An Image Measurement Method for Evaluating Pitting Corrosion Behavior of Tubing

A technology of image measurement and oil pipe, applied in the field of metal pitting corrosion evaluation

Active Publication Date: 2020-07-03
XI'AN PETROLEUM UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the pitting process is arbitrary, accidental, and random, so the above-mentioned pitting behavior research method only studies a small part of the corroded surface, which has great limitations.

Method used

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  • An Image Measurement Method for Evaluating Pitting Corrosion Behavior of Tubing
  • An Image Measurement Method for Evaluating Pitting Corrosion Behavior of Tubing
  • An Image Measurement Method for Evaluating Pitting Corrosion Behavior of Tubing

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] Measuring area corresponding to different magnifications

[0025] The material of the test piece used is J55 steel, the specification is 50×13×1.5mm, φ=6mm, and the surface area of ​​the front and back of the test piece is 621.7265mm 2 , the microscope is an OLYMPUS DSX500 optical digital microscope, and the same area of ​​the test piece is scanned with a single threshold of different magnifications and a 9-threshold mosaic scan (overlapping ratio of 10%). The results are shown in Table 1. Carry out splicing scanning of four points on one surface of the test piece with a magnification of 139 times and 9 visual thresholds, and the scanned area accounts for about 20% of the surface area, which is far beyond the research scope of other methods and can respond to the test more comprehensively and accurately. Pitting behavior on the chip surface.

[0026] Table 1 The scanning area corresponding to different magnifications and the proportion of the coupon surface

[0027] ...

Embodiment 2

[0029] Test piece surface corrosion depth measurement

[0030] The material of the test piece used is J55 steel, the specification is 50×13×1.5mm, φ=6mm, the microscope is OLYMPUSDSX500 optical digital microscope, the magnification is 208 times, and the image is a single-vision threshold image. The 10 colors in the picture represent different corrosion depths. Set the ten colors to divide 0-60 μm into equal parts. From left to right, they represent the depths of 54-60 μm, 58-54 μm, and so on. The rightmost color represents the depth of 0-6 μm. . The maximum pitting depth in the picture was measured by a measuring microscope to be 59.32 μm, and the ratio of the area occupied by different colors to the visual threshold was analyzed by image analysis software to obtain the distribution of different corrosion depth ranges. The statistical results are shown in Table 2.

[0031] Table 2 Measurement results of corrosion depth on the surface of the test piece

[0032]

Embodiment 3

[0034] Pitting corrosion on the surface of the test piece

[0035] The material of the test piece used is J55 steel, the specification is 50×13×1.5mm, φ=6mm, corrosion conditions: 80g / L simulated formation water, 50°C, pressure 4MPa, corrosion time 5d. The microscope is an OLYMPUS DSX500 optical digital microscope with a magnification of 150 times. The image is a stitched image of 9 visual thresholds, and the depth represented by ten colors is 0-100 μm. The maximum pitting depth is 99.4μm, and the maximum pitting area is 64432μm 2 , see Table 3-Table 5 for the statistical results of corrosion information.

[0036] Table 3 Measurement results of corrosion depth on the surface of the test piece

[0037]

[0038] Table 4 Measurement results of area distribution of pitting pits on the surface of test pieces

[0039] Area (μm 2 )

0-50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450-500 ＞500 Proportion(%) 76.78 15.46 4.20 1.7...

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Abstract

The invention discloses an image measuring method for evaluating oil pipe pitting behaviors. By means of the corrosion weight loss method and the micro-measurement technology, a proper datum plane is built on the surface of a slide through a coating method, proper temperature, proper pressure and a proper medium are selected, different corrosion time is controlled, the number and the size of pitting generated on the surface of the slide are effectively controlled, then large-scale image scanning is conducted on the slide through a measurement microscope, image information of a metal surface at the same position before corrosion and after corrosion is compared, and accordingly evaluation in the aspects of generation and development positions of pitting on the surface of an oil pipe, the number, the pit size and appearance is achieved. Relative information of a large amount of pitting can be obtained qualitatively and quantitatively, important bases are provided for researching generation and development of the oil pipe pitting behaviors, and the method has important research and application value.

Description

technical field [0001] The invention relates to the technical field of metal pitting evaluation, in particular to an image measurement method for evaluating oil pipe pitting behavior. Background technique [0002] In the process of oil field development, there are many major accidents caused by corrosion, and the economic loss is very serious. Through investigation, it is found that a large part of the failure mode of the oil casing is due to the corrosion perforation and piercing of the pipe wall caused by pitting corrosion. Pitting corrosion is one of the most common forms of corrosion in oil fields, especially those containing hydrogen sulfide and carbon dioxide. This type of corrosion has the characteristics of strong concealment and great destructiveness, and its occurrence mechanism and development process have always been one of the focuses of oilfield anticorrosion research. [0003] Pitting pits may be wide or narrow, deep or shallow, isolated or connected, and th...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N17/00
CPCG01N17/006
Inventor 马云白海涛王新强吴新民任鹏谢娟
Owner XI'AN PETROLEUM UNIVERSITY
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