EZCase

The gauge design’s tapered leading edge reduces reactive torque and sidecutting aggressiveness, minimizing unintentional wellbore sidetracking. A secondary bypass port option allows normal circulation or cementing to continue in the event of nozzle plugging. Drillout is accomplished with a roller cone or a custom-built PDC drillout bit.

Operator drills through and isolates rubble zone with nonretrievable rotating liner system run
In deepwater Gulf of Mexico, a nonretrievable liner drilling system with a 10 5/8-in. liner drill bit with six blades and 13-mm cutters drilled in the 9 5/8-in. liner on 6 5/8-in. drillpipe past a problematic rubble zone. The operator spent 10 days trying to control the well without success. Analysis indicated drilling with conventional assemblies was too risky under current conditions. The great challenge at that point was to drill through and isolate part of the subsalt, highly stressed rubble zone that was causing most of the wellbore stability problems. Drilling as deep as possible was imperative as was setting the liner below the current depth of 25,961 ft to reach the well target TD without an additional string of liner.  

The assembly drilled the highly stressed rubble zone without returns from 25,961 ft to 26,584 ft for a total of 623 ft in 26 hr at an average ROP of 24 ft/hr. Average drilling parameters during the run were 255 to 315 GPM, 8 to 25 K-Lbs WOB, 80 to 95 RPM, and maximum observed surface torque of 34,000 ft-lbs. To minimize the chance of borehole packoff, the mud weight was maintained at 15.2 ppg and the drilled hole was backreamed 15 ft at every connection. At TD, the liner hanger was set and the running tool released. Drilling with the liner only stopped at 26,584 ft because of  the lack of liner overlap.

At the time, this was a record for the deepest and longest successful liner drilling run in deepwater Gulf of Mexico.

Isolate problematic zones
A customer working in South Texas faced three depleted intervals under the 6 1/2in. hole section. Using a 6 1/2-in. EZCase bit, the customer set 5 1/2-in. casing through the problematic zones. The EZCase bit drilled from 50 ft to 445 ft, reaching section TD. ROP exceeded other PDC offset data in this field, averaging 27 ft/hr. The casing bit was drilled out successfully in less than 30 min using a MX-1 Tricone™ bit.

Drill through hard formations
An 8 3/4-in. EZCase bit, designed especially for harder drilling conditions, drilled through three formations—OJO Alamo, Kirkland Shale, and the Fruitland coal seam in New Mexico—and set 7 5/8-in. casing, which isolated the trouble zones. The bit drilled from 702 ft to a depth of 3,425 ft at an average ROP of 70 ft/hr, achieving instantaneous ROP at times of 300 ft/hr. After a successful cementing operation at TD, the bit was drilled out with an air hammer bit.

Additional Information
» EZCase flyer (PDF 136 KB)
» IADC/SPE 99110—Reducing Well Cost Utilizing Liner Drilling Operations in South Texas
» SPE 96810—Casing Drilling vs Liner Drilling: Critical Analysis of an Operation in Gulf of Mexico
» SPE /IADC 105395—Casing-Drilling Step Improvement: PDC Successfully Drills Out Casing Bit and Finishes Hole Section at Lowest Cost
» SPE/IADC 105595—PDC Casing Drilling Improves HS&E, Cuts Drilling Costs—West Africa