Integrated reservoir and production system modeling of geothermal energy extraction at the Aquistore CCS site in Canada

Mitigating the global climate crisis is the greatest challenge facing humanity this
century. The transition of current energy systems towards carbon-neutral energy
is inevitable. Renewable energy sources, particularly those that are both baseload-
and dispatch-capable, such as geothermal energy, are essential to replace current
energy systems that emit large amounts of CO₂. In addition, permanent isolation
of CO₂ from the atmosphere, using carbon capture and sequestration (CCS), is
indispensable to limit global warming to 1.5°C.
To enable the full potential of geothermal energy extraction and of CCS, their
efficiencies need to be improved. One possibility is to integrate both technologies.
Using CO₂ as the geothermal energy extraction fluid approximately doubles energy
generation rates, compared to conventional, brine-based geothermal systems under
our base-case conditions. Such CO₂ Plume Geothermal (CPG) systems reinject
the produced CO2, eventually sequestering all CO₂ underground. Extracting the
geothermal energy from the CCS reservoir results in additional CO₂ storage poten-
tial, as, for example, the CO₂ density increases and the overall reservoir pressure
decreases. The CPG-generated heat, electricity, and/or revenue could “subsidise”
CCS operations. Consequently, CPG could increase both the geothermal energy
and the CCS capacities.
Our CPG feasibility study combines an integrated production system modeling
approach with a history-matched reservoir model of an active CCS site (Aquistore,
Canada). The integrated modeling approach is used to account for all relevant
processes, from well-bore pressure and temperature drops to multi-phase, multi-
component fluid flow in the reservoir to fluid separation, power generation, and
continuous with reinjection of CO₂ at the land surface, in a fully implicit matter.
Our results suggest that stable CO₂ circulation, extracting geothermal energy
between the underground CO₂ plume in the saline reservoir and the land surface,
is possible. Furthermore, we see additional CO₂ storage potential, caused by the
circulation of CO₂. Our simulations indicate that Aquistore may provide a unique
opportunity for pioneering a CPG field test.