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Managed pressure drilling (MPD) helps operators efficiently navigate through narrow pore pressure-fracture pressure windows. The challenges encountered during one onshore drilling campaign included pore pressure uncertainty, high pressure influxes, total losses and high incidences of differential sticking, which at times led to abandoning wells when drilled conventionally. The case study highlights how these challenges were counteracted with the implementation of a fully automated MPD system. MPD is a safer and more effective drilling technique, as compared to conventional drilling, especially in wells with narrow drilling windows and downhole hazards. A fully automated, early kick detection and control system that enables nearly instantaneous, precise adjustments to the bottomhole pressure adds great value to the client's operations. It has been observed that in wells with a narrow window, precise determination of downhole pressure margins (i.e. pore pressure, wellbore stability and fracture pressure) and precise control of bottomhole pressure are imperative to complete the well without well-control incidents. A fully automated MPD system helps to achieve these goals. Prior to the start of drilling with MPD, the exact formation pressure is determined by conducting pore pressure tests, and then during drilling the target bottomhole pressure can be precisely adjusted almost instantly by adjusting the surface pressure at the MPD choke. The MPD system greatly reduces the time to stabilize well conditions when encountering well control problems or downhole losses. This paper summarizes the implementation of the fully automated MPD system as a sophisticated tool to precisely control such situations instantly, saving time, associated mud costs and hence optimize the overall drilling process. This paper describes a few MPD milestones in drilling the 8 3/8-in. and 12-in. hole sections in the field despite of difficulties including total losses and high-pressure influxes leading to well control events. The primary objective of MPD application in this field was to drill to the liner landing point by adjusting the bottomhole pressure (BHP) in real-time to eliminate the problems caused by uncertainty in the over pressured target formation and minimizing or eliminating the downhole fluid losses in the lower formations. The paper describes results from two case studies. In the first case, the well was drilled with a 1 pound per cubic foot (pcf) (0.13 ppg) narrow window, with accurate detection and control of influxes while mitigating losses. In the second case, initially the bottomhole mud-losses were minimized instantly and later the well was precisely displaced under partial losses to a lighter mud to save mud costs while maintaining well control. |
