Water Well Journal
Issue link: http://read.dmtmag.com/i/681918
Air Injection The most common way to introduce air is dual wall RC pipe, available in a variety of sizes indicated in its naming convention. For instance, 7×4 dual wall pipe consists of a 4-inch-diameter tube inside a 7-inch-diameter drill pipe. Cobble in the formation can be a problem for RC pipe, Kranzusch says, but the crews haven't run into much cobble here. "The Valley has some areas of really hard clay within 5 feet or so of the surface—but with the RD20 we drill right through them." Kranzusch says RC drillers using dual wall pipe here do not have much trouble with clay balling up on the bit and plugging the returns, a problem encountered by some drillers using a conventional flooded reverse system. The capabilities of the RD20 coupled with an experienced drilling crew allow the company to provide a level of well design and completed performance for the California agricul- tural water market. Those who drill deeper holes as Belknap's customer re- quired here would also typically run into trouble with cutting evacuation. "A thousand feet or more of rock cuttings is a lot of stacked weight for RC to hold up," Kranzusch says. "Chips begin to fall back on themselves, pile together, making heav- ier masses. Then they choke off circulation." But Kranzusch had some ideas how to overcome clay and move cuttings in the deepest holes. He consulted with engi- neers, Belknap, and industry drilling experts to refine the tool string. The modifications successfully eliminated the clay and cuttings-weight issues. The drill string adaptations also sped things up. Kranzusch was on hand as one of the crews drilled an initial 17½-inch- wide bore to a depth of 1200 feet and then opened it to 28 inches. Time from start to finish was less than 40 hours. By comparison, conventionally drilled wells here at that diameter and depth take 60 to 70 hours—when drill strings don't clog, and if they don't have to sit on the hole in devel- opment for several days to get formation permeability back. Flooded RC The technique Belknap is using is actually a variation of RC called flooded reverse circulation. It's a "closed-loop" system, in which the rig recirculates drilling fluid without the need for a mud pump or shaker box. It begins with excavation of a U-shaped pit capable of holding 20,000 to 30,000 gallons of water. One side is dug as a narrow, shallow channel to serve as an intake trough. The deeper side of the pit is for collecting fluid as it returns from the hole. Cuttings settle out to the bottom. Clear water nearer the surface of the pit migrates to the intake trough, where it flows back to the wellbore again. Turning Down the Air An RD20 rig's 1250 cfm at 350 psi (590 L/s) compressor package greatly exceeds requirements in this application. So Kranzusch instructed the driller how to lower the air compres- WWJ June 2016 37 Twitter @WaterWellJournl *,.%).%/-0"3/(- 3-("-.2(*,&)!/-.,&"-)".3.2(*,&)!/-.,&"-)". For more information call: 918 - 266 -7301, or visit taylorindustries.net MEETS CALIFORNIA ANNUAL GREEN PERMIT REQUIREMENTS PUMP HOIST UNITS PH- 80 & PH-100 3*, *&-.&)$+ &.2 3.**#+",.&)$"&$%. 3)."$,."!+/!!",*+.&*)( 3". ')$"- 32!,/(& ,11*,'- Call us TODAY for a Quote and Quick Delivery! In a Hurry? OIL AND WATER continues on page 38