Deep sea drilling machine bottoming process calculation method considering rheological sediment effect

Abstract

The invention provides a deep sea drilling machine bottoming process calculation method considering rheological sediment effect, which comprises the following steps of: dividing the whole bottoming process of a drilling machine into three stages of free falling, first bottoming of two groups of supporting legs and simultaneous bottoming of three groups of supporting legs, and establishing a coordinate transformation matrix between a world coordinate system and a drilling machine follow-up coordinate system, forming a multi-degree-of-freedom kinetic equation; seawater additional mass force, fluid Coriolis force, linear fluid damping force, sediment supporting force and sediment friction force are introduced into the multi-degree-of-freedom kinetic equation, and nonlinear environmental force changing along with speed, subsidence depth and time is obtained; taking a seabed slope angle, an initial pitch angle, a sediment rigidity coefficient and an internal friction angle as independent variables, performing iterative solution on the multi-degree-of-freedom kinetic equation by adopting a genetic algorithm, and outputting an extreme working condition parameter combination enabling a drilling machine to have a maximum acceleration extreme value, a maximum supporting force extreme value or a maximum sinking depth extreme value; accurate calculation and safety evaluation of the drilling machine bottoming dynamic behavior are achieved.

Description

Technical Field

[0001] This invention relates to the field of deep-sea resource exploration and development equipment technology, and more particularly to a calculation method for the deep-sea drilling rig bottoming process that takes into account the effects of rheological sediments. Background Technology

[0002] As a key piece of equipment for deep-sea resource exploration, the stability of the deep-sea drilling rig during its landing process directly affects the safety and reliability of subsequent drilling operations. In the deep-sea environment, the drilling rig must overcome the coupling effects of multiple physical fields, such as seawater fluid resistance and sediment contact forces, during the landing phase. Among these, the rheological properties of the sediment significantly influence the interaction mechanism between the drilling rig and the seabed. During the landing process, the drilling rig typically exhibits six degrees of freedom of motion, including vertical settlement, horizontal drift, and pitch / roll attitude changes. These dynamic behaviors are closely related to key technical parameters such as the structural strength design of the drilling rig and the cushioning performance of its outriggers.

[0003] Current research on the landing dynamics of deep-sea drilling rigs has significant limitations. Traditional methods often employ simplified contact models, such as the linear viscoelastic assumptions based on the Kelvin-Voigt model, which cannot accurately characterize the nonlinear rheological properties of deep-sea sediments. In terms of dynamic modeling, existing methods often decouple vertical and horizontal motion, neglecting the coupling effects between multiple degrees of freedom, leading to inaccuracies in the predicted landing attitude of the drilling rig. Furthermore, existing technologies lack systematic analysis of extreme conditions, particularly failing to consider the dynamic response under the combined effects of rugged seabed topography and the towing force of ship cables, making it difficult to identify key parameters such as the maximum impact load, thus affecting the accuracy of drilling rig structural safety assessments. These shortcomings make traditional calculation methods insufficient to meet the engineering requirements of drilling rig optimization design under complex sea conditions. Summary of the Invention

[0004] To address the technical problem that existing calculation methods fail to adequately consider the nonlinear time-varying environmental forces in the deep sea (especially the rheological properties of sediments), leading to inaccurate predictions of the drilling rig's bottom-landing dynamic behavior, this invention provides a calculation method for the deep-sea drilling rig's bottom-landing process that considers the effects of rheological sediments. This invention achieves accurate calculation of the drilling rig's bottom-landing dynamic behavior and prediction of extreme operating conditions by constructing a multi-stage, multi-degree-of-freedom model, deriving nonlinear environmental force equations, and combining them with a genetic algorithm.

[0005] The technical means employed in this invention are as follows: A calculation method for the deep-sea drilling rig bottoming process considering the effects of rheological sediments includes: S1. Establish a multi-degree-of-freedom dynamic model for the drilling rig: Divide the entire process of the drilling rig landing into three stages: free fall, two sets of outriggers touching the bottom first, and three sets of outriggers landing simultaneously. Establish a coordinate transformation matrix between the world coordinate system and the drilling rig's body coordinate system to form a multi-degree-of-freedom dynamic equation containing total mass, additional mass, Coriolis force, damping force, and restoring force. S2. Calculate nonlinear environmental forces: Introduce seawater-added mass force, fluid Coriolis force, linear fluid damping force, sediment support force based on Zener model, and sediment friction force based on Mohr-Coulomb law into the multi-degree-of-freedom dynamic equations to obtain nonlinear environmental forces that vary with velocity, subsidence depth, and time. S3. Extreme working condition prediction using genetic algorithm: Using seabed slope angle, initial pitch angle, sediment stiffness coefficient and internal friction angle as independent variables, the genetic algorithm is used to iteratively solve the multi-degree-of-freedom dynamic equations and output the extreme working condition parameter combination that causes the drilling rig to have the maximum acceleration extreme value, the maximum support force extreme value or the maximum sinking depth extreme value, so as to realize the accurate calculation and safety assessment of the dynamic behavior of the drilling rig when it hits the bottom.

