Simulation and Analysis of Sustained"A"-Annulus Pressure of Gas Injection-Production Wells Caused by Downhole String leakage
Gas injection-production wells has the phenomenon that the leakage of downhole string leads to sus-tained"A"-annulus pressure,which affected the daily normal operation.Logging tools can locate the leakage point of downhole string,but the operation is cumbersome and costly.It is necessary to conduct research on leak point parameter diagnosis based on numerical simulation,and quantitatively analyze the law of pressure in the an-nulus.The process of sustained"A"-annulus pressure caused by pipe string leakage is divided into three stages:gas leakage,"bubble"expansion,and gas column coalescence.Adopting the concept of elemental analysis,based on the theory of pressure balance and gas-liquid volume coupling,the mathematical model of"bubble"expansion is innovatively established.Combining the small hole model to form a simulation method for sustained"A"-annu-lus pressure,a software for calculating and analyzing the pressure in the A annulus of injection and production gas wells was developed.The number,depth and equivalent diameter of leakage points can be determined in reverse through parameter assumptions and fitting comparisons.The sensitivity analysis of the leakage point parameters is carried out.The research shows that the depth of leakage point mainly affects the stable pressure value of the A annulus,while the number and equivalent diameter of leakage points mainly affect the rate of pressure change in the A annulus.In the actual operation of gas injection-production wells,if multiple large-sized leakage points are generated in the shallow part of the downhole string,it would quickly generate high wellhead pressure in A annu-lus.The top leakage point should be prioritized to avoid the failure of the well barrier due to excessive annulus pressure.This study provides a new technical means for evaluating the integrity of tubing in gas injection-produc-tion wells.
gas injection-production wellspipe string leakagesustained"A"-annulus pressuremathemati-cal modelwell barrier
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维普
