Upper Magdalena Valley


Geochemistry

Heavy to normal oil predominates in the basin, varying between 12° and 35° API. A high percentage of heavy oils have been found in reservoirs of all ages. There is no direct relationship between API gravity and the reservoir depth. The oils in this basin are of regular to good quality with tendency to low API gravities and high sulfur content, due to biodegradation processes.

The thermal maturity ranges from immature to early mature. Most of the stratigraphic sequence (Tetuán Limestones, Bambucá and La Luna formations) have type II kerogen. The Caballos Formation has type III kerogen predominantly. The Tetuán, Bambucá and La Luna formations have very good to excellent potential for hydrocarbon generation. The TOC varies between 2 and 12%, the generative potential ranges between 20 and 80 mg HC / g rock. The Tetuán Limestone and La Luna Formations have the best source rock characteristics in the basin. For gas, the C2 + (%) vs. d13C CH4 (ppm) diagram (Schoell, 1983) suggests that the gas samples are of thermogenic origin with predominance of mixtures. Finally, the C2 / C3 vs. d13C c2 - d13C C3 diagram, suggest that the analyzed gas samples were originated by primary cracking.

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