Drilling Heat Maps for Active Temperature Management in Geothermal Wells

Abstract

Summary Geothermal energy has gained much attention as a promising contributor to the energy transition for its ability to provide a reliable, environmentally friendly source of heat and baseload power. However, drilling high-temperature (HT) reservoirs presents significant technical and economic challenges, including thermally induced damage to bits and downhole (DH) tools, increasing drilling time and cost. This paper introduces drilling heat maps for proactive temperature management in geothermal wells during well planning and real-time drilling operations phases to avoid thermally induced drilling problems. This study uses a transient hydraulic model integrated with a thermal model to predict the bottomhole circulating temperature (BHCT) while drilling geothermal wells. The model is used to generate a large volume (1,000s) of case scenarios to explore the impact of various cooling and other heat management strategies on the BHCT in the Utah FORGE field, used here as an example, covering a wide range of drilling parameters. Results are captured, visualized, and analyzed in convenient heat maps, illustrating the advantages of using such heat maps in geothermal well construction and real-time operations. Model validation with FORGE 16A(78)-32 well data and a west Texas case scenario shows good agreement between the modeling results and experimental data, with a mean absolute percentage error (MAPE) of less than 4%. There is a clear logarithmic relationship between the drilling flow rate and BHCT at a constant mud inlet temperature and a linear relationship between the mud inlet temperature and BHCT at a constant drilling flow rate. Pronounced variation of BHCT in geothermal wells is observed with mud type, mud weight, and mud viscosity. In addition, insulated drillpipe (IDP) technology is found to significantly reduce BHCT (14–44% on average for FORGE scenarios) compared to conventional drillpipe (CDP), particularly in wells with extended measured depth (MD) where other heat management technologies and strategies become less effective. Drilling heat maps can alert drilling engineers to strategies with the highest BHCT-lowering impact, allowing focused technology selection and decision-making regarding optimal temperature management during the geothermal well design phase. In addition, real-time heat maps are valuable for facilitating active temperature management and providing real-time guidance for optimal drilling parameters during daily drilling operations. In general, heat maps can help to avoid drilling problems related to the combination of HT and temperature limitations of DH equipment, which will benefit the safe and cost-efficient development of geothermal resources.