Abstract: Texas Lignite

W. R. Kaiser, C. G. Groat

Lignite is present in three Eocene stratigraphic units, the Wilcox Group, Yegua Formation, and Jackson Group, and in three depositional environments, fluvial, deltaic, and lagoonal. In East Texas, north of the Colorado River, fluvial lignite is dominant in the Wilcox and Yegua. Seams represent swamp accumulation in interchannel basins on the lower alluvial/upper delta plain. Jackson lignite in East Texas is deltaic and represents marsh-swamp accumulation in lower delta-plain environments. Lagoonal lignite dominates in South Texas, south of the Colorado River, and is in all stratigraphic units topping strand-plain-barrier bar sequences.

Statewide resources above depths of 200 ft (61 m) are estimated conservatively at 10 billion short tons (9 billion MT) with an additional 100 billion tons (90 billion MT) between 200 and 5,000 ft (61 and 1,524 m). On an as-received basis, ash and sulfur contents range from 10 to 35 and ½ to 2% respectively with heating values of 4,500 to 7,500 Btu/lb (2,500 to 4,200 kcal/kg). The largest reserves of highest grade lignite are in the Wilcox of East Texas in seams 2 to 22 ft (0.6 to 7 m) thick. Deposits of secondary importance, in terms of reserves and grade, are in the Yegua and Jackson in seams 2 to 12 ft (0.6 to 4 m) thick. The poorest grade lignite is in South Texas.

Three large steam-electric plants are using Wilcox lignite. Future plants will use not only Wilcox but also Yegua and Jackson lignite. Production, all from area-strip mines, jumped from about 2 million tons per year (1.8 million MT) in 1970 to 11 million tons (9.9 million MT) in 1975 with at least 50 million tons (45 million MT) projected for 1985.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC