Short runs, low ROP seen in offsets

A Kurten field operator used conventional rotary assemblies with polycrystalline diamond compact (PDC) or roller cone bits to drill the Bossier and Lower Bossier formations. These hard and sometimes abrasive Texas formations proved challenging because of short runs and low ROP, both of which the operator sought to improve. The company needed a durable, reliable drilling system that would increase ROP, allow for more time on bottom, and reduce costly bit trips in conditions including a bottomhole pressure of 17,797 psi and a bottomhole static temperature of 144 degF.

Continuous operation, good drillbit condition

Using the 4 3/4-in Neyrfor turbodrill to power impregnated drill bits, the operator made two turbine runs for a well in the Kurten field. For the first run, a competitor drill bit was chosen, and 1,593 ft was drilled in 327 hours at 4.9 ft/h. After pulling out of the hole, the bit was almost completely worn out (dull: 6-6WT-A-X-1-WT-PR).

For the second run, a Smith Bits Kinetic drill bit was chosen, and 1,855 ft was drilled in 444 hours at 4.1 ft/h with 18.5-ppg oil-base mud. The assembly was pulled at TD, and the drill bit proved to be in good condition compared with the previous bit (dull: 1-0-WT-C-X-IN-NO-TD). The run also provided excellent hole condition.

The Neyrfor turbodrill system achieved 85.7% efficiency and saved the operator 17+ bits, along with the associated trips to complete the well (assuming 200 ft/bit). This bit savings is equivalent to 14+ days in trip time alone. Overall, the operator saved 30 days of rig time. Furthermore, because of the 30-rpm rotary table of the Neyrfor turbodrill, casing wear was reduced compared with the 65 to 70 rpm associated with conventional rotary assemblies.