Hydrocarbon potential of the northeastern Caribbean based on integration of sediment thickness and source rock maturity data

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2015-08

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Abstract

Over 72 exploration wells have been drilled on the Caribbean islands of Hispaniola and Puerto over the past century, but with no commercial success. A key question is whether these large Caribbean oceanic islands have experienced sufficient subsidence and burial for any potential source rocks to reach maturity and produce commercial hydrocarbons. Well data and seismic interpretations from previous studies were compiled into a depth to basement and sediment thickness map for Hispaniola, Puerto Rico, and their offshore areas. This map shows the highest sedimentary thicknesses for the nine thickest basins: the onland Enriquillo / Cul-de-Sac basin (6.3 km), San Juan / Plateau Central basin (5 km), Azua basin (2.8 km), Cibao basin (5 km), North Coast basin (2.5 km), and South Coast basin (1.3 km), and the offshore Haiti sub-basin (3.7 km), Hispaniola basin (3.5 km), and San Pedro basin (3 km). One-dimensional modeling for six onland basins shows that only the Azua basin of the south-central Dominican Republic has reached sufficient maturity to place potential source rocks into the oil window. Maturity in this basin, likely related to localized heating from Plio-Pleistocene shallow intrusives, is supported by the presence of natural oil seeps and very limited production in the basin from shallow wells. Limited data indicate that the Cibao basin of the northern Dominican Republic also reached the oil window. Geochemical analysis of the Enriquillo basin indicates lower heat flow in the basin, resulting in immaturity of well samples. The North and South Coast basins of Puerto Rico are immature due to very low sedimentary thickness. Geochemical analytical results have shown that most organic matter from well samples in these basins consists of type III gas-prone kerogen, and that all well samples are immature. This study has shown that commercial hydrocarbons are possible in the deeper basins - Azua basin, San Juan - Plateau Central basin, and Cibao basin of Hispaniola - but unlikely in shallower basins. Biogenic gas is possible at shallower levels in several basins and in offshore areas.

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Keywords

Northeastern, Caribbean, Source rocks, Maturity, Geochemistry, Burial history, Basin models, Vitrinite reflectance, RockEval

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