An HPHT well in East Texas with a reservoir BHT of 334°F and approximately 13,900 psi reservoir pressure proved extremely challenging. Managed Pressure Drilling (MPD) was originally selected to avoid a classic “Kick-Loss-Kick” scenario while drilling deep into the Austin Chalk formation. One primary goal of MPD (“ascertaining the downhole pressure environment limits”) was accomplished, but the greatest benefit was achieved by handling several well control incidents that occurred in the HPHT reservoir section.
As HPHT drilling technology matures, the line between flow control and well control begins to blur. Rather than transitioning back and forth, drilling and well control activities tend to become parts of a single process. This process must take into account the effect of variations in the drilling fluid properties, use of the entire active pit system while circulating out kicks, and handling uncertainties in the downhole pressure regime. Knowledge of the pressure and temperature limits and the effects of HPHT on composition of pressure-sealing elements in all surface and downhole tools proved critical. Optimization of alternative casing design for well control while circulating a kick (influx) and using unconventional drilling techniques will also be described.