by William Ward, Operations Manager – East Africa at Capital Limited
Capital Limited was initially awarded an exploration drilling contract with Tembo Nickel Corporation Limited (Tembo), a subsidiary of Lifezone Metals Ltd. (NYSE:LZM), at the Kabanga Nickel Project, Tanzania in late 2021. The Project hosts one of the world’s largest and highest-grade nickel sulphide deposits.
Project overview
The Kabanga Nickel Project is situated in the northwest of Tanzania, close to the border with Burundi and within the highlands region of the country. It is approximately 800 km (497 mi) from Mwanza, the closest major center.
The Kabanga Nickel Project boasts significant nickel resources and exploration upside potential, with current estimates suggesting over 87 million tonnes of high-grade nickel sulfide mineralization. Lifezone is progressing the site towards the completion of the Definitive Feasibility Study expected by the end of Q3 2024.
The Project is expected to be a direct-to-metal operation producing high-grade battery-grade nickel, copper and cobalt with local processing facilities. The refining operation will be constructed in the Kahama District, Shinyanga Region, and will use a Lifezone Metal’s Hydromet technology, which is more cost-efficient than smelting and has a significantly lower environmental impact.
The site is located within the ultramafic rocks of the Tembo-Musongati Belt, the mineralization primarily consists of pentlandite, chalcopyrite, and pyrrhotite, with significant cobalt and copper by-products.
BHP has invested USD 100 million in the project which will be used to accelerate its development.
Capital Limited’s exploration drilling activity at Kabanga through 2023 included more than 30 000 m (98 425 ft) of diamond core.
A number of diamond and deep hole diamond drill rigs were used at the project, with maximum N-size depth capacities of up to 1200 m (3937 ft) and B-size of 2200 m (7218 ft).
Remote site challenges
The Kabanga deposit presented both logistical, geological as well as site topography challenges. Additionally, the project faced infrastructure challenges due to the location of the drill sites relative to the Kabanga Camp, with limited access to power, water, and transportation networks at the drill pads.
The closest airport is at Ngara, which is only capable of landing light aircraft. As a result, drilling inventory and consumables needed to be trucked in from Mwanza to ensure mechanical availability above 80% could be maintained.
The drill locations were positioned on steep, sloping hills, with limited established roads in, requiring track-mounted rigs to navigate the terrain. With multiple small targets to hit, traversing between hole locations was arduous.
Changing barrel configurations
To optimize the cost efficiency of directional drilling operations at Kabanga, Capital Limited strategically adjusted barrel configurations during the drill program, including core barrels with varying sizes and types of bits and reamers, utilized to optimize drilling efficiency and accuracy. Barrel configurations were chosen based on the site’s rock type, ground conditions, and desired intersection angles.
Core barrel orientation within the drill string was also adjusted to control borehole trajectory and target specific intersections accurately. This precision targeting minimized the need for the use of costly navigation motors.
Core orientation tools, such as gyroscopic surveys and electronic orientation devices, provided real-time data on core barrel orientation.
Enhancing diamond drill bit performance
In addition to barrel configuration adjustments, Capital Limited took proactive measures to enhance diamond drill bit performance in the hard and abrasive quartz-rich ground conditions.
Capital Limited worked closely with bit designers that traveled to the site to tailor the drill bits to the specific geological conditions encountered at Kabanga. They studied the geological characteristics of the quartz zones encountered and analyzed drilling data to customize their drill bit designs to ensure performance was optimized for the site conditions. These preferences incorporated features, such as specialized diamond configurations, cutter layouts, and compounds tailored to maximize bit life and drilling efficiency.
Managing water loss in fractured ground
In what can be typical of quartz formations, fractured zones during drilling created some water loss issues. To ensure fluid recovery and hole stability, Capital organized regular site visits by their mud engineers to advise on the best lost circulation materials to use in the conditions to maintain hole formation and stability.
Hitting targets with directional drilling
Capital Limited employed directional drilling techniques to ensure it hit the required targets, working closely with Well Force International, its rig site technology and software subsidiary company and the client.
Survey data obtained with Well Force’s North Seeking gyros was uploaded to their proprietary borehole management software, HiTT. In close collaboration with the client, progress to the target was tracked and downhole directional changes were managed through the use of core barrel configuration changes and as required, wedges.
The use of top drive rigs facilitated a safer, easier installation of wedges when required, given the clear configuration of the drill mast when lowering wedges.
By using directional drilling in the challenging terrain, Capital Limited was able to drill up to six targets off the original drill hole. This eliminated the need to prepare and move rigs to new drill sites for each target across the difficult conditions while delivering financial savings.
Tanzanian crews
It is noteworthy that all of the drilling crew operating at Tembo are Tanzanian employees. Their competency in managing the challenging terrain, remote location and at times difficult drilling conditions while delivering on the client’s drill program objectives reflects Capital’s training and development investment in their local teams, as well as the crew’s own dedication and resilience in executing drilling operations efficiently and safely.
Conclusion
Capital Limited’s focus on ensuring it not only delivers drilling programs accurately but also efficiently and cost-effectively, is reflected in the number of approaches taken to achieve the goals of this drilling program. Despite the challenging formation, holes remained stable and retained integrity to depth through the combination of techniques, from adjusting barrel configurations and drilling muds to customizing diamond drill bit preferences. In addition, the crews worked closely with the client’s on-site geological team to further reduce costs, resulting in significant cost-saving outcomes for the project.
The aim of any exploration drill program is to generate information on the ore body. Through its use of directional drilling techniques combined with the state-of-the-art accuracy of Well Force’s downhole gyros and HiTT software, precise drilling trajectories were achieved; every hole was in line and delivered every target intersection to aid in maximizing resource recovery. Additionally, it was achieved with zero redrills across the program.
About Capital Limited
Capital Limited is a leading mining services company providing full-service mining, drilling, maintenance and geochemical analysis solutions to customers within the minerals industry. The Company’s services extend across the mining value chain providing customers with a fully integrated mining services solution including exploration, delineation and production drilling; load and haul services; maintenance; and geochemical analysis. Our reputation is built on an unwavering commitment to safety, delivering professional mining solutions and working closely with our customers to deliver operational efficiencies.
The Group’s corporate headquarters are in the United Kingdom, and it has established operations in Côte d’Ivoire, Canada, the Democratic Republic of Congo, Egypt, Gabon, Ghana, Guinea, Kenya, Mali, Mauritania, Nigeria, Pakistan, Saudi Arabia, Tanzania and the US.
For more information visit: capdrill.com
