The Upper Cretaceous of Trinidad, is there an Unconventional Source Rock Play?

Abstract

Abstract To date Trinidad has produced close to three billion barrels of oil from onshore and offshore fields. Formations penetrated range in age from the Lower Cretaceous to the Pleistocene. Ninety three wells have been drilled to the Cretaceous with varying degrees of success, these wells have identified whether source rock facies are present or absent across the island. Based on well and outcrop data, the Upper Cretaceous interval is shale dominated with occasional turbidite sandstone reservoirs and a siliceous mudstone locally known as "Argilline". Geochemical research by Kuarsingh (1986), Rodrigues (1987, 1988, 1993), Talukdar et al (1990), Requejo (1991), Persad et al (1993), Requejo et al (1994), Baseline/DGSI (2004) indicated that most of the hydrocarbons in Trinidad have been sourced from Type II kerogens contained in Cenomanian-Santonian and Aptian aged marine shales of the Naparima Hill and Gautier Formations respectively, Maastrichtian and Tertiary sediments are dominated by mainly woody and coaly kerogens. Total Organic Contents range from 0.1 to +\- 9%. Rodrigues (1989) mapped the distribution of geothermal gradients identifying hot and cold areas, this data has implications for petroleum systems modeling, especially for the timing and top of the oil generating window. Royalty Lease Evaluation (RLE) analysis of oils produced from Upper Cretaceous sandstone and naturally fractured intervals (Specific gravity / API, viscosity, % Sulphur, % of products by distillation) give clues to the origin and history of these oils. Integration of these results and data can result in identification of areas with potentials unconventional source rock plays.