Numerical simulation method for hard bottom process of deep sea subsea drilling rig

Abstract

This invention discloses a numerical simulation method for the hard landing process of a deep-sea subsea drilling rig, comprising the following steps: 1) establishing a dynamic model of the hard landing of the deep-sea subsea drilling rig, including basic model assumptions, definition of the coordinate system, landing dynamic equations and kinematic equations, outrigger axial force sub-model, footboard-seabed contact force sub-model, and seawater force sub-model; 2) setting model parameters; 3) determining the initial conditions for solving the dynamic model of the hard landing of the deep-sea subsea drilling rig; 4) performing numerical simulation of the hard landing process of the deep-sea subsea drilling rig. This invention can meet the numerical simulation analysis needs of different specifications of deep-sea subsea drilling rigs using different landing control parameters on seabeds of different properties, providing theoretical basis and guidance for the optimized design of subsea drilling rig support systems and the landing control of subsea drilling rigs.

Description

Technical Field

[0001] This invention belongs to the field of underwater deployment and landing technology of deep-sea subsea drilling rigs, and specifically relates to a numerical simulation method for the hard landing process of deep-sea subsea drilling rigs. Background Technology

[0002] Deep-sea drilling rigs are key technological equipment for conducting marine geological and environmental scientific research, marine resource exploration, and seabed engineering geological surveys. Underwater deployment is a crucial preliminary step for drilling and coring operations, typically involving three steps: lowering, site selection, and landing. First, the rig is lowered to approximately 2-5 meters above the sea surface using an armored umbilical winch on the mother ship. Then, the seabed topography is observed using a site selection camera. Once the topography meets the landing conditions, the landing operation commences. Landing is the decisive step in underwater deployment. However, the mother ship inevitably experiences swaying motion due to ocean currents and waves, and the drilling rig itself also sways and rocks in the water due to the traction of the armored umbilical cable. Therefore, the soft landing method of directly lowering the rig to the seabed via the umbilical cable is practically impossible and could result in repeated lifting or even capsizing. Therefore, after the site search is completed, the outriggers of the drilling rig are usually deployed and the winch is operated to quickly release the cable, so that the drilling rig can make a hard landing in a near free fall manner. After the drilling rig touches the seabed, about 10 meters of cable should be released to isolate the impact of the mother ship's swaying motion on the drilling rig.

[0003] Hard landing of a subsea drilling rig will generate impact, which may not only cause structural damage to the rig's components due to excessive load, and damage to internal electronic instruments due to instantaneous acceleration overload, but also lead to excessive sinking depth of the rig due to impact with the seabed, intrusion of soft sediments into the rig's interior, and even deflection or capsizing during the impact rebound. Therefore, in order to achieve safe and reliable landing of deep-sea drilling rigs using the hard landing method, it is necessary to conduct numerical simulation of the hard landing process. This can also provide theoretical basis and guidance for the optimized design of the subsea drilling rig support system and the landing control of the subsea drilling rig. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a numerical simulation method for the hard landing process of a deep-sea subsea drilling rig. This method can simulate and predict the motion trajectory of the rig's outriggers, the stress on the outriggers, the magnitude of the transient acceleration of the rig's center of mass, the sinking depth of the outrigger footplates, and the deflection of the rig body. Based on this, it can determine whether the rig can successfully land under specified landing conditions and the ease of leveling the rig body after successful landing. This feedback information can then be used to guide the landing control of the rig, such as adjusting the outrigger deployment angle and the rig's release height from the bottom.

[0005] The technical solution adopted in this invention is: a numerical simulation method for the hard landing process of a deep-sea subsea drilling rig, comprising the following steps:

[0006] Step 1: Establish a dynamic model for the hard landing of a deep-sea subsea drilling rig;

[0007] Step 2: Set the parameters of the deep-sea subsea drilling rig, the landing control parameters, and the mechanical properties of the seabed in the model;

[0008] Step 3: Determine the initial conditions for solving the dynamic model of hard landing of deep-sea subsea drilling rigs;

[0009] Step 4: Perform numerical simulation of the hard landing process of the deep-sea drilling rig.

[0010] Furthermore, the specific steps for step 1 are as follows:

[0011] 1.1) The deep-sea drilling rig is simplified into one elastic support subsystem and N inelastic support subsystems, where N is the number of outriggers of the deep-sea drilling rig; and the following assumptions are made about the model:

[0012] 1.1.1) Total mass m of the elastic support subsystem u Concentrated at the center of mass of the deep-sea drilling rig, the elastic support subsystem possesses two translational degrees of freedom and one rotational degree of freedom within the structural symmetry plane of the deep-sea drilling rig during the landing process; the mass m of each inelastic support subsystem... f Concentrated at the connection between their respective foot plates and outriggers, each inelastic support subsystem has two translational degrees of freedom in its respective outrigger plane during landing; the elastic support subsystem and the inelastic support subsystem are connected by the geometric constraints of the outrigger structure to achieve positional constraints and force transmission.

[0013] 1.1.2) The outrigger linkage is equivalent to a rod with axial stiffness and damping, which can transmit lateral force but cannot be bent; the outrigger hydraulic cylinder is regarded as an elastic-damped element that is only subjected to axial force; the structural elasticity of the rest of the deep-sea drilling rig is not considered except for the outrigger hydraulic cylinder and the outrigger linkage.

