A method for determining the optimal pumping rate of a beam pumping unit

Abstract

The present invention provides a method for determining the optimal pumping rate of a beam pumping unit, including determining the inflow characteristic curve; determining the outflow characteristic curve; plotting the oil well supply and discharge coordination diagram according to the inflow characteristic curve and the outflow characteristic curve; calculating the dynamic liquid level depth; calculating the reasonable submergence degree; expressing the plunger motion equation of the oil pump in the form of a Fourier series expansion; calculating the pump chamber volume between the plunger and the fixed valve; calculating the liquid volume in the pump chamber; calculating the pump filling coefficient by combining the pump chamber volume and the liquid volume in the pump chamber; determining the constraint conditions; calculating the optimal coefficients of each term of the Fourier series expansion; determining the optimized plunger motion equation of the oil pump; and back-calculating the polished rod motion equation and the motor motion rate from the plunger motion equation of the oil pump. Without reducing the service life of the pumping system, the present invention improves the pump efficiency, the pumping efficiency, and reduces the pumping consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil production, and specifically relates to a method for determining the optimal pumping rate of a beam pumping unit based on downhole comprehensive working conditions. Background Art

[0002] The beam pumping unit has the advantages of simple geometric structure, reliable quality, etc., and thus plays a quite important role in the mechanical oil production of oil fields. Up to now, in the oil field production in China, mechanical oil production wells account for 98% of all oil wells, and among them, beam pumping unit wells account for 96% of all mechanical oil production wells. With the continuous development of oil fields, the liquid supply capacity of the formation continuously decreases, the liquid production of oil wells gradually reduces, and problems such as low efficiency of the oil production system and high energy consumption become increasingly prominent, seriously restricting the economic and efficient development of oil fields. Therefore, energy conservation and consumption reduction work becomes even more important. The pumping unit is the main part of the energy consumption in oil fields and is also the key object of energy conservation and consumption reduction management work.

[0003] Due to some inherent characteristics of the beam pumping unit, when the traditional beam pumping unit works, according to the set pumping unit strokes per minute, the motor speed is then adjusted to a constant value for oil production construction. As a result, the crank of the pumping unit makes a uniform circular motion, and the speed regulation mode is basically fixed. When the equipment is determined, the operating frequency and speed of the motor are also determined accordingly. However, when the pumping unit runs at a constant speed, the uniform circular rotation of the crank will cause the running speed distribution of the pump plunger to be uneven, with large speed peaks, resulting in low efficiency of the sucker rod pump. In individual intermittent oil wells, due to serious insufficient liquid supply, the phenomenon of motor burnout often occurs, which further aggravates the disharmony between the supply and production relationship in the oil layer, greatly reducing the system efficiency of the pumping unit, increasing the energy consumption of the pumping unit and equipment loss. Existing patents adopt variable speed drive of the motor. On the basis of adjusting the strokes per minute by the frequency converter, through optimizing the operation control, the motor actively changes speed to change the pumping frequency and the speed distribution of the plunger during the pumping process, thereby reducing the fatigue load of the surface drive system and the entire rod string. The pumping unit is a complex system composed of machine, rod, and pump. The energy-saving effect not only depends on the motor and the system itself, but also on the comprehensive working conditions of the oil well and the production status. However, such patents still only start from the pumping unit motor and the polished rod, without considering the actual physical properties of the oil layer fluid and the structure of the sucker rod pump, and do not fundamentally solve the problem of low pumping efficiency, and it is difficult to achieve the "one well, one policy" adjustment of the running stroke speed of the pumping unit well, control the motor speed to achieve the "demand output" of the pumping unit well operation, and it is difficult to realize the coordination of pump supply and discharge, and control the occurrence of "water hammer" and insufficient liquid supply phenomena. Summary of the Invention

[0004] To solve the problem of the mismatch between the movement law of the plunger of the oil pump and the working conditions of the oil well, and to improve the oil production efficiency of the pumping unit wells, the present invention proposes a method for determining the optimal pumping rate of the beam pumping unit based on the downhole comprehensive working conditions, so as to determine a reasonable supply and discharge relationship, optimize the plunger movement speed, and improve the pump efficiency; optimize the polished rod acceleration and reduce the inertial load; realize the adjustment of the running stroke speed of the pumping unit well according to the specific conditions of each well.

