The Influence of Cement Sheath Loss on Multi-layer Casing Stress in High Temperature and High Pressure Wells
Due to the complex cementing conditions in high temperature and high-pressure wells,there will be a loss between casing and cement sheath,resulting in casing damage and major accidents,especially in the case of the multi-layer casing.Taking a high-temperature high pressure and high quantity gas well in the southern margin of Junggar Basin as the research object,Based on the finite element principle and method of nonlinear contact problem of the discontinuous medium,the axisymmetric finite element model of casing cement sheath loss casing cement sheath casing formation is established by using ANSYS finite element analysis software,In this model,the hydrostatic fluid element is used at the missing part of the cement sheath,the Extended Drucker Prager constitutive model is used for the rock and cement sheath,and the contact mechanics finite element model is used for all the interfaces.The research results show that:the newly established finite element of cement sheath loss can accurately analyze the stress of cement sheath loss casing under complex conditions,and solve the problems of fluid-solid coupling at the cement sheath loss where the previous model can not simulate;when there is the annular loss between Casing and cement sheath,The maximum stress occurs near the interface where the cement sheath is missing.The lack of cement sheath and the nature of the liquid have a great impact on the casing.In deep and ultra-deep wells,it is recommended to optimize the return height of the cement sheath so that the cement sheath does not return to the wellhead,reduce the length of cementing section,eliminate the problem of cement sheath loss and ensure its wellbore integrity.In addition,maintaining reasonable internal pressure during mining is also one of the effective measures to prevent and control cement sheath loss.
absence of cement sheathcasing damagefinite elementhydrostatic fluid elementcementing quality
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