干旱区生态环境知识资源中心

This paper deals with the study of source rock potential and its depositional environment. These strata belong to Pojuca Formation and occur in syn-rift sequence of the Early Cretaceous age (Hauterivian-Barremian) in the region of Aramari, a little-explored area of the northwestern Reconcavo Basin. The potential generator of these sediments was evaluated based on studies of palynofacies, Total Organic Carbon (TOC) analysis and Rock-Eval pyrolysis. For the evaluation of the maturation thermal of organic matter of the sediments was used the Spore Coloration Index (SCI); and the palynological study was used to identify the paleoenvironment of these strata. By integration of data from "Rock-Eval" pyrolysis and palynofacies it was possible to identify the prevalence of type II and III kerogen, with varying degrees of quality, allowing for individualization of three palynofacies. The material has predominance of amorphous organic matter of lacustrine origin, with TOC data ranging from 0.95% to 4.71%. The organic matter is a great potential hydrocarbon generator, indicated by S2 values that reach 26.33 mgHC/g rock. SCI values between 4.5-5.0 corresponding to 0.5 reflective of vitrinite (% Ro) demonstrated that the studied section is entering the maturation window. With the data acquired through palynofacies analysis and palynological associations, it can be inferred that a continental deposition environment (deltaic lake) characterizes the sedimentation of the Pojuca Formation with the presence of higrophytic and xerophytic elements, indicating that the vegetation developed in an arid and dry paleoclimate with wet niches locally and latitude next to the present. The data show that the studied area is placed in anoxic conditions containing good quality kerogen and suitable for the generation of hydrocarbons.