Offshore Colombia Hydrocarbon Potential, Southern Caribbean

Abstract

The Magdalena Fan System, one of the last great-unexplored tertiary deltas in the world, lies offshore Colombia in the frontier southern Caribbean. Anadarko Petroleum Corporation has assembled an 11.5 MM acre position (named Grand Col) in the basin immediately outboard and north of the Southern Caribbean Fold Belt and has acquired impactful datasets that include: 2D seismic, gravity and magnetics, 30,000 km2 high-resolution 3D seismic, and over 300 piston cores. Insights into the Grand Col area using these datasets allows the key aspects of the petroleum system to be identified and risked appropriately. The deep-water Magdalena fan supplies the majority of the sediments to the Grand Col area, and clearly imaged channel-lobe-fan system morphologies on stratal depth slices of the 3D seismic data support that interpretation. The presence of medium to coarse-grained sands found in piston core samples of recent sediments gives evidence that good sand potential can be found at great distances from the entry point into the basin. The 2D & 3D seismic data show numerous amplitude and flat spot anomalies with great conformance to structure over a wide area and within a thick interval of the Magdalena Fan. Geophysical analysis and seismic response modeling of the data show the anomalies are consistent with a 3-fluid system and direct hydrocarbon indicators (DHI’s), with flat spots over 10 km in length blanketing the crest of broad, low-relief, 4-way structures. The hydrocarbons yielding the DHI’s appear to migrate up faults from greater depths, suggesting a strong thermogenic component. Seismically imaged source depocenters are located in the troughs of fracture zones and in spreading ridges associated with the disorganized opening of the Caribbean plate. These source depocenters, filled with high-amplitude, low-frequency reflectors, show significant post depositional compaction onto the basement ridges. Although we have no physical data to constrain the age of these sediments on Anadarko’s acreage, the anomalous depocenter-filled facies may be the time-equivalent to the prolific Upper Cretaceous source rocks found on-shore Colombia and also those sampled in the nearby DSDP wells (DSDP-153, -151, -146). This sedimentary fill is modelled to be mature present day for petroleum generation and likely serves as a robust source contributing to the numerous apparent DHI’s seen in the overlying Magdalena Fan deposits.

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