Marcelo Kulevicz Bartoszeck

Bayesian assessment of favorability for oil and gas prospects over the Recôncavo basin, Brazil

This paper presents a Bayesian approach to evaluate remaining potential of oil and gas in the Reconcavo basin, Brazil. The purpose is to test a new Bayesian weighting methodology and quantify the favorability for the existence of new fields in the basin. The methodology implies organization of petroleum system data in descriptive models with which results from drilling are manipulated statistically, including analysis of geologic factors that are spatially correlated with both producing and dry areas. In the first stage of modeling, the essential elements (reservoir, seal, and overburden rocks) that control the fundamental processes of generation, expulsion, migration, and entrapment of petroleum accumulation are defined throughout integration of previously published data. The petroleum accumulation models of Reconcavo basin comprise generation from Neocomian shale rocks of the Gomo Member (Candeias Formation), vertical migration along extensional and transfer faults, and accumulation in tilted horsts with Upper Jurassic prerift reservoirs (Sergi Formation) or in Neocomian turbidite reservoirs in stratigraphic/combined traps (Candeias and Marfim formations). Probability distributions and weights are then calculated through Boolean operations among producing and dry areas and each diagnostic criterion evaluated through descriptive models such as source bed thickness, onset of organic maturation, presence or absence of faults and structural blocks, reservoir thickness, and seal distribution. The final stage of evaluation consists of spatial integration of raster maps that are weighted according to their necessity and sufficiency conditions, the results being presented as favorability maps. The characterization of favorable areas and their comparison with known fields suggest that such a Bayesian approach can contribute to the understanding of petroleum systems as a practical approach that considers the spatial nature of exploration variables.

GeoGrid3D: a program to insert faults in 3D geological model for fluid simulation

This Paper show an application of geological and geophysical data integration into a flow simulation 3D model. A free program was used to do this flow simulation (Boast from United State Department of Energy). But to use this free simulator, a new program was build (GeoGrid3D). This program came with a special feature that can insert faults into the 3D model and also have other functions to get specific data codifications for Boast recognition. Outcrops from Permian sedimentary rocks and shallow seismic are used as data for this reservoir framework 3D model. Petrophysical properties were distributed using rules from interpretation of correlation done with facies and stratigraphic analysis of the outcrops. The main petrophysical model was built, and to test GeoGrid3D functions, other tree tectonic situations of faults comportament are also generated. The gas saturation, after flow simulation, confirms that changing faults permeabilities inside the reservoir will change gas production in rocks like this model.