Changes in ultra-deep and ultra-high-temperature drilling projects and associated technology development

Abstract

Although ultra-deep and ultra-high-temperature drilling projects such as Kola superdeep borehole, German KTB project and Kakkonda WD-1a deep geothermal drilling were implemented in the past, such challenging drilling projects seemed to disappear for the last 10 to 20 years. In this paper, the past ultra-deep and ultra-high-temperature drilling projects and the associated technology developments, and the national project on supercritical geothermal system development just started this year are overviewed.