Environmental protection is an increasing concern for plugged and abandoned wells within the Gulf of Mexico. Leakage, however, has been shown to occur before the plug and abandonment (P&A) process takes place. The cement used when completing a well may develop leakage paths in the form of microannuli gaps between the casing and cement due to decreases in pressure and/or temperature. The goal of this paper is to use Finite Element Models (FEM) to determine the decrease in pressure or temperature required to initiate debonding of the cement sheath and the corresponding microannuli widths. Results of this paper show that there is a reduction threshold in which microannuli gaps start to initiate and increase in magnitude. A parametric analysis of the parameters within a wellbore has been performed and determined that the dimensions of the wellbore play a critical factor in microannuli gap width. With this knowledge, microannuli gap prediction graphs can be developed for different wellbore dimensions with pressure and temperature variations to determine whether a wellbore is at risk for leakage prior to P&A.

环境保护对于墨西哥湾内堵塞和废弃的油井越来越引起关注。但是，已证明泄漏发生在即插即用（P＆A）过程发生之前。由于压力和/或温度降低，完井时使用的水泥可能会在套管和水泥之间形成微环隙形式的泄漏路径。本文的目的是使用有限元模型（FEM）来确定引发水泥护套脱粘所需的压力或温度的降低以及相应的微环形宽度。本文的结果表明，存在一个减小阈值，在该阈值中微环间隙开始引发并增大。已经对井眼内的参数进行了参数分析，并确定了井眼的尺寸对微环隙宽度起着至关重要的作用。有了这些知识，就可以针对具有压力和温度变化的不同井眼尺寸开发微环隙预测图，以确定在进行P＆A之前井眼是否存在泄漏风险。