A method for evaluating the stability of a self-elevating platform pile foundation

Abstract

This invention provides a method for evaluating the stability of pile foundations for jack-up platforms, belonging to the technical field of pile driving operations for jack-up platforms in offshore oilfields. The method includes the following steps: Step 1, collection of pile foundation data; Step 2, selection of pile driving algorithm based on geological formation adaptability; Step 3, analysis of pile driving prediction curves; Step 4, recommendation of algorithms; Step 5, analysis of pile driving soil squeezing effect; Step 6, analysis of complex situations involving pile driving slippage; Step 7, analysis of soil parameter tables, pile driving depth curves, and relative puncture safety factors to determine pile driving puncture and conduct risk analysis; Step 8, determination of ballast methods suitable for on-site pile driving operations on jack-up platforms based on the pile driving curves and risk analysis; Step 9, compilation of a pile foundation stability evaluation report. This invention contributes to the safety of pile driving operations during the positioning of jack-up platforms in offshore oilfields, ensuring the safety of pile driving for jack-up platforms and the safety of large offshore facilities, enabling safe and efficient offshore positioning operations.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of offshore oilfield self-elevating platform pile insertion operation, in particular to a self-elevating platform pile insertion foundation stability evaluation method. BACKGROUND

[0002] The self-elevating platform is the most important mobile drilling device for offshore oilfield development, which has 3 or 4 pile legs, and the bottom of the pile leg has various styles of pile shoes. The self-elevating platform is fixed at a certain well site or connected with fixed facilities to realize drilling and well repair operations, etc. During pile insertion, the pile shoe penetrates a certain depth below the sea bottom mud surface and is seated on the seabed foundation, so as to resist the complex environment and risks of wind, wave and current on the sea during operation.

[0003] The stability of the pile insertion foundation of the self-elevating platform has always been an important problem in offshore oil development. In May 2021, a self-elevating platform in Malaysia pierced the bow pile when ballasting, and finally capsized, and all personnel were rescued. In July, a self-elevating platform in China tilted when the pile leg penetrated the stratum during wind power installation operation, causing the ship body to tilt, and 4 people were missing. Therefore, the stability and safety of the pile insertion foundation of the self-elevating platform is not only the premise of operation, but also the guarantee of the safety of large facilities and personnel.

[0004] The existing technology is to calculate the pile insertion according to the international general standard algorithm, but there are some defects, which do not consider the side friction of the pile shoe, the influence of backfilling soil and the group pile effect, so that the calculation of the pile insertion foundation stability is biased, and sometimes the deviation can reach more than 3 meters. The risk of pile insertion sliding and piercing is not estimated enough, which causes the pile insertion time to exceed the planned time by more than one time, and also causes property loss and even personnel casualties. SUMMARY

[0005] Therefore, the present application aims to provide a self-elevating platform pile insertion foundation stability evaluation method, which is helpful for the foundation stability of the offshore oilfield self-elevating platform during pile insertion at well sites and sites. Through pile insertion foundation stability evaluation, risks are found and avoided, the accuracy of pile insertion prediction and the safety of on-site pile insertion are improved, the safety of large facilities is ensured, and the development operation process is promoted.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows: a self-elevating platform pile insertion foundation stability evaluation method, comprising the following steps:

[0007] Step 1, pile insertion foundation data collection, including self-elevating platform operation water depth, ship body weight, pile shoe information, historical old footprint information, and single pile maximum preloading;

[0008] Step two, the stratum adaptability selection of the pile insertion algorithm, the pile insertion depth calculation is carried out by using different algorithms, and the penetration depth curve based on different algorithms is obtained;

[0009] Step three, pile insertion prediction curve analysis, analyze the characteristics of the penetration curve of different ballast load points;

[0010] Step four, recommended algorithm, the best algorithm for the pile insertion of the jack-up platform is obtained according to the adaptability of different algorithms and the analysis of the penetration curve;

