CN111982705A - Economical anti-H2S-CO2Stress corrosion performance testing method for oil well pipe - Google Patents
Economical anti-H2S-CO2Stress corrosion performance testing method for oil well pipe Download PDFInfo
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract
The invention discloses an economical anti-H2S‑CO2The method for testing the stress corrosion performance of the oil well pipe comprises the steps of processing and surface preprocessing a sample, calculating the surface area and the original mass, carrying out four-point bending loading according to nominal yield strength, integrally placing a fixture and the sample into a closed storage tank for a stress corrosion resistance test, carrying out surface derusting treatment on the sample which is not failed after the test period is finished, recording the tested mass, carrying out corrosion rate analysis, observing the surface appearance and measuring the corrosion depth, taking the corrosion depth of the tensile stress side surface of the sample as the final test result, and evaluating the corrosion pit depth through corrosion appearance observation and corrosion pit depth calculationThe stress corrosion resistance of the oil well pipe material is evaluated by combining the corrosion rate. On the basis of not adding extra tests, the invention carries out quantifiable rating on the bending loading non-failure sample, evaluates the corrosion resistance of the oil well pipe in a specific working condition environment, and guides material selection and equipment maintenance.
Description
Technical Field
The invention provides an accurate evaluation economic anti-H2S-CO2A stress corrosion performance test method of an oil well pipe, in particular to a method for evaluating the stress corrosion resistance of the oil well pipe by analyzing the surface appearance of a bending loading sample and measuring the corrosion depth of the sample, belonging to the field of corrosion performance detection.
Background
The steel for oil well pipes accounts for 40% or more of the total amount of the steel for the petroleum industry. In recent years, along with the exploration and development of oil and gas wells in ultra-deep, ultra-high temperature and ultra-high corrosion harsh environments, the working condition environment of the oil and gas wells generally has high temperature, high pressure and high CO2High H2S, high Cl-High salinity, the stress corrosion failure of the oil well pipe caused by the complex and harsh working conditions and the special operation process seriously influences the normal production and operation of the oil and gas field, especially the H-containing oil2S-CO2When the oil well pipes coexist, the stress corrosion problem of the oil well pipes is more prominent, and corrosion failure accidents are frequent.
Stress Corrosion Cracking (Stress Corrosion Cracking-SCC) refers to a phenomenon in which a metal material subjected to tensile Stress generates a delayed Cracking or a delayed fracture in a specific medium due to a synergistic effect of a corrosive medium and Stress. Compared with other forms of corrosion damage, the stress corrosion cracking has the advantages of high crack propagation speed, sudden fracture and highest danger coefficient.
In view of the above circumstances, it is necessary to perform a test evaluation of the stress corrosion cracking resistance of an oil well pipe, particularlyIs a tensile load stress corrosion cracking test. NACE Standard TM 0177-2005H2Standard tensile tests (method A) are specified in indoor tests for resisting sulfide stress corrosion cracking and stress corrosion cracking of metals in an S environment and laboratory tests for resisting special form environmental cracking of metals in a hydrogen sulfide environment GB/T4157-2006, and the indoor tests comprise four common methods, namely a standard tensile test, a standard bending beam test, a standard C-shaped ring test and a standard double cantilever beam test (DCB). The hydrogen sulfide corrosion resistance of the oil well pipe can be directly evaluated by tensile, bending beam and C-shaped ring tests, but the test conditions are harsh, the requirement on sample processing precision is high, the test result only can give failure and non-failure information, and the hydrogen sulfide corrosion resistance grade cannot be quantitatively evaluated. And the standard double cantilever beam test provides the measurement of the EC expansion resistance of the metal material, KISSCFor SSC, KIECThe method can quantify the direct grade of crack propagation resistance, but has complex model design and theoretical calculation, high requirement on the quality of operators, difficult field test and incapability of realizing.
A four-point bending test in the ASTM G39-99 standard is a conventional method for evaluating the stress corrosion resistance of an oil well pipe, the method A standard solution is adopted, equipment is simple, the requirement on operators is not high, whether cracks exist on the surface of a sample is observed by only amplifying by 10 times, the test result only gives failure and non-failure information, for the sample without failure, the stress corrosion resistance grade of the sample cannot be evaluated, other experimental means are required to be combined for comprehensive evaluation, the test period is prolonged, or new equipment is required to be purchased, and the cost requirement is high.
