Author(s): Luis Miguel Bernardo, Petroleum Exploration Consultants Americas
The geochemical analysis of rock and oil samples as an integrated approach for the southeastern Caribbean region and the Guiana Basin permitted the identification of five marine source rocks (SRs) in these highly complex areas. All the identified SRs are marine, but they are clearly distinctive in terms of their redox condition, depositional environment, lithology, age, and organic matter input. The five source rocks identified are: 1) Eocene sequences located in the Barbados Accretionary Prism. These immature sequences are characterized by the presence of TOC values as high as 17.20% with an average of 2.98%. Kerogen is of Type II to Type III. Barbados oils are correlated to similar SR facies. 2) Upper Cretaceous Gutier Naparima Hill Fm. is identified as the marine SR’s that generated most of Trinidad oil. TOC values averaging 2.2%, and kerogen Type II to Type II/III, and is thermally immature to mature. 3) Also, in Trinidad, some oils indicate a marine SR with important terrestrial input (Type III/II), deposited under disoxic conditions, and possible Cenozoic age, as suggested by biomarkers. 4) The Orinoco Delta oil seeps indicate that existence of a marine SR deposited under highly anoxic conditions, characterized by a biogenic-rich lithology, which was apparently deposited at the base of the Cretaceous paleo-slope, in the Guiana Basin; 5) Cenomanian - Santonian sequences of the Canje Fm. deposited along the Guiana Basin and the Demerara Plateau. Lateral and vertical facies changes are typical in this sedimentary succession. The best hydrocarbon generative facies record slope environments with black shales with TOC’s ranging from 2% to 15% of kerogen Type II. Transitional facies within this sequence have fair TOC values between 1.0 and 2.68%, and kerogen Type III/II.
Luis Miguel Bernardo, Petroleum Exploration Consultants Americas
Luis earned a BS in Chemistry from the Universidad Central de Venezuela and a MSc in Geology from the University of Houston.
With over 20 years of experience, he is Petroleum Geochemist Consultant at Petroleum Exploration Consultants Americas in Houston. He has previously worked at companies such as Repsol, YPF, Ecopetrol and PDVSA. Luis is a member of AAPG and Alago.