ABSTRACT: Paleocene Deltaic Sandstones of the Venezuelan Andean Foothills: Potential Hydrocarbon Reservoirs

Xiomara Marquez

The sedimentary sections of the Paleocene Orocue Group cropping out in the Venezuelan Andean Foothills were studied with the main purpose of identifying the presence of potential oil reservoirs.

Using the facies analysis technique eleven sedimentary facies were defined: four sandstone facies (S, S3, S2, S11), one siltstone facies (St), two shale facies (Lu1, Lu2), three sandstone/shale interbedded facies (I1, I2, I3), and one coal facies (Cr).

The vertical and lateral facies association allowed the recognition of two sedimentary units, designated I and II. Unit I indicates sedimentation in a lower delta plain and unit II suggests sedimentation in an upper delta plain. The vertical variations of these sedimentary units represent a switching deltaic lobe in a progradational event, that is to say, a regressive sequence.

The S3 sandstone seems to be the best rock type as an oil reservoir. These sandstones are very continuous laterally and occur repeatedly in the sequence. The porosity values are up to 25% and the pores are well interconnected. Locally, facies S3 shows a high oil-residue content.

This study concludes that S3 sandstones represent the best rock type for possible hydrocarbon reservoirs.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990