Preliminary assessment of the geothermal potential at the Papago Farms, Papago Indian Reservation, Arizona

The Papago Indian Reservation in south-central Arizona comprises 11,000 km2 in the Basin and Range province. The region is typically one of fault-bounded ranges separated by deep, sediment-filled basins. A reconnaissance geothermal assessment of the Papago Indian Reservation indicates that a geothermal anomaly exists at the Papago Farms and that one perhaps exists at Sells. More detailed analysis of existing geologic, geophysical, and geochemical data definitely confirms the existence of a geothermal anomaly at the Papago Farms. Chemical geothermometers predict a minimum reservoir temperature of 80 C. Geochemical mixing models suggest that the maximum probable reservoir temperature may be as high as l40 C. Depth to the geothermal reservoir is uncertain, but may be as shallow as 1.5 to 2 km. The possible existence of two intersecting fault zones is suggested by gravity data and interpretations of water chemistry. The suspected fault zones trend N. 81 W. and N. 18 W. and intersect at the northeast corner of the Papago Farms, in the area of well PF-7. The fault intersection would comprise highly fractured basement rock, an ideal reservoir for geothermal fluids. p.53Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu)