Integrated geological, geophysical, and hydrological study of field-scale fault-zone cementation and permeability

现场尺度断层带胶结和渗透性的综合地质、地球物理和水文研究

• 批准号: 1557232
• 负责人: Glenn Spinelli
• 金额: $ 56.76万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1557232&HistoricalAwards=false
• 关键词: Integrated; geological; geophysical; hydrological; study

Because faults can be barriers to underground fluid flow, they influence groundwater supply, contaminant transport, petroleum production, and underground waste storage. Natural cements commonly precipitate along fault zones; these cements can dramatically inhibit fluid flow across a fault. However, determining the distribution of fault zone cements is difficult. As a result, fault-zone cementation is typically not accounted for in estimates of the impact of faults on fluid flow. This study aims to take advantage of unique electrical properties of natural cements to characterize the three-dimensional spatial distribution of cement for an exceptionally well-exposed fault zone. Then, the hypothesis that the degree and continuity of fault-zone cementation is a key control on fluid flow will be tested by drawing water from wells adjacent to the fault. The results of this project can be applied to better understand contaminant transport in faulted aquifers, the characterization of hydrocarbon reservoirs, and induced seismicity associated with wastewater injection. Undergraduate and graduate students will be involved with all stages of the project, which will enhance education for underrepresented minorities at New Mexico Tech (NMT), a Hispanic-serving institution with a focus on science, technology, engineering, and mathematics (STEM) fields. In addition, the geophysical equipment and groundwater wells used in this project will be long-lasting teaching resources both for NMT and for summer field courses sponsored by other universities.The objectives of this project are to characterize field-scale permeability across a fault and link the hydrogeologic behavior of the fault to spatial variations in the degree of fault-zone cementation. The central hypotheses are: 1) there are more pronounced variations in the degree of cementation down-dip than along the strike of the fault because the up/down-section variations in grain size are larger than those along strike, and 2) extensive cementation does not reduce cross-fault permeability at the field-scale (i.e. the de facto hypothesis for hydrogeologic models that neglect the potential effects of fault-zone cementation). The proposed project comprises: 1) characterizing the degree and extent of cementation along the surface exposure of the fault; 2) collecting resistivity and chargeability data in transects across the fault, deriving empirical relationships between the degree of fault-zone cementation and normalized chargeability for shallow portions of the fault, and using those relationships to map the estimated degree of cementation for deeper portions of the fault; 3) coring the fault at depth to confirm the degree of cementation; and 4) conducting well tests to determine permeability across the fault in both strongly- and weakly-cemented sections. The study will generate geologically based geophysical observations, providing a unique 3D map of cementation patterns from the land surface to ~30 m depth, in transects covering 700 m along the strike of the Loma Blanca fault. Interpreting well tests across the fault in the context provided by the geologic and geophysical observations will allow for the development of a holistic view of fault-zone permeability, improving predictive models of the hydrogeologic impacts of faults.

由于故障可能是地下流体流动的障碍，因此它们会影响地下水供应，污染物运输，石油生产和地下废物存储。天然水泥通常沿断层区域沉淀；这些水泥可以极大地抑制跨断层的流体流动。但是，难以确定断层区域的分布。结果，在估计断层对流体流动的影响时，通常不考虑断层区胶结。这项研究旨在利用自然水泥的独特电气特性来表征水泥的三维空间分布，以实现暴露良好的断层区域。然后，假设断层区胶结的程度和连续性是对流体流量的关键控制，将通过从与断层相邻的井中抽水来测试流体流动的关键控制。该项目的结果可用于更好地了解断层含水层中的污染物运输，碳氢化合物储层的表征以及与废水注入相关的诱导地震性。本科生和研究生将参与该项目的所有阶段，这将增强新墨西哥理工学院（NMT）的教育，这是一家西班牙裔服务机构，重点是科学，技术，工程，工程和数学（STEM）领域。此外，该项目中使用的地球物理设备和地下水井将是NMT和其他大学赞助的夏季野外课程的持久教学资源。该项目的目的是将故障的野外渗透性表征，并将故障的水理学行为链接到缺点的水平变化与缺陷术的空间变化。中心假设是：1）胶结下垂程度的变化比沿断层的打击更为明显，因为晶粒尺寸的上/下部分变化大于沿罢工的变化，而2）广泛的固化并不能降低野外大规模的交叉越野渗透性（即，对氢化模型的事实假设造成了造成的局部效果，而不是造成了造成的差异。拟议的项目包括：1）表征沿断层表面暴露的胶结程度和程度； 2）在断层跨断层的样带中收集电阻率和外观数据，从而导致断层胶结程度和断层浅层的归一化荷兰的经验关系，并使用这些关系来绘制估计的胶结度，以绘制出更深部分故障的深度； 3）在深度上加油以确认胶结度； 4）进行井测试以确定在强和污染的切片中跨断层的渗透性。这项研究将产生基于地质的地球物理观测，从沿Loma Blanca断层的罢工覆盖700 m的样带，提供从陆地表面到〜30 m深度的独特的3D胶结图图。在地质和地球物理观察提供的环境中，解释跨断层的井测试将允许对断层区渗透性的整体观点发展，从而改善了断层的水文地质影响的预测模型。