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Abstract: Petroleum System of the Cano Limon Field, Llanos Basin, Colombia

Jorge Molina

The Chipaque-Lower Carbonera(^cirf) Petroleum System of the northernmost Llanos Basin of Colombia, covers 11,100 km2 and includes two major oil fields: Cano Limon in Colombia, and Guafita in Venezuela, jointly with three more relatively small fields in Colombia: Redondo, Cano Rondon, and Jiba. Ultimate recoverable reserves are in the order of 1.4 BBO.

The sedimentary section penetrated in the Northern Llanos has been informally subdivided into four Cretaceous formations: K3, K2B, K2A, and Lower K1 deposited during the Albian-Senonian, and into four Tertiary formations: Lower Carbonera, Upper Carbonera, Leon, and Guayabo deposited during the Late Eocene to Pliocene time. The main reservoir is the Lower Carbonera Formation, which contains 81% of the total reserves. The Cretaceous K2A and Lower K1 reservoirs contain 6% and 8%, respectively of the reserves. Minor reserves are accumulated in the discontinuous sandstones of the Oligocene Upper Carbonera Formation

Geochemical analyses of the Cano Limon/Guafita oils indicate that these are aromatic intermediate to paraffinic-naphthenic, non degradated, genetically related to a common marine-derived type of kerogen. These oils were generated by a mature, marine clastic source rock with a small contribution of continental organic matter. The geochemistry of the hydrocarbon suggest a genetic relationship with the shales of the Chipaque formation, basinward equivalent of the K2 Formation, which presents kerogen type II organic matter and has been recognized as a good source rock. The petroleum system is hypothetical because a definite oil-source rock correlation is lacking.

The development of the petroleum system is directly related to the history of movement of the Santa Maria, La Yuca, Cano Limon, and Matanegra wrench faults. It has been determined that these faults of pre-Cretaceous rifting origin, created the Santa Maria Graben of which the Espino Graben is the continuation in Venezuela. Thermal maturation modelling indicates that the hydrocarbons could have been generated from a pod of active Chipaque source rocks, located along the Santa Maria Graben. Geochemical migration indicators of the Cano Limon oils imply an original upward migration of the oil along the faults and subsequent short lateral migration of the hydrocarbons into the different reservoirs. Indicated oil migration is from the southwest. The same migration indicators suggest an order y filling of the different Cano Limon structures and reservoirs from the oil generating area. Oil generation and migration took place during Eocene/Oligocene times. The major trapping folds had been formed by that time and were filled prior to the regional tilting that started during Leon time. Subsequent re-migration of part of the oil was caused by this regional tilting and resulted in different oil property trends for different areas, as well as different zones.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela