A Robust Screening Tool to Repurpose Hydrocarbon Wells to Geothermal Wells in Oklahoma

Abstract

Geothermal energy is a renewable energy that has vast potential due to its reliable energy supply. Its development has been related to specific geological locations with extremely high temperatures. However, depleted oil and gas reservoirs can produce geothermal energy from the subsurface. Repurposing this well can be a valuable tool to generate sustainable and steady energy for the state of Oklahoma due to its large number of wells used in the Oil and Gas industry. In fact, abandoned oil and gas wells are suitable candidates for conversion as these are environmental liabilities. The challenge is selecting which wells are good candidates for geothermal applications. This study aims to build an evaluation methodology to filter wells with a high potential for geothermal production. Three factors, temperature, proximity to the end user, and well integrity, are analyzed for evaluating possible candidates. Three datasets of temperature gradients were gathered from the Oklahoma Geological Survey, abandoned oil and gas wells from the Oklahoma Corporate Commission, and cities’ locations and populations from the US Census Bureau were combined. The objective is to evaluate the wells in Oklahoma to select promising candidates for repurposing for geothermal applications. Temperature prediction was made using Spatial Interpolation using Thiessen polygons, K-nearest Neighbors, and Kriging. K-nearest Neighbors exhibited the highest performance based on the evaluation metrics. Temperature prediction at an average true vertical depth of 6000 ft showed 26.7% or 4292 wells have more than 150 °F and can be converted for geothermal production. The shortest distance heuristic algorithm was used to calculate the shortest distance of each well to any city in Oklahoma. Before conversion, an evaluation of the well is required to assess the volumes and condition of the well; methods include statical analysis, logging, and evaluation techniques. These are discussed in this study. This study shows the high number of wells with the potential to be converted for geothermal applications converting a liability and environmental concern to a renewable energy-producing asset.