Reliability assessment method for topside modules of offshore oil and gas facilities under explosive loads

Abstract

This invention provides a reliability assessment method for the superstructure of offshore oil and gas facilities under explosive loads, comprising: S1, obtaining the maximum displacement of the members in the X direction, the maximum displacement of the members in the Y direction, and the maximum displacement of the members in the Z direction of the superstructure after an explosion; S2, obtaining the maximum displacement factor of the superstructure in each direction based on the dimensions of the superstructure before the explosion and the maximum displacement of the members after the explosion; S3, calculating the failure probability of the superstructure, comparing the failure probability with the failure threshold, and completing the reliability assessment of the superstructure under explosive loads. This method can not only simulate the explosion of the superstructure during the design phase to assess its reliability after the explosion, but also accurately assess the reliability of the existing superstructure after the explosion, providing a basis for determining whether the existing superstructure can continue to serve after the explosion.

Description

Technical Field

[0001] This invention belongs to the field of marine oil production equipment technology, specifically relating to a reliability assessment method for the top module of offshore oil and gas facilities under explosive loads. Background Technology

[0002] Offshore oil and gas production facilities are crucial engineering infrastructures for offshore oil and gas production, integrating functions such as oil and gas extraction, production, and transportation. Among these facilities, pressure vessels, oil and gas processing equipment, valves, and pipelines in the upper structure are frequently exposed to harsh marine environmental conditions, making them prone to oil and gas leaks and diffusion. Furthermore, the compact layout of these upper structures and poor air circulation further exacerbates the risk of explosions. An explosion can cause significant economic losses and casualties, as well as severe pollution and damage to the surrounding marine environment and ecosystem. Therefore, reliability analysis of the upper structure of offshore oil and gas facilities under explosive loads is of paramount importance.

[0003] Currently, the reliability assessment of the top module of offshore oil and gas facilities under explosive loads mainly involves conducting explosion dynamic response analysis on the finite element model of the top module. Based on the analysis results, the maximum stress value of the members in the top module and the fracture status of each key member are obtained. If the maximum stress value of the member exceeds the allowable stress value and at least one key member fractures, the top module of the offshore oil and gas facility is considered to have failed under explosive loads. In other words, this reliability assessment method is only applicable to the reliability assessment of the top module of offshore oil and gas facilities after explosion simulation in the design stage, and cannot accurately assess the reliability of the top module of existing offshore oil and gas facilities after an explosion. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide another reliability assessment method for the upper module of offshore oil and gas facilities under explosive load. This method calculates the failure probability of the upper module after the explosion by using the maximum offset factor of the upper module members in each direction before and after the explosion, thus filling the gap in accurately assessing the reliability of the upper module of existing offshore oil and gas facilities after an explosion.

[0005] To achieve the above and other related objectives, the present invention provides a reliability assessment method for the topside modules of offshore oil and gas facilities under explosive loads, the reliability assessment method comprising the following steps:

[0006] S1. Obtain the maximum displacement of the rods after the explosion of the upper module of the offshore oil and gas facility. The maximum displacement of the rods includes the maximum displacement of the rods in the X direction, the maximum displacement of the rods in the Y direction, and the maximum displacement of the rods in the Z direction.

[0007] S2. Based on the dimensions of the upper module of the offshore oil and gas facility before the explosion and the maximum offset of the rods after the explosion, obtain the maximum offset factor of the upper module of the offshore oil and gas facility in each direction.

[0008] S3. Calculate the failure probability of the topside module of the offshore oil and gas facility, compare the failure probability with the failure threshold, and complete the reliability assessment of the topside module of the offshore oil and gas facility under explosive load; the failure probability P f The calculation formula is:

[0009]

[0010] Among them, MDR X This is the maximum offset factor in the X direction;

[0011] MDR Y This is the maximum offset factor in the Y direction;

[0012] MDR Z The maximum offset factor in the Z direction;

[0013] A is the first environmental parameter, and its value is 180;

[0014] λ is the second environmental parameter, with a value of 0.202.

