Abstract:
In order to quantify the petroleum potential of the northwest offshore zone of Cuba, the source-rock potential has been estimated as well as the maturation level and the possible migration pathways. An interpretation of new seismic lines acquired by Compagnie Generale de Geophysique (CGG) has been coupled with field work and well data synthesis. To better characterize the source rocks, Institut Francais du Petrole's (IFP) Rock-Eval 6 apparatus was run on about 300 samples, and the analyses have been added to the existing IFP and Cuba Petroleo's (CUPET) databases. Specific kinetic parameters have been computed and modeling has been performed using both 1-D and 2-D models of maturation and migration processes. Several source-rock intervals could be defined in the area: (1) synrift clastic Jurassic, (2) deep-basin Upper Jurassic and Lower Cretaceous carbonate formations, and (3) Middle Cretaceous facies, also carbonates. One of the main results of this study is evidence of the potential of a deep petroleum system in the siliciclastic rift sequence. Shales from a Middle Jurassic synrift section initially appear to have good potential, depending on the maturity of the offshore zone, sufficient depth of the initial synrift half grabens, and the postrift carbonates being several kilometers thick. Upper Jurassic/Lower Cretaceous source rocks associated with deep-water carbonates are largely immature in the deep offshore (Northwest Cuba) except near the coast, where maturity level is high mainly because of thrusting and/or thickness of the foreland deposits. The third source rock is middle Cretaceous (Aptian/Cenomanian), recognized in onshore Cuba as well as in an Ocean Drilling Project (ODP) well; it appears to be an excellent source rock. In the offshore zone, these source rocks are mature only when buried under the flexural basin. The migration pathway under Jurassic evaporites and the middle Cretaceous unconformity (MCU) may lead to long northward as well as lateral migration from the kitchens. In the vicinity of the island of Cuba, in the first 100-150 km northward from the coast, various petroleum systems are active, and the high quality of numerous Cretaceous source-rock intervals show promise for hydrocarbon exploration in the area.