Method for determining reliable strength of tensile resistance of petroleum pipe

Abstract

The application discloses a method for determining the tensile reliability strength of petroleum pipes. On the basis of a historical API pipe body yield strength calculation formula, through a limit state equation corresponding to pipe body tensile yield strength, considering model uncertainty, the tensile strength of the oil casing pipe is calculated according to the first order second moment method, and then the tensile reliability strength of the oil casing pipe is calculated, and the finite element analysis and the physical test verification are adopted to verify and evaluate the calculation result of the tensile reliability strength. Through the application, the purpose of truly solving the scientific calculation method of the tensile reliability strength of the petroleum pipes can be achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of new methods for oil pipe materials, specifically relating to a method for determining the tensile reliability strength of oil pipe materials. Background Technology

[0002] Oil casing plays a vital role in oil drilling and oilfield development. Improper selection can lead to frequent failures of various types of oil casing, and the failure rate is on the rise, causing huge economic losses to oilfields and posing a serious challenge to safe production. Therefore, accurate calculation of oil casing strength is of paramount importance.

[0003] Currently, the internationally recognized and widely used method for calculating the tensile strength of tubing is the historical API method for calculating the yield strength of tubing, and the latest ISO 10400 standard also adopts the same calculation method. This formula is derived based on statistical experimental data, and due to limitations in past sample quality and experimental conditions, it has become somewhat conservative. In recent years, due to significant improvements in the precision and performance of various parameters of oil casing and tubing, the actual connection strength has exceeded the rated value of the historical API calculation formula. Therefore, this formula cannot accurately reflect the strength differences between oil casing and tubing of different qualities, which has brought many challenges to the strength design and application of oil casing and tubing.

[0004] Therefore, establishing a scientific and reasonable method for calculating the reliability strength of oil casing and tubing that can reflect the statistical characteristics of the connection strength parameters of oil casing and tubing products is an urgent and challenging task that has significant engineering value. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for determining the tensile reliability strength of oil pipes, so as to solve the problem that the API pipe yield strength calculation method in the prior art cannot accurately reflect the strength difference of oil casings of different qualities, which brings many difficult problems to the strength design and application of oil casings.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for determining the tensile reliability strength of oil pipes, comprising:

[0008] Step 1: Obtain connection strength calculation parameters through experiments;

[0009] Step 2: Calculate the yield strength of the pipe connection;

[0010] Step 3: Calculate the tensile strength of the tube under the limit state equation;

[0011] Step 4: Obtain the uncertainty based on the experimental values ​​and the calculated values ​​obtained in Step 3;

[0012] Step 5: Obtain the tensile strength and standard deviation of the pipe body;

[0013] Step Six: Calculate the tensile reliability strength;

[0014] Step 7: Perform finite element analysis and evaluation on the reliability strength calculation results, and verify and evaluate them through physical tensile tests;

[0015] Step 8: Compare the finite element analysis results with the actual tensile test results. If they are consistent, output the calculated tensile reliability strength. If they are inconsistent, recalculate.

[0016] Preferably, in step one, the geometric dimensions of the oil casing are measured and a tensile test is performed on the material, and the parameters for calculating the connection strength are obtained through statistical analysis.

[0017] Preferably, in step one, the parameters include average outer diameter, average wall thickness, and material tensile strength.

[0018] Preferably, in step two, the yield strength of the pipe connection is calculated according to the API formula:

[0019] F YAPI =f ymn A p (1)

[0020] Among them, F YAPI Indicates the yield strength of the tube; f ymn Indicates the specified minimum yield strength; A p This indicates the cross-sectional area of ​​the tube.

[0021] Preferably, in step three, the limit state equation is:

[0022] F = πf y (Dt)t (2)

[0023] Where F is the tensile strength of the pipe body; f y t represents the tensile strength of the material; D represents the average outer diameter; and t represents the average wall thickness.

[0024] Preferably, in step four, the model uncertainty is obtained by comparing the actual test values ​​with the calculated values ​​of oil casing pipes of the same manufacturer, batch, and specifications.

[0025] Preferably, in step four, the formula for calculating the tensile strength of the pipe connection is:

[0026] F = m u πf y (Dt)t (3)

[0027] Where F is the tensile strength of the pipe body; f y t represents the tensile strength of the material; D represents the average outer diameter; t represents the average wall thickness; m represents the average wall thickness. u This represents the model uncertainty.

