An Applied Sequence Stratigraphic Approach in Reservoirs Characterization, Eastern Venezuela: El Carito-El Furrial Fields

Integration of biostratigraphic, sedimentologic and petrophysic data from cores and well logs in reservoirs in El Carito-El Furrial Fields, Northern Monagas, Eastern Venezuelan Basin, allows to differentiate two sedimentary sequences ranging between the Upper Cretaceous and the Oligocene. The Maastrichtian-Paleocene sequence is divided into two sedimentary units (C and 1) both representing a south to north progradation from shallow marine to fluvial environments, within a large regressive cycle. The Middle Eocene to Middle-Late Oligocene sequence includes sedimentary units II and III. Unit II represents a large transgressive cycle of mostly inner neritic deposits with a condensed section at the base which changes laterally from glauconitic to lutitic facies to the south. Unit III grades transitionally from the inner neritic deposits of unit II to shallow marine deposits, and changes to inner neritic deposits again to the top. Unit III is interpreted as a large regressive -transgressive cycle. In all these sedimentary units, lithofacies association, paleoenvironments variation and definition of large cycles helped to define the parasequence stacking sets. The petrographic analysis points out that sandstones in unit C are basically subarcosic, while in units I, I and III are quartzitic. Additionally, sandstones in units C and II are very cementedmore » by quartz and carbonates respectively, showing chemical compaction, in contrast to units I and III where quartz dissolution is a porosity enhancing process. This indicates that sandstones in these units have the best porosity and permeability values, resulting in the best producing intervals in the study area.« less