CN103410475A - Environment-friendly annular continuous dosing automatic device for oil-gas wells and dosing method - Google Patents

Abstract

An environment-friendly continuous dosing automatic control device and method for annulus of oil and gas wells. The bottom of the pressure vessel is connected to the sewage outlet; The needle and the resistance probe are connected with the resistance measuring instrument in the automatic controller; the power supply of the automatic controller is connected with the solar energy; the inlet of the pressure balance tube communicates with the upper part of the pressure vessel; the outlet of the pressure balance tube communicates with the casing joint, and The operation method of the dosing process includes: 1) Calculate the dosing amount of the oil and gas well according to the designed formula; 2) Select the diameter of the liquid flow valve e in the flow regulator according to the dosing amount; 3) Install and adjust the device according to the designed program ; 4) Replenish the agent through the external diesel engine pump through the sewage outlet. The invention has the advantages of simple maintenance, almost zero failure rate, easy operation, and can adapt to dosing in oil well and gas well annulus under various oil field production environments.

Description

Environment-friendly oil and gas well annulus continuous dosing automatic control device and dosing method

technical field

The invention relates to the technical field of controllable and continuous dosing of various liquid medicaments in the annulus of oil wells and gas wells, in particular to an environment-friendly automatic control device and method for continuous dosing in the annulus of oil and gas wells.

Background technique

The current oil well annulus dosing method adopts the plunger pump. There are two ways to provide power. One is to use the high voltage at the oil well site to convert it into 200v or 380v voltage through a transformer, and the other is to use the pump The up and down movement of the sucker rod of the oil unit makes intermittent impacts. Due to the low dosing volume of a single oil well on site (the dosing volume of a general oil well is no more than 3kg/d, which is equivalent to 2L/min), it is easy to cause pump blockage when dosing with a small flow plunger pump, and the dosing volume is difficult to control. Design scope, pump drive failure phenomenon, poor environmental resistance, high failure rate, high maintenance cost, and it is difficult to maintain in time in the field, which affects normal dosing. At present, gas wells cannot use electric plunger pumps for dosing because there is no power supply at the well site. There is no special dosing device for gas well annulus dosing, and the gas well annulus dosing process has not been realized.

Contents of the invention

In order to overcome the above-mentioned defects in the prior art, the object of the present invention is to provide an environment-friendly oil and gas well annulus continuous dosing automatic control device and a dosing method, which completely overcomes the shortcomings of using plunger pumps for dosing in the annulus of existing oil wells, and can Solve the needs of dosing in the annulus of gas wells; the device not only has low cost, simple maintenance, but also has almost zero failure rate, is easy to operate, and can adapt to dosing in the annulus of oil wells and gas wells in various environments in oil field production.

In order to achieve the above object, the technical solution of the present invention is achieved in that:

The environment-friendly automatic control device for continuous dosing in the annulus of oil and gas wells includes a pressure-resistant container 1, which is composed of at least two tubular pressure-resistant containers; the bottom of the pressure-resistant container 1 is connected with a sewage outlet 8; The outlet pipeline at the bottom of the container 1 is connected to the valve 9 and the flow regulator 2, the outlet of the flow regulator 2 is connected to the outlet valve 10, and the upper part of the pressure-resistant container 1 is connected with the vent 7 and the resistance probe 5; the solar energy 4 is installed in the pressure-resistant container 1; the automatic controller 3 is installed on one side of the pressure vessel 1; the resistance probe 5 is connected with the resistance measuring instrument in the automatic controller 3; the power supply of the automatic controller 3 is connected with the solar energy 4; the pressure balance tube 6 The inlet communicates with the upper part of the pressure vessel 1; the outlet of the pressure balance pipe 6 is connected to the outlet valve 10, and the outlet of the outlet valve 10 is connected to the casing joint 12, and the pressure balance pipe 6 is provided with a balance pipe valve 11;

The flow regulator 2 includes a sealing pipe d, and there are threads at both ends of the sealing pipe d, the inlet is connected to the pressure vessel 1, the outlet is connected to the casing joint 12, and a magnetic ring b is connected to the outer wall of the sealing pipe d , the contact surface between the magnetic ring b and the moving track c is designed with a groove, and a motor a and the moving track c are installed outside the sealing tube d, and a baffle j with a hole is installed in the sealing tube d, on the baffle j There is an opening channel h and a bearing g is installed, the magnetic needle f can reciprocate in the bearing g, and a liquid flow valve e whose flow rate is controlled by the aperture is installed in the sealing pipe string d.

