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BUITRAGO, JAIME, Exxon Exploration Company, Houston, TX

ABSTRACT: The Villeta-Caballos(!) Petroleum System of the Neiva Area, Upper Magdalena Valley, Colombia

The Villeta-Caballos(!) petroleum system of the Neiva area covers 5120 sq km and includes 18 fields with ultimate recoverable reserves of 83.8x 10*6 cu m (527 million bbl) of oil and 5.7x 10*9 cu m (201 billion cu ft) of gas. Sedimentary rocks range in age from Aptian through Holocene, and were deposited in rift, margin-sag, and foreland basins. The hydrocarbons were sourced mainly from two intervals within the Albian-Santonian Villeta Formation, and migrated from the footwall of the Chusma fault an din the center of the Neiva syncline since the end of the Oligocene to the present. The two main reservoirs are Cretaceous sandstones of the Caballos and Monserrate formations. Secondary reservoirs of significance are the fluvial sandstones of the Honda Group, of Miocene age. The traps are mainly structures associated with the formation of a fold and thrust belt which began in the Oligocene and is still active.

The system extends in time from the Aptian (to 110 Ma) to the present. The first event was the deposition of the lower Caballos reservoir. The source rock was deposited a few million years later, and reached maturity in synchronism with the formation of structural traps during the last 25 m.y. Destruction of some of the accumulations, by uplift and erosion in the fold belt, started in the Miocene.

The volume of the hydrocarbons generated by the system was calculated using an average TOC content of 2.1 wt.% for 235 m of total source interval in two intervals, and an area of mature source of 1650 sq km. A hydrocarbon generation of 325 mgHC/gTOC was used based on the Hydrogen Index measurements of immature Villeta source rock and a hydrocarbon generation algorithm. The efficiency of the system, the percentage of hydorcarbons generated that are present in discovered traps, was determined to be about 10%.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.