Structural Controls on Ochoan Salt Dissolution and Delaware Mountain Group Oil Field Permeability Trends in the Delaware Basin, West Texas and Southeast New Mexico
ZAENGLE, JOHN F., and KYGER C. LOHMANN, University of Michigan, Ann Arbor, MI
A Landsat TM image of the Delaware basin, west Texas and southeast New Mexico, reveals geomorphic lineaments and tonal anomalies with preferred northwest-southeast and northeast-southwest orientations. Lineament orientations are the same as the trend of joints and fractures observed in Delaware Mountain exposures and from subsurface borehole break-out and televiewer data. These data suggest that lineament trends are controlled by subsurface joints and fractures.
Core, well log, and seismic data indicate that areas of Ochoan salt dissolution along the western margin of the Delaware basin form elongate fingerlike fronts that are coincident with the northeast-southwest trend of structural lineaments mapped using Landsat TM data. Striking spatial correlations also exist between the position of Ochoan salt dissolution fronts and linear, northeast-southwest-trending oil field permeability barriers in the underlying Delaware Mountain Group.
Petrographic data indicate that Delaware Mountain Group porosity/permeability development is controlled in large part by the occurrence of calcite/dolomite cement and chlorite/corrensite clays. The unimodality of grain size, sorting, and framework grain mineralogy, along with the virtual absence of detrital clays, favors a diagenetic control on cementation patterns. These observations coupled with formation water chemistry, and cement carbon-oxygen isotope and fluid inclusion data suggest that the occurrence of Delaware Mountain Group cements is related to diagenetic alteration by waters that have dissolved Ochoan halite and potash salts.
Hydrodynamic fluid flow along joint and fracture systems coupled with rock-water interactions are proposed that account for the coincidence of salt dissolution fronts and oil field permeability barriers as well as formation water chemical trends and cement isotopic signatures. Preliminary data suggest fracture systems provide conduits for hydrodynamic fluid flow capable of extensive Ochoan salt
dissolution and the transport of reactive solutions to remote horizons both laterally and vertically in the basin.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)