MPD Helped Successfully Drill a Central European Well to TD After Multiple Failures in a Formation Fraught with Wellbore Instability and Formation Pressure Uncertainties

Abstract MPD successfully delivered the first well in a remote Balkan region of Central Europe after multiple failed conventional drilling attempts into a reservoir fraught with formation pressure uncertainties and significant wellbore breakout. This paper discusses the MPD planning and execution strategies for managing the formation pressure uncertainties and borehole breakout, as well as the performance of the MPD system in handling larger cuttings and cavings. MPD offers many opportunities, such as using a reduced mud weight and tracking the lower pressure boundary, coupled with the ability to respond rapidly to changing formation pressures. Challenges arise when wellbore stability pressure is uncertain, leading to breakouts at the borehole wall. This results in larger cuttings and cavings that can potentially plug the choke, causing pressure fluctuations and potentially leading to charged fractures, thereby further exacerbating the situation. These scenarios require detailed analysis, extensive planning, and rapid response. The engineering team's planned response to the formation and fracture pressure uncertainties, combined with field execution and MPD system performance, enabled Shell Upstream Albania B.V. to successfully drill the well to the planned TD and secure and isolate multiple fracture zones with liner and MPC for stimulation and testing for the first time in the region. The well was drilled and completed with minimal losses while encountering major borehole breakout and with "0″ NPT due to choke plugging. MPD also enabled the client to obtain the first set of logs for the reservoir in this region with LWD. The liner was successfully run to TD, and bottom hole pressures were managed while cementing with MPD.