Mechanism Of Casing Collapse Failure For Rheological Formation

In the oil field of zhongyuan, jianghan, huabei, etc daqing and other areas of our country, the oil water well casing failure and invalidated because of the rheology of the salt rock and the ooze rock, which gives rise to tremendous economical loss to the oil field exploration and development. Hence, at the foundation of the preceding investigation, according as the experimental datas and field measured datas, and on the basises of the continuous medium mechanical elasticity, plasticity, viscidity theory, from the starting point of systemic viewpoint, systemic analysis has done to the mechanical mechanism on casing failure and invalidated. First do research on the collapse resistance intensity of casing under complicated working condition, then do research on the measurement of identity and mechanical property inversion of salt rock rheological models, at last estabalished the models of which rheology coupling under uniform formation stress and elasticity contact coupling under non-uniform formation stress of the formation cement band and casing system, and then do research on the mechanical characteristics. The idiographic content as follow:(1) On the casing collapse resistance intensity: Do research on the measurement of collapse resistance strength of crescent-shapes wear of casing with considering residual stress under uniform loading; established and explained mechanical models of collapse resistance analysis which the casing under non-uniform collapse on radial and non-uniform cut on loop, analyzed the casing stress distributing rule which under non-uniform loading, and bring forward non-uniform loading equivalent to uniform loading, thereout give the measurement of collapse resistance margin under non-uniform loading, and workout correlative programme.(2) On the rheological formation mechanical property: It bring forward identified measurement on salt rheological models with the basises of well diameter measured information, apply the method of least square and then established the objective function to identify the constitutive models, and aimed at the idiographic measured datas then bring forward measurement inversion to eliminate thick error. And then workout the computational programme to identify the salt rock rheological models and mechanical property inversion, well hole diameter shrinking rule.(3) Formation, cement band and casing elasticity-viscoelasticity coupling: Established and explained elasticity coupling mechanical models of the formation, cement band and casing which consider the initial creep deformation underuniform formation stress and combination system elasticity coupling mechanical models which consider formation, cement band and casing boundary contact. Then workout analytical programme of formation, cement band and casing viscoelasticity coupling mechanical models under different formation stress and different boundary contact. Analyzed the casing strength effect which formation mechanical property, cement band geometry and physical property casing geometrical property had on. The primary innovation of the paper:(1) Bring forward the measurement of the collapse resistance strength for wearing casing which consider residual stress and the measurement of the collapse resistance margin for casing which had non-uniform collapse on radial and had non-uniform cut on loop.(2) Bring forward a measurement of distinction of rheological model for the salt rock rheological models on the basises of well diameter measured information, and bring forward measurement inversion to eliminate thick errors which aimed at the idiographic measured datas.(3) Based and explained formation, cement band and casing viscoelasticity coupling mechanical models which consider the initial creep deformation and elasticity coupling mechanical models of the combination system which considering boundary contact under non-uniform formation stress.