Materials investigation of the high temperature IDDP-1 wellhead.

• Corrosion study of casing material from IDDP-1. • Cracking and corrosion of low to medium carbon steels is preventing its long time use in IDDP-1 conditions. • Methane cracking shown for the first time in material from geothermal well. The Iceland Deep Drilling Project (IDDP) well IDDP-1 in the Krafla geothermal field in Iceland is the most powerful geothermal well on record, with a maximum wellhead temperature of 452 °C and 140 bar pressures. In the end, the well had to be abandoned and closed permanently due to several casing failures, including a number of collapses and tensile coupling failures of the innermost casing – the production casing. The history of this first IDDP well is discussed in this paper, revealing the conditions the carbon steel was exposed to. The metal samples degrading mechanism was investigated by mechanical testing and microstructure analysis. For the first time, material used in geothermal steam in situ above 400 °C for a long period was investigated and a new alarming cracking mechanism detected. This cracking mechanism due to formation of methane inside the carbon steel structure results in severe cracks and as a result the steel loses its strength and ductility. This study reveals the need for review of material selection for high-temperature geothermal wells. [ABSTRACT FROM AUTHOR]