CN116411930A - Method and system for judging eccentric wear of rod and tube of rod-pumped well based on indicator diagram - Google Patents

Abstract

The invention discloses a method and a system for judging the eccentric wear of a rod tube of a rod-pumped well based on an indicator diagram, which specifically comprises the following steps: simultaneously collecting load data and displacement data of a pumping rod tube of the pumping unit well in each hour and actual input motor power of a pumping unit motor, and obtaining a polished rod indicator diagram according to the change rule of the load data and the displacement data and time; establishing a polished rod tube indicator diagram drift judgment model, judging whether the suspension point load sensor drifts or not according to the actual input motor power of the pumping unit motor, and obtaining a specific drift amount; establishing a calculation model of the friction force of the rod pipe of the up-down stroke, and calculating the friction force of the rod pipe of the up-down stroke; judging the eccentric wear of the rod tube of the oil pumping well according to the friction force of the rod tube of the up-down stroke; whether the underground rod pipe is subjected to eccentric wear can be judged, meanwhile, the stress condition of the rod column can be judged, the reason of the eccentric wear is distinguished, and the eccentric wear is caused by the borehole track or the eccentric wear caused by instability, so that improvement measures are provided in a targeted manner.

Description

Method and system for judging eccentric wear of rod and tube of rod-pumped well based on indicator diagram

Technical Field

The invention belongs to the technical field of oil extraction in an oil field, and particularly relates to an oil pumping unit well rod tube eccentric wear judging method and system based on an indicator diagram.

Background

The long-day oilfield adopts cluster type directional well group development, and the problems of complex well track and eccentric wear are outstanding. The frequency and cost of well repair operation are always high. The maintenance workload caused by eccentric wear of the well pipe rod of the oil pumping unit reaches 31.6%, the maintenance workload is increased by 6.5% in 5 years, the problem is increasingly remarkable, and the problem becomes a key for influencing the benefit development of the cluster directional well group.

At present, the most direct method for judging whether the eccentric wear occurs between the underground oil pipe and the sucker rod is to observe whether the conditions of scratch, wear-through, fracture, deformation and the like occur on the surfaces of the sucker rod and the oil pipe after the underground pipe column is lifted up by detecting the pump operation, so that whether the eccentric wear exists in the underground oil pipe is judged, and the reason is determined according to the result. The indirect method can predict whether the rod is eccentrically worn under the conditions of known borehole track, dynamic and static data of an oil well, rod column combination and the like through the optimization design software of the directional well, belongs to the pre-judgment of the underground condition according to the existing conditions, and possibly has access to the actual condition, and for a new production well, the optimization design software is applied to optimize and increase a centralizing wear-resistant tool for an underground rod pipe, and then the eccentric wear phenomenon of the oil well still occurs, so that the prediction is inconsistent with the actual condition, therefore, a judging method and a system for reliably and accurately judging whether the rod pipe is eccentrically worn underground are needed, early warning is carried out in advance before the off-line fault is caused by the eccentric wear of the rod pipe, and the rod is prevented from being broken.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides the method and the system for judging the eccentric wear of the rod tube of the oil pumping machine based on the indicator diagram, which not only can judge whether the underground rod tube is eccentric worn, but also can judge the stress condition of the rod column, and distinguish the reason of the eccentric wear, whether the eccentric wear is caused by the eccentric wear caused by the track of the well hole or the eccentric wear caused by the instability, thereby providing a targeted improvement measure.

In order to achieve the above purpose, the present invention provides the following technical solutions: the eccentric wear judging method for the rod tube of the rod-pumped well based on the indicator diagram comprises the following specific steps:

s1, simultaneously acquiring load data and displacement data of a sucker rod pipe of a pumping unit well and actual input motor power of a motor of the pumping unit, and obtaining a polished rod indicator diagram according to a change rule of the load data and the displacement data and time;

s2, a polished rod indicator diagram drift judgment model is established, whether the suspension point load sensor drifts or not is judged through the actual input motor power of the pumping unit motor, and a specific drift amount is obtained;

s3, establishing an up-down stroke rod tube friction force calculation model, and calculating the up-down stroke rod tube friction force;

and S4, judging the eccentric wear of the rod pipe of the oil pumping well according to the friction force of the rod pipe of the up-down stroke.

Further, in step S1, load data and displacement data of the sucker rod of the rod-pumped well per hour are detected by using a load sensor mounted on the wellhead string hanger and a displacement sensor below the walking beam.

Further, in step S1, three-phase current and voltage of the motor input end of the pumping unit in each hour are collected by the electric energy collection module, and actual input motor power is obtained by the three-phase electric energy quality analysis device.

