Underreamer Above the MWD in Conductor Jetting BHA: A Solution to Deliver Enlarged Surface Hole Below Conductor and Save a Trip in Deepwater Operations, Egypt East Mediterranean

Abstract An operator successfully delivered a complex deepwater exploration well from a drillship in Egypt's East Mediterranean. Due to challenging geological conditions, an intermediate casing had to be set at 2,025 m true vertical depth (TVD), positioned between the 36-inch conductor jetted to 1,472.5 m TVD (79 m below the mud line) and the next casing setting depth at 2,742 m TVD. To achieve the objective of delivering the final hole section in an 8½-in. bit size while accommodating six casing strings below the 36-in. conductor, it was necessary to enlarge the borehole to 32-in. below the conductor to allow placement of a 28-in. casing. Conventionally, this operation requires two trips: first, jetting the 36-in. conductor using a 28-in. bottom hole assembly (BHA) and drilling a 60-meter rathole below the conductor shoe; second, running a separate BHA equipped with an underreamer to enlarge the hole while drilling to the section's total depth (TD). Alternatively, the entire section can be drilled using the 28-in. jetting BHA, followed by a separate run with an underreamer or hole opener to enlarge the hole to 32-in. In both cases, two trips are required. In this project, an optimized approach was implemented: jetting the conductor and underreaming while drilling the surface hole below it in a single trip. While this technique introduces additional complexity and operational risks, it was executed safely and effectively through meticulous planning. The underreamer was placed above the measurements-while-drilling (MWD) tool in the conductor jetting BHA. This configuration enabled successful jetting of the conductor and simultaneous drilling and underreaming of the 28 × 32-in. hole to the planned depth, eliminating the need for a second trip – an important cost-saving measure in deepwater operations. The 28-in. casing was successfully run and cemented at the planned depth. This technique has now been accepted for future deepwater projects in Egypt. Its successful implementation demonstrates both operational efficiency and technical viability. The knowledge and lessons learned from this project can be applied to other deepwater wells worldwide with similar casing design requirements.