Potash bed mapping in northern San Juan County, Paradox Basin, Utah

Andrew Rupke and Taylor Boden

Strong international demand and high potash prices have prompted a number of companies to conduct or plan potash exploration in the already productive Paradox Basin. In response to potash interest in the area, the Utah School and Institutional Trust Lands Administration has funded the Utah Geological Survey to evaluate potash beds in the Pennsylvanian Paradox Formation in about 900 square miles of northern San Juan County. The most significant potash beds in the area are in salt cycles 5, 6, 9, 13, 16, 18, and 19, and we compiled published and unpublished data on these potash beds from 132 potash and oil and gas exploration wells in and around the area. From the compiled data, which include chemical analyses and gamma-ray log data, we created isopach, grade, overburden thickness, and structure contour maps of potash beds. For the maps, we interpolated the data using an inverse-distance-squared weighting with a northwest-trending anisotropy applied to take Paradox Basin geometry into account. Initial results suggest multiple salt cycles in the area may represent a potash resource; however, the resource comprises different beds in different areas. For example, in the Lisbon Valley area, salt cycles 5 and 9 show potash potential, whereas in the Hatch Point and Hart Point areas cycles 13 and 18 show some potential. Although overprinted and complicated by post-depositional salt deformation, our results also illustrate a shifting depocenter throughout salt-cycle deposition in the Paradox Basin.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012