Further, in step S2, the polished rod indicator diagram driftsThe judging model is used for comparing the predicted input power of the pumping unit motor obtained by calculation according to the crank shaft simulation torque based on the actually measured suspension point load with the actual input power of the pumping unit motor at the same time, judging whether the suspension point load sensor of the pumping unit drifts or not, and calculating the evaluation index sigma of the load drift _PMI ：

Wherein P is _MIPRL -predicting the instantaneous input power of the pumping unit motor calculated on the basis of the polished rod indicator diagram; p (P) _MIM Is the actual input power of the motor of the pumping unit.

Further, in step S2, the load sensor is determined to drift when the drift amount is greater than 5%.

In step S2, a simulation model of the net torque of the crankshaft is built according to the polished rod indicator diagram, the torque coefficient of the pumping unit and the balancing device parameter, and the simulation model of the net torque of the crankshaft is used to obtain the simulation torque of the crankshaft based on the actually measured suspension point load.

Further, in step S3, friction force P between sucker rod and oil pipe during upstroke _{On the pole tube} The method comprises the following steps:

P _{on the pole tube} ＝P _{Upper part} -P _{On the upper part of the body} -P _{Pump piston} -P _{Liquid in pipe} (28)

Wherein P is _{Upper part} -upstroke suspension point load, N; p (P) _{On the upper part of the body} -friction load on upstroke, N; p (P) _{Pump piston} -friction force between plunger and pump barrel, N; p (P) _{Liquid in pipe} -liquid friction between oil and tubing, N;

friction force P between sucker rod and oil pipe during downstroke _{Under the rod tube} The method comprises the following steps:

P _{under the rod tube} ＝P _{Under friction with} -P _{Under the pump plug} -P _{Rod liquid} -P _Valve (29)

Wherein P is _{Under friction with} -friction load on downstroke, N; p (P) _{Under the pump plug} -semi-dry friction between plunger and cylinder, N; p (P) _{Rod liquid} -liquid friction between sucker rod and column, N; p (P) _Valve -the friction of the fluid produced by the flow of fluid through the travelling valve, N.

Further, in step S4, the conditions for judging the eccentric wear of the oil engine well rod pipe are as follows:

the invention provides an indicator diagram-based rod and tube eccentric wear judging system of an oil pumping machine, which comprises a load sensor arranged on a wellhead rope hanger, a displacement sensor arranged below a walking beam, an electric energy acquisition module arranged at the input end of a control cabinet of the oil pumping machine, a control terminal arranged in a control cabinet of a well group, a data processing device, an internal computer and a rod and tube eccentric wear automatic judging program arranged in an in-station computer, wherein the rod and tube eccentric wear automatic judging program is used for executing the rod and tube eccentric wear judging method of the rod and tube of the oil pumping machine according to claims 1-8.

Further, when in use, 1) acquiring a suspension point load value of the pumping rod of the pumping well in each hour through a load sensor; obtaining a displacement value of the pumping rod of the pumping well in each hour through a displacement sensor; the three-phase current and the three-phase voltage of the input end of the motor of the pumping unit in each hour are collected through the electric energy collection module, and the input power of the motor of the pumping unit is obtained through calculation through the three-phase electric energy quality analysis module;

2) The obtained suspension point load and displacement data are transmitted to a control terminal, the control terminal transmits the suspension point load and displacement data to a data processing device, and the data processing device converts the received signals into digital signals and transmits the digital signals to a computer in a station;

3) The in-station computer runs an automatic rod and pipe eccentric wear judging program to judge whether the rod and pipe are eccentric worn or not, judge the type of eccentric wear and prompt and alarm the well with serious eccentric wear.

Compared with the prior art, the invention has at least the following beneficial effects:

according to the oil well indicator diagram data collected in real time, the friction force during up-down stroke is calculated, whether the underground rod tube is eccentrically worn or not is judged according to the obtained friction force, the reason for eccentric wear is found, and a centralizing anti-wear device can be designed for an eccentric wear well caused by a well track; for the eccentric wear well caused by instability, the rod column structure can be redesigned, so that the design error of the rod column is corrected, the fine management level of the oil well is further improved, the pump inspection of the oil well due to the eccentric wear of the rod tube is avoided, and the pump inspection period of the oil well is prolonged.

The judging system of the invention acquires the oil well indicator diagram data in real time, carries out on-line diagnosis on the eccentric wear condition of the well pipe rod of the oil pumping unit, can also track the data and analyze the eccentric wear trend of the well pipe of the oil pumping unit to obtain the wear degree of the well pipe, and can send out an alarm when the wear degree is overlarge.

