Modelamento da permissividade dielétrica de rochas saturadas de óleo e água e suas aplicações em perfilagem de poço

Abstract

The electromagnetic propagation tool (EPT) provides the propagation time (Tpl) and the attenuation (A) of an electromagnetic wave propagating in a lossy medium. These EPT responses depend on the dielectric permittivity of the medium. There are several models and mixing equations concerning the dielectric permittivity of reservoir rocks that can be used in the interpretation of the high frequency tool. However, the mixing equations do not take into account the distribution and the geometry of the pore space, and these parameters are essential to obtaining dielectric responses approximating a true rock. A model based on the parameters described above was selected and this was applied to dielectric data available in the literature. A good agreement was reached between the theoretical curves and experimental data, confirming that the distribution and geometry of the pore space must be considered in the development of a realistic model. Aspect ratio distribution functions of the pores were also obtained, which were used for generating several curves relating the EPT responses to various oil/gas saturations. These curves were applied to the log analysis. The selected model fit the dielectric data available in the literature reasonably well, thus, making it suitable for application to experimental data of rock from Brazilian producing fields for the interpretation of the EPT in these fields.