Effectiveness of Simulations on Well Control During HPHT Well Drilling

Abstract The conventional methods of oil and gas wells drilling has been to keep drilling mud in the active mud pit at ambient temperature and pressure to drill oil and gas wells; despite the effect of temperature and pressure on mud properties at bottom hole condition. Although, this practice has proved to be adequate in shallow and conventional wells owing to relatively small difference in temperature between surface and bottom hole and the existence of sufficient margin between pore and fracture pressures. Conversely, lots of changes occur on mud properties especially in drilling High Pressure High Temperature (HPHT) wells leading to increased incidences and serious well control situations. One of the key characteristics of HPHT wells is the existence of small margin between pore pressure and fracture pressure as well as elevated bottom hole temperature. This property of the well (HPHT) presents series of challenges to both drilling fluid management at bottom hole condition and well control incidents. Literature survey puts well control incident rate for conventional wells at 4 to 5% whereas in non-conventional wells such as the HPHT wells, an alarming rate of 100 to 200% or even greater has been recorded. This represents at least one well control incident in every 20 to 25 wells drilled for conventional wells and at least one to two well control incidents for every non-conventional well like HPHT. In this study, tier I HPHT well was examined to ascertain the severity of kick intensity and kick volume on well control using Drill Bench. Simulations were performed on 6.5bbls and 1bbls kick taken in 12¼” hole prior to reaching the next casing seat at 13780ft-ss TVD. The research presents results of delay in shut-in the well, kick volume and volume development during well control as well as gas migration. In addition, the study examined implication of well control methods and drilling fluid type on bottom hole pressures and timing to handle well control incident during HPHT well drilling.