Screw pump service life prediction method

Abstract

The invention relates to a method for predicting the service life of a screw pump, which is used for predicting the service life of a target screw pump by fitting a changing curve of a pump service life index which is positively correlated with the performance of the target screw pump along with operation time. The method is simple and efficient, can predict the service life of the screw pump according to the specification of the screw pump and the well condition of the oil well where the screw pump is located, and is wide in application range and high in prediction precision.

Description

Technical Field

[0001] The invention relates to the technical field of screw pumps, in particular to a method for predicting the life of a screw pump. Background Art

[0002] As the core equipment of the oil production system, the screw pump has shown significant advantages in heavy oil production and deep inclined well conditions due to its high stability and high adaptability to heavy oil. This type of pump achieves volumetric transportation through the meshing movement of the stator and rotor pair, and its theoretical volumetric efficiency (pump efficiency minus mechanical efficiency) can reach more than 90%. However, during long-term operation in complex underground conditions, the screw pump faces multiple failure mechanisms: 1. The alternating load during operation can easily cause plastic deformation of the stator and rotor materials; 2. Sandy crude oil causes wear on the stator and rotor meshing surfaces, which increases the clearance and reduces the volumetric efficiency. 3. Crude oil containing hydrogen sulfide can easily cause rotor cracking, stator swelling or hydrogen embrittlement; 4. High temperature and high pressure environment induces material creep, resulting in mismatch of the internal and external spiral lines of the screw pump, torque disorder, and reduced efficiency.

[0003] When the damage of the screw pump reaches a certain extent and the pump efficiency cannot be maintained at a high level even if the speed is increased / when the speed has reached the highest but the pump efficiency is still lower than expected, the screw pump is considered scrapped, which means the end of its life.

[0004] Since there are many types of oil wells in the oil field, and the well conditions such as well depth, well inclination, and oil viscosity are also different, even the same type of screw pump has different lifespans in different oil wells, which greatly increases the difficulty of predicting the life of screw pumps. The failure mode of screw pumps presents multi-physical field coupling characteristics, and the existing prediction model is difficult to accurately characterize the progressive damage process of the pump body under complex well conditions. The existing life prediction methods have significant limitations: 1. Relying on a single performance parameter (such as pump efficiency) to make threshold judgments, lacking multi-parameter coupling analysis; 2. Machine learning is used, but there is a lack of a large number of high-quality data sets that match the applied well conditions, resulting in overfitting.

[0005] Therefore, we propose a method for predicting the life of screw pumps. Summary of the invention

[0006] In view of the above-mentioned shortcomings in the prior art, the applicant provides a method for predicting the life of a screw pump.

[0007] The technical solution adopted by the present invention is as follows: A method for predicting the life of a screw pump, comprising: The curve of the pump life index of the target screw pump changing with the running time is fitted, and the pump life index is positively correlated with the performance of the target screw pump. The life of the target screw pump is predicted based on the change curve.

[0008] A further technical solution thereof includes fitting a curve showing a change in the pump life index of a target screw pump with respect to the running time, including: According to several pump life indexes of the target screw pump in a set operation period, a curve of the pump life index of the target screw pump changing with the operation time is obtained by fitting; and / or, According to several pump life indexes of a test screw pump of the same specification as the target screw pump during its entire life cycle, a curve of the pump life index of the target screw pump changing with the running time is obtained by fitting.

[0009] A further technical solution thereof includes: a method for determining a pump life index includes: Determine the theoretical performance curve of the target screw pump, which indicates the corresponding relationship between the pump pressure difference and the theoretical pump efficiency of the target screw pump at the actual speed; Based on the theoretical performance curve and actual operating parameters of the target screw pump, the theoretical speed of the target screw pump is determined using a first formula; the first formula indicates the corresponding relationship between the theoretical operating parameters and the actual operating parameters of the target screw pump; The pump life index is determined based on the theoretical speed and actual speed of the target screw pump.

