First Deepwater MPD Operation in the Gulf of Mexico: Challenges and Lessons Learned

摘要

In the Gulf of Mexico, the Paleogene play presents challenges in narrow drilling margins. To overcome the challenges, a fully integrated Managed Pressure Drilling (MPD) packaged system was incorporated into a deepwater drill ship. The MPD system was designed to drill a deepwater, high pressure / high temperature well in the Gulf of Mexico. This paper will explain the lessons learned, the challenges and improvements carried out through the use of the MPD system in three key areas: advanced wellbore pressure modeling, downhole characteristics fingerprinting using downhole data and the MPD equipment. A full MPD system was designed to comply with all new government regulations and its performance proven through successful cased hole and open hole testing. Upon government approval, the new system was used to drill the well in full MPD conditions, where the mud weight (MW) was brought below pore pressure and the well was balanced with applied surface back pressure. Throughout the well, there were numerous lessons learned in three key areas: wellbore hydraulics modeling, downhole characteristics provided by PWD data, & the MPD equipment. An advanced wellbore pressure model was needed to accurately maintain the appropriate downhole pressure through the application of surface backpressure. The system used this model to perform simulations and applied the results of those simulations to control the surface equipment. Downhole Pressure While Drilling (PWD) data provided verification of the modeling results and applied surface back pressure as the well was drilled. Challenges faced during the operation included pressure compensation due to swab and surge as a result of pipe movement, and fluid inertia coupled with compressibility of the mud. The downhole characteristics of the well were tracked through PWD data, which was important in compensating the backpressure during connections and drilling. Further, the downhole data were consistently used to fine-tune and adjust the applied back pressure to ensure the well did not go underbalanced during these operations. Continuous improvement during operations also led to increased reliability of the MPD equipment.