The Monroe gas field, located in northeastern Louisiana, is about 425 square miles in area. It ranks third in area and initial reserves among the known gas fields, and has accounted for a large part of the natural gas production in Louisiana.
Gas is produced from two separate reservoir zones known as the “Gas rock” and the “Second sand.”
The Gas rock, or upper zone, occurs at depths ranging from 2,050 to 2,300 feet. In the western part of the field it lies within the Navarro (Upper Cretaceous) and consists of chalk and chalky sands of primary porosity. Because of erosion or non-deposition, the Navarro is absent over the central and eastern parts of the field where the Gas rock passes laterally into the eroded and leached part of older chalk beds, the Monroe gas rock formation (Upper Cretaceous).
The Second sand, or lower reservoir zone, occurs 100–250 feet below the Gas rock horizon. It is in part Woodbine (Upper Cretaceous) in age, and in part Comanche.
As of December, 1932, 876 gas wells have been completed in the field. Of approximately 70 wells testing the Second sand only 23 commercial wells have been obtained. The initial well-head pressure of each of the reservoirs was 1,020 pounds per square inch. The initial open-flow volumes from both the Gas rock and Second sand have ranged as high as approximately 50 million cubic feet. Approximately 1,592 billion cubic feet (metered and wasted) of gas have been taken from the reservoirs to the end of 1032.