A method for evaluating the working performance of the rubber core of a rotary blowout preventer

Abstract

The present invention discloses a method for evaluating the working performance of a rubber core of a rotary blowout preventer, which relates to the field of oil and gas development, and includes establishing a strain energy function of a rubber core material, which is defined as a first strain energy function; establishing a damage function of a rubber core material based on the Mullins effect, which is introduced into the first strain energy function to obtain a strain energy function that considers the Mullins effect, which is defined as a second strain energy function; preparing a sample with the rubber core material, performing a tensile test, and obtaining an actual stress-strain curve; fitting the second strain energy function based on the actual stress-strain curve to obtain the material parameters of the rubber core material; establishing a finite element model based on the material parameters; and simulating, and evaluating the working performance of the rubber core based on the simulation results. The present invention is used to solve the problem that it is difficult to evaluate the influence of the Mullins effect on the sealing performance of the rubber core of a rotary blowout preventer through existing technologies, and to achieve the purpose of evaluating the working performance of the rubber core under the premise of considering the Mullins effect, and providing a more accurate evaluation method for the safety of the rotary blowout preventer.

Description

Technical Field

[0001] The invention relates to the field of oil and gas development, and in particular to a method for evaluating the working performance of a rubber core of a rotary blowout preventer. Background Art

[0002] As a key well control equipment for deepwater drilling, the rotary blowout preventer (RBOP) isolates the wellbore annulus and drill pipe and provides effective pressure control. In overflow or well kick conditions, failure of the rotary blowout preventer will lead to serious blowout accidents and cause significant losses.

[0003] As the core sealing element of the rotary blowout preventer, the sealing effect and service life of the rubber core affect the safety and efficiency of drilling construction to a certain extent. The "Mullins effect" refers to the phenomenon that the rubber material exhibits stress softening under cyclic loading conditions, which is particularly evident during the multiple loading and unloading processes of the rubber material. During the service of the rubber core, the external manifestation of the Mullins effect is that during the tripping and drilling process, the reciprocating motion of the drill pipe causes the inner cone surface of the rubber core and the main sealing surface to be sunken to varying degrees, which will have a significant impact on the sealing performance and structural integrity of the rubber core.

[0004] The existing research on rotary blowout preventers rarely involves the changes in the sealing performance of the rubber core under the Mullins effect caused by the movement of the drill pipe. That is, it is difficult to evaluate the influence of the Mullins effect on the sealing performance of the rubber core of the rotary blowout preventer by existing technical means, which is not conducive to ensuring the reliability of the rubber core seal and the operational safety of the offshore drilling platform. Summary of the invention

[0005] The present invention provides a method for evaluating the working performance of a rubber core of a rotary blowout preventer, so as to solve the problem that it is difficult to evaluate the influence of the Mullins effect on the sealing performance of the rubber core of a rotary blowout preventer through the existing technology, so as to achieve the purpose of evaluating the working performance of the rubber core under the premise of considering the Mullins effect, and providing a more accurate evaluation method for the safety of the rotary blowout preventer.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for evaluating the working performance of a rotary blowout preventer rubber core comprises the following steps:

[0008] S1. Establish the strain energy function of the rubber core material, which is defined as the first strain energy function;

[0009] S2, establishing a damage function of the rubber core material based on the Mullins effect, introducing the damage function of the rubber core material based on the Mullins effect into the first strain energy function, and obtaining a strain energy function considering the Mullins effect, which is defined as a second strain energy function;

[0010] S3, prepare the sample with the rubber core material, do the tensile test, and obtain the actual stress-strain curve;

[0011] S4, fitting the second strain energy function based on the actual stress-strain curve to obtain material parameters of the rubber core material;

[0012] S5. Establish a finite element model based on the material parameters of the rubber core material;

[0013] S6. Simulation, evaluating the working performance of the rubber core based on the simulation results.

