Mechanism Analysis And Prevention Measures Of Casing Damage In Zhongyuan Oilfield

With the adoption of various enhanced oil production measures,the working conditions of casing of oil and water wells have become more and more deteriorated, and nearly all oil fields are now confronted with a universal problem:casing damage, which is increasingly aggravated year by year and brings about enormous loss of manpower, material resources and financial resources to oilfield.The casing damage of Zhongyuan oilfield has been comprehensively analyzed in this paper, where the mechanism of casing damage and the casing damage repairing technology has been discussed. According to the cause of the casing damage, and more effective prevention measures are suggested to control the casing mechanics damage. According to the theory of elastic-plastic mechanics, the relationship between casing deformation and the load and heterogeneity of in-situ stress is studied in a formation-cement-casing system by establishing nonlinear finite element model. The relationship between the external load and casing deformation is analyzed under different conditions in this paper. According to the result of finite element analysis, the chart of casing deformation versus maximum and minimum earth stress is mapped, from which casing deformation under non-uniform in-situ stress can be predicted conveniently. This result can provide a reliable guide for casing damage prevention measures and subsequent well-repairing construction operation.The shaper device has been often used to repair the casing deformation well. Conforming the repairing force in the repairing progress is a complicated problem for the mechanics of elastic and plastic、geology mechanics、repairing material mechanics and material strength theory etc. several courses and realm. According to the Von Mises equivalent stress strength basis, the maximum of equivalent stress in casing body in the process of recovering the damage casing, is equal to or greater than the yield strength of casing materials, which shows that the casing under the function of pressure has reached the yield state, when continuing repairing, it would aggravate the casing damage; If the maximum of equivalent stress in casing body did not reach the yield strength, the change of the greater level of the shaper device again. By using the finite element modeling, simulating the process of shaper device of small diameter taper repairing the deformation casing, and determine the minimum of repairing boundary and the repairing force in the repairing progress, which has great important guiding significance on the field work in the operation of repairing the casing deformation well.