Evaluation of low-resistivity argillaceous reservoirs of the Alagamar Formatlon, Ubarana Field - RN

Abstract

Based on the technical bibliography and on the study of the arrangement of c1ay minerals within reservoir rock pores, a new model was devised for quantitative evaluation of argillaceous sandstones. This model takes into account not only the electrolytic conductivity of the rock but also two other conductivities - one is the result of the effective contribution of the surficial conductance of the c1ay minerals, which increases or decreases as a function of the cation-exchange capacity of these c/ay minerals, while the other, independent and parallel, derives from the conductance that develops in a continuous microporous network which the c/ay minerals from over the framework of the rock. A comparison of the proposed model with the principal equations and models found in the specialized bibliography yielded good correlations, especial/y with the traditional Waxman & Smits equation. The proposed model displeys theoretical and practical consistency, and in the particular case or the sandstones of the Alagamar formation, Ubarana field, it has proved more coherent with the production history of studied wells than have the other equations tested.