[0011] Step five, pile insertion soil squeezing effect analysis, the reaction force evaluation of the soil squeezing effect of the pile insertion on the jacket pile leg;

[0012] Step six, pile insertion slip complex situation analysis, the qualitative analysis of the slip trend and slip direction and the slip risk analysis are carried out by analyzing the slip factors, the new and old footprint overlapping area, the slip horizontal force distribution and the slip trend prediction;

[0013] Step seven, analyze the soil parameter table, the pile insertion depth curve and the relative penetration safety factor, and carry out the pile insertion penetration judgment and risk analysis;

[0014] Step eight, according to the pile insertion curve and risk analysis, determine the ballast mode that meets the pile insertion operation of the jack-up platform on site;

[0015] Step nine, according to steps one to eight, write the pile insertion foundation stability evaluation report.

[0016] Further, the water depth of the jack-up platform in step one is between the minimum draft depth of the jack-up platform and the maximum operation water depth, and the maximum operation water depth is determined by the total length of the pile leg, the pile insertion depth and the production air gap.

[0017] Further, the step two is specifically: (21) the pile insertion algorithm includes API algorithm and CPU algorithm; (22) the pile insertion penetration depth curve is an irregular curve with the limit pile shoe load as the horizontal axis and the pile foot tip penetration depth below the sea bottom mud surface as the vertical axis;

[0018] The step three is specifically: different ballast load points include the load generated by the ship body itself when the ship body of the jack-up platform is away from the sea level, the load corresponding to the penetration point when there is penetration, and the maximum pre-ballast load of a single pile.

[0019] Further, the API algorithm adaptability includes the pile end resistance of the shoe pile; the CPU algorithm adaptability includes not only the pile end resistance of the shoe pile, but also the lateral friction, the backfill percentage and the group pile effect.

[0020] Further, the reaction force evaluation of the step five is to determine whether the influence between the pile shoe and the jacket pile shoe meets the safety requirement according to the distance between the pile shoe of the self-elevating platform and the jacket pile leg, and the safety distance is 1 / 3-1 / 2 of the diameter of the pile shoe.

[0021] Further, the slip factor in the step six includes the insertion depth calculation value of the self-elevating platform into the mud, the historical old footprint depth value, the new and old footprint overlapping area, the diameter of the pile shoe of the self-elevating platform, the slip horizontal force direction and the just-in-place scheme.

[0022] The step seven is specifically:

[0023] (71) The relative puncture safety factor general judgment standard is the ratio of the maximum bearing capacity calculated in the hard soil layer or the minimum bearing capacity calculated in the soft underlayer to the maximum pile leg load expected;

[0024] (72) Whether the puncture occurs or not is determined according to the relative puncture safety factor, when the safety factor is greater than or equal to 1.5, it is considered that the puncture definitely will not occur, and the drilling ship can be inserted; when the safety factor is greater than or equal to 1.2 and less than 1.5, it is considered that the self-elevating platform can be inserted; when the safety factor is less than 1.2, it is considered that there is a possibility of puncture, and the self-elevating platform is not suitable for insertion.

[0025] Further, the ballast mode in the step eight includes the normal air gap ballast, the zero air gap ballast and the floating ballast.

[0026] Further, in the step two, the soil parameters of different algorithms are based on the same drilling soil data at the same drilling position, the same soil parameters are formed, and the basis data of the penetration depth curve is the formation soil parameter, the maximum pre-ballast load of the single pile of the planned self-elevating platform and the pile shoe geometric parameter.

[0027] Further, the slip and puncture insertion complex situation analysis needs to refer to the soil conditions of other well sites or sites in the same block and the insertion situation of the self-elevating platform in the same block for comprehensive analysis and evaluation.

[0028] Further, if the self-elevating platform insertion foundation is located in the shallow gas range, it is necessary to move out of the shallow gas and carry out drilling soil sampling operation at a new position, and repeat the steps one to nine to evaluate the stability of the insertion foundation.

