Favorable and Potentially Favorable Areas Hydrocarbon and Geothermal Energy Sources in Northeastern Arizona

The report area encompasses most of the eastern portion of the Colorado Plateau tectonic and physiographic province. The oil and gas accumulations found to date occur in the northeastern part of the area on the south flank of the Paradox basin. The production from the small pools near the Utah state line has been from carbonate reservoirs in Paleozoic Pennsylvanian, Mississippian, and Devonian rocks. The principal pay zones are in the Hermosa Formation of the Pennsylvanian. Hydrocarbon accumulations are controlled primarily by a combination of favorable stratigraphic and structural conditions. The Dineh-bi-Keyah field, 36 miles south of the northeast corner of the state, is the largest accumulation in the area. The reservoir for the IS-plus million barrels of oil produced to date is a Tertiary igneous sill intruded into Pennsylvanian Hermosa strata. Structurally the field is on an anticline but the oil accumulation is primarily stratigraphic. The northeastern part of the report area on the outer rim of the proved petroliferous Paradox basin offers the_mo's t attractive potential for new hydrocarbon production from Pennsylvanian, Mississippian, and Devonian reservoirs. Southward toward the Mogollon slope the decrease in the frequency of occurrence of organic limestone beds and the absence of carbonaceous shales in the Pennsylvanian suggest that source rocks adequate for the generation of hydrocarbons are not present. However, the Devonian Aneth Formation present in the Oraibi trough may be an adequate source rock. The temperature versus time relationship could have been favorable for the generation of hydrocarbons. The McCracken Sandstone of the Devonian Elbert Formation exhibits good reservoir characteristics. Numerous shows of oil have been recorded in the reservoir and some oil produced in the Walker Creek pool. This trough offers both structural and stratigraphic traps for hydrocarbon accumulations in the McCracken Sandstone reservoir.