(1) (n.) Drilling. The temperature of the circulating fluid (air, mud, cement or water) at the bottom of the wellbore after several hours ofcirculation. This temperature is lower than the bottomhole static temperature. Therefore, in extremely harsh environments, a component or fluid that would not ordinarily be suitable under bottomhole static conditions may be used with great care in circulating conditions. Similarly, a high-temperature well may be cooled down in an attempt to allow logging tools to function. The BHCT is also important in the design of operations to cement casing because the setting time for cement is temperature-dependent. The BHCT and bottomhole static temperature (BHST) are important parameters when placing large volumes of temperature-sensitive treatment fluids. Alt. form: BHCT. See: Cementing, Circulate, Logging Tool, Treatment Fluid; (2) (n.) Drilling Fluids. The temperature at the bottom of a well while fluid is being circulated, abbreviated BHCT. This is the temperature used for most tests of cement slurry in a liquid state (such as thickening time and fluid loss). In most cases, the BHCT is lower than the bottomhole static temperature (BHST), but in some cases, such as in deep water or in the arctic, the BHCT may be higher than the BHST. Alt. form: BHCT