[0014] In view of the problem that it is difficult to evaluate the influence of the Mullins effect on the sealing performance of the rubber core of a rotary blowout preventer in the prior art, the present invention proposes a method for evaluating the working performance of the rubber core of a rotary blowout preventer. The method first establishes a strain energy function of the rubber core material based on the material of the rubber core of the rotary blowout preventer, and defines it as the first strain energy function; then, based on the Mullins effect, establishes a damage function of the rubber core material; then, obtains the strain energy function considering the Mullins effect, and defines it as the second strain energy function, which includes several material parameters to be solved. Afterwards, a sample is prepared using the same material as the rubber core of the rotary blowout preventer, and a tensile test is performed to obtain an actual stress-strain curve; based on the data obtained from the actual stress-strain curve, the second strain energy function is fitted to obtain the material parameters of the rubber core material. Afterwards, a finite element model of the rubber core can be established, the material parameters are assigned therein, simulation is performed, the simulation results are obtained, and the working performance of the rubber core is evaluated.

[0015] It can be seen that the present application introduces a damage function based on the Mullins effect, and obtains the strain energy function of the rubber core material to be solved. The strain energy function is solved in combination with the tensile test, so that the material parameters taking into account the Mullins effect can be obtained, and then a finite element simulation is performed based on the obtained material parameters, and the sealing performance of the rubber core is evaluated based on the simulation results. The entire evaluation process fully considers the influence of the Mullins effect on the sealing performance of the rubber core of the rotary blowout preventer, overcomes the shortcomings of the prior art, and provides a more scientific and accurate method for the safety evaluation of the rotary blowout preventer, which is conducive to improving the operational safety of offshore drilling platforms and reducing safety hazards.

[0016] Furthermore, the first strain energy function is:

[0017] ;

[0018] Where: is the strain energy density on the main loading path; k , jTo control the power exponents of different terms in the formula, the order of polynomial expansion of strain invariants is expressed; N is the order; C kj is the material parameter of the deviatoric part; is the partial first strain invariant; is the partial second strain invariant; J el is the elastic volume ratio of the material; D k is a parameter related to volume response.

[0019] Those skilled in the art should understand that the main loading path in this solution refers to the path along which the material responds as stress or strain increases during the tensile test. C kj and k , j They can all be understood as distortion response related parameters.

[0020] Those skilled in the art will appreciate that the unloading path is opposite to the main loading path, and refers to the response path exhibited by the material when loading stops and begins to reduce the load. The control formula in this solution refers to a specific mathematical expression used to describe and control the behavior of the material (such as the specific form of the strain energy density function).

[0021] It should be understood by those skilled in the art that the material parameters of the deviator part and the volume response related parameters are parameters related to the material itself, and those skilled in the art can obtain them according to the existing technical means. For example, in a tensile test, the stress-strain curve can be measured to obtain the parameters related to the material itself. , The deviatoric strain response is directly related to , Relevant parts, such as , the material parameters of the deviatoric part can be extracted (such as C kj )and k , j .

[0022] Furthermore, the damage function of the rubber core material based on the Mullins effect is:

[0023] ;

[0024] Where: η is the damage variable; r , m and β All are material parameters; erf represents the Gaussian error function; Um is the maximum strain energy density during material loading; is the strain energy density on the main loading path.

[0025] In this scheme, r , m and ꞵ are the material parameters to be solved.

[0026] Based on the formula in this scheme, we can get about η Substituting the expression into the first strain energy function, we can get the second strain energy function.

[0027] Furthermore, step S3 specifically includes:

[0028] S301, preparing at least three dumbbell-shaped specimens; setting the initial stretching ratio to 0.5;

[0029] S302, performing four loading-unloading cycles on the dumbbell-shaped specimen;

[0030] S303, increase the stretching ratio by 0.5, and return to step S302, until four loading-unloading cycles with a stretching ratio of 2.5 are completed to obtain an actual stress-strain curve.

[0031] The rubber core material of the rotary blowout preventer will produce obvious stress softening phenomenon during the cyclic loading process. When experiencing loading, unloading, and reloading, the unloading stress and reloading stress are much smaller than the initial loading stress. When reloading, the stress-strain curve will first follow the last unloading path. When the reloading strain is greater than the historical maximum strain, the stress-strain curve returns to the main loading path. The residual strain generated after complete unloading to the zero stress state is permanent deformation. This permanent deformation will increase the possibility of sealing failure and affect the long-term use of the rubber core. Therefore, this scheme obtains cyclic stress-strain data under multiple tensile amplitudes, that is, the actual stress-strain curve, by subjecting multiple specimens to five different but fixed cyclic tensile loads. This is conducive to more accurate fitting of the second strain energy function to obtain more accurate material parameters that take into account the Mullins effect.

