Modeling of anisotropy in fractured systems by high-resolution studies in the Paraná Basin, Brazil

Abstract

The geological interpretation of outcrops and their integration with new high-resolution geophysical data revealed the intensity, extension, and the geometry of a complex system of fractures that affected the Itararé Group of the Paraná Basin, of potential value for the development of models with application for hydrocarbon exploration. Sets of small-displacement faults and joints that developed in the thick sequences of periglacial sandstone, diamictite and shale beds of the Itararé Group were imaged using different tech-niques. The depositional architecture and the structural framework were interpreted from high-resolution seismic data, electrical and electromagnetic surveying, the construction of cross sections; stratigraphic archi-tectural analysis and structural mapping at semi detailed and detailed scales. The study area is situated in the central part of the Paraná Basin, in the proximity of the Vila Velha National Park.  The extent of the exposures, their lateral continuity and the conditions of the terrain, facilitated the geophysical imaging of sub-out-crop sections. The modeling and evaluation of the potential reservoirs was mainly based on the integration between the geometric model obtained from the depo-sitional characteristics, such as the internal and external geometry of the sandstone bodies, with those devel-oped from the structural analysis, in order to map polygonal systems of fractures cutting tabular and lenticular sandstone bodies.  The resultant geometry is represented by a reservoir system on the scale of tens to hundreds of meters where the anisotropy is complex and derived from faciological and structural controls. With the support of high-resolution imaging, associated with traditional analytical techniques of stratigraph-ic and structural analysis, it was possible to generate three-dimensional models of the analogue reservoir.