Coalbed methane is playing an increasingly important role in meeting the energy needs of the United States. According to one estimate, this unconventional gas may supply 4-5% of the domestic natural gas in 1994.

The Plio-Pleistocene hydrocarbon fairway of offshore western Louisiana is restricted to the outer continental shelf and upper continental slope where a thick wedge of nearshore and deep-marine sediments was deposited.

Natural gas in the United States consists of proved reserves in known reservoirs, of inferred reserves and undeveloped resources within these reservoirs, and of undiscovered resources.

Official estimates of United States coal resources published during the past 15 years vary from less than 1.5 to 3.5 trillion metric tons (1.7 to 3.9 trillion short tons). These differences imply that a high degree of uncertainty exists in resource assessment.

Texas lignite occurs in three Eocene (lower Tertiary) geologic units--the Wilcox Group, Jackson Group, and Yegua Formation--and in three ancient depositional systems--fluvial, deltaic, and strandplain/lagoonal.