The Prediction And Mitigation Of Annular Pressure In Trapped Annulus

The annular pressure build-up(APB)is caused by the fluid thermal expansion in sealed annulus,which is a severe risk and endangers the wellbore integrity.This paper studies the prediction model and mitigation method of APB.To predict APB,it's necessary to obtain the fluid nonlinear properties that the thermal expansion coefficient and compressibility vary with the temperature and pressure.By 2-D Lagrange interpolation method,this work obtained the water's thermal expansion coefficient and compressibility that is suitable for the APB prediction;by simulation experiments,abundant experimental data are gotten to validate the obtained fluid nonlinear properties;based on these works,a new prediction model of APB is proposed.To mitigate APB,this paper established a prediction model to obtain the optimal nitrogen quantity in the foamed spacer based on non-ideal gas equation of state.Then multigroup experiments are carried out to validated the proposed model of nitrogen quantity.Case studies and models comparison show that,the prediction model proposed in this paper can predict APB more accurately because previous models ignore the fluid nonlinear properties.The prediction model of nitrogen quantity in this work can calculate the optimal nitrogen quantity more accurately because it considers the real state of annular gas.In the end,analysis of key factors is made to provide some valuable advices for the prediction and mitigation of APB.