Drawings

Figure 1 mechanical analysis model of reversing mechanism of rear beam pumping unit

FIG. 2 shows an actual measured electric power curve and a simulated power curve based on an indicator diagram, (a) a polished rod indicator diagram; (b) an actual input power profile of the pumping unit motor; (c) The input power curve is predicted by the motor of the pumping unit based on the polish rod indicator diagram;

fig. 3 rod tube friction zone.

Detailed Description

The invention is further described below with reference to the drawings and the detailed description.

The invention provides a diagnosis method of a rod tube of a rod-pumped well based on an indicator diagram, which comprises the following specific steps:

the first step: and acquiring a suspension point load and time curve of the suspension point position of the load sensor test pumping unit, acquiring a displacement and time curve of the suspension point position of the position sensor test pumping unit, and synthesizing a polish rod indicator diagram according to the two curves.

And a second step of: according to the polished rod indicator diagram, a simulation model of the net torque of the crankshaft is established by combining the torque coefficient of the pumping unit and the balance device parameter of the pumping unit, and the simulation torque of the crankshaft based on the actually measured suspension point load is obtained according to the simulation model of the net torque of the crankshaft;

specifically, for a beam pumping unit driven by a common Y-series motor, the motor rotation speed fluctuation is small, and the slip is generally less than 3%, so that the motor is assumed to rotate at a constant speed. According to the polished rod indicator diagram of the first step, and combining the torque coefficient of the pumping unit and the balance device parameter of the pumping unit, a simulation model of the net torque of the crankshaft is established, and the specific formula of the simulation model of the net torque of the crankshaft is as follows:

wherein: m is M _NPRL -a simulated torque of the crankshaft based on the measured suspension point load N.m;

-torque coefficient, m; PRL-measured suspension point load, N; b (B) _W -pumping unit mechanism unbalance weight, N; m is M _c Crank balancing torque, N.m; θ—crank angle, rad; θ ₀ -the suspension point bottom dead center crank initial rotation angle, rad; τ—the crank counterweight offset angle, rad; w is the weight of the walking beam counterweight and N; l (L) _W -balance radius of walking beam balance weight, m; τ _y -the angle of oscillation of the walking beam with respect to the horizontal, rad; τ _y0 -walking beam counterweight offset angle, rad; w (W) ₁ -walking beam hanging counterweight weight, N; l (L) _W1 -balance radius of walking beam suspension balance weight, m; a, a _A Suspension point motion acceleration, m/s ² The method comprises the steps of carrying out a first treatment on the surface of the R-crank radius, m; p is the length of the connecting rod, m; c, the length of a rear arm of the walking beam, m; k is the length of the base rod, m; a is the length of the forearm of the walking beam, m; i-horizontal projection length of base rod, m. η (eta) _CL -the transmission efficiency of the crank-rocker mechanism; k (k) ₁ Coefficient, k ₁ = ±1. When v _A When not less than 0, k ₁ -1; when v _A When < 0, k ₁ ＝1。

As can be seen from equation (1), the net torque of the crankshaft is composed of two parts: firstly, torque generated by the suspension point load; and secondly, the torque generated by the balancing device. When the balance device parameters are known, the net torque of the crankshaft can be calculated by the equation (1), and the net torque curve of the crankshaft is drawn.

And a third step of: the drift judgment model of the polished rod tube indicator diagram utilizes the simulation torque of the crankshaft to calculate and obtain the predicted input power of the motor of the pumping unit, compares the actual input power of the motor of the pumping unit with the predicted input power of the motor of the pumping unit at the same time, judges whether the load sensor of the pumping unit suspension point drifts, calculates the drift amount and obtains the calibration error of the load sensor;

in particular, the method comprises the steps of,

A. calculating predicted input power of a motor of the pumping unit:

first, calculating the instantaneous output power P of the motor of the pumping unit by using the simulation torque of the crankshaft _MOPRL The formula is as follows:

wherein: p (P) _MOPRL -the instantaneous output power of the pumping unit motor, kW, based on the measured setpoint load PRL; omega-angular velocity of crank rotation, rad/s; η (eta) _MB -the transmission efficiency of the belt and the reduction gearbox; k (k) ₂ -coefficients. When M _N At > 0, k ₂ -1; when M _N K is less than or equal to 0 ₂ ＝1。

Secondly, according to the instantaneous output power P of the motor of the pumping unit _MOPRL Calculating the instantaneous power utilization rate beta and the instantaneous efficiency eta of the motor of the pumping unit _M The formula is as follows:

wherein: beta-motor instantaneous power utilization; η (eta) _M -motor instantaneous efficiency; p (P) _N -motor power rating, kW; p (P) ₀ -motor power consumption, kW; η (eta) _N -motor nominal efficiency.