Disclosure of Invention
The invention aims to provide an economical anti-H2S-CO2The stress corrosion performance test method of the oil well pipe further analyzes the samples which are not failed in the bending loading test without adding extra tests, further evaluates the stress corrosion sensitivity of the oil well pipe through subsequent surface morphology observation and the depth measurement of the corrosion pit on the side surface of the tensile stress, and can quantify the stress corrosion sensitivity of the oil well pipeEvaluation of H resistance of oil well pipe2S-CO2Corrosion performance.
In order to realize the purpose of the invention, the technical scheme of the invention is as follows:
economical anti-H2S-CO2The method for testing the stress corrosion performance of the oil well pipe comprises the steps of sample processing, surface treatment, bending loading test, corrosion rate analysis, sample surface appearance observation and corrosion depth measurement, wherein the sample is processed into a proper size, the surface of the sample is pretreated, the surface area and the original mass are calculated, four-point bending loading under a certain proportion is carried out according to nominal yield strength, then a clamp and the sample are integrally placed in a closed storage tank for carrying out the stress corrosion resistance test, after the test period is completed, the sample which does not fail is subjected to surface rust removal treatment, the mass after the test is recorded, the corrosion rate analysis is carried out, further the surface appearance observation and the corrosion depth measurement are carried out, the corrosion depth of the tensile stress side surface of the sample is taken as the final test result, and the stress corrosion resistance performance of the oil well pipe material is evaluated by the corrosion appearance observation and the calculation of the depth of a, and (3) evaluating the corrosion resistance of the oil well pipe by combining the corrosion rate.
Furthermore, the test solution in the four-point bending loading experiment is HCO containing 1.5-3.0 g/L3 -Introducing hydrogen sulfide into the nice standard A solution at normal pressure to saturate, and then introducing CO2Gas, the pressure of the closed storage tank is constant at 0.1-0.5 Mpa, and CO is supplemented every 24-48 h2A gas.
Further, the etch pit depth is measured by the following steps:
1) placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, and focusing an area to be measured on the surface of the sample in an optical microscope mode to ensure that an image is displayed clearly;
2) switching to a laser scanning imaging mode, scanning the area to be detected on the surface of the sample layer by layer to obtain a two-dimensional topography, and then converting to form a three-dimensional topography;
3) and switching to a laser confocal three-dimensional measurement mode, selecting a typical area in a direction parallel to the X axis for intercepting to obtain a cross section profile topography and a cross section profile curve, wherein the profile curve shape represents the surface topography of the sample at the cross section position, selecting the adjacent highest point and the lowest point on the profile curve, and the measured height difference is the depth of the corrosion pit.
Further, the bending loading test is to pretreat the surface of the sample, carry out bending loading according to the proportion of 50-90% of nominal yield strength, and then integrally place the clamp and the sample in a closed storage tank containing a test solution for corrosion; the magnification of the laser confocal microscope is 300-500, so that the representative observation area is ensured.
The invention has the beneficial effects that: the stress corrosion resistance performance of the oil well pipe material in a service environment or a simulated actual environment is tested, the stress corrosion resistance performance of the oil well pipe is evaluated by observing corrosion morphology and measuring the depth of a corrosion pit, a quantifiable rating is carried out on a bending loading non-failure sample on the basis of not increasing an additional test, the corrosion resistance of the oil well pipe material in a specific working condition environment is further evaluated, and material selection and equipment maintenance are guided.
Drawings
FIG. 1 surface topography of cleaned sample (loading ratio 50%, HCO 2 g/L)3 -Actual well fluid of the oil field);
FIG. 2 surface topography of the cleaned sample (loading ratio 80%, 2g/L HCO content)3 -The nice standard a solution of (1), containing saturated hydrogen sulfide);
FIG. 3 surface topography of the cleaned sample (loading ratio 80%, 2g/L HCO content)3 -The nice standard A solution of (1) contains saturated hydrogen sulfide and 0.3MPa CO2)；
FIG. 4 surface topography of the cleaned sample (90% loading, 2g/L HCO content)3 -The nice standard A solution of (1) contains saturated hydrogen sulfide and 0.3MPa CO2)。
FIG. 5 is a two-dimensional topographical view;
FIG. 6 is a three-dimensional topographical view and a cross-sectional profile plot.
