Test method for excessive twist strain of oil casing pipe special button

Abstract

The invention provides a test method for excessive twist strain of an oil casing pipe special button. The method comprises the following steps: 1, a test instrument and devices are selected; 2, reference lines are drawn on the inner wall of the sealing surface of the oil casing pipe special button; 3, a strain foil is stuck; after the sticking operation is completed, the lead of the strain foil is welded with a flex cable together, the socket of the flex cable is connected onto a strain box, and the strain box is connected with the communication line of a computer well, so that the test can be performed. The test method has the effects that the sticking method is adopted to reflect the stress state of three directions near to the sealing surface, when the strain value is within the yield strain value stipulated by the API standard, and corresponding to the torque at the time, the highest bearable torque capacity of the special button can be obtained. The actual strain situation can be reflected, the yield phenomenon is obviously seen, and the corresponding relation between the strain and torque can be precisely determined.

Description

technical field [0001] The invention relates to a test method for overtorsion and large strain of a special buckle of an oil and casing pipe, which is used to evaluate the relationship between the deformation of a sealing part and the torque when the special buckle for oil and gas pipes is subjected to an overtorque test. Background technique [0002] In recent years, the environmental well conditions of the oil and gas industry have become more and more complex, and more stringent requirements have been put forward for the oil and casing used. Among them, the special buckle for connecting the oil and casing is an important link with high strength and high sealing performance. [0003] As the wellbore is getting deeper and deeper, when the oil casing is going down the well, the special buckle used for connection requires high torque when tightening, and sometimes the special buckle is over-torqued during screwing, and the special buckle male end is over-torqued. The sealing ...

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Problems solved by technology

[0004] After searching various papers, patents and other documents, no similar method has been found to solve this problem. Only one document that uses the strain method to test the external elastic stress state of the API buckle coupling, that is, "the surface contact state of the internal and external threads of the pipe threaded joint Distribution test method", this method is in the elastic range, it cannot measure large strains above yield, and the sticking of strain gauges is not limited by the area

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