Novel Downhole Technology with a True Point-the-Bit Rotary Steerable System Delivers Significant Operational Improvement and Cost Savings in a Challenging Reactive Shale Formation: Case Study, Kuwait

摘要

In pursuit of higher oil production targets in North Kuwait, a major campaign was initiated to drill reentry and new horizontal wells targeting a major multilayer carbonate reservoir. A recent study established that horizontal drilling along the northeast/southwest plane is most favorable to cut through two major unstable shale layers. Most well profiles did not satisfy this condition, given the subsurface target and the nearby wells. Contradictory to the study recommendations, multiple directional wells had to cut toward the least stress direction, complicating the tripping capability, spending many hours on back reaming to get the bottomhole assembly (BHA) out of the hole. The requirement for a reliable passive reaming device became necessary for less time-consuming trips. This paper discusses a review of a downhole technology that has helped improve metrics against this time-reduction imperative. Multiple designs comprising additional string stabilizer(s) did not address the issues resulting from placement too far from the BHA or not having reaming capabilities. In collaboration with a specialized downhole tools supplier, the service company designed a wired rigidized heavy-duty inline stabilizer (ILS) and a bidirectional passive cutting structure compatible with the rotary steerable system (RSS) BHA requirements, replacing the existing conventional wired ILS placed within the logging while drilling (LWD) tool string. This helped the reamer device be close to the RSS to provide the necessary BHA stabilization while delivering enhanced wellbore quality through controlled reaming and back-reaming capabilities. Using this engineered stabilizer contributed to helping ensure a gauged hole by removing tortuosity, ledges, microdoglegs, and spiral patterns associated with directional drilling. The proposed reamer device RSS BHA was successfully run on multiple wells where the shale portion became active while pulling out of the hole (POOH). The dedicated bidirectional passive reaming features above the RSS enabled reaming while drilling and back reaming the hole without any difficulties and removed obstructions more easily and efficiently. Reducing tripping time and protecting expensive BHA components from damage were a direct benefit of using these reamers. One well achieved a benchmark rate of penetration (ROP) because of a smoother running speed and weight transmission improvement. With the integration of the reamer device, the reaming process could be implemented without affecting building capability of the point the bit RSS with a build rate of more than 12°/100 ft achievable when necessary.