[0005] The embodiment of the present application provides a method for determining the optimal pumping rate of a beam pumping unit, including:

[0006] Determine the inflow characteristic curve;

[0007] Determine the outflow characteristic curve;

[0008] Draw a supply and discharge coordination diagram of the oil well according to the inflow characteristic curve and the outflow characteristic curve;

[0009] Calculate the dynamic liquid level depth;

[0010] Calculate the reasonable submergence depth;

[0011] Represent the plunger movement equation of the oil pump in the form of a Fourier series expansion;

[0012] Calculate the pump chamber volume between the plunger and the fixed valve;

[0013] Calculate the volume of the liquid in the pump chamber;

[0014] Calculate the pump filling coefficient by combining the pump chamber volume and the volume of the liquid in the pump chamber;

[0015] Determine the constraint conditions;

[0016] Calculate the optimal coefficients of each term of the Fourier series expansion;

[0017] Determine the optimized plunger movement equation of the oil pump;

[0018] Back-calculate the polished rod movement equation and the motor movement speed from the plunger movement equation of the oil pump.

[0019] Among them, the determination of the inflow characteristic curve includes:

[0020] Combined with the bottom hole flowing pressure p wf , liquid production index J o , average formation pressure p r , saturation pressure p b , obtain an equation representing the liquid production q o , so as to draw the inflow characteristic curve,

[0021]

[0022] Among them, the determination of the outflow characteristic curve includes:

[0023] Combined with the flowing bottomhole pressure p s , the tubing diameter d, the friction factor f; the average temperature T, the compressibility factor Z at the average temperature and average pressure, the relative density of natural gas rg, to obtain the equation representing the tubing discharge flow rate q sc , thus drawing the outflow characteristic curve,

[0024]

[0025] Among them, calculating the depth of the dynamic liquid level includes:

[0026] From the dynamic balance of the well liquid level, combined with the actual oil production Q 0 on the ground, the pumping flow rate Q pump of the pumping unit, p b = p wf when the productivity index J, the saturation pressure p b , the displacement coefficient η p , the plunger cross-sectional area f p , the effective stroke S p ; the pumping speed n; the inner diameter of the casing d ci , the outer diameter of the tubing d ie , calculate the depth of the dynamic liquid level h d (t),

[0027]

[0028] Among them, calculating the reasonable flowing bottomhole pressure includes:

[0029] Combined with the optimal flowing bottomhole pressure p wf , the casing pressure P c , the depth of the middle of the oil layer H z , the pump setting depth L, the density of crude oil γ o , the density of the liquid-gas mixture in the well γ 1 , calculate the reasonable flowing bottomhole pressure h s .

[0030] Among them, expressing the plunger motion equation of the sucker rod pump in the form of a Fourier series expansion includes:

[0031] Select the plunger motion equation x(t) assumed by the Fourier series expansion, set it as the object to be solved, and solve each coefficient according to each constraint condition,

[0032]

[0033] Select different k, ɑ 0 , ɑ 1 , b 1 ,... ɑ k , b kBy varying the 0 , ɑ 1 , b 1 ,... ɑ k , b k values, different forms of changes can be induced in the curve, and there are multiple different curve forms for x(t). For the problem of optimizing the curve x(t), that is, to solve a set of optimal k, ɑ

[0034] Among them, calculating the volume of the liquid in the pump chamber includes:

[0035] Combined with the submerged pressure p s , the pressure p(t) in the pump, the flow area A of the fixed valve s , the resistance coefficient ξ of the fixed valve v , the constant C related to the unit system, and the density ρ of the well fluid o , representing the volume V 1 (t) of the liquid in the pump chamber

[0036]

[0037] Among them, determining the constraint conditions includes:

[0038] The optimized pump efficiency η v should be greater than the pump efficiency η before optimization 0 ; the maximum stress at any cross-section of the sucker rod should not exceed the maximum allowable stress; the inspection pump period of the optimized sucker rod should not be lower than that of the sucker rod before optimization.

