Natural Gas in Bend Arch District, Texas
Gas development in the Bend Arch district of Texas has been in progress for about 20 years, but gas was not marketed to any extent until several years after its discovery. Prior to the entrance of gas pipe lines into the area, gas wastage was tremendous.
Production is obtained chiefly from the Strawn formation, of Upper Pennsylvanian age, and the Bend group of Lower Pennsylvanian age. Depths of gas wells vary from 160 feet to approximately 4,500 feet. Gas is widely distributed, geographically, in the area. Gas-producing horizons are numerous and widely distributed, stratigraphically, throughout rocks of Pennsylvanian age. Production is not obtained from the Bend arch as one large major structure, but from minor folds superimposed on its crest and flanks. Minor structures in the Bend formation are at places reflected in the structure of surface rocks, but in most places the relation is slight or entirely absent.
Gas occurrence is determined primarily by distribution of source and reservoir rocks, and secondarily by structure. The restricted area of the lenticular reservoirs, and in the Bend formation the scarcity of water, preclude gas migration for appreciable distances. Deep gas, especially that from the Bend, is much more valuable than shallow gas because of higher rock pressure, longer life, higher B. t. u., and gasoline content.
Total gas recoveries vary widely, even from the same sandstone zone at different localities. Several wells have produced more than 1 billion cubic feet of gas. Some wells beginning with good initial volume and pressure, however, have produced less than ten times the amount of their initial open flow.
A few deep tests have been drilled below the upper part of the Ellenburger limestone (Ordovician), two of which reached pre-Cambrian rocks.
Because of the large area of potential gas territory; indefinite relation, in many places, of gas occurrence to structure; possibility of developing heretofore neglected small gas showings in the Bend into commercial wells by shooting; and because of the fact that oil rather than gas was the objective during greatest drilling activity, the Bend Arch district is considered an important, but erratic, future gas reserve. If market demand warrants, the area will probably be drilled for gas for several years.