[0032] Furthermore, the establishing of the finite element model includes:

[0033] S501, respectively establishing geometric models of a rubber core, an iron frame and a drill rod, wherein the drill rod includes a drill rod coupling;

[0034] S502, assemble the iron frame on the outside of the rubber core, and allow the drill rod to pass through the rubber core;

[0035] S503, assigning material parameters of the rubber core material to the rubber core, and setting boundary conditions.

[0036] During the research process, the inventor of this case found that the shoulder of the drill pipe coupling would cause significant permanent deformation and stress softening on the lower part of the rubber core sealing surface. Therefore, the drill pipe geometric model established in this scheme needs to include the drill pipe coupling model, thereby improving the accuracy of subsequent simulations.

[0037] Furthermore, the setting boundary conditions includes:

[0038] Apply rigid body constraints to the drill rod and iron frame;

[0039] Set the contact between the rubber core and the drill pipe to limited slip; set the tangential contact friction model between the rubber core and the drill pipe to "penalty contact";

[0040] A fixed constraint is applied to the bolt hole area of ​​the rubber core, and wellhead pressure is applied to the outside of the rubber core.

[0041] When the rotary blowout preventer is closed on site and the drill is pulled up and down, the stress state of the rubber core is as follows: when the drill pipe passes through the wellhead, the rubber core is in a static sealing state, and its outer cylindrical cone surface is also subjected to the bottom hole hydraulic pressure. During the pressure drilling operation, the drill pipe moves downward. At this time, the rubber core is also subjected to the downward dynamic friction force caused by the downward movement of the drill pipe on the inner sealing surface. At this time, the rubber core is in an axial tensile deformation state. During the pulling up and down process, the drill pipe passes through the rubber core upward, and the inner surface of the rubber core is subjected to additional upward friction. At this time, the rubber core is in an axial compression deformation state. The boundary conditions set in this scheme can effectively simulate the above working process and improve the accuracy of the simulation results.

[0042] Furthermore, step S6 specifically includes:

[0043] S601, applying up and down reciprocating motion to the drill pipe, so that the drill pipe coupling passes through the rubber core during each upward and downward movement;

[0044] S602, taking the area from the top of the sealing surface between the rubber core and the drill pipe to the bottom of the rubber core as the data extraction path, determining the effective sealing section that reaches the required sealing pressure, and extracting the length and contact stress of each effective sealing section;

[0045] S603. Based on the contact length and contact stress of each effective sealing section, the sealing performance parameters are calculated to evaluate the working performance.

[0046] Under the action of wellhead hydraulic pressure, the contact length between the drill pipe and the rubber core of the rotary blowout preventer is much longer than the length of the main sealing surface. Therefore, this scheme uses the area from the top of the sealing surface to the bottom of the rubber core as the data extraction path, where the top of the sealing surface is the top of the inner surface of the rubber core. After that, this scheme determines the effective sealing section in the data extraction path, extracts the length and contact stress of each effective sealing section, and then calculates the sealing performance parameters, and evaluates the sealing performance of the rotary blowout preventer rubber core through the sealing performance parameters.

[0047] Furthermore, the sealing performance parameter is calculated by the following formula:

[0048] ;

[0049] Where: K is the sealing performance parameter; i Representative i An effective sealing section; a i , b i Respectively i The starting point and end point of an effective sealing section; σ ci For the i Contact stress of an effective sealing section; l i For the i The length of the effective sealing section.

[0050] This scheme is based on sealing performance parameters K The quantitative analysis of the sealing performance of the rubber core is carried out to fill the gap in the quantitative evaluation of the working performance of the rubber core of the rotary blowout preventer in the existing technology. K The larger the value, the better the sealing performance of the rubber core.