[0039] Among them, calculating the optimal coefficients of each term of the Fourier series expansion includes:

[0040] Using the optimization algorithm with the pump fullness coefficient as the optimization object: using the constraint conditions as the calculation boundary conditions, calculating and solving the optimal coefficients of each term of the Fourier series expansion, X = {a 0 , a 1 , b 1 , a 2 , b 2 ,... a k , b k}(k = 1, 2,... k).

[0041] Among them, determining the motion equation of the plunger of the optimized oil pump includes:

[0042] The motion law equation of the plunger of the optimized oil pump is represented by the coefficients of each term of the calculated Fourier series expansion, obtaining the plunger displacement-time, velocity-time, and acceleration-time curves.

[0043] The method for determining the optimal pumping rate of a beam pumping unit in this application has the following beneficial effects:

[0044] In the method for determining the optimal pumping rate of a beam pumping unit in the present invention, according to formation parameters of the oil well and parameters such as the structure of the sucker rod pump, simulation optimization and simulation are carried out to obtain the optimal motion law curve of the plunger, so that the motion law of the sucker rod pump plunger matches the production capacity condition of the oil well being produced on site. Without reducing the service life of the pumping system, the pump efficiency, pumping efficiency are improved, and pumping consumption is reduced. Brief Description of the Drawings

[0045] Figure 1 It is a schematic flow chart of a method for determining the optimal pumping rate of a beam pumping unit according to an embodiment of the present application;

[0046] Figure 2 It is a coordination diagram of oil well supply and discharge according to an embodiment of the present application;

[0047] Figure 3 It is the optimized plunger displacement-time, velocity-time, and acceleration-time curves according to an embodiment of the present application. Detailed Embodiments

[0048] The present application will be further introduced below in conjunction with the drawings and embodiments.

[0049] In the following description, the terms "first" and "second" are only for the purpose of description and cannot be construed as indicating or implying relative importance. The following description provides multiple embodiments of the present invention, and different embodiments can be replaced or combined. Therefore, the present application can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present application should also be considered to include embodiments containing all other possible combinations of A, B, C, and D, even though such embodiments may not be explicitly recited in the following content.

[0050] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes can be made to the functions and arrangements of the described elements without departing from the scope of the content of the present application. Each example can appropriately omit, substitute, or add various processes or components. For example, the described method can be executed in a different order than the described order, and various steps can be added, omitted, or combined. In addition, the features described in some examples can be combined into other examples.

[0051] Embodiment 1

[0052] As Figure 1As shown in the figure, the method for determining the optimal pumping rate of a beam pumping unit in this application includes: S101, determining the inflow characteristic curve; S102, determining the outflow characteristic curve; S103, drawing a coordination diagram of oil well supply and discharge according to the inflow characteristic curve and the outflow characteristic curve; S104, calculating the dynamic liquid level depth; S105, calculating the reasonable submergence degree; S106, expressing the plunger motion equation of the oil pump in the form of a Fourier series expansion; S107, calculating the pump chamber volume between the plunger and the fixed valve; S108, calculating the liquid volume in the pump chamber; S109, calculating the pump filling coefficient by combining the pump chamber volume and the liquid volume in the pump chamber; S110, determining the constraint conditions; S111, calculating the optimal coefficients of each term in the Fourier series expansion; S112, determining the optimized plunger motion equation of the oil pump; S113, inversely deducing the polished rod motion equation and the motor motion rate from the plunger motion equation of the oil pump.

[0053] A method for determining the optimal pumping rate of a beam pumping unit in the present invention belongs to the field of variable-speed operation of pumping units. This invention can improve the problem of mismatch between the plunger motion law of the oil pump and the well conditions, achieve the coordination of pump supply and discharge, reduce the occurrence of "liquid hammer" and insufficient liquid supply phenomena, optimize the plunger motion speed, improve the pump efficiency, and realize the "one well, one strategy" adjustment of the running stroke speed of the pumping unit well.

