Facies Analysis and Seismic Stratigraphic Interpretation of Cored Paleocene Carbonate Sequence in Block III, Lake Maracaibo, Venezuela

Argenis Rodriguez, Marcos Rampazzo

The cored Paleocene carbonate sequence found in wells VLC-812 and VLC-950, together with ditch samples from wells VLC-750 and VLC-693 in Block III, Lake Maracaibo, present a recurrent lithology which can be represented in seven sedimentary facies groups. The recognized facies range from a mollusk-rudstone to a sandy oolitic grainstone. The most important facies is a highly porous, oil-bearing grainstone.

The above-mentioned facies were grouped into a facies assemblage which was then interpreted in terms of its depositional environment. A genetic facies model was constructed in order to explain lateral and vertical facies changes and for regional prediction purposes. This facies model predicts a commercial porosity development in a preferred orientation in the Block III area.

A seismic-stratigraphic interpretation, which took into account the sedimentary facies model, documents a paleoshoreline at the time of the oolitic grainstone sedimentation. This finding confirmed the favorable prospective zones proposed by the sedimentary facies model for better porosity development in the carbonate sequence. This sedimentary facies/seismic-stratigraphic model can form the basis for hydrocarbon exploitation and exploration for carbonate rocks with similar geological characteristics and most importantly can be used where there are widely spaced wells.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.