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PDC Drill Bits Open Up Options for Geothermal Energy

Nearly two-thirds of the oil we use comes from wells drilled using polycrystalline diamond compact (PDC) bits, originally developed 30 years ago to lower the cost of geothermal drilling. Sandia National Laboratories and the U.S. Navy recently brought the technology full circle, showing how geothermal drillers might use it.

Three decades ago, Sandia played a large role in developing PDCs for geothermal drilling. That work focused on resolving issues with materials, devising laboratory tests, and developing data and design codes that now form the basis of the bit industry. Recently, Sandia received American Recovery and Reinvestment Act (ARRA) funding to improve PDC bits, potentially increasing access to geothermal resources in the continental U.S. by enabling the drilling of deeper, hotter geothermal resources in hard, basement rock formations.

Sandia and the Navy’s Geothermal Program Office (USN GPO) conducted Phase One demonstration tests as part of a geothermal resources evaluation at the Chocolate Mountains Aerial Gunnery Range in Imperial Valley, CA. The Sandia/Navy demonstration project called for a test hole to evaluate geothermal resources in the Camp Billy Machen/Hot Mineral Spa region that would have been otherwise undetectable at the surface. The basement rock at the Chocolate Mountains includes granite and andesite, formations typically encountered during geothermal drilling.

In the tests, two bits drilled 1,291 feet of the overall well depth of 3,000 feet. The two bits were in the well just over four days, penetrating approximately 30 feet per hour throughout their drilling interval, nearly three times better than standard roller bits used for comparison. The team retrieved and downloaded downhole data from both bits for analysis. In a planned second phase of the project, Sandia will continue work with NOV to evaluate drill performance and improve the bit design and materials.

(Sandia)