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Victoria University Antarctic Research Expedition Science and Logistics Reports 1998-99: VUWAE 43

1.4 CRP-3 in 1999 - Scientific and Drilling preparations

1.4 CRP-3 in 1999 - Scientific and Drilling preparations

  • Satellite imagery. The same level of service and supply of product that was achieved in 1998 will be required for the analysis and prediction of any planned drilling season in 1999. The first Radar Sat images hopefully can be supplied by 1 August and navigation control will be improved.
  • Currents. We collected a good suite of current data near the expected CRP-3 site. This data will be worked on in the following few months and will be used to help refine the drilling strategy for the CRP-3 hole.
  • Riser Deployment. We now have more confidence in operating the riser with minimum top tension for short periods and are prepared to core ahead as a matter of course to assist riser embedment. We expect to use the main winch bump-in method to embed the riser into clast-rich sediments and plan to use a more robust riser cutting shoe. The use of the two-arm under-reamer is not necessarily ruled out but appropriate strata will be required if its deployment is considered. The proper embedment of the riser is still paramount to achieving good down-hole progress. The available embedment techniques are limited and relatively slow but have now been shown to be successful. CRP-3 will be in deeper water, about 350 m, and although we have gained valuable experience in 1998 we should expect drilling operations to take about the same time as for CRP-2. - Drilling prognosis. CRP-3 should begin coring in the time equivalent of the lowest 200 m of CIROS- 1 then into strata of unknown fades and age. In general we can expect the formation to increase in hardness, but circulation was lost in a conglomerate at the base of CIROS-1, and we should expect intervals of circulation loss deep in CRP-3 also. Increase in the expanding clay content of the strata can be expected as we drill into the warmer conditions of the Eocene. This will require maintenance of the potassium content of the drill fluids to avoid expanding clay-induced problems down hole. The drill fluid programme planned for CRP-3 is based on the consumption of fluid in CRP-2/2A and will consist of basically the same mud compositions.