High-resolution sequence stratigraphy applied for the improvement of hydrocarbon production and reserves: A case study in Cretaceous fluvial deposits of the Potiguar basin, northeast Brazil

Abstract

High-resolution sequence stratigraphy (HRSS) was applied to Cretaceous fluvial deposits of Açu Formation, the principal oil-bearing unit of the Potiguar Basin, aiming to help reservoir management. Facies associations and stratigraphic surfaces were interpreted from an integrated analysis based on rock cores, ichnological, well logs, and production data. Overbank strata envelop transgressive meandering fluvial deposits and promote vertical fluid-flow barriers between reservoirs, thus characterizing zone boundaries. Zone boundaries consist of high-frequency subaerial unconformities placed at the top of paleosol levels correlated throughout the study area. The correlation allowed identifying nine high-frequency sequences and established the reservoir zonation that replaced the former four lithostratigraphic zones. The chronostratigraphic framework supports a more detailed and predictive 3D numerical geological model that is much more representative of the meandering fluvial system and its heterogeneities. Furthermore, the high-resolution stratigraphic reservoir zonation helped revitalize production by identifying intervals with high water cut, which hinder oil production, and oil-saturated intervals that were never opened to production. This case study demonstrates that the application of HRSS methodology is fundamental to improve oil reserves, production, and the final recovery factor in the Potiguar Basin oil fields and analogous situation worldwide.