Two-Stage Mud Chiller Thermohydraulic Model Development and Validation

Abstract Cooling the drill bit and lubrication are among the primary functions of drilling mud. Consequently, mud temperature increases as it absorbs the heat associated with drilling friction and the natural geothermal heat present in the earth’s crust. If the mud overheats, its properties begin to degrade, affecting its basic functionality. Downhole tools begin to malfunction, and elastomers used in well control equipment begin to degrade. High-temperature mud also poses a risk to the safety of rig personnel. To prevent these problems, drilling mud temperature is reduced either by passively circulating in tanks or actively cooling using mud chillers. Previous case studies [1], [2] have described the use of two-stage mud chillers to successfully reduce drilling fluid temperature (Fig. 1) in high-pressure/high-temperature (HP/HT) wells where downhole temperatures are greater than 300°F (149°C). This fully automated mud chiller has a two-pass configuration that allows high-temperature mud to be pre-cooled by fans and then chilled again by a highly efficient refrigeration unit. The effectiveness of the mud chiller depends on various factors, including mud properties, flow rates, and ambient temperature. These factors can vary significantly, making it difficult to predict the performance of a mud chiller. However, performance prediction is vital at the design stage and for optimally managing implementation in varied operating environments.