36 



in 1,500 feet of water, in the vicinity of a prolific strike (Humble/Stan- 

 cal Tract 325) in 1,050 feet of water. Humble Oil has also announced 

 plans to install a GO-well platform for drilling and production in 700 

 feet of water in the Santa Barbara Channel. With exploratory drill- 

 ing it is easier to achieve added depth capability than with pro- 

 duction drilling, because once the hole is drilled no more equipment is 

 needed as in the production wells. Reentry is a basic requirement in 

 drilling for petroleum. At certain intervals, when the bit wears out, 

 a new bit has to replace the old bit. In order to accomplish this, the 

 whole pipe length in the hole has to be withdrawn, the old bit is 

 replaced, and the drill string is reintroduced into the hole. Guidance 

 back into the hole is hard to achieve in deep waters. 



In research drilling, no reentry into the hole is required. This is 

 why the GloTnar Challenger was able to drill and core in 11,720 feet 

 of water on Sigsbee Knolls, and later set a record in the North Atlantic, 

 drilling 2,759 feet below the ocean floor in 16,316 feet of water. Power- 

 ing about 4 miles of drillpipe from a floating vessel is no small feat ! 

 However, as evidence of the rapid development in drilling technology, 

 a breakthrough was achieved by the Glomar Challenger when, on 

 June 14, 1970, a deep-water hole was successfully reentered. The crew 

 changed the worn-out bit and succeeded in finding and reentering the 

 hole m 10,000 feet of water. Several months later, a similar operation 

 was successfully completed in 13,000 feet of water; the bit wore out 

 after drilling 2,300 feet into the sea floor, was changed and reentered 

 into the same hole to drill 200 additional feet. Reentry was accom- 

 plished with the aid of a high-resolution scanning sonar system looking 

 through the drill bit and guiding it into a funnel-shaped receiving 

 cone mounted on the ocean floor, and a system for steering the drill pipe 

 toward the cone. This achievement heralded a new era in offshore 

 technology, but only for drilling, not for production. The aim, how- 

 ever, is production — a challenge more formidable though not insur- 

 mountable. 



PRODUCTION 



Following successful and promising exploratory drilling, a well is 

 completed and equipped for production. Production requires the 

 installation of a well head, a valve complex often called the "christmas 

 tree," flow lines to move the oil to the separators, separators to separate 

 the gas from the oil, and pipelines to transfer the products to storage 

 tanks and refineries. 



Some of this equipment is installed on platforms above water at 

 shallow depths to about 300 feet, and on the ocean floor in deeper 

 waters. There are problems of installation, production, and servicing. 

 The last is a major activity which is performed periodically through- 

 out the life of the well. Oil well ancillary services involve a number 

 of complicated activities often critically limited by water depth. One 

 such activity includes the services of divers, underwater submersibles, 

 and the attending support vessels and equipment. 



The majority of above-water production facilities is effective for 

 wells in waters no deeper than 340 feet, although new designs have 

 pushed this limit to twice the depth. As water depth increases, how- 

 ever, drilling costs increase drastically (see Appendix 10). In the 

 Gulf of Mexico, for example, the cost for existing platforms rises 



