Water Well Journal
Issue link: http://read.dmtmag.com/i/681918
Reverse Circulation The switch from drilling in the oil patch to drilling water wells didn't require a major change in tooling or technique, and Kranzusch recommended adapting the RD20 for reverse circulation. First designed for exploration using air rotary in the 1970s, a burst of tooling innovations made reverse circulation possi- ble for nearly every kind of drilling in any kind of drilling conditions. In some areas of California, it means using rotary mud in the first 50 to 150 feet of unconsolidated sediment through granite bedrock at its bottom. Kranzusch explains the benefits of using reverse circula- tion (RC) for water wells vs. conventional mud drilling. "When you drill for oil using what we call 'direct drilling technique,' you actually want mud to cake the hole walls," he says. "It helps maintain the hole walls as fluid and cuttings flush up the annulus until you can case it off from the aquifer to isolate it from the bore. Reverse circulation lets you drill in an aquifer without reducing the inflow of water. This keeps a clean and undisturbed borehole as desired for water wells." The group worked together to analyze the target formation geology, the drilling methods, and the well design objectives to establish the optimum method and process for completing the highest quality and performing wells in the region. As for maintaining wall stability, RC can actually be more effective in certain formations than conventional mud drilling. Kranzusch explained that is because cuttings go up the pipe, not against the borehole wall. This also can lead to less time spent on developing the well. Fluid return filled with cuttings is a prime cause of hole wall deterioration. But the drilling fluid in an RC situation has no cuttings in it. It is merely present in the annulus, migrating toward the bottom of the hole where it will be siphoned up the pipe, so there is also much less agitation. Siphoning is assisted by injecting air at the hole bottom. The air reduces fluid density in the pipe. The difference in hy- drostatic pressure between the fluid column outside the pipe and the less dense fluid inside it causes the fluid to percolate up the pipe, carrying cuttings with it. Scottie Belknap, a fourth generation well driller who manages the company's drilling operations with his father Scott Belknap and mother Marilyn Belknap. OIL AND WATER from page 35 waterwelljournal.com 36 June 2016 WWJ