An operator began drilling the 8 1/2-in vertical section of its exploration well in China’s Xinjiang province using a traditional BHA. At 7,025.81 m MD in a high-dip fragmentary layer, inclination had increased to 15.98° and could not be corrected, so the hole was cemented back about 100 m to a depth at which inclination was less than 3°. The operator planned to sidetrack the well at that point and drill vertically to a TD of 7,600 m. The fragmentary layer and a bottomhole static temperature expected to exceed 150 degC made that a challenge.
The sidetrack was kicked off using a high-temperature PowerPak steerable motor. Then a PowerV vertical drilling system, run with SlimPulse MWD service, automatically steered the wellbore back to vertical. When inclination had been reduced to 0.25°, the operator resumed drilling with a traditional BHA, but it proved unable to maintain verticality and was pulled out of the hole. Once again, the PowerV system steered the wellbore back to vertical and drilled it to TD at 7,510 m MD—the deepest a PowerV system had ever been run.
Inclination at TD was just 0.25°. The PowerV system drilled a total of 547 m in the high-temperature, high-dip fragmentary layer and achieved an average ROP of 1.25 m/h—a 25% increase over the 1 m/h averaged with a traditional BHA.
