Nuclear magnetic resonance logging: Example applications of an emerging tool for environmental investigations

Abstract

Nuclear magnetic resonance (NMR) geophysical tools have been widely used in the petroleum exploration industry since the 1960s and have improved significantly in the last two decades.These tools can provide estimates of bulk porosity and fluid content, quantification of bound versus mobile fluids, and estimates of hydraulic conductivity (K). Although the size and cost of oil-field tools historically limited their use for near-surface applications, smaller and more economical downhole NMR logging tools are now available for detecting and characterizing the formation water content and K to support environmental and groundwater resource investigations. These tools can be deployed using direct-push drilling techniques or they can be lowered into existing open borings or wells with nonconductive polyvinyl chloride casings and screens.In many cases, using the tool in existing wells offers a safer and more cost-effective alternative compared to drilling new boreholes. For environmental investigations, NMR can provide useful high-resolution quantitative hydrostratigraphic information that can provide additional valuable data to further inform and refine the conceptual site model. This paper highlights several NMR field investigations that demonstrate the viability of this technology as a site characterization tool for near-surface investigations. NMR measurements were compared to data from lithologic logs, cone penetrometer testing data, and prior field hydraulic tests. Use of NMR to detect vadose zone water, including previously unidentified perched groundwater zones, provided hydrostratigraphic details that could not be gleaned from historical well drilling logs and were used to evaluate drainable pore water versus pore water bound in small pores by capillary forces or electrochemically clay-bond water. NMR also produced K estimates similar to those from conventional hydraulic tests, but the improved vertical resolution from NMR provided additional information regarding the vertical heterogeneity of the formation along the entire length of the well or borehole. Additionally, bench-scale tests are presented that confirm the capability for NMR to reliably detect and quantify light nonaqueous phase liquid saturation (specifically diesel fuel and weathered gasoline) in situ. The field tests combined with bench-scale testing results affirm the applicability and potential for NMR as a practical characterization tool that should increasingly be utilized in environmental investigations. K E Y W O R D Sconceptual site model, environmental investigations, groundwater, LNAPL, mill tailings, nuclear magnetic resonance imaging, remediation, vadose zone INTRODUCTIONOver the past decade, it has become more widely understood that more detailed understandings of the hydrostratigraphic framework are needed to support conceptual site model development, remediation system design, and system operation/optimization, particularly for complex geological settings. There are several high-resolution tools and techniques that have been developed ...

Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

“…The capacity to fit such a simple and predictive expression encompassing the relaxation and mechanical strength properties of both tap water and hypersaline water hydrated CPB materials exhibiting variable binder content is clearly highly desirable; indeed, this expression facilitates the prediction of CPB mechanical strength properties based on the measurement of NMR relaxation times alone. It follows that such correlations provide a potential avenue for the assessment of industrial site CPB formations using NMR logging tools or single sided magnet-based spectrometers [26,[49][50][51].…”

Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

“…The capacity to fit such a simple and predictive expression encompassing the relaxation and mechanical strength properties of both tap water and hypersaline water hydrated CPB materials exhibiting variable binder content is clearly highly desirable; indeed, this expression facilitates the prediction of CPB mechanical strength properties based on the measurement of NMR relaxation times alone. It follows that such correlations provide a potential avenue for the assessment of industrial site CPB formations using NMR logging tools or single sided magnet-based spectrometers (Boguszynska et al, 2005;Kleinberg et al, 1992;McDonald et al, 2007;Spurlin et al, 2019). Figure 9: Correlation of a) 〈 1 〉 and b) 〈 2 〉 NMR relaxation times against CPB UCS data.…”

The Key Factors for the Fate and Transport of Petroleum Hydrocarbons in Soil With Related in/ex Situ Measurement Methods: An Overview

“…This technique has widely used in lithology to see fluids (such as LNAPLs) and gas distribution in porous media (Behroozmand et al, 2015). The very recent development of small-diameter, economical, and portable NMR tools (Spurlin et al, 2019) now permits the non-invasive use of this technology within existing polyvinyl chloride (PVC)-cased well infrastructure or open holes, which provides repeatability for long-term monitoring with low costs, as well as a direct-push approach that enables reconnaissance PH contaminated site characterisation. The physical principle of NMR logging is the same principle underlying magnetic resonance imaging technology used in medicine and NMR spectroscopy in chemistry, by emitting a series of radio-frequency pulses and recording the returning signal, referred to as "spin echoes" and the NMR tool measures the NMR response in the sensitive zone.…”

“…The characteristics of the measured NMR signal reflect the quantity of hydrogen protons, where the total amplitude of the signal is directly proportional to the total amount of groundwater or PHs. NMR has been effectively applied to geology applications for soil water content and permeability characterisation (Spurlin et al, 2019). There is little difference in the detection of petroleum hydrocarbon fluids and water.…”