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<p>Borehole temperature logging has the potential to provide insights into the presence and origin of uranium deposits; however, subtle radiogenic signatures from deposits may be disrupted by flow between different hydrogeologic units in open boreholes. A methodological study is underway at the Geological Survey of Canada’s Deep Bedrock Borehole Calibration Facility in Ottawa, Ontario, to assess the influence of groundwater flow in open boreholes on the interpretation of geothermal and radiogenic effects. Measurement techniques include high-resolution, single and multi-sensor temperature logging, flowmeter testing, repeat thermal recovery logging, and temporary installation of pressure and temperature sensors behind a liner for 6&#xa0;months. In open, cross-connected boreholes, environmental (seasonal) thermal influences were observed to extend to 180&#xa0;m in depth, but once vertical flow was eliminated with a liner, the hetero-homothermic boundary was interpreted to lie between 40 and 50&#xa0;m. Horizontal thermal gradients were observed to change at different horizons, contributing to the conceptualization of hydrogeological units at the site. Flow magnitude (0.0–3.3 l/min) and direction were observed to be influenced by deeper hydraulic pressures triggered by precipitation or snowmelt events. As a result, the identification of dynamic conditions required repeat and/or continuous monitoring. Although site-wide temperature patterns are similar, variation on the order of hundredths to a few degrees Celsius between wells is observed, influenced by each borehole’s intersection with a complex fracture network. Experimentation and observations at the test site led to the development of a temperature-logging methodology suited for deep, narrow-diameter exploration boreholes.</p>

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High-resolution temperature logging to support ore systems research in dynamic hydrogeological settings

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月27日

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  • Heather Crow,
  • Peeter Pehme,
  • Beth Parker,
  • Hazen Russell

摘要

Borehole temperature logging has the potential to provide insights into the presence and origin of uranium deposits; however, subtle radiogenic signatures from deposits may be disrupted by flow between different hydrogeologic units in open boreholes. A methodological study is underway at the Geological Survey of Canada’s Deep Bedrock Borehole Calibration Facility in Ottawa, Ontario, to assess the influence of groundwater flow in open boreholes on the interpretation of geothermal and radiogenic effects. Measurement techniques include high-resolution, single and multi-sensor temperature logging, flowmeter testing, repeat thermal recovery logging, and temporary installation of pressure and temperature sensors behind a liner for 6 months. In open, cross-connected boreholes, environmental (seasonal) thermal influences were observed to extend to 180 m in depth, but once vertical flow was eliminated with a liner, the hetero-homothermic boundary was interpreted to lie between 40 and 50 m. Horizontal thermal gradients were observed to change at different horizons, contributing to the conceptualization of hydrogeological units at the site. Flow magnitude (0.0–3.3 l/min) and direction were observed to be influenced by deeper hydraulic pressures triggered by precipitation or snowmelt events. As a result, the identification of dynamic conditions required repeat and/or continuous monitoring. Although site-wide temperature patterns are similar, variation on the order of hundredths to a few degrees Celsius between wells is observed, influenced by each borehole’s intersection with a complex fracture network. Experimentation and observations at the test site led to the development of a temperature-logging methodology suited for deep, narrow-diameter exploration boreholes.