[0028] Preferably, after performing a second-order moment method partial differential calculation on formula (3), according to f y The formula for calculating the F-distribution from the distributions of t and D is:

[0029]

[0030]

[0031] Where SDF is the standard squared deviation; mu is the model uncertainty; This represents the average tensile strength of the material. The average outer diameter; This represents the average wall thickness.

[0032] Preferably, a second-order partial differential calculation using the method of moments is performed on formula (3):

[0033]

[0034]

[0035]

[0036]

[0037] Among them, f y t represents the tensile strength of the material; D represents the average outer diameter; t represents the average wall thickness; m represents the average wall thickness. u For model uncertainty. Preferably, the tensile reliability strength is calculated as follows:

[0038] F des n =Fk*SD F (7)

[0039] Among them, F des n Tensile reliability strength with a certain confidence level; SD F is the standard squared deviation; k is a constant corresponding to each failure probability.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] This invention discloses a method for determining the tensile reliability strength of oil pipes. It obtains connection strength calculation parameters through experiments, resulting in high accuracy of the tensile reliability calculation parameters. By calculating the yield strength of the pipe connection and the tensile strength of the pipe under the limit state equation, the uncertainty of the model obtained from the experimental values ​​and calculated values ​​effectively improves the accuracy of the tensile reliability calculation results. By obtaining the tensile strength and standard square deviation of the pipe body and calculating the tensile reliability strength, the dispersion of the tensile reliability calculation results is reduced. The reliability of the tensile reliability determination method is effectively improved by performing finite element analysis and evaluation on the reliability strength calculation results, and by verifying and evaluating the reliability strength calculation results through physical tensile tests. By considering the model uncertainty and using the limit state equation corresponding to the pipe body yield strength, the tensile strength of the oil casing is calculated using the first second moment method, and then the tensile reliability strength of the oil casing is calculated. This provides a new and scientific method for determining tensile reliability strength and provides technical support for tensile strength issues in the reliability design of tubing strings. Simultaneously, it has certain guiding significance for differentiated tubing string design, quantitative quality control of oil casing, quantitative risk management of oil casing, and ultimate strength and failure analysis of oil casing. Attached Figure Description

[0042] Figure 1 A flowchart illustrating the method for determining the tensile reliability strength of oil casing;

[0043] Figure 2 This is a reliability and strength verification diagram for a Φ88.90×6.45mm 110 tubing.

[0044] Figure 3 This is a reliability and strength verification diagram for a Φ177.80×10.36mm BG110 bushing. Detailed Implementation

[0045] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings:

[0048] To provide a scientific and fundamental basis for determining the tensile reliability strength of oil pipeline materials, this invention proposes a method for determining the tensile reliability strength of oil pipeline materials. Based on the historical API formula for calculating the yield strength of pipe bodies, this method uses the limit state equation corresponding to the tensile yield strength of the pipe body, considers model uncertainties, and calculates the tensile strength of the oil casing using the first-order second-moment method. Furthermore, it calculates the tensile reliability strength of the oil casing, and verifies and evaluates the results using finite element analysis and physical experiments. This invention effectively solves the problem of lacking a scientific method for determining tensile reliability strength.

[0049] See Figure 1 The technical method and implementation steps provided by this invention are as follows:

[0050] A method for determining the tensile reliability strength of oil pipe materials, the technical method and steps are as follows:

[0051] 1) Perform geometric dimension measurements and material tensile tests on the oil casing and obtain key parameters for connection strength calculation (average outer diameter, average wall thickness, and material tensile strength) through statistical analysis.

[0052] 2) Calculation of yield strength of pipe connection (API formula):

[0053] F YAPI =f ymn A p (1)

[0054] Among them, F YAPI Indicates the yield strength of the pipe body, in kN; f ymn Indicates the specified minimum yield strength, MPa; A p This indicates the cross-sectional area of ​​the tube, in mm. 2 .

[0055] 3) The corresponding limit state equation:

[0056] F = πf y (Dt)t (2)

[0057] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; and t represents the average wall thickness, in mm.

[0058] 4) Obtain the model uncertainty based on the actual test values / calculated values ​​of oil casing and tubing of the same manufacturer, batch, and specifications. Then, the formula for calculating the tensile strength of the pipe body connection is:

[0059] F = m u πf y (Dt)t (3)

[0060] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; t represents the average wall thickness, in mm; m u This represents the model uncertainty.

[0061] 5) Perform a first-order partial differential calculation using the method of second moments on formula (3):

[0062]

[0063]

[0064]

[0065]

[0066] According to f y The formula for calculating the F-distribution from the distributions of t and D is:

[0067]

[0068]

[0069] Where SDF is the standard deviation of squares, KN ​​is the standard deviation of squares, and mu is the model uncertainty. The average tensile strength of the material is expressed in MPa. The average outer diameter is in mm. The average wall thickness is in mm.

