The south Texas report includes 58 counties within Texas Railroad Commission districts 1, 2, and 4 and portions of the Texas offshore.

District 1 exploration activity was down 11.7% from 1979 figures. However, the success rate increased from 23.1% to 37.1%. The heaviest concentration of exploratory drilling was in Zavala, McMullen, and Gonzales counties. Upper Cretaceous objectives were the most frequently explored.

District 2 exploration activity decreased for the second year in a row, down 7% from 1979 and 22% from 1978. The success rate was much higher in 1980; this figure increased by 23%. The Frio trend received the most attention in this district, accounting for 53% of new discoveries. Activity in the Wilcox trend remained steady, with continued success in the play for deeper objectives.

District 4 exploration activity remained at the high level established the previous year, and 579 wells were drilled. The success rate for all exploratory categories was 61%. Frio objectives accounted for 236 wells, or 41% of total exploratory drilling. The Wilcox trend saw sharply increased activity over already high 1979 levels. Thirty-three percent more wells were drilled, resulting in 81 discoveries in 1980. Webb County was the site of most of the activity. The downdip Wilcox trend is expected to become more active, as Fandango field was successfully developed in 1980.

Exploration activity in the south Texas offshore area declined from the 1979 total of 119 wells to 102 for 1980. Development drilling also decreased, although the success rate of 59% was much improved over the 1979 level of 29% and the 1978 level of 6%.