Advances in Drilling Technology for Managing Drilling Risk Using an In-Situ Hydraulically Actuated Drilling Reamer to Improve Borehole Quality and Reduce Stuck Pipe Occurrence
Authors: Nkwocha C. O. , Silva R. P. 
Published: October 2024

Days of $9/bbl. oil are now in the distant past. Current hydrocarbon reserves are either found in highly depleted reservoirs or require more expensive recovery strategies to extract due to their geographical or geological locations. That notwithstanding, environmental concerns further complicate the process as this must be taken into consideration when venturing further and farther than ever before. Improvements in drilling performance and eliminating or reducing the occurrence of stuck pipe incidents, should result in smaller environmental footprint due to fewer days on well. Several studies on stuck pipe events in the 1990s show that stuck-pipe events occurred in 1 out of every 3 wells drilled, accounting for 3-5% of total drilling cost. In 1991 the cost associated with stuck pipe incidents was estimated as being in excess of $250 million/year (Bradley, et. al, 1991). The actual cost of stuck pipe is significantly higher today due to higher technological tiers of services and much higher rig costs.

The proposed in-situ drilling reamer/stabilizer is powered by an inverse Moineau system with the stator and rotor transposed so the stator rotates whilst the rotor is coupled to the rest of the drill string. The stator housing incorporates a bladed profile referred to as the reamer housing, and this comes with active cutting elements which can be designed to ream concentrically or bicentric, where under-reaming is required. The bicentric configuration enlarges already drilled holes by up to 1 inch in diameter. The reamer is fluid actuated and capable of reaming on its own without surface string rotation. It can be used as an integral part of a rotary, rotary steerable or motor BHAs. Depending on the application, multiple tools can be run on the same string. The expected benefits of such an in-situ reamer include drill string stabilization, lower drag during trips in and out of hole, sliding and rotating motor assemblies, less hole rugosity, micro tortuosity from using short gage PDC bits. smoothened micro-doglegs, better hole cleaning, string agitation, reduced drill string vibration, with the ultimate objective of reducing or preventing stuck pipe events.

A concept of an in-situ fluid powered downhole drilling assurance tool is presented in this paper. The reamer allows a stator (bladed reamer housing) to rotate faster than the drill string thereby providing all the benefits of a mud motor power section such as eliminating or dampening the onset of drill string shocks and vibrations, and due to the different harmonics of the stator, stick-n-slip is better managed. Drilling torque is also reduced since the reamer is able to create torque with fluid circulation, to rotate the reamer housing independently of drill string rotation.

This is a first self-propelled reamer for use in the oil and gas drilling industry and provides a wide range of opportunities for improving drilling performance and reducing associated risks. Theoretically, the system should enhance drilling efficiency in horizontal, ERD and deep drilling operations with challenging geological sequences prone to diverse borehole problems.