[0006] Further, step S1 includes: S11. Establish three types of Cartesian coordinate systems, including the world coordinate system. Geodetic coordinate system and drilling rig coordinate system ; S12. Establish a coordinate transformation matrix between the world coordinate system and the geodetic coordinate system, as follows:

[0007] in, Indicates the angle of the seabed slope; S13. Establish a coordinate transformation matrix between the world coordinate system and the drilling rig coordinate system, as follows:

[0008] in, Indicates the drilling rig's pitch angle; S14. Perform stress analysis on the deep-sea drilling rig, using the following formula:

[0009]

[0010]

[0011]

[0012]

[0013] in, Indicates external force; Indicates external torque; Indicates seawater resistance; Indicates the supporting force of sediments; Indicates frictional force; This indicates the lateral distance between the two sets of foot pads that touch the bottom first and the center of gravity of the drilling rig. This indicates the vertical distance between the three foot pad planes and the drill rig's center of mass; This represents the resultant force of gravity and buoyancy; S15. The drilling rig's bottoming process is divided into three stages: the free fall stage, the two sets of outriggers touching the bottom stage, and the three sets of outriggers sitting on the bottom stage. During the free fall stage, the dynamic parameters... During the bottoming phase of both outriggers, ; S16. Construct the multi-degree-of-freedom dynamic equations containing total mass, additional mass, Coriolis force, damping force, and restoring force, as follows:

[0014] in, This represents the mass matrix, which includes the added mass. Represents the velocity matrix; Represents the Coriolis force matrix; Represents the fluid damping matrix; This represents the restoring force matrix, which includes gravity and buoyancy. This represents environmental forces, specifically the contact force between the drill's feet and the sediment during the drilling rig's descent. Indicates driving force.

[0015] Further, step S11 includes: S111, Establishing a world coordinate system ,in, The axis is vertically upward and opposite to the direction of gravity. and The plane that forms the plane is perpendicular to axis; S112. Establish a geodetic coordinate system Among them, the origin With world coordinate system coincide, The axis is perpendicular to the , The formed landing surface faces upwards, with an angle of inclination towards the seabed. Depend on shaft and The included angle of the axis is represented; S112. Establish the drilling rig coordinate system The drilling rig coordinate system is located inside the drilling rig main unit, with the origin at... The center of gravity coincides with that of the drilling rig main unit. Parallel to the vertical centerline of the drilling rig; at the initial moment... Parallel to , Parallel to When the drilling rig starts to rotate, shaft and The shaft rotates together with the drilling rig; for the symmetrical bottoming mode of the drilling rig, the drilling rig pitch angle... Depend on shaft and The included angle of the axis is represented.

[0016] Further, step S2 includes: S21. Define nonlinear environmental forces, including fluid forces, bottom sediment support forces, and sediment friction forces; S22. The fluid force is obtained using the added mass method, wherein: The additional mass force in the horizontal direction is applied using Minorsky's empirical formula:

[0017] in, Indicates the added mass in the horizontal direction. Indicates the quality of the drilling rig; The additional mass force in the vertical direction is applied using the empirical formula of Motora:

[0018] in, Indicates the added mass in the vertical direction; The additional moment of inertia during rotation is given by Petersen's empirical formula:

[0019] in, Indicates the additional moment of inertia during rotation. This represents the moment of inertia of the drilling rig. The formula for calculating the additional mass matrix is ​​as follows:

[0020] In underwater dynamics calculations, the influence of the Coriolis force of the additional mass fluid on the drilling rig must be considered. The fluid Coriolis force matrix... The function related to drilling rig speed is expressed as:

[0021] Due to the viscosity of seawater, the effect of viscosity on the drilling rig must also be considered. Linear viscous damping is used to describe the seawater damping force:

[0022] S23. The Zener model is used to describe the mechanical properties of the foot and deep-sea sediments, where: The Zener model is equivalent to a Kelvin body connected in series with a Hooke body (spring). The stress-strain relationship of the overall system is as follows:

[0023] in, express Damping coefficient of the body; express The stiffness coefficient of the body; express The stiffness coefficient of the body; This represents the rate of change of total stress; Indicates the total stress; Indicates total strain. This represents the rate of change of total stress; When the drilling rig comes into contact with the bottom sediment, the deep-sea sediment transmits the supporting force to the rig through its foot; the rig's foot receives the supporting force from the bottom sediment and transmits this force to the main unit through its outriggers; the supporting force of the bottom sediment is equivalent to the connection between the rigid surface Zener model and the foot; the expression for the sediment supporting force using the Zener model is:

[0024] in, , , Both indicate that deep-sea sediments are equivalent to mechanical parameters related to viscoelasticity; S24. The mechanical model of frictional force in deep-sea sediments adopts the Mohr-Coulomb law. The friction coefficient of sediments is given by their shear strength, which satisfies the Mohr-Coulomb law.

