Recently recovered records from more than 600 historical mine borings in Culberson County, Texas, yield unique insight into evaporite karst mechanisms and drilling-hazard risks in the western Delaware Basin. Lost-circulation events systematically decline in frequency with increasing depth below ground surface in the Castile Formation, suggesting a strong connection to near-surface processes. Spatially, lost-circulation events are more than twice as common in locations with sulfur shows compared to other areas, reflecting local sulfuric-acid–enhanced karsting and the presence of secondary sulfur-bearing limestone with vuggy porosity. The lack of widespread events at great depths indicates that many voids associated with ancient, basinwide, hypogene karsting episodes have collapsed and filled in following Miocene–Pliocene denudation of the Guadalupe Mountains. Overall, the probability of encountering lost circulation due to karst features in this area is relatively low (<7% below the typical conductor string depths of modern wells). Moreover, modern wells that avoid areas with sulfur mineralization experience these events at lower frequencies (<1% in a sample set of more than 100). Nevertheless, areas near surface drainage features or large sulfur accumulations are at above-average risk and may merit additional investigation. Some H2S and sour hydrocarbon gas encounters also occurred but only around mappable native sulfur deposits. These data provide a critical foundation for assessing shallow geohazards in a rapidly developing unconventional superbasin, delineating causes of modern and ancient karst in the Castile Gypsum Plain, and providing constraints for regional paleohydrologic models.

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