Abstract
Portland cements are essential components for oilfield well construction. However, these cements do not always provide the required long-lasting well barrier under corrosive downhole conditions. Also cement production emits tremendous amounts of CO2 with contributions up to 8% of the total global greenhouse gas emissions during the manufacturing process. This paper presents the first indepth durability study and successful field deployment of innovative acid-resistant cement-free geopolymer that is formulated from industrial waste by-product. The study considered different corrosive environments, including field-sourced formation brine and organic acid. In contrast to cement, geopolymers are unique 3D amorphous materials that have high potential for being a robust and sustainable alternative to conventional well barrier solutions.
For the field test, standard design and implementation workflows were used to deploy acid-resistant geopolymer systems for primary casing cementing. Pressure-matching and cement bond logs were used for post-job evaluation. A comprehensive comparative durability laboratory evaluation was conducted on geopolymer and conventional cement systems for up to a 6-month period at bottomhole temperature. A suite of analytical chemistry measurements was performed to understand the degradation process. Mechanical properties and sample weight loss were also measured after their exposure to corrosive environments.
The innovative cement-free fluid was deployed in the field using standard pumping equipment and logged using conventional sonic and ultrasonic logging tools, which confirmed superior and reliable well integrity performance. As an overview of our new findings, the geopolymer demonstrated superior durability over Portland cement in the most corrosive environment. This result was confirmed by time series weight change and compressive strength measurements. The measured mechanical properties provided important data related to the field application, i.e., the geopolymer exhibited better mechanical integrity as a downhole annular seal potentially for the life of the well. It is noteworthy to mention that the study on mechanical property is not typically included in numerous published geopolymer papers, which investigate its robustness in harsh acidic condition.
As a strategy to decarbonize well cementing, a novel acid-resistant geopolymer design is presented in this paper, which was successfully field-tested proving scalability for primary well cementing. Overall, the comparative durability study has shown that for primary cementing in highly corrosive environments, geopolymer systems can be effective and scalable alternatives to the traditional cements. Furthermore, the carbon footprint of geopolymer systems when compared to conventional cements is substantially lower; thus, even supporting industry's decarbonization drive while delivering performance.
