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Appendix A CRREL ACTIVITY IN DEEP DRILLING Based on statement by Donald Garfield given to the Polar Research Board's ad hoc Panel on Polar Ice Coring HISTORICAL SUMMARY CRREL's involvement in deep ice core drilling began in the 1950s when SIPRE, one of CRREL's parent organizations, initiated efforts to obtain deep ice cores for scientific analyses. The first projects were undertaken using modified conventional mobile oil drilling rigs. Four cored holes were completed using this method. The first two were at Site 2, Greenland during 1956 and 1957, when cores were obtained to depths of 305 m and 411 m, respectively. A second similarly modified rig was shipped to Antarctica in 1956 for use on the IGY program. Two sets of cores were obtainedâthe first at Byrd Station to a depth of 308 m in 1957-58, and the second at Little America V to a depth of 257 m in 1958-59. Drilling at Little America V was the first major ice coring operating to be conducted in a fluid-filled hole. Because of the extensive trip time involved in making and breaking drill pipe joints to recover each core, conventional oil field coring techniques were abandoned in favor of cable-suspended thermal coring methods. The thermal concept evolved over several years and ultimately resulted in coring to a depth of 535 m in 1964 at Camp Century, Greenland. Thermal coring proved to be quite slow, especially in fluid-filled holes, so this concept was abandoned in favor of electromechanical coring methods. The first electromechanical ice coring drill (Electrodrill ) was a modified non conventional oil well tool, which was cable-suspended, with a submersible electrical motor and drive system. Ethylene glycol was used to dissolve the ice cuttings. It was the first drill to successfully penetrate a major ice sheet, reaching a depth of 1390 m 47
48 at Camp Century, Greenland, in July 1966. To assist in the further development of this drill, a drill test facility was constructed at CRREL. This facility is a 200-foot deep, three-foot diameter water-filled hole capable of being frozen from top to bottom with ice temperatures down to -20° C. The modified Electrodrill was shipped to Antarctica in 1966 to be used in coring a hole at Byrd Station. This hole was successfully completed to a depth of 2164 m in January 1968. Unfortunately, the drill was lost during the following 1968-69 season while attempting to clear the bottom portion of the hole to subsequently recover cores of sub-ice material. The drill became stuck in a heavy slush caused by water at the bottom of the ice sheet. For the next several years, CRREL concentrated on developing electromechanical coring drills for obtaining shallow (100 m) and intermediate (500 m) depth ice cores. In 1978, CRREL initiated an effort to fabricate a drill similar to the original Electrodrill system for use on the GISP deep drilling program. This effort was terminated after a few months because there was some doubt that the GISP schedule could be met due to long delivery times for some major drill components. There was also considerable reluctance to continue when price quotations on some major components substantially exceeded original estimates. A decision was made to sponsor the Danish drill development effort, which was already in progress, with CRREL providing advice and assistance. Assistance was provided in writing major component specifications, testing the drill in the drill test facility, drilling and casing the upper portion of the DYE 3 hole, and monitoring progress during drilling. CRREL's involvement in deep ice core drilling ended in 1981 when the Danes successfully completed coring to a depth of 2037 m at DYE 3, Greenland. FUTURE DEVELOPMENT CHALLENGES Several new design criteria must be met in order to accommodate future deep ice coring needs. Future drills should be capable of drilling almost twice the depth The Electrodrill was invented by Mr. Armi Arutunoff, Reda Pump Co., Barlesville, Oklahoma.
49 of previous deep holes. New drill systems must be able to operate over a wide temperature spanâin ice as cold as -60° C. The new systems should also be able to core frozen sub-ice materials. Just these three requirements greatly restrict available design options, and indeed, perhaps one single drill system cannot satisfy all requirements. Hydrostatic pressure Non freezing and relatively inexpensive hole fluids must be used to maintain hydrostatic equilibrium in the hole to prevent closure. The greater hydrostatic pressures associated with deeper holes make attainment of leak-free dynamic seals much more difficult than on previous drills. Electromechanical components, such as motors and gear trains, can be operated in a fluid and pressure compensated with their external environment, but many standard electronic components operate reliably only in air at normal atmospheric pressures and temperatures. Ice cutting disposal Methods for collecting and disposing of ice cuttings depend upon the type of hole fluid selected and the temperature profile in the drill hole. Three obvious options are to (1) separate the cuttings from the hole fluid and remove them from the hole, (2) dissolve the cuttings and remove the solution from the hole, or (3) dissolve the cuttings and leave the solution in the hole. Drilling torque reaction Torsional restraint of the drill continues to be a problem, and may be critical when drilling through warm ice into sub-ice material. The Electrodrill relied heavily upon the torsional rigidity of the suspension cable for its reaction. The Danish drill also had some reported problems with torque restraint, even though this drill produced relatively low torque and was equipped with specially designed anti-torque springs. Cutter design Current cutter designs may have to be modified for coring in extremely cold ice. Certainly new cutters will be required for coring in sub-ice materials. Methods for retaining sub-ice samples will have to accommodate the following three possibilities: (1) frozen consolidated material, (2) unfrozen consolidated material, and (3) unfrozen unconsolidated material. These are a few of the technical challenges facing the designer. Solutions to various problems are likely to involve trade-offs, so the final product may not completely meet all requirements.
50 ESTIMATED DEVELOPMENT COSTS Based upon development cost estimates obtained during initial stages of CRREL's 1978 drill development project, it has been estimated that approximately $2 million would be required to develop and fabricate a new drill system. ESTIMATED DEVELOPMENT TIME CRREL has recently conducted some research into the drilling problems cited above, but a substantial amount of additional work is required. We estimate that 36 months total would be required to design, fabricate, and lab test a complete drill system that could be fielded with confidence. RECOMMENDATIONS Based upon past experience, four recommendations should contribute to a successful development program: (1) Separate the drill development schedule from the science plan until tests indicate that the drill will be fully operational. (2) Conduct laboratory tests whenever possible to reduce expensive field testing. (3) Construct an insulated, refrigerated building over the CRREL deep ice well to permit year-round testing. (4) Involve key field operational personnel during the latter stages of drill development. (5) CCREL experience and facilities should be considered as a resource to assist in implementing a new U.S. initiative in deep ice drilling.
Appendix B ICE CORE DRILLING Prepared by Karl C. Kuivinen and Bruce R. Koci Polar Ice Coring Office University of Nebraska-Lincoln Donald E. Garfield Cold Regions Research and Engineering Laboratory INTRODUCTION The purpose of this report is to assess existing capabilities in ice core drilling from a national and international perspective, and to provide a realistic assessment of the technological problems and available resources that may be involved in future (5-year) shallow, intermediate, and deep drilling operations. Advancements in ice core drilling technology and results of operational experience with various drill systems are published in reports of the 1974 Symposium on Ice-Core Drilling (Splettstoesser, 1976) and the 1982 Second International Workshop/Symposium on Ice Drilling Technology (Holdsworth and others, 1984). DRILL TECHNOLOGY The primary application of ice drilling technology has always been the acquisition of cores for glaciological, hydrological, and climatological research. Secondary applications have been the provision of access holes through glaciers or ice shelves and the acquisition of lake and sea ice cores. The wide variety of drilling equipment and techniques used to meet these applications can be classified based on four functions: the means of penetration (thermal or mechanical), the removal of the cuttings or meltwater formed during penetration, control of hole closure or opening due to plastic flow of the ice, and coring or non-coring applications (Hansen, 1984; 51