[0070] 6) Tensile reliability strength calculation:

[0071] F des n =Fk*SD F (7)

[0072] Among them, Fdes n For a certain level of confidence, Fdes0.95 represents the tensile reliability strength with a 95% confidence level when n is 0.95, corresponding to a target reliability level of 0.5%; SD F Let KN be the standard squared deviation; k is a constant corresponding to each failure probability.

[0073] 7) Perform finite element analysis and evaluation on the reliability strength calculation results; verify and evaluate the reliability strength calculation results through physical tensile tests;

[0074] 8) Compare the finite element analysis results with the actual tensile test results. If they are consistent, output the calculated tensile reliability strength. If they are inconsistent, recalculate.

[0075] This invention discloses a method for determining the tensile reliability strength of oil pipes. By considering the model uncertainty and using the limit state equation corresponding to the yield strength of the pipe body, the tensile strength of the oil casing is calculated using the first second moment method, and then the tensile reliability strength of the oil casing is calculated. This provides a new and scientific method for determining the tensile reliability strength, and solves the problem that the existing API pipe yield strength calculation method cannot accurately reflect the strength differences of oil casings of different qualities, which has brought many difficulties to the strength design and application of oil casings.

[0076] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0077]

Example 1

[0078] Determination of the tensile reliability strength of Φ88.90×6.45mm 110 tubing

[0079] Implementation process:

[0080] 1) Geometric dimensions and tensile tests were performed on Φ88.90×6.45mm 110 oil tubing, with specimen numbers 1Y and 2Y;

[0081] The average outer diameter of sample 1Y was 89.25 mm and the average wall thickness was 6.79 mm.

[0082] The average outer diameter of sample 2Y is 89.44 mm, and the average wall thickness is 6.60 mm.

[0083] The tensile strength of both specimen 1Y and specimen 2Y is 852 MPa.

[0084] 2) Calculate the yield strength of the pipe connection according to the API formula:

[0085] F YAPI =f ymn A p (1)

[0086] Among them, F YAPI Indicates the yield strength of the pipe body, in kN; f ymn Indicates the specified minimum yield strength, MPa; A p This indicates the cross-sectional area of ​​the tube, in mm. 2 .

[0087] 3) Calculate the tensile strength of the pipe under the limit state equation;

[0088] The corresponding limit state equations are:

[0089] F = πf y (Dt)t (2)

[0090] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; and t represents the average wall thickness, in mm.

[0091] The model uncertainty is obtained by dividing the experimental value by the calculated value. Therefore, the formula for calculating the tensile strength of the pipe connection is:

[0092] F = m u πf y (Dt)t (3)

[0093] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; t represents the average wall thickness, in mm; m u For model uncertainty;

[0094] Perform a first-order partial differential calculation using the method of second moments on formula (3):

[0095]

[0096]

[0097]

[0098]

[0099] Substituting the data, the model uncertainty is 0.98387 and the standard deviation of squares is 0.00303.

[0100] 4) Calculate the pipe connection strength using formulas (5) and (6);

[0101] According to f y The formula for calculating the F-distribution from the distributions of t and D is:

[0102]

[0103]

[0104] Where SDF is the standard deviation of squares, KN ​​is the standard deviation of squares, and mu is the model uncertainty. The average tensile strength of the material is expressed in MPa. The average outer diameter is in mm. The average wall thickness is in mm.

[0105] The tube connection strength of sample 1Y is 1475KN, and the standard deviation of squares is 30.3KN;

[0106] The tube connection strength of sample 2Y is 1506 kN, and the standard deviation of squares is 37.0 kN.

[0107] 5) Calculate the tensile reliability strength using formula (7);

[0108] F des n =Fk*SD F (7)

[0109] Among them, F des n Tensile reliability strength with a certain confidence level; SD F Let K be the standard deviation of squares, KN; and k be a constant corresponding to each failure probability.

[0110] The tensile reliability strength TRL0.005 of specimen 1Y is 1397 kN;

[0111] The tensile reliability strength TRL0.005 of specimen 2Y is 1411 kN.

[0112] 6) Obtained through finite element analysis:

[0113] The tensile strength of specimen 1Y is 1475 kN;

[0114] The tensile strength of specimen 2Y is 1509 kN.

