Análise petrofísica e petrográfica de padrões internacionais de arenitos e carbonatos.

Abstract

The wide use of seismic prospecting method in the oil industry to generate images of geological structures that are found in subsurface and to the monitoring of petroleum reservoirs makes it essential to the knowledge of the petrophysical properties and the factors that affect them. In this context, this research aims to carry out the petrophysical and petrographical study of 30 samples of sedimentary rocks (sandstones and limestones) from American formations, considered standards in the industry. Petrophysical characterization tests were carried out by conventional laboratory methods, empirical-through fluid-replacement models and simulations by computer models, using the software Avizo Fire 8.1 and COMSOL Multiphysics 5.1, as well as the compositional analysis from the x-ray diffractometry and thin sections description in optical microscope. The petrophysical tests were performed under different conditions of pressure and fluid saturation. The petrophysical properties were influenced by several parameters, which differ according to the lithological rock type. The saturation of rocks not reached 90%, being much lower for dolomitic matrix rocks when saturated with oil, possibly due to their water wettability. Fluid saturation influences definitely in elastic properties of rocks in both methods studied. When saturated with oil most of the samples show higher compressional velocities as compared to other conditions of saturation (dry or saturated with water). The models of Gassmann and Brown & Korringa were more representative for the compressionais waves, being efficient in some cases also for the shear ones. Biot model proved to be more efficient for shear waves, especially in sandstones. The computational method proved effective as the compressional velocity, at least for one of the receivers, approaches or matches the value measured in the laboratory. The results obtained show that the set of samples studied presents good potential for reservoir. The mineralogical composition by DRX presented a good fit with the grain density measured conventionally.