Safety control of annular pressure in gas storage wells under CO2 corrosion
In the long-term injection-production cycle of underground gas storage wells,the annular pressure phenomenon caused by the corrosion of pipe string in the wellbore brings great challenges to the operation of gas storage wells.In order to strengthen the safe operation of gas storage wells,a prediction model of uniform corrosion and a calculation model of residual strength for tubing were established considering the influence of CO2 corrosion on gas storage well tubing.On this basis,the critical pressure value of A annulus in the gas storage well was calculated,and a control chart for the critical pressure of A an-nulus was established.The results show that in the injection-production stage,with the increase of well depth,the corrosion rate of the tubing string decreases,while the corrosion rate of the casing string increases first and then decreases.Due to the influence of formation water and ions,the attenuation of string in the gas production stage is greater than that in the gas injec-tion stage.The critical value of A annulus decreases with the decrease of the extrusion strength of tubing,and the extrusion strength of tubing is the main controlling factor of the critical value of A annulus.When the gas storage is in normal operation,the selection of tubing with thicker initial wall thickness and higher initial strength can reduce the reduction rate of the critical value of A annular pressure.The research results can provide theoretical reference for the management scheme of annular pressure in gas storage wells.
gas storage wellcorrosionresidual strengthannular pressure
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