[0115] 7) Obtained through physical experiments:

[0116] The tensile strength of specimen 1Y is 1502 kN;

[0117] The tensile strength of specimen 2Y is 1453 kN.

[0118]

Example 2

[0119] Determination of the tensile reliability strength of Φ177.80×10.36mm 110 sleeve

[0120] Implementation process:

[0121] 1) Geometric dimensions and tensile tests were performed on the Φ177.80×10.36mm 110 sleeve, with specimen numbers 1Y and 2Y;

[0122] The average outer diameter of sample 1Y was 179.30 mm and the average wall thickness was 10.61 mm.

[0123] The average outer diameter of sample 2Y is 179.08 mm, and the average wall thickness is 10.70 mm.

[0124] The tensile strength of the material in specimen 1Y is 1001 MPa;

[0125] The tensile strength of the material in specimen 2Y is 983 MPa.

[0126] 2) Calculate the yield strength of the pipe connection according to the API formula:

[0127] F YAPI =f ymn A p (1)

[0128] Among them, F YAPI Indicates the yield strength of the pipe body, in kN; f ymn Indicates the specified minimum yield strength, MPa; A p This indicates the cross-sectional area of ​​the tube, in mm. 2 .

[0129] 3) Calculate the tensile strength of the pipe under the limit state equation;

[0130] The corresponding limit state equations are:

[0131] F = πf y (Dt)t (2)

[0132] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; and t represents the average wall thickness, in mm.

[0133] Based on the model uncertainty obtained from the ratio of experimental values ​​to calculated values, the formula for calculating the tensile strength of the pipe connection is as follows:

[0134] F = m u πf y (Dt)t (3)

[0135] Where F is the tensile strength of the pipe body, in kN; f y t represents the tensile strength of the material, in MPa; D represents the average outer diameter, in mm; t represents the average wall thickness, in mm; m u For model uncertainty;

[0136] Perform a first-order partial differential calculation using the method of second moments on formula (3):

[0137]

[0138]

[0139]

[0140]

[0141] Substituting the data, the model uncertainty is 0.98295 and the standard deviation of squares is 0.01667.

[0142] 4) Calculate the pipe connection strength using formulas (5) and (6);

[0143] According to f y The formula for calculating the F-distribution from the distributions of t and D is:

[0144]

[0145]

[0146] Where SDF is the standard deviation of squares, KN ​​is the standard deviation of squares, and mu is the model uncertainty. The average tensile strength of the material is expressed in MPa. The average outer diameter is in mm. The average wall thickness is in mm.

[0147] The tube connection strength of sample 1Y is 5521 kN, and the standard deviation of squares is 112.6 kN.

[0148] The tube connection strength of sample 2Y is 5475KN, and the standard deviation of squares is 109.3KN.

[0149] 5) Calculate the tensile reliability strength using formula (7);

[0150] F des n =Fk*SD F (7)

[0151] Among them, F des n Tensile reliability strength with a certain confidence level; SD F Let K be the standard deviation of squares, KN; and k be a constant corresponding to each failure probability.

[0152] The tensile reliability strength (TRL0.005) of specimen 1Y is 52131 kN;

[0153] The tensile reliability strength TRL0.005 of specimen 2Y is 5193 kN.

[0154] 6) Obtained through finite element analysis:

[0155] The tensile strength of specimen 1Y is 5549 kN;

[0156] The tensile strength of specimen 2Y is 5502 kN.

[0157] 7) Obtained through physical experiments:

[0158] The tensile strength of specimen 1Y is 5374 kN;

[0159] The tensile strength of specimen 2Y is 5397 kN.

[0160] Implementation Results: As shown in Examples 1 and 2, through verification by physical experiments and finite element analysis, at a reliability level TRL = 0.5%, the calculated tensile reliability strength is less than both the physical experiment value and the finite element analysis value. The physical experiment value and the finite element analysis value are essentially consistent, verifying the reliability of the strength reliability theoretical calculation method of this invention. This method scientifically and accurately determined the tensile reliability strength of Φ88.90×6.45mm 110 tubing and Φ177.80×10.36mm 110 casing.

