Methane contamination of drinking water resources is one of the major concerns associated with unconventional gas development. This study assesses the potential contamination of shallow groundwater via methane migration from a leaky natural gas well through overburden rocks, following hydraulic fracturing. A two-dimensional, two-phase, two-component numerical model is employed to simulate methane and brine upward migration toward shallow groundwater in a generic sedimentary basin. A sensitivity analysis is conducted to examine the influence of methane solubility, capillary pressure–saturation relationship parameters and residual water saturation of overburden rocks, gas leakage rate from the well, tilted formations, and low-permeability sediments (i.e., claystones) on the transport of fluids. Results show that the presence of lithological barriers is the most important factor controlling the temporal–spatial distribution of methane in the subsurface and the arrival time to shallow groundwater. A pulse of high leakage rate is required for early manifestation of methane in groundwater wells. Simulations reveal that the presence of tilted features could further explain fast-growing methane contamination and extensive lateral spreading reported in field studies.

饮用水资源的甲烷污染是与非常规天然气开发相关的主要问题之一。这项研究评估了水力压裂后甲烷从泄漏的天然气井穿过覆盖岩的迁移所引起的浅层地下水的潜在污染。使用二维，两相，两成分的数值模型来模拟甲烷和盐水在普通沉积盆地中向浅层地下水的向上迁移。进行了敏感性分析，以检查甲烷溶解度，毛细压力-饱和度关系参数和覆岩的残留水饱和度，井的气体泄漏率，倾斜的地层和低渗透性沉积物（即粘土岩）对运输的影响。的液体。结果表明，岩性屏障的存在是控制甲烷在地下的时空分布以及到达浅层地下水的时间的最重要因素。地下水井中甲烷的早期显现需要高泄漏率的脉冲。模拟表明，倾斜特征的存在可以进一步解释田间研究报告的甲烷快速增长的污染和广泛的横向扩散。