[0051] Furthermore, the required sealing pressure is the wellhead pressure. When the rotary blowout preventer is closed, the wellhead pressure also helps seal the blowout preventer rubber core. Therefore, using the wellhead pressure set in the simulation as the required sealing pressure is conducive to ensuring the theoretical consistency of the calculation process.

[0052] Furthermore, the effective sealing section is determined by the following method:

[0053] S6021. Obtain contact stress distribution data on the data extraction path based on simulation;

[0054] S6022, taking the wellhead pressure as a contact stress threshold, extracting a node interval where the contact stress is greater than the contact stress threshold;

[0055] S6023. Use the continuous node interval as the effective sealing section.

[0056] There may be several node intervals. In this solution, a continuous node interval can be used as an effective sealing section. The contact stress threshold can be adaptively set according to the actual working conditions, preferably the wellhead pressure value.

[0057] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0058] 1. A method for evaluating the working performance of a rubber core of a rotary blowout preventer of the present invention introduces a damage function based on the Mullins effect, and obtains a strain energy function of the rubber core material to be solved. The strain energy function is solved by combining a tensile test, and material parameters that take the Mullins effect into consideration can be obtained. Finite element simulation is then performed based on the obtained material parameters, and the sealing performance of the rubber core is evaluated based on the simulation results.

[0059] 2. The present invention provides a method for evaluating the working performance of a rotary blowout preventer rubber core. The entire evaluation process fully considers the influence of the Mullins effect on the sealing performance of the rotary blowout preventer rubber core, overcomes the shortcomings of the prior art, and provides a more scientific and accurate method for the safety evaluation of the rotary blowout preventer, which is beneficial to improving the operating safety of offshore drilling platforms and reducing safety hazards.

[0060] 3. A method for evaluating the working performance of a rotary blowout preventer rubber core of the present invention obtains cyclic stress-strain data under multiple tensile amplitudes, i.e., actual stress-strain curves, by subjecting multiple specimens to five different but fixed periodic tensile loads. This is conducive to more accurate fitting of the second strain energy function to obtain more accurate material parameters that take into account the Mullins effect.

[0061] 4. The present invention provides a method for evaluating the working performance of a rotary blowout preventer rubber core, using sealing performance parameters K The quantitative analysis of the sealing performance of the rubber core is carried out to fill the gap in the existing technology in the quantitative evaluation of the working performance of the rubber core of the rotary blowout preventer. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0063] Figure 1 It is a schematic diagram of a flow chart of a specific embodiment of the present invention;

[0064] Figure 2 It is an actual stress-strain curve diagram in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0066] Example 1

[0067] A method for evaluating the working performance of a rotary blowout preventer rubber core, such as Figure 1 As shown, the following steps are included:

[0068] Step 1: Establish the strain energy function of the rubber core material, which is defined as the first strain energy function:

[0069] ;

[0070] Where: is the strain energy density on the main loading path; k , j To control the power exponents of different terms in the formula, the order of polynomial expansion of strain invariants is expressed; N is the order; C kj is the material parameter of the deviatoric part; is the partial first strain invariant; is the partial second strain invariant; J el is the elastic volume ratio of the material; D k is a parameter related to volume response.

[0071] The first strain energy function in this embodiment can be used to simulate the typical S-shaped stress-strain curve of the rubber core material, can predict the mechanical behavior under different deformation modes, and is suitable for simulating the superelastic properties of the rubber core under large deformation.

[0072] Step 2: Establish a damage function of the rubber core material based on the Mullins effect, introduce the damage function of the rubber core material based on the Mullins effect into the first strain energy function, and obtain a strain energy function considering the Mullins effect, which is defined as the second strain energy function.

[0073] Among them, the damage function of the rubber core material based on the Mullins effect is:

[0074] ;

[0075] Where: η is the damage variable; r , m and β All are material parameters; erf represents the Gaussian error function; U m is the maximum strain energy density during material loading.

[0076] Step 3: Prepare a sample with the rubber core material, perform a tensile test, and obtain the actual stress-strain curve.

[0077] S301, preparing three dumbbell-shaped specimens; setting the initial stretching ratio to 0.5;

[0078] S302, performing four loading-unloading cycles on the dumbbell-shaped specimen;

[0079] S303, increase the stretching ratio by 0.5, and return to step S302 until four loading-unloading cycles with a maximum stretching ratio of 2.5 are completed, and the actual stress-strain curve is obtained as shown in Figure 2 shown in Figure 2 In the equation, λ represents the stretching ratio.

