A new geologic evaluation of Swan Lake field led to the discovery of 24 new reservoirs. The field originally was found in March 1950; initial development drilling ended in 1957. Sun Oil Co. took over operations in 1970. A new lower Frio structural

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interpretation indicated the crest of a deep closure had not been penetrated. The Sun 27 G. T. Brooking, drilled in December 1972, found new deep production. New reservoirs also were discovered in the previously drilled upper part of the Frio section.

The improved logging techniques used in the wells allowed a more quantitative look at all the sandstones. Combination logging tools providing a simultaneous recording of induction resistivity, acoustic velocity, and computed Rwa curve were used exclusively. Using the Rwa curve as a hydrocarbon indicator, low resistivity sandstones that appeared wet from casual examination were tested and found productive. Other sandstones which appeared to have no vertical separation from overlying water sandstones were tested and found productive.

Twelve new wells were drilled from 1972 through 1974. The drilling program resulted in a significant increase in the daily gas and oil production. Multiple recompletion opportunities also were recognized.

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