12 JULY 2022 WorldWide Drilling Resource® When Gas Wells and Mining Collide Adapted from Information by the U.S. Mine Safety and Health Administration Across the country, thousands of gas and oil wells penetrate coal seams being actively mined, which could be dangerous. If a mine runs into an active gas well, methane gas can flood the mining section. Abandoned wells in depleted gas and oil reserves can pose a similar hazard because they can recharge with gas over time. Flooded and abandoned wells can cause injuries by forcibly ejecting material into the mine or by submerging mining sections with water. Every year, the U.S. Mine Safety and Health Administration and state regulatory agencies evaluate around 1000 requests to mine within 150 feet of gas and oil wells. The primary technical document used to address the issue of gas and oil wells intersecting underground mines has been the “Pennsylvania Joint Oil and Gas Well Gas Well Pillar Study” which was conducted by the Joint Coal and Gas Committee, including members from both the coal and gas industries, and published in 1957. They studied mining-related well failures from gas and oil companies, and obtained mining data from the associated coal companies. Mining in the case histories occurred between 1918 and 1956, before continuous miners were widely used. The depth of cover was less than 650 feet in all of the cases, so the study recommended the setback distance (the distance between a well and the closest point of development mining, or the rib-to-well distance) of 50 feet. A lot has changed in both the mining and gas industries since 1957. Not only are powerful continuous miners used more frequently, modern coal mines are deeper than 650 feet. When combined with the increased development of high-pressure gas wells, the potential consequences of an incident are even higher. New scientific information, most notably downhole gas well surveys, show depth has a big effect on the possible deviation between a well’s surface location and its location at the coal seam level. Today, Key Safety Practices when Mining Near Gas or Oil Wells Include: 1. Defining a special precaution zone around the well, prior to development. When mining occurs within the precaution zone, miners should test for methane with a hand-held methane detector and probe at least every ten minutes. This zone should be free from accumulations of coal dust and spillage. Rock dust should be placed on the roof, rib, and floor to within 20 feet of the face. 2. Making sure firefighting equipment, including fire extinguishers, rock dust, and enough fire hose to reach the working face from the nearest fire tap are be available near the precaution zone while mining. 3. Ensuring sufficient supplies of roof support and ventilation materials are available near the precaution zone. 4. Checking the permissibility and servicing equipment, including the section fan, on the shift prior to when mining begins in the precaution zone. 5. Calibrating the methane monitor on the continuous mining machine on the shift prior to when mining begins in the precaution zone. 6. Advancing check survey stations to within at least 300 feet of the precaution zone prior to development near the gas well. 7. Installing sight spads (a nail made of iron, brass, tin, or tinned iron with a hook or eye at the head used to mark stations in underground mine surveying) at the last open crosscut prior to development adjacent to the gas well. The mine operator should also use sight spads to establish crosscuts forming the protective pillar. Laser or additional sights should establish the sight line for the entry or crosscut they are mining is not more than 50 feet from the projected well location. 8. Reviewing safety precautions and a drawing of the area with all personnel involved in the mining operation near the well. This should be done prior to approaching the well and throughout all shifts while developing the protective gas well pillar. Recently, a continuous miner was able to cut through a dual-cased well and its surrounding grout very easily. The abandoned, plugged well was an injection and recovery well for an underground gas storage field in Pennsylvania. G&O A portion of the well structure recovered after the continuous miner cut through it. Louisiana Ground Water Association (LGWA) LGWA.org LGWA is a unique association promoting what every association should: j Camaraderie j Education j New Techniques j Equipment j Products j Services CENEPS = LGWA.org Remember to plan NOW for the 2023 LGWA Convention and Trade Show. Contractors, this is your only opportunity to obtain Education Points for Louisiana. This association works very hard to bring you new and exciting speakers who are willing to share their “School of Hard Knocks” knowledge with you! Forms Available Online https://LGWA.org Hope to see you there!
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