Magnetic Resonance (NMR) is an important technology that is vital for successfully conducting groundwater resources projects. In fact, NMR is the only technology that is capable of measuring groundwater directly. Both surface based NMR and borehole NMR logging have applicability in groundwater resources projects.
There are three main areas where NMR plays a key role in groundwater applications: Prospecting, Economic Extraction and Aquifer Management.
This involves determining the location and characteristics of aquifers in order to assess the amount of groundwater, the size & location of aquifers, and key factors such as permeability & porosity that impact how readily the water can be extracted. While other technologies such as aerial electromagnetic surveys can be helpful in making initial assessments of aquifer locations, magnetic resonance is the only way to directly measure detailed groundwater characteristics needed to adequately assess the amount, location and extractability of the water.
Surface NMR tools such as the GMR and GMR Flex provide the only existing non-invasive method for directly measuring groundwater characteristics to depths of up to 500 feet (150 meters). Surface-based direct measurement of groundwater can be particularly valuable for assessing relatively large areas and acquiring unambiguous data on aquifers, without the time and expense of drilling multiple holes.
Borehole NMR Logging tools such as Javelin Wireline Slim, Javelin Wireline Max, and Dart Portable NMR Logging Tool, all provide downhole, high-resolution, logging of groundwater characteristics at depths up to 600 meters. NMR borehole logging can obtain data at multiple frequencies, providing up to three discrete diameters of investigation (depending on the tool), thereby reaching well beyond the “drilling disturbed zone” to directly characterize aquifers. Borehole NMR can also be used in conjunction with industry-standard direct push equipment to quickly acquire data without the disturbance, tailings and expense associated with drilling multiple holes.
Finding groundwater is only the first step, after which you need to determine the hydraulic characteristics of the aquifer(s) in order to predict the yield and behavior that are key to assessing the economic viability of extraction. The NMR tools described above can help you acquire and analyze detailed porosity and permeability data to decide on target well locations and plan extraction processes for optimal production efficiency. NMR data also helps with designing the wells, such as deciding on the target zones for locating well screens, screening out zones that you specifically want to avoid, etc.
With aquifer depletion becoming an increasingly important issue and regulatory agencies keeping a close eye on groundwater extraction, the need for ongoing analysis is critical for long-term aquifer management. Once again, NMR tools play a key role in the ongoing management processes. Borehole NMR tools can be used in any existing well hole to periodically acquire new data to assess changes to the aquifer in order to the track amount of water extracted and remaining, and any significant changes in the aquifer’s extent or connections with other aquifers. Direct measurement of these characteristics are key to both continued economic operation of the extraction process and compliance with data reporting to applicable regulatory bodies.
An additional element of groundwater management that is becoming more prevalent is proactive aquifer storage and recovery (ASR), which is vital for extending useful life of extraction programs by replenishing aquifers. As detailed in this applications spotlight on Denver Colorado’s Aquifer Storage and Recovery program, NMR can use existing boreholes to gather current data to help identify optimal injection sites for recharging underground aquifers.
- READ: Case Study – Urban Groundwater Resources Management in Arizona
- READ: Case Study – Sustainable Groundwater Management in Indian Wells, CA
- READ: Case Study – Aquifer Storage and Recovery (ASR) at Denver Water
- WATCH: Applications Spotlight Video – Denver ASR Project
- WATCH: Video on Direct Push and NMR Logging