Sucker rod pump automated control method and system

Abstract

A sucker rod pump automated control method comprising measuring the sucker rod pump parameters, counting the sucker rod pump geometry, forming a dynamometer card of the sucker rod pump parameters. Measuring an angle of the sucker rod pump walking beam, and based on the walking beam angle value, forming a real time value of the sucker rod pump crank angle and a polished rod velocity with using geometry dependences of the sucker rod pump components. The walking beam is equipped with an angle sensor connected to a PC input and is formed to detecting position of the walking beam.

Claims

1. A sucker rod pump automated control method comprising: measuring the sucker rod pump parameters, counting the sucker rod pump geometry, forming a dynamometer card of the sucker rod pump parameters, providing the sucker rod pump motor control signals depending on measured parameters, the measured parameters comprising at least a load or/and a velocity of a polished rod, wherein at least the motor torque, the polished rod load or/and velocity are calculated based on mass and geometry values of the sucker rod pump components with counting current and voltage parameters; calculating the motor momentary power value (MMP) and a counter weight system power (CWP) during each reciprocating stroke of the polished rod, and using a variable speed drive (VSD) active power value excluding a losses, wherein calculating the active power value based on a frequency setting (f) value, wherein changing the frequency setting (f) value relative to the sucker rod pump filling rate; wherein measuring the angle of the sucker rod pump walking beam, and based on the walking beam angle value, forming the real time values of the sucker rod pump crank angle and the polished rod velocity with using geometry dependences of the sucker rod pump components.

2. The method according to claim 1 wherein obtaining the motor torque average value by: comparing the motor torque average value relative to the motor torque reference value, wherein taking the motor torque reference value calculated on a first sucker rod pump stroke, and taking the motor torque reference value calculated on low motor velocity, wherein said motor torque reference value showing a ratio between the motor torque average value and the sucker rod pump filling rate, wherein at least the sucker rod pump filling rate reflects changing of the polished rod load.

3. The method according to claim 1 and 2 wherein calculating the motor torque average value during each reciprocation period of the polished rod, wherein the reciprocation period start is related to the polished rod end point.

4. The method according to claim 1 wherein calculating a current motor power expended in motion of the polished rod, forming a current motor power based on the VSD active power value excluding the losses, wherein calculating a stator and a rotor power losses of the motor, and taking into account the sucker rod pump dynamic moment and a mechanical losses within the sucker rod pump swing joints.

5. The method according to claim 1 wherein using the VSD programmable controller, forming a surface and a down hole dynamometer card of the sucker rod pump parameters, wherein calculating the motor momentary power value (MMP), the counter weight system power (CWP), the polished rod load or/and velocity.

6. The method according to claim 1 wherein based on the sucker rod pump parameters dynamometer card forming the frequency settings value and calculating the VSD output voltage.

7. The method according to claim 1 wherein calculating geometry dependences of the sucker rod pump components via dimensioning, wherein using the geometry dependences for calculating the counter weight system power (CWP), the polished rod load or/and velocity.

8. The method according to claim 1 wherein calculating the load zero portion at the polished rod end points, wherein the load zero portion is forming a part of the polished road stroke length, wherein forming the polished rod load constant value at an input/output of the zero portion, wherein forming an intermediate load value as a calculated mathematic value.

9. A sucker rod pump automated control system comprising: a variable speed drive (VSD) equipped with a programmable controller (PC) and connected with a motor, the motor is designed as a drive for the sucker rod pump crank, wherein the sucker rod pump crank is in cinematic connection with a walking beam which is connected to a polished rod; wherein the walking beam is equipped with an angle sensor connected to the PC input and is formed to detecting position of the walking beam, wherein the PC input contains a galvanic isolation of a power supply, wherein said PC comprising: a means of the crank position detection based on the detected position of the walking beam, a means of the sucker rod pump geometry dependences calculation, a means of the motor power calculation and a counter weight system power (CWP) calculation, a means of the polished rod load or/and velocity calculation, a means of data processing and forming a surface and a down hole dynamometer card of the sucker rod pump parameters.

10. The sucker rod pump automated control system according to claim 9 wherein the means of the motor power calculation comprising a block of a stator and a rotor power losses calculation and a block of the sucker rod pump dynamic moment calculation.

Description

DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1—is a sucker rod pump structure;

[0027] FIG. 2—is an automated control system of the sucker rod pump structure;

[0028] FIG. 3—is a method of forming constructing dynamometer card (Stage 1);

[0029] FIG. 4—is a method of forming constructing dynamometer card (Stage 2);

[0030] FIG. 5—is a method of forming constructing dynamometer card (Stage 3);

[0031] FIG. 6—is a polished rod load with a pump filling rate (example 1);

[0032] FIG. 7—is a polished rod load with a pump filling rate (example 2);

[0033] FIG. 8—is a polished rod load with a pump filling rate (example 3);

[0034] FIG. 9—is an embodiment of the method of the sucker rod pump automated control and a flow control.

