How do we explain the giant reserves of northern South America?

Abstract

Reported reserves of Colombia, Venezuela and Trinidad record the world’s most prolific known hydrocarbon province. STOIIP of 1.5 trillion barrels of the spectacular Orinoco Heavy Oil Belt of Venezuela (and its extension in Colombia) implies original generation of at least 3 trillion bbls. While the upper Cretaceous source rocks rank among the world’s richest in organic content and thickness (TOC up to 11%, over 100 metres thick), reported kitchen areas related to Oligocene — Recent foreland basins and limited in area, do not explain the huge volumes. Graphitic quartzose, phyllite and marble in metamorphosed sections north of the sedimentary source rock occurrences record former hydrocarbon systems perhaps 1000s of metres thick and extending down to the Jurassic. Similar rocks occur in the offshore, ranging from upper Jurassic — upper Cretaceous, along with radiolarites, cherts, basalts and volcanic rocks. All this suggests that northern S America formerly was a vast area of source rock accumulation and maturation in regional foreland basins. Hydrocarbons migrated, perhaps remigrated, updip to structural and stratigraphic traps.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018