[0010] Its further technical solution includes that the expression of the first formula is: S th =S ac (1-E th ) / (1-E ac ); Among them, S th is the theoretical speed of the target screw pump, E th is the theoretical pump efficiency of the target screw pump, S ac is the actual speed of the target screw pump, E ac It is the actual pump efficiency of the target screw pump.

[0011] A further technical solution thereof includes that the actual operating parameters include at least one of the actual rotation speed, the actual pump efficiency, and the pump pressure difference, and the theoretical operating parameters include at least one of the theoretical rotation speed and the theoretical pump efficiency.

[0012] A further technical solution includes determining a pump life index according to a theoretical speed and an actual speed of a target screw pump, including: Determine the pump life index Y=S th / S ac , where Sth is the theoretical speed of the target screw pump, S ac is the actual speed of the target screw pump.

[0013] A further technical solution thereof includes: the expression of the curve of the pump life index of the target screw pump obtained by fitting and the change of the running time is: Y(X)=AX B ; Among them, Y is the pump life index, X is a quantity that is positively correlated with the operating time of the target screw pump, and A and B are fitting coefficients.

[0014] A further technical solution thereof includes that X is any one of the operating time of the target screw pump, the sampling times of the pump life index, and the accumulated number of revolutions of the target screw pump.

[0015] Its further technical solution includes predicting the life of the target screw pump based on the change curve, including: When the pump life index is less than or equal to the set threshold, the target screw pump is determined to be scrapped; The life of the target screw pump is determined as the total time from the initial operation time to the scrapping time.

[0016] Its further technical solution includes predicting the life of the target screw pump based on the change curve, including: When the target screw pump is running at a constant actual speed S ac_h Running, and the speed index S=α(S ac_h -S th ) / S ac_h +β is greater than or equal to the set speed index threshold S max When the corresponding pump life index Y is determined s =S th / S ac_h , combined with the change curve to determine the pump life index Y S The target screw pump is scrapped at the corresponding moment, and the life of the target screw pump is predicted; When the target screw pump has a constant actual pump efficiency E ac_h Operation, and the pump efficiency index E=γ(E th -E ac_h ) / E th +δ is greater than or equal to the set pump efficiency index threshold E max When the corresponding pump life index Y is determined E =(1-E th ) / (1-E ac_h ), combined with the change curve to determine the pump life index Y E The target screw pump is scrapped at the corresponding moment, and the life of the target screw pump is predicted; Among them, S this the theoretical speed of the target screw pump, E th is the theoretical pump efficiency of the target screw pump, and α, β, γ, and δ are all constants.

[0017] The beneficial effects of this application are as follows: The method for predicting the life of a screw pump designed in this application predicts the life of a target screw pump by fitting a curve of the pump life index that is positively correlated with the performance of the target screw pump versus the operating time. This method is simple and efficient, and can accurately predict the life of a screw pump based on its specifications and the well conditions of the oil well in which it is located.

[0018] The present application also designs a matching test method, using a test screw pump of the same specification as the target screw pump to conduct a control variable test under different well parameters, and then combining the well parameters of the target screw pump corresponding to the oil well to obtain its preliminary predicted life. The preliminary predicted life of the target screw pump can be used to plan its control after installation in advance, which can improve the pump efficiency and extend the life of the screw pump to a certain extent.

[0019] The present application also designs a method for calculating the pump life index, and obtains the corresponding pump life index change curve through fitting. This method calculates through the logical relationship of operating parameters such as pump efficiency, speed, and pump pressure difference, conforms to the objective law of screw pump operation, is applicable to various well conditions and screw pumps of various specifications, has a wide range of applications and high prediction accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a flow chart of a method for predicting the life of a screw pump in one embodiment of the present invention.

[0021] Figure 2 1 is a flow chart of a method for determining a pump life index in one embodiment of the present invention.

[0022] Figure 3 It is a schematic diagram of a theoretical performance curve of a target screw pump in one embodiment of the present invention. DETAILED DESCRIPTION

[0023] The specific implementation of the present application is described below in conjunction with the accompanying drawings.