[0035] The following are definitions of some of the technical terms used in the detailed description of the preferred embodiments. [0036] a power balance—relation between the momentary power (MMP) and a counter weight system power (CWP) to a polished rod velocity. [0037] walking beam angle sensor—rate-of-turn sensor; encode; rotation angle sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Referring to FIG. 1, there is shown a sucker rod pump (SRP) 1 system comprises a variable speed drive (VSD) 2 equipped with a programmable controller (PC) 3 and connected with a motor 4. The motor 4 is designed as a drive for the sucker rod pump crank 5. Wherein the sucker rod pump crank 5 is in cinematic connection with a walking beam 7 through a link rod 6. Wherein the walking beam 7 is connected to a polished rod 8. The polished rod 8 provides transmission of reciprocating motion to the string of sucker rods 9 within a tubing string 10.

[0039] On one embodiment of the invention, the walking beam 7 is equipped with an angle sensor 11 connected to the PC 3 input and is formed to detecting position of the walking beam. Wherein the PC 3 input is an analog input contains a power supply galvanic isolation, which provides immunity to power-frequency magnetic fields.

[0040] The PC 3 comprising an operating means based on a central processor unit (CPU) 3.1. Referring to FIG. 2 an automated control system of the sucker rod pump comprising: a means 12 of the crank 5 position detection based on the detected position of the walking beam 7, a means 13 of the sucker rod pump 1 geometry dependences calculation, a means 14 of the motor 4 power calculation and a counter weight system 15 power (CWP) calculation, as well as means of the polished rod 8 velocity 16 and load 17 calculation. Wherein the polished rod 8 velocity and load values can be expressed through a power balance in the SRP 1 system. The calculated parameters used by a means 18 for data processing and forming a surface and a down hole dynamometer card of the sucker rod pump parameters. Said surface and the down hole dynamometer card are displayed on the screen of CP 3, or another remount control device of the SRP automated control system.

[0041] The means 14 of the motor power calculation is made with a capability of the VSD active power calculation, by usage of a block 14.1 for a stator (P.sub.ST) and a rotor (P.sub.RT) power losses calculation and a block 14.2 of the sucker rod pump dynamic moment calculation.

[0042] Also, according to the one embodiment the means 18 for the data processing and forming the dynamometer cards is made with an ability of the polisher rod load zero portion calculation at the polished rod end points. Which is leading to an accuracy of forming and displaying of dynamometer cards.

[0043] Based on the described variant of the SRP system, the method of the SRP automated control can be implemented.

[0044] At the beginning of the SRP equipment operation, providing the automated control system calibration. The calibration is performing by the operator of the SRP.

[0045] During the SRP control system settings, providing calibration of the walking beam angle sensor 11. Taking the motor torque reference value calculated on a first SRP stroke at a low motor velocity. Wherein the low motor velocity is up to 30% of nominal motor value. According to present invention said motor torque reference value showing a ratio between the motor torque average value and the sucker rod pump filling rate, wherein at least the sucker rod pump filling rate reflects changing of the polished rod load.

[0046] During the SRP commissioning, a number of parameters are also determined, the values of which remain unchanged during SRP operation and can be used in the calculation and performing of the dynamometer card. Among which, a moment of inertia formed by the motor 4 and by the counter weight system 15, an inductance and a resistance motor parameter, parameters characterizing the geometry dependences of the SRP components.

[0047] According to the present embodiment, taking a linear dimension between the crank axis 19 and an anchor point between the link rod 6 and the crank 5, a linear dimension between an anchor point of the link rod 6 and the walking beam 7 anchor point, a length of an arms of the walking beam 7, a linear dimension between the walking beam 7 axes and the crank 5 axes, as well as a masses of counter weights system 15.

[0048] Based on mentioned geometry dependences and calculated motor parameters calculating the dynamic moment which causing losses of the VFD dynamic power.

[0049] After SRP commissioning the control system is ready for exploitation. According to the present embodiment, the control method is based on the SRP dynamometer card, comprising a surface and a down hole dynamometer card (FIG. 6-8).

[0050] Based on the dynamometer card data, forming the SRP motor control signals in accordance with the sucker rod pump filling rate. Also, the SRP motor control signals can be made, based on a load or/and a velocity of the polished rod. Wherein at least the motor torque, the polished rod load or/and the velocity are calculated based on mass and geometry values of the sucker rod pump components as well the as current and voltage parameters.

[0051] Calculating the power balance (P.sub.bal) during the dynamometer card performing, wherein the motor power and the counter weight system power (CWP) excluding losses are corresponding to a power at an anchor point between the polished rod and the rod string.

[0052] According to the present invention performing of the surface dynamometer card comprising at least three main steps (FIG. 3-6), one of which determines the value of the momentary power value (MMP) necessary to reciprocate the polished rod.

[0053] At the next step, the polished rod velocity is determined, and also at the next or one of the previous steps, the crank angle (φK) is determined. At the final step, using the result of the first steps, the power balance is determined, which is displayed graphically on the PC display. It is also possible to implement the invention, in which the results are displayed at the remote workplace of the operator of the automated control system.