[0014] 1.2) Introduce a global coordinate system, a body coordinate system, and a leg coordinate system into the model;

[0015] 1.3) Establish the dynamic and kinematic equations for the hard landing of the deep-sea subsea drilling rig, and derive the expression for the lateral force transmitted by the outrigger connecting rod;

[0016] 1.4) Establish the axial force sub-model of the outrigger;

[0017] 1.5) Establish a foot-substrate contact force model;

[0018] 1.6) Establish a sub-model of seawater forces.

[0019] Furthermore, the specific operation of step 1.3) is as follows:

[0020] 1.3.1) For the n independent degrees of freedom of the deep-sea drilling rig hard landing in the model, the dynamic equations of each degree of freedom are established in a suitable coordinate system using Newton's second law, the theorem of angular momentum and the theorem of composition of acceleration; for the geometric variables involved in the dynamic equations, the kinematic equations of the deep-sea drilling rig hard landing are established in the corresponding coordinate system through coordinate and inverse trigonometric function operations.

[0021] 1.3.2) Derive the expression for the lateral force transmitted by each leg link. The specific steps are as follows:

[0022] Based on the translational dynamics equations of any inelastic support subsystem in the selected outrigger coordinate system:

[0023]

[0024] In the formula, m f For the mass of the inelastic support subsystem, r fi Let [x] be the displacement of the inelastic support subsystem in the selected outrigger coordinate system. fSi ,y fSi ,z fSi ] T , These represent the velocity and acceleration of the inelastic support subsystem in the selected outrigger coordinate system, F. sum ω is the net external force acting on this inelastic support subsystem. S , These are the rotational angular velocity and angular acceleration of the selected leg coordinate system relative to the global coordinate system, respectively. Let z be the acceleration of the selected outrigger coordinate system origin relative to the global coordinate system origin; then, combining the assumption in model 1.1.2) that "the outrigger link can transmit lateral force but cannot bend," i.e., the displacement of the inelastic support subsystem along the outrigger lateral direction is 0, we obtain z. fSi =0, and then the expression for the lateral force transmitted by the outrigger connecting rod corresponding to the inelastic support subsystem is derived.

[0025] Furthermore, the specific operation of step 1.4) is as follows:

[0026] 1.4.1) Based on model assumption 1.1.2), the equivalent stiffness k of the outrigger hydraulic cylinder p Represented as:

[0027]

[0028] In the formula: k oil k is the equivalent stiffness coefficient of hydraulic oil.rod k is the piston rod stiffness coefficient. barrel This is the cylinder stiffness coefficient;

[0029] 1.4.2) Equivalent stiffness k of the outrigger link a The equivalent damping coefficient is calculated using the finite element method or from the equivalent cross-sectional dimensions and length, and is given by the following formula: Calculate, where ξ is the damping ratio, m a For the mass of the outrigger connecting rod.

[0030] Furthermore, the specific operation of step 1.5) is as follows:

[0031] 1.5.1) For the normal contact force F between the foot and the substrate n Considering the elastic support and energy dissipation effects of the deep seabed, we obtain F. n =F ela +F dam F ela For the elastic force of the substrate, F dam The bottom damping force is F; where the bottom damping force is F. dam Calculate using the following formula:

[0032]

[0033] In the formula: c sedi Let δ be the bottom mass damping coefficient, and δ be the bottom mass damping coefficient. These represent the sinking depth and sinking speed of the foot, respectively; and the elastic force F of the substrate. ela Considering the dynamic load-bearing capacity of the bottom sediment and the repeated loading and unloading of the footplate:

[0034] First time adding / uninstalling:

[0035]

[0036] The qth (q≥2) addition / unloading:

[0037]

[0038] In the formula: k1 and k2 are the equivalent elastic coefficients of dynamic compression and rebound recovery of the substrate corresponding to the foot area, respectively, and δ1 is... The δ value at the first change of number is the maximum depth of the foot's initial sinking. δ2 is the δ value corresponding to the irreversible plastic deformation of the substrate caused by the initial sinking of the foot.

[0039] 1.5.2) Calculate the horizontal friction force F between the footboard and the substrate. f Considering the effects of relative slippage and sinking depth on friction, the coefficient of friction between the footboard and the substrate, after correction for both sinking depth and relative slippage velocity, is: μ f =μδ +μ k0 +(μ s0 -μ k0 )e -εv , where μ s0 and μ k0 These represent the static and dynamic friction coefficients of the substrate without considering the subsidence depth, respectively; ε is the exponential decay coefficient; v is the relative sliding velocity; and μ is the dynamic friction coefficient. δ Frictional gain caused by subsidence depth:

[0040]

[0041] In the formula: R is the radius of the footboard; F is the horizontal frictional force between the footboard and the substrate. f =μ f ·F n μ f It is the coefficient of friction between the foot and the substrate.

[0042] Furthermore, the specific operation of step 1.6) is as follows:

[0043] The forces exerted on the deep-sea drilling rig during its descent include three components: buoyancy, fluid resistance, and hydrodynamic force. Since the current velocity at the deep seabed is nearly zero, the forces exerted on the elastic support subsystem in the global coordinate system are approximately zero at point O. I X I Shaft and O I Y I The components on the axis are as follows:

[0044]

[0045] In the formula: x u , The elastic support subsystem is located in O I X I Displacement, velocity, and acceleration on the axis, y u , The elastic support subsystem is located in O I Y I Displacement, velocity, and acceleration along the axis, where ρ is the density of seawater, and C dx C dy The elastic support subsystem is located in O I X I Shaft and O I Y I The coefficient of water resistance in the axial direction, C mx C my The elastic support subsystem is located in O I X I Shaft and O I YI Additional mass coefficient in the axial direction, S x S y The elastic support subsystem is located in O I X I Shaft and O I Y I Water-facing area in the axial direction, V u and F bu These represent the volume and buoyancy of the elastic support subsystem, respectively; the seawater buoyancy is calculated from the difference between the weight of the deep-sea subsea drilling rig in air and its weight underwater.

