Method for determining optimal intermittent pumping period of oil well according to indicator diagram

Abstract

The invention provides a method for determining the optimal intermittent pumping period of an oil well according to an indicator diagram. The method is applied to determining the optimal intermittent pumping period of a low-liquid-production rod pumped well in an oil field. According to an oil well indicator diagram continuously monitored at a wellhead, the change trend of the full degree of the indicator diagram represents a static liquid level recovery curve, and when an oil well continuously works, when the full degree of the indicator diagram is reduced to a certain value and is not obviously reduced any more, the optimal well stopping opportunity is achieved; and the well stopping time of the oil well is increased at a fixed step length, a scatter diagram trend line is drawn, and when the well stopping time is increased and the pumping starting operation time is no longer obviously increased, the optimal pumping starting time is obtained. According to the invention, electricity can be saved to the greatest extent under the condition that the yield is not influenced basically. The downtime is a fixed value, and the pumping starting operation time is a variable value. The method is applied to a low-liquid-production oil well Ha 20 well, intelligent optimization of an intermittent pumping system is achieved, compared with continuous production, the daily liquid production of intermittent pumping operation is slightly increased, and the comprehensive electricity saving rate is 62%.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and in particular relates to a method for determining an optimal intermittent pumping period of an oil well according to a dynamometer diagram. Background Art

[0002] Low-liquid-yield oil wells are limited by the minimum stroke and frequency of the pumping system. Even when producing under extreme parameters, it is still difficult to achieve supply and discharge coordination, resulting in empty pumping, low pump efficiency and high energy consumption for ineffective lifting, and the conditions for continuous well opening cannot be met. Many pumping wells have adopted an automatic control intermittent pumping mode, which effectively reduces operating energy consumption.

[0003] Chinese patent CN114382447A discloses an intelligent control method and device for intermittent pumping of an oil pumping unit, which determines a surface dynamometer diagram of an oil well based on a voltage signal and a current signal of a driving motor; determines a bottomhole dynamometer diagram of an oil well based on the surface dynamometer diagram of the oil well; determines whether the oil pumping unit is in an empty pumping state based on the bottomhole dynamometer diagram of the oil well; and controls the driving motor of the oil pumping unit when the oil pumping unit is in an empty pumping state so that the oil pumping unit operates in an intermittent pumping control mode.

[0004] Chinese patent CN112682008A discloses an oil well inter-pumping method and an oil well inter-pumping device, which mainly detects the rising and falling rules of the liquid level of the low-yield oil well, and controls the intermittent oil production of the pumping unit according to the rules to provide sufficient replenishment time for the liquid level of the low-yield oil well. When the oil volume of the low-yield oil well is sufficient, the work is carried out, and when it is insufficient, the work is stopped. In this way, by formulating and implementing a reasonable intermittent work system, the economic benefits of low-yield wells can be improved, pump efficiency can be improved, electric energy can be saved, mechanical loss can be reduced, and equipment maintenance time and repair costs can be reduced.

[0005] "An Intelligent Interval Pumping Control System for Oil Wells Based on the Internet of Things" published by Jia Zhipeng et al. in the 7th issue of "Internet of Things Technology" in 2021 records: An intelligent interval pumping control system for oil wells based on the Internet of Things. The system is mainly composed of a dynamic liquid level monitor, a dynamometer acquisition module, an interval pumping control cabinet and an interval pumping monitoring background, forming a dual closed-loop control system. It collects, transmits and applies data based on the three-layer architecture of the Internet of Things, realizes real-time collection, reliable transmission, intelligent control and dynamic monitoring of the working status of the pumping unit, and has important application value for the construction of smart oil fields.

[0006] Xie Yingli's "Research on Intelligent Interval Pumping System of Oil Wells Based on Dynamometer Diagram" published in the Journal of Yangtze University, Vol. 14, No. 19, October 2017, records: A set of intelligent interval pumping system for oil wells was developed based on the digital platform of oil fields. The system converts the dynamometer diagram collected by the digital system into a pump dynamometer diagram, diagnoses the pump working condition according to the pump dynamometer diagram, and switches the wells with insufficient fluid supply to interval pumping mode. For interval pumping wells, it is proposed to determine the interval pumping time according to the size of the pump efficiency. The system was applied in two digital cluster well groups, and the results showed that the system played a good role in energy saving and consumption reduction.

[0007] Although many public intermittent pumping control systems and devices can realize automatic control of intermittent pumping in oil wells, there are still certain defects in the way of judging the changing trend of the supply and discharge relationship of oil wells and the intelligent optimization of intermittent pumping cycles. Either the calculation process has large errors and is difficult to implement, which cannot effectively exert the production capacity of oil wells; or the cycle is unreasonable and the process control is unreasonable, which cannot achieve the best energy-saving effect. How to optimize the intermittent pumping system economically and efficiently and achieve the best energy-saving effect without basically affecting the liquid production requires further research.

