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Geophysical Delineation of Megaporosity and Fluid Migration Pathways for Geohazard Characterization Within the Delaware Basin, Culberson County, Texas


Differential dissolution of gypsum karst within the Delaware Basin poses a significant threat to infrastructure that industry depends on. The study area is located in Culberson County, Texas and traverses a distance of approximately 34 miles along RM 652. It is located on the northern margin of the Chihuahua Desert and includes outcrops of Castile and Rustler strata that host karst geohazards. The objective of this research was to characterize and delineate anomalies along RM 652 using electrical resistivity. Regions of karst geohazard potential were found in evaporite throughout the Castile Formation outcrop; minimal hazards were documented in the Rustler Formation. A TR5 OhmMapper capacitively-coupled resistivity meter was used to acquire resistivity data for geohazard characterization. This study utilized a traditional dipole-dipole array, and the depth of investigation was dependent on the electrode spacing. An electrode spacing of 2.5 meters was used, with a transmitter offset of 2.5 meters. This geometric configuration, combined with the medium analyzed, allowed for recordings to be made as deep as 5 meters. Data acquisition was recorded at approximately 2 miles per hour at a rate of 1 transmission per second. Resistivity data was processed using AGI's EarthImager 2D inversion software to produce a Smooth Model Inversion with a 10.0 smoothness factor after 8 iterations. Resistivity data collected from the OhmMapper successfully imaged significant anomalous patterns throughout the study area. Field checks were conducted in order to correlate resistivity lab interpretations, with karst surface expressions. Results yielded caves, vertical conduits in gypsum bedrock, extensive sink filled areas, lateral piping, and heavily leached zones. These features could potentially lead to catastrophic failure that could have significant impact on the petroleum industry throughout this region.