In 2017, Torque Africa embarked on a groundbreaking project that would set the record for the deepest Pan-African percussion drilling at the time. The ambitious endeavor began with an initial borehole diameter of 558mm, which tapered down to 127mm by the project’s completion. Despite widespread skepticism from industry experts who doubted the feasibility of achieving such depths, the project was successfully completed in just three months.
The group’s director, confidently accepted the challenge, defying critics and demonstrating the unparalleled expertise of our team. His leadership and the team’s unwavering determination not only silenced the doubters but also solidified our reputation in the industry. Reflecting on this achievement, Nardus proudly proclaimed,
NARDUS BEZUIDENHOUT – Group director
Given the uncharted geology of the area, we initially used standard bits, switching to diamond impregnated bits when formations became too hard or abrasive,” Bezuidenhout explained. “After about 300 meters of dolomite and shale, we encountered predominantly hard quartzite interspersed with khaki shale, black slate shale, mixed dolomite, quartzite, and diabase. The diamond impregnated bits significantly eased the tough drilling conditions.”
Mr. Bezuidenhout emphasized that the forces encountered at such depths necessitated the highest quality bits. Despite the higher cost, the diamond impregnated bits lasted beyond 378 meters per bit, far surpassing the 70 meters achievable with standard bits, which would have required frequent and time-consuming pullouts.
“Bit changes at these depths are complex and can take up to 24 hours to retrieve the 6-meter rods for tooling replacement. A shanked bit would be catastrophic, potentially necessitating the drilling of a new hole if retrieval was impossible,” he noted.The team also faced challenges such as dolomite wetlands, dykes, voids, and water ingress at various levels. The hole was drilled telescopically, starting at 558.9 mm in diameter and reducing through various layers, including a 310-meter deep grouted section. Upon reaching 300 meters and intersecting quartzite, the diameter was down to 172 mm.The drilling continued until intersecting a stope at 1148 meters, slightly short of the predicted 1200 meters. At this depth, the bit size was 124 mm, ready to accommodate pumped products from the treatment of millions of liters of acid-mine drainage.
Bezuidenhout concluded by highlighting the critical role of high-quality equipment in deep hole drilling operations. “There is limited room for error. Drilling contractors can incur significant losses if tooling wears out quickly or breaks catastrophically deep underground. This is why we insist on quality tooling from Sandvik,” he asserted.
This achievement underscores Torque Africa’s capability to push the boundaries of drilling technology, setting new standards in the industry.