Drill with fewer trips in formation of varied stratigraphy

Operator Mangyshlak Munai is developing the Pridorozhnoye gas field in southern Kazakhstan. On the first well drilled, Well 16, an 8 1/2-in section was drilled in 62 days using 36 bits without conical diamond elements. Drilling performance was affected by hard carbonates with chert inclusions in the Lower Carboniferous period (high compressive strengths), as well as soft and sticky Devonian-aged shales, interbedded with sandstone and gravel in the Paleozoic basement. The cutting structures on conventional PDC and insert roller cone bits used in Well 16 were severely damaged, resulting in poor ROP and multiple trips to change the bit.

Increase ROP and reduce tripping time for bit changes

In this highly varied formation, an engineering team from Smith Bits, a Schlumberger company, employed the DBOS drillbit optimization system to support the recommendation to use a StingBlade bit with Stinger conical diamond elements across the bit face, combined with a high-torque PDM with a 7:8 lobe ratio. The Stinger elements’ 3D conical shape is designed to fail high-compressive-strength formations with a concentrated point load while maximizing strength and durability with a thicker diamond layer. This enables StingBlade bits to drill farther through formations that typically cause impact damage to PDC bits, while also sustaining higher ROPs throughout the run. StingBlade bits also consistently drill with less shock and vibration, prolonging the operating life of the bit and other BHA components, reducing PDM stalling, and delivering minimum well deviation.

Field ROP record set with successful drilling to TD

Two subsequent wells drilled with StingBlade bits set ROP field records and eliminated as many as 16 costly bit trips. Compared to Well 16, which was drilled without StingBlade bits, Well 15 required 16 fewer bits to drill the 8 1/2-in section. Well 15 required nine StingBlade bit runs with an average ROP of 2.5 m/h, which represented a 45% improvement in penetration and a 53% improvement in meterage versus Well 16, saving Mangyshlak Munai 23 rig days.

The second offset well, Well 17, required 14 Smith bit runs, 10 of which used StingBlade bits, with even better results: the ROP increased 55% and saved the operator 27 rig days over Well 16. The average meterage recorded for Well 17 was 160% higher than in Well 16 and 70% higher than in Well 15. These measures saved the operator an estimated USD 486,000 in rig time and bit costs while shortening time to production and allowing for more wells to be drilled in a given period.