Geothermal Resource Characterization and Development of the Clarke Lake Gas Field, Fort Nelson, B.C., Canada

The Clarke Lake depleted gas field in northeastern British Columbia displays anomalously high reservoir temperature, high permeability, and a strong water drive, making it suitable to investigate the potential of repurposing the field as a source of geothermal electrical power. The gas field occurs in carbonate sediments of the Slave Point Formation, which were deposited within a rimmed carbonate platform environment flanking the Horn River Basin during Givetian time. The development of porous and permeable reservoir resulted from hydrothermal alteration of parent limestone to dolomite due to the movement of halite- and gypsum-saturated brines through aquifers toward the reef margin. Hydrothermal alteration is common throughout the Keg River, Sulphur Point and Slave Point formations, which constitute the Presqu’ile Barrier, a Devonian carbonate barrier reef extending from northeastern B.C. to Pine Point, NWT. These same formations make up the primary Clarke Lake Reef geothermal reservoir. An initial estimate of the total field-wide potential for electricity generation was found to be 34 MW (Walsh, 2013). An engineering level feasibility study is underway to prove the viability of the geothermal resource for commercial development. The detailed study is being performed of the geothermal resource properties including structure, thickness, permeability, porosity, temperature, brine and gas geochemistry. A three-dimensional conceptual model, analytical well simulations and numerical geothermal reservoir simulations are being created and run to test potential well field designs and estimate power production. A geothermal reservoir characterization well doublet has been designed to prove the resource and support further modeling. Drilling and testing of the doublet wells are proposed for the 3rd and 4th quarter of 2020.