Granite-based geopolymers have shown great potential as viable and sustainable alternatives to fully replace OPC. This article shows the impact of drilling fluid contamination (both water-based and oil-based) on the rheological and mechanical properties of such a geopolymer. The mechanisms involved in contamination are also explored. The maximum contamination intake before geopolymers lose most of their strength is investigated. Optimized granite-based geopolymer is mixed with varying volumes of a typical water-based drilling fluid (5% and 10%). The resulting mixture is cured under bottom hole static temperatures (BHST) of 70℃ and 13.79 MPa pressure to simulate production casing conditions. Compressive and tensile strengths of the cured contaminated geopolymer are measured after 1, 3, and 7 days. The early strength is evaluated using the Ultrasonic Cement Analyzer (UCA). The impact of the drilling fluid on the geopolymer's microstructure is analyzed using Scanning Electron Microscopy (SEM). The results show that the geopolymer is more sensitive to the Water-Based Mud (WBM), and slurry does not develop strength after 1 day if contaminated with higher than 10% WBM. This behavior is due to geopolymerization reaction in which water remains in the system, unlike the consumption of water in OPC due to hydration. Particle sedimentation is also increased as more contamination is introduced into the geopolymer. SEM images show that after contamination with OBM, geopolymer slurry becomes an oil in water emulsion which leaves dispersed oil in pores throughout the sample after the setting phase.

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