EVALUATION OF THE STRESS STATE AROUND BOREHOLES USING WELL LOG DATA: A CASE STUDY IN THE SERGIPE-ALAGOAS BASIN, BRAZIL

Abstract

The oil industry has been investing heavily in studies focused on secondary recovery methods. In this context, water injection represents one of the leading methods used to obtain an increase in recovery factor. Studies to determine geomechanical parameters of rocks through the application of Zoback's equations (Zoback, 2007) using only well logging data are sparse. This work studies the variations of the in-situ stress state around the injector well in a reservoir through the application Zoback’s equations aiming to identify the maximum injection pressure limit to prevent rock fracturing. For the study, the in-situ stresses of the rock were determined using well log data acquired from drillings in a basing located in the Brazilian northeast. The study also considers the Mohr-Coulomb rupture criterion in the determination of the safe region. The results obtained by Mohr-Coulomb rupture criterion were validated with the absorption pressure values obtained with direct data of Leak Off Test (LOT) done in the wells. From the results obtained, it was possible to verify that the calculated values overestimated rupture pressures presenting an average relative error of 7.87%. Furthermore, the stress regime obtained for the Sergipe-Alagoas basin is agreement with other studies found in the literature.