Controlling the heat evaluation of cement slurry system used in natural gas hydrate layer by micro-encapsulated phase change materials

Based on the low hydration heat requirement of cement slurry system used in natural gas hydrate layer and the shortcoming of traditional methods, a novel material, namely, micro-encapsulated phase change material (MPCM-1) was synthesized and used to regulate the temperature profiles and hydration heat of the cement slurry system by a physical method. During this study, the hydration heat was absorbed by MPCM-1 when the temperature of cement slurry system beyond the melting point of the phase change material (PCM), and then the hydration heat was released by the MPCM-1 when the temperature of cement slurry system drops below the crystallization point of PCM. The MPCM-1 containing low melting paraffin wax with urea formaldehyde resin shell was prepared by the method of in situ polymerization. At first, the structure of MPCM-1 was obtained by infrared spectrum analysis (FT-IR). Secondly, the phase change properties of MPCM-1 were measured by using a differential scanning calorimeter (DSC). As a result, it was shown that the melting point and heat of fusion of MPCM-1 is 23.09 degrees C and -97.49 J/g, respectively. Moreover, the thermal stability of MPCM-1 was obtained by using a synchronous thermal analyzer. Simultaneously, the surface morphology, particle size and distribution of MPCM-1 were also measured by using a scanning electronic microscope (SEM) and Laser particle size analyzer. Then, the MPCM-1 was introduced into the ordinary Portland cement slurry system to prepare a low hydration heat cement slurry system, the heat evaluation of cement slurry system were investigated by using a developed semi-adiabatic test equipment. The controlling effects of MPCM-1 on the heat evaluation of cement slurry system were investigated by the temperature profiles and hydration heat. Particularly, the temperature profiles were characterized by the initial temperature (T-in), temperature rise (T-r), maximum temperature (T-max), and the hydration time (t(max)) corresponding to the maximum temperature (T-max), respectively. Besides, the effects of MPCM-1 on the mechanical strength of cement slurry system were also studied. As a result, it was shown that the use of the synthesized MPCM-1 reduced the T-r and T-max of cement slurry system, it was also confirmed that the cement slurry system prepared by the synthesized MPCM-1 presented excellent mechanical properties.