A method for optimizing the suspension point speed of a pumping unit based on directional wells

Abstract

The present invention provides a method for optimizing the suspension point speed of a pumping unit based on a directional well, comprising: step one: importing the three-dimensional borehole data and sucker rod data, pumping parameters and reservoir parameters of the oil well; step two: establishing a finite element model and equilibrium equation of the sucker rod; step three: analyzing the fatigue life of the sucker rod; step four: constructing the suspension point speed with Fourier series; step five: determining the design variables, constraints and objective functions, and establishing a mathematical model for the real-time suspension point speed optimization design; step six: using a genetic algorithm to optimize the mathematical model in step five to obtain the optimal solution for the suspension point speed. The present invention achieves the purpose of reducing the eccentric wear of the sucker rod and thus extending the pump inspection cycle by changing the suspension point speed of the pumping unit without changing the existing pumping parameters, sucker rod column combination and number of centralizers of the oil well, thereby saving operating costs and improving development benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production, and in particular relates to a method for optimizing the suspension point speed of an oil pump based on a directional well. Background Art

[0002] The actual wellbore trajectory of directional wells in the petroleum industry is an irregular three-dimensional spatial curve with complex spatial characteristics. The mechanical behavior of the sucker rod string in a directional well is very different from that in a conventional vertical well. This is mainly due to the changes in the curvature and torsion of the wellbore trajectory, which causes the sucker rod string with an ultra-slenderness ratio to be subjected to axial tension, compression and bending during reciprocating motion downhole, and exhibit typical instability characteristics during the downstroke, which indirectly causes the increasingly serious problems of eccentric wear and breakage of the sucker rod string.

[0003] The reason why the sucker rod suffers fatigue fracture is that the sucker rod is subjected to alternating loads during the up and down strokes.

[0004] There are two main reasons for the eccentric wear of the sucker rod: (1) When the pumping well is working normally, the force conditions of the sucker rod string in the upstroke and downstroke are different. During the upstroke, the entire sucker rod is in a tensile state, and the rod string is basically straight; during the downstroke, the sucker rod is mainly subjected to forces in the up and down directions, one is the downward gravity of its own, and the other is the downward resistance of the piston and the sucker rod. The resistance is in the upward direction, causing the lower sucker rod to produce a spiral bend. In this way, during the up and down reciprocating motion of the sucker rod, the upper and lower forces of the rod string are inconsistent. During the downstroke, a force neutralization point is formed on the sucker rod string. The rod string above the neutralization point is subjected to a tensile force, and the rod string below the neutralization point is subjected to a compressive force. The part of the rod string that is compressed during the downstroke will bend and deform, and eccentric wear will occur with the oil pipe. (2) For inclined wells or horizontal wells, there is a certain inclination angle in the wellbore structure. If the pump is lowered below the inclination point, the tubing above the pump will bend with the casing. During production, the combined tension or pressure of the sucker rod will generate a lateral component, causing eccentric wear of the tubing and the sucker rod. The larger the angle of the bending section or the inclination point, the more severe the wear between the sucker rod and the tubing. This wear occurs throughout the entire process of the upper and lower strokes of the sucker rod, and the wear is more severe. Even for vertical wells, current drilling technology makes it difficult to ensure that the wellbore is completely vertical, so the casing will bend at a certain section, and the tubing that is subsequently lowered will also bend with the casing. When the bending section appears above the pump hanger, the sucker rod will reciprocate up and down in the tubing, which will also cause friction between the pipe and the rod.

[0005] During the downstroke, the sucker rod string is compressed and bent. In order to reduce or avoid this compression bending, a weight rod is generally added to the lower end of the sucker rod string to improve the working condition of the sucker rod string and increase the working life of the sucker rod. However, an overly long weight rod not only increases the cost, but also increases the gravity of the rod string and the power consumption of pumping oil. The centralizer can effectively prevent failure caused by eccentric wear of the sucker rod and the oil pipe, but too many centralizers not only increase the resistance of the plunger to move up and down, but also increase the mining cost.

[0006] The existing optimization schemes for the suspension point speed of the pumping unit generally only consider the energy-saving control of the pumping unit, but do not consider the impact of the suspension point speed on the fatigue life of the sucker rod and the eccentric wear of the sucker rod. Summary of the invention

[0007] In order to solve the problem of short pump inspection cycle caused by fatigue damage and eccentric wear of sucker rods, the present invention provides a method for finding the optimal operating speed of the suspension point without changing the pumping parameters, the sucker rod column combination and the number of stabilizers, so as to achieve the purpose of reducing eccentric wear of the pipe and rod, increasing the fatigue life of the sucker rod, and then extending the pump inspection cycle, thereby saving operating costs and improving development benefits.

