Unraveling the Caribbean Petroleum Habitat

Abstract

This study performed a quantitative geochemical evaluation of petroleum samples across seven Caribbean regions: Cariaco, Tobago Trough, Barbados, Dominican Republic, Jamaica, Nicaraguan Rise, Chorotega, the Lower Magdalena, Guajira, and Falcon. Additionally, oils from the Maracaibo and Guyana basins were used to establish oil-oil correlations between the Caribbean and South America (La Luna Fm. and its equivalents). We applied a suite of conventional geochemical and multivariate statistical analyses (e.g. hierarchical cluster analysis and PCA) to identify the main characteristics of their original source rock and to establish their genetic correlation.

Saturate and aromatic biomarkers and bulk geochemical analysis from 30 oil samples indicate that almost all oils were generated by marine source rocks with unique geochemical signatures. The Dominican Republic oil; however, could have been generated by a lacustrine source rock - striking surprise for the region. One distinctive oil family has been identified in each basin, but it was not possible to establish a genetic correlation between the different oil families. The age of all families ranges from late Cretaceous to Miocene. All oils were generated by local source rocks controlled by the complex tectonic history of the Caribbean. The main geochemical differences between the oil families are controlled by: 1) organic input 2) depositional environment; 3) redox conditions; 4) lithology, and 5) age. Thermal maturity and post-accumulation processes do not have a major influence on the particular differences of the oils. The Caribbean oil families are not correlative with the late Cretaceous source rock in South America.

Our oil geochemical analyses suggest that it is necessary to evaluate multiple geochemical parameters to effectively characterize and to correlate oils. An evaluation based only on few pre-established parameters could lead to a completely erroneous characterization and correlation. Multivariate statistical analyses are excellent tools for this purpose, permitting the simultaneous analysis and comparison of multiple oil properties.

A geochemical gas evaluation suggests that in the Caribbean accumulations are mainly biogenic, with a minor thermogenic component. The gas associated with the Caribbean small oil accumulations is primarily thermogenic and generated at the same maturity level than the oils. To date, no important deep gas sources have been identified in the Caribbean basins.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018