Fatigue damage evaluation method and device for fatigue hot spot of rubber core on wellhead rotary blowout preventer

Abstract

The present application relates to the technical field of rubber core fatigue damage evaluation, and is a rubber core fatigue hot spot fatigue damage evaluation method and device for a wellhead rotary blowout preventer, comprising taking the rubber core material of the wellhead rotary blowout preventer as a sample, performing a drilling working condition simulation experiment on the sample; establishing an evaluation standard of the correlation between the interference pressure and the rubber core fatigue damage grade in the whole life cycle; collecting the interference pressure between the rubber core and the drill pipe in real time, and obtaining the fatigue damage grade corresponding to the interference pressure by referring to the evaluation standard. The present application can judge the fatigue damage grade of the rubber core by collecting the interference pressure between the rubber core and the drill pipe, combining the evaluation standard of the correlation between the interference pressure and the rubber core fatigue damage grade, and collecting the interference pressure, so as to accurately monitor the service life of the rubber core, grasp the replacement time of the rubber core, and avoid waste of the rubber core.

Description

Technical Field

[0001] This invention relates to the field of fatigue damage assessment technology for rubber cores, and is a method and device for assessing fatigue damage at fatigue hotspots on the rubber core of a wellhead rotary blowout preventer. Background Technology

[0002] In today's underbalanced drilling and precision pressure controlled drilling and completion operations, the rotary control head (i.e., the wellhead rotary blowout preventer) plays a crucial role in ensuring well control. The sealing core (i.e., the sealing insert), as a key component, directly affects well control safety, and the quantity used is closely linked to economic benefits. However, several problems exist in practical applications. First, due to variations in the performance of sealing cores, some substandard cores may fail before reaching their rated service life, leading to poor sealing and potentially triggering emergencies, significantly increasing the workload for the drilling team in handling such incidents. Second, when encountering complex drilling conditions, frequent replacement of the sealing core is necessary to ensure well control safety, which not only increases operating costs but also significantly reduces economic efficiency.

[0003] Traditional methods for replacing rubber cores primarily rely on analyzing current operating conditions and determining whether each core should be replaced based on its rated service life. However, this method cannot accurately assess the degree of fatigue damage to the core in a digital form. Therefore, a novel basis for determining core replacement is urgently needed: judging the degree of fatigue damage at fatigue hotspots of the rotary blowout preventer's rubber core based on interference pressure. Summary of the Invention

[0004] This invention provides a method and apparatus for assessing fatigue damage at fatigue hotspots on the rubber core of a wellhead rotary blowout preventer. It can assess the degree or level of fatigue damage to the rubber core of the wellhead rotary blowout preventer based on the interference pressure data monitored by the pressure sensor.

[0005] One of the technical solutions of this invention is achieved through the following measures: a method for assessing fatigue damage at fatigue hotspots on the rubber core of a wellhead rotary blowout preventer, comprising:

[0006] Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment was conducted on the sample. The simulation experiment covered the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state.

[0007] During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle were obtained;

[0008] Establish an evaluation standard that correlates interference pressure throughout the entire life cycle with the fatigue damage level of the adhesive core;

[0009] The interference pressure between the rubber core and the drill pipe is collected in real time, and the fatigue damage level corresponding to the interference pressure is obtained by referring to the evaluation criteria.

[0010] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions:

[0011] Furthermore, the fatigue damage level of the aforementioned upper core is determined based on the deformation rate ε and the attenuation rate R of the elastic modulus. E Divided into low, medium, and high levels, low level: ε < 8%, R E ≤10%; Medium level: ε is 8% to 25%, R E 10% to 50%; High level: ε > 25%, R E >50%.

[0012] Furthermore, when the core material is nitrile rubber, the interference pressure P I The evaluation criteria associated with the fatigue damage level of the adhesive core are as follows:

[0013] Low level: P I ≥8.0×10 9 Pa; Medium grade: 3.0 × 10 9 Pa <P I <8.0×10 9 Pa; High grade: P≤3.0×10 9 Pa.

