In recent years, new technology has significantly improved the economics in high-cost drilling environments worldwide. In a western Siberian case, two service providers recently combined their technologies and operating procedures to yield reduced drilling costs and overall improved project economics. The service companies cooperated to produce the best results for the project and the customer.

This paper describes a project in western Siberia, a well-developed, low-cost environment. Drilling performance had to be measurable and repeatable. The major challenge was to design a polycrystalline diamond compact (PDC) drill-bit/mud-motor combination for use on Russian-made rigs to achieve performance improvement. Issues included tool face control, initial cost of PDC drill bits, and in-country rigs incapable of delivering adequate torque and hydraulic horsepower to the PDC bit.

Applied technology included a new PDC bit designed for steerable motors in projects in which tool face control was a primary concern. The PDC bit was optimized for formation characteristics and motor capabilities by use of depth-of-cut control (DOCC) technology. This optimization reduced torque fluctuations that, in turn, increased tool face control while sliding and increased the rate of penetration (ROP) in rotary mode. Maximizing the benefit of the bit, a special motor was used that was capable of delivering high torque to allow consistently high ROP while maintaining trajectory control. This combination resulted in successful high-performance drilling.

The objective was to complete intervals normally requiring several bits with a single bit run at higher average ROP. The results were indeed rewarding. There were 66% fewer trips per 8½-in. section, on average, compared to offset wells, in conjunction with a 37% reduction in drilling hours, equating to an ROP improvement of 27%. In spite of the additional cost of the PDC and high-torque motor, the system delivered the lowest cost per foot vs. the best offsets from three drilling pads examined. An important feature of the application was that the bit/motor combination was run on a risk/reward incentive program.

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