[0054] Embodiment 2

[0055] The present invention first proposes to construct the plunger motion equation of the oil pump with Fourier series, use the pump filling degree coefficient as the optimization objective function, and use the pump efficiency, sucker rod life, etc. as the constraint conditions to calculate and solve the optimal plunger motion law equation of the oil pump, and inversely deduce the polished rod and motor motion rates from the plunger motion law equation, so as to obtain the optimal pumping rate matching the downhole conditions.

[0056] The method of this application includes the following steps: (1) Combining parameters such as bottom-hole flowing pressure, liquid production index, formation pressure, saturation pressure, etc., to obtain the liquid production equation of the oil well and determine the inflow characteristic curve; (2) Combining parameters such as submergence pressure, tubing diameter, friction coefficient, etc., to obtain the tubing discharge flow equation and determine the outflow characteristic curve; (3) According to the inflow characteristic curve and the outflow characteristic curve, draw the supply-discharge coordination diagram of the oil well. The intersection point of the two curves is the optimal supply-discharge coordination point of the oil well. In the area to the left of the supply-discharge coordination point, the liquid supply capacity of the oil well is stronger than the discharge capacity of the pump, and the production potential of the oil well cannot be fully released. In the area to the right of the supply-discharge coordination point, although the discharge capacity of the pump is relatively strong, due to the weak liquid supply capacity of the oil well, there is a phenomenon of supply falling short of demand. Therefore, only at the supply-discharge coordination point can the supply-discharge situation of the oil well reach coordination, obtaining the maximum lifting output. Take the bottom-hole flowing pressure and liquid production parameters at the supply-discharge coordination point for subsequent calculations; (4) Combining parameters such as actual surface oil production, oil production index, saturation pressure, stroke, pumping frequency, etc., to calculate the dynamic liquid level depth; (5) Combining parameters such as the optimal bottom-hole flowing pressure, casing pressure, middle depth of the oil layer, pump setting depth, etc., to calculate the reasonable submergence degree; (6) Considering factors such as the curve having a certain periodicity, smooth general shape, no mutations, value selection situation, etc., select to represent the plunger movement equation of the sucker rod pump in the form of a Fourier series expansion, so that the equation can generate multiple solution values, ensuring that multiple flexible solution forms can be generated through different combinations of coefficients, achieving the maximization of curve optimization. By solving the optimal coefficient values of a set of equations under constraint conditions, the optimal curve can be obtained; (7) Combining parameters such as plunger cross-sectional area, stroke, etc., to represent the pump chamber volume between the plunger and the standing valve; (8) Combining parameters such as submergence pressure, pump internal pressure, standing valve flow area, resistance coefficient, etc., to represent the liquid volume in the pump chamber; (9) Combining the pump chamber volume and the liquid volume in the pump chamber to represent the pump filling coefficient, with the pump filling coefficient as the main optimization target; (10) By determining constraint conditions such as pump efficiency, working stress of the sucker rod, fatigue life of the sucker rod, etc., provide an executable solution domain for the coefficient solution values of the optimized curve; (11) Calculate the optimal coefficients of each term of the Fourier series expansion by combining the optimization algorithm with the optimization target and constraint conditions; (12) Determine the optimized plunger movement equation of the sucker rod pump and draw the optimized plunger displacement-time, velocity-time, and acceleration-time curves; (13) Invert the polished rod movement equation and the motor movement speed from the plunger movement equation of the sucker rod pump.

[0057] Specifically, in step 1, determining the inflow characteristic curve includes: combining the bottom-hole flowing pressure p wf , liquid production index J o , average formation pressure p r , saturation pressure p b to obtain the Vogel equation representing the liquid production q o , thereby drawing the inflow characteristic curve.