[0008] The embodiment of the present application provides a method for optimizing the suspension point speed of a pumping unit based on a directional well, comprising:

[0009] Step 1: Import the 3D wellbore data and sucker rod data, pumping parameters and reservoir parameters of the oil well;

[0010] Step 2: Establish the finite element model and equilibrium equation of the sucker rod;

[0011] Step 3: Analyze the fatigue life of the sucker rod;

[0012] Step 4: Construct the suspension point velocity using Fourier series;

[0013] Step 5: Determine the design variables, constraints and objective functions, and establish a mathematical model for real-time suspension point speed optimization design;

[0014] Step 6: Use genetic algorithm to optimize the mathematical model in step 5 to obtain the optimal solution of suspension point speed, and form the regular curve into a CNC frequency conversion program for oil well production.

[0015] Among them, step 2: establish the finite element model and equilibrium equation of the sucker rod, including:

[0016] The sucker rod is divided into a finite number of spatial beam elements. The force matrix of the node end of the spatial beam element is: The corresponding nodal displacement matrix is

[0017]

[0018]

[0019] In the step 2, each spatial beam unit has tensile, compressive, bending and torsional stiffness. According to the minimum potential energy principle, the equilibrium equation of each spatial beam unit can be derived:

[0020]

[0021] After the unit stiffness matrix of all units is obtained in step 2, the local coordinates of the units are transformed into the global coordinates, and then superimposed according to the principle of matching numbers, so as to establish the stiffness matrix of the overall structure; according to the same idea, the node load or displacement of each unit is obtained, converted to the global coordinates, and then superimposed to form the node load of the entire structure, and the overall balance equation of the sucker rod can be established:

[0022] {F}=[K]{δ}

[0023] Where: F x 、F y 、F z ——node load; M x 、M y 、M z ——torque in corresponding direction; u x ,v y ,w z ——Displacement of the node in the x, y, and z directions; θ x ,θ y ,θ z ——Rotation angle of the node around the x, y, and z axes; {F}——Total node load of the sucker rod in global coordinates; [K]——Total stiffness matrix of the sucker rod in global coordinates; {δ}——Total node displacement array of the sucker rod in global coordinates.

[0024] Wherein, the step 3 of analyzing the fatigue life of the sucker rod comprises:

[0025] The calculation model of the fatigue life of the rod section is established using the material σ-N curve. The expression of any number of cycles N within the limited life range of the sucker rod is:

[0026] N=N0σ r / (σ a ) ε

[0027] In the formula: N0——cycle base, N0=10 7 times; r ——Fatigue limit with stress ratio r, MPa; (σ a ) ε ——Equivalent stress amplitude, MPa.

[0028] Among them, the fatigue life of the sucker rod is the life of the finite life fatigue stage.

[0029] The equation for the suspension point velocity constructed by Fourier series in step 4 is as follows:

[0030]

[0031] in:

[0032]

[0033]

[0034]

[0035] Where: n is the Fourier series; T is the period, s; ​​l is the length of 0.5 period, s.

[0036] Among them, in the step 5, the Fourier coefficient of the suspension point speed is used as the design variable, the pump efficiency, the life of the sucker rod, the neutral point height, and the working stress of the sucker rod are used as the constraints, and the pump inspection cycle is used as the objective function. The implementation method of establishing the mathematical model of the real-time suspension point speed optimization design is as follows;

[0037] By selecting different k, a0, a1, b1…a N 、b N The value of v(t) can have different curve forms; the optimization problem of v(t) is to solve a set of optimal a0, a1, b1…a N 、b N , so that the optimization target under the constraints reaches the maximum value, that is, the design variable X is:

[0038] X={a0,a1,b1,a2,b2...a k ,b k}(k=1,2,3...N)

[0039] The objective function pump inspection cycle is:

[0040] T max =max[v(a0, a1...a N ; b1, b2...b N )].

[0041] Among them, in the step 5, the constraints are set to provide a feasible solution domain for the optimization strategy, and the constraints are:

[0042]

[0043] Where: η v , ηo are the pump efficiencies before and after optimization; N f0 、N f1 are respectively the fatigue life of the sucker rod before and after optimization; L 中1 , L 中2 are the distances between the neutral point and the wellhead before and after optimization, m; σ max , [σ max ] are the maximum working stress of the sucker rod after optimization and the maximum allowable working stress of the sucker rod, respectively.

