Synthesis and evaluation of inorganic-organic composite phase change materials for large temperature difference cementing

Slow strength development of the top cement stone is an issue in long-segment cementing operations. In this study, an inorganic-organic composite phase-change early-strength material (NSS) has been prepared by the sol-gel method. The structure of NSS was characterized by X-ray diffraction (XRD) and Fourier Transform-infrared (FTIR) spectroscopy. In addition, thermal stability and phase transformation were evaluated by thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). The NSS material exhibited an irregular spherical shape, with a relatively uniform particle size distribution; median particle size = 4.12 μm. The initial thermal decomposition temperature was 192 ℃, with phase change endothermic temperature of 59.74 ℃ and an exothermic temperature of 53.64 ℃. The cement slurry containing NSS delivers superior temperature-resistance and retardation at 150 ℃. The thickening time can be adjusted, where the associated curve is stable without any observed abnormal phenomena such as "bulging". The 24-h compressive strength of cement containing 1.5 % NSS at 50 ℃ was 175 % higher than the blank group. The addition of NSS increased the cumulative heat release and total amount of hydration products, and optimized the pore structure. The findings of this study have established that NSS effectively addresses the slow development of low-temperature cement slurry strength in large temperature difference well cementing via a mechanism involving physical filling → chemical enhancement → temperature buffering → pore optimization. • Novel composite phase-change material (NSS) was developed via sol-gel method for large-temperature-difference cementing. • NSS exhibits excellent thermal stability (192 ℃) and phase-change properties (59.74 ℃ endothermic, 53.64 ℃ exothermic). • NSS significantly enhances early strength (175 % increase in 24 h compressive strength at 50 °C). • A multi-level mechanism (physical filling → chemical enhancement → temperature buffering → pore optimization) is revealed. • NSS demonstrates good compatibility with high-temperature retarders, ensuring safe and adjustable thickening time.