Using the Electromagnetic Method to Locate Abandoned Brine Wells in Hutchinson, Kansas

Natural gas explosions and fire destroyed two businesses in downtown Hutchinson and two residents of a mobile-home park also died of injuries from explosions. Gas geyser eruptions spewing a mixture of natural gas and saltwater in the area forced the evacuation of hundreds of people. The pathways to the land surface at both the explosion sites and the geysers were abandoned brine wells used for solution mining of salt. A part of the Hutchinson Response Project is to find abandoned brine wells. I proposed to use the eletromagnetic (EM) method to search for these wells. A GEM-2 is an EM instrument that can survey an area quickly and with great detail. Multi-frequency data are acquired simultaneously with a maximum sampling rate of 30 Hz when an instrument operator walks along a survey line. For each frequency, both in-phase and quadrature components of the induced EM field in ppm (parts per million relative to the primary field) were recorded. Three frequencies were chosen for this project: 2,430 Hz, 7,290 Hz, and 18,270 Hz. EM signals from a known well were first recorded to determine what kind of anomaly would be identified as a possible buried well. The signals were then compared with EM reconnaissance results acquired at a designated area. EM results successfully located one uncapped abandoned brine well 4 inches in diameter and buried at a depth of 5 ft. This survey result indicates the potential investigation depth with a GEM-2 would be as deep as 20 ft in this specific area. This survey also demonstrated the importance of acquiring target signals in interpreting anomalies. Based on these results, EM surveys in Hutchinson will be successful and effective in locating the abandoned brine wells.