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Tales from the Field by Jeremy C. Wire Geoconsultants, Inc. The Case of the Well that Resisted Destruction In our region, there are several different ways to destroy or abandon a water well once its useful life is over - the most common being by the procedure of “blasting”. Generally, the well is cleared of any debris or junk to the original total depth, if possible; a string of charges matching the depth interval to be destroyed is lowered into the well; and an appropriate mixture of cement is introduced, filling the casing. Then the charges are detonated, demolishing the casing and forcing the cement mixture into the for- mation, destroying the well. Usually, the only effect at the surface is a slight “bump” felt by persons standing around at a safe distance from the center of activity. Sometimes, unexpected results occur despite covering the open casing with ply- wood and sandbags - particularly if the charges are set too close to the surface. In this situation, a “geyser” of water and cement may erupt, coating everything (and anyone) too close to the action. The municipal well involved in this tale was drilled in the early 1960s and, being over 50 years old, was showing its age. So the city decided to destroy it, as other uses for the property were planned. The well had a large-diameter conductor casing ending at a depth of about 100 feet, and was assumed to have an annular seal. However, the presence of a seal or its condition could not be verified in the field or from existing data. When the well was constructed, water levels were deep, but in later years, artesian conditions prevailed. At the time of destruction, the well was flowing, a condition which was consid- ered in the original work plan for the procedure, so diversion of the flow was main- tained to allow the operation to proceed. The blasting charges were fastened to a PVC pipe to resist “floating” out of position in the casing; the assembly installed in the well; and the cementing mixture introduced, with minor difficulty. The charges were detonated, with the usual bump being felt - disappointing those persons who had never witnessed this type of well destruction and expected something more exciting to occur. The cement level fell in the casing, the artesian flow ceased, and everyone involved thought the operation was successfully concluded . . . but not quite, as it turned out. Several days later, the contractor returned to the site to cut off the casing, top off the cement, and fill a shallow excavation around the casing back to grade. Some artesian flow was seeping from around the exposed casing into the excavation, so obviously the blasting did not result in a perfect seal, and additional measures needed to be taken. A specialized cementing crew was employed, and they drilled several holes around the circumference of the casing to a depth of 80 feet, followed by pressure grouting them with quick-setting cement. This operation stopped the flow of water, much to the relief of everyone involved, particularly the contractor. The excavation was left open for several days to make sure the sealing operation was effective; and the well capped with cement and the excavation filled to grade. Based on this experience, it was decided that if another well like this one with artesian conditions were to be destroyed, and if there was any question about the presence or condition of an annular seal, the conductor casing would be pressure grouted as the first operation in destruction - not the last one. Unfortunately, this conclusion was reached the hard way, con- firming the old adage: “Experience is the best teacher” - and it certainly was in this case. Jeremy Jeremy Wire may be contacted via e-mail to michele@worldwidedrillingresource.com 35 WorldWide Drilling Resource ® FEBRUARY 2019 Atlantis Vault • Self-Contained • Simple installation • Trouble-free operation For more information call: (270) 786-3010 or visit us online: www.geothermalsupply.com EXB Celebrating Safety Since 1925 Adapted from Information by the National Mining Association Cosponsored by the National Mining Association (NMA) and the U.S. Department of Labor’s Mine Safety and Health Administration (MSHA), the Sentinel of Safety award is among the most prestigious awards in the mining industry. The award began in 1925, by Herbert Hoover who was Commerce Secretary at the time, as well as a former mining engineer. It contin- ues to reward safety nearly a century later. The Sentinel of Safety award acknowledges mining operations for outstanding worker safety and is given out annually to the nation’s safest mines with a minimum of 4000 injury-free hours. Of the roughly 13,000 mining operations in the country, MIN Celebrating Safety cont’d on page 44.