Conroe oil field, Montgomery County, Texas

The Conroe oil field, located in Montgomery County, Texas, was discovered in 1931. It is a broad ovate structure crossed by several normal faults which form a central graben area. The maximum vertical displacements of these faults range from 130 to 165 feet. Production is obtained at an average depth of 5,050 feet from the Cockfield formation of Upper Claiborne (Eocene) age, which has been uplifted more than 800 feet above its normal position. The average thickness of the Conroe producing sand throughout the field is 60 feet. The recoverable reserves have been estimated to be about 600 million barrels. Currently the field is producing daily 47,700 barrels of oil from 829 wells, of which 53 wells are producing salt water in varying amounts. There is free communication and equalization of fluid across the fault planes so that there exists a unit reservoir wherein the fluids segregate themselves at uniform levels throughout the field. The interval within which sand may contain oil is 130 feet, or between the -4,860-foot and -4,990-foot datum planes. A large gas cap overlies the oil and occupies an interval of 170 feet, or between the datum planes of -4,690 and -4,860 feet. Conroe has a proved area of 17,200 acres and has produced a little more than 40 million barrels of oil up to January 1, 1935. Reservoir pressures became stabilized after the field has produced about 29 million barrels of oil and the pressure decline since then has been less than one pound per million barrels of oil produced.