[0025] in, This indicates the shear strength that causes friction in deep-sea sediments. Indicates the cohesiveness of deep-sea sediments. Indicates the normal stress on the shear plane. Indicates the internal friction angle of deep-sea sediments; The conditions for determining friction are as follows:

[0026] in, This indicates the contact area between the footpad and the sediment.

[0027] Further, step S3 includes: S31. Establish numerical models of the free fall phase, the phase in which two sets of outriggers touch the bottom first, and the phase in which three sets of outriggers simultaneously hit the bottom using MATLAB. S32. Input the drilling rig mass, initial drilling rig centroid position coordinates, initial pitch angle, seabed slope angle, sediment coefficient, and seawater force coefficient; S33. Solve the numerical model of the free fall phase using the implicit solution of differential equations (ode15s) and determine whether two sets of outriggers have touched the bottom. If two sets of outriggers have touched the bottom, solve the numerical model of the phase where the two sets of outriggers touch the bottom first using the implicit solution of differential equations (ode15s) and determine whether a third set of outriggers has touched the bottom. If all three sets of outriggers touch the bottom simultaneously, solve the numerical model of the phase where all three sets of outriggers touch the bottom simultaneously using the implicit solution of differential equations (ode15s) and determine whether the set simulation time has been reached. S34. If the set simulation time is reached, output the horizontal acceleration of the drilling rig, the vertical acceleration of the drilling rig, the pitch angle of the drilling rig, the angular acceleration of the drilling rig, the outrigger penetration depth, and the support force. S35. Set four independent environmental parameters, namely, seabed slope angle. Initial pitch angle Sediment stiffness coefficient and the internal friction angle of sediments ; S36. To ensure the drilling rig reaches the bottom and avoid repeated working conditions, constraints are added to the initial pitch angle and seabed slope angle:

[0028] S37. Based on the drilling rig's bottoming response under different working conditions, the extreme working conditions are defined as follows: The drilling rig reaches its maximum acceleration extreme value; The drilling rig reached its maximum support force extreme value; The drilling rig's outriggers reached their maximum sinking depth. S38. Initialization: Randomly generate 100 individuals within the range of independent variables to initialize the population, and set the iteration limit to 200; S39. Individual Evolution: The initial parameters are substituted into the multi-degree-of-freedom dynamic model of the drilling rig for calculation. The dynamic extreme values ​​under each parameter are obtained, and the dynamic extreme values ​​are used as the fitness of the individual. S310, Selection Operation: Randomly select individuals based on fitness; S311, Crossover operation: In order to pass on the genes of individuals with higher fitness to the next generation, the genes are crossed over. S312, Mutation Operation: To maintain the genetic diversity of the population, a mutation operation is set; S313. Generate a new population: After selection, crossover and mutation operations, a new population is obtained. In addition, the population is sorted according to its fitness, and selection, crossover and mutation operations are performed again. S314. When the number of iterations is reached, the iteration stops. At this point, the individual with the highest fitness is the optimal individual, and the environmental parameters of the extreme landing conditions are obtained.

[0029] Compared with the prior art, the present invention has the following advantages: 1. This invention fills the gap in existing research on the multi-degree-of-freedom dynamic response of deep-sea drilling rigs under nonlinear time-varying environmental forces. Its numerical model and experimental data are in good agreement, which can provide accurate reference for the design and application of marine exploration equipment and effectively improve the applicability of drilling rigs in complex sea conditions such as rugged seabeds and towed cables.

[0030] 2. This invention is based on a multi-degree-of-freedom landing dynamics model built independently using MATLAB. It divides the motion state into three stages: free fall, landing of two sets of outriggers, and landing of three sets of outriggers, and establishes corresponding force equations. Furthermore, it adopts the method of adding mass to incorporate fluid forces into the dynamic equations, which closely matches the actual landing process of the drilling rig. This avoids the deviation in force and dynamic behavior calculation caused by general modeling and accurately captures the coupling effect of horizontal translation, vertical translation, and rotational degrees of freedom.