[0044] Among them, the steps of using genetic algorithm to optimize the mathematical model in step five in step six include: encoding, generating the first generation population, global search, calculating fitness, judging whether the optimization criteria are met, if so, outputting the optimal individual, if not, selecting, crossover, mutation, local search, generating a new generation population, and then returning to the step of calculating fitness.

[0045] The method for optimizing the suspension point speed of the pumping unit based on a directional well in the embodiment of the present application has the following beneficial effects:

[0046] The present application is based on a method for optimizing the suspension point speed of a pumping unit in a directional well, comprising: step one: importing the three-dimensional borehole data and sucker rod data, pumping parameters and reservoir parameters of the oil well; step two: establishing a finite element model and equilibrium equation of the sucker rod; step three: analyzing the fatigue life of the sucker rod; step four: constructing the suspension point speed using Fourier series; step five: determining the design variables, constraints and objective functions, and establishing a mathematical model for the real-time suspension point speed optimization design; step six: using a genetic algorithm to optimize the mathematical model in step five, obtaining the optimal solution for the suspension point speed, and forming a numerical control frequency conversion program with the regular curve for oil well production. The present invention achieves the purpose of reducing the eccentric wear of the sucker rod and thus extending the pump inspection cycle by changing the suspension point speed of the pumping unit without changing the existing pumping parameters, sucker rod column combination and number of stabilizers of the oil well, thereby saving operating costs and improving development benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the flow chart of the method for optimizing the suspension point speed of a pumping unit based on a directional well according to an embodiment of the present application;

[0048] Figure 2 Another schematic diagram of the process of optimizing the suspension point speed of a pumping unit based on a directional well according to an embodiment of the present application;

[0049] Figure 3 A schematic diagram of a genetic algorithm program used in the present invention;

[0050] Figure 4 is the wellbore trajectory of a well in the example;

[0051] Figure 5Comparison of suspension point velocity curves before and after optimization in the example;

[0052] Figure 6 Comparison of the acceleration curves of the suspension point before and after optimization in the example. DETAILED DESCRIPTION

[0053] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0054] In the following introduction, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The following introduction provides multiple embodiments of the present invention, and different embodiments can be replaced or combined, so this application can also be considered to include all possible combinations of the same and / or different embodiments recorded. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more of all other possible combinations of A, B, C, and D, even though the embodiment may not be clearly recorded in the following text.

[0055] The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Changes may be made to the functions and arrangements of the elements described without departing from the scope of the present application. Various processes or components may be appropriately omitted, substituted or added to each example. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted or combined. In addition, features described in some examples may be combined in other examples.

[0056] Embodiment 1

[0057] The present invention relates to a method for optimizing the suspension point speed of a pumping unit based on a directional well, comprising: step (1): importing the three-dimensional borehole data and pumping rod data, pumping parameters and reservoir parameters of the oil well; step (2): establishing a finite element model and equilibrium equation of the pumping rod; step (3): establishing a fatigue life model of the pumping rod; step (4): constructing the suspension point speed using Fourier series; step (5): determining design variables, constraints and objective functions, and establishing a mathematical model for optimizing the suspension point speed in real time; and step (6): using a genetic algorithm to optimize the mathematical model in step five, obtaining the optimal solution for the suspension point speed, and converting the regular curve into a numerical control frequency conversion program for use in oil well production.

[0058] The present invention achieves the purpose of reducing eccentric wear of the sucker rod and thus prolonging the pump inspection cycle by changing the suspension point speed of the pumping unit without changing the existing pumping parameters, sucker rod column combination and the number of centralizers of the oil well, thereby saving operating costs and improving development benefits.

[0059] Embodiment 2

[0060] like Figure 1 As shown, the present application is based on the method for optimizing the suspension point speed of the pumping unit of a directional well, which includes the following steps: S101: importing the three-dimensional wellbore data and sucker rod data, pumping parameters and reservoir parameters of the oil well; S102: establishing a finite element model and equilibrium equation of the sucker rod; S103: analyzing the fatigue life of the sucker rod; S104: constructing the suspension point speed by Fourier series; S105: determining the design variables, constraints and objective functions, and establishing a mathematical model for the real-time suspension point speed optimization design; S106: using a genetic algorithm to optimize the mathematical model in step five, obtain the optimal solution for the suspension point speed, and form a numerical control frequency conversion program with the regular curve for oil well production.