[0080] Step 4: Fitting the second strain energy function based on the actual stress-strain curve to obtain material parameters of the rubber core material.

[0081] In this embodiment, the data in the actual stress-strain curve is fitted with the second strain energy function, iterated, and the model parameters are optimized to obtain material parameters. After these parameters are determined, they can be used to simulate the softening effect of the rubber core material under different stress states.

[0082] Step 5: Establish a finite element model based on the material parameters of the rubber core material.

[0083] S501, respectively establishing geometric models of a rubber core, an iron frame and a drill rod, wherein the drill rod includes a drill rod coupling;

[0084] S502, assemble the iron frame on the outside of the rubber core, and allow the drill rod to pass through the rubber core;

[0085] S503, assigning material parameters of the rubber core material to the rubber core, and setting boundary conditions, including:

[0086] Apply rigid body constraints to the drill rod and iron frame;

[0087] Set the contact between the rubber core and the drill pipe to limited slip; set the tangential contact friction model between the rubber core and the drill pipe to "penalty contact";

[0088] A fixed constraint is applied to the bolt hole area of ​​the rubber core, and wellhead pressure is applied to the outside of the rubber core.

[0089] Step 6: Simulation, evaluate the working performance of the rubber core based on the simulation results. Specifically:

[0090] S601, applying up and down reciprocating motion to the drill pipe, so that the drill pipe coupling passes through the rubber core during each upward and downward movement;

[0091] S602, taking the area from the top of the sealing surface between the rubber core and the drill pipe to the bottom of the rubber core as the data extraction path, determining the effective sealing section that reaches the required sealing pressure, and extracting the length and contact stress of each effective sealing section;

[0092] In this embodiment, the required sealing pressure is the wellhead pressure;

[0093] In this embodiment, the effective sealing section is determined by the following method: based on simulation, the contact stress distribution data on the data extraction path is obtained; the wellhead pressure is used as the contact stress threshold, and the node interval with contact stress greater than the contact stress threshold is extracted; and the continuous node interval is used as the effective sealing section.

[0094] S603, based on the contact length and contact stress of each effective sealing section, calculate the sealing performance parameters and evaluate the working performance. The sealing performance parameters are calculated by the following formula:

[0095] ;

[0096] Where: K is the sealing performance parameter; i Representative i An effective sealing section; a i , b i Respectively i The starting point and end point of an effective sealing section; σ ci For the i Contact stress of an effective sealing section; l i For the i The length of the effective sealing section.

[0097] The applicant adopted the evaluation method in this embodiment and compared it with the actual failure cases of the rubber core fed back from the field. The results showed that the parts greatly affected by the Mullins effect obtained by the simulation analysis in this embodiment were highly consistent with the failure cases, verifying the accuracy of this method.

[0098] Example 2

[0099] A method for evaluating the working performance of a rotary blowout preventer rubber core, based on Example 1, in the process of fitting a second strain energy function based on an actual stress-strain curve:

[0100] In this embodiment, the curve during the loading process is used as the main curve, and the curve during the unloading process is used as the secondary curve. During the fitting process, the main curve is calibrated first, and then the unloading curve is calibrated.

[0101] The master curve is fitted using the least squares method, the corresponding stress-strain relationship is derived according to the second strain energy function, and the material parameters can be obtained by fitting using the least squares optimization algorithm.

[0102] On this basis, the stress-strain relationship of the entire strain energy model can be derived according to the rubber constitutive theory, and then the master curve can be used to calibrate the unloading curve. That is, the calibrated master curve material parameters are substituted into the following formula, and then the least squares method is used to calibrate the remaining material parameters:

[0103] ;

[0104] Where: is the deviatoric stress corresponding to the main loading path under the current deviatoric deformation level; is the stretching ratio corresponding to the main loading path; is the corresponding deviator stress on the main loading path; is the hydrostatic pressure corresponding to the main loading path; I is the unit tensor.