[0008] In summary, it is necessary to design a method for optimizing the inter-well pumping cycle of low-liquid production pumping units to solve the above problems. Summary of the invention

[0009] The purpose of the present invention is to make up for the shortcomings of the prior art and provide a method for determining the optimal intermittent pumping period of an oil well according to the dynamometer diagram, determining the optimal shutdown time and the optimal pumping start time according to the changing characteristics of the dynamometer diagram, and reducing the operating time to the greatest extent without basically affecting the liquid production of the oil well, thereby achieving the purpose of optimal power saving effect.

[0010] A method for determining an optimal intermittent pumping period of an oil well according to a dynamometer diagram comprises the following steps:

[0011] Step 1: Set the continuous impulse times and calculate the boundary filling degree σ according to the test dynamometer diagram b and shutdown fullness σ s ,

[0012] Boundary filling degree σ b is: b =AD / BC,

[0013] In the formula, line segment AD represents the height of the liquid level in the pump barrel of the oil well pump, and line segment BC represents the effective stroke length of the plunger in the pump barrel;

[0014] Shutdown fullness σ s is: s =2σ b ;

[0015] Step 2: Set the initial downtime to 30 minutes, record the start time t1, and continuously test the dynamometer diagram after start to calculate the fullness σ b , when the filling degree σ b Continuously drop to shutdown full levelσ s When the pump is shut down, record the downtime t2 and calculate the pumping operation time t3;

[0016] Wherein, t3=t2-t1, the pumping operation time t3 is the operation time from pumping start to shut down;

[0017] Step 3: Increase the downtime t2 in fixed steps, repeat step 2, and end the process when the downtime t2 increases and the pumping operation time t3 stops increasing. Record the pumping operation time t3 each time. n ;

[0018] Wherein, said n is greater than or equal to 3 times;

[0019] Step 4: Based on the experimental data of downtime and pumping operation time obtained in step 3, the experimental data are plotted into a scatter plot trend line with downtime as the horizontal axis and pumping operation time as the vertical axis to determine the optimal downtime;

[0020] Step 5. Repeat steps 2-4 at fixed intervals and dynamically optimize the intermittent extraction system according to changes in external conditions.

[0021] Furthermore, the scatter plot trend line is a power function curve or a quadratic polynomial curve.

[0022] Furthermore, the optimal pumping operation time is a variable value, that is, the pumping time from the start to the full degree σ b Reduced to shutdown fullness levelσ s The running time of .

[0023] The embodiments of the present invention bring the following beneficial effects:

[0024] The present invention finds the best pumping stop timing and pumping start timing according to the trend of the fullness change of the power diagram, dynamically adjusts the intermittent pumping system, is more conducive to releasing the production capacity of the oil well, and realizes power saving to the maximum extent under the premise of ensuring that the output does not drop basically.

[0025] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A fullness curve diagram for solving an indicator diagram provided by an embodiment of the present invention;

[0028] Figure 2 A curve chart for determining the optimal downtime provided by an embodiment of the present invention;

[0029] Figure 3 A flow chart for determining an optimal intermittent extraction period from a dynamometer diagram provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figure 1-3 As shown, an embodiment of the present invention provides a method for determining an optimal intermittent pumping period of an oil well according to a dynamometer diagram, comprising the following steps:

[0032] Step 1: The oil well is continuously produced for more than 3 days according to the designed stroke frequency, and the dynamometer diagram is tested to calculate the boundary filling degree σ b and shutdown fullness σ s ,

[0033] If the cycle cannot converge, the shutdown fullness σ can be adjusted appropriately s The value of

[0034] Wherein, the boundary filling degree σ b =AD / BC, shutdown fullness σ s =2σ b ;

[0035] like Figure 1 As shown, point A is the starting point of the upstroke, at which time the floating valve of the oil pump begins to close, the fixed valve begins to open, and the ground sucker rod suspension point begins to be loaded. Due to elastic deformation, the plunger in the pump barrel has not yet started to move; point B is the point where the floating valve is completely closed, at which time the pump plunger has begun to move upward; point C is the point of maximum displacement, after which the pump plunger begins to turn and move downward; point D is the point where the floating valve of the downstroke pump opens and the fixed valve is completely closed. At this point, the plunger just touches the liquid surface in the pump barrel, and the pump barrel is empty between points C and D.

[0036] Since the oil pump is not fully filled when working underground, the better the liquid supply capacity, the better the pump is filled. Conversely, if the liquid supply capacity is poor, the pump is in an empty state. The line segment AD in the figure can represent the height of the liquid level in the pump barrel of the oil pump, the line segment BC can represent the effective stroke length of the plunger in the pump barrel, and AD / BC represents the fullness of the pump.

