Estado actual de esfuerzos en Béticas y Alborán a partir del análisis de “breakouts”

Abstract

Logging data from several onshore and offshore deep wells located at the South-Iberian Margin were selected to perform breakout analysis. Every data used to determine the orientation of breakouts come from magnetically oriented four-arm caliper which is part of the dipmeter logging tool. Most of the wells were drilled through Plio-Quaternary and late Miocene sediments, in cases reaching the metamorphic basement. Breakouts zones have been recognized in 6 wells; in depths up to 3000 m. Mean orientation and standard deviation of breakouts at each well have been used to assess the borehole quality following ranking criteria of the World Stress Map (WSM). From the well data set analyzed, three wells are considered as reliable stress indicators to characterize the present-day stress field throughout the margin (Andalucía A-1, Andalucía G-1, and Bética 18-1). The rest must be interpreted with caution because of the sparse number of breakouts. Stress inversion performed in these wells evidences that maximum horizontal stress (SHmax) tend to parallel coast strike, resulting in a roughly E-W orientation along the northern margin of the Alboran Sea