[0024] Screw pumps are widely used in oil production in major oil fields. Their performance and life play an important role in the reliability and oil production efficiency of the entire screw pump oil production system. By accurately predicting the life of the screw pump, the relevant production process can be arranged in advance, and the oil production produced by the screw pump can be estimated, which is convenient for oil production efficiency and cost accounting. To this end, this embodiment discloses a method for predicting the life of a screw pump, such as Figure 1 As shown, including: S110, a curve of the pump life index of the target screw pump changing with the running time is obtained by fitting, and the pump life index is positively correlated with the performance of the target screw pump.

[0025] Among them, the performance of the screw pump reflects the integrity and accuracy of the overall structure of the screw pump. As the running time of the screw pump increases, its stator and rotor will gradually show wear, distortion, deformation, corrosion and other phenomena, the performance of the screw pump will continue to decline, and the pump life index will also decrease accordingly.

[0026] S120, predicting the life of the target screw pump based on the change curve.

[0027] In this embodiment, the variation curve of the pump life index decreases over time, and by presetting a threshold value corresponding to the pump life index when the screw pump is scrapped, the life of the target screw pump can be predicted.

[0028] In order to better understand the screw pump life prediction method of the present application, another embodiment is described in detail below.

[0029] This embodiment discloses a method for predicting the life of a screw pump, comprising: S110, a curve of the pump life index of the target screw pump changing with the running time is obtained by fitting, and the pump life index is positively correlated with the performance of the target screw pump.

[0030] In one embodiment, step S110 specifically includes: According to several pump life indexes of the target screw pump in a set operating period, a curve of the pump life index of the target screw pump changing with the operating time is obtained by fitting.

[0031] Specifically, after the target screw pump is put into the oil well for operation, the pump life index at multiple sampling moments is obtained, and then the pump life index change curve corresponding to the target screw pump is obtained by fitting.

[0032] Optionally, the time intervals between the various sampling moments are equal, or the number of revolutions of the screw pump between the various sampling moments is equal.

[0033] In another embodiment, step S110 specifically includes: According to several pump life indexes of a test screw pump of the same specification as the target screw pump during its entire life cycle, a curve of the pump life index of the target screw pump changing with the running time is obtained by fitting.

[0034] Specifically, before the target screw pump is installed in the well, the pump life index of several test screw pumps of the same specification is sampled to obtain several curves of the pump life index changing with the running time. Based on these change curves, the life of the target screw pump can be roughly predicted.

[0035] Furthermore, the pump life index change curves of several test screw pumps of the same specification as the target screw pump under different preset well condition parameters are obtained through the control variable method, and then the preset well condition parameters closest to the well condition parameters of the oil well corresponding to the target screw pump are determined, and the corresponding pump life index change curve is used as the pump life index change curve of the target screw pump.

[0036] Optionally, the well condition parameter is at least one of oil viscosity, temperature, and well depth.

[0037] In addition, the present application can also combine the methods in the two embodiments of the above step S110, that is, firstly make a rough life prediction for the target screw pump through a test screw pump of the same specification as the target screw pump, and then after the target screw pump is installed in the well, collect the actual pump life index of several target screw pumps and fit them, so as to obtain a more accurate predicted life.

[0038] In this embodiment, the expression of the curve of the pump life index of the target screw pump obtained by fitting versus the running time is: Y(X)=AX B ; Among them, Y is the pump life index, X is a quantity that is positively correlated with the operating time of the target screw pump, and A and B are fitting coefficients.

[0039] Optionally, X is any one of the operating time of the target screw pump, the sampling times of the pump life index, and the accumulated number of revolutions of the target screw pump.

[0040] In this embodiment, the method for determining the pump life index includes: A110, determine the theoretical performance curve of the target screw pump, the theoretical performance curve indicates the corresponding relationship between the pump pressure difference and the theoretical pump efficiency of the target screw pump at the actual speed.

