Tectonic synthesis of the deepwater Lamprea thrust and fold belt, offshore Burgos Basin, western Gulf of Mexico

Abstract

Hydrocarbon exploration in the deepwater Western Gulf of Mexico, offshore Burgos Basin, Tamaulipas, Mexico, has been mainly focused in the NE-SW structural trend of the Perdido fold belt. Recent exploration efforts have targeted the adjacent Lamprea thrust and fold belt, located south of the Perdido trend. Deepwater channel and lobe systems constitute the Oligocene plays in the underexplored Lamprea trend. The objective of this research is to understand the tectonic evolution of the Lamprea thrust and fold belt, as recent oil and gas discoveries proved the presence of economic hydrocarbon accumulations. The Lamprea thrust and fold belt is located at the toe of a regional, gravity-driven linked system in the Western Gulf of Mexico. Middle Eocene to Late Oligocene strata were folded and thrusted during a Late Oligocene to Early Miocene compressional episode. A wide variety of thin-skinned NW-SE trending structures, such as imbricate systems, pop-up anticlines, and shear fault propagation folds characterizes the structural style. This compressional province detaches on an overpressurized Middle Eocene shale-system. Seismic velocity analysis suggests that variable degrees of overpressure affected the mechanical properties of the shale-based detachment, exerting a first order control on the development of different structural styles. Sequential restorations suggest that the Lamprea thrust and fold belt initiated as a series of N-S shale-cored folds. Subsequent shortening was accommodated by imbrication to the West of the shale-cored folds. Precursor folds evolved into breakthrough shear fault propagation folds in the East, and pop-up structures in the central area. The Lamprea thrust and fold belt followed an out-of-sequence propagation style, and most of the thrusts propagated along strike in a N-S direction. Shortening rates decreased from 4.75 mm/y in the South to 4.09 mm/y in the North. Restoration sensitivity analysis of seismic-derived interpretation error, and forward and inverse numerical modeling decreased uncertainty while providing viable restored cross-sections. The combination of two different restoration methods provided a more compelling kinematic model, including a thrust propagation sequence. This approach can be used in analogous structural areas. The top Late Oligocene pre-kinematic sequence was severely affected by subaqueous erosion caused by bottom currents that removed as much as 83 km3 of rock volume. Early Miocene increase of oceanographic current velocities in the Gulf of Mexico due to a progressive termination of global equatorial flow is considered the cause of this erosional episode. The main results of this research include (1) more precise timing of faulting, and (2) paleobathymetry reconstructions. The results can be directly integrated into petroleum system analysis to assess hydrocarbon migration and charge, and evaluate the distribution of structurally controlled deepwater reservoirs.