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The I2L-3 Reservoir of the Oveja Field, Eastern Venezuela has an estimated 445 million barrels of 150 API oil-in-place.
Production history early in the operation of the reservoir pointed to a final recovery of 6.4% of the oil-in-place, or 28.5 million barrels. This figure was considerably less than that anticipated from a simple solution gas drive mechanism acting alone, 7.5% of the oil-in-place, 0 33.4 million barrels.
Individual well behavior showed this lower recovery to be mainly the result of severe water fingering, or selective encroachment of the aquifer, into successively updip outlets.
An attempt to improve upon the apparently poor depletion behavior by secondary recovery was necessary. In view of the excellent vertical permeability of the reservoir, gas availability, and the behavior of wells next to the gas cap, gas injection was recommended.
Injection commenced in August, 1961 and performance since has been very satisfactory. Gas fingering has not been a problem. The gas-oil-ratios of updip wells have been efficiently controlled by choke changes; certain wells reached by the gas-oil contact have been effectively produced at prebreak through gas-oil ratios from lowered perforations. Positive evidence of the success achieved in increasing recovery is demonstrated by the fact that water encroachment into the reservoir has been stopped. Wells which were shut-in or producing with high water cuts are now producing clean oil or producing with substantially decreased water cuts.
As of October 31st, 1966 recovery from the reservoir totaled 24.7 million barrels, or 5.6% of the oil-in-place, and the predicted recovery of 49.9 million barrels, or 11.2%, will apparently be reached.