Engineering & Mining Journal

JUN 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 90 of 115

PIT DEWATERING JUNE 2018 • E&MJ 89 ply, dewatering and injection wells. While these methods have the potential to drill quickly, maintaining circulation and hole integrity can be a challenge in fractured and friable ground conditions. As a result of circulation loss or collapsing bore- holes, these wells were often completed at a shallower depth than specified. Drilling a large diameter hole with either conventional air or dual rotary air can also produce a tremendous amount of discharge water. This is an issue because many drill locations cannot release water to the environment. So, the water is contained in giant sumps dug parallel to the drill rig. Often these pits fill quickly during drilling and op- erations must be stopped to allow for draining. With DTFR, the need for large sumps is eliminated because water is not discharged during drilling. This is a tremendous advantage working in-pit where water management issues can in- terrupt mining operations. Meeting the Challenge A unique situation requires a unique drilling method. Over a 1-year period, Boart Longyear drilled 2,300 meters (m) for a large mine operator in the Pilbara region with hole diameters of 17.5 in. and 20 in. The completed wells reached depths of 250 m and were cased with 10-in. to 12-in. production strings. For the development of one ex-pit dewater- ing well in particular, the DTFR reached a depth of 144 m with less than 1% of deviation during drilling. The geology the drillers encountered included banded iron, thick sequences of friable mineralized ore, and shale in- ter-bedded with hard chert bands. These changing ground conditions were easily handled by the DTFR and drilling did not stop at any point due to loss of cir- culation. Prior to the use of the DTFR in the Pilbara region, there was specula- tion that a tri-cone drill bit, which is typ- ically used on all types of mud drilling, would not be able to handle the hard rock associated with iron ore deposits. These concerns were quickly alleviated with DTFR, which helped persuade oth- er large iron ore producers to sign multi- year contracts with Boart Longyear. Jason Lamb began working with Boart Longyear in 1999 as a driller in the field. Today, Lamb manages custom- er relationships for the Boart Longyear drilling services team. His areas of expertise include water services, dewatering and reverse-circulation drilling. LESS DOWNTIME IS MORE UPTIME with CleanScrape ® Belt Cleaner LESS IS MORE WITH CLEANSCRAPE ® BELT CLEANER. Less Blade Replacements / More Blade Life – lasts up to 4x as long as traditional cleaners Less Maintenance / More Performance – only one tensioner adjustment ever Less Concern / More Confidence – safe for vulcanized and mechanical splices visit 800.544.2947 / 309.852.2384 ® Registered trademark of Martin Engineering Company in the US and other select locations. © 2018 Martin Engineering Company. Additional information can be obtained at and A GLOBAL FAMILY

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