[0061] The method for establishing the finite element model and the equilibrium equation of the sucker rod in step S102 is as follows:

[0062] The sucker rod is divided into a finite number of spatial beam elements. The force matrix of the node end of the spatial beam element is: The corresponding nodal displacement matrix is

[0063]

[0064]

[0065] In step S102, each spatial beam unit has tensile, compressive, bending and torsional stiffness. According to the minimum potential energy principle, the equilibrium equation of each spatial beam unit can be derived:

[0066]

[0067] After the unit stiffness matrix of all units is obtained in step S102, the local coordinates of the units are transformed into the global coordinates, and then superimposed according to the principle of matching numbers, so as to establish the stiffness matrix of the overall structure. According to the same idea, the node load or displacement of each unit is obtained, converted to the global coordinates, and then superimposed to form the node load of the entire structure, and then the overall balance equation of the sucker rod can be established:

[0068] {F}=[K]{δ}

[0069] Where: F x 、F y 、F z ——node load; M x 、M y 、M z ——torque in corresponding direction; u x ,v y ,w z ——Displacement of the node in the x, y, and z directions; θ x,θ y ,θ z ——Rotation angle of the node around the x, y, and z axes; {F}——Total node load of the sucker rod in global coordinates; [K]——Total stiffness matrix of the sucker rod in global coordinates; {δ}——Total node displacement array of the sucker rod in global coordinates.

[0070] The method for analyzing the fatigue life of the sucker rod in step S103 is:

[0071] The calculation model of the fatigue life of the rod section is established by using the material σ-N curve. The fatigue life of the sucker rod calculated by the present invention is the life of the limited life fatigue stage. The expression of any cycle number N within the limited life interval of the sucker rod is:

[0072] N=N0σ r / (σ a ) ε

[0073] In the formula: N0——cycle base, N0=10 7 times; r ——Fatigue limit with stress ratio r, MPa; (σ a ) ε ——Equivalent stress amplitude, MPa.

[0074] The equation for the suspension point velocity constructed by Fourier series in step 4 is as follows:

[0075]

[0076] in:

[0077]

[0078]

[0079]

[0080] Where: n is the Fourier series; T is the period, s; ​​l is the length of 0.5 period, s.

[0081] In step S105, the Fourier coefficient of the suspension point speed is used as the design variable, the pump efficiency, the life of the sucker rod, the neutral point height, and the working stress of the sucker rod are used as the constraint conditions, and the pump inspection cycle is used as the objective function. The implementation method of establishing the mathematical model of the real-time suspension point speed optimization design is as follows;

[0082] By selecting different k, a0, a1, b1…a N 、b N For the value of v(t), v(t) can have different curve forms. To solve the optimization problem of v(t), we need to solve a set of optimal a0, a1, b1…aN 、b N , so that the optimization target under the constraints reaches the maximum value, that is, the design variable X is:

[0083] X={a0,a1,b1,a2,b2...a k ,b k}(k=1,2,3...N)

[0084] In step S105, the length of the eccentric wear section is shortened by optimizing the suspension point rate, and the fatigue life of the sucker rod is increased, thereby achieving the purpose of extending the pump inspection cycle. That is, the objective function pump inspection cycle is:

[0085] T max =max[v(a0, a1...a N ; b1, b2...b N )]

[0086] In step S105, in order to prevent the occurrence of accidents such as reduced oil well production and pumping rod breakage, it is necessary to set constraints to provide a feasible solution domain for the optimization strategy. The constraints of the present invention are:

[0087]

[0088] Where: η v , η o are the pump efficiencies before and after optimization; N f0 、N f1 are respectively the fatigue life of the sucker rod before and after optimization; L 中1 , L 中2 are the distances between the neutral point and the wellhead before and after optimization, m; σ max , [σ max ] are the maximum working stress of the sucker rod after optimization and the maximum allowable working stress of the sucker rod, respectively.

[0089] like Figure 3 As shown, in step S106, a genetic algorithm is used to optimize the mathematical model in step S105.

[0090] The present invention relates to a method for optimizing the suspension point speed of a pumping unit based on a directional well. Compared with the prior art, the method for optimizing the suspension point speed of a pumping unit based on a directional well provided by the present invention can reduce the eccentric wear of the pumping rod and extend the pump inspection cycle by changing the suspension point speed of the pumping unit without changing the existing pumping parameters, pumping rod column combination and the number of centralizers of the oil well, thereby saving operating costs and improving development benefits.

