Nicot Jean-Philippe, Larson Toti, Darvari Roxana, Mickler Patrick, Slotten Michael, Aldridge Jordan, Uhlman Kristine, Costley Ruth
Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, 10100 Burnet Road, Austin, TX.
Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2305 Speedway, Austin, TX.
Ground Water. 2017 Jul;55(4):443-454. doi: 10.1111/gwat.12500. Epub 2017 Jan 19.
Understanding the source of dissolved methane in drinking-water aquifers is critical for assessing potential contributions from hydraulic fracturing in shale plays. Shallow groundwater in the Texas portion of the Haynesville Shale area (13,000 km ) was sampled (70 samples) for methane and other dissolved light alkanes. Most samples were derived from the fresh water bearing Wilcox formations and show little methane except in a localized cluster of 12 water wells (17% of total) in a approximately 30 × 30 km area in Southern Panola County with dissolved methane concentrations less than 10 mg/L. This zone of elevated methane is spatially associated with the termination of an active fault system affecting the entire sedimentary section, including the Haynesville Shale at a depth more than 3.5 km, and with shallow lignite seams of Lower Wilcox age at a depth of 100 to 230 m. The lignite spatial extension overlaps with the cluster. Gas wetness and methane isotope compositions suggest a mixed microbial and thermogenic origin with contribution from lignite beds and from deep thermogenic reservoirs that produce condensate in most of the cluster area. The pathway for methane from the lignite and deeper reservoirs is then provided by the fault system.
了解饮用水含水层中溶解甲烷的来源对于评估页岩气藏水力压裂的潜在贡献至关重要。对海恩斯维尔页岩地区得克萨斯部分（13000平方千米）的浅层地下水进行了采样（70个样本），以分析甲烷和其他溶解轻烷烃。大多数样本来自含水的威尔科克斯地层，除了在南帕诺拉县一个约30×30千米区域内的12口水井局部集群（占总数的17%）中，溶解甲烷浓度低于10毫克/升外，甲烷含量很少。这个甲烷含量升高的区域在空间上与一个影响整个沉积层段（包括深度超过3.5千米的海恩斯维尔页岩）的活动断层系统的末端相关，并且与威尔科克斯下层年龄、深度为100至230米的浅层褐煤层相关。褐煤的空间延伸与该集群重叠。气体湿度和甲烷同位素组成表明，甲烷来源混合了微生物成因和热成因，来自褐煤层以及在该集群大部分区域产生凝析油的深层热成因储层。褐煤和更深层储层中的甲烷通过断层系统形成运移通道。
