The design of an invert emulsion fluid that can hold up more than 24,000 psi and 435°F is a complicated and exhausting process. The challenges presented in the design of an UHPHT drilling fluid formulation are the base oil selection and the complete drilling fluid formulation. Flash point measurement of base oil before and after heat ageing to ensure that the base fluid were stable and the overall stability of the mud system need to be assured (rheology, gelation, fluid loss and weight material suspension) after both dynamic and static ageing for at least 96 hours at anticipated maximum BHST.
Laboratory pilot testing allows us to find a chemical balance where the rheology profile and mud properties fulfill the UHPHT project requirements. The laboratory testing protocol validation is the most important factor to prevent different issues during the drilling phase. This testing will be a contributor factor to conclude a well successfully.
Another phase of the design that we need to consider is an exact dynamic temperature modelling because a more precise Bottom Hole Temperature profile helps optimize the drilling process to increase the possibility of borehole stability.