A series of monounsaturated triterpenes have been identified in an oil
from Utue Field of the Niger delta. The triterpenes are the angiosper
m-derived olean-13(18)-ene, olean-12-ene, olean-18-ene, baur-7-ene, an
d urs-12-ene. The presence of these compounds in oils is attributed to
the extraction of thermally immature Agbada shales by the migrating f
luid and in the reservoir. The terpane biomarker signature of the oil
does not appear to have been altered by this phenomenon.