Monitoring saltwater influx into freshwater aquifers using measurements of spontaneous potential

使用自发电位测量监测盐水流入淡水含水层

• 批准号: NE/I018417/1
• 负责人: Matthew Jackson
• 金额: $ 9.48万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI018417%2F1
• 关键词: Monitoring; saltwater; influx; into; freshwater

Coastal aquifers are valuable resources of fresh water for domestic and industrial use. However, over-abstraction leaves them at risk of contamination by saltwater, which migrates into the aquifer in response to abstraction. Detecting and monitoring the movement of saltwater is difficult, as the methods currently available rely on data acquired at production or monitoring wells. Consequently, it is typically of low spatial resolution. Moreover, once saltwater reaches the production well(s), it is too late to take action; that region of the aquifer has already been contaminated. This problem is exacerbated in chalk aquifers owing to their dual porosity behaviour and high transmissivity. The aim of this project is to develop new technology, based on measurements of electrical potential (the so-called spontaneous- or self-potential), to detect and monitor the movement of saltwater during freshwater abstraction. The electrical potential is measured using electrodes installed at the earth surface and/or in production or monitoring wells. The advantage of the technique is that saline fronts may be monitored while they are several tens to hundreds of metres away from the monitoring location. Consequently, saline water moving into an aquifer may be detected before it reaches the abstraction well(s), allowing abstraction to be managed proactively so as to avoid widespread contamination of the aquifer. The innovative, multidisciplinary project builds on existing work undertaken at Imperial College, in which measurements of the spontaneous potential, acquired from electrodes permanently installed downhole, are used to monitor water movement in oil or gas reservoirs during production. The underlying rationale in hydrocarbon applications is similar, in that waterfronts may be monitored while they are several tens to hundreds of metres away from the production well, allowing production to be managed proactively so as to avoid excessive unwanted water. This is contaminated and so expensive to treat and dispose of. The project will provide new experimental data, which is required to model and interpret measurements of spontaneous potential in coastal chalk aquifers. The project will also use numerical modeling to determine whether the saline front can be detected and monitored, and over what distances and at what spatial and temporal resolution. Finally, the utility of the method will be demonstrated at a well-characterized chalk aquifer test site, via field experiments in which small volumes of saline water are injected and the resulting electrical signals are measured. This is an essential step to establish credibility prior to deployment in a commercial abstraction project. The results will be of direct benefit to UK plc, because they contribute to the sustainable management of water resources, helping to preserve and maintain these as demand continues to increase. See the attached document 'Case for Support' for further details of the scientific case, aims and objectives, and scope of work.

沿海含水层是家庭和工业用水的宝贵淡水资源。然而，过度抽取使它们面临被盐水污染的风险，盐水会随着抽取而迁移到含水层中。检测和监测盐水的运动很困难，因为目前可用的方法依赖于生产井或监测井获取的数据。因此，它通常具有低空间分辨率。此外，一旦盐水到达生产井，再采取行动就为时已晚；该地区的含水层已经受到污染。由于白垩含水层的双重孔隙行为和高透射率，这个问题更加严重。该项目的目的是开发基于电势测量（所谓的自发电势或自电势）的新技术，以检测和监测淡水抽取过程中盐水的运动。使用安装在地球表面和/或生产井或监测井中的电极来测量电势。该技术的优点是可以在距离监测地点几十到几百米的地方监测盐锋。因此，进入含水层的盐水可以在到达抽取井之前被检测到，从而允许主动管理抽取以避免含水层的广泛污染。这一创新的多学科项目建立在帝国理工学院现有工作的基础上，其中通过永久安装在井下的电极获得的自发电位测量用于监测生产过程中油气藏中的水运动。碳氢化合物应用的基本原理是相似的，即可以在距离生产井几十到几百米的地方对滨水区进行监测，从而可以主动管理生产，以避免产生过多的不需要的水。它已被污染，处理和处置成本高昂。该项目将提供新的实验数据，需要这些数据来模拟和解释沿海白垩含水层自发电位的测量结果。该项目还将使用数值模型来确定是否可以检测和监测盐锋，以及检测和监测的距离以及空间和时间分辨率。最后，该方法的实用性将在一个特征明确的白垩含水层测试地点通过现场实验得到证明，其中注入少量盐水并测量产生的电信号。这是在商业抽象项目中部署之前建立可信度的重要步骤。研究结果将使 UK plc 直接受益，因为它们有助于水资源的可持续管理，随着需求的不断增加，有助于保护和维护这些资源。有关科学案例、目的和目标以及工作范围的更多详细信息，请参阅随附的文件“支持案例”。