Major tight gas sandstones in Texas range from lenticular to blanket geometry, from hydropressured to geopressured, and from Pennsylvanian to Eocene in age. The Cotton Valley sandstone (East Texas basin) includes barrier- and marine-bar sandstones (blanket) derived from prograding fan deltas with associated braided stream, delta-front, and pro-delta deposits. The overlying Travis Peak Formation contains a lower deltaic facies, a middle, dominantly braided fluvial facies (broadly lenticular), and an upper transgressive clastic-to-carbonate transition. Estimated gas in place varies from 53 tcf (Cotton Valley) to 25 tcf (Travis Peak); most wells initially produce from 500 to 1,500 mcf and few wells produce 2,500 mcf. Tight gas sandstones in the Wilcox and Vicksburg Groups (Gulf Coast basin) are mostly geopressured delta-front, shelf, and slope deposits. These lenticular sandstones isolated in shale have pressure gradients up to 0.81 psi/ft (18.3 kPa/m). Initial well yields are mostly 300 to 2,400 mcfd; resource estimates for tight Wilcox and Vicksburg trends are not available.

Canyon Group sandstones of the Sonora basin (parts of the Ozona arch, Concho platform, and Val Verde basin) contain 24 tcf of estimated gas in place and initial flow rates are commonly 100 to 1,000 mcf. These sandstones are broadly lenticular and are interpreted to be submarine fan and possibly shelf-margin deposits. The Olmos Formation (Maverick basin) contains gas within broadly lenticular delta-front deposits of high-constructive delta systems; liquid hydrocarbons in the Olmos are trapped in more proximal facies. Gas in place in the Olmos is estimated to be 5 tcf and initial well yields are 300 to 3,000 mcf. In 1980, 893 wells were completed in formations designated as partially or completely tight by the Railroad Commission of Texas. These completions represent 2.5% of new gas wells in the state, but 28.0% of those completed in the 5,000 to 15,000-ft depth range in that year.

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