Detailed Description
The invention is economical H-resistance by combining the following drawings2S-CO2The method for testing the stress corrosion performance of the oil well pipe is explained in detail. The scope of the invention is not limited to the following embodiments, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.
Example 1
The test specimens used were A, B two types of oil country tubular goods (for example, oil country tubular goods different in material and in processes such as rolling and heat treatment, and the same explanation will be given in the following examples). The test method comprises the steps of sample processing a, surface treatment b, bending loading test c, corrosion rate analysis d, appearance observation of the surface of the sample e and calculation of the depth of a corrosion pit.
The sample processed in the step a is processed into the size of 115mm 15mm 5mm and the surface finish degree of 0.3 mu m;
in the step b, the surface treatment test adopts acetone cleaning twice, and then absolute ethyl alcohol cleaning once, so as to remove residues and grease on the surface of the sample, then calculate the surface area of the sample, and record the initial quality;
c, in the step c, a four-point bending loading mode is adopted in the bending loading test, loading is carried out according to 50% of the nominal yield strength of the oil well pipe, after the loading is finished, the whole sample and the clamp are placed into a closed storage tank for carrying out the stress corrosion resistance test, and the sample solution is HCO containing 2g/L3 -The actual well fluid of the oil field is not broken in a test period of 720h, after the test is finished, the surface rust layer is treated according to a method for removing corrosion products of a steel sample in a standard GB/T-19292.4, and the sample after rust removal is placed in a dryer for 24 h;
d, recording the mass after the test, calculating the weight loss in the corrosion process, analyzing the corrosion rate, and recording the average corrosion rate;
e, observing the surface appearance and measuring the depth of the corrosion pit by using a laser confocal microscope, firstly, placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, under an optical microscope mode, enabling the magnification factor to be 400, and focusing and adjusting the contrast and the brightness of a region to be measured on the surface of the sample; then switching to a laser scanning imaging mode, scanning the areas to be measured on the surface of the sample layer by layer to obtain a two-dimensional topography map (see fig. 5), and then converting to form a three-dimensional topography map, as shown in fig. 1, selecting five areas to be measured on the surface of the sample of each steel type, respectively obtaining a cross-section profile topography map and a cross-section profile curve, selecting adjacent highest points and lowest points on the profile curve, wherein the measured height difference is the depth of the corrosion pit, the corrosion depth value pit is the maximum value of the height difference on the whole profile curve at the cross section (see fig. 6), and the test results are shown in table 1, and the analysis shows that: the stress corrosion resistance performance is in the order from high to low: a > B, the corrosion resistance is in the order from high to low: a > B.
TABLE 1 depth of etch pits on the surface of the test specimens
Example 2
The test method comprises the steps of a sample processing, b surface treatment, c bending loading test, d corrosion rate analysis, e sample surface morphology observation and corrosion pit depth calculation.
The sample processed in the step a is processed into the size of 115mm 15mm 5mm and the surface finish degree of 0.3 mu m;
in the step b, the surface treatment test adopts acetone cleaning twice, and then absolute ethyl alcohol cleaning once, so as to remove residues and grease on the surface of the sample, then calculate the surface area of the sample, and record the initial quality;
c, in the step c, a four-point bending loading mode is adopted in the bending loading test, loading is carried out according to 80% of the nominal yield strength of the oil well pipe, after the loading is finished, the whole sample and the clamp are placed into a closed storage tank for carrying out the stress corrosion resistance test, and the sample solution contains 2g/L HCO3 -The silicon standard A solution contains saturated hydrogen sulfide, and the test period is 720h without fractureAfter the test is finished, carrying out surface rust layer treatment according to a method for removing corrosion products of a steel sample in the standard GB/T-19292.4, and placing the sample after rust removal in a dryer for 24 hours;
d, recording the mass after the test, calculating the weight loss in the corrosion process, analyzing the corrosion rate, and recording the average corrosion rate;
e, observing the surface appearance and measuring the depth of the corrosion pit by using a laser confocal microscope, firstly, placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, under an optical microscope mode, enabling the magnification factor to be 400, and focusing and adjusting the contrast and the brightness of a region to be measured on the surface of the sample; then switching to a laser scanning imaging mode, scanning the areas to be detected on the surface of the sample layer by layer to obtain a two-dimensional topography map (see fig. 5), and then converting to form a three-dimensional topography map, as shown in fig. 2, selecting five areas to be detected on the surface of the sample of each steel type, respectively obtaining a cross-section profile topography map and a cross-section profile curve, selecting adjacent highest points and lowest points on the profile curve, wherein the measured height difference is the depth of the corrosion pit, the corrosion depth value pit is the maximum value of the height difference on the whole profile curve at the cross section (see fig. 6), the test result is shown in table 2, and the analysis result can be seen as follows: the stress corrosion resistance performance is in the order from high to low: a > B, the corrosion resistance is in the order from high to low: a > B.
