Optimization of microcrack control and performance in deepwater well cementing with microencapsulated phase change materials

As deep-sea resource exploration progresses, maintaining wellbore stability and preventing natural gas hydrate (NGH) decomposition during cementing pose persistent challenges. This study clarifies the mechanisms of microencapsulated phase change materials (mPCM) in cement slurry by optimizing mPCM particle size and dosage. An efficient synthesis method was developed to produce mPCM with a polymethyl methacrylate (PMMA) shell and a hexadecane-octadecane core, followed by detailed physicochemical characterization. The impact of mPCM particle size (unscreened and 5–50, 50–75, 75–100 μm) and dosage (0–12 wt%) on Class G oilwell cement performance was assessed under simulated deep-sea conditions (15 °C, 3.5 % NaCl solution) using calorimetry, micro-CT, scanning electron microscopy, and compressive strength tests. Findings reveal that mPCM reduces hydration heat by up to 15.56 %, accelerates hydration, and shortens the induction period. Adding 4 wt% mPCM with particles smaller than 50 μm enhances cement compressive strength by 12.55 % while maintaining slurry fluidity. Smaller mPCM particles improve pore structure uniformity, decreasing porosity by 46.33 %, whereas larger particles increase pore complexity, reducing mechanical integrity. Thermal regulation efficiency diminishes when ambient temperature exceeds the mPCM phase transition onset, though minimal heat control persists. These results provide a novel approach to designing low-heat cement slurries, offering theoretical and technical insights for safe, sustainable deep-sea oil and gas extraction with reduced ecological impact.