[0029] Compared with the prior art, the self-elevating platform insertion foundation stability evaluation method has the following advantages:

[0030] (1) The present application fully considers the influence of the old footprint, the lateral friction force and the group pile, so that the insertion foundation evaluation is more comprehensive and accurate;

[0031] (2) The pile driving algorithm is more compatible with the self-elevating platform and soil characteristics, which improves the accuracy of pile driving prediction;

[0032] (3) On-site pile driving and ballast risk assessment make the pile driving operation of the self-elevating platform safer, ensuring the safety of positioning and the safety of large facilities. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0034] Figure 1 This is a flowchart illustrating the steps of the method described in an embodiment of the present invention;

[0035] Figure 2 This is a diagram illustrating the placement scheme according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of a pile boot;

[0037] Figure 4 For the API algorithm's mud penetration depth curve;

[0038] Figure 5 This is the mud penetration depth curve for the CPU algorithm.

[0039] Explanation of the attached diagram labels: 1. First old footprint; 2. Pile boot; 3. Second old footprint; 4. Submarine cable. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] like Figure 1 This invention provides a method for evaluating the stability of a self-elevating platform pile foundation, comprising the following steps:

[0043] Step 1: Collection of foundation data for pile driving. The foundation data for pile driving includes the operating water depth of the jack-up platform, the weight of the hull, information on pile shoe 2, historical footprint information, and the maximum preload of a single pile. Among them, the operating water depth of the jack-up platform is between the minimum draft and the maximum operating water depth of the jack-up platform. The maximum operating water depth is determined by the total length of the pile legs, the pile driving depth, and the production air gap.

[0044] Step two, stratum adaptability selection of the insertion algorithm, different algorithms are used to calculate the penetration depth, and the penetration depth curves based on two different algorithms are obtained respectively; specifically, the insertion algorithm includes API algorithm and CPU algorithm, both of which are existing bases; the penetration depth curve of the inserted pile is an irregular curve with the limit pile shoe 2 load as the horizontal axis and the pile toe penetration depth below the seabed soil surface as the vertical axis; the soil parameters of different algorithms are based on the same drilling soil data at the same drilling location, forming the same soil parameters, and the basic data of the penetration depth curve is the soil parameters, the planned maximum pre-load of the single pile of the self-elevating platform, and the geometric parameters of the pile shoe 2.

[0045] Step three, analysis of the insertion prediction curve, the characteristics of the penetration curve at different ballast load points are analyzed; wherein the different ballast load points include the load generated by the ship body itself when the ship body is out of the sea level, that is, the load generated by the ship body itself when the buoyancy of the sea water on the ship body is zero, the load corresponding to the puncture point when there is puncture, and the maximum pre-load of the single pile. It should be noted that, whether it is API algorithm or CPU algorithm, when performing insertion prediction curve analysis, according to the industry report rules, when the safety factor is greater than 1.5, there is no puncture risk, so the safety factor is not marked on the report; when the safety factor is less than 1.5, the safety factor will be marked, that is, the safety factor is the data written on the report, only less than 1.5 will mark the puncture safety factor in the curve graph, when the safety factor is greater than 1.5, the safety factor will not be marked in the curve graph.

[0046] The analysis of the complex situation of sliding and puncture insertion needs to refer to the soil conditions of other well sites or sites in the same block and the insertion situation of similar self-elevating platforms in the block for comprehensive analysis and evaluation.

[0047] Step four, recommended algorithm, the best algorithm that meets the insertion of the self-elevating platform in a certain block is obtained according to the adaptability of different algorithms and the analysis of the penetration curve; wherein the API algorithm adaptability includes the pile end resistance of the shoe pile; the CPU algorithm adaptability not only includes the pile end resistance of the shoe pile, but also includes the lateral friction, the backfill percentage and the group pile effect, so the CPU algorithm is more comprehensive than the API algorithm.

