Mann, Paul¹ and Pierce, Stephen²

¹Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Bldg 96, 10100 Burnet Road, Austin, Texas 78758-4445, paulm@ig.utexas.edu, office phone: 512-471-0452 office fax: 512-471-8844
²P. O. Box 70, Palmer, Texas 75152, pierce@ectisp.net

Natural oil seeps and small-production oilfields in south-central Hispaniola are regionally isolated from much larger and older hydrocarbon provinces in the circum-Gulf of Mexico and northern South America. In this talk, we evaluate the tectonic, stratigraphic, and structural setting of these hydrocarbon occurrences in this era of rapidly escalating energy costs. GPS studies have shown that the area of maximum oblique plate convergence between the Caribbean and North America plates is centered on the topographically elevated and seismogenic island of Hispaniola. The zone of oblique convergence includes the Bahamas Platform, Cretaceous and Paleogene arc rocks in Hispaniola, and the Cretaceous Caribbean oceanic plateau. The onset of oblique collision occurred in late Miocene time.

Since 1904, hydrocarbon exploration in west-central Hispaniola has been concentrated in the elongate, northwest- to west-northwest-trending, thrust- and strike-slip-fault-bounded Cibao, San Juan-Azua, and Enriquillo basins. Previous drilling has largely focussed on drilling surface anticlines formed by Late Miocene and younger oblique plate convergence. Analyses of Cretaceous to Neogene rocks in the Dominican Republic shows that most rocks contain poor to marginal total organic carbon values and low source rock potential. In the San Juan, Azua, and Enriquillo basins, the middle Miocene Sombrerito Formation exhibits TOC values within the lower end of petroleum generative capacity. Five Neogene stratigraphic units are summarized in this talk because of their close association with known hydrocarbon production areas and seeps.

The future promise of Dominican exploration lies offshore in the Ocoa and offshore San Pedro basins both of which have been been mapped using widely spaced seismic lines but no offshore wells have been drilled in either area (three wells were drilled in the onshore San Pedro basin in the 1970s). Potential reservoirs in these basins include quartz-rich sand eroded from the plutonic terrane of the Cordillera Central and carbonates formed on highs and in coastal areas. Source rocks remain problematic as seen in our study of the onshore basins.