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Abstract An innovative approach is required in the energy industry to address the well cementing process in order to minimize the operation's carbon footprint. Typically, ordinary Portland cement is used as a well barrier to isolate oil and gas wells. The energy-intensive manufacturing process of Portland cement creates approximately 1 metric tonne of carbon dioxide emissions per metric tonne of cement produced. This paper discusses a cement-free geopolymer technology that can be used as a cement replacement and tailored for different well conditions. The formulations discussed in this paper reduce the embodied carbon emissions compared to a traditional cementing job, while also providing slurry and set properties adequate for isolation. The objective of this paper is to present two case histories of this unique cement-free geopolymer technology. These were the first jobs pumped using this technology in Europe, and the paper will detail the fit-for-purpose design methodology, as well as the job preparation, yard trial, and field execution. The geopolymer system discussed in this paper has been applied in over 750 jobs globally in various configurations, including plug and abandonment. The aim of this particular project was to demonstrate that the cement-free geopolymer technology is scalable and versatile across a range of conditions while providing slurry and set material properties that permit it to perform as an adequate wellbore barrier in the European market, as well as following industry guidelines such as API (American Petroleum Institute) Recommended Practice 10B-2. Four separate geopolymer slurries designed for plug and abandonment operations were optimized for different well conditions, including varied temperatures due to uncertainty in plug depth. Once optimized in the laboratory, the scalability of the geopolymer technology was assessed by preparing the material using conventional cementing equipment in three different locations in Europe. The flowability and homogeneity of scaled bulk plant blends of varying designs were verified by collecting multiple samples for analysis and comparison with laboratory-prepared blends. A yard trial demonstration of bulk mixing and pumping these fluids using conventional cementing equipment was completed in one country, and then plug jobs were successfully executed and verified in two other countries’ field locations in Europe. The cement-free geopolymer system demonstrated reliable adaptability to varying well conditions, consistent performance, and compatibility with conventional cementing equipment and workflows. Field operations successfully mixed, pumped, and verified the plugs, validating that this cement-free geopolymer technology can be deployed at scale. Replacing Portland cement with geopolymer materials offers a viable path toward more sustainable wellbore barrier systems, reducing environmental impact while preserving the high fluid performance and operational simplicity required in the field.