The pore and fracture pressure provides the boundaries during drilling operation. Nominal disparities between pore pressure and fracture pressure gradients cause the drilling window to be narrow, hence the term, “narrow margin wells.” Using conventional drilling methods, the drilling of narrow margin wells can be very challenging, hence the industry has begun exploring various methods of drilling through the narrow windows in a safe and effective manner. Managed Pressure Drilling MPD has evolved as a drilling method, which if properly engineered and implemented, could enable drilling through narrow margins in a safe and effective manner with significant reduction in drilling problems.
MPD utilizes the application of Surface Back Pressure (SBP) in order to manipulate the bottomhole pressure (BHP) within the confines of the pore and fracture pressure and enables precise navigation while drilling through the narrow margins. According to Fredericks et al, the effective control provided by MPD allows a more precise and better management of the annular pressure profile, allows accurate management of bottomhole pressure while drilling, during connections and even during well control operations.
The Weatherford MPD system was installed on an offshore Jack-Up rig to fulfill various requirements of the drilling operation. With the proven capability of the MPD system to “walk the line” between the pore and fracture pressure limits, the MPD system provided immense value to the entire drilling operation and enabled the operator to drill to the target depth.
This paper will detail a case study of this MPD operation and also describe significant values provided by the MPD system to the overall drilling objective. The MPD system enabled early kick and loss detection, ability to maintain constant bottomhole pressure during drilling and during pumps - off events and ability to utilize the Annular Pressure Control mode (APC) to automatically displace heavy mud cap at specific depths in order to maintain the static overbalance when the drill string is out of hole. The MPD system was incorporated into the existing rig system with minimal disruptions to rig operations and equipment. Drilling process safety and operational efficiencies were greatly improved with the adoption of MPD.