This paper describes the strategies and practices used to deliver best in class ROP performance in three different applications (through salt, soft clastic and medium-hard clastic formations) on the Deepwater Gulf of Mexico. A novel advanced bit design was tested with mechanical (WOB and RPM) and hydraulic (flow rate) parameters beyond the current operational envelope. Several operational and equipment limits were also tested and moved beyond the previous levels. The drilling parameters and results from the three applications are also included.
Over the last couple of years, the drilling cost for deep-water drilling has been reduced through continuous performance improvement resulting in a "Beyond the Best" mentality. Every time a new best in class ROP performance is achieved, questions about "What else can be done", are asked. A project was taken up to challenge the current drilling operational envelope resulting in ROPs faster than ever in the Deepwater Gulf of Mexico. Integrated well planning combining operator and service provider knowhow and modeling capability were used to identify current operational limits and the required changes to go beyond them. BHA configuration and downhole tools were design and adjusted accordingly. Rig equipment were also reviewed and modified. The novel advanced bit design, with 3D cutting elements combining the shearing action of conventional PDC cutters with the crushing action of tungsten carbide insert, was selected by the project due to its capability of delivering less torque when higher mechanical parameters (WOB and RPM) are used.
Field data demonstrates that using WOB up to 70,000 lbs while drilling with a 14-3/4" bit through medium-hard rock resulted in 9 % increase in ROP (103.2 ft/hr), when compared with the previous fastest ROP achieved while drilling similar formations in the field. Also, using 220 rpm while drilling trough salt with a 16-1/2" bit delivered 12% increase in ROP (307.3 ft/hr), when compared with the previous best performance. Furthermore, using 220 rpm in combination with 1460 gpm flow rate (22% above the normal flow rate), while drilling with a similar 16-1/2" bit through interbedded soft rock formations delivered 91% increase in ROP (368.7 ft/hr), when compared with the previous fastest ROP achieved while drilling similar formations in the field. The cuttings load limit in the annulus was tested beyond its current limit (3%) without observing hole pack off or stuck pipe issues. No vibration was observed while operating at the surface torque limit. A cost saving of over $2M was realized from this performance improvement effort.
The identified opportunities for improvement and lessons learned included in the paper have led to best practices for future wells resulting in a valuable benchmark benefiting practicing engineer involved in similar projects. Furthermore, operational parameters used in the project confirm the robustness and benefits of the novel advanced bit design used in the project delivering higher ROP with a smooth torque response.
