ORGANIC GEOCHEMISTRY AND PETROLEUM POTENTIAL OF JAMAICA

Abstract

Eleven wells were drilled in Jamaican territory over a 27–year period commencing in 1955: all were abandoned as dry. This study evaluates the island's petroleum potential in the light of new data on the source-rock quality of the shales penetrated, and on reservoir properties of sandstones and limestones interbedded with these shales. Altogether. 270 representative shales and mudstones were sampled from the Cretaceous Windsor, Hanover and Sunderland Formations, and from the Eocene Richmond and Chapelton Formations. and subjected to standard organic-geochemical analyses. Data on organic matter quantity, type and maturity indicate good potential for oil generation in the Chapelton Formation. The other formations analysed have < 1.0% total organic carbon. comprising woody and coaly kerogens, with no potential for oil generation. Modal compositions of detrital grains were determined on sandstones sampled for reservoir quality evaluation from four formations. Provenance studies indicate derivation from a magmatic-arc source, with volcanic lithic fragments and feldspars being the dominant constituents. This unstable mineralogy, combined with rapid sedimentation and location of sedimentary basins close to source areas, implies low porosity and permeability in these sandstones. Other considerations of trap availability, presence and extent of cap rocks. and the likelihood of any petroleum generated being preserved in view of Jamaica's active tectonic history since the Middle Miocene, suggest that conditions for the generation. accumulation and preservation of commercial deposits of petroleum probably may not have existed here.