[0015] Preferably, the maximum displacement of the struts after the explosion of the upper module of the offshore oil and gas facility is either the actual maximum displacement of the struts or the theoretical maximum displacement of the struts; the actual maximum displacement of the struts is obtained by direct measurement; the steps for obtaining the theoretical maximum displacement of the struts include:

[0016] A finite element model of the upper module of an offshore oil and gas facility is established to determine the loading method of the explosive load; the loading method of the explosive load includes the loading position and direction of the explosive load, the loading time t of the explosive load, and the loading pressure P of the explosive load;

[0017] Based on static load, an explosion dynamics response analysis is performed to obtain a damage model of the upper module of the offshore oil and gas facility, and then the maximum displacement of the rods after the explosion of the upper module of the offshore oil and gas facility is obtained.

[0018] Preferably, the loading pressure P of the explosive load and the loading time t of the explosive load satisfy the following relationship:

[0019]

[0020] Where P0 is the maximum value of the explosive load;

[0021] t0 is the duration of the explosion load, 0.2s≤t0≤1s.

[0022] Preferably, the explosive load is applied at the following locations and in the following directions: inside the module along the Z direction, outside the module along the X direction, or outside the module along the Y direction.

[0023] As described above, the reliability assessment method for the top module of offshore oil and gas facilities under explosive loads of the present invention has the following beneficial effects:

[0024] This invention only requires obtaining the maximum offset of the rods in each direction after the explosion of the upper module, and calculating the maximum offset factor of the upper module in each direction, to calculate the failure probability of the upper module after the explosion. This can not only simulate the explosion of the upper module in the design stage to evaluate its reliability after the explosion, but also accurately evaluate the reliability of the existing upper module after the explosion, providing a basis for judging whether the existing upper module can continue to serve after the explosion, and avoiding unnecessary economic losses. Attached Figure Description

[0025] Figure 1 This is a flowchart of the reliability assessment method of the present invention.

[0026] Figure 2 This is a schematic diagram of an idealized triangular load application method. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0028] Please see Figures 1 to 2 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0029] like Figure 1 As shown, this invention provides a reliability assessment method for the topside modules of offshore oil and gas facilities under explosive loads: the method includes the following steps:

[0030] S1. Obtain the maximum displacement of the struts after the explosion of the upper module of the offshore oil and gas facility. The maximum displacement of the struts includes the maximum displacement L of the struts in the X direction. dX Maximum offset L of the member in the Y direction dY and the maximum offset L of the member in the Z direction dZ ;

[0031] S2. Based on the dimensions of the upper module of the offshore oil and gas facility before the explosion and the maximum offset of the rods after the explosion, obtain the maximum deviation rate (MDR) of the upper module of the offshore oil and gas facility in each direction.

[0032] Specifically, the maximum offset factor (MDR) of the topside module of an offshore oil and gas facility in the X direction. X The calculation formula is: MDR X =-L 0X / L dX (1); where L 0X The dimensions of the superstructure module of the offshore oil and gas facility in the X direction before the explosion;

[0033] Maximum offset factor (MDR) of the topside module of offshore oil and gas facilities in the Y direction Y The calculation formula is: MDR Y =-L 0Y / L dY (2); where L dY The dimensions of the superstructure module of the offshore oil and gas facility in the Y direction before the explosion;

[0034] Maximum offset factor (MDR) of the topside module of offshore oil and gas facilities in the Z direction Z The calculation formula is: MDR Z =-L 0Z / L dZ (3); where L dZ The dimensions of the superstructure module of the offshore oil and gas facility in the Z direction before the explosion;

[0035] S3. Calculate the failure probability of the top module of the offshore oil and gas facility. If the failure probability is less than the failure threshold, the top module of the offshore oil and gas facility is in a safe state after the explosion; otherwise, the top module of the offshore oil and gas facility is in a failed state after the explosion, thus completing the reliability assessment of the top module of the offshore oil and gas facility under the explosion load; the failure probability P... f The calculation formula is:

[0036]

[0037] Among them, MDR X This is the maximum offset factor in the X direction;

[0038] MDR Y This is the maximum offset factor in the Y direction;

[0039] MDR Z The maximum offset factor in the Z direction;

[0040] A is the first environmental parameter, and its value is 180;

[0041] λ is the second environmental parameter, with a value of 0.202.

