Theoretical Study on Working Mechanics of Smith Expansion Cone

The deformation failures of many casings are in urgent need of one reliable repair technology recently. Smith expansion cone (SEC) repair technology is high efficient to repair deformed casing. However, the reshaping force is a very important parameter for designing and optimizing the SEC and construction parameters. Hence, the mechanical mechanism of SEC repair technology is studied, and one mechanical model of SEC used to repair deformed casing is proposed based on twin shear unified strength theory in this paper. In this model, the effects of material hardening and the ratio of yield strength to tensile strength on casing repair were taken into full account. The mechanical model can calculate reshaping force that is used to repair the deformed casing under any confining pressure, and there is a good agreement between calculated results and experimental data. Based on this model, the effects of expansion amount every time, friction efficient, cone angle and length of equal diameter section on the reshaping force were analyzed in detail, by which the correlations between the reshaping force and the expansion amount every time, friction efficient, cone angle and length of equal diameter section were obtained. Research results can provide theoretical guidance for design and optimization of the structure and construction parameters of SEC.