38 NOVEMBER 2023 WorldWide Drilling Resource® Economical Sonic Drilling vs. Rotary Drilling Adapted from Information by Geoprobe Systems® GeoTek Alaska, Inc. began with a Geoprobe® 54DT rig and environmental drilling as their bread and butter. Through the years, the company diversified by opening a second location, in Hawaii, and completing a 50/50 mix of environmental and geotechnical drilling. As the company grew, they sought opportunities to grow the technologies offered to clients, including sonic drilling. “We initially rented [a Geoprobe] 8150LS for a job on an Air Force base in Fairbanks, drilling two-inch wells to 220 feet from December through January in -30ºF (-34ºC) weather,” Scott Vojta, president of GeoTek Alaska said. “The 8150LS performed flawlessly in those temperatures. We had more problems with trucks and skid steers than we did the 8150.” The crew sampled and set a well to 220 feet in a single shift; then a second crew performed the surface completions and site preps. “It was our first sonic project and it went well and [was] completed under budget; and this was all possible because of the durability of the 8150 and the tooling,” remarked Vojta. The company wanted to purchase the rig then, but were hesitant to spend so much on a technology yet to be proven profitable in Alaska. Yet when Geoprobe® had an 8140LC in on trade, Vojta seized the opportunity to invest in sonic technology and understand where in their region sonic drilling versus rotary drilling made economic sense. “For the soils in Fairbanks, it’s conducive to use sonic to get to depth. If [using a] rotary drilling auger, you potentially break your tool string or are not able to get cuttings to return to the surface and stall out. Direct-push using an 8040 will meet refusal before depth is achieved. Thus, you have to use a tricone bit to rotary wash and develop large amounts of investigation derived waste (IDW),” Vojta said. “Sonic technology can sample and set a well to 200 feet in a day. It’s extremely fast and collects a large sample. If you do the water correctly, there’s not a lot of IDW compared to [the] rotary method.” As GeoTek Alaska has been establishing their sonic footprint, they’ve come to realize sonic drilling versus rotary drilling or direct-push can reduce the dollar per foot. “Some people think sonic costs more to run, but cost wise per foot - when it works, it’s less,” Vojta said. “We’re building a solid foundation of where it will work, and clients like it. Our piece of the pie is growing.” He admits clients are curious, but slow to warm to the new technology. “Alaska is a big state with many soil types. Clients wrestle with proven drilling methods versus newer technology, but we are building their confidence level every day. Every client has been happy it has met the scope of work. People have confidence in running the technology if we tell them the project is a good option for sonic.” They’ve been pleased with the rig’s reliability as they’ve worked to grow their sector. “The durability of the rig has been great. We’ve had very few issues in the field,” Vojta commented. That durability extends to the Geoprobe sonic tooling they run on the rig. They’ve primarily utilized the tried-and-true 4X6 sampling method, but recently purchased 6X8. “Nothing touches Geoprobe tooling - from the thread design, to the rod thickness, to the durability, and the good price. Any drill rod we use, we use Geoprobe,” said Vojta. “We’ve had a very low failure rate with few issues in the field. It’s extremely durable and runs great.” ENV
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