[0042] It is understood that the failure threshold can be determined by the user, and in this embodiment, the failure threshold is preferably set to 3.0 × 10⁻⁶. -5 .

[0043] It is understandable that the maximum displacement of the struts after the explosion of the top module of the offshore oil and gas facility can be either the maximum displacement of the struts after the actual explosion of the top module of the offshore oil and gas facility (i.e., the actual maximum displacement of the struts) or the maximum displacement of the struts after the theoretical simulated explosion of the top module of the offshore oil and gas facility (i.e., the theoretical maximum displacement of the struts). There is no limitation on this, and the assessors can choose according to the state of the top module of the offshore oil and gas facility.

[0044] Specifically, the maximum displacement of the struts after the actual explosion of the upper module of an active offshore oil and gas facility can be directly measured.

[0045] Specifically, the steps for obtaining the maximum displacement of the struts after a theoretical simulation explosion of the upper module of an offshore oil and gas facility include:

[0046] S31. Establish a finite element model of the upper module of the offshore oil and gas facility in finite element software, and determine the loading method of the explosion load; the loading method of the explosion load includes the loading position and direction of the explosion pressure, the loading time t of the explosion pressure and the loading pressure P of the explosion pressure;

[0047] It is understandable that finite element modeling includes geometric modeling and feature modeling. Geometric modeling is based on geometric and topological information, such as the principal dimensions of the model, member types, and member lengths. Feature modeling is based on stiffness, mass, and / or damping.

[0048] Understandably, the method of applying explosive loads is determined by the explosion conditions, and there are three main common explosion conditions:

[0049] Explosion Scenario 1: Occurs outside the module along the X direction;

[0050] Explosion Scenario 2: Occurs outside the module along the Y direction;

[0051] Explosion Case 3: Occurs inside the module along the Z-axis;

[0052] The explosion pressure for each explosion condition is applied using an idealized triangular load, specifically as follows: Figure 2 As shown, P0 is the maximum value of the explosion pressure, and t0 is the duration of the explosion pressure. The explosion pressure P and the loading time t of the explosion pressure satisfy the following relationship:

[0053]

[0054] It is understandable that the duration t0 of the explosion pressure satisfies: 0.2s≤t0≤1s, and the specific values ​​can be found in Table 1.

[0055] Table 1: Values ​​for Explosion Duration

[0056] Module Categories Duration / s Fully enclosed partition 1 <![CDATA[Vibration chamber (space less than 1000 m 3 )]]> 0.2 Large or crowded operating areas 0.2 Operating areas smaller than 20m x 20m or not crowded 0.2 Open drilling platform 0.2

[0057] S32. Based on the actual conditions of the upper module on offshore oil and gas production facilities, boundary conditions are set. An explosion dynamic response analysis is performed considering static loads such as self-weight and equipment weight to obtain a damage model. Then, the maximum displacement L of the member in the X direction of the damage model is obtained. dX Maximum offset L of the member in the Y direction dY Maximum offset L of the member in the Z direction dZ .

[0058] The following are specific embodiments of the present invention:

[0059] Example 1

[0060] Based on the relevant parameters of the triethylene glycol dehydration module on the upper part of an offshore oil and gas production facility with main dimensions of 10m × 4m × 10.2m (i.e., X-axis dimension 10m, Y-axis dimension 4m, Z-axis dimension 10.2m), a corresponding finite element model was established in finite element software such as Abaqus or Ansys. Explosion dynamic response analyses (i.e., finite element analysis calculations) were performed under explosion conditions one (i.e., explosion pressure applied along the X-axis outside the module), explosion condition two (i.e., explosion pressure applied along the Y-axis outside the module), and explosion condition three (i.e., explosion pressure applied along the Z-axis inside the module). The peak explosion pressure P0 for each explosion condition was 2.0 bar, and the explosion pressure duration t0 was 0.2 s. Structural damage models were obtained for each explosion condition, and subsequently, the maximum displacement L of the module's members in the X-axis direction after the explosion was determined for each explosion condition. dX Maximum offset L of the member in the Y direction dY and the maximum offset L of the member in the Z direction dZ Meanwhile, based on the results of the explosion dynamic response analysis and calculation, the maximum stress value of the rods and the failure status of key rods under each explosion condition are obtained.