TABLE 2 depth of corrosion on the surface of the test specimens
Example 3
The test method comprises the steps of a sample processing, b surface treatment, c bending loading test, d corrosion rate analysis, e sample surface morphology observation and corrosion pit depth calculation.
The sample processed in the step a is processed into the size of 115mm 15mm 5mm and the surface finish degree of 0.3 mu m;
in the step b, the surface treatment test adopts acetone cleaning twice, and then absolute ethyl alcohol cleaning once, so as to remove residues and grease on the surface of the sample, then calculate the surface area of the sample, and record the initial quality;
c, in the step c, a four-point bending loading mode is adopted in the bending loading test, loading is carried out according to 80% of the nominal yield strength of the oil well pipe, after the loading is finished, the sample and the clamp are integrally placed into a closed storage tank for carrying out a stress corrosion resistance test, and the sample solution contains 2g/LHCO3 -Introducing hydrogen sulfide into the nice standard A solution at normal pressure to saturate, and then introducing CO2Gas, making the pressure of the closed storage tank constant at 0.3Mpa, and supplementing CO every 24h2Gas, the test period is 720h, the steel sample is not broken, after the test is finished, the surface rust layer is processed according to the standard GB/T-19292.4, a method for removing corrosion products of the steel sample, and the sample after rust removal is placed in a dryer for 24 h;
d, recording the mass after the test, calculating the weight loss in the corrosion process, analyzing the corrosion rate, and recording the average corrosion rate;
e, observing the surface appearance and measuring the depth of the corrosion pit by using a laser confocal microscope, firstly, placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, under an optical microscope mode, enabling the magnification factor to be 400, and focusing and adjusting the contrast and the brightness of a region to be measured on the surface of the sample; then switching to a laser scanning imaging mode, scanning the areas to be detected on the surface of the sample layer by layer to obtain a two-dimensional topography map (see fig. 5), and then converting to form a three-dimensional topography map, as shown in fig. 3, selecting five areas to be detected on the surface of the sample of each steel type, respectively obtaining a cross-section profile topography map and a cross-section profile curve, selecting adjacent highest points and lowest points on the profile curve, wherein the measured height difference is the depth of the corrosion pit, the corrosion depth value pit is the maximum value of the height difference on the whole profile curve at the cross section (see fig. 6), the test result is shown in table 3, and the analysis result can be seen as follows: the stress corrosion resistance performance is in the order from high to low: a > B, the corrosion resistance is in the order from high to low: a > B.
TABLE 3 depth of etch pits on the surface of the test specimens
Example 4
The test method comprises the steps of a sample processing, b surface treatment, c bending loading test, d corrosion rate analysis, e sample surface morphology observation and corrosion pit depth calculation.
