Study On Integrity Of Double-layer Casing Cement Sheath

Aiming at the complex wellbore structure in drilling process,it is significant to establish a double-layer casing and cement model for the whole life of oil and gas well.Study the formation process of double-layer casing cement ring assembly and explore the guiding plan for the mechanical properties of cement stone,to ensure the good integrity of cement stone,the safe isolation of formation oil and gas water layer and the casing wall of the casing.Provide a basis for keeping the effect.In process of drilling,cementing,completion and production,the elastic mechanics method is used to establish double-layer casing and cement model considering temperature,stress and volume of cement under different working conditions.According to the mechanism of cementing,combined with the mechanical model of the double-layer casing and cement model and based on the "DR well integrity analysis software",the " mechanical performance demand analysis of cement paste " and the " integrity mechanical analysis of double-layer casing and cement" are written using C# language.By calculating the safety coefficient of cement paste and analytic solution of stress/displacement,the stress distribution of complex wellbore structure and cement paste can be analyzed more comprehensively.Combining with well structure,the mechanical demand analysis of cement paste is given.The production casing and technical casing cementing data is collocated.The failure risk of double-layer casing and cement seal is analyzed.Based on calculation results,suggestions are put forward to ensure the integrity of cement seal from the aspects of cement mechanical properties and cementing technology.