Cementing casing in a super-hot, 350 – 500°C, geothermal well is a very important part of well construction operation. Failure to properly place cement can leave cement voids which can increase the risk of mechanical failure of the casing due to lack of support. Mechanical failure of the cement due to cyclic stress loading can expose the casing to aggressively corrosive fluids from the formation. Super-hot temperature environment can pose challenges in cement placement and long-term durability of the cementitious material. Large temperature ranges from the top to bottom of the column of cement can pose challenges in getting the cement successfully placed and then harden after placement.
The content of this paper will focus on keys areas of technical challenge, discussing the current state of the art, identifying the gaps in knowledge and practice, and finally recommendations for what is needed for future research and development. The paper will include discussion of the unique challenges of geothermal well cementing and how they become even greater for super-hot geothermal development. The topics covered in the paper will be subsurface conditions, existing cement systems, thermal and chemical durability, mechanical stress due to thermal cycling, cement placement issues, and alternative materials.
Conclusions and recommendations for what is needed in the future to develop super-hot geothermal power will also be provided.