[0046] Furthermore, the specific steps for step 3 are as follows:

[0047] 3.1) The initial position coordinates of the elastic and inelastic support subsystems when the deep-sea subsea drilling rig first touches the bottom are calculated from the structural dimensions of the deep-sea subsea drilling rig and the deployment angle of the outriggers;

[0048] 3.2) Considering the deep-sea drilling rig as a single unit, and simplifying its process from release to initial contact with the bottom as free fall, and assuming a flat seabed topography and simultaneous contact with the bottom by all legs of the deep-sea drilling rig, the initial rotational angular velocity and horizontal velocity of the deep-sea drilling rig are both zero; the dynamic equations of the free fall process of the deep-sea drilling rig are:

[0049]

[0050] In the formula: y t , These represent the vertical displacement, velocity, and acceleration of the deep-sea subsea drilling rig, in meters. t S, V, F b These are the mass, vertical surface area facing the water, volume, and buoyancy force acting on the deep-sea subsea drilling rig, respectively. d C represents the water resistance coefficient of a deep-sea subsea drilling rig in the vertical direction. m Let y be the additional mass coefficient of the deep-sea subsea drilling rig in the vertical direction; solve the differential equation, and let y t0 =H, where H is the release height from the bottom. And in y t The solution is terminated when the value is 0, which gives the magnitude of the vertical velocity of the deep-sea drilling rig when it first touches the bottom.

[0051] Furthermore, the specific steps in step 4 are as follows:

[0052] 4.1) The second-order ordinary differential equations with n degrees of freedom, which are composed of the dynamic equations of the elastic and inelastic support subsystems, are transformed into first-order state equations by variable substitution. These state equations, together with the kinematic equations, the model expressions of the outrigger hydraulic cylinders, the axial forces of the outrigger connecting rods, the contact forces between the foot plate and the seabed, and the seawater forces, are compiled into an ODE file to be solved.

[0053] 4.2) Using the ODE45 solver of MATLAB, the fourth- to fifth-order Runge-Kutta algorithm with adaptive step size is adopted. After setting the solution time, the model is numerically solved. By setting the corresponding zero-crossing detection, the solution is judged in real time whether the deep-sea drilling rig has reached the boundary condition that will cause it to overturn. If it is judged that the deep-sea drilling rig will overturn, the solution is terminated in advance. Otherwise, the solution time is executed normally until the set solution time is completed.

[0054] 4.3) Further analysis and processing of the solution results are performed to obtain the motion trajectory of the deep-sea drilling rig during the hard landing process, the force on the legs of the deep-sea drilling rig, the magnitude of the transient acceleration of the center of mass of the deep-sea drilling rig, the sinking depth of the foot plates of the legs of the deep-sea drilling rig, and the deflection of the deep-sea drilling rig.

[0055] Compared with the prior art, the beneficial effects of the present invention are:

[0056] 1. This invention establishes a quasi-three-dimensional dynamic model of the hard landing of a deep-sea subsea drilling rig, which is closer to the actual situation of the drilling rig landing and is easy to solve.

[0057] 2. The numerical simulation output of this invention includes various important dynamic responses of the drilling rig during the hard landing process, including the force on the outriggers, the magnitude of the transient acceleration of the drilling rig's center of mass, the sinking depth of the outrigger footplates, and the deflection of the rig body. In addition to determining whether the drilling rig can successfully land under specified landing conditions, it can also be used to predict the ease of leveling the drilling rig body after successful landing.

[0058] 3. By adjusting the model parameters, this invention can meet the numerical simulation requirements for hard landing of deep-sea subsea drilling rigs of different specifications on seabeds of different properties using different landing control parameters. It can also be used to analyze the influence of factors such as landing control parameters and seabed mechanical parameters on the landing dynamic response of the drilling rig, and further provide theoretical basis and guidance for the optimized design of the support system of deep-sea subsea drilling rigs and the landing control of deep-sea subsea drilling rigs. Attached Figure Description

[0059] Figure 1 This is a 3D schematic diagram of a three-legged deep-sea subsea drilling rig.

[0060] Figure 2This is a simplified model diagram of a three-legged deep-sea subsea drilling rig; Figure 2 a is the main view of a simplified model of a three-legged deep-sea subsea drilling rig; Figure 2 b is a top view of a simplified model of a three-legged deep-sea subsea drilling rig.

[0061] Figure 3 This is a diagram of the equivalent spring-damping model of the axial force of the outriggers of a deep-sea subsea drilling rig. Figure 3 a is the equivalent spring-damping model of the axial force of the hydraulic cylinder of the outrigger of the deep-sea subsea drilling rig. Figure 3 b is the equivalent spring-damping model of the axial force of the outrigger connecting rod of the deep-sea subsea drilling rig.