[0048] Step five, analysis of the soil squeezing effect of insertion, the reaction force evaluation of the soil squeezing effect of the insertion on the jacket pile leg; wherein the reaction force evaluation of the soil squeezing effect is to determine whether the influence between the pile shoe 2 and the jacket pile leg meets the safety requirements according to the distance between the self-elevating platform pile shoe 2 and the jacket pile leg, and the safety distance is 1 / 3-1 / 2 of the diameter of the pile shoe 2. According to the insertion and positioning scheme of the self-elevating platform, the distance between the self-elevating platform pile shoe 2 and the jacket pile leg can be obtained, then since the diameter of the pile shoe 2 is a known parameter, the safety distance can be calculated, and then whether it meets the safety requirements is judged according to the safety distance.

[0049] Step six, analysis of complex conditions of pile insertion and sliding, qualitative analysis of sliding trend and direction and sliding risk analysis are performed by analyzing sliding factors, including calculation value of pile insertion depth of the self-elevating platform, historical old footprint depth value, overlapping area of new and old footprints, diameter of the pile shoe of the self-elevating platform, sliding horizontal force direction and positioning scheme; the positioning scheme of the self-elevating platform refers to the design scheme of the pile insertion position of the self-elevating platform according to the technical requirements of the ship heading, longitudinal deviation and lateral deviation, and the production platform (including wellhead), subsea pipeline and cable, first old footprint and second old footprint are parameters in the positioning scheme.

[0050] Step seven, analysis of soil parameter table, pile insertion depth curve and relative puncture safety factor to determine whether the pile insertion puncture occurs and risk analysis; step seven is specifically as follows:

[0051] (71) the general judgment standard of the relative puncture safety factor is the ratio of the maximum bearing capacity calculated in the hard soil layer or the minimum bearing capacity calculated in the soft underlayer to the maximum pile leg load expected;

[0052] (72) whether the puncture occurs is determined according to the relative puncture safety factor, when the safety factor is greater than or equal to 1.5, it is considered that the puncture will not occur, and the drilling ship can be inserted; when the safety factor is greater than or equal to 1.2 and less than 1.5, it is considered that the self-elevating platform is suitable for pile insertion; when the safety factor is less than 1.2, it is considered that there is a possibility of puncture, and the self-elevating platform is not suitable for pile insertion.

[0053] Step eight, according to the pile insertion curve and risk analysis, the ballast mode suitable for the self-elevating platform site pile insertion operation is determined; wherein the ballast mode includes normal air gap ballast, zero air gap ballast and floating ballast.

[0054] Step nine, according to steps one to eight, a pile foundation stability evaluation report is prepared.

[0055] If the pile foundation of the self-elevating platform is located within the shallow gas range, it is necessary to move out of the shallow gas and perform drilling soil sampling operation at a new position, and steps one to nine are repeated to evaluate the stability of the pile foundation.

[0056] The following is a specific embodiment of a certain self-elevating platform, site QK platform, which further illustrates a self-elevating platform pile foundation stability evaluation method of the application, which includes the following steps:

[0057] (1) a certain self-elevating platform, site QK platform: pile foundation data collection, specific data are shown in table 1, table 2 and table 3.

[0058] Table 1 Foundation information

[0059]

[0060] Table 2 Historical old footprint data table

[0061]

[0062] Table 3 Soil parameters table

[0063]

[0064] (2) The stratum adaptability selection of the pile insertion algorithm, the different algorithms are used to calculate the penetration depth, and the penetration depth curves based on two different algorithms are obtained respectively.

[0065] Figure 4 The API algorithm penetration depth curve is shown in the figure. From the curve, the depth values corresponding to different loads, the depth value at the maximum pre-pressing load, and the risk of sudden penetration can be seen.

