SOURCE ROCKS AND OIL FAMILIES, SOUTHWEST MARACAIBO BASIN (CATATUMBO SUBBASIN), COLOMBIA

An extensive evaluation of organic source facies, the application of h ydrocarbon geochemistry, and integrated basin modeling of the southwes t portion of the Maracaibo basin in Colombia (referred to as the Catat umbo subbasin) indicate (1) multiple organic-rich horizons occur withi n-the Cretaceous and Paleocene sections, (2) most of the reservoired o il and gas was sourced locally from Cretaceous marine carbonate facies by means of lateral and vertical migration, (3) two subfamilies of Cr etaceous oils are recognized that reflect different source facies with in the Cretaceous section and different maturation and migration histo ries, (4) oil and gas present in the southern Catatumbo subbasin indic ate a contribution from Paleocene terrestrial source facies that requi red westerly migration from a source area in Venezuela, possibly withi n the North Andean foredeep, and (5) oil generation from Cretaceous so urce rocks began in the Oligocene, and peak generation occurred in the late Miocene. These key conclusions are based on source rock analyses of 365 rock samples from eight wells, gas chromatography/mass spectro metry, and isotope and bulk composition analyses from nine rock extrac ts and seven oil samples.