[0061] Then, using the reliability assessment method of the present invention, the maximum offset factor MDR of the module in the X direction after the explosion is calculated according to formulas (1) to (3) for each explosion condition. X Maximum offset factor (MDR) in the Y direction Y and the maximum offset factor MDR in the Z direction Z Then, the failure probability P of the module after the explosion is calculated using formula (4) under each explosion condition. f By comparing with the failure threshold of 3.0 × 10 -5 The reliability of the module after the explosion was compared to determine the reliability under each explosion condition; the specific calculation results are shown in Table 2.

[0062] Table 2. MDR values ​​and failure probabilities P of the triethylene glycol dehydration module under different explosion conditions. f and evaluation conclusions

[0063]

[0064] Based on the maximum stress and fracture conditions of key members in the traditional finite element analysis calculations, the reliability of the module after the explosion is evaluated under various explosion conditions. The evaluation results are shown in Table 3.

[0065] Table 3. Maximum stress values, fracture status of key components, and evaluation conclusions of the triethylene glycol dehydration module under different explosion conditions.

[0066] Explosion Case Categories Maximum stress value / MPa Key member status in conclusion Explosion Condition 1 450 No breakage reliable Explosion Condition Two ＞470 fracture Failure Explosion Condition 3 ＞470 No breakage reliable

[0067] As can be seen from Tables 2 and 3, the reliability assessment conclusions of the present invention are completely consistent with the traditional reliability assessment conclusions, effectively verifying the effectiveness of the reliability assessment method of the present invention.

[0068] Example 2

[0069] Based on the relevant parameters of a FPSO upper electrical room module (which is a two-story spatial steel frame) with main dimensions of 10m×6m×8m (i.e., X-axis dimension 10m, Y-axis dimension 6m, Z-axis dimension 8m), a corresponding finite element model was established in finite element software such as Abaqus or Ansys. Explosion dynamic response analysis (i.e., finite element analysis calculation) was performed under explosion conditions one (i.e., explosion pressure applied along the X-axis outside the module), explosion condition two (i.e., explosion pressure applied along the Y-axis outside the module), and explosion condition three (i.e., explosion pressure applied along the Z-axis inside the module). The peak explosion pressure P0 for each explosion condition was 0.6 bar, and the explosion pressure duration t0 was 0.3 s. The structural damage model under each explosion condition was obtained, and subsequently, the maximum displacement L of the module's members in the X-axis direction after the explosion was obtained for each explosion condition. dX Maximum offset L of the member in the Y direction dYand the maximum offset L of the member in the Z direction dZ Meanwhile, based on the results of the explosion dynamic response analysis and calculation, the maximum stress value of the rods and the failure status of key rods under each explosion condition are obtained.

[0070] Then, using the reliability assessment method of the present invention, the maximum offset factor MDR of the module in the X direction after the explosion is calculated according to formulas (1) to (3) for each explosion condition. X Maximum offset factor (MDR) in the Y direction Y and the maximum offset factor MDR in the Z direction Z Then, the failure probability P of the module after the explosion is calculated using formula (4) under each explosion condition. f By comparing with the failure threshold of 3.0 × 10 -5 The reliability of the module after the explosion was compared to determine the reliability under each explosion condition; the specific calculation results are shown in Table 4.

[0071] Table 4. MDR values ​​and failure probabilities P of FPSO electrical room modules under different explosion conditions. f and evaluation conclusions

[0072]

[0073] Based on the maximum stress and fracture conditions of key members calculated by traditional finite element analysis, the reliability of the module after the explosion was evaluated under various explosion conditions. The evaluation results are shown in Table 5.

[0074] Table 5. Maximum stress values, critical component fracture conditions, and assessment conclusions of the FPSO electrical room module under different explosion conditions.

[0075] Explosion Case Categories Maximum stress value / MPa Key member status in conclusion Explosion Condition 1 ＞470 fracture Failure Explosion Condition Two ＞470 fracture Failure Explosion Condition 3 420 No breakage reliable

[0076] As shown in Tables 4 and 5, the reliability assessment conclusions of this invention are completely consistent with those of traditional reliability assessment conclusions, effectively verifying the effectiveness of the reliability assessment method of this invention.