[0031] 3. The contact force model derived from the external load characteristics of the drilling rig in this invention, based on the Zener model, can fully reflect the rheological characteristics of deep-sea sediments (with a higher degree of agreement with experimental data compared to traditional models). Based on the Mohr-Coulomb law, it can effectively consider the cohesive force of sediments, thus solving the problem of inaccurate calculation of sediment rheological characteristics and friction.

[0032] 4. This invention combines a genetic algorithm to predict multi-factor extreme bottoming conditions. It can quickly iterate and optimize using seabed slope angle, initial pitch angle, etc. as independent variables, and accurately obtain the input parameters for extreme conditions such as maximum acceleration, contact force, and extreme depth of the drilling rig. This solves the problem that traditional methods are difficult to efficiently determine extreme dangerous conditions and provides a direct basis for drilling rig structural safety verification and risk avoidance. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart of the method of the present invention.

[0035] Figure 2 This is a schematic diagram illustrating the establishment of the coordinate system in this invention.

[0036] Figure 3 This is a flowchart of the drilling rig dynamics calculation for this invention.

[0037] Figure 4 This is a flowchart of the genetic algorithm of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0040] like Figure 1 As shown, this invention provides a calculation method for the deep-sea drilling rig's bottom-landing process that considers the effects of rheological sediments, including: S1. Establish a multi-degree-of-freedom dynamic model for the drilling rig: The entire process of the drilling rig landing is divided into three stages: free fall, two sets of outriggers touching the bottom first, and all three sets of outriggers landing simultaneously. A coordinate transformation matrix is ​​established between the world coordinate system and the drilling rig's body coordinate system, forming a multi-degree-of-freedom dynamic equation containing total mass, added mass, Coriolis force, damping force, and restoring force. In this embodiment, the drilling rig model consists of the drilling rig body and the outrigger structure. The drilling rig body is stably supported by the outrigger structure. This ensures a symmetrical landing mode (two sets of outriggers touch the bottom first, and the remaining set of outriggers touches the bottom last). The two sets of outriggers that contact the seabed first are dynamically equivalent, and the forces and movements of the two sets of outriggers are consistent.

[0041] S2. Calculate nonlinear environmental forces: Introduce seawater-added mass force, fluid Coriolis force, linear fluid damping force, sediment support force based on Zener model, and sediment friction force based on Mohr-Coulomb law into the multi-degree-of-freedom dynamic equations to obtain nonlinear environmental forces that vary with velocity, subsidence depth, and time. S3. Extreme working condition prediction using genetic algorithm: Using seabed slope angle, initial pitch angle, sediment stiffness coefficient and internal friction angle as independent variables, the genetic algorithm is used to iteratively solve the multi-degree-of-freedom dynamic equations and output the extreme working condition parameter combination that causes the drilling rig to have the maximum acceleration extreme value, the maximum support force extreme value or the maximum sinking depth extreme value, so as to realize the accurate calculation and safety assessment of the dynamic behavior of the drilling rig when it hits the bottom.

[0042] In a specific implementation, as a preferred embodiment of the present invention, step S1 includes: S11. Establish three types of Cartesian coordinate systems, including the world coordinate system. Geodetic coordinate system and drilling rig coordinate system ; S12. Establish a coordinate transformation matrix between the world coordinate system and the geodetic coordinate system, as follows:

[0043] in, Indicates the angle of the seabed slope; S13. Establish a coordinate transformation matrix between the world coordinate system and the drilling rig coordinate system, as follows:

[0044] in, Indicates the drilling rig's pitch angle; S14. Perform stress analysis on the deep-sea drilling rig, using the following formula:

[0045]

[0046]

[0047]

[0048]

[0049] in, Indicates external force; Indicates external torque; Indicates seawater resistance; Indicates the supporting force of sediments; Indicates frictional force; This indicates the lateral distance between the two sets of foot pads that touch the bottom first and the center of gravity of the drilling rig. This indicates the vertical distance between the three foot pad planes and the drill rig's center of mass; This represents the resultant force of gravity and buoyancy; S15. The drilling rig's bottoming process is divided into three stages: the free fall stage, the two sets of outriggers touching the bottom stage, and the three sets of outriggers sitting on the bottom stage. During the free fall stage, the dynamic parameters... During the bottoming phase of both outriggers, ; S16. Construct the multi-degree-of-freedom dynamic equations containing total mass, additional mass, Coriolis force, damping force, and restoring force, as follows:

[0050] in, This represents the mass matrix, which includes the added mass. Represents the velocity matrix; Represents the Coriolis force matrix; Represents the fluid damping matrix; This represents the restoring force matrix, typically referring to gravity and buoyancy. This represents environmental forces, specifically the contact force between the drill's feet and the sediment during the drilling rig's descent. Indicates driving force.

