Modelos virtuais de afloramento aplicados à estratigrafia de sequências e modelagem de análogos de reservatório fluvial na Bacia Lusitânica

Abstract

Sedimentary deposits outcrops analogous to oil and natural gas reservoirs have been increasingly used by the oil industry to help determine the spatial and temporal distribution parameters of the reservoirs and their heterogeneities. These outcrops provide relevant geological information for understanding the characteristics of subsurface rocks. Sequence stratigraphy is a tool that allows zoning both analogous outcrops and natural reservoirs through the definition of sedimentary basin filling patterns. The determination of the filling patterns in similar outcrops allows the characterization and prediction of the quality of subsurface reservoirs. Although extremely relevant for the oil industry, the study of outcrops is still carried out using 1D and 2D analog techniques. Virtual Outcrop Models (MVA) are photorealistic 3D digital representations that transform nature's forms into three-dimensional computer models. With MVA, reservoir models can be created in a manner similar to the workflow used in industry, with geological and stratigraphic information obtained from digital data. This work has the objective of analyzing the heterogeneities of rocks deposited in river systems and the construction of reservoir models through sequence stratigraphy and MVA. The study area comprises a cluster of cliffs, about 30m high and a total of 1.8km long. The region is located to the west of Portugal and comprises rocks of the Lourinhã Formation, Upper Jurassic, of the Lusitanian Basin. Through this work, eight photofacies and three photofacies associations were delineated, characterizing the architectural elements of fluvial reservoirs. From the faciological interpretation it’s possible to observe different stacking patterns and define high level, low level and transgressive system tracts. Four depositional sequences were then delimited, and the presence of higher frequency sequences associated with them was suggested. From the photofacies associations were also constructed geocellular volumes representing the geometry of fluvial channels, floodplains and deposits of crevasse splay. These bodies allowed the representation of the internal variations of the quality of a hydrocarbon reservoir in fluvial systems, and the analysis of the relation between the quality of the reservoir with different systems tracts.