Mechanical Mechanism And Early Warning Analysis Of Casing Shear Damage In Shale Layer

Casing damage has always been a difficult problem that plagued the major oil fields.During the development of high pressure water injection in Daqing Oilfield,casing damage,which caused by shear slip of shale in the index bed,has the trend of developing.Casing damage has affected the oil-field stable production seriously.At present,there are still many meticulous research work on casing damage,to reduce the economic losses caused by casing damage.In this paper,based on ABAQUS6.14 software platform,according to the detection well data of the Sazhong development zone in Daqing Oilfield,considering the fluid solid coupling effect,the index bed shale micro banding are simulated by the joint material and rock mass material are simulated by the linear Drucker-Prager model,has established the three dimensional mechanical model about casing,cement sheath and layer in the index bed.And compared with the actual test results of the well ZJ3-21,the numerical simulation error is within a reasonable range,verify the reasonableness of the finite element model.Based on the finite element model,has obtained the law of variation of casing stress with external load and the cumulative strain law of casing,and the external load has the greatest influence on the horizontal stress and strain of the casing.At last,using the method of control variables,the influence law of casing grade,rock dip angle,rock elastic modulus,rock permeability coefficient,different load and rock thickness on casing deformation is obtained.By extracting casing strain under various influencing factors as sample data,using MATLAB software to multiple regression,has obtained the multiple linear regression model on critical strain of casing and multivariate two polynomial regression model on predicting strain.By fitting degree,F test and residual test to verify the rationality of the regression model.Finally,the regression model of critical strain and predicted strain is incorporated into the MATLAB GUI,and the shale layer early warning template with various factors is made.The above research results provide a new research idea and a new attempt that predicting casing damage in the actual situation.