Summary

This paper presents a detailed description and interpretation of the stratigraphy, sandbody geometry and major reservoir heterogeneities of three contrasting styles of Upper Oligocene to Lower Miocene turbidite reservoirs, which comprise three giant oil fields (total reserves of 3.2 billion bbl) in deep water (300 - 1300 m) areas of Campos Basin, Brazil. Three case histories of sand-rich, poorly consolidated turbidites are characterized with 3D seismic, well log, core, and production data. They include (1) channel complexes, (2) thicker, amalgamated lobes, and (3) thinner, amalgamated lobes heavily dissected by channels. These reservoirs show high porosities and permeabilities, which average values typically exceed 26 % and 800 mD, respectively. Major types of reservoir heterogeneities include (1) complex external geometry (particularly in the case of channel complexes and lobes heavily dissected by channels), (2) widespread or discontinuous, mudstones and marls interbedded with sandy and conglomeratic reservoirs, (3) discontinuous calcite concretions, and horizons of calcite-cemented, intraclastic sandstones and conglomerates, and (4) variations in petrophysical properties related to grain size and sorting distribution.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas