Approach Evaluates Geothermal Potential in Existing Oil and Gas Wells
Authors: Carpenter Chris 
Published: January 2023

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207801, “Geothermal Production From Existing Oil and Gas Wells: A Sustainable Repurposing Model,” by Oscar M. Molina, SPE, and Camilo Mejia, Enovate Upstream, and Mayank Tyagi, SPE, Louisiana State University, et al. The paper has not been peer reviewed.

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In the complete paper, the authors discuss an integrated cloud-based work flow aimed at evaluating the cost-effectiveness of adopting geothermal production in low- to medium-enthalpy systems either by repurposing existing oil and gas wells or by coproducing thermal and fossil energy. The work flow introduces an automated and intrinsically secure decision-making process to convert mature oil and gas wells into geothermal wells, enabling both operational and financial assessment of the conversion process, whether partial or complete.

Background
The strong projection of geothermal-market growth allows oil and gas companies to consider geothermal energy coproduction from existing wells. This process considers, first, full conversion of wells in depleted hydrocarbon-bearing formations and, second, partial conversion to enable coproduction of hydrocarbons and economical volumes of water (wells with high water cut are suitable candidates for the partial-conversion approach).
Aside from the financial gain resulting from repurposing candidate wells for geothermal production, the conversion process yields operational cost optimization by reducing the amount of wells in need of plugging and abandonment, extending the productive life of an otherwise depleted asset, and significantly reducing carbon dioxide emissions on location.

Methodology
The premise of the work flow is that candidate wells for conversion are producing hydrocarbons from low- to medium-enthalpy systems. The conversion from hydrocarbon to geothermal energy producer can be full or partial, meaning that a candidate well can produce water either by itself (full conversion) or alongside oil and gas (partial conversion). The authors discuss the fundamentals of the geothermal-conversion work flow, which is based on a well-structured and physics-informed decision-making process. Operational and financial metrics pertaining to the conversion process, whether partial or complete, are assessed by the work flow.
The proposed work flow focuses on the reliability of the surface-to-subsurface model and the production system to ensure the financial success of the conversion project in terms of the realizable heat production and associated cost of development. The decision-making part of the work flow considers technical-, social-, and environmental-effect metrics that ultimately translate into return on investment (ROI) for either conversion case for geothermal production. All components of the work flow are evaluated using artificial intelligence algorithms that will help reduce biases in the decision-making process.
The automated section of the work flow considers the assessment of the following components:
- Heat potential
- Integration of geological, petrophysical, and geophysical interpretation
- Predictive methods for reservoir characterization
- Dynamic reservoir modeling
- Environmental, social, and governance (ESG)
Each component is considered cloud-ready so that the entire work flow can be assembled in a cloud environment.