Kinematic evolution and fracture prediction of the Valle Morado structure inferred from 3-D seismic data, Salta Province, northwest Argentina

The Valle Morado structure, located in northwest Argentina, is an approximately 7-km-long and 4-km-wide north-northeast-south-southwest-trending anticline cut by faults that involve Paleozoic basement and Mesozoic-Cenozoic sedimentary cover. Geological interpretation of a three-dimensional seismic survey that covers the structure, plus a well and two-dimensional regional-scale seismic lines, indicates that the Valle Morado is an Andean pop-up structure formed by foreland-directed faults, resulting from reverse reactivation of Cretaceous extensional faults dipping westward, and newly formed hinterland-directed reverse faults dipping eastward. The orientation of the preexisting extensional faults is nearly perpendicular to the Andean tectonic transport direction in the northern part of the structure and oblique toward the south, resulting in almost pure contraction in the north and transpression southward. Curvature analysis performed on two interpreted reservoir seismic horizons suggests that the maximum density of open fractures is likely to occur along the anticline axis in the northern portion of the fold and along the northeast-southwest-striking foreland-directed, reactivated faults to the south. The direction of the open fractures interpreted from ultrasonic borehole image data along the well coincide with that of the open fractures predicted from the curvature analysis.