The Four Corners region includes 40,000 square miles in New Mexico, Colorado, Utah, and Arizona and is underlain by Mesozoic sediments. Within this area, 21,000 square miles are underlain by sediments at depths favorable for oil or gas production in at least one formation. The present development of oil and gas fields in this area was foreshadowed by shows of oil and gas in early wells, and by seeps in outcrop areas. Much of the present significant production is associated with stratigraphic changes in the formations which produce.

End_Page 951------------------------------

The Triassic Shinarump conglomerate, the Jurassic Entrada sand, the uppermost Jurassic Morrison(?) sand, the Upper Cretaceous Dakota-Graneros sands, and many other Upper Cretaceous sands intertonguing with the Mancos and Lewis shales have a record of oil and gas shows which has not been fully exploited in 90 per cent of the favorable area.

Exploration frontiers associated with sedimentation exist as overlooked variations in deposition, development, and permeability of the Mesozoic sands. Frontiers associated with structure exist with possibility of fault traps, permeability traps, and hydrodynamic traps on low plunging folds with no apparent surface closure. Closure may exist on these folds in the pre-Cretaceous sediments.

The known lithologic variations of the many possible reservoir beds, when combined with known regional structural anomalies, point to many areas of possible production in the sands with a proved record of shows.

End_of_Article - Last_Page 952------------