[0014] Furthermore, a pressure sensor is fixedly installed on the outside of the aforementioned glue core, and the interference pressure between the glue core and the drill rod is collected by the pressure sensor.

[0015] Furthermore, the interference pressure between the collected adhesive core and the drill pipe was verified using the following method:

[0016] Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core.

[0017] When ε < 15% ;

[0018] When 15%≤ε<50% ;

[0019] In the formula, P I ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

[0020] By verifying the interference pressure collected between the glue core and the drill rod, the effectiveness of the interference pressure (collected by the pressure sensor) is improved, avoiding the use of the pressure collected by the faulty pressure sensor as the interference pressure for determining the fatigue damage level of the glue core when the pressure sensor fails.

[0021] Verification work can be carried out from the beginning of the glue core approaching fatigue state, and the frequency of verification work should be increased when it is about to fail.

[0022] The second technical solution of the present invention is achieved through the following measures: an apparatus for evaluating fatigue damage at fatigue hot spots of the rubber core of a wellhead rotary blowout preventer as described in the first technical solution, comprising:

[0023] Simulation module: Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment is conducted on the sample. The simulation experiment covers the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state.

[0024] Parameter acquisition module: During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle are obtained;

[0025] Standard establishment module: Establish evaluation standards for the correlation between interference pressure and fatigue damage level of the glue core throughout the entire life cycle;

[0026] Evaluation module: Real-time acquisition of the interference pressure between the glue core and the drill pipe, and obtaining the fatigue damage level corresponding to the interference pressure by referring to the evaluation criteria.

[0027] The following are further optimizations and / or improvements to the second technical solution of the above invention:

[0028] Furthermore, in the aforementioned standard establishment module, the fatigue damage level of the upper adhesive core is determined based on the deformation rate ε and the attenuation rate R of the elastic modulus. E Divided into low, medium, and high levels, low level: ε < 8%, R E ≤10%; Medium level: ε is 8% to 25%, R E 10% to 50%; High level: ε > 25%, R E >50%.

[0029] Furthermore, in the aforementioned standard establishment module, when the core material is nitrile rubber, the interference pressure P... I The evaluation criteria associated with the fatigue damage level of the adhesive core are as follows:

[0030] Low level: P I ≥8.0×10 9 Pa; Medium grade: 3.0 × 10 9Pa <P I <8.0×10 9 Pa; High grade: P≤3.0×10 9 Pa.

[0031] Furthermore, in the aforementioned evaluation module, a pressure sensor is fixedly installed on the outside of the glue core, and the interference pressure between the glue core and the drill pipe is collected by the pressure sensor.

[0032] Furthermore, in the aforementioned evaluation module, the interference pressure between the collected adhesive core and the drill pipe is verified using the following method:

[0033] Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core.

[0034] When ε < 15% ;

[0035] When 15%≤ε<50% ;

[0036] In the formula, P I ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

[0037] This invention collects the interference pressure between the rubber core and the drill pipe in real time. Combined with an evaluation standard that correlates the interference pressure with the fatigue damage level of the rubber core, the collected interference pressure can be used to determine the fatigue damage level of the rubber core. This allows for precise monitoring of the rubber core's service life, identifying the optimal replacement time, and avoiding waste. Furthermore, this invention has excellent field implementation conditions and can fully meet actual field needs. It has significant guiding significance for underbalanced drilling and precision pressure controlled drilling and completion operations, demonstrating great potential for widespread application. Attached Figure Description

[0038] Appendix Figure 1 A top view diagram showing the pressure sensor fixedly installed on the outside of the adhesive core.

[0039] The codes in the attached diagram are as follows: 1 is the drill pipe, 2 is the interference contact surface, 3 is the glue core, 4 is the pressure sensor, and 5 is the digital display device. Detailed Implementation

[0040] The present invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of the present invention.

[0041] The terminology involved in this invention is explained as follows:

[0042] Fatigue hotspots in the rubber core are localized areas of high damage caused by stress concentration or material defects under dynamic loads.

[0043] The digital display device can be a display screen or other existing digital display equipment.