Then, utilizing the instantaneous power utilization rate beta and the instantaneous efficiency eta of the motor of the pumping unit _M The predicted instantaneous input power and the predicted average input power of the motor of the pumping unit are calculated, and the formula is as follows:

p in the formula _MIPRL -predicting the instantaneous input power, kW, of the motor of the pumping unit calculated on the basis of the polished rod indicator diagram;

the average input power is predicted by the motor of the pumping unit, which is calculated based on the polished rod indicator diagram, and kW; t-period of suspension point movement, s.

B. Calculation of actual input power of pumping unit motor

Let P be _MIM The average input power of the motor of the pumping unit is the actual input power of the motor of the pumping unit

The actual measurement values of the power balance degree are as follows:

C. evaluation index of load drift

Because of the influence of the test error and the model error, the predicted input power curve of the pumping unit motor based on the polished rod indicator diagram and the actual input power curve of the pumping unit motor generally do not completely coincide. To reflect the coincidence degree of two power curves, the root mean square sigma of the sum of the squares of the input power difference of the motor is adopted _PMI Drift amount as load drift:

drift amount = root mean square of sum of squares of difference values of predicted input power and actual input power of a motor of the pumping unit divided by maximum value of actual input power, when the drift amount is greater than 5%, the drift of the load sensor is recognized, early warning is needed, and 5% of the value can be regulated according to the service condition of the load sensor.

Fourth step: as shown in fig. 1, carrying out stress analysis on a rod column in the up-down stroke process of a pumping unit sucker rod, taking a suspension point load value of the middle position of the up-down stroke of a polish rod indicator diagram, correcting the suspension point load in the polish rod indicator diagram by using the calibration error obtained in the step three, and calculating the friction force of the up-down stroke rod tube;

specifically, the suspension point load can reflect all loads acting on the sucker rod underground, including various friction forces, can be represented through a ground work diagram, and the friction force in the suspension point load consists of two parts, namely the friction force between the sucker rod and an oil pipe and the friction force between a plunger and a pump cylinder, and the friction force between a sucker rod string and the oil string, the friction force between the oil string and the oil pipe and the friction force between the oil string and the oil flow of the pump valve group. Because the action direction of the friction force is opposite to the movement direction of the sucker rod, the influence of the friction force on the suspension point load is different in the up-down stroke movement process;

during the upstroke, the pumping unit drives the pumping rod to move upwards, the friction force is downward, and the friction force increases the suspension point load, so the suspension point load at the moment is as follows:

P _{upper part} ＝P _{Quiet upward} +P _{Inertial robot} +P _{Vibration device} +P _{On the upper part of the body} (8)

Wherein: p (P) _{Upper part} -upstroke suspension point load, N; p (P) _{Quiet upward} Suspension point static load on upstroke, N; p (P) _{Inertial robot} -inertial load on upstroke, N; p (P) _{Vibration device} -vibration load on upstroke, N; p (P) _{On the upper part of the body} -friction load on upstroke, N;

wherein A. Static load

Dead load = sucker rod dead weight + plunger upper liquid column load

P _{Quiet upward} ＝W _r +W _l (9)

Sucker rod dead weight:

plunger upper liquid column load:

B. inertial load

C. Vibration load

The maximum value of the vibration load occurs at the end of the extension deformation of the upstroke sucker rod and at the instant when the downstroke deformation is fully recovered. I.e. the top dead center position, the vibration load is relatively small in the middle of the stroke and approximately equal in magnitude to the downstroke, here ignored.

D. Friction load

P _{On the upper part of the body} The oil pump consists of three parts, namely, friction force between the sucker rod and an oil pipe, friction force between a plunger and a pump cylinder, liquid friction force between oil liquid and the oil pipe and unit N.

P _{On the upper part of the body} ＝P _{On the pole tube} +P _{Pump piston} +P _{Liquid in pipe} (13)

Wherein:

wherein: ρ _s Density of sucker rod (steel), ρ _s ＝7850kg/m ³ The method comprises the steps of carrying out a first treatment on the surface of the g-gravity acceleration, m/s ² ；A _ri -cross-sectional area of the ith sucker rod, m ² ；L _i -length of the i-th sucker rod, m; q _ri -weight per unit length of the i-th sucker rod, N/m; d, d _p -diameter of the plunger of the oil pump, m; delta-gap m between plunger and cylinder radius of oil pump; p (P) _{On the pole tube} -friction force between sucker rod and tubing during upstroke, N.

