CAPACITIVELY-COUPLED RESISTIVITY CHARACTERIZATION OF KARST GEOHAZARDS AND DELINEATION OF MEGAPOROSITY AND FLUID MIGRATION PATHWAYS WITHIN THE DELAWARE BASIN, CULBERSON COUNTY, TEXAS

Differential dissolution of gypsum karst within the Delaware Basin poses a significant threat to infrastructure that society depends on in the form of geohazards. The study area is located in Culberson County, Texas and traverses a distance of approximately 55 kilometers along RM 652 which crosses outcrops of Castile and Rustler strata that are known to host significant karst phenomena. This research characterizes and delineates anomalies along RM 652 using electrical resistivity; regions of karst geohazard potential were found in evaporites throughout the Castile Formation outcrop, while 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; 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 three kilometers per hour at a rate of one transmission per second. Data was processed using AGI’s EarthImager 2D inversion software to produce a Smooth Model Inversion.

Resistivity data analyses successfully imaged significant anomalous patterns throughout the study area. Field checks were conducted in order to correlate resistivity interpretations with karst surface expressions. Results identified karst geohazards that showed preferential drainage and fluid migration with associated suffusion. These phenomena include suffusion induced caves, vertical conduits in gypsum bedrock, extensive filled sink areas, lateral piping, and heavily leached zones; anthropogenic structures in the study area can pose a high risk of enhancing suffusion and karst processes. These geohazard features could potentially lead to catastrophic road failure that would have a significant impact on the surrounding industries throughout this region.