ABSTRACT: The Giant Cano Limon Field, Llanos Basin, Colombia

C. N. McCollough, J. A. Carver

After 40 yr of sporadic exploration that yielded negative or marginal results, the Llanos basin of eastern Colombia was thrust to the forefront of world attention by the discovery of the giant Cano Limon field in July 1983.

This discovery was the culmination of an intensive 3-yr exploration effort by Occidental involving 4000 km of dynamite seismic, 20 stratigraphic tests from 396 to 1067 m (1300 to 3500 ft) deep, and 12 exploratory wells.

Prior to Oxy's entering the area, there had been 61 exploratory wells drilled with meager results, namely two fields with total reserves of about 20 million bbl of light oil and one field with reserves of 90 million bbl of 13.6° API oil--none of which were commercial.

The Llanos basin was known for its abundant excellent reservoir sandstones and opinions varied as to whether there was adequate source rock. The major problem had been defining traps. Except for the very young folding along the Andean front, the known structural traps were sparse and subtle.

Most of the exploration had been done in the western part of the basin near the basin deep or in the Andean foothills. Occidental took a very large acreage position east of the area of past exploration efforts and found an exception to the small fault closures known elsewhere in the basin.

This exception, the Cano Limon area, is dominated by major early Tertiary northeast-southwest strike-slip faulting. Concurrent folding in combination with fault sealing formed the Cano Limon field and other much smaller fields in the area.

The Cano Limon field, encompassing 3570 ha (8821 ac), contains an estimated 1.8 billion bbl of oil in place, of which 1.6 billion bbl are expected to be recovered with the very strong natural water drive.

The bulk of the oil is in deltaic sandstones of the Eocene Mirador formation with additional reservoirs in the Upper Cretaceous. The average porosity of the Mirador is about 25%, the permeability is about 5 d, and water saturation is about 23%. Individual well flow rates have exceeded 20,000 BOPD. The average oil gravity is 29.5° API, with a GOR of 8 ft³/bbl and sulfur content of 0.41%. Current production is about 230,000 bbl/day.

AAPG Search and Discovery Article #91000©1990 AAPG Conference-Giant Oil and Gas Fields of the Decade 1978-1988 Conference, Stavanger, Norway, September 9-12, 1990