[0058]

[0059] Step 2, determining the outflow characteristic curve includes:

[0060] Combining the flowing bottom-hole pressure p s , the tubing diameter d, the friction factor f; the average temperature T, the compressibility factor Z at the average temperature and average pressure, the relative density of natural gas rg, to obtain an equation representing the tubing discharge flow rate q sc , and thus draw the outflow characteristic curve.

[0061]

[0062] Step 3, draw the oil well supply and discharge coordination diagram according to the inflow characteristic curve and the outflow characteristic curve. The intersection point of the two curves in the oil well supply and discharge coordination diagram is the optimal supply and discharge coordination point. Only at the optimal supply and discharge coordination point can the supply and discharge conditions of the oil well reach coordination, which is the best point for the oil well to obtain the maximum lifting production. Therefore, select the values at the supply and discharge coordination point for subsequent calculations.

[0063] Step 4, calculating the dynamic liquid level depth includes:

[0064] From the dynamic balance of the oil well liquid level, combining the actual oil production Q 0 on the ground, the pumping volume Q pump of the pumping unit, p b = p wf when the productivity index J, the saturation pressure p b , the displacement coefficient η p , the plunger cross-sectional area f p , the effective stroke S p ; the pumping speed n; the casing inner diameter d ci , the tubing outer diameter d ie , calculate the dynamic liquid level depth h d (t).

[0065]

[0066] Step 5, calculating the reasonable submergence degree includes: Combining the optimal bottom-hole flowing pressure p wf , the casing pressure P c , the middle depth H of the oil layer z , the pump setting depth L, the crude oil density γ o , the liquid-gas mixture density γ in the well 1 , calculate the reasonable submergence degree h s .

[0067] Step 6. When constructing the form of the plunger motion curve, the key point of this method is to consider that the curve has a certain periodicity, with a smooth general shape, no mutations, and multiple solution values to ensure that various flexible solution forms can be generated through combinations of different coefficients, achieving the maximization of optimization. Combining the stroke and the pumping speed, assume the plunger motion equation x(t) in the form of a Fourier series expansion, and set it as the object to be solved. Then, the coefficients can be solved according to each constraint condition.

[0068]

[0069] Select different k, ɑ through the constraint conditions 0 , ɑ 1 , b 1 ,... ɑ k , b k values, which can make the curve have different forms of changes. x(t) will have multiple different curve forms. For the problem of optimizing the curve x(t), that is, to solve a set of optimal k, ɑ 0 , ɑ 1 , b 1 ,... ɑ k , b k values, so as to obtain the optimal solution under the constraint conditions.

[0070] Step 7. Calculate the pump chamber volume V(t) between the plunger and the fixed valve.

[0071]

[0072] Step 8. Calculate the liquid volume in the pump chamber, including:

[0073] Combined with the submerged pressure p s , the pump internal pressure p(t), the fixed valve flow area A s , the fixed valve resistance coefficient ξ v , the constant C related to the unit system, and the well fluid density ρ o , representing the liquid volume V 1 (t).

[0074]

[0075] Step 9. Take the pump filling coefficient β as the optimization objective function.

[0076] Step 10. Determine the constraint conditions, including:

[0077] The optimized pump efficiency η v should be greater than the pump efficiency η before optimization 0 (η v >η 0); The maximum stress at any cross-section of the sucker rod should not exceed the maximum allowable stress (σ max ≤ [σ max ); The pump inspection period of the optimized sucker rod is not less than that of the sucker rod before optimization (N fv ≤ N f ).

[0078] Step 11, calculating the optimal coefficients of each term in the Fourier series expansion includes:

[0079] Using the optimization algorithm with the pump fullness coefficient as the optimization object: taking the constraint conditions as the boundary conditions for calculation, calculating and solving the optimal coefficients of each term in the Fourier series expansion, X = {a 0 , a 1 , b 1 , a 2 , b 2 ,... a k , b k} (k = 1, 2,... k).

[0080] Step 12, determining the motion equation of the plunger of the optimized oil pump includes:

[0081] Using the coefficients of each term in the calculated Fourier series expansion to represent the motion law equation of the plunger of the optimized oil pump, obtaining the plunger displacement-time, velocity-time, and acceleration-time curves.

