Diamond Bits for Geothermal Drilling Adapted from Information by Sandia National Laboratories Researchers at Sandia analyzed drilling records from the Frontier Observatory for Research in Geothermal Energy (FORGE) to develop guidance for selecting the most suitable drill bit for geothermal well drilling, considering factors such as location and depth, to minimize drilling costs. Located in southwestern Utah, the FORGE field laboratory is a Department of Energy (DOE) funded facility focused on testing geothermal technologies to reduce risks and accelerate commercial viability. The FORGE site, managed by the University of Utah, saw the drilling of four wells using polycrystalline diamond compact (PDC) bits, which utilize lab-grown diamonds in disc-shaped cutters to effectively cut through rock. “At the FORGE site, a number of wells were drilled to depths of approximately 10,000 feet, and they were largely drilled by polycrystalline diamond compact bits,” said David Raymond, a Sandia Mechanical Engineer and leader of the analysis. “This is one of the largest applications of diamond bits for geothermal drilling in their 40-year history. We produced a compendium of all the drill bits used and how they performed.” David and his team, with Mechanical Engineer Melanie Schneider, analyzed daily reports from the FORGE site to collect four critical parameters: the force applied to the drill bit, rotation speed, drilling speed, and required power. These values were used in a computer model to simulate the interaction between the drill bit and rock, and compare it to a standardized diamond cutter. “Two things afforded FORGE the ability to drill with these advanced diamond bits,” said Doug Blankenship, a Sandia geothermal expert on detail with DOE’s Geothermal Technologies Office as a senior adviser. “One is the advanced technology that the bit companies have developed so that the bits are more capable of drilling in hot, hard rock. Two is the approach to running these bits that Fred Dupriest and Sam Noynaert from Texas A&M brought to the drilling program.” In addition to examining cost constraints, the Sandia team investigated the balance between drilling speed and distance drilled, as well as how it affects the cost per foot drilled by each bit. David pointed out drill rig rental is a significant daily expense in geothermal well drilling. Melanie cautioned faster drilling isn’t always the most cost-effective approach. As David explained, a slower, steadier approach may be more costeffective, depending on the depth and time required to replace a bit. “A big cost is truly how long it takes to get in and out of the hole when you’re at depth,” Melanie said. “A key takeaway from our reporting is it’s not necessarily about going fast or with more force; it’s about trying to extend the bit’s life and getting the most out of each one. We’re already seeing a huge improvement in drilling performance throughout the course of the four wells at FORGE.” Melanie Schneider holds a PDC bit. Photo courtesy of Craig Fritz. Frontier Rig 16 was used to drill wells. GEO Looking for GREAT DEALS? WorldWide Buyers Guide - in the back of the magazine! 39 APRIL 2025 WorldWide Drilling Resource®
RkJQdWJsaXNoZXIy NDk4Mzk=