TAMING JUNGLE GEOLOGY WITH XTREME SEISMIC: AN INTEGRATED STUDY OF THE AMATIQUE BASIN, GUATEMALA

The Cretaceous carbonate rocks of Mexican Yucatan hold the largest conventional oil reserves in the Western Hemisphere and oil and gas companies have sought similar-sized fields in the Guatemalan and Belizean portions of the Yucatan. Southern Belize and Eastern Guatemala share similar tectonic origins with the prolific Reforma area and the Peten Basin. Upper Cretaceous to Paleocene compression deformed the oil-producing Lower Cretaceous carbonates into foreland basins and associated structures. Subsequently, Paleocene to Holocene left-slip wrenching has altered old structures and created new structures. Active surface oil seeps (“Beverly Hillbilly-like”) are often associated with these structures.

Integrating surface geologic, surface geochemical and seismic data created a consistent picture from otherwise bewildering data sets. A regional 2D seismic survey was undertaken in 2007 and 2008 that recognized the particular challenges resulting from dramatic limestone karst topography, highly variable surface geology and lack of nearby well control. The program was designed to image steeply dipping strata and fault planes; properly image shallow seismic reflections; accurately depict the potential reservoirs in the intermediate level; determine the likelihood of basement involvement in structural deformation; obtain strong seismic reflections despite karsting at the surface; and properly account for variable surface geology and resulting near-surface velocity variation. Geometric analyses, field testing and a review of analog areas resulted in an acquisition strategy different from prior Guatemala surveys. A 3 hole shot array, closely spaced receivers and shot points, high fold, and large charge sizes were determined to be optimal shooting parameters.

Follow-up geologic field studies were necessary to improve fault plane geometries and improve cross-fault stratigraphic ties. The resulting data and integrated interpretation confirmed the 2 stage deformation model (compression followed by left-slip). The integrated study suggests that the best exploration opportunities lie in large imbricated thrust fault folds that have been subsequently deformed in recent translation. Flower-structure folding has attenuated and enhanced the older thin-skinned folds.