[0082] Step 13: Back-calculating the polished rod motion equation and the motor motion speed from the plunger motion equation of the oil pump.

[0083] Example Three

[0084] The pumping unit is of the CYJ10-3-37HB type, with a stroke of 3m and a pumping frequency of 6min -1 . The basic parameters of the oil well and the physical properties of the fluid are shown in Table 1:

[0085] Table 1 Basic parameters of the oil well and physical properties of the fluid

[0086]

[0087] As shown in the appendix Figure 2 , first determine the inflow characteristic curve q o = 6.045(14.8 - p wf ), and the outflow characteristic curve and draw the supply and discharge coordination diagram of the oil well. The intersection point of the two curves in the figure is the optimal supply and discharge coordination point. This numerical point is the best point for the oil well to obtain the maximum lifting output (i.e., p wf = 5.5MPa, q o = 48m 3(d). Then, based on the values at the determined optimal coordination point of supply and discharge and the basic parameters of the oil well, the dynamic liquid level value is calculated to be 860 m and the reasonable submergence degree is 193 m.

[0088] Express the plunger motion equation of the sucker rod pump in the form of a Fourier series expansion. According to the calculation, the pump chamber volume expression V(t) = 0.0054 * x(t) + 0.00095 between the plunger and the fixed valve and the liquid volume expression V 1 (t) = 0.0405 * v(t) + 0.00095 in the pump chamber are obtained, representing the pump filling coefficient Take the variable pump filling degree β as the optimization objective and determine the constraint conditions of the optimization objective: (1) The pump efficiency after optimization is greater than the pump efficiency before optimization (η v / η 0 ≥ 1); (2) During the entire pumping process, the maximum stress at any cross-section of the sucker rod does not exceed the maximum allowable stress (σ max <[σ max ); (3) The fatigue life of the sucker rod does not decrease (N fv / N < 1). These constraint conditions provide an executable solution domain for the coefficient solution values of the optimization curve.

[0089] Take the Fourier coefficients of the plunger displacement as the design variables, take the pump efficiency, the sucker rod life, and the working stress of the sucker rod as the constraint conditions, and take the pump efficiency as the objective function (i.e., β max = max[x(a 0 、a 1 ...a k ; b 1 、b 2 ...b k )]) to establish a mathematical model for the real-time optimization design of the plunger speed. According to optimization algorithms such as the genetic algorithm, the coefficients of the Fourier series expansion are calculated as follows:

[0090]

[0091] That is, the coefficients of each item of the optimized plunger displacement function of the sucker rod pump and the motion equation are obtained as:

[0092]

[0093] As shown in the appendix Figure 3 , finally, the plunger displacement-time, velocity-time, and acceleration-time curves are plotted.

[0094] Compared with the plunger motion curve before optimization, the optimized plunger motion curve has a greater initial acceleration of the plunger in the upstroke and a greater maximum speed reached, which is beneficial to making the pressure change in the pump more rapid and the liquid entering the pump more quickly; while the speed in the early stage of the downstroke is smaller, the maximum value of the plunger acceleration in the downstroke is smaller, and the average acceleration is also smaller, which is beneficial to the gentle discharge of the fluid in the pump and reduces the liquid impact situation.

[0095] Through test comparison, on the premise of meeting the control target value, the optimized pump efficiency has increased from 36.7% to 40.2%, an increase of 3.5%, and the sucker rod life has increased by 1.6%, with an obvious improvement effect.

