Impact of Geochemical Weathering on Fault Zone Architecture

长期以来，人们一直在研究断裂带的跨断层流动特性，以限制它们容纳油气柱的能力。然而，断层带内的水流可能导致它们充当次垂直管道。断层可以起到密封旁路系统的作用，使常规油气系统中的隔间得以连接。断层还可以为非常规储气藏的天然气流动提供管道，减少现有的经济天然气；或者为水进入非常规油井提供途径，增加水的产量和随之而来的环境影响。因此，迫切需要开发新的工作流程和工具，以量化特定地下断层的断层内流动风险。断层带内流动的风险受到断层的内部结构、断层岩石的岩石物理性质以及断层带内机械和化学过程(断层成岩作用)相互作用的影响。后者是断层内流动研究最少的方面。犹他州的Little Grand Wash和Iron Wash断层分别为非常规和常规油藏中的断层提供了地表类似物。这些地点是描述限制断层内流动的过程的极好的天然实验室：研究小组从地表暴露和井(科学和工业)收集了两个地点无与伦比的数据，并拥有断层带结构的广泛数据集，断层岩的地下样本。地下样品允许探索适当的方法来校正风化对表面类似物的影响。这位博士生将收集新的现场数据，以调查地球化学反应对断层岩石的力学响应和断层岩石的水力性质的影响。他们将使用岩石学、扫描电子显微镜技术以及全岩石化学和同位素分析来约束断裂带的成岩作用；使用Strathclyde开发的最先进的流动模型来调查可能的断层内流动情景的范围；在Strathclyde地球力学实验室收集新的机械数据；并开发用于断层内流动的预测工作流程/工具。最后，他们将根据文献中的行业数据集和NERC CDT合作伙伴提供的数据来验证该工具。

Cross-fault flow properties of fault zones have long been studied to constrain their ability to hold a hydrocarbon column. However flow within fault zones can lead them to act as sub-vertical conduits. Faults can act as seal bypass systems, permitting linkage of compartments in conventional hydrocarbon systems. Faults can also provide conduits for gas flow out of unconventional reservoirs, reducing the economic gas in place; or provide pathways for water into unconventional wells, increasing water production and the consequent environmental impacts. There is therefore an urgent need to develop new workflows and tools for quantifying the risk of within-fault flow for a given subsurface fault.The risk of flow within fault zones is affected by the internal structural architecture of the fault, the petrophysical properties of the fault rocks and the interplay of mechanical and chemical processes within the fault zone (fault zone diagenesis). The latter is the least-studied aspect of within-fault flow. The Little Grand Wash and Iron Wash faults, Utah, provide surface analogues for faults in unconventional and conventional reservoirs respectively. The sites represent excellent natural labs for characterising the processes that constrain within-fault flow: the research team have collected unparalleled data at both sites from surface exposures and wells (both scientific and industry) and have extensive datasets of fault zone structure subsurface samples of fault rocks. Subsurface samples allow exploration of the appropriate ways to correct for the effect of weathering on surface analogues. The PhD student will collect new field data to investigate the effect of geochemical reactions on both the mechanical response of the fault rocks and the hydraulic properties of the fault rocks. They will constrain the fault zone diagenesis using petrological,SEM techniques and whole-rock chemical and isotopic analyses; use state of the art flow modelling developed at Strathclyde to investigate the range of likely within-fault flow scenarios; collect new mechanical data in Strathclyde geo-mechanics labs; and develop a predictive workflow/tool for within-fault flow. Finally they will validate this tool against industry datasets both in the literature and provided by NERC CDT partners.