Print this pageAbstract: Salt Dissolution in Oil and Gas Test Holes in Central Kansas
During the drilling of the 72,000 oil and gas test holes which penetrate the Hutchinson Salt Member of the Permian Wellington Formation, salt dissolution commonly resulted in borehole enlargement to 6 to 10 diameters in rotary holes of the 1930s and 1940s and to 3 diameters in recently drilled boreholes. The salt, nearly 300 ft thick, is locally thinner on anticlines in central Kansas because of depositional variation. It includes 25 to 33 1/3 percent of bedded shales.
No postdrilling salt dissolution occurs when properly cemented surface casing isolates all aquifers above the salt. This conclusion, based on the hydrology of central Kansas aquifers, appears valid regardless of how the boreholes are plugged or if they are plugged at all. Exceptions are seven known cases of severe postdrilling salt dissolution causing surface subsidence. These are associated with high-energy-input situations, principally salt-water-disposal systems, in which corrosion caused casing leaks. Three such subsidence areas are in the Chase-Silica field (260 million bbl cumulative oil production) and two due to uncased aquifers above the salt in the 50+ year-old Gorham field. A comparable subsidence area at the Cargill Salt, Inc. plant in Hutchinson, Kansas, collapsed October 21, 1974, leaving the Missouri-Pacific railroad tracks suspended in midair. This is in comparison with the rare subsidence areas (ratio one subsidence area per 10,000+ boreholes drilled) caused by salt dissolution in oil and gas test holes in Kansas.
APG Search and Discovery Article #90974©1975 AAPG Mid-Continent Section Meeting, Wichita, Kansas