Novel Corrosion-Resistant and Sustainable Cement-Free Well Cementing Solution: From Laboratory Design to Yard Test

Abstract

Abstract In this paper, we present an in-depth durability study of a novel geopolymer (GP) cement-free system for acidic high-sulfate formation brines. We report its scale-up performance for wellboreapplication through a successful yard test using standard cementing equipment to pump the new fluid system. In contrast to high carbon-footprint cement, GPs are unique 3D amorphous materials that have high potential for being robust and sustainable alternatives to conventional well barriers. Because of their complex nature and chemistry, GPs could not be designed in the past for downhole conditions of temperature and pressure that we encounter during well construction. Now, with significant research carried out in this field, we developed chemistries that allow for successful use of GPs for well construction. Comprehensive comparative durability evaluation was conducted on GP and conventional cement with corrosive formation fluid. Analytical chemistry measurements, imaging techniques, and mechanical property testing were performed to understand the performance of both materials. To test for scalability and equipment compatibility in the field, the innovative GP design was blended in the bulk plant followed by mixing and pumping the slurry using a cement pumper unit to simulate the actual job. The study also covered the formulation optimization of the new GP design to meet the different wellbore requirements. As an overview of our findings, GPs demonstrated superior durability over traditional cements in simulated formation brine (pH 4 to 5) with ~45,000 ppm sulfate. This result was confirmed by computerized tomography (CT) scan imaging, weight loss, and compressive strength measurements. The measured mechanical properties provided important data related to field application; i.e., GPs exhibited better mechanical integrity as a downhole annular seal. It is worth mentioning that the study on mechanical properties is not typically included in numerous published GP papers, which investigate its robustness in harsh acidic media. The job chart for the successful mixing and pumping on-the-fly of 30 bbl of GP slurry in the field by standard cement pumper units demonstrated a stable fluid system equivalent to traditional cement. GPs are a novel class of materials that here, for the first time, have been customized for use in wellbore construction with even more challenging conditions such as highly corrosive environments. Aside from presenting new knowledge to evaluate the material’s performance, in this paper we also prove the field scalability and standard equipment compatibility of this innovative corrosion-resistant GP design. Finally, the carbon footprint of GP systems when compared to conventional cements is substantially lower, thus supporting the industry’s decarbonization drive while delivering performance.