E. Suspension point load due to upstroke sinking pressure

In the upstroke, under the action of sinking pressure, the resistance of the inlet device of the in-well liquid customer service pump enters the pump, and at the moment, the pressure of liquid flow is called suction pressure, and the pressure acts on the bottom of the plunger to generate upward load:

P _{sinking to} ＝(p _n -Δp _i )f _p (18)

Wherein Δp _i Suction pressure, pa; f (f) _p -plunger cross-sectional area, m2; Δp _i -the pressure drop, pa, of the liquid flow through the inlet device of the pump.

F. Suspension point load caused by back pressure of upstroke wellhead

The wellhead back pressure created by the flow resistance of the fluid in the surface pipeline will create additional load to the suspension point, which is the same in nature as the load created by the fluid in the tubing, increasing the suspension point load in the upstroke and decreasing the sucker rod string load in the downstroke.

P _{Returning to} ＝p _h (f _p -f _r ) (19)

Wherein p is _h -wellhead back pressure, pa; f (f) _r -sucker rod cross-sectional area, m2;

because the sink pressure and wellhead back pressure are opposite in direction to the suspension point load caused in the upstroke, they may be partially inefficient with respect to each other, and therefore, are ignored in the calculations of the present application.

During the down stroke, the sucker rod moves downwards, the direction of the friction force is upward, and the friction force reduces the suspension point load, so the suspension point load is at the moment:

P _{lower part(s)} ＝P _{Under static condition} -(P _{Under the inertia} +P _{Vibration device} )-P _{Under friction with} (20)

Wherein: p (P) _{Lower part(s)} -downstroke suspension point load; p (P) _{Under static condition} Suspension point static load on downstroke, N; p (P) _{Under the inertia} -inertial load on downstroke, N; p (P) _{Under the inertia} -inertial load of downstroke; p (P) _{Vibration device} -vibration load on downstroke, N; p (P) _{Under friction with} -friction load on downstroke, N;

A. static load

The down stroke, the dead load at the suspension point is equal to the dead weight of the rod string minus the buoyancy of the well fluid on the sucker rod string.

P _{Under static condition} ＝W _r -W _f (21)

B. Inertial load

In the downstroke, the first half stroke acceleration is negative, i.e., the acceleration is downward, and the inertial force is upward, thereby reducing the suspension point load, and the second half stroke acceleration is positive, i.e., the acceleration is upward, and the inertial force is downward, thereby increasing the suspension point load.

C. Vibration load

The maximum value of the vibration load occurs at the end of the extension deformation of the upstroke sucker rod and at the instant when the downstroke deformation is fully recovered, i.e., at the bottom dead center position, where the vibration load is relatively small and approximately equal in magnitude to the upstroke, and is ignored here.

D. Friction load

According to the actual working condition of the oil well, P _{Under friction with} Consists of four parts: friction between sucker rod and oil pipe; semi-dry friction between plunger and cylinder; liquid friction between sucker rod and oil column; liquid flowThe friction of the liquid generated by the flow through the travelling valve.

P _{Under friction with} ＝P _{Under the rod tube} +P _{Under the pump plug} +P _{Rod liquid} +P _Valve (23)

Wherein:

wherein: w (W) _f -buoyancy of well production fluid to the sucker rod string, N; a is that _P Plunger cross-sectional area, m ² The method comprises the steps of carrying out a first treatment on the surface of the n-pumping unit sprint, min ^-1 The method comprises the steps of carrying out a first treatment on the surface of the ζ -the flow coefficient determined by the test, can be obtained by looking up a table; a is that ₀ Valve bore cross-sectional area of travelling valve, m ² The method comprises the steps of carrying out a first treatment on the surface of the S, stroke of the pumping unit, m; p (P) _{Under the rod tube} -friction force, N, between sucker rod and tubing during downstroke; p (P) _{Under the pump plug} -semi-dry friction between plunger and cylinder, N; p (P) _{Rod liquid} -liquid friction between sucker rod and column, N; p (P) _Valve -the friction of the liquid produced by the flow of the liquid through the travelling valve, N;

according to the polished rod indicator diagram obtained in the step 1, the suspension point load of the up-down stroke can be obtained, and the position of the minimum value of the vibration load and the inertia load is considered to be in the middle of the dead points of the up-down stroke, so that the formula can be deformed as follows:

equation 8 and equation 20 may be modified as follows:

P _{on the upper part of the body} ＝P _{Upper part} -P _{Quiet upward} (26)

P _{Under friction with} ＝P _{Under static condition} -P _{Lower part(s)} (27)