[0091] Embodiment 3

[0092] like Figure 2As shown, taking Well XX as an example, the pumping unit model is CYJ10-3-37HB; rod column combination parameters are 22mm 925m; stroke is 3m; stroke frequency is 6 times / min. The reservoir and wellbore parameters of the well are shown in Table 1:

[0093] Table 1 Reservoir and wellbore parameters

[0094]

[0095]

[0096] Attached Figure 4 This is a schematic diagram of the wellbore trajectory of the well. According to the wellbore trajectory curve and related inclination data, the oil well consists of a vertical well section, a curved well section and an inclined well section, of which the inclination angle of the inclined well section is about 30°. The maximum east-west deviation of the oil well is 197.2m, the maximum north-south deviation is 124.3m, and the maximum vertical depth is 936m.

[0097] The conventional suspension point speed used in this well is as follows:

[0098]

[0099] Step 1: Record reservoir parameters, wellbore parameters, and wellbore parameters.

[0100] Step 2: Perform finite element division on the sucker rod according to the above parameters and establish the equilibrium equation:

[0101] {F}=[K]{δ}

[0102] in:

[0103] {F}=[F x1 ,F y1 ,F z1 ,M x1 ,M y1 ,M z1 ,F x2 ,F y2 ,F z2 ,M x2 ,M y2 ,M z2 ,...

[0104] F xi ,F yi ,F zi ,M xi ,M yi ,M zi ,F xi+1 ,F yi+1 ,F zi+1 ,M xi+1 ,M yi+1 ,Mzi+1 ] T

[0105] {δ}=[u x1 ,v y1 ,w z1 ,θ x1 ,θ y1 ,θ z1 ,u x2 ,v y2 ,w z2 ,θ x2 ,θ y2 ,θ z2 ,...

[0106] u xi ,v yi ,w zi ,θ xi ,θ yi ,θ zi ,u xi+1 ,v yi+1 ,w zi+1 ,θ xi+1 ,θ yi+1 ,θ zi+1 ] T

[0107] Step 3: Analyze the limited fatigue life of the sucker rod:

[0108] N=N0σ r / (σ a ) ε

[0109] in:

[0110] σ r ={f+(1-f)[(1+r) / 2] n}σ b

[0111] n=1 / cf

[0112]

[0113] Where: f is the fatigue ratio of the material; c is the coefficient to be determined, for the structural steel unnotched specimen c = 1.66, for the structural steel notched specimen c = 2.16; K σ ——stress concentration factor; ε σ ——Size coefficient; β——Surface state coefficient; σ a ——stress amplitude, MPa; ——sensitivity coefficient; σ m ——Average stress, MPa.

[0114] Step 4: Construct the suspension point velocity using the fourth-order Fourier series:

[0115]

[0116] Step 5: Taking the Fourier coefficient of suspension point velocity as the design variable, pump efficiency, sucker rod life, neutral point height, sucker rod working stress as constraints, and pump inspection cycle as the objective function, a mathematical model for real-time suspension point velocity optimization design is established.

[0117] Step 6: Genetic algorithm is used to optimize the mathematical model in step 5, and the optimal solution of suspension point speed is obtained as follows:

[0118] v(t)=0.965sin(πt / 5)-0.059cos(πt / 5)+0.015sin(2πt / 5)-0.001cos(2πt / 5 )-0.069sin(3πt / 5)+-0.059cos(3πt / 5)-0.004sin(4πt / 5)+0.001cos(4πt / 5)

[0119] Compare the suspension point speed before and after optimization, and draw the suspension point speed curve and suspension point acceleration curve as shown in the attached figure. Figure 5 and attached Figure 6 The slower suspension point movement speed at the beginning of the up and down strokes and at the end of the up and down strokes can effectively reduce the leakage of the oil pump. Figure 6 The optimized suspension point speed v(t) is slow at the beginning of the up and down strokes, but is almost equal to the speed v0(t) before optimization at the end of the up and down strokes. Therefore, the optimized suspension point speed can effectively reduce the pump leakage.

