Reservoir Casing Damage The Mechanism

This paper was supported by National Natural Science Foundation of China (NSFC) "Study of Mechanism of Casing Failure on the Formation of Complex Mechanics System Based on numerical simulation" (Project No. :50074025).This paper mainly dealt with the Mechanism of Casing Failure on the Oil-deformation. Many of related references were studied in the paper, some methods and ideas are to help our study. The formulas on the perforated casing collapse strength were derived while the casing was perforated. And the stress and displacement formulas on the system of deformation, cement and casing with the non-uniform load were derived. Compared the calculating results by FEM (Finite Element Method), those formulas were true. Those formulas give simple methods to design optimally casing string.New ideas and methods in the paper:1) The formulas on perforated casing collapse strength were deducted, which offereda convenient method to analyze the relationship between casing collapse strength and perforation;2) The stress and displacement formulas on the system of casing, cement anddeformation under the non-uniform load were deducted, which offered the theoretical found for designing optimally casing string;3) The relationship between structure in-situ field of whole oil field and casing failurewere studied, which offered the scheme for the prediction of casing failure. The process of study in the paper:1) For simulating the relationship between the structure in-situ field and the casingfailure in the oil-deformation, the tests of the uniaxial tensile, compress, tnaxial compress and dilatability were made on the samples of the drill cores from deformation of casing failure position in Yuejing II oil field. The elasticity modulus, Poisson's ratio, cohesion, inner friction angle and linear dilatation coefficient of rock were obtained from those tests, which offered the material data for the theoretical analysis and FEM on the mechanism of casing failure of oil-deformation;2) The varieties of casing collapse strength under the conditions of perforated ornon-uniform load were theoretically analyzed;3) The calculated results by theoretical analysis were compared with those by FEM;4) The casing failure caused by structure in-situ stress field of Yuejing II oil field wasanalyzed with FEM.