ABSTRACT

An exploration program was initiated during the summer of 1975 to identify prospective areas for additional reserves of gas in the Eocene Wilcox Group in Caldwell Parish, Louisiana. The area chosen included townships 11N-2E, 11N-3E, 12N-2E, and 12N-3E. A mainframe computer was utilized in the analysis and contouring of well data.

Subsurface data from 223 wells drilled prior to the time of the study were encoded and fed into the computer for preparing a variety of structure, isopach, trend surface, and residual maps. Areas of additional potential were then identified by combining anomalies defined from structure, isopach and residual maps.

The 1975 study was re-evaluated in 1985 to determine the success of the study in defining prospective areas. The original 1975 map with anomalies and well control was compared with a 1985 map showing the 1975 anomalies and new wells drilled in the 1975-1985 decade.

From this study it is shown that, of the 469 new wells drilled since 1975, 160, or 34%, resulted in gas production. Two-hundred and twenty-seven of the total wells were drilled within anomalous areas, resulting in 104 gas wells, for a success ratio of 45.8%. Fifty-six wells were drilled in the most anomalous areas, resulting in 35 gas wells, for success ratio of 62.5%. By contrast, 242 wells were drilled outside of the anomalous areas and these resulted in only 51 gas wells, for a success ratio of 21.1%.

Based on this review, it is concluded that computer analysis can significantly improve the changes of drilling success in areas with moderate subsurface control.