[0051] In this embodiment, a world coordinate system is first established ( , (axis vertically upward), geodetic coordinate system ( , (axis perpendicular to seabed surface), host coordinate system ( The three coordinate systems (origin and center of mass of the drilling rig coincide) define the three core degrees of freedom of the drilling rig. Horizontal translation of the axis Vertical translation of the axis (Plane rotation); then, according to the order of the outriggers touching the bottom, the landing process is divided into three stages and targeted force equations are established: the free fall stage (from the release of the drilling rig to the bottoming of the two sets of outriggers) only includes gravity, buoyancy and seawater resistance; the landing stage of the two sets of outriggers (from the bottoming of the two sets of outriggers to the bottoming of the third set of outriggers) adds the support force and friction force of the symmetrical outriggers; the landing stage of the three sets of outriggers (from the bottoming of the third set of outriggers to the stabilization of the drilling rig) adds the contact force of the asymmetrical outriggers. The matrix form of the equations clearly includes key terms such as total mass (including additional mass), Coriolis force, and damping force, ensuring accurate capture of the dynamic behavior of each stage.

[0052] In specific implementation, as a preferred embodiment of the present invention, such as Figure 2 As shown, step S11 includes: S111, Establishing a world coordinate system ,in, The axis is vertically upward and opposite to the direction of gravity. and The plane that forms the plane is perpendicular to axis; S112. Establish a geodetic coordinate system Among them, the origin With world coordinate system coincide, The axis is perpendicular to the , The formed landing surface faces upwards, with an angle of inclination towards the seabed. Depend on shaft and The included angle of the axis is represented; S112. Establish the drilling rig coordinate system The drilling rig coordinate system is located inside the drilling rig main unit, with the origin at... The center of gravity coincides with that of the drilling rig main unit. Parallel to the vertical centerline of the drilling rig; at the initial moment... Parallel to , Parallel to When the drilling rig starts to rotate, shaft and The shaft rotates together with the drilling rig; for the symmetrical bottoming mode of the drilling rig, the drilling rig pitch angle... Depend on shaft and The included angle of the axis is represented.

[0053] In a specific implementation, as a preferred embodiment of the present invention, step S2 includes: S21. Define nonlinear environmental forces, including fluid forces, bottom sediment support forces, and sediment friction forces; S22. The fluid force is obtained using the added mass method, wherein: The additional mass force in the horizontal direction is applied using Minorsky's empirical formula:

[0054] in, Indicates the added mass in the horizontal direction. Indicates the quality of the drilling rig; The additional mass force in the vertical direction is applied using the empirical formula of Motora:

[0055] in, This represents the added mass in the vertical direction; in this embodiment, the vertical added mass coefficient is 0.07.

[0056] The additional moment of inertia during rotation is given by Petersen's empirical formula:

[0057] in, Indicates the additional moment of inertia during rotation. This represents the moment of inertia of the drilling rig. The formula for calculating the additional mass matrix is ​​as follows:

[0058] In underwater dynamics calculations, the influence of the Coriolis force of the additional mass fluid on the drilling rig must be considered. The fluid Coriolis force matrix... The function related to drilling rig speed is expressed as:

[0059] Due to the viscosity of seawater, the effect of viscosity on the drilling rig must also be considered. Linear viscous damping is used to describe the seawater damping force:

[0060] S23. The Zener model is used to describe the mechanical properties of the foot and deep-sea sediments, where: The Zener model is equivalent to a Kelvin body connected in series with a Hooke body (spring). The stress-strain relationship of the overall system is as follows:

[0061] in, express Damping coefficient of the body; express The stiffness coefficient of the body; express The stiffness coefficient of the body; This represents the rate of change of total stress; Indicates the total stress; Indicates total strain. This represents the rate of change of total stress; When the drilling rig comes into contact with the bottom sediment, the deep-sea sediment transmits the supporting force to the rig through its foot; the rig's foot receives the supporting force from the bottom sediment and transmits this force to the main unit through its outriggers; the supporting force of the bottom sediment is equivalent to the connection between the rigid surface Zener model and the foot; the expression for the sediment supporting force using the Zener model is:

[0062] in, , , All these represent the equivalent mechanical parameters of deep-sea sediments related to viscoelasticity; in this embodiment, the following are set... , , ; S24. The mechanical model of frictional force in deep-sea sediments adopts the Mohr-Coulomb law. The friction coefficient of sediments is given by their shear strength, which satisfies the Mohr-Coulomb law.

[0063] in, This indicates the shear strength that causes friction in deep-sea sediments. Indicates the cohesiveness of deep-sea sediments. Indicates the normal stress on the shear plane. Indicates the internal friction angle of deep-sea sediments; The conditions for determining friction are as follows:

[0064] in, This indicates the contact area between the footpad and the sediment.

