Contemporary stress orientations in the Andean retroarc between 34°S and 39°S from borehole breakout analysis

Abstract

In this paper we present the results of the analysis of borehole breakouts from 115 wells drilled within Neuquén Basin in the Andean retroarc between 34° and 39°S (Argentina). The first-order present-day stress orientation in the Andean retroarc is expected to be mainly controlled by the plate boundary forces (azimuth 80°) and the topographic forces (E-W). The obtained maximum horizontal stress (SHmax) has a preferred trend with a resultant direction of azimuth 88.7° and a 95% confidence interval of 13.3° consistent with the expected trend. The horizontal stress trajectory map achieved for this region shows that the SHmax along the study area is not completely uniform. To the north of Colorado River, the SHmax shows an ESE tendency interpreted as significant influenced by the topographic forces. To the south of Colorado River, SHmax has an ENE trend similar to the expected based on plate boundary forces. To the southeast of the region, a NE direction was found, probably showing a basement structural control in the stress field geometry. The stress orientations obtained for the whole region show that plate boundary forces, drag basal, and topographic forces are strongly controlling the stress direction distribution.