Performance Analysis of Digital Underreamers in Motorized Bottom Hole Assembly

Abstract Expandable reamers were developed to enhance operational efficiencies and minimize risks during the drilling process in challenging formations found in deep-water and offshore wells. These tools are particularly valuable in addressing the significant challenge of ensuring wellbore stability in such environments. The initial concentric expandable reamers were activated by a ball mechanism, and once expanded, they remained open until circulation was halted. In the subsequent version, modifications were made to enable deactivation, allowing circulation even after reaming for improved hole cleaning. The concentric expandable reamer offered several advantages over its mechanical-arm predecessors. These included the ability to achieve a larger borehole size to accommodate larger bottomhole assembly (BHA) components, flexibility in choosing pilot bits, higher flow rates, and the capability to ream a previously drilled hole or back ream a hole after drilling. The digitally controlled, expandable under reamer, activated as needed, is seamlessly incorporated into BHA and can be remotely monitored and managed from the surface. Real-time feedback from the reamer includes data on tool vibration and stick slip (VSS), along with confirmation of blade activation status and precise blade position (fully retracted, fully extended, or in transit between the two positions). The extended blade position is pre-set to a specific surface position, and upon activation, the reamer opens to this position to initiate reaming operations. This real-time feedback minimizes operational uncertainties during reaming, streamlining the shoulder test process and saving time. With unlimited activation cycles, the reamer offers the capability for selective reaming. The flexible arrangement of multiple reamers within the BHA allows for both near-bit and main reaming applications. Intense study of Bit and Cutter on reamers is needed to deliver wells flawlessly. Also, the motor on top of reamer provides sufficient RPM to obtain drilling performance. The paper discusses in detail the concept of Installing the underreamer below the mud motor and showcases how it worked successfully in four recent wells, saving a trip for the operator in each well. The paper will also compare multiple Bottom Hole assemblies where the concept of Motorized Underreamer was used with wide range of well profiles including vertical to highly deviated wells. Every well had its own challenges and Intense pre job planning was done to successfully complete the wells. The target depths of well ranged from 2500m to 5500m. Body text 2 paragraphs.