Method for characterizing steel fatigue crack propagation behavior for casing drilling

A technology for fatigue crack propagation and casing drilling, which is applied in the field of casing, can solve the problems of unclear physical meaning of parameters, time-consuming and labor-intensive, etc., and achieves the effect of avoiding formula derivation and mathematical calculation, simple formula and eliminating background noise.

Inactive Publication Date: 2012-07-25
XI'AN PETROLEUM UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The conventional Pairs characterization method is to measure the growth of fatigue cracks by performing a destructive fatigue test on a fatigue testing machine, which is often time-consu

Method used

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  • Method for characterizing steel fatigue crack propagation behavior for casing drilling
  • Method for characterizing steel fatigue crack propagation behavior for casing drilling
  • Method for characterizing steel fatigue crack propagation behavior for casing drilling

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] A method for characterizing the fatigue crack growth behavior of steel for casing drilling, comprising the following steps:

[0025] First, derusting, grinding and cleaning the CT samples of N80 casing steel;

[0026] Firstly, pre-crack the CT sample, the pre-crack length is 2 mm, derust with a hydrochloric acid solution with a molar concentration of 1.0%, and the soaking time is 1 minute; then clean it with ethanol and deionized water respectively, and the soaking time is 2 Minutes, after face grinding and polishing, use 200 ml of HNO with a molar concentration of 2% 3 solution, the HNO 3 The solution uses pure ethanol as a solvent, cleans it, takes it out, hangs it up, and blows it dry;

[0027] Second, the low-frequency noise test before fatigue is carried out on the N80 casing steel CT sample;

[0028] 1) Weld the lead wires of the CT samples of N80 casing steel after rust removal and cleaning. The present invention takes the fatigue crack monitoring point in the...

Embodiment 2

[0040] A new low-frequency noise characterization method for casing steel fatigue crack growth behavior, including the following steps:

[0041] First, derusting, grinding and cleaning of CT samples such as N80 casing steel;

[0042] Rust removal is carried out with a hydrochloric acid (HCl) solution with a molar concentration of 3.0%, and the soaking time is 2 minutes; then, it is cleaned with ethanol and deionized water, and the soaking time is 2 minutes. 4.0% HNO 3 Clean with the etchant of ethanol solution, take it out and hang it, and dry it;

[0043] Second, carry out low-frequency noise test on N80 casing steel samples before fatigue;

[0044] 1) Weld the leads on the CT samples of N80 casing steel after derusting and cleaning. In the present invention, the fatigue crack monitoring point in the conventional fatigue test is used as the potential reference point, and two lead wires are respectively welded on both sides of the prefabricated crack of the sample;

[0045...

Embodiment 3

[0056] A new low-frequency noise characterization method for casing steel fatigue crack growth behavior, including the following steps:

[0057] First, derusting, grinding and cleaning of CT samples such as N80 casing steel;

[0058] Rust removal can be carried out with a hydrochloric acid (HCl) solution with a molar concentration of 5.0%, and the soaking time is 3 minutes; then, it is cleaned with ethanol and deionized water, and the soaking time is 2 minutes. 5% HNO 3 solution, the HNO 3 The solution uses pure ethanol as a solvent, cleans it, takes it out, hangs it up, and blows it dry;

[0059] Second, carry out low-frequency noise test on N80 casing steel samples before fatigue;

[0060] 1) Weld the lead wires of the CT samples of N80 casing steel after rust removal and cleaning. The present invention takes the fatigue crack monitoring point in the conventional fatigue test as the potential reference point, and welds two lead wires on both sides of the prefabricated cra...

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Abstract

The invention discloses a method for characterizing a steel fatigue crack propagation behavior for casing drilling. The method comprises the steps of: firstly, sampling casing drilling steel, preparing a sample and cleaning; secondly, carrying out low-frequency noise testing on the sample before fatigue; thirdly, carrying out fatigue testing on the sample; fourthly, carrying out low-frequency noise testing on the sample after fatigue; and fifthly, analyzing, extracting and processing low-frequency noise data before and after the fatigue testing according to low-frequency l/f noise information before and after the fatigue, and characterizing a fatigue crack propagation behavior of the sample. Through two times of low-frequency l/f noise testing before and after the fatigue propagation, the influence of background noise of the sample is eliminated, more complex formula derivation and mathematical calculation in common characterizing methods are avoided, no strict requirements are required for the shape of the sample, the fatigue testing quantity is favorably reduced, the testing cost is lowered, and the fatigue crack propagation behaviors of various samples can be conveniently subjected to sampling and fatigue service life estimation; and the method has the characteristics of convenience in use, low cost and convenience in popularization.

Description

technical field [0001] The present invention relates to the technical field of casing drilling, in particular to a characterization method for fatigue crack growth behavior of steel for casing drilling, and to a low-frequency noise characterization method for fatigue crack growth of N80 steel for casing drilling, which is mainly used for low-frequency 1 / f noise For the analysis of fatigue crack growth performance of N80 casing drilling steel, the fatigue information and crack growth information of N80 casing steel are obtained by comparing and analyzing the low-frequency noise information before and after fatigue crack growth. Background technique [0002] In actual oil and gas production operations, the stress on the casing is very complicated. When the casing is in service, under the continuous action of periodic alternating cyclic loads, fatigue damage begins to increase in a small range, and fatigue cracks begin to initiate after a period of damage. It is generally beli...

Claims

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Application Information

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IPC IPC(8): G01N3/08
Inventor 王党会许天旱
Owner XI'AN PETROLEUM UNIVERSITY
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