RODRIGUES, KIRTON, Trinidad and Tobago Oil Company Limited, Exploration and Production Research Services, Pointe-a-Pierre, Trinidad, West Indies

ABSTRACT: The Naparima Hill--Cruse/Forest/Gros Morne Petroleum System of Trinidad: A Quantitative Evaluation of Petroleum Generated

Trinidad is situated at the eastern end of the prolific Maturin basin of Eastern Venezuela where more than 9.5 billion barrels of oil have been produced over the last 80 years, with recoverable reserves estimated at 40 billion barrels.

The Naparima Hill--Cruse/Forest/Gros Morne (NH-C/F/GM) petroleum system is proposed for the Trinidad area following the established definition and nomenclature of petroleum systems. This system covers an area of 14,000 sq km and has produced 2.5 billion barrels of oil from more than 25 oil fields, including 7 giants.

More than 9 km of Lower Cretaceous to Pleistocene sediments, primarily of continental origin, have been deposited within the NH-C/F/GM system. These sediments include the source beds of the Upper Cretaceous Naparima Hill mudstones and the principal reservoir rocks of the Cruse, Forest and Gros Morne deltaic sandstones.

Anticlinal and fault-related traps associated with petroleum occurrences in Trinidad began to form since the Miocene. Thermal history reconstructions indicate that oil generation and expulsion from source beds occurred over the last 8 m.y. in most parts of the NH-C/F/GH petroleum system.

Based on an average organic carbon content of 3.0 wt% and hydrogen index of 500 mg HC/g TOC the Naparima Hill source beds (type II kerogens) have a generative capacity of 76 to 127 x 10{6} bbls/cu km. Assuming 25% of the 500 m average thickness of the Naparima Hill Formation is net source rock, and that 67% of the present day area (14,000 sq km of the NH-C/F/GM petroleum system is effective source rock kitchen area, the Naparima Hill source beds are capable of yielding between 88 and 148 x 10{9} barrels of oil. This represents more than 4 times the volume of reservoired oil (producible and non-producible) calculated for the Trinidad area.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.