[0062] Figure 4 It is the normal dynamic loading and unloading mechanical property curve of the seabed sediment in the drilling rig footplate-seabed contact force sub-model.

[0063] Figure 5 It is a motion trajectory diagram of the hard landing process of a three-legged deep-sea subsea drilling rig, obtained through numerical simulation. Detailed Implementation

[0064] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0065] Example

[0066] Taking the numerical simulation of the hard landing process of a three-legged deep-sea subsea drilling rig as an example.

[0067] This invention includes the following steps:

[0068] Step 1: Establish a dynamic model for the hard landing of the deep-sea subsea drilling rig.

[0069] like Figure 1 As shown, the deep-sea drilling rig consists of a body 1 and three sets of outriggers (outrigger 2, outrigger 3, and outrigger 4). The three sets of outriggers have identical structures and are symmetrically distributed. Each set of outriggers mainly consists of a foot plate 201, a universal joint 202, an outrigger connecting rod 203, and an outrigger hydraulic cylinder 204. One end of the outrigger hydraulic cylinder 204 and the outrigger connecting rod 203 is hinged to the foot plate 201 through the universal joint 202, denoted as hinge point J; the other end of the hydraulic cylinder 204 is hinged to the outrigger seat 101 on the body 1, denoted as hinge point M; the other end of the outrigger connecting rod 203 is also hinged to the outrigger seat 101, but there are two coaxial hinge points. When modeling, the midpoint N of the two actual hinge points is taken as the equivalent hinge point.

[0070] The process of establishing the dynamic model for the hard landing of a deep-sea subsea drilling rig is as follows:

[0071] 1.1) As Figure 2As shown, to accurately represent the real-world situation of a deep-sea drilling rig landing hard on the seabed and to better solve the computational problems, the deep-sea drilling rig is simplified into one elastic support subsystem and three non-elastic support subsystems (the number of non-elastic support subsystems corresponds to the number of outrigger groups). The elastic support subsystem consists of the upper mass supported by the outrigger hydraulic cylinders 204, specifically including the mass of the drilling rig body 1, the cylinder barrel of hydraulic cylinder 204 and related accessories, and half the mass of the outrigger connecting rod 203. Each non-elastic support subsystem consists of some components in a single outrigger group, specifically including the mass of the piston and piston rod of the outrigger hydraulic cylinder 204, the foot plate 201, the universal joint 202, and other components, as well as half the mass of the outrigger connecting rod 203. The non-elastic support subsystems in outriggers 2, 3, and 4 are respectively designated as non-elastic support subsystems I, II, and III.

[0072] The model makes the following assumptions:

[0073] 1.1.1) As Figure 2 As shown, the total mass m of the elastic support subsystem u The center of mass O of the drilling rig body 1 is concentrated in B At the landing point, the elastic support subsystem is located on the structural symmetry plane X of the deep-sea subsea drilling rig. B O B Y B It has two translational degrees of freedom and one orbital degree of freedom. B Z B The rotational degrees of freedom of the shaft; the mass m of each inelastic support subsystem f Concentrated at the universal joint 202 (i.e. hinge point J) of each outrigger, during the landing process, each inelastic support subsystem has two translational degrees of freedom in its respective outrigger plane MJN; the positional constraints and force transmission between the elastic support subsystem and the inelastic support subsystem are achieved through the geometric constraint relationship of the outrigger structure.

[0074] 1.1.2) The outrigger link 203 is equivalent to a rod with axial stiffness and damping, and which can transmit lateral force but cannot be bent in the lateral direction (referring to the direction perpendicular to the plane MJN where the outrigger is located, and the outrigger plane MJN refers to the plane that passes through the outrigger hydraulic cylinder and is parallel to the longitudinal axis of the deep-sea subsea drilling rig body); the outrigger hydraulic cylinder 204 plays the main role of buffering and absorbing energy, and is regarded as an elastic-damping element that is only subjected to axial force; apart from the outrigger hydraulic cylinder 204 and the outrigger link 203, the structural elasticity of the rest of the deep-sea subsea drilling rig is not considered.

[0075] 1.2) To facilitate the description and analysis of the various parts of the deep-sea subsea drilling rig, such as Figure 2 As shown, the model introduces a global coordinate system and multiple local coordinate systems, the definitions of which are as follows:

[0076] 1.2.1) Global coordinate system O I -X I Y I Z I The projection point O of the footplate 201 of outrigger 2 (or outrigger 3) onto the structural symmetry plane of the deep-sea drilling rig when the drilling rig first touches the bottom. I Let X be the origin of the coordinate system. I O I Y I The surface coincides with the structural symmetry plane of the deep-sea subsea drilling rig, O I X I The axis is positive when it is horizontal to the right, O I Y I The axis is vertically upward as positive, O I Z I The positive axis is determined by the right-hand screw rule;

[0077] 1.2.2) Body coordinate system O B -X B Y B Z B : Origin O B At the center of mass of the body 1, O B Y B The positive direction of the axis points upward along the axis of the body 1, O B X B The axis is within the structural symmetry plane of the deep-sea subsea drilling rig and intersects with O. B Y B The axis is perpendicular and points to the right, O B Z B The positive axis is determined by the right-hand screw rule;

[0078] 1.2.3) Leg coordinate system O S -X S Y S Z S : Origin O S The origin O of the body coordinate system B Coincidence, O S Y S Shaft and O B Y B The axes coincide, and they are circumscribed around O via the body coordinate system. B Y B The axis is rotated 60° counterclockwise to make the support leg 2 located at X. S O S Y S In the plane.

