Figure
1a. A theodolite was used to define grids for high-resolution magnetic survey.
David Laflen (left)and Gang Tian (right) are defining grids. HIGH-RESOLUTION MAGNETIC SURVEY IN LOCATING ABANDONED BRINE
WELLS IN HUTCHINSON, KANSAS
Jianghai Xia, Kansas Geological Survey, The University of Kansas, Lawrence,
Kansas
Stephen L. Williams, The City of Hutchinson, Kansas
Abstract
The City of Hutchinson designed seven sites with a total area
of 512,000 ft2 to search for abandoned brine wells after the City researched
literature of the salt mining history in Hutchinson area. A high-resolution
magnetic survey was conducted on these seven sites in May 2002. Twenty-three
anomalies were verified by excavation with a backhoe, of which are five were
identified as brine wells, four as suspected brine wells, one probable water
well, and one probable gas pipe. A monopole anomaly with more than 12,000 nanoteslas
in amplitude is a basic criterion to identify a well with an 8-inch metal case.
A monopole anomaly with several thousand nanoteslas in amplitude is a basic
criterion to identify a 2.5-inch or 4-inch well. The high-resolution magnetic
method with theodolite-defined grids was successful in locating the abandoned
brine wells in the City of Hutchinson, Kansas.
Introduction
On January 17, 2001, a natural gas explosion and fire destroyed two downtown
Hutchinson businesses. The next day another explosion occurred at a mobile home
park three miles away. Two residents died of injuries from the explosion, which
forced the evacuation of hundreds of people as gas geysers began erupting in
the area. The geysers spewed a mixture of natural gas and saltwater. The pathways
to the land surface at both the explosion sites and the geysers were abandoned
brine wells used for solution mining of salt (www.kgs.ukans.edu/Hydro/Hutch/Background/index.html,
Allison, 2001). To find these abandoned brine wells is a part of the Hutchinson
Response Project. Some known wells in the mobile home park had steel cased pipes.
The length of vertical steel pipe normally is 400 – 700 ft. An electromagnetic
(EM) method was used to successfully locate one abandoned brine well at a depth
of 5 ft (Xia, 2002a). Uniquely identifying well-generated EM anomaly in historical
salt mining sites remains as a challenge. In addition, the investigation depth
of the EM method is still an attractive research topic. However, Relatively
much higher anomalies could be observed in high-resolution magnetic measurements
based on forward calculations. The maximum magnetic signal caused by this pipe
can be higher than 15,000 nanoteslas (nT) on the top of the normal geomagnetic
field in Hutchinson, Kansas. This huge anomaly shows great promise in locating
brine wells in the City noise environment.
Figure
1a. A theodolite was used to define grids for high-resolution magnetic survey.
David Laflen (left)and Gang Tian (right) are defining grids.
Figure 1b. A portable cesium magnetometer G-858 was used to measure the total
component of thegeomagnetic field. Xia is performing the magnetic survey. A
traffic cone is acting as a line guide.
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