[0037] Step 2: Switch to intermittent production, set the initial downtime to 30 minutes, record the start time t1, and continuously test the dynamometer diagram after start to calculate the filling degree σ b , when the filling degree σ b Calculate three times in a row to reduce the shutdown fullness level σ s When the pump is shut down, record the downtime t2 and calculate the pumping operation time t3;

[0038] The initial downtime can be adjusted according to the oil well fluid supply capacity, and the pumping operation time t3 = t2 - t1 is the operation time from pumping to shutting down;

[0039] Step 3: Increase the downtime in fixed steps, repeat step 2, and end when the downtime increases and the start-up time stops increasing. Record the start-up time t each time. n ; The fixed step length is generally 10 minutes; the n is greater than or equal to 3 times;

[0040] Step 4: With the downtime as the horizontal axis and the pumping operation time as the vertical axis, the experimental data is plotted into a scatter plot trend line. The integer time corresponding to the extreme point is the optimal downtime.

[0041] Among them, the optimal start-up operation time is the variable value, that is, the time from the start of the pumping to the full degree to the shutdown full degree σ s The running time of the scatter plot is generally a power function curve or a quadratic polynomial curve; the integer time is generally an integer multiple of 10 minutes, which is convenient for calculating the running time of one day and the liquid production of the day;

[0042] Step 5: Repeat steps 2-4 at fixed intervals to dynamically optimize the intermittent extraction system according to changes in external conditions. The fixed interval is generally one month.

[0043] The specific implementation example is: Take Ha 20 well as an example

[0044] Step 1: Run the machine for 3 consecutive days at a rate of 4 strokes / min and calculate the boundary filling degree σ b =10%, take 2 times σ b Assume that the shutdown fullness is s =20%;

[0045] Step 2: Switch to intermittent production. The initial downtime is set to 60 minutes. After starting the pumping, the dynamometer diagram is tested continuously to calculate the fullness. When the fullness drops to the shutdown fullness level σ for three consecutive times, s The machine is shut down at this time, and the pumping operation time is recorded as 20 minutes;

[0046] Step 3: The downtime is increased by 60 minutes. Repeat step 2. When the downtime is 240 minutes, the start-up time will not increase any more and the machine is finished.

[0047] Step 4: With the downtime as the horizontal axis and the pumping operation time as the vertical axis, the experimental data is plotted into a scatter plot trend line, and the optimal downtime is determined to be 160 minutes;

[0048] Step 5. Repeat steps 2-4 every month to dynamically optimize the intermittent sampling system.

[0049] Effect of Ha-20 Well: Compared with continuous production, the liquid production of intermittent pumping operation increased from 2 tons / day to 3.32 tons / day, and the daily power consumption decreased from 104.5 degrees to 39.7 degrees, with a power saving rate of 62%.

[0050] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0051] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the optimal intermittent pumping period of an oil well according to a dynamometer diagram, characterized in that: The following steps are involved: Step 1: Set the continuous impulse times and test the dynamometer diagram to calculate the boundary filling degree σ b and shutdown fullness σ s , Boundary filling degree σ b is: b =AD / BC, In the formula, line segment AD represents the height of the liquid level in the pump barrel of the oil well pump, and line segment BC represents the effective stroke length of the plunger in the pump barrel; Shutdown fullness σ s is: s =2σ b ; Step 2: Set the initial downtime to 30 minutes, record the start time t1, and continuously test the dynamometer diagram after start to calculate the fullness σ b , when the filling degree σ b Continuously drop to shutdown full levelσ s When the pump is shut down, record the downtime t2 and calculate the pumping operation time t3; Wherein, t3=t2-t1, the pumping operation time t3 is the operation time from pumping start to shut down; Step 3: Increase the downtime t2 in fixed steps, repeat step 2, and end the process when the downtime t2 increases and the pumping operation time t3 stops increasing. Record the pumping operation time t3 each time. n ; Wherein, said n is greater than or equal to 3 times; Step 4: Based on the experimental data of downtime and pumping operation time obtained in step 3, the experimental data are plotted into a scatter plot trend line with downtime as the horizontal axis and pumping operation time as the vertical axis to determine the optimal downtime; Step 5. Repeat steps 2-4 at fixed intervals and dynamically optimize the intermittent extraction system according to changes in external conditions.

2. The method for determining the optimal intermittent pumping period of an oil well according to claim 1, characterized in that: The scatter plot trend line is a power function curve or a quadratic polynomial curve.

3. The method for determining the optimal intermittent pumping period of an oil well according to claim 1, characterized in that: The optimal pumping operation time is a variable value, that is, the pumping time from the start to the full degree σ b Reduced to shutdown fullness levelσ s The running time of .

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