An Integrated Technical Framework for Assessing Offshore Geothermal Opportunities in and Around Existing Oil and Gas Assets
Authors: Pasturel K. , Barres-Montel V. , Harrar W. , Watt K. 
Published: September 2023

This paper provides an overview of a Geothermal Assessment Project (GAP) completed to assess the geothermal energy resource in and around an operational HPHT field on the UKCS. It demonstrates a new methodology to identify, assess and determine the amount of electrical power that might be realised from the geothermal resource and associated field infrastructure, and investigates both existing and future opportunities.

Geothermal energy adoption into oil and gas net-zero portfolios remains relatively unexplored. This paper shares the results of the design and implementation of a novel integrated workflow to assess and evaluate the geothermal energy potential of producing offshore oil and gas assets from subsurface, wells, and topsides perspectives. The workflow is designed to allow operators to determine potential electrical power production from geothermal sources within existing field infrastructure alongside a model of the opportunity it provides to reduce CO2 emissions.

Three geothermal production scenarios are defined, that are: proven co-produced fluid reserves, contingent co-produced and enhanced fluid resources and prospective exploratory geothermal resources. Existing and sanctioned production forecasts were used along with reservoir modelling to examine aquifer behavior and the ability for enhanced and sustained water production. Screening and complexity matrices were applied to identify and rank relevant reservoir plays and candidate wells. Process flow diagrams were interrogated to establish potential tie-in points for heat to power equipment and equipment characteristics required for enhancing heat to power generation were considered. The overall opportunity was also risk assessed from a flow assurance perspective.

Results of the study are discussed in terms of the challenges and opportunities that exist to co-produce geothermal energy within the constraints of an established oil and gas development. It illustrates the value of developing a structured framework to allow assessment and benchmarking of geothermal resources. Furthermore, the nuances of modelling aquifer response and the behavior of enhanced water production as it travels from the reservoir to the process facilities are considered. The study shows that the production characteristics that favor geothermal energy adoption on a producing asset are elevated temperature profile, high water production rates, presence of injection support and/or artificial lift, and production lifespan.

This study identified, assessed, and compared geothermal development models that might support geothermal co-production or repurposing of hydrocarbon assets. The result was a clear picture of near and long-term geothermal power options that are replicable across asset portfolios, that provides operators with additional strategies when considering lifecycle field activities and underlines the potential commercial value of including geothermal in field development. The study concludes that opportunities exist to generate meaningful geothermal power and offset emissions using existing production, examples of which will be presented and discussed.