The friction between the sucker rod and the oil pipe during the up-down stroke is obtained by taking formula 26 and formula 27 into formulas 13 and 23 respectively, wherein the formulas are as follows:

P _{on the pole tube} ＝P _{Upper part} -P _{On the upper part of the body} -P _{Pump piston} -P _{Liquid in pipe} (28)

Wherein P is _{Upper part} -upstroke suspension point load, N; p (P) _{On the upper part of the body} -friction load on upstroke, N; p (P) _{Pump piston} -friction force between plunger and pump barrel, N; p (P) _{Liquid in pipe} -liquid friction between oil and tubing, N;

P _{under the rod tube} ＝P _{Under friction with} -P _{Under the pump plug} -P _{Rod liquid} -P _Valve (29)

Wherein P is _{Under friction with} -friction load on downstroke, N; p (P) _{Under the pump plug} -semi-dry friction between plunger and cylinder, N; p (P) _{Rod liquid} -liquid friction between sucker rod and column, N; p (P) _Valve -the friction of the fluid produced by the flow of fluid through the travelling valve, N.

Fifth step: the eccentric wear judgment of the sucker rod is carried out according to the friction force between the sucker rod and the oil pipe during the up-down stroke

1. The stress model of the sucker rod is assumed, if the influence of factors such as 'doglegs', deformation of an oil pipe and the like is not considered, the eccentric wear of the sucker rod and the oil pipe does not exist in the upstroke, and in the downstroke, a neutral point with zero stress exists due to the influence of various resistances in the pit, so that the friction force is equal to 0 and is used for eccentric wear judgment as a limit of a judgment standard, and the method is as follows:

on upstroke, if P _{On the pole tube} =0, indicating no friction between the sucker rod and the tubing during the upstroke; p (P) _{On the pole tube} More than 0, the friction exists between the sucker rod and the oil pipe during the upstroke, which indicates that the oil well may have the phenomena of dog leg or bending deformation of the oil pipe, and the like, so that the sucker rod contacts with the oil pipe to generate friction, and the friction load is equal to P _{On the pole tube} 。

On downstroke, if P _{Under the rod tube} =0, indicating that the sucker rod is frictionless with the tubing on the downstroke; p (P) _{Under the rod tube} More than 0, the friction exists between the sucker rod and the oil pipe during the downstroke, which indicates that the sucker rod may have instability deformation, the oil well may have dogleg phenomenon or oil pipe bending deformation, etc., causingThe sucker rod contacts with the oil pipe to generate friction, and the friction load is equal to P _{Under the rod tube} 。

2. The limit of the friction force equal to 0 is based on an ideal state, the bias grinding judgment basis is also required to be defined according to the actual condition of the site, and the friction force of the rod and the pipe of the oil pumping machine with serious bias grinding is mostly more than 2000N, so that the limit of the friction force between the oil pumping rod and the oil pipe in the up-down stroke is more than 2000N and is serious bias grinding, and the friction force is more than 0 and less than 2000N and is general bias grinding, and the limit of-1000 is general bias grinding can be properly considered in consideration of calculation errors; if the friction of the rod string of a severely biased rod is mostly above 4000N, the severely biased and the general biased are defined by the limit of 4000N.

In the following, 2000N is taken as an example, the friction force of the up-down stroke rod tube is divided into three sections as shown in fig. 3, and the three sections are combined arbitrarily to find judgment conditions and conclusions, and the judgment conditions and conclusions are specifically shown in table 1:

table 1 conditions for determination of eccentric wear

When the friction force between the down-stroke sucker rod and the oil pipe is larger than-1000N and the friction force between the up-stroke sucker rod and the oil pipe is larger than 2000N, judging that the phenomenon of rod column instability and dogleg occurs if the friction force between the up-stroke sucker rod and the oil pipe is smaller than the friction force between the down-stroke sucker rod and the oil pipe; if the friction force between the upstroke sucker rod and the oil pipe is larger than the friction force between the downstroke sucker rod and the oil pipe, judging that a dog leg or oil pipe bending deformation phenomenon occurs;

when the friction force between the down stroke sucker rod and the oil pipe is larger than-1000N and the friction force between the up stroke sucker rod and the oil pipe is smaller than 2000N, the dog leg or the oil pipe bending deformation phenomenon is judged to occur.

When the friction force between the upstroke sucker rod and the oil pipe is smaller than 2000N and the friction force between the downstroke sucker rod and the oil pipe is larger than 2000N, judging that the phenomenon of instability of the pole column occurs;

when the friction force between the upper stroke sucker rod and the oil pipe and the friction force between the lower stroke sucker rod and the oil pipe are more than-1000N and less than or equal to 2000N, the slight eccentric wear is judged;

and when the friction force between the upstroke sucker rod and the oil pipe and the friction force between the downstroke sucker rod and the oil pipe are less than or equal to minus 1000N, judging that the parameter is wrong or the sensor drifts.

