Rates of Growth of Plio-Pleistocene Oil Traps in the Colombian Eastern Foothills: Impacts for Along-strike Differential Hydrocarbon Charge

Taylor, Michael¹; Veloza, Gabriel; Mora, Andres; Monsalve, Gaspar; Sheehan, Anne; Worthington, Lindsay; and Becker, Thorsten W.
¹[email protected]

Tracking the growth of hydrocarbon structural traps through time is critical to understand the effectiveness of hydrocarbon charge processes. Today, rates of growth can be obtained with increasing resolution using the most cutting edge dating techniques. This allows for making better predictions about hydrocarbon charge and accumulation. Here we show that neotectonic rates of growth are important for understanding hydrocarbon traps along the eastern foothills of Colombia. Northwestern South America is an intriguing tectonic setting where the interaction between the Caribbean, Nazca, and South American plates are producing complex patterns of active fault systems. In the Llanos basin, Colombia, active thrust faults have uplifted fluvial strath terraces in the upper plate of the east-directed frontal thrust system bounding the eastern Colombian Andes. Neotectonic field mapping and structural controls obtained from seismic reflection data along the north-south length of the basin provides geometric constraints for the style and rate of recent shortening across the active thrust front. Seismic reflection data indicates listric geometries are common for many of the active thrust faults. At four along-strike locations, Quaternary geochronology obtained for the faulted terraces and the magnitude of fault slip since terrace abandonment allows us to estimate recent shortening rates of approximately 2 mm/yr or more. The fault geometry and shortening rates we obtain imply that the structural traps developed only recently, and that the faults may be acting as conduits for oil migration from structurally deeper levels that are currently untapped resources. Interestingly, some of the young traps coincide with giant oil fields like the Cusiana (ca. 2 Ma old), whereas others like Tame (ca. 0.39 Ma) coincide with traps associated with minor to non-commercial oil accumulations. Such different relationships between young traps and oil accumulations suggest the absence of an active oil kitchen adjacent to the trap. However, the Tame field is much younger than the Cusiana, therefore it could be a case of an extremely young trap which may imply that too short of a time has passed to be adequately charged with oil. These structural relationships underscore the need for deep crustal imaging that will potentially lead to new and profitable discoveries.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013