Drilling Heat Maps for Active Temperature Management in Geothermal Wells

Abstract

Abstract Geothermal (GT) energy has gained much attention as a promising contributor to the energy transition for its capacity to provide a reliable, environmentally friendly source of baseload power. However, drilling high-temperature reservoirs presents significant technical and economic challenges, including thermally induced damage to bits and downhole tools, increasing drilling time and cost. This paper introduces the benefits of drilling heat maps for pro-active temperature management in GT wells during the well planning phase and the real-time drilling operations phase to avoid thermally induced drilling problems. This study uses a transient hydraulic model integrated with a thermal model to predict the bottom hole circulating temperature (BHCT) while drilling GT wells. The model was used to generate a large volume (1000's) of case scenarios to explore the impact of various cooling and other heat management strategies on downhole temperature, covering a wide range of drilling parameters. Results were captured, visualized, and analyzed in convenient heat maps, using the Utah Forge GT field as an example, illustrating the advantages of using such heat maps in GT well construction and real-time operations. Model validation with Forge 16A(78)-32 well data and Hasan and Kabir's well temperature model show very good results, with a mean absolute percentage error (MAPE) of less than 3.2%. 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 GT wells was observed with mud type, mud weight, and mud viscosity. In addition, insulated drill pipe (IDP) technology was found to significantly reduce BHCT (14-44% on average for Forge scenarios) compared to conventional drill pipe (CDP), particularly in wells with extended measured depth 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 optimum temperature management during the GT well design phase. Real-time heat maps, on the other hand, are valuable for facilitating active temperature management and providing real-time guidance for optimum drilling parameters during daily drilling operations. In general, heat maps can help to avoid drilling problems related to high temperature, thereby helping to facilitate safe and cost-efficient development of GT resources.