The Luling field, in Caldwell and Guadalupe counties, Texas, is a fault structure located about 20 miles southeast of the main Balcones fault. The area is drained by San Marcos River. The Wilcox formation is exposed at the surface and the producing formation is the Edwards limestone of the Comanchean Cretaceous. The field is 7.5 miles long and averages about ½ mile wide. The discovery well was brought in on August 14, 1922. On December 31, 1924, there were 391 producing wells in the field.

The structure is a faulted monocline limited on the northwest, northeast, and southwest by faults of about 450-foot displacement. The strike of the structure is NE.-SW. The heave of the fault measured on the top of the Edwards is 1,000-1,800 feet. The highest points of the structure are near the two extremities of the field, the middle portion being about 40 feet lower. The sedimentary column seems to overlie a metamorphic basement composed of rocks of early Cretaceous or pre-Cretaceous age. The average depth of the top of the Edwards oil horizon is about 2,100 feet. The oil is of about 27° Baume gravity. The total production of the field to December 31, 1924, was about 14,500,000 barrels and the daily production about 30,000 barrels.