According to the principle, an on-line system for the eccentric wear of the directional well rod and tube is established, wherein fig. 2 (a) is a diagram of an actual measurement indicator diagram in the field, fig. 2 (b) is a diagram of an actual measurement electric power curve, and fig. 2 (c) is an electric power input power based on the simulation based on fig. 2 (a), and obviously, the simulation power curve and the actual measurement power curve have obvious differences. And diagnosing whether the output data of the load sensor has drift according to the difference of the two curves, and further diagnosing the drift amount.

The diagnosed load drift amount was 4786N. The load sensor is calibrated in a laboratory, and the load drift amount is 4997N. The calibration error based on the load drift of the electric parameter dynamometer is 4.41%. And correcting the suspension point load in the polished rod indicator diagram according to the calibration error. If drift is judged, the drift amount is determined, the correction is carried out in the subsequent calculation process, if the suspension point load value deviates upwards by 10%, the suspension point load of the upper and lower strokes in the polished rod indicator diagram is increased by 10%, and if the suspension point load value deviates downwards by 10%, the suspension point load of the upper and lower strokes in the polished rod indicator diagram is reduced by 10%. Calculating the friction force of the rod tube of the up-down stroke on the corrected polished rod indicator diagram, and obtaining whether the rod tube is eccentric-worn or not and the eccentric-worn type as shown in table 2;

table 2 results of calculation of friction force and determination of eccentric wear for up-down stroke tube

The invention also provides an indicator diagram-based rod and tube eccentric wear judging system of the rod and tube of the oil pumping unit, which is used for realizing on-line diagnosis and specifically comprises the following steps: load sensor installed on well head polished rod eye, install the displacement sensor in the walking beam below, install the electric energy collection module at beam-pumping unit switch board input, set up control terminal, data processing device, in-station computer and the automatic judgement recognition program of pole pipe eccentric wear in well group control box, specifically:

(1) the method comprises the following steps The method comprises the steps of obtaining a suspension point load value of a sucker rod of a pumping well in each hour through a load sensor; obtaining a displacement value of the pumping rod of the pumping well in each hour through a displacement sensor; the three-phase current and the three-phase voltage of the input end of the motor of the pumping unit in each hour are collected through the electric energy collection module, the power of the motor of the pumping unit is calculated through the three-phase electric energy quality analysis module, the input power of the motor of the pumping unit is obtained, and particularly, synchronous collection of electric parameter data and load displacement data is required.

(2) And transmitting the obtained suspension point load and displacement data to a control terminal (RTU) through a cable, and transmitting the acquired suspension point load and displacement data to a data processing device at the center of the main station in a wave form through a well group antenna.

(3) The received signals are converted into digital signals by a data processing device and transmitted to an in-station computer.

(4) The automatic judging program for the eccentric wear of the rod and the pipe is installed in the computer in the station, and when the automatic judging program for the eccentric wear of the rod and the pipe is operated by the computer in the station, the automatic judging program for the eccentric wear of the rod and the pipe of the rod-pumped well realizes the judging method for the eccentric wear of the rod and the pipe of the rod-pumped well, judges whether the eccentric wear occurs to the rod and the pipe, judges the type of the eccentric wear and prompts and alarms the well with serious eccentric wear.

Claims (10)

1. The method for judging the eccentric wear of the rod tube of the rod-pumped well based on the indicator diagram is characterized by comprising the following specific steps:

s1, simultaneously acquiring load data and displacement data of a sucker rod pipe of a pumping unit well and actual input motor power of a motor of the pumping unit, and obtaining a polished rod indicator diagram according to a change rule of the load data and the displacement data and time;

s2, a polished rod indicator diagram drift judgment model is established, whether the suspension point load sensor drifts or not is judged through the actual input motor power of the pumping unit motor, and a specific drift amount is obtained;

s3, establishing an up-down stroke rod tube friction force calculation model, and calculating the up-down stroke rod tube friction force;

and S4, judging the eccentric wear of the rod pipe of the oil pumping well according to the friction force of the rod pipe of the up-down stroke.

2. The method for judging the eccentric wear of the rod and tube of the rod-pumped well based on the indicator diagram according to claim 1, wherein in the step S1, load data and displacement data of the rod and tube of the rod-pumped well per hour are detected by a load sensor arranged on a wellhead rope hanger and a displacement sensor below a walking beam.

