Characterization of the Geothermal Resource at Clarke Lake Field Northeast British Columbia

  • Author / Creator
    Renaud, Evan
  • Clarke Lake is a depleted gas fi eld developed in carbonate platform deposits of the Slave Point
    Formation (Middle Devonian) in northeastern British Columbia, Canada. It displays anomalously high reservoir temperature and strong water drive, making it a candidate for repurposing as a
    source of geothermal power. Porous and permeable reservoir near the platform margin developed
    through the hydrothermal alteration of host limestone to dolomite. A geothermal resource requires
    permeable reservoir rock that allows for fl ow rates that can sustain economic electricity generation. A depositional model in provides a basis for mapping the dolomite reservoir, and thus, permeability. Porosity and permeability measurements can be incorporated in a comprehensive suite
    of fl ow simulations to test how reinjected water affects geothermal power production.
    Nine depositional facies and two diagenetic facies are identifi ed, the former based on bioclast
    assemblages, rock types, texture and composition and the latter based on rock fabric and the
    degree of alteration to dolomite. Deposition of these facies occurred within lagoonal, reef-fl at and
    foreslope settings associated with a rimmed carbonate platform. Dolomitized lagoon, reef fl at,
    reef margin and shoal lithologies show enhanced porosity and permeability due to dissolution of
    stromatoporoid bioclasts, forming mouldic and vuggy porosity. Diagenetic facies show high permeability but reduced porosity as a result of precipitation of porosity-occluding dolomite, fl uorite,
    and sulphide minerals. High quality reservoir zones occur primarily at the reef margin, caused by
    fabric-selective hydrothermal alteration of carbonate sediments near the contact with shales of the
    Horn River and Muskwa formations.
    Correlation of core descriptions and wireline log data allow the Slave Point Formation to be separated into successions that infl uenced dolomitization: an initial shoal unit, S1, three subsequent
    reef units, R1, R2, R3, and terminal shoal units of D1, D2 and D3. Shoal units were deposited in
    the transgressive systems tracts, whereas reef growth units were deposited in the highstand systems tracts. An initial transgression deposited shoals of the S1 unit across the carbonate platform.
    As the rate of relative sea level rise waned, a well-defi ned reef margin developed at the platform
    edge, which infl uenced depositional energy across the platform top and allowed deposition of
    reef units (R1, R2, and R3). A subsequent transgression began to drown the reef, during which
    spatially restricted shoals, D1, D2 and D3, were deposited near the reef margin before the rate of
    relative sea level rise outpaced the rate of deposition.
    We assessed the viability of geothermal energy production by simulating the water temperatures
    in production scenarios that use different operation conditions, well confi gurations and grid sizes,
    and by applying a Monte Carlo approach to different porosity and permeability realizations. Both
    an injection-production well doublet and an array of 4 injection and 8 production wells were simulated. Temperature drops at production wells result from a migration of an injected cold water
    plume and are most strongly related to fl ow rate. Varying fl ow rates result in a temperature drop
    that ranges from 0.47 to 5.6 °C. Simulations using progressively fi ner grids predict longer thermal breakthrough time compared to coarser grids, while coarser grids predict greater temperature
    drops at the production well.
    The impact of thermal breakthrough at a geothermal production well is a reduction of the power
    potential. Reduced power potentials using doublet production-injection scenarios are 465 kWe at
    25 kg/s fl ow rates and 930 kWe at 50 kg/s fl ow rates, compared to baseline results (that assume
    no thermal breakthrough) of 511 kWe and 1036 kWe, respectively . The four injection-eight production well scenarios estimate a power production of 3456 kWe at 200 kg/s fl ow rates, compared
    to a baseline result of 4085 kWe without thermal breakthrough.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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