to the ocean floor which are recorded on a seismograph as 

 they bounce back to the surface. The time it takes (inter- 

 vals) for the waves to go down and return reveals whether the 

 formation is hard or soft and the actual depth of the forma- 

 tion (Shell, 1975: 8). Seismic surveys are extremely useful 

 in locating geologic structures that could "trap" oil and gas 

 to form a commercial deposit. Direct hydrocarbon detection 

 is the latest technological advance in the effort to locate 

 more oil and gas reserves ( Offshore , January 1976a: 100). It 

 consists of a series of new and different techniques which 

 measure physicochemical phenomena (generation of an electric 

 current) in rocks associated with the presence of underground 

 pooled hydrocarbons (Pirson, 1973: 63-66). Recent gains in 

 successfully pinpointing probable deposits have been rewarding. 

 Phase 3 is centered around the drilling of exploratory 



wells by one of the four basic types of mobile platforms: drill 



5 

 ships, jack-ups, semi-submersibles , or drilling barges. Each 



type is designated for and limited by the depth of the water 



in which it will be operating and the average adverse weather 



conditions that can be expected to be encountered (Council on 



Environmental Quality, 1974-III: A-3). 



Drilling 



There are five basic types of drilling platforms found 

 on the Gulf of Mexico Outer Continental Shelf; drilling barges, 



5 

 A more detailed description of each type will be given in the 



upcoming analysis of drilling platforms. 



15 



