Instability of drilling fluid density downhole in the high pressure, high temperature hole section of a HPHT well has been posing many drilling challenges like well control (kick/blowout) or high ECD that could lead to the fracturing of formation especially where the operational window between the pore pressure and fracture gradient is very narrow which is often the case for HPHT wells. Accurate prediction of dominant effect of temperature or pressure on the change in the equivalent static density of drilling mud prior to drilling is important to benchmark with the real time pressure measurement.
This study uses Kutasov empirical model and subsurface data to predict the behavior of equivalent static density (ESD) of the anticipated drilling fluid in Niger Delta.
Furthermore, the equivalent static density of drilling fluids of some HPHT wells are modeled to investigate some drilling issues that were experienced during the drilling of these wells. Finally some HPHT case histories and their specific drilling challenges are discussed as part of this study.