A double-layer composite casing with mismatched strength

Abstract

The invention discloses a strength-mismatched double-layer composite casing, which includes an external threaded joint, an internal threaded joint, an outer layer casing and an inner layer casing, wherein the outer layer casing and the inner layer casing adopt different strength grades material; after the outer casing is plastically deformed and in contact with the inner casing, since the stiffness of the inner casing is much greater than that of the outer casing, and there is a coating with a small friction coefficient on the outer wall of the inner casing, the With the anti-friction effect of the lubricating fluid, under the action of the external extrusion force, the outer casing will undergo metal plastic flow deformation along the outer wall of the inner casing, absorb part of the external extrusion load, reduce the external extrusion load borne by the inner casing, and effectively improve The anti-extrusion performance of the double-layer composite casing reduces and reduces the risk of plastic deformation failure of the inner layer casing, and is suitable for the deformation area of ​​the conventional casing caused by non-uniform load.

Description

technical field [0001] The invention belongs to the technical field of casing for oil and gas development, and in particular relates to a double-layer composite casing with strength mismatch. Background technique [0002] With the deepening of the production and development of various oilfields at home and abroad, casing damages of varying degrees have occurred in most oilfields, which has caused a great impact on oil production and development. Double-layer composite casing is an important means of early casing protection. At present, most double-layer composite casings use the method of injecting cement between the inner and outer casings, which can improve the collapse resistance of the casing. In large areas, the extrusion force of the formation is directly transmitted to the inner casing through the outer casing and the cement sheath, causing damage to the inner casing, resulting in the failure of the oil production project, and the construction is complicated and diffi...

AI Technical Summary

Problems solved by technology

Double-layer composite casing is an important means of early casing protection. At present, most double-layer composite casings use the method of injecting cement between the inner and outer casings, which can improve the collapse resistance of the casing. In large areas, the extrusion force of the formation is directly transmitted to the inner casing through the outer casing and the cement sheath, causing damage to the inner casing, resulting in the failure of the oil production project, and the construction is complicated and difficult to operate; at the same time, the existing The double-layer composite casing has no research results on the material strength matching of the inner and outer casings, and the performance of the casings is uneven

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