[0066] Figure 5 The CPU algorithm penetration depth curve is shown in the figure. From the curve, the depth values corresponding to different loads, the depth value at the maximum pre-pressing load, and the risk of sudden penetration can be seen.

[0067] (3) Pile insertion prediction curve analysis, analyze the characteristics of the penetration curve of different pre-pressing load points.

[0068] As shown in Figure 4 , the pre-pressing load is increased by a little weight, and the penetration depth is increased with the increase of the pile foot load. In theory, the load is increased, and the penetration depth should be completely consistent with the curve. The maximum pre-pressing load is 34.5MN (3520 tons), and the corresponding depth value is 10.9 meters; as shown in Figure 5 , the depth value corresponding to the maximum pre-pressing load is 8.9 meters. Since Figure 4 and Figure 5 do not mark the safety factor, it can be known that the safety factor is greater than 1.5, and both algorithms show that there is no puncture risk in the site.

[0069] (4) According to the adaptability of different algorithms and the analysis of the penetration curve, the best algorithm for the pile insertion of the self-elevating platform in a certain block is obtained.

[0070] Figure 3As shown in Fig. 2, a schematic diagram of the pile shoe 2 is shown. In this embodiment, the equivalent diameter d2 of the pile shoe 2 is 9.2 meters, the height a from the toe of the pile shoe 2 to the maximum cross-sectional height is 0.5 meters, and the side height b is 0.65 meters. Thus, the effective area of the pile shoe 2 can be calculated as 70.1 square meters. The lateral friction contact area is 0.65 x π x 9.2 = 18.78 square meters. The forces that exist under normal circumstances include the lateral friction of the pile shoe 2, the force generated by the backfill, and the pile exclusion force of the pile group effect of the pile shoe 2 and the jacket leg. In this embodiment, the lateral friction contact area is much smaller than the effective area of the pile shoe 2, so the main determining factors are the backfill percentage and the pile group effect of the pile shoe 2 and the jacket leg. Since the API algorithm adaptability includes the pile end resistance of the pile shoe, the CPU algorithm adaptability includes not only the pile end resistance of the pile shoe, but also the lateral friction, the backfill percentage, and the pile group effect. Therefore, in this embodiment, the CPU algorithm is closer to the actual situation.

[0071] (5) Analysis of the pile insertion and soil extrusion effect.

[0072] As shown in Fig. 2, a schematic diagram of the pile shoe 2 is shown. In this embodiment, the equivalent diameter d2 of the pile shoe 2 is 9.2 meters, the height a from the toe of the pile shoe 2 to the maximum cross-sectional height is 0.5 meters, and the side height b is 0.65 meters. Thus, the effective area of the pile shoe 2 can be calculated as 70.1 square meters. The lateral friction contact area is 0.65 x π x 9.2 = 18.78 square meters. The forces that exist under normal circumstances include the lateral friction of the pile shoe 2, the force generated by the backfill, and the pile exclusion force of the pile group effect of the pile shoe 2 and the jacket leg. In this embodiment, the lateral friction contact area is much smaller than the effective area of the pile shoe 2, so the main determining factors are the backfill percentage and the pile group effect of the pile shoe 2 and the jacket leg. Since the API algorithm adaptability includes the pile end resistance of the pile shoe, the CPU algorithm adaptability includes not only the pile end resistance of the pile shoe, but also the lateral friction, the backfill percentage, and the pile group effect. Therefore, in this embodiment, the CPU algorithm is closer to the actual situation.

[0073] (6) Analysis of the pile insertion and soil extrusion effect.

