设：剩余水被毛细作用力吸收到页岩中，并无限期地保留在那里。该模型包括系统的基本物理原理，并使用最简单的合理的几何结构。我们应用该模型来模拟不列颠哥伦比亚省霍恩河盆地中特定井场的井，那里有足够的可用数据来构建和测试模型。