Deep-Water Coring for Scientific Purposes

Abstract

Larson, V.F., SPE-AIME, Deep Sea Drilling Project, Scripps Institution of Oceanography of the U. of California The Deep Sea Drilling Project is now almost 7 years old. Many articles have been written on the design of the drilling vessel, Glomar Challenger, and the equipment used for drilling in water depths up to 20,000 ft. Now, after drilling and coring more than 500,000 ft of hole, a review of the project's operational experience is presented. Introduction Since 1968, the Deep Sea Drilling Project (DSDP) has used a dynamically positioned drillship, the Glomar Challenger, in a world-wide scientific research program for recovering sediment cores from the deep oceans and adjacent seas. Short sections of underlying igneous and metamorphic rocks also have been recovered. The objective of this basic geologic research is to learn about the origin and history of the earth through the study of samples obtained in previously inaccessible sites. Operations have been conducted successfully in water depths greater than 20,000 ft and in polar latitudes to 77 degrees south and 76 degrees north. More than 120,000 ft of cores have been recovered. Previous reports have described the drillship, positioning system, re-entry equipment, and coring bits. positioning system, re-entry equipment, and coring bits. This paper summarizes the operational accomplishments and experience with the various systems. Coring procedures are described and improvements and new tools developed are discussed. A brief description is given of future scientific objectives and the challenging technological program that will be required to meet them. program that will be required to meet them. History The use of drilling to study the ocean was first considered seriously 17 years ago by Project Mohole, which was supported by the National Science Foundation (NSF). Early in 1961, Project Mohole produced the first successful drilling and coring operation in deep water. The barge Cuss I, equipped with dynamic positioning, drilled five holes near San Diego in around 3,300 ft of water and five more near Guadalupe Island in water depths of nearly 12,000 ft. The feasibility of scientific deep-sea drilling thus was demonstrated. In May 1964, the directors of the Institute of Marine Sciences of Miami U., Lamont Geological Observatory of Columbia U., Woods Hole Oceanographic Institution, and Scripps Institution of Oceanography of the U. of California signed a formal agreement establishing Joint Oceanographic Institutions Deep Earth Sampling (JOIDES) to cooperate in deep-sea drilling. Initial drilling was conducted in 1965 on the Blake Plateau off the southeastern U.S. coast. The work was conducted from the R/V Caldrill, funded by the NSF, and managed by Lamont. The success of the Blake Plateau work (water depths of 100 to 3,300 ft) stimulated plans for drilling in deeper water. Studies at the time showed that much more could be learned from an immediate advance into deep water, and that the petroleum industry was moving rapidly into the shallower depths partly for purposes of research. These studies also showed that the technology existed for drilling in water depths of 20,000 ft at a reasonable cost. In 1964, the director of NSF announced his intention to support such a program, and the fiscal year 1966 NSF budget approved by Congress included funds to initiate a national Ocean Sediment Coring Program. JPT P. 925