In this paper, we present an analytical method for evaluating the stress field within a casing-cement-formation system of oil/gas wells under anisotropic in-situ stresses in the rock formation and uniform pressure within the casing. The present method treats the in-situ stresses in the formation as initial stresses since the in-situ stresses have already developed in the formation before placement of cement and casin  (本文共22页) 阅读全文>>

A multi-casing structure in drilling engineering can be considered as an inhomogeneous body consisting of many different materials. The mechanical behavior of the inhomogeneous body in an infinite domain is very complicated. In this paper, a detailed expression about the fictitious stress method of the boundary element method(BEM) is demonstrated for the inhomogeneous body. Then the fictitious stress method is deploy...  (本文共12页) 阅读全文>>

Casing corrosion during CO_2 injection or storage results in significant economic loss and increased production risks. Therefore, in this paper, a corroded casing risk assessment model based on analytic hierarchy process and fuzzy comprehensive evaluation is established to identify potential risks in time. First, the corrosion rate and residual strength characteristics are analyzed through corrosion tests and numeric...  (本文共12页) 阅读全文>>

The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In addition,the experimental equipment in many cases cannot meet the actual conditions and the experimental cost is very high. These comprehensive factors cause the existing casing design to not meet the actua...  (本文共9页) 阅读全文>>

Eight casing failure modes and 32 risk factors in oil and gas wells are given in this paper. According to the quantitative analysis of the influence degree and occurrence probability of risk factors, the Borda counts for failure modes are obtained with the Borda method. The risk indexes of failure modes are derived from the Borda matrix. Based on the support vector machine (SVM), a cas...  (本文共6页) 阅读全文>>

In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material's yield strength, the casing deforms and collapses. The traditional casing design standard only considers the influence of temperature variation on casing material's yield strength. Actually, for commonly used grades of...  (本文共8页) 阅读全文>>