Luiz Antonio Trindade¹, Lorenz Schwark²

(1) PETROBRAS/CENPES, Rio de Janeiro, Brazil
(2) University of Cologne, Cologne, Germany

ABSTRACT: Geochemical Effects of Secondary Migration within the Candeias - Agua Grande Petroleum System along the Mata Catu Fault Trend, Reconcavo Basin, Brazil

The Reconcavo Basin was investigated for migration processes in a lacustrine sedimentary basin. The oils are generated in the Cretaceous Candeias Formation and migrate into age-equivalent reservoirs of the Sergi- and Agua Grande-Formations. Sandstones of the Agua Grande Fm. preferentially serve as carrier beds in this tectonically highly structured rift basin, which is separated into a southern and a central compartment by the Mata Catu fault system. The role of this structural element in regional migration processes was evaluated by analyzing residual oils and DST oils from the Agua Grande Fm. areas east and west of the fault. Residual oils were analyzed for intra-well and inter-well compositional difference. For several wells significant intra-well variability was noted indicating strong reservoir or carrier bed compartmentalization. This intra-well variability is recognized in biomarker maturity ratios and in carbazole migration indicators. This mixing of oils of different origin within the carrier bed is mainly caused by the convergence of individual migration routes originating from different source areas. Single-well averaged biomarker maturity and geotracer ratios allow the definition of a separate migration route in the southern compartment of the basin, which is de-coupled from the main migration trend in the central compartment. Convergence of migration routes parallel to and perpendicular to the Mata Catu Fault system, but not across the fault, could also be detected based on inter-well carbazole geotracer and biomarker maturity data. This study provided new insights into mechanisms of petroleum migration and proves the general applicability of carbazole geotracers to lacustrine basins.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado