Analysis on Casing Deformation and Buckling Risk in Sand Production Section of Thermal Recovery Horizontal Wells
Considering the impact of sand production from reservoir on casing deformation and stability in thermal recovery wells,a test was conducted to investigate how high temperature steam affects the rock properties of heavy oil reservoirs.Combined with heat transfer and heat-solid coupling theories,2D casing-cement sheath-forma-tion and 3D casing buckling models were built to analyze the active mechanism of sand production from reservoirs on the casing deformation and buckling during heat injection process,and the influences of different sand produc-tion severities on casing deformation and buckling were compared.The results show that in case of sand production from reservoir,the casing is subjected to both thermal stress and circumferential nonuniform ground stress,resulting in inner wall yielding.As the sand production expands,the plastic deformation gradually increases.When the sand production aggravates to cause formation voidage,the casing in the sand production section is less supported by the reservoir rocks,and there is a risk for the axial thermal stress resulted from heat injection to cause casing buckling.Given the steam injection temperature of 350℃,when the formation voidage section length is less than 3 m,there is a risk of casing buckling;when the formation voidage section length is 4 m,the axial force of casing reaches a critical buckling load(4 876.9 kN)in the heat injection process,corresponding to a critical buckling temperature of 304.9℃,so that there is a risk of casing buckling,and as the formation voidage section length in-creases,the critical load and corresponding temperature for the casing in the sand production section to buckle sig-nificantly decrease,exacerbating the risk of buckling.The research results provide theoretical guidance for sand control and casing selection of thermal recovery wells.
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