Research On The Influence And Prevention Of Thermal Recovery Well Casing Damage Based On Multi-factor Coupling

Today heavy oil resources is abundant,steam injection method as the main production approach has been widely used.However,the failure rate of casing in oil thermal recovery wells is increasing year by year.Casing damage has been a technical problem exists in oilfield development,coupled with the factors of more complex mechanism of interaction between various factors that cause casing damage,less theoretical research on tool repaired casing damage.It caused huge losses to oilfield,seriously affected the oil production and economic benefits.Based on it,non-uniform stress,the high-temperature and high-pressure,casing-cement ring itself quality and other factors were thermal coupled, the mechanism of casing damage under the influence of these complex factors has been studied systematically.The corresponding casing damage prevention and control measures combined with the analysis is put forward.This article mainly finishes the following research work:(1) Establish the coupling system model of casing-cement-formation under non-uniform stress,analytical solutions of casing stress and displacement fields are derived by using elastic-plastic mechanics theory.In particular,analysis wear casing under the non-uniform stress,obtained casing stress distribution under non-uniform stress.(2) Establish thermal stress finite element model of thermal recovery well casing under the coupling of multiple factors,establish casing temperature and stress field at different factors.Analysis casing damage mechanism in non-producing layer and the layer at the production.Casing safety of orthogonal experimental design for important factors of heat recovery wells,analysis each parameter sensitivity to determine the level of significance under the effect of various parameters. Obtained a function of significant factors and thermal stress,and the quantitative relationship cloud is given,based on it prevention measures of damage thermal recovery casing is proposed.(3) Research the cement defects on damage thermal recovery casing,in particular analyze the impact of gas passage missing accounting and circumferential missing.Cement gas passage missing accounting and circumferential missing depth have larger impact on casing stress in thermal recovery wells,the maximum Mises stress of casing increases with the higher of cement gas passage missing accounting and circumferential missing depth.(4) Casing oval deformation was induced by non-uniform stress.Based on it,it presents a controlled anti-seize casing shaping device in oil and gas well which its'structure is simple, good sealing and lubricating properties.lt can be controlled by providing a reasonable ground pressure.(5) Derivation the shaping force and tool range based on Mohr integral theory when it's shaping,and with a real value corrected theoretical value.The residual stress of casing repairing model was deduced in the use of Elastic-plastic theory.The distribution of the longest residual stress band was drawn up based on ABAQUS finite element platform.The slider cone angle is recommended to select within 70°?80° based on the residual stress theory.Research on casing damage factors and mechanisms,and propose targeted casing damage prevention measures is of great significance for the late production oilfield.Therefore,this study is not only has theoretical significance,but also has practical value.