Caracterização tectonoestrutural do Campo de Xaréu (Sub-Bacia de Mundaú, Bacia do Ceará -NE do Brasil): abordagem multiescala e pluriferramental

Abstract

The Xaréu Oil Field, located in the centralsouthern portion of Mundaú Sub-Basin (eastern Ceará Basin), is characterized by an array of NW-trending and NE-dipping normal faults. Those faults constitute an extensional listric fan rooted along a detachment surface which corresponds to the Mundaú Fault, located at the southwestern border of Mundaú Sub-Basin. The main carbonatic unit in the oil field, the Trairí Member (Paracuru Formation, Early Aptian to Early Albian), contains the largest oil volume in the area, which is concentrated in structurally controlled accumulations. The structural analysis carried out by drill cores and image profiles studies of the Trairí Member identified two generations of meso- to microscale structures: (i) the earliest D1 structures partially present a typical hydroplastic character, characterized by bedding-parallel and oblique shear zones, besides late brittle structures; and (ii) the D2 structures present a typical brittle character, encompassing normal faults and recrystallized argillaceous slickenlines. Although the macrofaults observed in the Xaréu Oil Field (and, consequently, in the Mundaú Sub-Basin) are classically referred as dip-slip normal faults, the kinematic analysis of the D1 structures indicates that such faults are, actually, oblique-slip structures, presenting tectonic transport towards ENE. Those oblique movements might be the response to the onset of a transtractive context in the Mundaú Sub-Basin, which is, ultimately, the result of a strike-slip tectonics that took place during the origin of the Atlantic Equatorial Margin.