[0054] At the step of determining the motor momentary power Pm, (FIG. 4) necessary for the polished road reciprocating, using the means 14, for calculating the VSD active power value (P.sub.VSD), based on three-phase current (I.sub.ABC) parameters, as well as the frequency setting (f) and the calculated voltage U value, in particular, the voltage vector angle (θ). Wherein changing the frequency setting (f) value relative to the sucker rod pump filling rate. After calculating active power value (P.sub.VSD), taking the momentary power value required for polished rod reciprocation by excluding the losses.

[0055] In the above-mentioned embodiment of the invention, the SRP system power losses comprise a stator and a rotor loss of the motor, as well as the motor velocity change losses (P.sub.V) (acceleration and braking of the system) and a mechanical loss. The stator losses are determined based on an amplitude value of the stator current and the stator resistance. The rotor losses are determined by using the rotor current calculated values as well as inductance and voltage. The acceleration/resistance losses take into account the parameters characterized by the dynamic moment of the system, which takes into account the geometric dependences between the SRP components, as well as the moments of inertia of the electric motor (Me) and the counter weight system power (CWP) (Pw), which are recorded into the PC memory block 21 during the commissioning step.

[0056] According to a preferred embodiment of the invention, the PC also contains a block of 20 of a smoothing filter (low-pass filters (LPF)), which allows forming the dynamometer card without interference of current harmonics and mechanical vibrations of the SRP system. Getting the MMP value required for polished road reciprocation after passing signals through the block 20 of smoothing filters.

[0057] At the second step (FIG. 5), calculating the polished rod 8 velocity (V.sub.PR). Wherein calculating the crank angle (φK) using the parameters of the SRP geometric dependences which are determined through the measured walking beam 7 angle (φB). The polished rod 8 displacement (S.sub.PR) also calculated through the mentioned above values. During the polished rod 8 velocity calculation excluding a near-zero velocity values (V.sub.PR≠0) at the walking beam 7 extreme points.

[0058] Calculating the load zero portion at the polished rod end points, wherein the load zero portion is forming a part of the polished road stroke length. Wherein forming the polished rod load constant value at an input/output of the zero portion, and forming an intermediate load value as a calculated mathematic value. Such variant, allows additionally take into account possible inaccuracies in the values of the SRP geometric dimensions.

[0059] On (FIG. 6) is showing the final step of forming the surface or/and down hole dynamometer card. The dynamometer card is forming through the power balance of the SRP 1 system by using means 18 of the CPU 3.1. In additional taking into account the motor momentary power value (MMP) calculated on the first steps, and a counter weight system power (Pw) during each reciprocating stroke of the polished rod 8. Wherein, also counting the crank angle (φK), the polished rod velocity (V.sub.PR) and displacement (S.sub.PR). Wherein a visualization rate is depending on the time of one polished rod reciprocating cycle, calculated between two successive upstrokes.

[0060] The obtained dynamometer cards (FIG. 6-8) are used by the SRP control system to generate control signals depending on the sucker rod pump filling rate. In particular, (FIG. 6) shows the results of the SRP system operation according to the claimed method, wherein when the polished rod displacement graph 22 shows the SRP filling rate (FIG. 6) dropping down equal to 56% which leads to a related polished rod load showed at graph 23. As we can see on FIG. 6 the estimated surface 22.1 dynamometer card is close to the measured surface 22.2 dynamometer card as well as down hole dynamometer card 22.3.

FIG. 6 shows that changing the frequency setting and increasing the polished rod velocity V.sub.PR, are leading the optimal filling rate (FIG. 8).

[0061] The dynamic changes of the SRP system operation are shown on (FIG. 9). An example of the SRP control system operation with the flow rate optimization are shown (graph 24 depending on changing the motor velocity value (graph 25). In the given example (FIG. 9), before the start of recording, the filling rate was set to 80% and the SRP system is reaching the maximum pumping of 4.16 pumps/min (65 Hz)—the moment the recording started. Further, at the time 11.46.40, the filling rate set was increased to 90%. After that, the SRP control system providing the flow rate optimization mode. The flow rate optimization mode anticipating a cyclic work with providing an optimized flow rate and maintaining the SRP filling rate.

[0062] The SRP filling rate, in one of the invention embodiments, also obtained by calculating the motor torque average value per each cycle (calculated between two successive upstrokes). In this option, the calculation of the motor torque average value calculated at low velocity, equal to 30% of the nominal value, and is taken the pump filling rate as 100%. Next, during each period of the SRP operation, the current average torque is comparing to the reference value, based on the achieved result calculating the percentage relation, which shows the percentage of the SRP filling (the dependence is shown in FIG. 6-8).

[0063] The implementation of the described invention contributes to the achievement of the claimed technical result, increasing the accuracy of measuring the of the SRP characteristics, ensuring real time well flow rate optimization, as well as a continuity of the technological process with the possibility of changing the main parameters.