[0079] 1.3) Establish the dynamic and kinematic equations for the hard landing of the deep-sea subsea drilling rig, and derive the expression for the lateral force transmitted by the outrigger connecting rod 203. The specific operation is as follows:

[0080] 1.3.1) Due to the symmetrical structure of the three-legged deep-sea subsea drilling rig, and combined with model assumption 1.1.1), the established dynamic model of the hard landing of the deep-sea subsea drilling rig has 7 independent degrees of freedom. A suitable coordinate system is selected to establish the dynamic equations for each degree of freedom: In the global coordinate system, according to Newton's second law, the translational dynamic equations for the elastic support subsystem and the inelastic support subsystem III can be established; in the body coordinate system, according to the angular momentum theorem, the dynamic equations for the elastic support subsystem around O can be established. B Z B The rotational dynamics equation of the shaft; in the outrigger coordinate system, according to the theorem of acceleration composition, the translational dynamics equation of the inelastic support subsystem I can be established. For the geometric variables involved in the dynamics equations, such as the compression or extension strokes of the outrigger hydraulic cylinder 204 and the outrigger connecting rod 203, and the geometric angles between the outrigger hydraulic cylinder 204 and the outrigger connecting rod 203 and each coordinate plane, their kinematic equations can be established in the corresponding coordinate system through coordinate and inverse trigonometric function operations.

[0081] 1.3.2) Because the outrigger 4 of the three-legged deep-sea subsea drilling rig is located on the structural symmetry plane X of the drilling rig. B O B Y B Therefore, outrigger 4 is not subject to lateral forces, and because outriggers 2 and 3 are symmetrical about the drilling rig's structural plane X... B O B Y B Because of the symmetry, the force distribution on outriggers 2 and 3 is also symmetrical. Therefore, it is only necessary to derive the expression for the lateral force transmitted by the outrigger link 203 of outrigger 2. The specific steps are as follows:

[0082] Based on the translational dynamics equations of the inelastic support subsystem I in the outrigger coordinate system:

[0083]

[0084] Where: m f For the mass of inelastic support subsystem I, r f1 The displacement of the inelastic support subsystem I in the leg coordinate system [x] fS1 ,y fS1 ,z fS1 ] T , These are the velocity and acceleration of the inelastic support subsystem I in the outrigger coordinate system, F. sum The net external force acting on the inelastic support subsystem I is ω. S , These are the rotational angular velocity and angular acceleration of the leg coordinate system relative to the global coordinate system, respectively. Let z be the acceleration of the outrigger coordinate system origin relative to the global coordinate system origin. Combining this with model assumption 1.1.2) that "outrigger link 203 can transmit lateral forces but cannot bend," meaning the displacement of the inelastic support subsystem I along the outrigger 2 lateral direction is 0, we obtain z. fS1 =0, and then the expression for the lateral force transmitted by the leg link 203 of the outrigger 2 corresponding to the inelastic support subsystem I is derived.

[0085] 1.4) As Figure 3 As shown, the axial force sub-model of the outrigger is established, and the specific operation is as follows:

[0086] 1.4.1) Based on model assumption 1.1.2), the equivalent stiffness k of the outrigger hydraulic cylinder 204 is... p Represented as

[0087]

[0088] In the formula: k oil k is the equivalent stiffness coefficient of hydraulic oil. rod k is the piston rod stiffness coefficient. barrel This is the cylinder stiffness coefficient;

[0089] 1.4.2) Equivalent stiffness k of outrigger link 203 a The equivalent damping coefficient is calculated using the finite element method or from the equivalent cross-sectional dimensions and length, and is given by the following formula: Calculate, where ξ is the damping ratio, m a The mass of the outrigger connecting rod 203.

[0090] 1.5) Establish a contact force sub-model between footplate 201 and seabed sediment 5. The specific operation is as follows:

[0091] 1.5.1) The normal contact force F between foot plate 201 and substrate 5 n Considering the elastic support and energy dissipation effects of the deep seabed sediment 5, we obtain F. n =F ela +F dam F ela For the elastic force of substrate 5, F dam The damping force of substrate 5 is F; where the damping force of substrate 5 is F. dam Calculate using the following formula:

[0092]

[0093] In the formula: c sedi Let δ be the damping coefficient of the substrate 5, and δ be the damping coefficient of the substrate 5. These represent the sinking depth and sinking speed of footplate 201, respectively; and the elastic force F of substrate 5. elaConsidering the dynamic load-bearing capacity of the substrate 5 and the repeated loading and unloading of the footplate 201, such as... Figure 4 As shown in the figure, k1 and k2 are the dynamic compression equivalent elastic coefficient and rebound recovery equivalent elastic coefficient of the substrate 5 corresponding to the area of ​​foot plate 201, respectively, and δ1 is... The δ value at the first change of number is the maximum depth of the first sinking of foot plate 201. δ2 is the δ value corresponding to the irreversible plastic deformation of the substrate 5 caused by the first sinking of foot plate 201.

