Rapid Access Ice Drill (RAID) for Sampling Antarctic Bedrock
D. L. Nielson and C. Delahunty, DOSECC Exploration Services, LLC; J. W. Goodge, University of Minnesota-Duluth and J. P. Severinghaus, University of California, San Diego
Paper prepared for presentation at the ArcticTechnology Conference held in St. John’s, Newfoundland and Labrador, 24-26 October 2016.
The Rapid Access Ice Drill (RAID) was designed and built to rapidly drill through the Antarctic ice cap, and then core the ice-rock transition zone and underlying bedrock. The system is designed to be mobile and to operate autonomously near the South Pole at elevations of 3000 to 4000 m and at air temperatures as low as -40C. The anticipated drilling environment consists of about 100 m of firn that must be cased, followed by 2500 to 3300 m of glacial ice before reaching bedrock. The ice temperature at the surface is about -55C warming to near 0C at the base of the ice (warm ice). Previous work has focused on ice drilling and coring, and individual holes have required more than one drilling season. Our objective is to drill and complete a hole in approximately two weeks.
Firn will be drilled using a conventional auger system at 177.8 mm diameter until impermeable ice is encountered. Casing of 114.3 mm outer diameter will be placed in the hole and sealed against the ice with an inflatable packer. The next stage of drilling utilizes a 88.9 mm bit and 69.9 mm flush joint NRQ V-wall core rod to drill the ice section with penetration rates of 3 m/minute. The bottom hole assembly includes an outer bit and wireline-retrievable inner bit. After experimenting with a number of designs, we chose an outer bit with steel cutters to optimize penetration through the ice. In order to collect core in the transition zone or bedrock, the inner bit is removed by wireline and replaced with a coring assembly that utilizes an impregnated diamond bit.
The drilling system consists of five modules that will be mounted on skis for traversing the ice. These are a Drilling Rig Module, Rod Handling Module, Fluid Recirculation System (FRS) Module, a Power Module and a Shop/Inventory Module. The rig is a Boart Longyear LF-230 that we have modified to operate with an electric prime mover. The drilling fluid is ESTISOL-140 that is recycled through the FRS. The drilling system is powered by a 500 kW diesel generator. Two of these units are mounted in a power module to provide redundancy.