The sample processed in the step a is processed into the size of 115mm 15mm 5mm and the surface finish degree of 0.3 mu m;
in the step b, the surface treatment test adopts acetone cleaning twice, and then absolute ethyl alcohol cleaning once, so as to remove residues and grease on the surface of the sample, then calculate the surface area of the sample, and record the initial quality;
c, in the step c, a four-point bending loading mode is adopted in the bending loading test, loading is carried out according to 90% of the nominal yield strength of the oil well pipe, after the loading is finished, the sample and the clamp are integrally placed into a closed storage tank for carrying out a stress corrosion resistance test, and the sample solution contains 2g/LHCO3 -Introducing hydrogen sulfide into the nice standard A solution at normal pressure to saturate, and then introducing CO2Gas, making the pressure of the closed storage tank constant at 0.3Mpa, and supplementing CO every 24h2Gas, the test period is 720h, the steel sample is not broken, after the test is finished, the surface rust layer is processed according to the standard GB/T-19292.4, a method for removing corrosion products of the steel sample, and the sample after rust removal is placed in a dryer for 24 h;
d, recording the mass after the test, calculating the weight loss in the corrosion process, analyzing the corrosion rate, and recording the average corrosion rate;
e, observing the surface appearance and measuring the depth of the corrosion pit by using a laser confocal microscope, firstly, placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, under an optical microscope mode, enabling the magnification factor to be 400, and focusing and adjusting the contrast and the brightness of a region to be measured on the surface of the sample; then switching to a laser scanning imaging mode, scanning the areas to be detected on the surface of the sample layer by layer to obtain a two-dimensional topography map (see fig. 5), and then converting to form a three-dimensional topography map, as shown in fig. 4, selecting five areas to be detected on the surface of the sample of each steel type, respectively obtaining a cross-section profile topography map and a cross-section profile curve, selecting adjacent highest points and lowest points on the profile curve, wherein the measured height difference is the depth of the corrosion pit, the corrosion depth value pit is the maximum value of the height difference on the whole profile curve at the cross section (see fig. 6), the test result is shown in table 4, and the analysis result can be seen as follows: the stress corrosion resistance performance is in the order from high to low: a > B, the corrosion resistance is in the order from high to low: a > B.
TABLE 4 depth of etch pits on the surface of the test specimens
Claims (4)
1. Economical anti-H2S-CO2The method for testing the stress corrosion performance of the oil well pipe is characterized by comprising the steps of sample processing, surface treatment, bending loading test, corrosion rate analysis, sample surface appearance observation and corrosion depth measurement, wherein the sample is processed into a proper size, the surface of the sample is pretreated, the surface area and the original mass are calculated, four-point bending loading under a certain proportion is carried out according to nominal yield strength, then a clamp and the sample are integrally placed in a closed storage tank for carrying out the stress corrosion resistance test, after the test period is completed, the sample which does not fail is subjected to surface rust removal treatment, the mass after the test is recorded, the corrosion rate analysis is carried out, further the surface appearance observation and the corrosion depth measurement are carried out, the corrosion depth of the tensile stress side surface of the sample is taken as the final test result, and the stress corrosion resistance performance of the oil well pipe material is evaluated by the corrosion appearance observation and the calculation of the depth of a, and (3) evaluating the corrosion resistance of the oil well pipe by combining the corrosion rate.
2. The method of claim 1Economical anti-H2S-CO2The method for testing the stress corrosion performance of the oil well pipe is characterized in that a test solution in a four-point bending loading experiment is HCO containing 1.5-3.0 g/L3 -Introducing hydrogen sulfide into the nice standard A solution at normal pressure to saturate, and then introducing CO2Gas, the pressure of the closed storage tank is constant at 0.1-0.5 Mpa, and CO is supplemented every 24-48 h2A gas.
3. An economical H-resistance according to claim 12S-CO2The stress corrosion performance testing method of the oil well pipe is characterized in that the measuring steps of the depth of the corrosion pit are as follows:
1) placing a sample on an objective table, rotating the objective table to enable the length direction of the sample to be measured to be parallel to an X axis and the width direction of the sample to be measured to be parallel to a Y axis, and focusing an area to be measured on the surface of the sample in an optical microscope mode to ensure that an image is displayed clearly;
2) switching to a laser scanning imaging mode, scanning the area to be detected on the surface of the sample layer by layer to obtain a two-dimensional topography, and then converting to form a three-dimensional topography;
3) and switching to a laser confocal three-dimensional measurement mode, selecting a typical area in a direction parallel to the X axis for intercepting to obtain a cross section profile topography and a cross section profile curve, wherein the profile curve shape represents the surface topography of the sample at the cross section position, selecting the adjacent highest point and the lowest point on the profile curve, and the measured height difference is the depth of the corrosion pit.
4. An economical H-resistance according to claim 12S-CO2The method for testing the stress corrosion performance of the oil well pipe is characterized in that the bending loading test is to pretreat the surface of a sample, carry out bending loading according to the proportion of 50-90% of nominal yield strength, and then integrally place a clamp and the sample into a closed storage tank containing a test solution for corrosion; the magnification of the laser confocal microscope is 300-500, so that the representative observation area is ensured.
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