The flow regulator 2 includes a sealing column d, and there are threads at both ends of the sealing column d, the inlet is connected to the pressure vessel 1, the outlet is connected to the sleeve joint 12, and a magnetic ring b is connected to the outer wall of the sealing column. A DC electromagnetic coil a and a DC electromagnetic coil c are installed on the left and right sides of the magnetic ring b, and a baffle j with holes is installed in the sealing column d. The baffle j has an opening channel h and a bearing g , the magnetic needle f can reciprocate in the magnetic needle bearing g, and the liquid flow valve e whose flow rate is controlled by the aperture is installed in the sealing column d.

The flow regulator 2 includes a sealing string d, with threads at both ends of the sealing string d, the inlet is connected to the pressure vessel 1, the outlet is connected to the casing joint 12, and a DC electromagnetic coil a is installed on the upper part of the sealing string d, A baffle j with a hole is installed in the sealing column d, and there is an opening channel h on the baffle j, the magnetic needle f can reciprocate up and down in the middle hole of the baffle j, and a hole controlled by the aperture is installed in the sealing column d flow valve e.

The dosing method based on the above-mentioned environment-friendly oil and gas well annulus continuous dosing automatic control device includes the following steps:

(1) Determine the dosing amount of oil well or gas well: the calculation formula of dosing amount of oil well is M=1.35×C×Q×N, M is the dosing amount of oil well L/h; The concentration of etchant in mg/L, Q is the liquid production rate of the oil well in m ³ /h, N is the water cut in % of the oil well; the formula for calculating the dosing amount of the gas well is M=1.2×C×Q _water + 2×10 ^-5 ×C ×Q _gas , M is the dosage L/h of the gas well, C is the corrosion inhibitor concentration mg/L evaluated according to the standard method, Q _water is the liquid production rate of the gas well m ³ /h, and Q _gas is the gas production rate of the gas well ;

(2) According to the dosage L/h of the oil well, select the liquid flow valve e with the corresponding diameter calibrated by the indoor standard method;

(3) Install the selected liquid flow valve e in the flow regulator 2;

(4) Connect the casing joint 12 of the environment-friendly oil and gas well annulus continuous dosing automatic control device to the casing valve of the oil or gas well, and the valve 9, the outlet valve 10 and the balance pipe valve 11 are used to start the automatic controller 3 Make it run at designed intervals;

(5) After all the chemicals in the pressure-resistant container 1 in the device have been added, connect the pipeline of the diesel engine dosing pump to the sewage outlet 8, open the valve of the sewage outlet 8, close the valve 9, close the flow regulator 2, and open the automatic controller 3 Resistance tester, start the diesel engine dosing pump to replenish the container, stop replenishing the drug when the resistance tester indicates that the drug in the container reaches the liquid level, close the valve 8 of the sewage outlet, open the valve 9, restart the flow regulator 2 and the automatic Controller 3, adjust or check whether the automatic controller is running normally and whether the time interval is correct, enter the normal dosing, when the medicine in the container is added again, repeat the same operation.

The invention has the advantages that it completely overcomes the deficiency of plunger pump dosing in the annulus of the existing oil well, and solves the need for dosing in the annulus of the gas well. The device not only has low cost and simple maintenance, but also has almost zero failure rate, is easy to operate, and can adapt to the annular dosing of oil wells and gas wells in various environments of oil field production.

Description of drawings

Fig. 1 is a structural schematic diagram of an environment-friendly oil and gas well annulus continuous dosing automatic control device of the present invention; wherein the pressure vessel 1 can determine the volume and number of the pressure vessel 1 according to the on-site oil and gas well pressure and the amount of dosing.

Fig. 1-1 is a schematic diagram of the first structure of the flow regulator 2 in the environmental-friendly oil and gas well annulus continuous dosing automatic control device of the present invention; it consists of a DC motor a (which can run alternately in positive and negative directions), a magnetic ring b, and a moving track c (made of stainless steel), sealing column d (made of stainless steel), liquid flow valve e, magnetic needle f (composed of strong magnetic rods wrapped in stainless steel), bearing g, channel h, and baffle j.

Fig. 1-2 is the 2nd kind of structure schematic diagram of the flow regulator 2 in the environmental protection type oil and gas well annulus continuous dosing automatic control device of the present invention; Column d (made of stainless steel), liquid flow valve e, magnetic needle f (composed of strong magnetic rods wrapped in stainless steel), bearing g, channel h, and baffle j.

Fig. 1-3 is the third structural diagram of the flow regulator 2 in the environmental-friendly oil and gas well annulus continuous dosing automatic control device of the present invention; it consists of a DC magnetic coil a, a sealing pipe string d (made of stainless steel), and a liquid flow valve e, magnetic needle f (composed of strong magnetic rods wrapped in stainless steel), channel h, and baffle j.

