Foz do Amazonas Basin

Characterization of Crude Oils and Source Rocks

GEOCHEMICAL SOLUTIONS INTERNATIONAL INC. (GSI) has conducted a geochemical study of crude oils and potential source rocks from the Foz do Amazonas basin of the equatorial margin of Brazil. This study was designed to identify and compare the petroleum systems that have contributed to accumulations in this important area and to evaluate the organic richness, hydrocarbon-generating potential, oil proneness, and thermal maturity level of all potential source rock intervals in order to assist exploration efforts in the less developed regions.

The Foz do Amazonas Basin is situated at the western portion of the Brazilian equatorial margin, alongside the coast of the Amapá and Para States. It occupies an area of approximately 261,170 km2, including the continental platform, slope and deepwater region, to the boundary between continental and oceanic crust. The basin includes the following geologic provinces: (1) Pará and Amapá Platforms (shallow basement), (2) Mexiana and Caciporé areas, and (3) Tertiary carbonate shelf and Amazonas Cone. Ninety-three (93) exploration wells have been drilled in the basin, 60 by Petrobras and 33 by companies within risk contracts. This exploration effort resulted in the discovery of two sub-commercial gas accumulations: Pirapema and the area of well APS-51A. Sub-commercial oil accumulations have been discovered in the Caciporé area and gas was found in the shallow area of the Amazon Cone.

Four (4) crude oils from this area have been analyzed using state-of-the-art oil fingerprinting techniques to evaluate the major factors governing oil quality and quantity including: (1) source facies, (2) thermal maturity, (3) distance of migration from source to trap, (4) extent and timing of biodegradation, and (5) degree of oil mixing.

A detailed evaluation of the hydrocarbon source potential of the Foz do Amazonas Basin has been accomplished by the evaluation of more than 2000 samples from 18 wells covering approximately 20,000 meters of section. This evaluation is based on Total Organic Carbon content (%TOC) and Rock-Eval pyrolysis data obtained from the analysis of samples representing the Tertiary and Upper Cretaceous post rift Pirarucu, Marajo, Amapá, and Limoeiro formations and the Middle Cretaceous rift Caciporé Formation. Selected well cuttings and/or core samples have been characterized based on detailed kerogen and/or bitumen analyses.

Crude oil and source rock analyses have been performed at BRI-DGSI laboratories in Houston. Results of the study are presented in both analytical and interpretive formats to insure that all findings are accessible to explorationists and research personnel. All geochemical data is provided in hard copy and in digital format in a database contained on CD, which includes a proprietary data browser to facilitate access. A synthesis and interpretation of all information is presented in a comprehensive final report including oil-oil and oil-source rock correlations, oil quality, hydrocarbon source potential, oil proneness and thermal maturity.