Naphthenic Acid
Distribution in Crude Oils: Effects of Biodegradation
Chen, ZhengZheng1, J. Michael
Moldowan2 (1) Stanford University, Houston, TX (2) Stanford University, Stanford, CA
Californian oils and Mediterranean oils
have drastically different acid profiles with increasing severity of
biodegradation. Biodegraded oils from San Joaquin Valley are characterized by a
sequential generation-destruction pattern of naphthenic acids, which include
n-alkanoic acids, tricyclic-terpenoid acids, and penta-cyclic terpenoid acids.
Oils and rock extracts from Mediterranean basin, however, features incremental
abundance in all three types of acids. 25-norhopanoic acids remained the most
resistant acid components in Californian samples while being absent in Mediterranean
sample sets. Profiles of acid components provides
independent evidence about bacterial activities involved in biodegradation. For
heavily biodegraded oils, dominance of different types of acids may have
implications in explaining inconsistency observed between crude oil corrosivity
and total acid number.