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.
After a 13 3/8-in. expandable liner collapsed in a Gulf of Mexico ultradeepwater well, an operator considered a whipstock sidetrack, exiting as deep as possible to finish drilling and completion operations. Exiting the 16-in. casing, industry standards would have called for redrilling and casing an entire hole section. Exiting the expandable liner was an alternative option, but would require a unique solution to operate in the larger internal diameter (ID) and maintain the existing hole size. The service provider created a fit-for-purpose solution to install a casing window in the 13.77-in. ID expandable liner. The standard casing exit system accommodates 13 3/8-in. casing through 14-in. casing and requires minimal modifications to anchor the actual concave assembly to support a 12.25-in. pilot window. Additional mill runs would then open the 12.25-in. pilot window to a full bore 13 1/2-in. outside diameter (OD) window. Despite never having performed an installation in this size of expandable liner, the provider had a run history for exits with similar modifications and extra trips to enlarge and elongate windows. Job challenges included thin-wall, channeled cement; limited flow rates because of liner pressure limits; equipment availability; and a short lead time. The 11 1/2-in. OD assembly was quickly modified to enable the anchor engagement in the 13.77-in. ID liner. Within days the mills were dressed to the custom ODs required to enlarge the 12.25-in. pilot window to 13.50-in. On the first run, the whipstock was hydraulically set in the liner. Kickoff was achieved at 19,609-ft to cut a 27.5-ft window and ream a 45-ft rathole in 22 hours. The second bottom hole assembly (BHA) consisted of three mills with 12 1/2-in., 12 3/4-in., and 13-in. ODs. Milling and reaming took 6 hours. The third and final BHA to open the window to a 13 1/2-in. OD consisted of a 13 1/4-in. OD mill and two full-drift mills above. Milling and reaming with this BHA took 29 hours before coming back in with a motor assembly to drill ahead. This installation is the first sidetrack conducted with a whipstock in a 13 3/8-in. expandable. This paper will show that it is possible to safely and reliably install a casing exit system in difficult applications, such as deep expandable liners, that might previously have been considered unfeasible. This approach provides an opportunity for the industry to significantly reduce non-productive time in such scenarios.
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