[0074] As shown in Fig. 2, a schematic diagram of the pile shoe 2 is shown. In this embodiment, the equivalent diameter d2 of the pile shoe 2 is 9.2 meters, the height a from the toe of the pile shoe 2 to the maximum cross-sectional height is 0.5 meters, and the side height b is 0.65 meters. Thus, the effective area of the pile shoe 2 can be calculated as 70.1 square meters. The lateral friction contact area is 0.65 x π x 9.2 = 18.78 square meters. The forces that exist under normal circumstances include the lateral friction of the pile shoe 2, the force generated by the backfill, and the pile exclusion force of the pile group effect of the pile shoe 2 and the jacket leg. In this embodiment, the lateral friction contact area is much smaller than the effective area of the pile shoe 2, so the main determining factors are the backfill percentage and the pile group effect of the pile shoe 2 and the jacket leg. Since the API algorithm adaptability includes the pile end resistance of the pile shoe, the CPU algorithm adaptability includes not only the pile end resistance of the pile shoe, but also the lateral friction, the backfill percentage, and the pile group effect. Therefore, in this embodiment, the CPU algorithm is closer to the actual situation. Figure 2

[0075] ​The pile shoe 2 at the bow position (bow pile) has a contact area of about 80% with the first old footprint 1 and a contact area of about 20% with the second old footprint 3, so the pile shoe 2 has a clear tendency to slide towards the first old footprint 1, and the first old footprint 1 has a large equivalent circle diameter, so it has the risk of sliding towards the bow pile; the depths of the first old footprint 1 and the second old footprint 3 are 8.5 meters and 8.3 meters respectively, and the depths of the two are almost the same, so the depth of the old footprint has the same effect, and the depths of the two are known parameters. Since the first old footprint 1 clearly slides towards the bow pile, the horizontal sliding force of the first old footprint 1 plays a major role, so the bow pile slides forward; the contact area of the pile shoes 2 of the two stern piles with the first old footprint 1 is about 15%, and the contact area with the second old footprint 3 is more than 70%, so the two stern piles have a clear tendency to slide towards the second old footprint 3. That is, through analysis, the bow pile slides forward, and the two stern piles slide backward. In the description of the present application, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features with "first", "second", etc. can be explicitly or implicitly included one or more of the features.

[0076] (7) Analyze the soil parameter table, pile driving depth curve, and relative penetration safety factor to determine whether pile penetration occurs and risk analysis. The relative penetration safety factor is on the pile penetration depth curve or the pile analysis report, and the penetration risk is determined according to the safety factor. As known from the above steps, the pile penetration curve of the self-elevating platform at the site has no penetration risk, so no penetration analysis is required.

[0077] (8) Determine the ballast mode that meets the self-elevating platform site pile driving operation according to the pile curve and risk analysis. Since the self-elevating platform in the embodiment has no penetration risk at the site, normal air gap ballast mode can be used for single pile step-by-step ballast, but the anti-sliding measure should be taken considering the sliding risk.

[0078] (9) According to steps (1) to (8), expand the data and analysis content, and write a QK platform pile foundation stability evaluation report for a certain self-elevating platform.

[0079] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method of evaluating the stability of a jack-up platform spudcan foundation, characterized by, The method comprises the following steps: Step one, collecting pile foundation data, including the working water depth of the jack-up platform, the hull weight, the pile shoe (2) information, the historical old footprint information, and the maximum pre-load of a single pile; Step two, selecting the stratum adaptability of the pile algorithm, using different algorithms to calculate the pile penetration depth, and obtaining the pile penetration depth curve based on different algorithms; Step two specifically includes: (21) the pile algorithm includes API algorithm and CPU algorithm; (22) the pile penetration depth curve is an irregular curve with the limit pile shoe (2) load as the horizontal axis and the pile foot tip penetration depth below the seabed soil surface as the vertical axis; wherein the API algorithm adaptability includes the pile end resistance of the shoe pile; the CPU algorithm adaptability includes not only the pile end resistance of the shoe pile, but also the lateral friction, the backfill percentage, and the pile group effect; Step three, analyzing the pile prediction curve, analyzing the characteristics of the penetration curve at different ballast load points; Step four, recommending an algorithm, obtaining the best algorithm for the jack-up platform pile according to the adaptability of different algorithms and the analysis of the penetration curve; Step five, analyzing the pile soil squeezing effect, evaluating the reaction force of the pile soil squeezing effect on the jacket pile leg; wherein the reaction force of the soil squeezing effect is evaluated according to the distance between the jack-up platform pile shoe (2) and the jacket pile leg to determine whether the influence between the pile shoe (2) and the jacket pile shoe (2) meets the safety requirements, and the safety distance is 1 / 3-1 / 2 of the diameter of the pile shoe (2); Step six, analyzing the complex situation of pile sliding, qualitatively analyzing the sliding trend and direction and analyzing the sliding risk by analyzing the sliding factors, the overlapping area of new and old footprints, the sliding horizontal force distribution, and the sliding trend prediction; Step seven, analyzing the soil parameter table, the pile penetration depth curve, and the relative penetration safety factor to determine the pile penetration and risk analysis; Step eight, determining the ballast mode that meets the jack-up platform site pile operation according to the pile curve and risk analysis; Step nine, compiling the pile foundation stability evaluation report according to steps one to eight.

