ABSTRACT

Log correlations, biostratigraphic data and seismic data across the South Liberty salt dome, Texas, have been used to review the stratigraphic and depositional models of a section of the Houston-Liberty delta during the Cook Mountain-Cockfield/Yegua depositional episodes. A structural cross-section is compiled to demonstrate the presence of significant structural dip and faulted intervals on the flanks of the dome. The cross-section has been used to evaluate the influence of the dome's structural history on the chemical characteristics and flow pattern of fluids in the vicinity.

Multi-element, ¹⁸O and D) composition of brines collected from oil-bearing horizons of the Frio, Yegua, and Cook Mountain Formations along the flanks of the South Liberty salt dome have been used to determine fluid sources and flow patterns around the salt dome. The water is a Na-Cl brine with total dissolved solids ranging from 68,000 mg/L to more than 200,000 mg/L from the soft geopressured transition zone. The fluid source, as indicated by chemical and isotopic tracers, is brine from the surrounding geopressured sediments mixed with the local meteoric water, with the percentage of meteoric-sourced water decreasing with increased depth. This mixing trend prevails across formations and occurs in sediments away from the salt diapir that lack a meteoric component. This suggests that the downward infiltration of meteoric-sourced water into these deeper formations is facilitated by the presence of the salt dome and associated faulting. While this mixing trend is found on all sides of the dome, isolated occurrences of brines enriched by gypsum and/or halite dissolution are suggestive of compartmentalization within individual fault blocks.