[0120] Comparing the data before and after optimization, the pump efficiency was improved by 0.37%, the maximum stress amplitude of the sucker rod was reduced by 4.85%, the life of the sucker rod was increased by 9.27%, the neutral point height was reduced by 8.53%, and the maximum load of the suspension point was reduced by 1.08%.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing the suspension point speed of a pumping unit based on a directional well, characterized in that: include: Step 1: Import the 3D wellbore data and sucker rod data, pumping parameters and reservoir parameters of the oil well; Step 2: Establish the finite element model and equilibrium equation of the sucker rod; Step 3: Analyze the fatigue life of the sucker rod; Step 4: Construct the suspension point velocity using Fourier series; the equation for constructing the suspension point velocity using Fourier series is as follows: in: Where: n——Fourier series; T——period, s; ​​l——0.5 period length, s; Step 5: Determine the design variables, constraints and objective functions, and establish a mathematical model for optimizing the real-time suspension point speed. The implementation method for establishing the mathematical model for optimizing the real-time suspension point speed is as follows, with the Fourier coefficient of the suspension point speed as the design variable, the pump efficiency, the life of the sucker rod, the neutral point height, and the working stress of the sucker rod as the constraints, and the pump inspection cycle as the objective function; By selecting different k, a0, a1, b1…a N , b N The value of v(t) can have different curve forms; the optimization problem of v(t) is to solve a set of optimal a0, a1, b1…a N , b N , so that the optimization target under the constraints reaches the maximum value, that is, the design variable X is: X={a0,a1,b1,a2,b2...a k ,b k }(k=1,2,3...N) The objective function pump inspection cycle is: T max =max[v(a0、a1...a N ;b1、b2...b N )]; Setting constraints provides a feasible solution domain for the optimization strategy. The constraints are: Where: η v , η o are the pump efficiencies before and after optimization; N f0 、N f1 are respectively the fatigue life of the sucker rod before and after optimization; L 中1 , L 中2 are the distances between the neutral point and the wellhead before and after optimization, m; σ max , [σ max ] are the maximum working stress of the sucker rod after optimization and the maximum allowable working stress of the sucker rod respectively; Step 6: Use genetic algorithm to optimize the mathematical model in step 5 to obtain the optimal solution of suspension point speed, and form the regular curve into a CNC frequency conversion program for oil well production.

2. The method for optimizing the suspension point speed of a pumping unit based on a directional well according to claim 1 is characterized in that: Step 2: Establish the finite element model and equilibrium equation of the sucker rod, including: The sucker rod is divided into a finite number of spatial beam elements. The force matrix of the node end of the spatial beam element is: The corresponding nodal displacement matrix is In the step 2, each spatial beam unit has tensile, compressive, bending and torsional stiffness. According to the minimum potential energy principle, the equilibrium equation of each spatial beam unit can be derived: After the unit stiffness matrix of all units is obtained in step 2, the local coordinates of the units are transformed into the global coordinates, and then superimposed according to the principle of matching numbers, so as to establish the stiffness matrix of the overall structure; according to the same idea, the node load or displacement of each unit is obtained, converted to the global coordinates, and then superimposed to form the node load of the entire structure, and the overall balance equation of the sucker rod can be established: {F}=[K]{δ} Where: F x 、F y 、F z ——node load; M x 、M y 、M z ——torque in corresponding direction; u x ,v y ,w z ——Displacement of the node in the x, y, and z directions; θ x ,θ y ,θ z ——Rotation angle of the node around the x, y, and z axes; {F}——Total node load of the sucker rod in global coordinates; [K]——Total stiffness matrix of the sucker rod in global coordinates; {δ}——Total node displacement array of the sucker rod in global coordinates.

3. The method for optimizing the suspension point speed of a pumping unit based on a directional well according to claim 1 is characterized in that: The step 3 of analyzing the fatigue life of the sucker rod includes: The calculation model of the fatigue life of the rod section is established using the material σ-N curve. The expression of any number of cycles N within the limited life range of the sucker rod is: N=N0σ r / (s a ) ε In the formula: N0——cycle base, N0=10 7 times; r ——Fatigue limit with stress ratio r, MPa; (σ a ) ε ——Equivalent stress amplitude, MPa.

4. The method for optimizing the suspension point speed of a pumping unit based on a directional well according to claim 3 is characterized in that: The fatigue life of the sucker rod is the life in the finite life fatigue stage.

5. The method for optimizing the suspension point speed of a pumping unit based on a directional well according to any one of claims 1 to 4, characterized in that: The steps of optimizing the mathematical model in step five by using a genetic algorithm in step six include: encoding, generating an initial population, global search, calculating fitness, determining whether the optimization criteria are met, if so, outputting the optimal individual, if not, selecting, crossing, mutating, locally searching, generating a new generation population, and then returning to the step of calculating fitness.

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