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Incredible Tale of Texasgulf Well 7 and Fracture Permeability, Paradox Basin, Utah
Author(s) -
Huntoon Peter W.
Publication year - 1986
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1986.tb03713.x
Subject(s) - geology , anticline , petrology , echelon formation , permeability (electromagnetism) , fault (geology) , extensional fault , pressure solution , permian , fracture zone , tectonics , extensional definition , seismology , structural basin , compaction , geotechnical engineering , geomorphology , genetics , membrane , biology
Normal faults and associated extended joints form an extremely permeable zone in Pennsylvanian and Permian limestones and arkoscs along the crest of the Cane Creek salt growth anticline of southeastern Utah. These same rocks in unfaulted states comprise an extensive regional confining layer sequence. Fluids in the fault zone are sodium chloride/hydrogen sulfide brines which have bleached all permeable flow paths within the units. Bleaching patterns in outcrops reveal that circulation in the fault zone is largely restricted to the fault planes and nearby extended joints. Orthogonal joints within the fault zone are also bleached but to a lesser extent. In contrast, bleaching of all joints a short distance from the faults is rare. The highly anisotropic permeability distribution observed is characterized by maximum principal permeability tensors oriented parallel to the strike of the faults and minimum principal tensors perpendicular to the fault planes. The productive zone has a transmissivity considerably in excess of 10 s gallons/day‐foot parallel to the strike of the faults. Fracture permeability is attributed to minute separations developed along faults and joints as the rocks containing them underwent extension perpendicular to the strike of the anticline. The causative extensional stress regime was imposed on the rocks as they were bent and stretched over the growing core of the anticline. The general conclusion of this article is that extensional tectonic regimes are ideally suited for imprinting fracture permeability on brittle rock sequences. Such fractures include extensional joints and high angle normal faults. Small offsets appear to favor development of porosity because surface irregularities in the fracture planes are not ground off thereby forcing the facing surfaces to separate, and gouge development is minimized.