Effect of Calcium Expansive Additives on the Performance of Granite-Based Geopolymers for Zonal Isolation in Oil and Gas Wells

Geopolymers have emerged as a promising alternative to Portland cement for oil and gas wells. Achieving effective zonal isolation by use of geopolymers may require controlling their expansion. This study investigates the effect of calcium oxide (CaO) as an expansive agent on the performance of geopolymer-based sealing materials. Specifically, we explore the impact of CaO reactivity on various material properties using isothermal calorimetry, Brunauer-Emmett-Teller (BET) surface area analysis, linear expansion (LE) test, shear bond strength, compressive strength, and hydraulic bond strength (HBS). Our results indicate that CaO reactivity is a critical factor affecting the properties and performance of geopolymers for zonal isolation. Lower reactivities are associated with longer induction periods and lower heat evolution, which in turn increase LE. While lower reactivity decreases compressive strength, it increases shear bond strength. However, the CaO with the lowest reactivity resulted in a very low HBS due to matrix cracking and leakage. Therefore, optimizing the reactivity of CaO expansive agents is essential to enhancing the properties of geopolymer-based sealing materials for oil and gas wells. Shown in this paper is the successful application of CaO as an expansive agent for granite-based geopolymers at shallow depths in oil and gas wells.