Teamwork and industry experience were behind the success of FORACO’s recent 3,011.5 metre hole – SE0019 – drilled for KCGM at the Super Pit in Kalgoorlie, Western Australia.
The challenging diamond drill hole, completed on 3 September 2015, is the deepest mineral exploration hole within Australia, eclipsing the previous record of 3,009m drilled at Mt Isa in the early 2000’s. SE0019 contained over 4,592 metres of drill rods with a value exceeding $380,000.
At a record depth of 3,011.5 metres, the NRQ™ V Wall rods alone equated to 20.8 tonnes of rotating steel – a tough ask for any drill. Fortunately the UDR 1200HC (Sandvik DE 880) was capable of the task and delivered a flawless performance to total depth.
Commenting on the success of SE0019, Senior Vice President for FORACO Asia Pacific, Peter Jacobs, said FORACO worked closely with KCGM and drilling fluids provider AMC to achieve targeted objectives, optimal drilling performance and greater operational efficiencies:
“The project really highlighted the teamwork required to successfully plan and execute such a hole that had little margin for error. KCGM planned the hole – taking into consideration the equipment in use; AMC designed and monitored the mud program to ensure hole stability; and our highly skilled drill crew delivered the technical parameters without incident.”
In 2014, FORACO drilled SE0018 for KCGM to a depth of 2,358 metres. This hole, located to the south of SE0019, provided valuable insight regarding ground conditions and their impact on dip, azimuth deviation and technical planning requirements.
Based on knowledge gained from SE0018, the KCGM team planned and positioned SE0019 to eliminate the cost of utilising down hole motors. The hole, located on a waste dump, was collared at 60 degrees and was to be flattened to 30 degrees. The objective was to obtain the broadest possible cross-section through the formation to the south of the Super Pit.
After setting up on the RC hole and running PQ™ drill pipe, the crew cut out of the pre-collar at the base of the waste dump, as it had deviated when transitioning to the underlying bedrock. Cutting a new hole with the PQ™ at 140 metres helped redirect the hole as the RC collar had steepened at depth.
PQ™ coring continued to a casing depth of 370 metres – the hole was then advanced to 1,210 metres with HRQ™ drill pipe. Directional control of the hole was maintained via a selection of core barrels, bit profiles and matrix, together with reamer shell placement. Boart Longyear™ NRQ™ V Wall rods were used from the HRQ™ casing point to total depth.
Mr Jacobs said he had used the NRQ™ V Wall rods in Canada during the 1990s to depths of 3,000 metres and was confident in their rated capacity for the project.
“The V Wall product is 12% lighter than standard NRQ™. With the hole planned to flatten towards the west at depth, we weren’t concerned with the winching capacity of the rig as it is rated at 3,176 metres and the hole would carry a portion of the rod weight.”
With an intentionally deviated drill hole such as SE0019, we were more concerned with the ability of the rig to rotate the drill string efficiently at depth”, added Mr Jacobs.
An AMC Solids Control Unit (SRU) was used for the entire program. The closed loop system only requires 3,000 litres of surface tank storage, representing a significant reduction in the down hole circulating volume of 13,250 litres at total depth. Additionally, the SRU allowed drilling muds to be closely monitored and quickly adjusted, and delivered substantial savings in drilling fluid costs.
