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 effect of CaO reactivity on various material properties using isothermal calorimetry, Brunauer-Emmett-Teller 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 because of 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. This paper shows the successful application of CaO as an expansive agent for granite-based geopolymers at shallow depths in oil and gas wells.
This abstract is taken from paper SPE 217431 by F. D. Gomado, M. Khalifeh, and A. Saasen, University of Stavanger; S. G. Sanfelix and A.-L. Kjøniksen, Østfold University College; and J. A. Aasen, University of Stavanger. The paper has been peer reviewed and is available as Open Access in SPE Journal on OnePetro.