A Feasibility Assessment of Heat Energy Productivity of Geothermal Wells Converted from Oil/Gas Wells

Abstract

The mitigation of greenhouse gas emissions necessitates a shift from fossil fuel to environmentally friendly energy, such as geothermal energy. It is advantageous to retrofit end-of-life oil/gas wells for geothermal energy extraction. Prior to repurposing depleted wells into geothermal wells, it is imperative to conduct the heat-energy potential assessment. In this work, an analytical model was developed for this purpose. A case study was conducted using the model and the data from a well in North-west Louisiana for a feasibility assessment. A sensitivity study was performed with the model to identify major factors affecting well productivity. The result of the case study shows that reverse circulation is 35% more efficient than direct circulation for improving the heat-energy productivity of geothermal wells converted from oil/gas wells. The sensitivity analysis revealed that well productivity increases with higher injection rates and greater horizontal wellbore lengths. Additionally, well productivity rises in correspondence with reservoir temperature as well as the temperature of the injected water. However, well productivity decreases as the thermal conductivity of the tubing insulation increases. Counteracting this trend, well productivity increases with thicker tubing insulation layers. This study furnishes engineers with an easy-to-use tool for predicting the heat-energy deliverability of wells converted from end-of-life oil/gas wells.