The relative contents of saturated and aromatic hydrocarbons 

 decreased perceptibly (Fig. 5) in nearly constant proportions, the 

 ratio SAT/ARO decreased slightly probably because of a significant 

 increase in resins -- from 17 to 40 % by weight. After January 1980, 

 however, contents of all these substance remained about the same. 



4 



AW 31-3-71 



%AR0 



AW 22 II 78 



AW ?C E 7S 



AW 17 1-80 



AW 24-6-80 



FIGURE 5. Evolution of the various chemical families (saturated 

 hydrocarbons, aromatic hydrocarbons, polar compounds). 



The increase in resin contents results from an oxidation degra- 

 dation of the crude in the medium, reflected in a perceptible upward 

 curve of the absorption bands under infra-red at the level of the 

 hydroxyls (3,600 to 2,900 cm" 1 ) and the carbonyls — including 

 esters, and a qreat predominance of Carboxylic acids (1,740 -> 



116 



