An operator in Leon County, Texas, fought short runs with limited ROP in the Bossier and Lower Bossier formations. Using conventional rotary assemblies with polycrystalline diamond compact (PDC) or roller cone drill bits resulted in less time on bottom and costly bit trips. For a deep HPHT well in this Upper Jurassic formation, the operator needed a drilling system that would improve ROP and provide durability and reliability for more time on bottom and less bit trips. The system would face a 17,410-psi bottomhole pressure and a 190 degC [375 degF] bottomhole temperature.
Neyrfor supplied a 5-in T2 MK1 turbodrill to power impregnated diamond bits through the hard and sometimes abrasive formation. Two turbine runs were made with Kinetic drill bits and 18-ppg oil-base mud. The first run drilled 3,269 ft in 417 hours at 7.8 ft/h. It was pulled because of a required blowout preventer test, after which the second run drilled the remaining 396 ft to TD. Neither run encountered any problems, and both provided excellent hole condition.
Because of the 3,269 ft drilled in a single run with the Neyrfor turbodrill at 7.8-ft/h, the operator saw 86.1% efficiency and saved approximately 18 days over the offset wells. Furthermore, the 30-rpm rotary table of the Neyrfor turbodrill significantly reduced casing wear as compared with the 65 to 70 rpm associated with conventional rotary assemblies.