[0044] The method described in this invention can prevent wellbore pressure runaway due to poor sealing of the rubber core during drilling and completion, while reducing the cost of using the rubber core while ensuring well control safety, thus improving the utilization efficiency of the rubber core.

[0045] The present invention will be further described below with reference to embodiments:

[0046] Example 1: A method for assessing fatigue damage at fatigue hotspots on the rubber core of the wellhead rotary blowout preventer, including:

[0047] Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment was conducted on the sample. The simulation experiment covered the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state.

[0048] During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle were obtained;

[0049] Establish an evaluation standard that correlates interference pressure throughout the entire life cycle with the fatigue damage level of the adhesive core;

[0050] The interference pressure between the rubber core and the drill pipe is collected in real time, and the fatigue damage level corresponding to the interference pressure is obtained by referring to the evaluation criteria.

[0051] The drilling conditions include temperature and drill pipe movement frequency.

[0052] Example 2: As an optimization of the above example, the fatigue damage level of the upper core is determined based on the deformation rate ε and the attenuation rate R of the elastic modulus. E Divided into low, medium, and high levels, low level: ε < 8%, R E ≤10%; Medium level: ε is 8% to 25%, R E 10% to 50%; High level: ε > 25%, R E >50%.

[0053] Example 3: As an optimization of the above examples, when the core material is nitrile rubber, the interference pressure P I The evaluation criteria associated with the fatigue damage level of the adhesive core are as follows:

[0054] Low level: P I≥8.0×10 9 Pa; Medium grade: 3.0 × 10 9 Pa <P I <8.0×10 9 Pa; High grade: P≤3.0×10 9 Pa.

[0055] Example 4: As an optimization of the above embodiment, a pressure sensor is fixedly installed on the outside of the upper rubber core, and the interference pressure between the upper rubber core and the drill rod is collected by the pressure sensor. Based on the interference fit between the rubber core and the drill rod, and according to the mechanical transmission of rubber material, the pressure on the inner side of the upper rubber core is equal to the pressure measured on its outer side. Therefore, by fixing a pressure sensor on the outside of the upper rubber core, the interference pressure between the rubber core and the drill rod can be collected.

[0056] Example 5: As an optimization of the above examples, the interference pressure between the collected adhesive core and the drill rod is verified. The verification method is as follows:

[0057] Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core.

[0058] When ε < 15% ;

[0059] When 15%≤ε<50% ;

[0060] In the formula, P I ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

[0061] Example 6: An apparatus for assessing fatigue damage at fatigue hotspots on the rubber core of the wellhead rotary blowout preventer, comprising:

[0062] Simulation module: Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment is conducted on the sample. The simulation experiment covers the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state.

[0063] Parameter acquisition module: During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle are obtained;

[0064] Standard establishment module: Establish evaluation standards for the correlation between interference pressure and fatigue damage level of the glue core throughout the entire life cycle;

[0065] Evaluation module: Real-time acquisition of the interference pressure between the glue core and the drill pipe, and obtaining the fatigue damage level corresponding to the interference pressure by referring to the evaluation criteria.

[0066] Example 7: As an optimization of Example 6 above, in the standard establishment module, the fatigue damage level of the upper core is determined based on the deformation rate ε and the attenuation rate R of the elastic modulus. E Divided into low, medium, and high levels, low level: ε < 8%, R E ≤10%; Medium level: ε is 8% to 25%, R E 10% to 50%; High level: ε > 25%, R E >50%.

[0067] Example 8: As an optimization of Example 6 above, in the standard establishment module, when the core material is nitrile rubber, the interference pressure P I The evaluation criteria associated with the fatigue damage level of the adhesive core are as follows:

[0068] Low level: P I ≥8.0×10 9 Pa; Medium grade: 3.0 × 10 9 Pa <P I <8.0×10 9 Pa; High grade: P≤3.0×10 9 Pa.

[0069] Example 9: As an optimization of Example 6 above, in the evaluation module, a pressure sensor is fixedly installed on the outside of the glue core, and the interference pressure between the glue core and the drill rod is collected by the pressure sensor.

