Fault Characterization in the Colombia Basin, Southern Caribbean: Implications for Lithology, Stress State, and Exploration Risk

Abstract

The recently acquired Esmeralda 3D seismic dataset offers a new opportunity to characterize densely faulted sediments using traditional workstation mapping techniques, depth slicing of attribute volumes, and fault detection via machine learning. The seismic data covers an area immediately outboard and north of the Southern Caribbean Fold Belt, with subtle folds in the south and homoclinal, gently south dipping deepwater sediments in the north, all deposited on thin and rugose Caribbean crust. The faults are mostly confined within one prominent sedimentary package, and display predominantly normal displacements with throws typically <25m. Fault density increases dramatically to the north, away from the thrust front within Anadarko’s COL-6 and COL-7 blocks. Fault patterns often show slightly polygonal geometries in the north, but trend mostly parallel to the subtle fold axes in the south. The quasi polygonal geometries may be interpreted as forming in a relatively isotropic horizontal stress field within fine-grained sediments. Multiple hypotheses on the controls of faulting were proposed and subsequently narrowed down to three possible mechanisms that include: (1) Forebuldge Model - basement uplift or flexure caused by fold and thrust belt loading, as well as loading from the Magdalena Fan sedimentation; (2) Reactivation of Basement Blocks - “torqueing” of basement blocks causes faulting in the sedimentary section above; and (3) Mechanical Stratigraphy - a gradual increase in fine-grained sediments to the north that is prone to faulting, and possibly triggered by some unknown combination of shortening in the south or plate extension during subduction. These observations have both negative and positive risk implications for hydrocarbon exploration. For example, there may be a greater risk of reservoir presence and quality in this interval (model 3), an increase in compartmentalization, and decrease in vertical containment. On the other hand, the faults could serve as vertical conduits that provide migration pathways between deeper source rock intervals and shallower reservoir objectives.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018