Fig. 2 is a schematic diagram of the connection process between the environmental-friendly oil and gas well annulus continuous dosing automatic control device and the oil and gas well annulus casing of the present invention; after the container in the device is filled with medicament, a diesel engine dosing pump is used to replenish the medicament to the container.

Detailed ways

Referring to Fig. 1, the environment-friendly automatic control device for continuous dosing in the annulus of oil and gas wells includes a pressure-resistant container 1, which is composed of at least two tubular pressure-resistant containers; the bottom of the pressure-resistant container 1 is connected with a sewage outlet 8. The outlet pipeline at the bottom of the pressure vessel 1 is connected to the valve 9 and the flow regulator 2, the outlet of the flow regulator 2 is connected to the outlet valve 10, and the upper part of the pressure vessel 1 is connected to the vent 7 and the resistance probe 5; the solar energy 4 is installed On the top of the pressure vessel 1; the automatic controller 3 is installed on one side of the pressure vessel 1; the resistance probe 5 is connected with the resistance measuring instrument in the automatic controller 3; the power supply of the automatic controller 3 is connected with the solar energy 4; The inlet of the balance pipe 6 communicates with the upper part of the pressure-resistant container 1; the outlet of the pressure balance pipe 6 communicates with the casing joint 12, and the pressure balance pipe 6 is provided with a balance pipe valve 11;

A pressure vessel 1 is composed of a collection of multiple tubular pressure vessels, which may be N (N≥2).

A flow regulator 2 is equipped with an anti-theft device to prevent damage to the flow regulator. There are 3 types of flow regulator designs:

Referring to Figure (1-1), this embodiment consists of a DC motor a (which can run alternately in forward and reverse directions), a magnetic ring b, a moving track c (made of stainless steel), a sealing column d (made of stainless steel), a liquid flow valve e, and a magnetic needle f (composed of strong magnetic rods wrapped in stainless steel), bearing g, channel h, and baffle j.

The flow regulator 2 includes a sealing string d, with threaded fasteners at both ends of the sealing string d, the inlet is connected to the pressure vessel 1, the outlet is connected to the casing joint 12, and a magnetic ring b is connected to the outer sleeve of the sealing string d, and the magnetic ring b A groove is designed on the contact surface between the ring b and the moving track c, and a motor a and the moving track c are installed outside the sealing pipe string d, and a baffle j with a hole is installed in the sealing pipe string d, and the baffle j has an opening The hole channel h is installed with a bearing g, the magnetic needle f can reciprocate in the bearing g, and the liquid flow valve e whose flow rate is controlled by the hole diameter is installed in the sealing column d, the movement of the motor a drives the moving track c to reciprocate, and the moving The track c drives the magnetic ring to reciprocate on the sealing pipe string. The reciprocating motion of the magnetic ring drives the reciprocating motion of the magnetic needle. The reciprocating motion of the magnetic needle plays the role of dredging the e channel of the liquid flow valve and controlling the liquid flow rate of the e channel of the liquid flow valve.

The principle adopted: install the outlet of the dosing device on the upper part of the sleeve valve, rely on the gravity of the liquid medicine to automatically flow into the sleeve, and set up a balance pipe on the upper part of the dosing container to connect the inlet of the sleeve to balance the container The negative pressure generated by the reduction of traditional Chinese medicine, and then use the aperture size of the liquid flow valve e and the reciprocating motion of the magnetic needle at a certain frequency to control the dosing flow; since the aperture of the liquid flow valve e is very small, in order to prevent the blockage of the liquid flow valve channel, the motor The rotation is transformed into the reciprocating movement of the magnetic ring, which drives the magnetic needle to reciprocate in the liquid flow valve e, so as to dredge the channel of the liquid flow valve e and prevent blockage.

Referring to Figure (1-2), this embodiment consists of a left DC electromagnetic coil a, a magnetic ring b, a right DC electromagnetic coil c, a sealing column d (made of stainless steel), a liquid flow valve e, and a magnetic needle f (a strong magnetic coil wrapped in stainless steel) Composed of rods), bearing g, channel h, baffle j.

The flow regulator 2 includes a sealing string d, and there are threads at both ends of the sealing string d. A DC electromagnetic coil a and a DC electromagnetic coil c are installed on the left and right sides of the magnetic ring b, and a baffle j with a hole is installed in the sealing column d. The baffle j has an opening channel h and a magnetic needle bearing g , the magnetic needle f can reciprocate in the magnetic needle bearing g, and the liquid flow valve e whose flow rate is controlled by the aperture is installed in the sealing pipe d, the alternating intermittent energization of the DC electromagnetic coil generates an electromagnetic field, and the magnetic ring moves reciprocatingly on the sealing pipe , the reciprocating movement of the magnetic ring drives the reciprocating movement of the magnetic needle, and the reciprocating movement of the magnetic needle plays the role of dredging the e channel of the liquid flow valve and controlling the liquid flow rate of the e channel of the liquid flow valve.