[0070] Example 10: As an optimization of Example 9 above, the evaluation module verifies the interference pressure between the collected adhesive core and the drill rod. The verification method is as follows:

[0071] Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core.

[0072] When ε < 15% ;

[0073] When 15%≤ε<50% ;

[0074] In the formula, PI ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

[0075] The following are experimental research data for this invention:

[0076] Basic Information for the Experiment

[0077] Sample specifications: Nitrile rubber is the core material for conventional wellhead rotary blowout preventers, with a thickness h=20mm (error ±0.05mm) and a volume V=5×10. -4 m³, 5 parallel samples per group, the average value is taken as experimental data, and each table represents one group of sample data.

[0078] Experimental equipment: electronic universal testing machine (accuracy 0.01MPa), simulated drilling condition test bench (including temperature / pressure control module), high-precision pressure sensor (accuracy 0.1% FS). The high-precision pressure sensor is used to collect the interference pressure of the rubber core sample.

[0079] The core experimental phases include: determination of basic mechanical parameters (initial state), dynamic fatigue attenuation test (fatigue state), and verification of sealing critical threshold (failure state). The experiments cover the entire life cycle from initial to fatigue to failure.

[0080] Experimental Data Recording

[0081] (1) The basic mechanical parameters of the sample with the glue core in the initial state (t=0h, temperature 25℃) are shown in Table 1.

[0082] Table 1

[0083] .

[0084] (2) The results of the dynamic fatigue decay test of the glued core sample are shown in Table 2. Dynamic fatigue decay test: t=200h, temperature 50℃, drill rod movement frequency is 1 time / min.

[0085] Table 2

[0086] .

[0087] (3) The results of dynamic fatigue decay of the glued core sample are shown in Table 3. Dynamic fatigue decay test: t=600h, temperature 60℃, drill rod movement frequency is 1 time / min.

[0088] Table 3

[0089] .

[0090] (4) The sealing critical threshold verification of the glue core sample is shown in Table 4. Sealing critical threshold verification: t=800h, temperature 65℃, gradually reduce the interference pressure.

[0091] Table 4

[0092] .

[0093] III. Experimental Data Processing and Analysis

[0094] (1) Verification of basic mechanical parameters: consistency between calculated values ​​and measured values.

[0095] Taking the adhesive core sample numbered 1-1 in Table 1 (initial state) as an example, substituting E=2.0×10¹¹Pa and ε=4% into the formula, we obtain P. I =2.0×10¹¹×0.04=8.0×10 9 Pa is basically consistent with the average value of the interference pressure measured in Table 1.

[0096] (2) Analysis of fatigue decay law: trend of parameter change over time

[0097] Table 5 shows the average data from Tables 1 to 4. As can be seen from Table 5, the parameters change to varying degrees over time.

[0098] Table 5

[0099] .

[0100] (3) Fatigue level classification verification:

[0101] Based on the above experimental data, the correspondence between "interference pressure and fatigue damage level" was verified, as shown in Table 6.

[0102] Table 6

[0103] .

[0104] (4) Determination of sealing critical threshold

[0105] As shown in Table 4, when the leakage rate Q = 5 mL / min (the on-site failure criterion), the corresponding average interference pressure is 3.0 × 10⁻⁶. 9 Pa can serve as the core basis for on-site rubber core replacement.

[0106] The experimental data above verified the correlation between interference pressure and fatigue damage degree, clarified the interference pressure thresholds corresponding to low, medium, and high fatigue levels, and the interference pressure P... I =3×10 9 Pa can be used directly for on-site decision-making regarding whether the adhesive core has failed.

[0107] Application Recommendation: When monitoring interference pressure on-site, when P I ≥8×10 9When Pa, monitor according to the regular cycle; 3×10 9 Pa <P I <8×10 9 When Pa, shorten the sampling interval to once every 2 hours; P I ≤3×10 9 If the pressure reaches Pa, immediately stop the machine and replace the rubber core.