[0065] In this embodiment, the three-stage motion state of the drilling rig landing is divided and the force equation is established. The fluid force calculation adopts the classical empirical formula with correction. The horizontal additional mass is based on the Minorsky empirical formula, the vertical direction is based on the Motora correction value, and the additional rotational inertia is based on the Petersen formula. At the same time, the velocity-related fluid Coriolis force matrix and the linear fluid damping matrix are derived. The sediment contact force calculation innovatively adopts the Zener model to describe the support force, which can accurately reflect the rheological characteristics of sediments. The friction force calculation is based on the Mohr-Coulomb law, and the parameters are referenced from the data of polymetallic crust mining areas in the Chinese ocean, avoiding the errors of the traditional fixed friction coefficient method.

[0066] In a specific implementation, as a preferred embodiment of the present invention, step S3 includes: S31. Establish numerical models of the free fall phase, the phase in which two sets of outriggers touch the bottom first, and the phase in which three sets of outriggers simultaneously hit the bottom using MATLAB. S32, such as Figure 3 As shown, input the drilling rig mass, initial drilling rig centroid coordinates, initial pitch angle, seabed slope angle, sediment coefficient, and seawater force coefficient; S33. Solve the numerical model of the free fall phase using the implicit solution of differential equations (ode15s) and determine whether two sets of outriggers have touched the bottom. If two sets of outriggers have touched the bottom, solve the numerical model of the phase where the two sets of outriggers touch the bottom first using the implicit solution of differential equations (ode15s) and determine whether a third set of outriggers has touched the bottom. If all three sets of outriggers touch the bottom simultaneously, solve the numerical model of the phase where all three sets of outriggers touch the bottom simultaneously using the implicit solution of differential equations (ode15s) and determine whether the set simulation time has been reached. S34. If the set simulation time is reached, output the horizontal acceleration of the drilling rig, the vertical acceleration of the drilling rig, the pitch angle of the drilling rig, the angular acceleration of the drilling rig, the outrigger penetration depth, and the support force. S35, such as Figure 4 As shown, four independent environmental parameters are set, namely the seabed slope angle. Initial pitch angle Sediment stiffness coefficient and the internal friction angle of sediments In this embodiment, the seabed slope angle The range is Step size is Initial pitch angle The range is Step size is Sediment stiffness coefficient The range is 1000-3000 kN / m, with a step size of 100 kN / m.

[0067] S36. To ensure the drilling rig reaches the bottom and avoid repeated working conditions, constraints are added to the initial pitch angle and seabed slope angle:

[0068] S37. Based on the drilling rig's bottoming response under different working conditions, the extreme working conditions are defined as follows: The drilling rig reaches its maximum acceleration extreme value; The drilling rig reached its maximum support force extreme value; The drilling rig's outriggers reached their maximum sinking depth. S38. Initialization: Randomly generate 100 individuals within the range of independent variables to initialize the population, and set the iteration limit to 200; S39. Individual Evolution: The initial parameters are substituted into the multi-degree-of-freedom dynamic model of the drilling rig for calculation. The dynamic extreme values ​​under each parameter are obtained, and the dynamic extreme values ​​are used as the fitness of the individual. S310. Selection operation: Randomly select individuals based on fitness; In this embodiment, a roulette wheel selection method is used, which ensures that the chance of being selected is proportional to fitness, and excellent individuals can generate subpopulations; S311, Crossover operation: In order to pass on the genes (independent variables) of individuals with higher fitness to the next generation, the genes are crossed over; in this embodiment, the crossover probability is set to 0.8.

[0069] S312, Mutation Operation: To maintain the genetic diversity of the population, a mutation operation is set; in this embodiment, since mutation is not always a positive effect, the mutation probability is set to 0.1.

[0070] S313. Generate a new population: After selection, crossover and mutation operations, a new population is obtained. In addition, the population is sorted according to its fitness, and selection, crossover and mutation operations are performed again. S314. When the number of iterations is reached, the iteration stops. At this point, the individual with the highest fitness is the optimal individual, and the environmental parameters of the extreme landing conditions are obtained.

