Influence of the Characteristics of Cement Plug on well Integrity for Offshore Abandonment

Abstract

With the development of offshore oil fields into the middle and late stages, more and more oil wells are facing the problem of disposal. The reliability of the plugging between the cement plug and the wellbore is directly related to the safety of offshore operations and the problem of marine ecological damage caused by oil and gas leakage. Starting from the cement failure mechanism between the cement plug and the casing, consider the heterogeneity of the formation and the magnitude of the ground stress. The finite element software is used to simulate the interaction between the cement plug and the casing with different characteristics, and then judge the risk of sealing failure. Furthermore, the influence of cement plug properties on casing stress and cementation strength is obtained. Study show that the use of high strength, low modulus of elasticity, low Poisson's ratio cement is conducive to prevent cement plug tensile failure. When the local layer is hard, the method of reducing the elastic modulus of the cement plug can be adopted; and when the local layer is soft, the method of appropriately increasing the elastic modulus of the cement plug should be adopted. It has certain guidance and reference significance for the safe disposal of offshore wellbore.