Deep-sea borehole re-entry with fiber optic wireline technology

In September 1999, the Marine Physical Laboratory´s control vehicle (CV) was deployed on a 17.3 mm armored electro-optical tow cable to retrieve 300-600 m long instrument strings from deep-sea boreholes drilled near the Juan de Fuca Ridge by the Ocean Drilling Program (ODP). The CV was used also to deposit heavy instruments near the well heads for subsequent operations by the research submarine Alvin, and to re-enter and log ODP hole 1026B. The wireline technology and techniques used for this work are described in this paper. In particular, re-entry operations involved lowering a 5 m long probe, about 7 cm in diameter, into the 9 cm opening diameter of the hole´s circulation obviation retrofit kit in 2600 m of water depth. Grappling and re-entry operations were made possible by a combination of dynamic positioning of the ship, long baseline acoustic navigation of the CV and of the probe, and real-time video through fiber optic telemetry on the tow cable