[0071] In this embodiment, the seabed slope angle, initial pitch angle, sediment stiffness coefficient, and internal friction angle are used as independent variables. The extreme operating condition parameters are output through a process of "initializing individuals – calculating dynamic extreme values ​​as fitness – roulette wheel selection – crossover and mutation genetic operations – iteration to convergence number". This invention can provide precise theoretical basis for deep-sea drilling rig design and safe seabed assessment, improving the applicability of drilling rigs in complex sea conditions.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A calculation method for the deep-sea drilling rig's bottom-landing process considering the effects of rheological sediments, characterized in that, include: S1. Establish a multi-degree-of-freedom dynamic model for the drilling rig: Divide the entire process of the drilling rig landing into three stages: free fall, two sets of outriggers touching the bottom first, and three sets of outriggers landing simultaneously. Establish a coordinate transformation matrix between the world coordinate system and the drilling rig's body coordinate system to form a multi-degree-of-freedom dynamic equation containing total mass, additional mass, Coriolis force, damping force, and restoring force. S2. Calculate nonlinear environmental forces: Introduce seawater-added mass force, fluid Coriolis force, linear fluid damping force, sediment support force based on Zener model, and sediment friction force based on Mohr-Coulomb law into the multi-degree-of-freedom dynamic equations to obtain nonlinear environmental forces that vary with velocity, subsidence depth, and time. S3. Extreme working condition prediction using genetic algorithm: Using seabed slope angle, initial pitch angle, sediment stiffness coefficient and internal friction angle as independent variables, the genetic algorithm is used to iteratively solve the multi-degree-of-freedom dynamic equations and output the extreme working condition parameter combination that causes the drilling rig to have the maximum acceleration extreme value, the maximum support force extreme value or the maximum sinking depth extreme value, so as to realize the accurate calculation and safety assessment of the dynamic behavior of the drilling rig when it hits the bottom.

2. The calculation method for the deep-sea drilling rig bottoming process considering the effects of rheological sediments as described in claim 1, characterized in that, Step S1 includes: S11. Establish three types of Cartesian coordinate systems, including the world coordinate system. Geodetic coordinate system and drilling rig coordinate system ; S12. Establish a coordinate transformation matrix between the world coordinate system and the geodetic coordinate system, as follows: in, Indicates the angle of the seabed slope; S13. Establish a coordinate transformation matrix between the world coordinate system and the drilling rig coordinate system, as follows: in, Indicates the drilling rig's pitch angle; S14. Perform stress analysis on the deep-sea drilling rig, using the following formula: in, Indicates external force; Indicates external torque; Indicates seawater resistance; Indicates the supporting force of sediments; Indicates frictional force; This indicates the lateral distance between the two sets of foot pads that touch the bottom first and the center of gravity of the drilling rig. This indicates the vertical distance between the three foot pad planes and the drill rig's center of mass; This represents the resultant force of gravity and buoyancy; S15. The drilling rig's bottoming process is divided into three stages: the free fall stage, the two sets of outriggers touching the bottom stage, and the three sets of outriggers sitting on the bottom stage. During the free fall stage, the dynamic parameters... During the bottoming phase of both outriggers, ; S16. Construct the multi-degree-of-freedom dynamic equations containing total mass, additional mass, Coriolis force, damping force, and restoring force, as follows: in, This represents the mass matrix, which includes the added mass. Represents the velocity matrix; Represents the Coriolis force matrix; Represents the fluid damping matrix; This represents the restoring force matrix, which includes gravity and buoyancy. This represents environmental forces, specifically the contact force between the drill's feet and the sediment during the drilling rig's descent. Indicates driving force.

3. The calculation method for the deep-sea drilling rig bottoming process considering the effects of rheological sediments according to claim 2, characterized in that, Step S11 includes: S111, Establishing a world coordinate system ,in, The axis is vertically upward and opposite to the direction of gravity. and The plane that forms the plane is perpendicular to axis; S112. Establish a geodetic coordinate system Among them, the origin With world coordinate system coincide, The axis is perpendicular to the , The formed landing surface faces upwards, with an angle of inclination towards the seabed. Depend on shaft and The included angle of the axis is represented; S112. Establish the drilling rig coordinate system The drilling rig coordinate system is located inside the drilling rig main unit, with the origin at... The center of gravity coincides with that of the drilling rig main unit. Parallel to the vertical centerline of the drilling rig; at the initial moment... Parallel to , Parallel to When the drilling rig starts to rotate, shaft and The shaft rotates together with the drilling rig; for the symmetrical bottoming mode of the drilling rig, the drilling rig pitch angle... Depend on shaft and The included angle of the axis is represented.

