Performance Improvement Through Continuous Learning – A Case Study of World's First Unified 30 and 20 Casing While Drilling Project

The objective of this paper is to present the valuable lessons learned in the world's first unified 30" and 20" non-directional Casing While Drilling (CWD) project in ONGC's Bombay High field and how the operational workflow was optimized based on those learnings to further enhance operational efficiency. The focus is on addressing the challenges encountered during the operation and sharing the corresponding solutions. The project involved drilling six wells using CWD technology in the exploratory fields of Bombay High. Specially designed Copper-Bronze Drillable Alloy Bits (DABs) were attached to the bottom of the casing to drill and case the 30" conductor pipe and the 20" surface casing. A casing drive system provided mechanical and hydraulic energy to the assembly and DABs. Based on challenges faced and experiences gained in the six well pilot project, the operational procedures and workflow were constantly optimized to ensure continuous improvement in well delivery timelines. The implementation of CWD technology reduced the average drilling time of the 30" and 20" sections from an average of 12.83 days to 5.95 days, resulting in significant savings of 41 offshore rig days in the six-well pilot project. The use of CWD technology eliminated the need for piling the 30" conductor casing, 17.5" pilot hole drilling, and subsequent hole enlargement to 26" to facilitate lowering of 20" casing. This improvement in the drilling efficiency allowed ONGC to meet their drilling targets, reduce NPT, and improve well delivery rate. The CWD technique also reduced the HSE exposure of the rig crew, as the risks associated with piling, higher man hours, tripping operations and manual handling of large sized casings were eliminated. The paper explains the various optimizations that were done in the process of CWD to overcome unique challenges that helped improve the well delivery timeline from average 6.25 days in the first 3 wells to average 5.65 days in the last 3 wells. This paper provides a comprehensive case study of the world's first unified 30" and 20" CWD project in the Bombay High field. The lessons learned from addressing extremely unique challenges such as high torque, casing sinking, DAB drill-out issue, and CRT stuck issues during the operation are shared in the paper. The insights gained from this study will benefit drilling engineers, well planners, and operators seeking to implement CWD technology more efficiently, reduce NPT, optimize well delivery, and maintain safety standards.