Hydrocarbon Families in the Maracaibo Basin, Western Venezuela

Wolfgang Scherer, S. A. Intevep

The Maracaibo basin is a prolific oil province situated in an intra-montane basin between the Perija and Andes mountain ranges in western Venezuela. It produces more than 2MM BOPD from Miocene, Eocene and Cretaceous reservoirs. The main, for some authors only, source rock is believed to be the upper Cretaceous La Luna formation, nevertheless seeps and crude oils of greatly varying compositions have been reported and interpreted as originating from different facies of that formation. The objective of the present study was to obtain an unbiased, quantitative classification of crude oils from the Maracaibo basin, establish the areal distribution of these families and correlate them with geologic variables representing sedimentary and tectonic conditions that are thought to b favorable for oil generation.

Peak heights of C₁₃-C₃₃ gas chromatograms from the saturate fraction of more than 90 crude oils and 20 oil seeps were statistically analyzed with simple Euclidean distance coefficients and Q-mode principal components; the resulting dendrogram shows six (6) natural families of crude oils that were mapped over the basin. Regional geologic maps of the La Luna Fm including stratigraphic (isopach, facies, organic carbon, etc) and structural (number of faults, max. displacement, length of fault segments, etc) variables were than discretized and correlated with these families.

From this it can be concluded that the hypothesis of a single source rock is probably true for most of the basin, except for the southwestern portion, and at least three families can be correlated to geologic variables thus establishing a meaningful geologic-genetic classification.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995