4. The calculation method for the deep-sea drilling rig bottoming process considering the effects of rheological sediments as described in claim 1, characterized in that, Step S2 includes: S21. Define nonlinear environmental forces, including fluid forces, bottom sediment support forces, and sediment friction forces; S22. The fluid force is obtained using the added mass method, wherein: The additional mass force in the horizontal direction is applied using Minorsky's empirical formula: in, Indicates the added mass in the horizontal direction. Indicates the quality of the drilling rig; The additional mass force in the vertical direction is applied using the empirical formula of Motora: in, Indicates the added mass in the vertical direction; The additional moment of inertia during rotation is given by Petersen's empirical formula: in, Indicates the additional moment of inertia during rotation. This represents the moment of inertia of the drilling rig. The formula for calculating the additional mass matrix is ​​as follows: In underwater dynamics calculations, the influence of the Coriolis force of the additional mass fluid on the drilling rig must be considered. The fluid Coriolis force matrix... The function related to drilling rig speed is expressed as: Due to the viscosity of seawater, the effect of viscosity on the drilling rig must also be considered. Linear viscous damping is used to describe the seawater damping force: S23. The Zener model is used to describe the mechanical properties of the foot and deep-sea sediments, where: The Zener model is equivalent to a Kelvin body connected to a Hooke body, and the stress-strain relationship of the overall system is: in, express Damping coefficient of the body; express The stiffness coefficient of the body; express The stiffness coefficient of the body; This represents the rate of change of total stress; Indicates the total stress; Indicates total strain. This represents the rate of change of total stress; When the drilling rig comes into contact with the bottom sediment, the deep-sea sediment transmits the supporting force to the rig through its foot; the rig's foot receives the supporting force from the bottom sediment and transmits this force to the main unit through its outriggers; the supporting force of the bottom sediment is equivalent to the connection between the rigid surface Zener model and the foot; the expression for the sediment supporting force using the Zener model is: in, , , Both indicate that deep-sea sediments are equivalent to mechanical parameters related to viscoelasticity; S24. The mechanical model of frictional force in deep-sea sediments adopts the Mohr-Coulomb law. The friction coefficient of sediments is given by their shear strength, which satisfies the Mohr-Coulomb law. in, This indicates the shear strength that causes friction in deep-sea sediments. Indicates the cohesiveness of deep-sea sediments. Indicates the normal stress on the shear plane. Indicates the internal friction angle of deep-sea sediments; The conditions for determining friction are as follows: in, This indicates the contact area between the footpad and the sediment.

5. The calculation method for the deep-sea drilling rig bottoming process considering the effects of rheological sediments according to claim 1, characterized in that, Step S3 includes: S31. Establish numerical models of the free fall phase, the phase in which two sets of outriggers touch the bottom first, and the phase in which three sets of outriggers simultaneously hit the bottom using MATLAB. S32. Input the drilling rig mass, initial drilling rig centroid position coordinates, initial pitch angle, seabed slope angle, sediment coefficient, and seawater force coefficient; S33. Solve the numerical model of the free fall phase using the implicit solution of differential equations, and determine whether two sets of outriggers touch the bottom. If two sets of outriggers touch the bottom, solve the numerical model of the phase where the two sets of outriggers touch the bottom first using the implicit solution of differential equations, and determine whether a third set of outriggers touches the bottom. If all three sets of outriggers touch the bottom simultaneously, solve the numerical model of the phase where all three sets of outriggers touch the bottom simultaneously using the implicit solution of differential equations, and determine whether the set simulation time has been reached. S34. If the set simulation time is reached, output the horizontal acceleration of the drilling rig, the vertical acceleration of the drilling rig, the pitch angle of the drilling rig, the angular acceleration of the drilling rig, the outrigger penetration depth, and the support force. S35. Set four independent environmental parameters, namely, seabed slope angle. Initial pitch angle Sediment stiffness coefficient Angle of friction between sediments and internal friction ; S36. To ensure the drilling rig reaches the bottom and avoid repeated working conditions, constraints are added to the initial pitch angle and seabed slope angle: S37. Based on the drilling rig's bottoming response under different working conditions, the extreme working conditions are defined as follows: The drilling rig reaches its maximum acceleration extreme value; The drilling rig reached its maximum support force extreme value; The drilling rig's outriggers reached their maximum sinking depth. S38. Initialization: Randomly generate 100 individuals within the range of independent variables to initialize the population, and set the iteration limit to 200; S39. Individual Evolution: The initial parameters are substituted into the multi-degree-of-freedom dynamic model of the drilling rig for calculation. The dynamic extreme values ​​under each parameter are obtained, and the dynamic extreme values ​​are used as the fitness of the individual. S310, Selection Operation: Randomly select individuals based on fitness; S311, Crossover operation: In order to pass on the genes of individuals with higher fitness to the next generation, the genes are crossed over. S312, Mutation Operation: To maintain the genetic diversity of the population, a mutation operation is set; S313. Generate a new population: After selection, crossover and mutation operations, a new population is obtained. In addition, the population is sorted according to its fitness, and selection, crossover and mutation operations are performed again. S314. When the number of iterations is reached, the iteration stops. At this point, the individual with the highest fitness is the optimal individual, and the environmental parameters of the extreme landing conditions are obtained.

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