[0041] In this embodiment, the theoretical performance curve of each screw pump is related to its specifications and well conditions.

[0042] A120, based on the theoretical performance curve and actual operating parameters of the target screw pump, the theoretical speed of the target screw pump is determined using the first formula; the first formula indicates the corresponding relationship between the theoretical operating parameters and the actual operating parameters of the target screw pump.

[0043] In this embodiment, the expression of the first formula is: S th =S ac (1-E th ) / (1-E ac ); Among them, S th is the theoretical speed of the target screw pump, E th is the theoretical pump efficiency of the target screw pump, Sac is the actual speed of the target screw pump, E ac It is the actual pump efficiency of the target screw pump.

[0044] Optionally, the actual operating parameters include at least one of an actual rotational speed, an actual pump efficiency, and a pump pressure difference, and the theoretical operating parameters include at least one of a theoretical rotational speed and a theoretical pump efficiency.

[0045] Among them, the theoretical pump efficiency is related to the specifications of the screw pump and the well conditions, and has nothing to do with the wear of the pump.

[0046] A130, determines the pump life index based on the theoretical speed and actual speed of the target screw pump.

[0047] In this embodiment, the pump life index Y=S is determined th / S ac , where S th is the theoretical speed of the target screw pump, S ac is the actual speed of the target screw pump.

[0048] S120, predicting the life of the target screw pump based on the change curve.

[0049] Since the change curve of the pump life index reflects the performance of the screw pump, both of them decrease with the running time of the screw pump. Therefore, in this embodiment, when the pump life index is less than or equal to the set threshold, it is determined that the target screw pump is scrapped. And the life of the target screw pump is set to the total time from the initial running time to the scrapping time.

[0050] In one embodiment, predicting the life of a target screw pump based on the change curve includes: When the target screw pump is running at a constant actual speed S ac_h Running, and the speed index S=α(S ac_h -S th ) / S ac_h +β is greater than or equal to the set speed index threshold S max When the corresponding pump life index Y is determined s =S th / S ac_h , combined with the change curve to determine the pump life index Y S The target screw pump is scrapped at the corresponding time, and the life of the target screw pump is predicted. th is the theoretical speed of the target screw pump, and α and β are constants.

[0051] For example, Figure 3 As shown, the target screw pump is assumed to have a constant actual speed S ac_h =100 operation, α=1, β=0, speed index threshold S max=0.9. As the target screw pump runs, its theoretical speed S th Will continue to decrease, when S th =10, the speed index S=S max =0.9, the screw pump is scrapped at this time, and the corresponding pump life index Y s = 0.1, find Y according to the change curve of pump life index s =0.1, the corresponding screw pump running time, take this running time as the target screw pump life. Optionally, the speed unit is revolutions per minute.

[0052] In another embodiment, predicting the life of a target screw pump based on the variation curve includes: When the target screw pump has a constant actual pump efficiency E ac_h Operation, and the pump efficiency index E=γ(E th -E ac_h ) / E th +δ is greater than or equal to the set pump efficiency index threshold E max When the corresponding pump life index Y is determined E =(1-E th ) / (1-E ac_h ), combined with the change curve to determine the pump life index Y E At the corresponding moment, the target screw pump is scrapped, and the life of the target screw pump is predicted. th is the theoretical pump efficiency of the target screw pump, and γ and δ are both constants.

[0053] In addition, the present application can also combine the methods in the above two embodiments. For example, after the target screw pump is installed and operated, the actual speed S is constant before the time x1. ac_h After x1, the actual pump efficiency is constant. ac_h Operation, the selection of x1 is set according to the actual situation of the target screw pump, and this application does not limit this.

[0054] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A method for predicting the life of a screw pump, characterized in that: The method comprises: A curve of the pump life index of the target screw pump changing with the running time is obtained by fitting, and the pump life index is positively correlated with the performance of the target screw pump; The life of the target screw pump is predicted based on the change curve.

