Abstract: Evaluation and Management of Vertically Drained Reservoirs: Castilla and Chichimene Fields, Llanos Basin, Colombia

Kelly G. Hartshorn

The Castilla and Chichimene NE fields, operated by Chevron, are located in the southern Llanos basin of Colombia. The Castilla field, with an estimated 2.3 billion BBLS OOIP, produces heavy 14° API oil, while the Chichimene NE field with an estimated 480 MMBBLS OOIP, produces a lighter 20° API oil. Production is from multiple sandstone reservoirs of the Tertiary San Fernando and the Cretaceous Guadalupe Formations, and from massive non-marine sands of the Cretaceous Une Formation.

Early problems with water coning and high water cuts led to detailed geologic study and engineering simulation to determine the most effective methods of reservoir management. The fresh nature of the connate water made evaluation more complicated, but results of RST (Reservoir Saturation Tool) logging runs on producing wells support the conclusions of the simulation studies regarding the potential for vertical drainage of the reservoir. As a result, the massive sands of the Une Formation can be perforated in the upper portion of the reservoir only, still enabling effective drainage of the lower reservoir while reducing water production and coning problems.

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