On April 16, 2019, the Changning H19 well of Southwest Oilfield adopted a new drilling configuration consisting of an impact-resistant single-face gear bit + vertical drilling system + constant-wall, low-speed, high-torque screw motor. The operation drilled to 1,372 m, achieving a single-trip footage of 1,070 m in the 12-1/4″ section, with a mechanical drilling speed of 6.69 m/h, setting a new record for single-bit footage under large-diameter drilling-fluid conditions in the second block.

The geological design predicted that the lithology of the 12-1/4″ second-open section would be dominated by conglomerate and sandstone, located at the top of the Hanjiadian Formation. To address these formations, the well deployed the new high-impact multi-edge bit ST519ZX, featuring a double-row tooth structure, with wear-resistant teeth serving as the primary cutting elements.

Through a compound rock-breaking mechanism, the bit significantly improved rock-breaking efficiency while delivering twice the impact resistance of conventional PDC cutters. Conical teeth were arranged on the outer shoulder of the blades to reduce bit whirling damage. In addition, the cobalt-removal depth of the cutting teeth was optimized to enhance wear resistance.

At the same time, improvements to the anti-rotation design enhanced bit stability and further boosted rock-breaking performance, ensuring efficient and reliable drilling throughout the section.