Vista Clara, ConeTec, Geoprobe and Georgia Tech researchers recently partnered to deploy a Vista Clara Dart Nuclear Magnetic Resonance (NMR) probe via a cone penetrometer test (CPT) rig to measure water content and porosity in a mine tailings facility. Vista Clara geophysicists collected CPT-NMR logs to depths of 75ft in tailings material at the mine site. Additionally, they logged NMR in an adjacent cased hole using a wireline-based Javelin system for comparison and validation of NMR data collected using direct push and traditional drilling. This is possibly the first deployment of an NMR logging tool via a CPT vehicle.
The Dart NMR logging tool provides direct, in-situ measurement of volumetric water content, porosity (e.g. void ratio) and pore size distributions with high resolution, precision and relatively low cost. These water bearing parameters, particularly the saturation and void ratio, are critical to the geotechnical and hydrological properties of tailings structures.
The direct push deployment used 2.25in Geoprobe drill rods deployed using a ConeTec CPT vehicle (shown in Figure 1). The drill string was pushed to depth, the Dart probe (shown in Figure 2) advanced to the bottom of the rod string, and NMR measurements taken in a stepwise manner while retracting the rod string.
One of the CPT-NMR logs is shown in Figure 3. Excellent agreement was achieved between the CPT-NMR logs and the Javelin NMR log performed in a nearby pvc-cased borehole hole.
Thanks to ConeTec, Georgia Tech, GeoLog LLC and Geoprobe Inc.
This work was supported by in part by US Department of Energy Grant number DE-SC0017096. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the US Department of Energy.