The Salt Flat oil field in southern Caldwell County, Texas, was opened October 13, 1928, making the third oil field in Caldwell County producing from the Edwards limestone. A daily peak of 52,013 barrels was reached on June 18, 1929. In all, 343 wells have been drilled, only 25 of which are dry holes.

The Salt Flat field is located parallel with, and on the southeast or upthrown side of, a fault which strikes N. 30° E. The fault has a maximum vertical displacement of 375 feet.

The pay formation is the upper 25-35 feet of the Edwards limestone (Comanche), which is a porous dolomitic limestone with lenses of indurated cherty limestone. The upper few feet of the pay formation is ordinarily soft yellowish limestone, commonly referred to as "dobe." A few wells have encountered commercial production above the Edwards limestone. The surface beds in the Salt Flat field are Wilcox sand and shale, which are Eocene or early Tertiary in age.

The Salt Flat field, which consists of 1,196 productive acres, produced 13,790,362 barrels of 36° gravity oil (A. P. I.) to the end of 1929. It is estimated that the ultimate recovery will be approximately 30,000 barrels per acre, or a total recovery of approximately 36,000,000 barrels of oil for the entire field.

The average depth to the pay horizon is 2,700 feet, and rotary methods of drilling have been used exclusively. Most of the wells are pumped with individual electric pumping units.