[0094] First time adding / uninstalling:

[0095]

[0096] The qth (q≥2) addition / unloading:

[0097]

[0098] 1.5.2) Calculate the horizontal friction force F between the footplate 201 and the substrate 5. f Considering the influence of relative slippage and sinking depth on friction, the coefficient of friction between the footplate 201 and the substrate 5, after correction for both sinking depth and relative slippage velocity, is: μ f =μ δ +μ k0 +(μ s0 -μ k0 )e -εv , where μ s0 and μ k0 These are the static and dynamic friction coefficients of the substrate 5, respectively, without considering the subsidence depth; ε is the exponential decay coefficient; v is the relative sliding velocity; and μ is the dynamic friction coefficient. δ Frictional gain caused by subsidence depth:

[0099]

[0100] In the formula: R is the radius of foot plate 201; the horizontal friction force between foot plate 201 and substrate 5 is: F f =μ f ·F n μ f The coefficient of friction between foot plate 201 and substrate 5.

[0101] 1.6) Establish a sub-model of seawater forces. The specific steps are as follows:

[0102] The forces exerted on the deep-sea drilling rig during its descent include three components: buoyancy, fluid resistance, and hydrodynamic force. Since the current velocity at the deep seabed is nearly zero, the forces exerted on the elastic support subsystem in the global coordinate system are approximately zero at point O. I X I Shaft and OI Y I The components on the axis are as follows:

[0103]

[0104] In the formula: x u , The elastic support subsystem is located in O I X I Displacement, velocity, and acceleration on the axis, y u , The elastic support subsystem is located in O I Y I Displacement, velocity, and acceleration along the axis, where ρ is the density of seawater, and C dx C dy The elastic support subsystem is located in O I X I Shaft and O I Y I The coefficient of water resistance in the axial direction, C mx C my The elastic support subsystem is located in O I X I Shaft and O I Y I Additional mass coefficient in the axial direction, S x S y The elastic support subsystem is located in O I X I Shaft and O I Y I Water-facing area in the axial direction, V u and F bu These represent the volume of the elastic support subsystem and the buoyancy it experiences; the seawater buoyancy can be calculated from the difference between the drilling rig's weight in air and its weight underwater.

[0105] Step 2: Set the parameters of the deep-sea drilling rig, the landing control parameters, and the mechanical properties of the seabed in the model. The specific operation is as follows:

[0106] 2.1) Based on the physical structure of the deep-sea subsea drilling rig, the parameters of the deep-sea subsea drilling rig in the model are set;

[0107] 2.2) The landing control parameters of the deep-sea subsea drilling rig include the outrigger deployment angle β (the angle between the outrigger connecting rod 203 and the bottom surface of the body 1) and the drilling rig release height H (the vertical distance between the drilling rig foot plate 201 and the seabed 5 before the rapid cable laying). Based on the sea trial and engineering application experience of the deep-sea subsea drilling rig, the landing control parameters are set as H = 3m and β = 20°.

[0108] 2.3) Set the bottom sediment mechanical parameter k1 = 1 × 10 6 N / m, k2=3k1, c sedi =1×10 4 N·s / m, μ s0 =0.25, μ k0 =0.8μ s0 .

[0109] Step 3: Determine the initial conditions for solving the dynamic model of the hard landing of the deep-sea subsea drilling rig. The specific operations are as follows:

[0110] 3.1) The initial position coordinates of the elastic and inelastic support subsystems when the drilling rig first touches the bottom are calculated from the structural dimensions of the deep-sea subsea drilling rig and the deployment angle β of the outriggers;

[0111] 3.2) Considering the deep-sea drilling rig as a whole, and simplifying its process from release to initial contact with the bottom as free fall, and assuming the seabed topography is flat, and that the footplates 201 of each leg of the deep-sea drilling rig contact the bottom simultaneously, the initial rotational angular velocity and horizontal velocity of the deep-sea drilling rig are both zero; the dynamic equation of the overall free fall process of the deep-sea drilling rig is:

[0112]

[0113] In the formula: y t , These represent the vertical displacement, velocity, and acceleration of the deep-sea subsea drilling rig, in meters. t S, V, F b These are the mass, vertical surface area facing the water, volume, and buoyancy force acting on the deep-sea subsea drilling rig, respectively. d C represents the water resistance coefficient of a deep-sea subsea drilling rig in the vertical direction. m Let y be the additional mass coefficient of the deep-sea subsea drilling rig in the vertical direction; solve the differential equation, and let y t0 =H, And in y t The solution is terminated when the value is 0, which gives the magnitude of the vertical velocity of the deep-sea drilling rig when it first touches the bottom.

[0114] Step 4: Perform numerical simulation of the hard landing process of the deep-sea drilling rig. The specific operation is as follows:

[0115] 4.1) The 7-DOF second-order ordinary differential equation system consisting of the dynamic equations of the elastic and inelastic support subsystems is transformed into a first-order state equation by variable substitution. This state equation, together with the kinematic equations, the axial forces of the outrigger hydraulic cylinder 204 and the outrigger connecting rod 203, the contact force between the foot plate 201 and the bottom material 5, the seawater force, etc., are compiled into an ODE file to be solved.

[0116] 4.2) Using the ODE45 solver of MATLAB, the fourth- to fifth-order Runge-Kutta algorithm with adaptive step size and a solution time of 3 seconds is used to solve the model numerically. By setting corresponding zero-crossing detection, the solution process is used to judge in real time whether the deep-sea drilling rig has reached the boundary condition that will cause it to overturn. If it is judged that the deep-sea drilling rig will overturn, the solution is terminated in advance; otherwise, the solution time is executed normally until the set solution time is completed.

