Repurposing abandoned wells for geothermal energy: Current status and future prospects

Abstract

A debate rages as to whether abandoned oil and gas wells have to be sealed to prevent methane leakage – a potent greenhouse gas – or whether the valuable infrastructure can be repurposed for environmental benefit. One viable solution is to repurpose such wells for the recovery of low-grade geothermal energy and simultaneously produce a revenue stream, staunch fugitive emissions and maintain workforce engagement. This avoids the major upfront costs of drilling and significant risks of non-transmissive reservoirs that remain major obstacles in the development of geothermal energy. Regions of extensive hydrocarbon exploration are often close to market and with significant geothermal gradients. Repurposing must accommodate local energy demand, potential markets, existing infrastructure and technical challenges. So far, most studies have been scattered or focused on the viability of converting a specific oilfield. This work integrates the accomplishments and key challenges faced from projects that converted hydrocarbon production in geothermal renewable energy and establish guidelines to assist future projects. Conversion strategies are discussed for open-loop systems with co-production and enhanced geothermal systems and for true closed-loop systems. Five key challenges relate to well selection, data availability, underground infrastructure, well integrity and regulatory factors. Potential challenges in inspection and preparation of these wells in terms of well integrity and productivity with possible remedies are also discussed. Pilot projects and feasibility studies that have been performed worldwide confirm the viability of this concept but at low efficiency, paving the way for future innovations in this area.