[0108] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for assessing fatigue damage at fatigue hotspots on the rubber core of a wellhead rotary blowout preventer, characterized in that, include: Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment was conducted on the sample. The simulation experiment covered the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state. During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle were obtained; Establish an evaluation standard that correlates interference pressure throughout the entire life cycle with the fatigue damage level of the adhesive core; The interference pressure between the glue core and the drill pipe is collected in real time, and the fatigue damage level corresponding to the interference pressure is obtained by referring to the evaluation criteria. wherein the gummed core fatigue damage level is classified according to the strain rate ε and the attenuation rate R of the elastic modulus E Low grade: ε < 8%, R E ≤ 10%; middle grade: ε is 8% to 25%, R E is 10% to 50%; high grade: ε > 25%, R E > 50%. When the gummed core material is nitrile rubber, the interference pressure P I The evaluation criteria associated with the gummed core fatigue damage rating are as follows: Low: P I ≥ 8.0 x 10 9 Pa; Medium: 3.0 x 10 9 Pa < P I < 8.0 x 10 9 Pa; High: P I ≤ 3.0 x 10 9 Pa; A pressure sensor is fixedly installed on the outside of the glue core. The interference pressure between the glue core and the drill pipe is collected by the pressure sensor. The collected interference pressure between the glue core and the drill pipe is verified by the following method: Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core. When ε < 15% ; When 15%≤ε<50% ; In the formula, P I ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

2. An apparatus for assessing fatigue damage at fatigue hotspots on the rubber core of a wellhead rotary blowout preventer as described in claim 1, characterized in that, include: Simulation module: Using the core material of the wellhead rotary blowout preventer as a sample, a drilling condition simulation experiment is conducted on the sample. The simulation experiment covers the entire life cycle change process of the core material from the initial state to the fatigue state and finally to the failure state. Parameter acquisition module: During the drilling condition simulation experiment, the deformation rate, elastic modulus and interference pressure of the sample throughout its entire life cycle are obtained; Standard establishment module: Establish evaluation standards for the correlation between interference pressure and fatigue damage level of the glue core throughout the entire life cycle; Evaluation module: Real-time acquisition of the interference pressure between the glue core and the drill pipe, and obtaining the fatigue damage level corresponding to the interference pressure by referring to the evaluation criteria.

3. The apparatus according to claim 2, characterized in that, In the standard establishment module, the fatigue damage level of the upper adhesive core is determined based on the deformation rate ε and the attenuation rate of the elastic modulus R. E Divided into low, medium, and high levels, low level: ε < 8%, R E ≤10%; Medium level: ε is 8% to 25%, R E 10% to 50%; High level: ε > 25%, R E >50%.

4. The apparatus according to claim 3, characterized in that, In the standard setup module, when the core material is nitrile rubber, the interference pressure P is... I The evaluation criteria associated with the fatigue damage level of the adhesive core are as follows: Low level: P I ≥8.0×10 9 Pa; Medium level: 3.0×10 9 Pa <P I <8.0×10 9 Pa; High level: P I ≤3.0×10 9 Pa.

5. The apparatus according to claim 2, 3, or 4, characterized in that, In the evaluation module, a pressure sensor is fixedly installed on the outside of the glue core, and the interference pressure between the glue core and the drill pipe is collected by the pressure sensor.

6. The apparatus according to claim 5, characterized in that, In the evaluation module, the interference pressure between the glue core and the drill pipe is verified. The verification method is as follows: Using the measurement data of the deformation rate and elastic modulus of the upper core, the interference pressure is calculated according to the following formula. If the error between the calculated value of the interference pressure and the pressure collected by the pressure sensor is less than the error threshold, then the pressure collected by the pressure sensor is the interference pressure, and the pressure collected by the pressure sensor can be used to determine the fatigue damage level of the core. Otherwise, it is not the interference pressure, and the pressure collected by the pressure sensor cannot be used to determine the fatigue damage level of the core. When ε < 15% ; When 15%≤ε<50% ; In the formula, P I ε is the interference pressure; ε is the deformation rate; E is the elastic modulus.

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