3D outcrop geologic modeling applied to test the role of brittle structures on permoporosity of poorly lithified reservoirs

Poorly lithified siliciclastic rocks correspond to important post-salt reservoirs in the Southeastern Brazilian Margin offshore basins. These reservoirs present challenges regarding the prediction of the hydraulic behavior of faults due to low cohesion leading to diffuse brittle deformation. To improve the understanding of the deformation influence on the reservoir quality of these rocks, this paper presents a 3D modeling method based on an outcrop analog composed of Paleogene poorly lithified fluvial siliciclastic deposits in the Volta Redonda Basin (Continental Rift of Southeastern Brazil). A database was collected containing a 3D digital terrain model of the outcrop, a 1:50-scale geological section, permeability and porosity measurements, and lithological and sonic log from a well drilled upon the outcrop to the basement. Two models were built: one using traditional methods for industry where properties were uniformly distributed throughout the grid and a second model where sectors were delimited and populated with data from deformed rocks, highlighting the impact of tectonic structures (faults and deformation bands) on fluid flow, reducing the permeability by one order of magnitude, and increasing the flow time between wells by more than 10%. This study contributes to improving reservoir modeling accuracy, enhancing the understanding of fluid flow behavior in complex, deformed, poorly lithified rocks.

KEYWORDS:
poorly lithified sandstone; analog reservoir modeling; digital outcrop; fractured reservoir