East Texas Oil Field
The East Texas Oil Field is a large oil and gas field in east Texas. Covering 140,000 acres (57,000 ha) and parts of five counties, and having 30,340 historic and active oil wells, it is the second-largest oil field in the United States outside Alaska, and first in total volume of oil recovered since its discovery in 1930.[ 1] Over 5.42 billion barrels (862,000,000 m3) of oil have been produced from it to-date.[ 2] It is a component of the Mid-continent oil field, the huge region of petroleum deposits extending from Kansas to New Mexico to the Gulf of Mexico.
The field includes parts of Gregg, western Rusk, southern Upshur, southeastern Smith, and northeastern Cherokee counties in the northeastern part of the state. Overall the field is about 45 miles (72 km) long on the north-south axis, and five miles (8 km) to 12 miles (19 km) across. The producing sands were relatively shallow at about 3,500 feet (1,100 m), was high gravity, low in sulfur, and yielded a high percentage of gasoline (up to 37 per cent).[ 3] Interstate 20 cuts across the field from east to west, and the towns of Kilgore, Overton, and Gladewater are on the field. At one time, downtown Kilgore had more than 1,000 active wells clustered in a tight area, making it the densest oil development in the world.[ 4]
The primary productive geologic unit is the Cretaceous-age Woodbine Formation, a regional petroleum-bearing unit which had been known since the early part of the 20th century. This sandstone unit was deposited during a period when East Texas was a shallow sea, approximately 100 million years ago. During a subsequent period it was uplifted with the Sabine Uplift, eroded, and then covered again by the sea, which this time unconformably deposited a layer of impermeable chalk, the Austin Chalk, creating a stratigraphic trap – a situation where oil, which is lighter than water and migrates upwards, reaches a point where it can move no farther, and pools. The source rock for the oil in East Texas is the overlying Eagle Ford Shale.[ 5] [ 6]
