WINK SINKHOLES IN TEXAS OBSERVED BY SATELLITE SAR IMAGERY

Two Wink sinkholes (Wink Sink #1, #2) in Winkler County, West Texas collapsed in 1980 and 2002, respectively. The Permian basin where the sinkholes are located is underlain by thick salt beds in the depth of about 200~300 m. Anthropogenic activities related with oil and water production in the Hendrick oilfield have been considered as a primary cause of the sinkhole development. Previous studies have suggested that poor wellbore management, which failed to prevent the intrusion of freshwater and/or unsaturated saltwater into soluble rocks (evaporites), had resulted in the cavity formation, roof failure, and successive upward cavity migration. Time-series interferometric SAR (InSAR) measurements using ALOS-1, TerraSAR-X and Sentinel-1A/B satellite SAR images have revealed spatiotemporal details about the progression of the existing sinkholes and neighboring regions. Although the continuous collapse of Wink Sink #1 and #2 had ceased by about 2010, the vicinities of the two sinkholes are still subsiding at a rate of 5-6 cm/year, possibly due to the gradual deposit of the debris from overlying rock formation into the cavity. However, an alarming rate of subsidence is found 1 km east of Wink Sink #2. The peak subsidence rate of the area ranged from ~40 cm/ year during 2007-2010 to ~50 cm/year during 2010-2011, and rose to ~60 cm/year after 2016. Even though the initial trigger of the subsidence over the area 1 km east of Wink #2 might be similar to that of Wink Sinks #1 and #2 (i.e., poor borehole management, water flooding operations in a karst environment) (Kim et al., 2019), we also attribute the recent expansion and accelerated subsidence to the severe drought in 2011. Based on supplementary data from records of precipitation and groundwater level, we suggest that severe drought in 2011 contributed to the expansion and creation of ground fractures and fissures, which opened vertical pathways of freshwater into salt beds and ultimately causing such a large acceleration of subsidence. Continuous monitoring of the subsidence in the vicinity of the Wink sinkholes and other parts of West Texas is required for preventing future catastrophic outcomes of long-term developing geohazards to the area’s oil production facility, infrastructure, and human safety.