Review of Offshore Geothermal Projects: Past Projects and Current Ideas

Abstract

Offshore geothermal energy production is a natural progression of thought when discussing the future of geothermal energy as the baseload power solution for a decarbonized future. This is a difficult and expensive development, though. Here we attempt to answer the question: how can we make offshore geothermal energy work? Previous research examined offshore geothermal energy production as a green energy power solution. This previous work examined geothermal energy in volcanic settings, utilizing high enthalpy resources often associated with onshore power plants. High-level calculations suggest built-for-purpose offshore geothermal platforms will be too expensive even for a world class geothermal resource. Alternatively, geothermal energy has been suggested as a solution to repurpose existing oil and gas infrastructure, which saves development cost of the geothermal resource while also extending the life of offshore platforms, ultimately delaying the financial burden of decommissioning. For repurposing scenarios, we examined public production data from the Corpus Christi Bay and the Galveston Bay in Texas Coastal waters of the Gulf of Mexico for geothermal power potential. Geothermal power potential is calculated, including cost of energy and project financials, are examined. Similarly, data from the North Sea is analyzed for power production potential and the project financial potential at a high level. In both the Gulf of Mexico and the North Sea, the technoeconomic feasibility is borderline economic for optimistic scenarios, when repurposing both wells and platforms for geothermal energy production. Many wells were drilled for hydrocarbon production, meaning the intersected reservoirs are not optimized for hot water production, and ultimately have insufficient flow rates for maximum energy production. Alternatively, recompleting wells into more promising zones have better economics because of greater power production with still moderately cheap wellbore recompletion costs. If both new drilling and repurposing existing wells are expected to be uneconomic, how can we make offshore geothermal energy work? Offshore geothermal energy needs to be a multipurpose solution, which offers baseload clean energy and prolonged existing infrastructure life. There are opportunities to be this multipurpose solution, though. This first option is development of a Synthetic Geothermal Reservoir (SGR) as energy storage to increase offshore wind penetration. The second option is as a niche baseload power for other infrastructure repurposing ideas such as carbon dioxide storage, hydrogen generation, aquaculture, personnel training, and potentially others. Similarly, new oil platforms should be built with a hydrocarbon-geothermal coproduction design so that the geothermal energy can be a multipurpose solution from initial production. This option requires forethought and buy-in from existing energy producers. In all these scenarios, geothermal energy is the baseload clean energy, decreasing the environmental footprint of the respective industry, and prolonging the life of the offshore infrastructure.