The downhole hammer attaches to the end of a column of drill pipe and cuts through rock with a rapid hammering action similar to that of a jackhammer. Downhole hammers are not new — the oil and gas and mining industries have used them since the 1950s — but the older design, with its reliance on oil-based lubricants, plastic and rubber O-rings, is not suited for the hotter temperatures of geothermal drilling.
Jiann Su, Sandia's principal investigator on the project with Atlas Copco, said: "The technology behind the new hammer is fundamentally the same, but Sandia worked with Sweden-based Atlas Copco in material selection and dry lubricant technology that will work in the high-temperature environment."
The US Department of Energy (DOE) Geothermal Technologies Office funded Atlas Copco as prime contractor on the project, and the company partnered with Sandia as the subcontractor.
"Part of what the DOE's Geothermal Program is looking to do is help lower the cost of getting geothermal energy out to customers," said Su, a researcher in Sandia's geothermal research department. "Some of reducing the cost is lowering exploration and development costs, and that's one of the areas we're helping to tackle."
The Geothermal Energy Association's 2016 annual production report said the US had about 2.7GW of net geothermal capacity at the end of 2015. In addition, the US market was developing about 1.25GW of geothermal power, and new renewable portfolio standards in states such as California and Hawaii could create opportunities for geothermal energy, the report said. Su said the high-temperature hammer could help reach those development goals.
He considers the three-year project a success, and said the team and Atlas Copco are looking for opportunities to deploy the tool.
"We developed a tool that can be used in high-temperature environments that can help increase the drilling rates and the rate of penetration to maybe 5 to 10 times that of conventional drilling operations, so that's a big plus for drillers," he said. "It adds to the available options drillers have. This is not necessarily the final option for every drilling situation, but it does provide a good option for the right situation."