Figure 1 shows the distribution of relative ethane concentrations 

 (where the total open ocean surface values of Co hydrocarbons are set 

 equal to one) around a group of platforms located off the central 

 Louisiana coast. All saturated Co to Cg hydrocarbons, which are cer- 

 tainly petrogenic, as well as methane, which may also be formed 

 biologically, showed approximately the same relative concentrations. 

 The highest values, 85,000 times open ocean values or about 0.3 ml of 

 ethane per liter of sea water, were found near what appeared to be 

 an underwater "flare." This phenomenon, a large volume of gas 

 bubbling to the surface at one spot next to one platform, covered an 

 area of several hundred square feet. This technique of disposing of 

 gas appears to be a common one. High hydrocarbon levels, apparently 

 from this one source, were observed in the surface water over an area 

 greater than 25 square miles. This location was visited three times in 

 four months with no apparent change in the appearance of this "flare" 

 or the high levels of hydrocarbons in the surrounding water column. 



On two subsequent cruises, four other flares were found, indicating 



Figure 1. Relative ethane concentrations (1 — 3 X 10-^ ml of dissolved ethane at 

 S.T.P. per liter of sea water) at 28°50'N 92°00'W. Solid squares are locations of 

 platforms; solid circles are exposed well heads. 



14 



