Wellbore cement in geothermal environments is subjected to a number of mechanical, thermal (up to 400℃), and chemical (CO2, H2S, mineral acids, concentrated brines) stress regimes over its lifetime. As a result, wellbore failure at the cement lining due to thermal, mechanical, and or chemical stresses is one of the most common drivers of reservoir intervention during geothermal energy production. Wellbore intervention is expensive and time-intensive since involves production shutdowns and repairs with an average cost of $1.5 million per wellbore without taking into consideration the economic losses because of production stoppage. Similarly, long-term storage of CO2 considers very low or no leakage from the formation. Cement is not stable in a CO2 environment and becomes vulnerable when a wellbore is exposed to CO2 injected into the surrounding formation for permanent storage. To address these problems, Pacific Northwest National Laboratory has developed scalable self-healing cement formulations for geothermal and carbon storage applications with capability for full recovery of structural integrity. The cement technology is distinctly different from other competing cements because it is the only technology that: (1) offers fast ( less than 24h) and complete recovery of structural integrity and mechanical strength and over multiple damage and healing events, (2) does not require time-intensive manipulations or staff training for cement preparation and placement, (3) adheres to steel casing and wellbore rock, and (4) is resilient to high-temperature and chemically corrosive environments. This work will report on experimental as well as modeling results obtained this far on this 2020 R&D100 award winner technology.

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