[0117] 4.3) Further analysis and processing of the solution results yields the motion trajectory of the deep-sea drilling rig during its hard landing process, the force conditions of the rig's outriggers, and the center of mass O of the rig body 1. B The magnitude of transient acceleration, the sinking depth of the deep-sea drilling rig's outrigger footplate 201, and the deflection of the deep-sea drilling rig's body 1.

[0118] like Figure 5 The figure shows the motion trajectory of the three-legged deep-sea subsea drilling rig during the hard landing process obtained by numerical simulation. Combined with the other dynamic responses output by the simulation, it can be seen that under the above-mentioned landing conditions, the values ​​of all dynamic responses of the three-legged deep-sea subsea drilling rig during the landing process are within the design allowable range, and the entire landing process is relatively stable. This result is consistent with the actual situation, proving that the numerical simulation method is effective.

Claims

1. A numerical simulation method for the hard landing process of a deep-sea subsea drilling rig, characterized by comprising the following steps: Step 1: Establish a dynamic model for the hard landing of a deep-sea subsea drilling rig; Step 2: Set the parameters of the deep-sea subsea drilling rig, the landing control parameters, and the mechanical properties of the seabed in the model; Step 3: Determine the initial conditions for solving the dynamic model of hard landing of deep-sea subsea drilling rigs; Step 4: Perform numerical simulation of the hard landing process of the deep-sea drilling rig on the seabed; The specific steps for step 1 are as follows: 1.1) The deep-sea subsea drilling rig is simplified into one elastic support subsystem and N inelastic support subsystems, where N is the number of outriggers of the deep-sea subsea drilling rig; and the following assumptions are made about the model: 1.1.1) Total mass m of the elastic support subsystem u Concentrated at the center of mass of the deep-sea drilling rig, the elastic support subsystem possesses two translational degrees of freedom and one rotational degree of freedom within the structural symmetry plane of the deep-sea drilling rig during the landing process; the mass m of each inelastic support subsystem... f Concentrated at the connection between their respective foot plates and outriggers, each inelastic support subsystem has two translational degrees of freedom in its respective outrigger plane during landing; the elastic support subsystem and the inelastic support subsystem are connected by the geometric constraints of the outrigger structure to achieve positional constraints and force transmission. 1.1.2) The outrigger linkage is equivalent to a rod with axial stiffness and damping, which can transmit lateral force but cannot be bent; the outrigger hydraulic cylinder is regarded as an elastic-damped element that is only subjected to axial force; the structural elasticity of the rest of the deep-sea drilling rig is not considered except for the outrigger hydraulic cylinder and the outrigger linkage. 1.2) Introduce a global coordinate system, a body coordinate system, and a leg coordinate system into the model; 1.3) Establish the dynamic and kinematic equations for the hard landing of the deep-sea subsea drilling rig, and derive the expression for the lateral force transmitted by the outrigger connecting rod; 1.4) Establish the axial force sub-model of the outrigger; 1.5) Establish a foot-substrate contact force model; 1.6) Establish a sub-model of seawater forces; The specific steps for step 1.3) are as follows: 1.3.1) For the n independent degrees of freedom of the deep-sea drilling rig hard landing in the model, the dynamic equations of each degree of freedom are established in a suitable coordinate system using Newton's second law, the theorem of angular momentum and the theorem of composition of acceleration; for the geometric variables involved in the dynamic equations, the kinematic equations of the deep-sea drilling rig hard landing are established in the corresponding coordinate system through coordinate and inverse trigonometric function operations. 1.3.2) Derive the expression for the lateral force transmitted by each leg link. The specific steps are as follows: Based on the translational dynamics equations of any inelastic support subsystem in the selected outrigger coordinate system: ； In the formula, For the mass of the inelastic support subsystem, The displacement of the inelastic support subsystem in the selected leg coordinate system. , , ] T , , These represent the velocity and acceleration of the inelastic support subsystem in the selected outrigger coordinate system, respectively. The resultant external force acting on this inelastic support subsystem , These are the rotational angular velocity and angular acceleration of the selected leg coordinate system relative to the global coordinate system, respectively. Let be the acceleration of the selected outrigger coordinate system origin relative to the global coordinate system origin; then, combining this with model assumption 1.1.2) that "the outrigger link can transmit lateral force but cannot bend," i.e., the displacement of the inelastic support subsystem along the outrigger lateral direction is 0, we obtain... Then, the expression for the lateral force transmitted by the outrigger linkage corresponding to the inelastic support subsystem was derived.

2. The numerical simulation method for the hard landing process of a deep-sea subsea drilling rig according to claim 1, step 1.4) is specifically performed as follows: 1.4.1) Based on model assumption 1.1.2), the equivalent stiffness of the outrigger hydraulic cylinder Represented as: ； In the formula: This is the equivalent stiffness coefficient of the hydraulic oil. This is the piston rod stiffness coefficient. This is the cylinder stiffness coefficient; 1.4.2) Equivalent stiffness k of the outrigger link a The equivalent damping coefficient is calculated using the finite element method or from the equivalent cross-sectional dimensions and length, and is given by the following formula: Calculate, where: For the damping ratio, m a For the mass of the outrigger connecting rod.

