Simultaneous drilling and hole enlargement is a common practice in deepwater Gulf of Mexico projects where tighter casing tolerances are required. Hole enlargement via underreaming is the most common practice, because it provides a larger diameter hole to ensure that casing reaches its required total depth (TD). Hole enlargement creates sufficient annular space to allow casing to be delivered to planned depth as well as for a properly executed cement job. The most accepted bottom hole assembly (BHA) design for hole enlargement while drilling (HEWD) places an underreamer above both the measurement while drilling / logging while drilling (MWD/LWD) and rotary steerable system (RSS) packages. This placement ensures proper installation of the activation ball in the underreamer and connectivity of the RSS and MWD/LWD so that directional work can be executed. However, this placement also leaves up to 200 feet (61 m) of under gauge rat hole to total depth (TD), forcing the operator in many cases to make a second dedicated run to underream the remaining under gauge rat hole.

An alternative underreamer technology that is gaining interest is designed to run directly above the RSS, but below the MWD/LWD package. Known as the intelligent wired underreamer, this design allows for a much shorter under gauge rathole to TD, while circumventing several common deployment challenges with conventional underreamers. Historically, placing an underreamer below the MWD/LWD prevented the operator from pumping an activation ball through the restricted internal diameter of the MWD/LWD tools. Another challenge of placing the underreamer near the bit is the fact that connectivity is severed between the MWD/LWD and RSS, which makes it impossible to use certain RSS in the BHA.

A deepwater operator drilled a development well in the Gulf of Mexico which required such a solution to simultaneously drill and enlarge the 18 1/8" and 16 ½" sections of the wellbore to 22" and 20", respectively. The intelligent wired underreamer, with its radio frequency identification (RFID) and pump-cycle activation capabilities, allowed the operator to run the underreamer directly above the RSS and below the MWD/LWD package and successfully activate and deactivate the underreamer, without ball drop. A wire through the underreamer connected the MWD/LWD and the RSS, providing full connectivity and directional control. And the use of an intelligent wired reamer in this application eliminated a potential round trip to ream the rathole and allowed the operator to successfully drill and ream both sections to planned TD.

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