Undersea Drilling and Production Sites for Petroleum

Abstract

Large undersea installations with shirtsleeve environment have existed under the continental shelves for many decades, The technology now exists, using off-the-shelf petroleum and mining equipment, to establish permanent manned installations within the sea floor- that can be used for well drilling and initial petroleum fluid processing. The past and present permanent, in-the-sea-floor mining industry is reviewed and methods now practical for direct access to and from permanent in-the-sea-floor drilling and production sites are outlined. Drill sites beneath the sea floor are free of weather and floating ice hazards, and enable complete access to the wellhead area by technicians and laborers. A present estimate for such an operating site is approximately $50 million. Introduction The petroleum industry has become deeply and irrevocably involved in producing gas and oil from the continental shelves. Chief among the problems of offshore drilling today is the hazard presented by the air-water interface, i.e., the damage potential of serious storms and waves, an example of which is the recent destruction of a British petroleum platform, costing 11 lives. To overcome the problems of working at the unstable air-water interface. the present industrial trend is to go to the sea floor. The following statement is appropriate: "The consensus of oil companies is that by 1975, if technology is available, most stationary installations will be on the bottom of the sea, not on the surface."' In addition to working on the bottom of the sea while keeping the drilling platform on the surface, there is another major potential solution to the problems of offshore drilling. This solution is literally to burrow into the sea floor, using the rock as the construction medium for drilling and production sites in which all activities are carried out in a normal one-atmosphere environment. Fig. 1 illustrates the practicality of this approach. This machine shop bay is part of a mining complex with approximately 7 1/2 sq miles of open, permanent floor space. The individual shop bay is some 500 ft long. The striking aspect is that this existing installation is located beneath 400 ft of water, some 2 1/2 miles off the shore of an island on the eastern coast of Canada. The installation is 1,500 ft below sea level. A series of openings such as the one illustrated, excavated in the sea floor, could obviously contain an extensive petroleum drilling and production installation and very extensive bulk storage and processing installations. This article discusses how the study program called Rock Site, conducted at the U.S. Naval Weapons Center, has led to the conclusion that petroleum production sites, as well as many other industrial operations, can be located within the bedrock beneath the sea floor, using only existing tools and technology. JPT P. 1309ˆ