Hydrophilic Liquid in Glacier Boreholes

Ecological integrity is a primary criteria of any liquid used for filling boreholes in glaciers. Antifreeze solutions based on ethanol and other high molecular weight alcohols are among several potential fluids used for drilling deep holes in the central part of the Antarctic Ice Sheet. At relatively high ice temperatures in boreholes, the concentration of ethanol in the solution is low. Therefore, such drilling fluids have a much lower environmental impact than others. Ethanol-water solutions can be used for filling boreholes with temperatures from 0 to -60 degrees Celsius. Ethanol requirements for deep drilling are significantly less than the volume of the borehole. The penetration of ethanol into the ice core is essentially the same as kerosene. Given the correct technological regimen, ice core dissolution is about 1-mm ply per 40 min. The preparation of an antifreeze thermodrill takes from 5 to 15 min, which includes pumping the drilling solution into the drill while simultaneously extracting the ice core. The lowering or raising speed of the instruments in the boreholes with an ethanol-water solution at -53 degrees Celsius is 0.3 m/s. By increasing the clearance between the drill and the hole wall, the movement speed could be 0.5 m/sec. At -53 degrees Celsius the penetration rate of an antifreeze thermodrill is about 120 m/week. Drills with 6-m length core barrels and large clearance will operate with about a 350 to 450 m/week penetration rate. Use of ethanol-water fluid for thermal drilling involves slush formation. Practice has shown that ice slush formation in boreholes is not a major drilling problem.