Geochemical characterization of Jurassic source rock from Cuba: 1. Cifuentes Formation in onshore Via Blanca - Boca de Jaruco oils fields

Abstract

The present study investigates the principal characteristics of organic matter contained in sedimentary rocks of the Jurassic Cifuentes Formation, Cuba and to assess its hydrocarbon generative potential. The Cifuentes Formation is part of the Placetas Tectono-Stratigrafic Unit (TSU) of the Northern Cuba Petroleum Province and is considered the principal hydrocarbon source rock of the area. A total of 37 core samples collected from 10 petroleum onshore exploration wells were analyzed ranging in depth from 1478 to 4037 m. Analytical methods included total organic carbon (TOC) determinations, Rock Eval, optical analyses and gas chromatography and mass spectrometry (GC-MS). Results indicate that these rocks have organic carbon contents ranging from 0.52 wt% to 9.91 wt%. The average hydrocarbon generation potential as determined by Rock-Eval pyrolysis (S2) is between 0.34-83.37 mg HC/g of rock suggesting a fair to good hydrocarbon generation potential for many samples. Hydrogen Indices (HI) and Oxygen Indices (OI) suggest kerogen types ranging from I to II and II/III. Optical analyses based on palynofacies concepts indicate predominance of amorphous organic matter (AOM). Based on biomarker distribution depositional environments is range from anoxic/hypersaline to normal saline. Maturity parameter such as Tmax ( C), vitrinite reflectance (Rrandom %), spore coloration index (SCI) and biomarker ratios suggest the organic matter is immature to marginally mature.