3. The numerical simulation method for the hard landing process of a deep-sea subsea drilling rig according to claim 1, step 1.5) is specifically performed as follows: 1.5.1) For the normal contact force F between the foot and the substrate n Considering the elastic support and energy dissipation effects of the deep seabed, we obtain... F ela For the elastic force of the substrate, F dam The bottom damping force; among which, Substrate damping force F dam Calculate using the following formula: ； In the formula: The bottom mass damping coefficient is... and These represent the sinking depth and sinking speed of the foot, respectively. For the elastic force F of the substrate ela Considering the dynamic load-bearing capacity of the bottom sediment and the repeated loading and unloading of the footplate: First time adding / uninstalling: ； The qth (q≥2)th addition / unloading: ； In the formula: k1 and k2 are the equivalent elastic coefficients of dynamic compression and rebound recovery of the substrate corresponding to the foot area, respectively. for First change of number Value, that is, the maximum depth to which the foot first sinks. The irreversible plastic deformation of the substrate caused by the initial sinking of the foot. value; 1.5.2) Calculate the horizontal friction force between the footboard and the substrate. Considering the effects of relative slippage and sinking depth on friction, the coefficient of friction between the footboard and the substrate, after correction for both sinking depth and relative slippage velocity, is: ,in and These are the static friction coefficient and dynamic friction coefficient of the bottom sediment, respectively, without considering the subsidence depth. The exponential decay coefficient is... The relative sliding speed, Frictional gain caused by subsidence depth: ， In the formula: R is the radius of the footplate; the horizontal frictional force between the footplate and the substrate is: , It is the coefficient of friction between the foot and the substrate.

4. The numerical simulation method for the hard landing process of a deep-sea subsea drilling rig according to claim 1, the specific operation of step 1.6) is as follows: The forces exerted on the deep-sea drilling rig during its descent include three components: buoyancy, fluid resistance, and hydrodynamic force. Since the current velocity at the deep seabed is nearly zero, the forces exerted on the elastic support subsystem in the global coordinate system are approximately zero at point O. I X I Shaft and O I Y I The components on the axis are as follows: ； In the formula: , , The elastic support subsystem is located in O I X I Displacement, velocity, and acceleration on the axis , , The elastic support subsystem is located in O I Y I Displacement, velocity, and acceleration on the axis C is the density of seawater. dx C dy The elastic support subsystem is located in O I X I Shaft and O I Y I The coefficient of water resistance in the axial direction, C mx C my The elastic support subsystem is located in O I X I Shaft and O I Y I Additional mass coefficient in the axial direction, S x S y The elastic support subsystem is located in O I X I Shaft and O I Y I Water-facing area in the axial direction, V u and F bu These represent the volume and buoyancy of the elastic support subsystem, respectively; the seawater buoyancy is calculated from the difference between the weight of the deep-sea subsea drilling rig in air and its weight underwater.

5. The numerical simulation method for the hard landing process of a deep-sea subsea drilling rig according to claim 1, the specific operation of step 3 is as follows: 3.1) The initial position coordinates of the elastic and inelastic support subsystems when the deep-sea subsea drilling rig first touches the bottom are calculated from the structural dimensions of the deep-sea subsea drilling rig and the deployment angle of the outriggers; 3.2) Considering the deep-sea drilling rig as a single unit, and simplifying its process from release to initial contact with the bottom as free fall, and assuming a flat seabed topography and simultaneous contact with the bottom by all legs of the deep-sea drilling rig, the initial rotational angular velocity and horizontal velocity of the deep-sea drilling rig are both zero; the dynamic equations of the free fall process of the deep-sea drilling rig are: ； In the formula: , , These are the vertical displacement, velocity, and acceleration of the deep-sea drilling rig. S, V, F b These are the mass, vertical surface area facing the water, volume, and buoyancy force experienced by the deep-sea subsea drilling rig, respectively. d C represents the water resistance coefficient of a deep-sea subsea drilling rig in the vertical direction. m Let be the additional mass coefficient of the deep-sea subsea drilling rig in the vertical direction; solve the differential equation, and let H is the release height from the bottom. and in The solution is terminated when the deep-sea drilling rig first touches the bottom, thus obtaining the magnitude of its vertical velocity.

6. The numerical simulation method for the hard landing process of a deep-sea subsea drilling rig according to claim 1, the specific operation of step 4 is as follows: 4.1) The second-order ordinary differential equations with n degrees of freedom, which are composed of the dynamic equations of the elastic and inelastic support subsystems, are transformed into first-order state equations by variable substitution. These state equations, together with the kinematic equations, the axial forces of the outrigger hydraulic cylinders and outrigger connecting rods, the contact forces between the foot plate and the seabed, and the seawater forces, are compiled into an ODE file to be solved. 4.2) Using the ODE45 solver of MATLAB, the fourth- to fifth-order Runge-Kutta algorithm with adaptive step size is adopted. After setting the solution time, the model is numerically solved. By setting the corresponding zero-crossing detection, the solution is judged in real time whether the deep-sea drilling rig has reached the boundary condition that will cause it to overturn. If it is judged that the deep-sea drilling rig will overturn, the solution is terminated in advance. Otherwise, the solution time is executed normally until the set solution time is completed. 4.3) Further analysis and processing of the solution results are performed to obtain the motion trajectory of the deep-sea drilling rig during the hard landing process, the force on the legs of the deep-sea drilling rig, the magnitude of the transient acceleration of the center of mass of the deep-sea drilling rig, the sinking depth of the foot plates of the legs of the deep-sea drilling rig, and the deflection of the deep-sea drilling rig.

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