SAFETY AND RELIABILITY EVALUATION OF CASING STRENGTH UNDER ANNULUS PRESSURE IN ULTRA-DEEP WELLS DURING OIL ANDGAS DEVELOPMENT

摘要

At present,the situation of high temperature and high pressure well annulus pressure generally appears in the ultra-deep wells.The casing damage caused by annulus pressure is increasingly serious. For the long-term service of annulus pressure situation,it is necessary to consider the impact of high temperature and high pressure environment and annulus pressure on the safety and reliability of casing and the characteristics of annulus pressure,and check the casing under high pressure.Therefore,this paper studies the mechanism and characteristics of the annular pressure,analyzes the variation of the annular pressure under different conditions,and gives the calculation methods of the closed annular pressure and the continuous annular pressure.The finite element method is used to simulate the external load and miss stress of each section of casing under the change of annulus pressure.Considering the high temperature and high pressure environment and the influence of annulus pressure on the external load, combined with the casing cement annulus formation model,the external load calculation model of each section of casing under the condition of high temperature and high pressure annulus pressure is established,and the external load of the whole life cycle of casing is established in combination with the relevant working conditions such as drilling and cementing The calculation method is used to evaluate the safety and reliability of the whole life cycle of the casing in the ultra-deep well structure in the south edge,and the relevant control measures to improve the safety and reliability of the casing are put forward in combination with the evaluation results.