Deep Core Drilling in the East Antarctic Ice Sheet: A Prospectus

A major objective of the International Antarctic Glaciological Project (IA GP) is to core drill through the East Antarctic Ice Sheet and into the bedrock beneath it.

The drilling site will be remote from major bases at an elevation of over 3000 m. All equipment and supplies will be flown in using ski-equipped C-130 aircraft.

A unique drill pipe consisting of lengths of fiberglass-reinforced epoxy pipe cemented to lightweight steel tool joints has been developed which weighs only 2.87 kg/m and costs less than $25/m.

This development makes it possible to use a lightweight wireline core-drilling system which minimizes the logistics burden, the time required for drilling, and the cost of the operation.

The wireline core-drilling system consists of a coring bit attached to the core barrel outer tube assembly which is rotated by the drill pipe, the non-rotating core barrel inner-tube and core lifter assembly, a wireline hoist with an overshot attached to its cable which is used to retrieve the core-laden inner tube through the inside of the drill pipe, a means of supporting and rotating the drill string, and a means of circulating the drilling fluid which removes the cuttings from the hole and prevents its closure by plastic flow of the ice due to the overburden pressure.

Cold air will be the drilling fluid for the upper 1000 m of the hole. Use of a reverse air vacuum circulation system eliminates the requirement for an air-cooling system and results in the production of very clean uncontaminated ice cores.

At a depth of about 1000 m arctic-grade diesel fuel (DFA) will be used as the drilling fluid to reduce hole closure and remove the cuttings.

The DFA will be pumped through the drill pipe and carry the cuttings up through the annulus to a separator on the surface. The clarified DFA will be recirculated through the drill string.

It is intended to fleld test all components of the wireline core drilling system on the Ross Ice Shelf Project in Antarctica during the 1975-1976 austral summer.

A program is recommended which would make it possible to begin the US. deep core drilling in ice portion of the lAGP as early as the 1976-1977 season.