The Erath field, situated in eastern Vermilion Parish, Louisiana, is one of the major gas-condensate reserves of the Gulf Coastal area of Louisiana and Texas. It is a large domal uplift having a 325-400-foot down-to-the-coast fault extending east and west across the north flank. It is regarded as a deep-seated or non-piercement salt dome.

No structural expression of the uplift is present on the surface of the low plain which ranges in elevation from 6 to 10 feet above sea-level.

Gas-condensate saturation exists in nineteen sands of Miocene age ranging in depth from 8,100 to 12,000 feet. These reservoirs range in size from an estimated 40 acres to 3,000 acres and in volume from 380 acre-feet to 202,000 acre-feet, respectively. Maximum net sand thickness for individual sands ranges from 7 to 178 feet.

Maps showing structure and net sand thickness of ten of the productive sands and tables outlining pertinent reservoir data are included.

The presence of the structure was detected by seismograph surveys by several companies. The discovery well was The Texas Company's Vermilion Parish School Board No. 1 in the SE. ¼ of Sec. 16, T. 13 S., R. 4 E. It was completed on April 26, 1940.

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Testing of the Phillips Petroleum Company's Fitzsimmons No. 1, shortly thereafter, revealed the character of the products in place and the potential importance of the reserves. This led to a decision by the principal operators to unitize their holdings below 8,000 feet in depth and to erect a 200,000,000-cubic-foot-capacity cycling plant which would yield 18,000 barrels of liquid products per day. Twenty-nine wells, twelve of which were dually completed, were used in the initial cycling operation.