[0161] See Figure 2 This is a reliability and strength verification diagram for a Φ88.90×6.45mm 110 oil tubing. Figure 3The figure shows the reliability strength verification diagram of a Φ177.80×10.36mm BG110 casing. As can be seen from the figure, the method for determining the tensile reliability strength of oil pipes disclosed in this invention, using physical experiments and finite element calculations, verifies that when the reliability level TRL = 0.5%, the calculated tensile reliability strength value is less than both the physical experiment value and the finite element calculation value. The physical experiment value and the finite element calculation value are basically consistent, verifying the reliability of the tensile reliability determination method of this invention. This invention obtains the connection strength calculation parameters through experiments, resulting in high accuracy of the tensile reliability calculation parameters. By calculating the yield strength of the pipe connection and the tensile strength of the pipe under the limit state equation, the model uncertainty obtained from the physical experiment value and the calculated value effectively improves the tensile reliability. The accuracy of the calculation results is improved by obtaining the tensile strength and standard square deviation of the pipe body and calculating the tensile reliability strength, resulting in small dispersion of the tensile reliability calculation results. The reliability of the tensile reliability determination method is effectively improved by performing finite element analysis and evaluation of the reliability strength calculation results, and by verifying and evaluating the results through physical tensile tests. By considering the model uncertainty and using the limit state equation corresponding to the yield strength of the pipe body, the tensile strength of the oil casing is calculated using the first second moment method, and then the tensile reliability strength of the oil casing is calculated. This provides a new and scientific method for determining the tensile reliability strength and provides technical support for the tensile strength aspects of tubing string reliability design. It also solves the problem that the existing API pipe yield strength calculation method cannot accurately reflect the strength differences of oil casing of different qualities, which has brought many difficulties to the strength design and application of oil casing.

[0162] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for determining the tensile reliability strength of oil pipes, characterized in that, include: Step 1: Obtain connection strength calculation parameters through experiments; Step 2: Calculate the yield strength of the pipe connection based on the connection strength calculation parameters; Step 3: Calculate the tensile strength of the pipe body under the limit state equation based on the yield strength of the pipe body connection; Step 4: Obtain the model uncertainty based on the experimental values ​​and the tensile strength of the tube body; Step 5: Based on the model uncertainty, perform a second-order partial differential equation calculation to obtain the tensile strength and standard squared deviation of the pipe body; Step Six: Calculate the tensile reliability strength using the pipe's tensile strength and standard square deviation; Step 7: Perform finite element analysis and evaluation on the reliability strength calculation results, and verify and evaluate them through physical tensile tests; Step 8: Compare the finite element analysis results with the actual tensile test results. If they are consistent, output the calculated tensile reliability strength. If they are inconsistent, recalculate.

2. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, In step one, the geometric dimensions of the oil casing and the material tensile test are performed, and the parameters for calculating the connection strength are obtained through statistical analysis.

3. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, In step one, the parameters include average outer diameter, average wall thickness, and material tensile strength.

4. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, In step two, the yield strength of the pipe connection is calculated according to the API formula: F YaPI =f ymn A p (1) Among them, F YAPI Indicates the yield strength of the tube; f ymn Indicates the specified minimum yield strength; A p This indicates the cross-sectional area of ​​the tube.

5. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, In step three, the limit state equation is: F = πf y (Dt)t (2) where, F represents the tensile strength of the pipe body; f y t represents the tensile strength of the material; D represents the average outer diameter; and t represents the average wall thickness.

6. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, In step four, the model uncertainty is obtained by comparing the actual test values ​​with the calculated values ​​of oil casing pipes of the same manufacturer, batch, and specifications.

7. The method for determining the tensile reliability strength of oil pipes according to claim 6, characterized in that, In step four, the formula for calculating the tensile strength of the pipe connection is: F=m u πf y (D-t)t (3) Where F is the tensile strength of the pipe body; f y D is the tensile strength of the material; D is the average outer diameter; t is the average wall thickness; m u This represents the model uncertainty.

8. The method for determining the tensile reliability strength of oil pipes according to claim 7, characterized in that, After performing a second-order partial differential calculation using the method of moments on formula (3), according to f y The formula for calculating the F-distribution from the distributions of t and D is: Among them, SD F The standard deviation of squares; m u For model uncertainty; This represents the average tensile strength of the material. The average outer diameter; This represents the average wall thickness.

9. The method for determining the tensile reliability strength of oil pipes according to claim 6, characterized in that, Perform a first-order partial differential calculation using the method of second moments on formula (3): Among them, f y t represents the tensile strength of the material; D represents the average outer diameter; t represents the average wall thickness; m represents the average wall thickness. u This represents the model uncertainty.

10. The method for determining the tensile reliability strength of oil pipes according to claim 1, characterized in that, Tensile reliability strength calculation: F des n =F-k*SD F (7) Among them, F des n Tensile reliability strength with a certain confidence level; SD F is the standard squared deviation; k is a constant corresponding to each failure probability.

Images