The South Texas report includes 58 counties in Texas Railroad Districts 1, 2, and 4 and parts of the Texas offshore.

District 1 exploration activity increased 8.9% from 1978. However, the success rate was down from 30.7% in 1978 to 23.1% for this year. Drilling for Upper Cretaceous pays was the focus of activity in 1979. Average well depth was 539 ft shallower than last year because of a decline in exploration for deep Cretaceous objectives.

District 2 exploration activity decreased 15.4% with 394 wells drilled. The success rate was 2% higher than in 1978; there were 146 gas and 25 oil completions. Activity continued to be heavy in the Frio trend within Victoria, Jackson, and Calhoun Counties. Exploration increased in the deeper Wilcox trend in Live Oak, Karnes, Bee, and Dewitt Counties.

District 4 exploration activity was up sharply this year with a 33% increase over 1978 totals. The success rate was 56%. The Frio trend was most active, recording 268 exploratory attempts. The deepest completion in the district in 1979 was in the Vicksburg at 15,532 ft. Vicksburg trend activity was up 67% this year with 127 wells drilled. Very active drilling in the Wilcox Lobo trend produced significant new extensions north of the town of Laredo. The downdip Wilcox trend was successfully explored in northeast Zapata County on strike with northeast Thompsonville field, 20 mi away.

Exploration activity in the South Texas offshore area declined from the 1978 total of 143 wells to 119 for 1979. Average footage per well, however, increased by 543 ft.