[0077] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for reliability assessment of the topside modules of offshore oil and gas facilities under explosive loads, characterized in that, This reliability assessment method includes the following steps: S1. Obtain the maximum displacement of the rods after the explosion of the upper module of the offshore oil and gas facility. The maximum displacement of the rods includes the maximum displacement of the rods in the X direction, the maximum displacement of the rods in the Y direction, and the maximum displacement of the rods in the Z direction. S2. Based on the dimensions of the upper module of the offshore oil and gas facility before the explosion and the maximum offset of the rods after the explosion, obtain the maximum offset factor of the upper module of the offshore oil and gas facility in each direction. Maximum offset factor of the topside module of offshore oil and gas facility in the X direction MDR X The calculation formula is: MDR X =− L 0X / L dX ;in, L 0X The dimensions of the superstructure module of the offshore oil and gas facility in the X direction before the explosion; L dX The maximum displacement of the rod in the X direction after the explosion of the upper module of the offshore oil and gas facility; Maximum offset factor of the topside module of offshore oil and gas facility in the Y direction MDR Y The calculation formula is: MDR Y =− L 0Y / L dY ;in, L 0Y The dimensions of the superstructure module of the offshore oil and gas facility in the Y direction before the explosion; L dY This represents the maximum displacement of the rod in the Y direction after the explosion of the upper module of the offshore oil and gas facility; Maximum offset factor of the topside module of offshore oil and gas facility in the Z direction MDR Z The calculation formula is: MDR Z =− L 0Z / L dZ ;in, L 0Z The dimensions of the superstructure module of the offshore oil and gas facility in the Z direction before the explosion; L dZ This represents the maximum displacement of the rod in the Z direction after the explosion of the upper module of the offshore oil and gas facility. S3. Calculate the failure probability of the top module of the offshore oil and gas facility, and compare the failure probability with the failure threshold. If the failure probability is less than the failure threshold, the top module of the offshore oil and gas facility is in a safe state after the explosion; otherwise, the top module of the offshore oil and gas facility is in a failed state after the explosion. This completes the reliability assessment of the top module of the offshore oil and gas facility under the explosion load. The failure probability... P f The calculation formula is: ； in, MDR X This is the maximum offset factor in the X direction; MDR Y This is the maximum offset factor in the Y direction; MDR Z The maximum offset factor in the Z direction; A This is the first environmental parameter, and its value is 180. This is the second environmental parameter, with a value of 0.

202.

2. The reliability assessment method for the topside module of an offshore oil and gas facility under explosive load as described in claim 1, characterized in that, The maximum displacement of the struts after the explosion of the upper module of the offshore oil and gas facility is either the actual maximum displacement of the struts or the theoretical maximum displacement of the struts. The actual maximum offset of the member is obtained by direct measurement; the steps for obtaining the theoretical maximum offset of the member include: Establish a finite element model of the upper module of offshore oil and gas facilities to determine the loading method of explosive loads; The method of applying the explosive load includes the application location and direction of the explosive pressure, and the application time of the explosive pressure. t With the magnitude of the explosion pressure P ; Based on static load, an explosion dynamics response analysis is performed to obtain a damage model of the upper module of the offshore oil and gas facility after the explosion, and then the maximum displacement of the rods after the explosion of the upper module of the offshore oil and gas facility is obtained.

3. The reliability assessment method for the top module of an offshore oil and gas facility under explosive load according to claim 2, characterized in that, The magnitude P of the explosion pressure and the loading time t of the explosion pressure satisfy the following relationship: ； in, P 0 represents the maximum explosion pressure; t 0 represents the duration of the explosion pressure, 0.2s ≤ t 0≤1s.

4. The reliability assessment method for the topside module of an offshore oil and gas facility under explosive load according to claim 2 or 3, characterized in that, The explosive pressure is applied at the following locations and in the following directions: inside the module along the Z direction, outside the module along the X direction, or outside the module along the Y direction.

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