Water Well Journal

July 2015

Water Well Journal

Issue link: http://read.dmtmag.com/i/529509

Contents of this Issue


Page 28 of 83

T roy Alexander wanted no part of a three-day rainstorm coming his way in mid-May. Finishing up a 200-foot domestic water well in Veeders- burg, Indiana—the last thing Alexander needed was to be caught stuck in rain with his 1978 George E. Failing CF15. It didn't happen. All because Alexander followed what he has learned and applied over the years since he began drilling in 1994. "You've got to be thinking ahead, so I'm going to take an extra five minutes to do maintenance to make sure I've got the proper bit," says Alexander, driller for Findlay Bros. Well Drilling in Covington, Indiana. "If you've got a broken bit just to limp by, then all of a sudden you're sidelined and you've lost half a day. It's as sim- ple as taking the 20 minutes to change the bit and make the hole and be done." Thinking ahead enabled Alexander to beat the rain so he could oil, grease, and complete other upkeep of the rig back at the shop. It's a testament of the little things going a long way. As president of the Indiana Ground Water Association, Alexander sees proper bit maintenance as commonplace. Water well contractors who are in a rush to get a hole done may neglect it. It's no coincidence this timeless topic of proper bit selection for different types of formations is covered regularly at the National Ground Water Association's Groundwater Expo and Annual Meeting. In this article, water well contractors and drill bit manufacturers share their thoughts on choosing the right drill bit. Selecting the right drill bit can depend on the geologic for- mation one is encountering—among other factors, requiring patience while adhering to a trial and error mind-set. In Alexander's area, 80 miles northwest of Indianapolis near the border of Illinois, he predominately uses a tricone roller carbide bit through clay. He works in a 70-mile radius from Covington and drills both in unconsolidated and consoli- dated formations using the mud rotary drilling method. For unconsolidated formations, Alexander prefers an 8½- inch tricone roller bit with carbide buttons rather than the steel tooth. This bit, Alexander says, can drill through boulders faster and they don't wear out. In consolidated formations (shale, sandstone, limestone), he'll switch to a 4¾-inch polycrystalline diamond compact (PDC) bit to drill though bedrock. "Once we get the casing set, we'll drill just an open hole into the bedrock," Alexander says. "That will just fly through the rock formations in our area. That's sped up the drilling just dramatically. We can drill several feet a minute versus a lot slower rate with just a roller cone bit." Some contractors are forced to switch to a hammer bit for limestone in Alexander's area, but he doesn't have hammer capability on his table-drive, four-speed transmission rig—so the PDC is his choice. Typically, Alexander sees six months of life with a bit. "It's one of those every hole you drill and how many boul- ders you have to drill through, you kind of just have to keep checking to see how the bearings are and see if you're missing the carbide button teeth," Alexander says. "The teeth will actually break out of it, so it's a daily maintenance of looking at the bit itself to see if it's time to replace it." An important pre-drilling check Alexander follows is in- specting the different holes in the bit itself for water and air to flow through it. Any obstructions in the bit could cause it to become plugged, forcing the contractor to trip out of the hole. The roller bits should spin and rotate completely. If they can't rotate, a locked bearing might be the culprit. "If you don't do that five- to 10-second look at the bit, it'll cost you hours' worth of labor to get back to that point," says Alexander. In western Michigan, the size of the permanent well casing Wahlfield Drilling Co. intends to set in place primarily dic- tates the size of the drill bits it uses. The Michigan Depart- ment of Environmental Quality's well construction code also has guidelines for bit size for each individual casing size. Common in the area is the use of 5-inch polyvinyl chloride (PVC) casing. With it, Wahlfield Drilling uses an 8¾-inch tricone roller bit, which leaves room for casing centralizers, gravel pack sand, and casing grouting. Its screens are either telescoped or attached to the casing in its sand/gravel aquifer formations. "If the well is going to be completed in the bedrock aquifer, we will try to set casing as soon as we are sure we're in the bedrock and grout it into place," says Mike Wahlfield, whose company uses mud rotary and cable tool drilling meth- ods. "Then we will drop back to a smaller bit and drill through the inside of the casing until total depth is reached." Wahlfield says for their 4-inch steel casing with cable tool drilling, they typically use a 4-inch-diameter standard chisel style bit with a hard surface weld built up on the tip. "If we are going to complete the well in the bedrock aquifer formation, we will typically switch up to a 4-inch car- bide button bit, along with a wing-style mixing sub. We would also use a set of scissor-style drilling jars below the wire rope socket to help us dislodge our drill string, if it should happen to get stuck." Water well contractors have the luxury of seeking expertise from drill bit manufacturers when necessary. Kevin Christensen, president of Palmer Bit Co. in Willis- ton, North Dakota, sees a large majority of water well contrac- tors adhere to a rigid mind-set. The line of thinking follows "This bit has worked for years, so why change?" As a presenter on drill bits for various drilling formations at state shows and the NGWA Groundwater Expo and Annual Meeting, Christensen focuses on the bit cost per foot, among other things. The key is to drill faster at a lower cost per foot . DRILL BITS continues on page 28 WWJ July 2015 27 Twitter @WaterWellJournl

Articles in this issue

Archives of this issue

view archives of Water Well Journal - July 2015