Porosity expresses the volume of fluid in a sedimentary rock, setting the storage capacity of fluid and its quality as a reservoir rock. The determination of realistic porosity values has a direct impact on the calculation of water saturation and, consequently, the evaluation of hydrocarbon reserves. A popular method for porosity calculation uses the combination of density and neutron porosity logs, producing porosity values corrected for shale content. The points of same depth of those logs represented as coordinates in a graph exhibit characteristic angular pattern, which can be conveniently interpreted by a intelligent algorithm, as the competitive angular neural network, which can recognize those angular patters producing the log zonation and enabling porosity calculation using convenient values of physical properties for each lithology. The evaluation of this methodology was performed using porosity logs and core analysis results from boreholes drilled in Namorado Field, Campos Basin, Brazil.
|
