The technology for wireline re‐entry of deep ocean boreholes employed for the Dianaut Program

More than 850 holes have been drilled in the world's oceans over the past 24 years, in connection with the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP). At least 45 of these holes were fitted with a re-entry cone and many were cased through the sedimentary and unconsolidated layers, allowing hole re-entry with a drill string from a drilling vessel and wireline logging to the drill stem. Re-entry of seafloor drill holes with a wireline logger positioned on the seabed was first successfully accomplished during the FARE program. The DIANAUT program was a scientific application of seafloor wireline re-entry utilizing the logging shuttle ‘Nadia’ in combination with the manned submersible ‘Nautile’. The Nadia re-entry logging system was successfully seated in drill re-entry cones of three boreholes in the Atlantic Ocean (water depths of 1666, 4485, and, 4976 m) and logging operations with different probes (temperature, heat-pulse flowmeter, BHTV, fluid sampler, magnetometer) were performed from the seafloor with full logging control and data acquisition from the Nautile. In the near future the logging shuttle ‘Nadia’ could be developed into a support facility for long-term downhole measurements and later into an unmanned seafloor logging system.