great as 20,000 feet. This program of basic 

 scientific investigaion, utilizing the equipment and 

 capabilities of the petroleum industry, wUl explore 

 in several of the world's oceans and major seas. 



In general, there are no operating limitations to 

 geological and geophysical evaluation of the U.S. 

 continental margins. However, the only way that 

 the presence or absence of oil or gas can ever be 

 determined is by drilling of exploratory wells deep 

 into the rocks beneath the sea floor. 



B. Drilling Capabilities 



The drilling of an exploration or development 

 well is more difficult and expensive than drilling a 

 core hole because repeated reentry into the hole is 

 required, casing must be set in the hole to keep it 

 open and control drilling fluids or fluids in the 

 rock, large blowout preventors must be installed in 

 case high-pressure oil or gas is encountered, and 

 the drilling rig must maintain position at the 

 wellsite for many weeks or months instead of a 

 few days. More than 9,000 wells have already been 

 drilled into the U.S. continental shelves. The 

 deepest water, 632 feet, in which an exploration 

 well has been successfully drilled is located off 

 southern California. Similar wells have been drilled 

 in the Mediterranean off Libya. This depth in- 

 cludes virtually all of the U.S. continental shelves. 



The petroleum industry has more than $1 

 billion worth of offshore drilling equipment pre- 

 sently at work. Nearly 1 50 mobile drilling vessels 

 are now operating, some costing more than $10 

 million to build and up to $750,000 a month to 

 operate. Some have the drilling rig mounted on a 

 conventional ship-shaped hull; others have legs 

 taller than a 30-story building which are jacked 

 dovra to the sea floor in order to raise the drilling 

 platform above the turbulent surface of the sea; 

 others are floated to the drilling site on similar tall 

 legs, which are then flooded to rest on the sea 

 floor; and in others the drilUng platform is held 

 above the sea surface by partly submerged buoy- 

 ant legs (Figure 6). 



The floating drilling vessels are normally se- 

 cured over the drill hole by a system of anchors. 

 However, many of the newer vessels for deep 

 water are equipped with various types of propel- 

 lers that can dynamically position the vessel over 

 the hole during drilling. There is little doubt that 

 exploratory and production wells can now be 



drilled successfully in water as deep as 1 ,000 feet. 

 One company recently announced that they plan 

 to drill a well off California in 1 ,300 feet of water 

 by the end of 1968. 



C. Production Capabilities 



The ability to explore and to drill for marine 

 petroleum resources in deep water presently ex- 

 ceeds the capability to produce it once it is found. 

 This may be due in part to the fact that 

 exploration has only very recently been extended 

 into deep-water areas, and there is as yet no need 

 for deep-water production capabilities. However, it 

 is also true that many of the problems associated 

 with petroleum production at sea are more diffi- 

 cult to solve than those associated wdth marine 

 exploration or drilling. 



A completed well must be accessible for 

 periodic maintenance. Oil wells may require 

 paraffin and sand removal, corrosion prevention, 

 and both oil and gas wells may require remedial 

 work on the hole itself. Separation and treating 

 equipment is needed to provide adequate sepa- 

 ration and measurement of the oil, gas, water, and 

 natural gas liquids produced. Oil and natural gas 

 liquids also must normally be stored and measured 

 before transportation to the shore or to an 

 offshore loading facility. The producing well must 

 have flexible control mechanisms for well-testing, 

 flow-rate control and shutdown during 

 emergencies. Gas is normally flowed directly into 

 the pipeline, but commonly a major problem is the 

 formation of solid hydrates which plug lines and 

 valves under certain temperature and pressure 

 conditions. 



These and other problems have been solved to 

 date largely by installing the well-head and pro- 

 ducing equipment on permanent platforms resting 

 on the sea floor and standing above sea level. In 

 other cases the subsurface reservoir is close enough 

 to shore that the well-head and producing equip- 

 ment can be located on land, and in other cases 

 man-made islands have been built to hold these 

 facilities. Obviously these approaches are confined 

 to fairly shallow waters. Permanent platforms, 

 however, have now been installed in 340 feet of 

 water off Louisiana and some companies believe 

 they can be installed in 600 feet of water or more. 

 Under some conditions as many as 60 wells can be 

 drilled directionally from a single production 



VlI-205 



