The Ocean Drilling Program is an internationally-funded geoscience research program which recovers cores and data from the seabed. Since 1985, operations have been carried out worldwide in water depths ranging from 40 to 6000 m. From time to time, the operations of the program come into conflict with other uses of the seafloor. Drill sites identified on the basis of underway geophysical surveys have been found to coincide with the locations of munitions dump sites, low-level radioactive waste disposal sites and submarine telephone cables. The drill sites are moved in order to avoid disturbing pre-existing artifacts on the seafloor, or operations are modified to minimize the chance that undesirable material might be recovered to the ship. ODP has also used its drill string to recover a small scientific instrument lost by another oceanographic expedition. The precision with which the bottom of the drill string can be moved in relation to objects on the seafloor is discussed. The drill string could be used to recover much larger loads from the ocean floor, comparable in weight to some of the drilling equipment. The lifting capability of the drill string as a function of water depth is discussed.
In January 1995 the scientific drillship JOIDES Resolution, registered name SEDCO/BP 471, completed ten years of operations for the Ocean Drilling Program (ODP). ODP is an internationally-funded geoscience research program which recovers cores and data from the seabed. JOIDES Resolution is on long-term charter from Sedco-Forex to Texas A&M University, the Science Operator of ODP.
Over the past ten years, ODP has operated worldwide in latitudes ranging from more than 80° N off Spitsbergen to nearly 71 °S in the Weddell Sea. Operations have been carried out in water depths ranging from 38 to 5969 m. Most of the holes drilled by ODP are single-bit holes at sites chosen on the basis of underway geophysical surveys. Even large objects, such as shipwrecks, cannot be resolved in oceanic depths by geophysical equipment operated near the seasurface. Thus we are not aware in most of our operations of what man-made objects may exist in the vicinity of the drill site. However, in twenty five years of scientific ocean drilling by the drillships Glomar Challenger and JOIDES Resolution, there is no evidence of human artifacts being encountered by the drill string or recovered in the cores, apart from equipment deployed by the drillships themselves or that we have deliberately attempted to recover.
The depth of a single-bit hole is limited by the life of the drill bit, or occasionally by complications of the geology. To achieve deeper penetrations, re-entry holes are required. A re-entry cone or hard-rock guide base, depending on the nature of the bottom, is placed on the seafloor, allowing the drillship to withdraw the pipe from the hole and re-enter it as many times as required.
