Drilling of glacier boreholes with a hydrophilic liquid

During the last twenty years over 10000m of ice core have been recovered through the use of antifreeze thermal electric drills (ATED). An environmentally safe ethanol-water solution (EWS) was utilized as a borehole liquid. The ATED method has been widely used on high mountain temperate and polar glaciers. At glacier temperatures (T_i) from -28 to -8℃ the ATED penetration rate is about 420-450m/wk (I. A. ZOTIKOV; CRREL Rep., 79-24,12p., 1979; V. S. ZAGORODNOV; Ice Core Drilling : Proc. 3rd Int. Workshop Ice Drilling Tech., 97,1989). In Antarctica a borehole of 800m depth was drilled in ice at T_i=-53℃ in two month. Drilling of this borehole was continued the next field season. The major cause of ice core fracture under thermal drilling is thermoelastic stresses. The quality of an ice core taken under ATED can be significantly improved applying the forced circulation of EWS at the borehole kerf. Experimental and theoretical studies demonstrate that a modified ATED (m-ATED) reduces power consumption by 20%-40%. The penetration rate of the m-ATED at low temperatures (below -30℃) is estimated to be about 450m/wk. The logistic cost for deep (>1000m) drilling with ATED is estimated to be about 25% of the conventional thermal or mechanical drilling. Laboratory experiments show that ice can be dissolved by EWS. The phenomenon of ice dissolution by EWS can underlie the dissolution drilling technology (DDT). Further development of DDT technology may offer : simple drill structure, low power consumption, low thermal effect on ice core and borehole wall, ability to penetrate dirty ice, and low logistic cost.