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Case Study: LUKOIL Saves 5 Drilling Days in Challenging Sand Formation Using Enhanced Drilling Technologies

ONYX 360 cutters and Stinger element help eliminate 4 bit trips and increase ROP by 40% in hard, abrasive sections of the Kyrtaelskoye field, Russia

Challenge: Reduce drilling time for the production section by increasing ROP and bit durability in a hard, highly abrasive sand formation.

Solution: Use two Schlumberger drillbit technologies— ONYX 360 rolling PDC cutters and the Stinger conical diamond element—along with a PowerPak steerable motor.

Result:

  • Drilled the 8 5/8-in section in 15 days, saving 5 days versus AFE.
  • Achieved an average ROP of 9.3 m/h [30.1 ft/h] per section, a 40% increase compared with the maximum ROP achieved in offset wells.
  • Saved four trips compared with offset well performance.

Challenging formation demands multiple bits and runs

The Kyrtaelskoye field is situated on the left bank of the Pechora River in northern Russia. The production section of wells drilled in the field typically targets the Devonian system, where the geological profile includes terrigenous and carbonate-terrigenous deposits of the Paleozoic sedimentary cover. Mechanical drilling performance in the lower interval was affected by dense Devonian bituminous limestone and Middle Devonian quartzose sandstone and silt with a total thickness of 500 m [1,640 ft]. These highly abrasive formations lead to reduced service life of all bit types—average footage is 123 m [404 ft] before bit changeout is required, ROP is limited to 0.7 m/h [2.3 ft/h], and most bits suffer catastrophic ringout in the shoulder area.

To optimize drilling performance and reduce well construction time, LUKOIL sought a solution that would maximize ROP in the upper interval of the production section and provide improved bit durability when drilling the lower part of the interval.

Advanced drilling technologies overcome complexities

LUKOIL engineers worked with Schlumberger drillbit and directional drilling engineers to optimize a drilling solution and develop a horizontal directional drilling program. After consulting with the operator about its objectives, Smith Bits and Schlumberger engineers suggested using a PDC bit with a central Stinger conical diamond element at the upper interval to achieve greater ROP and a PDC bit with ONYX 360 rolling PDC cutters in the lower interval for enhanced durability and footage in the abrasive formation. The bits would be run with a PowerPak motor to improve mechanical drilling performance.

Stinger elements were chosen for the application because the elements offer superior impact strength and wear resistance. When positioned at the bit center, Stinger elements continuously crush and fracture the stress-relieved column of rock that accumulates in the middle of the bit, helping to improve borehole quality and reduce vibration while increasing drilling efficiency.

In addition to the central Stinger element bit, LUKOIL used a PDC bit dressed with ONYX 360 rolling PDC cutters. These cutters were recommended because they rotate 360°, enabling the entire diamond edge to be used to drill the formation. This rotation also allows the cutter’s diamond edge to stay sharper longer, extending ONYX 360 cutter life far beyond that of premium fixed cutters and, in turn, reducing bit trips and lowering drilling costs.

Improved efficiency generates rig-time and cost savings

The drilling technologies helped LUKOIL drill the production section at an ROP of 9.3 m/h, a record for the field. Only three bits were required to reach section TD. In contrast, offset wells required six bits and a total of seven runs. ROP increased by 40% compared with offset horizontal wells, and LUKOIL saved 5 days off AFE.


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