Improve drilling efficiency in damaging dolerite sections

The Kahlouche Field in Algeria contains hard dolerite layers above the pay zone, presenting many unique drilling challenges. With unconfined compressive strength (UCS) up to 45,000 psi [310.26 MPa], unpredictable distribution, and varying thickness, the dolerite inclusions were considered “undrillable” using conventional PDC bits. Drilling through this high-impact rock required GRN to pull out of hole and replace several damaged bits before reaching target depth. The consortium sought to minimize the number of trips required in these difficult dolerite sections without compromising penetration rates.

Overcome bit failure with advanced diamond element bit

GRN partnered with Schlumberger to drill the 8 1/2-in section, which had a predicted dolerite layer at 2,077-m [6,814-m] TVD with an estimated thickness of 20 m [65.6 ft]. After conducting a detailed study using the IDEAS platform, Smith Bits, a Schlumberger company, recommended the StingBlade conical diamond element bit, which includes Stinger elements. The Stinger elements have a thicker diamond table to enhance impact resistance and have proved to provide superior impact strength and wear resistance in hard-to-drill formations.

Drilled section in one run and saved USD 306,000

The StingBlade bit mitigated bit damage, becoming the first bit to drill a section with dolerite from shoe to shoe in Kahlouche Field. GRN drilled a total of 477 m [1,565 ft] in one run—including the dolerite intrusion that turned out to be 28 m [92 ft] thick—saving more than USD 306,000.