[0105] Example 3

[0106] A device for evaluating the working performance of a rotary blowout preventer rubber core comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method steps described in Embodiment 1 or 2 are implemented.

[0107] Example 4

[0108] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method steps described in Example 1 or 2 are implemented.

[0109] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0110] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A method for evaluating the working performance of a rotary blowout preventer rubber core, characterized in that: The following steps are involved: S1. Establish the strain energy function of the rubber core material, which is defined as the first strain energy function; S2, establishing a damage function of the rubber core material based on the Mullins effect, introducing the damage function of the rubber core material based on the Mullins effect into the first strain energy function, and obtaining a strain energy function considering the Mullins effect, which is defined as a second strain energy function; S3, prepare the sample with the rubber core material, do the tensile test, and obtain the actual stress-strain curve; S4, fitting the second strain energy function based on the actual stress-strain curve to obtain material parameters of the rubber core material; S5. Establish a finite element model based on the material parameters of the rubber core material; S6. Simulation, evaluating the working performance of the rubber core based on the simulation results.

2. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 1, characterized in that: The first strain energy function is: ； Where: is the strain energy density on the main loading path; k , j To control the power exponents of different terms in the formula, the order of polynomial expansion of strain invariants is expressed; N is the order; C kj is the material parameter of the deviatoric part; is the partial first strain invariant; is the partial second strain invariant; J el is the elastic volume ratio of the material; D k is the volume response related parameter.

3. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 1, characterized in that: The damage function of the rubber core material based on the Mullins effect is: ； Where: η is the damage variable; r , m and β All are material parameters; erf represents the Gaussian error function; U m is the maximum strain energy density during material loading; is the strain energy density on the main loading path.

4. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 1, characterized in that: Step S3 specifically includes: S301, preparing at least three dumbbell-shaped specimens; setting the initial stretching ratio to 0.5; S302, performing four loading-unloading cycles on the dumbbell-shaped specimen; S303, increase the stretching ratio by 0.5, and return to step S302, until four loading-unloading cycles with a stretching ratio of 2.5 are completed to obtain an actual stress-strain curve.

5. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 1, characterized in that: The finite element model establishment comprises: S501, respectively establishing geometric models of a rubber core, an iron frame and a drill rod, wherein the drill rod includes a drill rod coupling; S502, assemble the iron frame on the outside of the rubber core, and allow the drill rod to pass through the rubber core; S503, assigning material parameters of the rubber core material to the rubber core, and setting boundary conditions.

6. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 5, characterized in that: The boundary conditions include: Apply rigid body constraints to the drill rod and iron frame; Set the contact between the rubber core and the drill pipe to limited slip; set the tangential contact friction model between the rubber core and the drill pipe to "penalty contact"; A fixed constraint is applied to the bolt hole area of ​​the rubber core, and wellhead pressure is applied to the outside of the rubber core.

7. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 5, characterized in that: Step S6 specifically includes: S601, applying up and down reciprocating motion to the drill pipe, so that the drill pipe coupling passes through the rubber core during each upward and downward movement; S602, taking the area from the top of the sealing surface between the rubber core and the drill pipe to the bottom of the rubber core as the data extraction path, determining the effective sealing section that reaches the required sealing pressure, and extracting the length and contact stress of each effective sealing section; S603. Based on the contact length and contact stress of each effective sealing section, the sealing performance parameters are calculated to evaluate the working performance.

8. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 7, characterized in that: The sealing performance parameters are calculated by the following formula: ； Where: K is the sealing performance parameter; i Representative i An effective sealing section; a i , b i Respectively i The starting point and end point of an effective sealing section; σ ci For the i Contact stress of an effective sealing section; l i For the i The length of the effective sealing section.

9. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 7, characterized in that: The required sealing pressure is the wellhead pressure.

10. A method for evaluating the working performance of a rotary blowout preventer rubber core according to claim 7, characterized in that: The effective sealing section is determined by the following method: S6021. Obtain contact stress distribution data on the data extraction path based on simulation; S6022, taking the wellhead pressure as a contact stress threshold, extracting a node interval where the contact stress is greater than the contact stress threshold; S6023. Use the continuous node interval as the effective sealing section.

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