Research On Double Casing Of Collapse Strength After Patched By Expandable Tubular

As a common technique for repairing casing damaged wells,the expandable tubular technology greatly improves the casing collapse strength after patched and greatly reduces the casing collapse.However,there is no standard calculation method for the collapse strength of expandable tubular after expansion,and there is no accepted calculation method for the collapse strength of the casing after expandable tubular patch.Therefore,this paper studies the collapse strength of the casing after patched by expandable tubular.In this paper,based on the theories of elastic-plastic mechanics and contact nonlinear analysis,the explicit dynamic analysis module is used to perform finite element simulation and analysis on the expansion process of 55 ksi expandable tubular with expansion rates of 6.3%,11.2% and 17.1% respectively,and then to study the geometrical size of the expandable tubular under the three expansion ratios,circumferential residual stress and circumferential compressive yield strength in the tubular body are obtained.For the three kinds of expandable tubulars after diameter expansion,the buckling analysis method was used to calculate the collapse strength of the expandable tubulars after diameter expansion,and the buckling analysis results of the collapse strength of the three expandable tubulars after diameter expansion were compared.At the same time,the influence of the expandable tubular’s geometrical size,circumferential residual stress and circumferential compressive yield strength on the collapse strength of the expandable tubular after expansion is analyzed.For the double casing formed after patched by expandable tubular,the buckling analysis method was also used to calculate the collapse strength of the double casing and the collapse strength of the outer casing.The results of strength buckling analysis were compared,and the effects of the annulus gap between the double casing and the above three factors on the casing collapse strength after expandable tubular patches were further analyzed.The sum of the collapse strength of the inner expandable tubular and the collapse strength of the outer casing was compared with the collapse strength of the double casing after the expandable tubular was patched.In this paper,the collapse strength of the expandable tubular under the three expansion ratios after expansion,the collapse strength of the outer casing and the casing collapse strength after the expandable tubular patch are obtained.The casing collapse strength was compared and analyzed.It was found that the casing collapse strength after patching the expandable tubular was significantly higher than the sum of the collapse strength of the inner and outer casings,and the buckling analysis results of the collapse strength of the double casing comparing the graphs,it is found that the greater the expansion ratio,the closer the collapse strength of the two.The annulus gap between the double casing,the geometrical size,the circumferential compressive yield strength after expansion of the expandable tubular and the circumferential residual stress of the pipe body have significant effects on the casing collapse strength after the expandable tubular is patched.