Preparation and characterization of intelligent temperature-control microcapsules for natural gas hydrate bearing sediment

Abstract The friction heat generated during the drilling process of natural gas hydrate bearing sediment (HBS) leads to the temperature of drilling fluid higher than the phase equilibrium temperature of hydrate, which induces hydrate decomposition and wellbore instability. In this work, tetrabutylammonium bromide (TBAB) and Nano-silica were microencapsulated by inverse emulsion interfacial polymerization. The effect of different preparation conditions on the encapsulation rate of microcapsules was characterized by differential scanning calorimetry (DSC), and the highest encapsulation rate was 62.2% with the melting enthalpy of 121.4 J/g. Polarizing microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM) images were used to characterize the synthesis process and microstructure of microcapsules, which proved a quasi-spherical structure coated with Nano-silica. Furthermore, it was confirmed that the microcapsules also had good thermal conductivity, reliability and thermoregulating performance. The rheological parameters of drilling fluid with 5 wt% microcapsules increased slightly, and the filtration loss decreased, indicating good compatibility. In addition, it is convenient to adjust the melting temperature of the core materials by adding NaCl with different concentrations. This study is of guiding significance to realize intelligent temperature-control of hydrate bearing sediment during drilling.