Directionally drilling the 8-V" hole section in specific areas of Saudi Arabia is particularly challenging due to a complex stratigraphic section that consists of soft, dense limestone and anhydrite with tough bands of hard stringers. Historically, roller cone bits with tungsten carbide inserts (TCI) have dominated the 8-1/2" application due to proficient steerability and ability to consistently achieve the required build rates in the soft limestone. However, multiple runs are required to finish the entire section. Conversely, Polycrystalline Diamond Compact (PDC) technology increased ROP but lacked consistency due to fluctuations in reactive torque that resulted in poor tool face control and inconsistent build-up rates relative to roller cone bits.

Saudi Aramco determined to efficiently drill the section in one run and meet performance and directional requirements would require new PDC technology. To address this challenge, Saudi Aramco and a service company organized an integrated cross-functional team composed of engineers from both companies to aggressively seek new steerable PDC technology to drill the curved section with controllable torque response and consistent directional behavior while achieving the full penetration rate advantages of PDC bits.

The team analyzed the drilling operation from virtually every perspective using numerical models, laboratory drilling tests, and field testing. The key to the PDC solution was the team process that identified the relevant drilling problems and performance requirements in order to develop the needed technology.

The team identified that poor tool face control in the soft limestone and cutter damage due to vibration problems were the primary obstacles in achieving performance goals. The solution was a PDC design with a new steerable concept that provided exceptional tool face control without sacrificing ROP in addition to improved stability and new cutter technology for prolonged bit life.

After 15 bit runs, the team reduced drilling cost by $17.55 per foot for a total savings of $857,476 over 48,871 ft and 1880.5 drilling hours. The average ROP for the section increased from 22.47 ft/hr with standard PDC bits to 26 ft/hr with the new PDC technology. The current ROP record stands at 42.02 ft/hr with the single run record footage standing at 6,229 ft.

You can access this article if you purchase or spend a download.