2. The method for evaluating the stability of the pile driving foundation of the self-elevating platform according to claim 1, characterized in that: The working water depth of the jack-up platform in step one is between the minimum draft depth and the maximum working water depth of the jack-up platform, and the maximum working water depth is determined by the total length of the pile leg, the pile penetration depth, and the production air gap.

3. The method for evaluating the stability of the pile driving foundation of the self-elevating platform according to claim 1, characterized in that, Step three specifically includes: different ballast load points include the load generated by the hull weight of the jack-up platform when the hull is away from the sea level, the load corresponding to the penetration point when there is penetration, and the maximum pre-load of a single pile.

4. The jack-up platform pile foundation stability evaluation method according to claim 1, characterized in that: The sliding factors in step six include the jack-up platform pile penetration depth calculation value, the historical old footprint depth value, the overlapping area of new and old footprints, the diameter of the jack-up platform pile shoe (2), the sliding horizontal force direction, and the just-in-place scheme; Step seven specifically includes: (71) the general judgment standard of the relative penetration safety factor is the ratio of the maximum bearing capacity calculated in the hard soil layer or the minimum bearing capacity calculated in the soft underlayer to the maximum pile leg load. (72) The occurrence of puncture is determined according to the relative puncture safety factor. When the safety factor is greater than or equal to 1.5, it is considered that the puncture will not occur, and the drilling ship can be adapted to pile insertion; when the safety factor is greater than or equal to 1.2 and less than 1.5, it is considered that the jack-up platform is suitable for pile insertion; and when the safety factor is less than 1.2, it is considered that there is a possibility of puncture, and the jack-up platform is not suitable for pile insertion.

5. The method for evaluating the stability of the pile driving foundation of the self-elevating platform according to claim 1, characterized in that: The ballast mode in step eight includes normal air gap ballast, zero air gap ballast and floating ballast.

6. The method for evaluating the stability of the pile driving foundation of a self-elevating platform according to claim 3, characterized in that: In step two, the soil parameters of different algorithms are based on the same borehole soil data at the same borehole position, and the same soil parameters are formed. The basic data of the penetration depth curve is the formation soil parameter, the planned maximum pre-ballast load of the single pile of the jack-up platform and the geometric parameter of the pile shoe (2).

7. The method according to claim 4, wherein: The analysis of the complex situation of sliding and puncture pile insertion needs to refer to the soil conditions of other well sites or sites in the same block and the pile insertion situation of the same type of jack-up platform in the block for comprehensive analysis and evaluation.

8. The method for evaluating the stability of the pile-driving foundation of a self-elevating platform according to claim 1, characterized in that: If the jack-up platform pile foundation is located within the shallow gas range, it needs to be moved out of the shallow gas and the borehole soil sampling operation is carried out at the new position, and steps one to nine are repeated for pile foundation stability evaluation.

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