2. The method for predicting the life of a screw pump according to claim 1, characterized in that: The fitting obtains a curve of the pump life index of the target screw pump changing with the running time, including: According to a plurality of pump life indexes of the target screw pump in a set operation period, a curve of the pump life index of the target screw pump changing with the operation time is obtained by fitting; and / or, According to several pump life indexes of a test screw pump of the same specification as the target screw pump during its entire life cycle, a curve of the change of the pump life index of the target screw pump versus the operating time is obtained by fitting.

3. The method for predicting the life of a screw pump according to claim 2, characterized in that: Methods for determining the pump life index include: Determine a theoretical performance curve of a target screw pump, wherein the theoretical performance curve indicates a corresponding relationship between a pump pressure difference and a theoretical pump efficiency of the target screw pump at an actual rotation speed; Based on the theoretical performance curve and actual operating parameters of the target screw pump, the theoretical speed of the target screw pump is determined using a first formula; the first formula indicates the corresponding relationship between the theoretical operating parameters and the actual operating parameters of the target screw pump; The pump life index is determined according to the theoretical rotation speed and the actual rotation speed of the target screw pump.

4. The method for predicting the life of a screw pump according to claim 3, characterized in that: The expression of the first formula is: S th =S ac (1-E th ) / (1-E ac ); Among them, S th is the theoretical speed of the target screw pump, E th is the theoretical pump efficiency of the target screw pump, S ac is the actual speed of the target screw pump, E ac is the actual pump efficiency of the target screw pump.

5. The method for predicting the life of a screw pump according to claim 1, characterized in that: The actual operating parameters include at least one of an actual rotation speed, an actual pump efficiency, and a pump pressure difference, and the theoretical operating parameters include at least one of a theoretical rotation speed and a theoretical pump efficiency.

6. The method for predicting the life of a screw pump according to claim 3, characterized in that: Determining the pump life index according to the theoretical speed and the actual speed of the target screw pump includes: Determine the pump life index Y=S th / S ac , where S th is the theoretical speed of the target screw pump, S ac is the actual speed of the target screw pump.

7. The method for predicting the life of a screw pump according to claim 1, characterized in that: The expression of the curve of the pump life index of the target screw pump obtained by fitting versus the running time is: Y(X)=AX B ; Among them, Y is the pump life index, X is a quantity that is positively correlated with the operating time of the target screw pump, and A and B are fitting coefficients.

8. The method for predicting the life of a screw pump according to claim 7, characterized in that: X is any one of the operating time of the target screw pump, the sampling number of the pump life index, and the cumulative number of revolutions of the target screw pump.

9. The method for predicting the life of a screw pump according to claim 1, characterized in that: The predicting the life of the target screw pump based on the change curve includes: When the pump life index is less than or equal to a set threshold, the target screw pump is determined to be scrapped; The life of the target screw pump is determined as the total duration from the initial operation time to the scrapping time.

10. The method for predicting the life of a screw pump according to claim 3, characterized in that: The predicting the life of the target screw pump based on the change curve includes: When the target screw pump is rotating at a constant actual speed S ac_h Running, and the speed index S=α(S ac_h -S th ) / S ac_h +β is greater than or equal to the set speed index threshold S max When the corresponding pump life index Y is determined s =S th / S ac_h , combined with the change curve to determine the pump life index Y S At a corresponding moment, the target screw pump is scrapped, and the life of the target screw pump is predicted; When the target screw pump has a constant actual pump efficiency E ac_h Operation, and the pump efficiency index E=γ(E th -E ac_h ) / E th +δ is greater than or equal to the set pump efficiency index threshold E max When the corresponding pump life index Y is determined E =(1-E th ) / (1-E ac_h ), and determine the pump life index Y in combination with the change curve E At a corresponding moment, the target screw pump is scrapped, and the life of the target screw pump is predicted; Among them, S th is the theoretical speed of the target screw pump, E th is the theoretical pump efficiency of the target screw pump, and α, β, γ, and δ are all constants.

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