Preparation and action mechanism of temperature control materials for low-temperature cement

Abstract

Encountering natural gas hydrate (NGH) is inevitable in the process of drilling and the production of oil and gas wells in deep-sea and shallow formations. The heat released by the cement slurry during the hydration process will cause the decomposition of gas hydrates, which will lead to annular channelling. Our purpose is to improve the cementing quality and ensure the safety of oil and gas production. In this paper, temperature control phase change microcapsules (PCMCs) with dodecanol (DA)/n-decanoic acid (CA) composite phase change materials (PCMs) as the core and active silica as the shell were prepared by a chemical precipitation method to store and release heat reversibly, to reduce the hydration heat of cement and improve the early strength. Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrometry (EDS) were used to test and analyse the chemical structure and microscopic morphology of the synthesized temperature-controlled phase change microcapsules. Differential scanning calorimetry (DSC) was used to determine the phase change characteristics of the phase change microcapsules. The thermal stability of the phase change microcapsules was measured by a thermogravimetric analyser (TG). The application of PCMCs in a low-temperature cement slurry was also investigated. The results showed that the synthesized microcapsules had good thermal stability with a phase transformation temperature of 12.4 ℃ and enthalpy of 1.65 J/g. PCMCs can effectively control the hydration heat of cement and reduce the rise of hydration temperature by 6.06% to 11.79%. In addition, PCMCs can slowly release heat to promote the hydration of cement in the later strength development, and improve the early compressive strength of cement in the range of 5 ℃ to 10 ℃.