Extraction of radioactive and toxic element contaminants from organic-rich shale in contact with hydraulic fracturing fluids

ellis, Brian r .密歇根大学安娜堡分校（university Ann arbor）定向钻井和油井增产技术的最新进展，使得通过大规模水力压裂从页岩地层中开采天然气和石油变得经济可行。水力压裂的一个副作用是暴露在先前水力分离的矿物中，这些矿物可能含有天然存在的放射性物质和有毒金属元素。这些成分可能会被释放到压裂液中，然后回流到地面，必须妥善处理，以避免污染淡水资源。本研究的主要目的是表征水力压裂液与富有机质页岩之间的相互作用，以确定水力压裂液化学物质调动不需要的微量有毒金属和放射性核素返排液成分的潜力。虽然预计返排液会受到一定程度的污染，例如，已知这些返排液可能是高盐的，含有高浓度的微量有毒金属和放射性元素，但这些污染物被浸出的可能性，与页岩成分、井下条件和水力压裂液配方中存在的化学添加剂有关，目前还没有确定。为了解决这一知识差距，将进行一系列批量和流动实验，以评估这些参数对污染物浸出的影响。实验将在密歇根州两个页岩气藏的天然页岩岩石样本上进行，在现场遇到的典型原位温度和压力条件下进行。这项研究将建造独特的、最先进的高温高压设备，并用于开发标准化的方法，以评估富有机质页岩在与地下水力压裂液接触时释放无机有毒和放射性元素的化学过程和机制。目前评估反排水质量的工作依赖于对水返回地面后的分析。为了正确解决或消除水力压裂对水质影响的担忧，需要更好地了解地下水力压裂液的化学演变。这项研究的结果将有助于指导行业最佳实践，以可持续地开发国内页岩气资源，并减少水力压裂完井对水质的潜在影响。此外，了解注入流体的化学演变将有助于制定完善的反排水管理政策，包括处理、再利用和处置。

CBET 1336719Ellis, Brian R.University of Michigan Ann ArborRecent advances in directional drilling and well stimulation techniques have made extraction of natural gas and oil from shale formations economically viable via high-volume hydraulic fracturing. A side effect of hydraulic fracturing is the exposure of previously hydraulically isolated minerals that may contain naturally occurring radioactive material and toxic metal elements. These constituents may be released into the fracturing fluids that flow back to the surface, which must be properly handled to avoid contamination of fresh water resources. The primary objective of this study is to characterize the interactions between the hydraulic fracturing fluid and organic-rich shales in order to determine the potential for hydraulic fracturing fluid chemicals to mobilize undesirable trace toxic metal and radionuclide flowback fluid constituents. While flowback fluids are expected to be contaminated to some degree, e.g., it is known that these fluids may be highly saline and contain elevated levels of trace toxic metals and radioactive elements, the potential for these contaminants to be leached as a function of the shale composition, down-hole conditions, and chemical additives present in hydraulic fracturing fluid formulations has not yet been determined. To address this knowledge gap, a series of batch and flow-through experiments will be performed to assess the impact of these parameters on contaminant leaching. Experiments will be conducted on natural shale rock samples from two Michigan shale gas reservoirs, under typical in situ temperature and pressure conditions encountered in the field. Unique and state-of-the art high temperature and pressure apparatuses will be constructed for this research and used to development standardized methods for evaluating the chemical processes and mechanisms controlling the release of inorganic toxic and radioactive elements from organic-rich shales in contact with hydraulic fracturing fluids in the subsurface.Current efforts to assess flowback water quality rely on the analysis of the water once it has returned to the surface. To properly address or dismiss concerns regarding water quality impacts associated with hydraulic fracturing, a better understanding of the chemical evolution of hydraulic fracturing fluids in the subsurface is required. The results of this study will help guide industry best practices for sustainably developing domestic shale gas resources and for reducing potential water quality impacts associated with hydraulic fracturing well completions. Furthermore, understanding the chemical evolution of the injected fluids will aid in forming sound regulatory policy addressing flowback water management practices, including treatment, reuse and disposal.