Experiment Study on the Cement Hydraulic Pressure Evolution Law in Closed Environment

With the implementation of drilling and production of deep wells, liner cementing can effectively save operating costs, and ensuring the quality of liner cementing is the key to ensure the safety of drilling, completion and later production of oil and gas wells. After the cement slurry of the oil well is pumped into the formation, its hydration and solidification process are accompanied by the decrease of its own hydraulic pressure, that is, the phenomenon of “weightlessness” of the cement sheath occurs. In the process of liner cementing, the setting seal of the liner hanger will block the downward transmission of the pressure of the upper liquid column, which is likely to cause more serious condition of cement slurry pressure decreasing, and then increase the risk of cement gas migration. In this study, a pressure monitoring device was designed and fabricated in the closed environment, which can realize real-time monitoring of pressure evolution and volume change during cement hydration and solidification of oil wells under different overlying pressures and temperatures. The results show that under open conditions, the hydraulic pressure of cement during solidification will show the characteristics of stability-rapid decline-stability, and the volume of cement will show the characteristics of slow-fast-slow contraction, while in the closed environment, the hydraulic pressure of cement will decrease more rapidly, and the volume shrinkage rate of cement will show a stable state. The research results can provide theoretical basis and engineering guidance for optimizing cement slurry formulation and improving cementing quality.