3. The method for judging the eccentric wear of the rod and tube of the oil pumping machine based on the indicator diagram, which is disclosed in claim 1, is characterized in that in step S1, three-phase current and voltage of the input end of the motor of the oil pumping machine in each hour are collected through an electric energy collection module, and the actual input motor power is obtained through a three-phase electric energy quality analysis device.

4. The method for judging the eccentric wear of a rod tube of a pumping unit well according to claim 1, wherein in the step S2, a drift judgment model of the rod tube indicator diagram is used for comparing the predicted input power of a pumping unit motor obtained by calculation according to the simulation torque of a crank shaft based on the actual measured suspension point load with the actual input power of the pumping unit motor at the same time, judging whether a suspension point load sensor of the pumping unit drifts, and calculating an evaluation index sigma of the load drift _PMI ：

Wherein P is _MIPRL -predicting the instantaneous input power of the pumping unit motor calculated on the basis of the polished rod indicator diagram; p (P) _MIM Is the actual input power of the motor of the pumping unit.

5. The method for judging the eccentric wear of the rod and tube of the rod-pumped well based on the indicator diagram according to claim 4, wherein in the step S2, the load sensor is determined to drift when the drift amount is greater than 5%.

6. The method for judging the eccentric wear of the rod and tube of the rod-pumped well based on the indicator diagram according to claim 4, wherein in the step S2, a simulation model of the net torque of the crankshaft is established according to the torque coefficient and the balance device parameters of the polished rod indicator diagram and the pumping unit, and the simulation model of the net torque of the crankshaft is utilized to obtain the simulation torque of the crankshaft based on the actual measurement suspension point load.

7. The method for judging the eccentric wear of a rod and tube of a rod-pumped well based on an indicator diagram according to claim 1, wherein in step S3, the friction force P between the rod and the tube during the up stroke is _{On the pole tube} The method comprises the following steps:

P _{on the pole tube} ＝P _{Upper part} -P _{On the upper part of the body} -P _{Pump piston} -P _{Liquid in pipe} (28)

Wherein P is _{Upper part} -upstroke suspension point load, N; p (P) _{On the upper part of the body} -friction load on upstroke, N; p (P) _{Pump piston} -friction force between plunger and pump barrel, N; p (P) _{Liquid in pipe} -liquid friction between oil and tubing, N;

friction force P between sucker rod and oil pipe during downstroke _{Under the rod tube} The method comprises the following steps:

P _{under the rod tube} ＝P _{Under friction with} -P _{Under the pump plug} -P _{Rod liquid} -P _Valve (29)

Wherein P is _{Under friction with} -friction load on downstroke, N; p (P) _{Under the pump plug} -semi-dry friction between plunger and cylinder, N; p (P) _{Rod liquid} -liquid friction between sucker rod and column, N; p (P) _Valve -the friction of the fluid produced by the flow of fluid through the travelling valve, N.

8. The method for judging the eccentric wear of the rod-and-tube of the oil pumping unit based on the indicator diagram according to claim 7, wherein in the step S4, the judging condition of the eccentric wear of the rod-and-tube of the oil pumping unit is as follows:

9. the system is characterized by comprising a load sensor arranged on a wellhead rope hanger, a displacement sensor arranged below a walking beam, an electric energy acquisition module arranged at the input end of a pumping unit control cabinet, a control terminal arranged in a well group control box, a data processing device, an internal computer and a rod and pipe eccentric wear automatic judging program arranged in an in-station computer, wherein the rod and pipe eccentric wear automatic judging program is used for executing the rod and pipe eccentric wear judging method of the pumping unit well and pipe according to claims 1-8.

10. The indicator diagram-based rod and tube bias wear determination system of a rod and tube well, as set forth in claim 9, wherein in use 1) obtains a point-of-suspension load value for the rod and tube of the rod and tube well for each hour through a load sensor; obtaining a displacement value of the pumping rod of the pumping well in each hour through a displacement sensor; the three-phase current and the three-phase voltage of the input end of the motor of the pumping unit in each hour are collected through the electric energy collection module, and the input power of the motor of the pumping unit is obtained through calculation through the three-phase electric energy quality analysis module;

2) The obtained suspension point load and displacement data are transmitted to a control terminal, the control terminal transmits the suspension point load and displacement data to a data processing device, and the data processing device converts the received signals into digital signals and transmits the digital signals to a computer in a station;

3) The in-station computer runs an automatic rod and pipe eccentric wear judging program to judge whether the rod and pipe are eccentric worn or not, judge the type of eccentric wear and prompt and alarm the well with serious eccentric wear.

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