COMPILED REPORTS OF THE
U.S. ICE CORE RESEARCH WORKSHOP

2.2 GISP II: DEEP DRILL TECHNOLOGY, THE CORE PROCESSING LINE AND CAMP DESIGN

(Moderator: K Kuivinen)

The role of the engineering and technical services group at the Polar Ice Coring Office (PICO) is to provide the deep ice core drill, sidewall sampling, borehole instrumentation, bedrock and sub-ice sediment sampling equipment to meet the needs of the scientists. Off-the shelf technology will be used where applicable; some new ice coring and ancillary shallow coring and access hold drilling equipment will be designed and fabricated by PICO.

The core processing line is defined as an equipment and procedures needed to handle the ice core once it is removed from the deep drill. The design criteria for this processing line are dependent on the extent to which scientists plan to sample and analyze core in the field, and the rate of core production and optimal core processing.

The deep drill camp design is dependent on the extent and length of site occupation, the number of personnel on site, the size of equipment to be transported, the extent to which auxiliary projects will be using the site as a base for traverse and satellite projects, the airport facilities required.

The following considerations for deep drill design parameters, core processing line and camp design were discussed:

A. Deep Drill Technology

     1. Core diameter will be 5.2-inch (<20 kg/m). Five-inch diameter core could be considered as maximum size for handling purposes; the larger the 
better for sampling.
     2. Core productivity is planned at 2-3m per run for the prototype and 1000m drilling. For greater depths core barrels would be extended to 6-m length. This reduces transit time up and down hole. The core processing line must be scaled up to handle increased length.
     3. Drill materials (stainless steel, polyethylene, viton, composites, scintered tungsten heads, diamond bits) will be provided to geochemists for testing.
     4. Toluene appears to be a good candidate for a deep drilling fluid. Samples will be provided for testing.
     5. Sidewall sampling (coring and notch sawing) capabilities exist and  directional drilling will be investigated further to meet science needs at  critical depth/age targets. Good depth control in the borehole is critical.  Samples could be pressurized upon retrieval.
     6. Pressurized cores could be collected on an intermittent basis to control microcracking.
     7. Borehole logging capabilities should include temperature, diameter azimuth and inclination. If hole wall could be polished, conductivity could be 
measured continuously. 'Me capability of inserting vertical strain rings on 
markers in the hole wall should be investigated. Good depth control is critical.
     8. Sub-ice sampling and sampling of basal ice is important.
     9. Hot water drilling could provide rapid access to great depths in ice 
(estimate 3000m. in one week of drilling; 0.5m/minute penetration rate). 
Core could be taken on air intermittent basis.
     10. Existing radar resolution can detect ice/bedrock to ± 5m.

B. Deep Core Processing

     1. High pressure fluid (e.g., toluene if used as drilling fluid) could be used to cut core. Advantages over a bandsaw are: no vibration, small kerf (.25mm). Tests should be done on sample ice prior to decision to use fluid over a bandsaw.
     2. The rate at which core can be processed depends on the number of 
investigators that must handle/sample the core in the field. Fifty meters of 
core per day (average) should be manageable.
     3. Core should be allowed to relax after drilling and before cutting/processing. Several days worth of core storage capability should be provided.
     4. Core produced in this brittle ice zone (700-1400m est.) could be fractured but intact after elastic relaxation. A pressure equilibration chamber should be considered.
     5. The issue of -core archiving has not been resolved. The concept of minimal core processing in the field, with core being retrograded to a centralized ice core processing facility in the U.S. was discussed. This could enable investigators to conduct their field session in a controlled laboratory 
environment at a more convenient and possibly cost-effective location than a remote field camp. A subcommittee will provide an outline of facility  specifications so that PICO can do a cost evaluation. The ocean core curation system might be considered as a model.
     6. Core packaging materials should be defined to reduce contamination. New insulating foams blown with C02 should be used instead of polyurethane.

C. Deep Drill Camp

     1. Drilling will be done on the snow surface inside a windbreak structure.
     2. Core processing will be done in a subsurface trench.
     3. Core will be stored in a subsurface trench.
     4. The key to logistical cost savings is to reduce heavy-lift air support (LC- 130) flight hours by minimi7ing fuel consumption, permanent camp structures, heavy surface vehicles, and rotation of personnel. Core samples would be retrograded on the return leg of re-supply flights at projected one-month intervals.

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