Replicate Coring System for 98mm Electromechanical Drill - Whipstock Conceptual Documentation

Replicate coring systems (RCS) provide a means for additional core samples with high scientific value to be collected from an existing borehole. Considerable conservation of resources can be realized by the implementation and deployment of core replicating technology which is integrated into an established drilling/coring system. A long range (>3km) core replicating system has been designed and successfully deployed with the Deep Ice-Sheet Coring (DISC) Drill system to retrieve cores at five separate deviation points. The DISC Drill produced 122mm diameter core and the RCS produced 108mm diameter. This particular RCS provided operators complete autonomous control of position and inclination for initiating a deviated path including on the uphill side of the parent borehole. Adapting this technology to the Hans Tausen (HT) type drill design with 98mm diameter core, specifically the Ice Drilling Design and Operations' (IDDO) Intermediate Depth Drill (IDD) and Foro 3000 Drill, is not feasible without completely redesigning the drill systems due to the electronic and mechanical complexity of the technology.

Motivated by science community priorities articulated in the U.S. Ice Drilling Program Long Range Science Plan, the need for RCS capabilities to be adapted for use with the IDD and Foro 3000 systems was identified. The requirements and subsequent design for new a RCS can realize a relative simplification of the controls scheme in that deviations are allowed at any azimuth. Deviations made on the downhill side of a parent borehole are permitted and steering capabilities may be excluded. Further, the azimuthal orientation may be unknown during replicate coring operations. When the angular departure from the parent borehole is small, replicated core samples can be recovered from the same location in the ice sheet as original cores.

Independent replication and verification of experimental science relies on the highly specialized design and operation of ice drilling equipment to obtain samples of superior quality. Additionally, infrastructure costs associated with initiating a new intermediate depth or deep drilling site are significant. Replicate coring systems will facilitate maximizing the return of funding by the collection of additional ice from specific areas of high scientific value without having to drill a complete new borehole (Severinghaus, 2008).