Abstract

Exploration for gas in the Dakota formation of the San Juan Basin can be designated as structural and stratigraphic. Petrographic analyses and subsurface studies of sand bodies below the top of the Graneros member of the Mancos formation were utilized in attempting to designate the areas best suited for stratigraphic exploration.

Valuable criticisms and contributions were made by Roy L. Pritchard, Allen J. Loleit, Marvin L. Matheny, John W. McCarthy and Roy W. Allen of the Geological Department and by Frank Barnes, consulting geologist, Santa Fe, New Mexico.

High degrees of regeneration of the quartz grains composing the Dakota have hindered the drilling and exploration of the formation, and is believed responsible for the varying degrees of porosity and permeability of the Dakota in wells in adjoining sections.

The deletion of permeability by an increase in clay mineral content of the sandstone members of the Dakota formation is believed responsible for the accumulation of gas southwest of the axis of the low portion of the basin.