Numerical investigation of the influence of underground water injection on the groundwater system in a shale gas reservoir in southwestern China
Numerical investigation of the influence of underground water injection on the groundwater system in a shale gas reservoir in southwestern China
复制标题
西南某页岩气藏地下水注水对地下水系统影响的数值研究
DOI：
10.1007/s12665-016-5889-6
复制
发表时间：
2016
影响因子：
2.8
通讯作者：
Teng Yanguo
中科院分区：
文献类型：
--
作者：
Yin Wenjie;Hu Litang;Yao Lili;Teng Yanguo
地下注水是处理页岩气生产废水的有效手段。然而，应仔细研究UI对地下水系统的影响，以保护饮用地下水水源。建立了基于TOUGH 2-MP/EOS 7 R的区域水文地质模型，模拟了污水注入四川盆地深层含水层后的压力变化和溶质运移。假设废水以5.45 kg s-1的速率通过井注入5年，注入后的时期为45年。模拟结果表明，UI将导致显着的压力建立在注射期间，之后的压力将消散在后注射期间。溶质的质量分数在整个模拟期间增加。参考《安全饮用水法》的法规草案和中国政府规定的三级地下水质量标准作为评价UI对地下水系统影响的标准。据发现，由UI引起的最大压力水平可能超过安全水平。从以往的研究和注入试验结果分析了渗透率的不确定性。当实施UI时，较低的渗透率水平引起较高程度的压力累积。不同的注射方案进行了讨论，我们验证，从时变注射方案的压力恢复小于从恒定注射方案相同的总注射量。在页岩气藏中实施UI之前，应仔细评估注入方案。
Underground injection (UI) is an effective and efficient means of disposing of wastewater from shale gas production. However, the influence of UI on groundwater systems should be examined carefully to protect drinking groundwater sources. A regional hydrogeological model based on TOUGH2-MP/EOS7R of part of the Sichuan Basin is established to simulate pressure changes and solute transport in response to wastewater injection into deep aquifers. Wastewater is assumed to be injected through a well at a rate of 5.45 kg s−1for 5 years and a post-injection period of 45 years. The simulation results indicate that UI will cause significant pressure buildup during the injection period, after which pressure will dissipate during the post-injection period. The mass fraction of solute increased over the entire simulation period. The draft regulation under the Safe Drinking Water Act and the level III groundwater quality standards regulated by the Chinese government is referenced as the criteria for evaluating the influence of UI on groundwater systems. It is found that maximum pressure levels caused by UI may exceed safe levels. Uncertainties with respect to permeability are analyzed from previous studies and injection test results. Lower levels of permeability incur higher degrees of pressure buildup when UI is implemented. Different injection schemes are discussed, and we verify that pressure buildup from time-variant injection schemes is less than that from constant injection schemes for the same total injection volume. Injection schemes should be carefully evaluated before implementing UI in a shale gas reservoir.