Conclusions

• The gas that caused the January 2001 explosions in Hutchinson, Kansas, primarily moved laterally within a 20-30-ft-thick interval, which is composed of several thin dolomite layers, approximately 170 ft above the Hutchinson Salt Member.
• The main gas-bearing interval can be correlated on gamma-ray logs throughout the Hutchinson area and shows a regional westerly structural dip, with a broad west-northwest-trending anticline (the Yaggy-Hutchinson anticline) superimposed.
• The uppermost occurrence of gas is in a slightly deeper stratigraphic interval in the northernmost vent wells and appears to step up to the south by approximately 20 ft along a northwest-trending line which corresponds to the edge of a zone of local dissolution of the upper Hutchinson Salt Member.
• Dissolution of the upper Hutchinson Salt Member in the study area occurs along two structural trends (northwest and north-northeast). This dissolution may have caused flexure and preferred zones of weakness in the overlying strata, providing pathways for gas migration.
• Deep-seated faults and fractures appear to have controlled salt dissolution.
• A combination of core and gamma ray log data indicates that the 3-finger dolomite interval is less shaly along a northwest-southeast-trending corridor between Yaggy and Hutchinson.
• Salt remnants, produced by surrounding dissolution, may have been topographic highs during the deposition of the 3-finger dolomite, leading to the production of cleaner carbonates over these remnants. The cleaner carbonates are more susceptible to fracturing and could be preferential gas conduits.
• Higher subsurface shut-in pressures have been noted in vent and observation wells closer to Yaggy and in a linear trend along the crest of the Yaggy-Hutchinson anticline.
• Current slow decline in subsurface pressure associated with negligible gas flow at the vent wells is consistent with a fracture-flow model where fracture apertures have closed with reduced gas pressure.

References

Bhattacharya, S., and Watney, W. L., 2001, Pressure and production analyses - vent wells around Yaggy gas storage facility, Hutchinson, Kansas: Kansas Geological Survey, Open-file Report 2001-68, 9 p. + 9 figs.

Bhattacharya, S., and Watney, W. L., 2002, Analysis of data from vent wells around Yaggy gas storage facility, Hutchinson, Kansas: Kansas Geological Survey, Open-file Report 2002-71.

Bhattacharya, S., and Watney, W. L., 2003, Follow-up studies related to vent wells around Yaggy storage facility, Hutchinson, Kansas: Kansas Geological Survey, Open-file Report 2003-77.

Nissen, S. E., and Watney, W. L., 2003, Detailed mapping of the upper Hutchinson salt and overlying Permian strata beneath Hutchinson, Kansas: Kansas Geological Survey, Open-file Report 2003-66, <http://www.kgs.ku.edu/PRS/publication/2003/ofr2003-66/>

Nissen, S. E., Watney, W. L., and Xia, J., 2004, High-resolution seismic detection of shallow natural gas beneath Hutchinson, Kansas: Environmental Geosciences 11, in press.

Watney, W. L., Nissen, S. E., Bhattacharya, S., and Young, D., 2003, Evaluation of the role of evaporite karst in the Hutchinson, Kansas, gas explosions, January 17 and 18, 2001; in, Johnson, K. S., and Neal, J. T. (eds.), Evaporite Karst and Engineering/environmental Problems in the United States: Oklahoma Geological Survey, Circular 109, p. 119-147.

Watney , W. L., and Paul, S. E., 1980, Maps and cross sections of the Lower Permian Hutchinson Salt Member in Kansas: Kansas Geological Survey, Open-file Report 80-7, 11 p., 9 maps, 3 cross sections.

Acknowledgments

The authors would like to thank the following individuals and corporations for their contributions to this project:

• Mike Cochran of the Kansas Department of Health and Environment (KDHE) and Larry Fisher and his staff at ONEOK, Inc., for providing subsurface information
• Rick Miller, Dave Laflen, Chadwick Gratton, and Joe Anderson for seismic-data acquisition
• Jianghai Xia for seismic-data processing
• Seismic Micro-Technology, Inc. for providing access to The KINGDOM Suite+ seismic-interpretation software
• GeoPLUS Corporation for access to the PETRA7 well-log correlation and mapping software

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Last updated June 2004
http://www.kgs.ku.edu/PRS/publication/2004/AAPG/NG_Migration/P3-07.html