[0096] The above introduction is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the optimal pumping rate of a beam pumping unit, characterized in that, comprising: determining the inflow characteristic curve; determining the outflow characteristic curve; drawing a well supply and discharge coordination diagram according to the inflow characteristic curve and the outflow characteristic curve; calculating the dynamic liquid level depth; calculating the reasonable submergence degree; expressing the plunger motion equation of the sucker rod pump in the form of a Fourier series expansion; expressing the plunger motion equation of the sucker rod pump in the form of a Fourier series expansion, including: selecting to assume the plunger motion equation x(t) in the form of a Fourier series expansion, setting it as the object to be solved, and solving each coefficient according to each constraint condition, k = 1, 2, 3...k; By selecting different k and ɑ through the constraint conditions 0 , ɑ 1 , b 1 ,... ɑ k , b k values, the curve can be made to have different forms of change, and x(t) will have multiple different curve forms. For the problem of optimizing the curve x(t), that is, to solve a set of optimal k and ɑ 0 , ɑ 1 , b 1 ,... ɑ k , b k values such that the optimal solution can be obtained under the constraint conditions; calculating the pump chamber volume V(t) between the plunger and the fixed valve, calculating the liquid volume in the pump chamber; including: Combined with the sinking pressure p s , the pressure p(t) inside the pump, the flow area A of the fixed valve s , the resistance coefficient ξ of the fixed valve v , the constant C related to the unit system, the density ρ of the well fluid o , representing the volume V 1 (t) of the liquid in the pump chamber calculating the pump filling coefficient by combining the pump chamber volume and the liquid volume in the pump chamber; determining the constraint conditions; including: The optimized pump efficiency η v should be greater than the pump efficiency η before optimization 0 ; the maximum stress at any cross-section of the sucker rod should not exceed the maximum allowable stress; the inspection and pump replacement period of the optimized sucker rod should not be lower than that of the sucker rod before optimization; calculating the optimal coefficients of each term of the Fourier series expansion; including: The optimization algorithm takes the pump fullness coefficient as the optimization object: uses the constraint conditions as the calculation boundary conditions, and calculates and solves the coefficients of each term in the optimal Fourier series expansion. X = {a 0 , a 1 , b 1 , a 2 , b 2 ,... a k , a k}, k = 1, 2, 3... k; determining the optimized plunger motion equation of the sucker rod pump; inversely deducing the polished rod motion equation and the motor motion rate from the plunger motion equation of the sucker rod pump.

2. The method for determining the optimal pumping rate of a beam pumping unit according to claim 1, characterized in that, the determination of the inflow characteristic curve includes: Combined with the bottom-hole flowing pressure p wf , the liquid production index J o , the average formation pressure p r , the saturation pressure p b , an equation representing the liquid production rate q o is obtained, and thus the inflow performance curve is plotted.

3. The method for determining the optimal pumping rate of a beam pumping unit according to claim 2, characterized in that, the determination of the outflow characteristic curve includes: Combined with the flowing bottomhole pressure p s , tubing diameter d, friction factor f; average temperature T, compressibility factor Z at average temperature and average pressure, relative density of natural gas rg, an equation for expressing the tubing discharge flow rate q sc is obtained, and thus the outflow characteristic curve is plotted.

4. The method for determining the optimal pumping rate of a beam pumping unit according to any one of claims 2-3, characterized in that, the calculation of the dynamic liquid level depth includes: Based on the dynamic balance of the oil well liquid level and combined with the actual oil production Q on the ground 0 , the pumping rate Q of the pumping unit pump , p b = p wf when the productivity index J, saturation pressure p b , displacement coefficient η p , plunger cross-sectional area f p , effective stroke S p ; stroke frequency n; casing inner diameter d ci , tubing outer diameter d ie , calculate the dynamic liquid level depth h d (t), 5. The method for determining the optimal pumping rate of a beam pumping unit according to any one of claims 1-3, characterized in that, the calculation of the reasonable submergence degree includes: Combined with the optimal bottom-hole flowing pressure p wf , casing pressure P c , midpoint depth of the oil reservoir H z , pump setting depth L, crude oil density γ o , liquid-gas mixture density γ in the well 1 , calculate the reasonable submergence depth h s .

6. The method for determining the optimal pumping rate of a beam pumping unit according to any one of claims 1-3, characterized in that, the determination of the optimized plunger motion equation of the sucker rod pump includes: expressing the optimized plunger motion law equation by the coefficients of each term of the calculated Fourier series expansion, and obtaining the plunger displacement-time, velocity-time, and acceleration-time curves.

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