The principle adopted: install the outlet of the dosing device on the upper part of the sleeve valve, rely on the gravity of the liquid medicine to automatically flow into the sleeve, and set up a balance pipe on the upper part of the dosing container to connect the inlet of the sleeve to balance the container The negative pressure generated by the reduction of the traditional Chinese medicine, and then use the aperture size of the liquid flow valve e and the reciprocating motion of the magnetic needle at a certain frequency to control the dosing flow rate; since the aperture of the liquid flow valve e is very small, in order to prevent the channel of the liquid flow valve from being blocked, a left and right direct current is used. The magnetic coil is energized alternately and intermittently to generate an electromagnetic field, which absorbs the magnetic ring to reciprocate, and the magnetic ring drives the magnetic needle to reciprocate in the liquid flow valve e, dredging the channel of the liquid flow valve e to prevent blockage.

Referring to Figures 1-3, this embodiment consists of a DC electromagnetic coil a, a sealed pipe d (made of stainless steel), a liquid flow valve e, a magnetic needle f (composed of a strong magnetic rod wrapped in stainless steel), a channel h, and a baffle j.

The flow regulator 2 includes a sealing string d, with threads at both ends of the sealing string d, the inlet is connected to the pressure vessel 1, the outlet is connected to the casing joint 12, and a DC electromagnetic coil a is installed on the upper part of the sealing string d, A baffle j with a hole is installed in the sealing column d, and there is an opening channel h on the baffle j, the magnetic needle f can reciprocate up and down in the middle hole of the baffle j, and a hole controlled by the aperture is installed in the sealing column d The liquid flow valve e of the flow rate; the magnetic needle can reciprocate up and down in the middle hole of the baffle, and the liquid flow valve e whose flow rate is controlled by the aperture is installed in the sealing column. The intermittent energization of the DC electromagnetic coil generates an electromagnetic field, and the magnetic needle moves upward. When the DC electromagnetic coil is powered off, the magnetic field disappears and the magnetic needle moves down by gravity, and the up and down reciprocating movement of the magnetic needle plays the role of dredging the e-channel of the liquid flow valve and controlling the liquid flow rate of the e-channel of the liquid flow valve.

The principle adopted: install the outlet of the dosing device on the upper part of the sleeve valve, rely on the gravity of the liquid medicine to automatically flow into the sleeve, and set up a balance pipe on the upper part of the dosing container to connect the inlet of the sleeve to balance the container The negative pressure generated by the reduction of traditional Chinese medicine, and then use the aperture size of the liquid flow valve e and the reciprocating motion of the magnetic needle at a certain frequency to control the dosing flow; since the aperture of the liquid flow valve e is very small, in order to prevent the blockage of the liquid flow valve channel, a DC magnetic The coil is energized intermittently. When energized, an electromagnetic field is generated to attract the magnetic needle to move upward. When the power is turned off, the magnetic field disappears and the magnetic needle moves downward by gravity. The magnetic needle moves up and down in the liquid flow valve e to dredge the channel of the liquid flow valve e to prevent blockage.

An automatic controller 3 is used to control the energization frequency of the flow regulator, control the resistance tester, control the motor speed and measure the pressure, etc.

A solar energy 4 is provided with an anti-theft device to supply power to the automatic controller 3 .

A resistance probe 5, the resistance measuring instrument in the automatic controller 3 tests the signal change of the probe to determine whether the medicament in the container is replenished in place.

A pressure balance pipe 6 is used to balance the pressure of the pressure vessel and the annular space of the casing.

A vent port 7 is used to vent the internal pressure of the device during device maintenance and oil and gas well operations.

A blowdown outlet 8 is used for replenishing the medicine to the device while taking into account blowdown.

A casing joint 12 is used to connect the device with casing valves of oil and gas wells.

A plurality of valves, including valve 9, outlet valve 10 and balance pipe valve 11, are used for the opening operation of the device and the maintenance of the flow regulator, etc.

The dosing method based on the above-mentioned environment-friendly oil and gas well annulus continuous dosing automatic control device includes the following steps:

(1) Determine the dosing amount of oil well or gas well: the calculation formula of dosing amount of oil well is M=1.35×C×Q×N, M is the dosing amount of oil well L/h; The concentration of etchant in mg/L, Q is the liquid production rate of the oil well in m ³ /h, N is the water cut in % of the oil well; the formula for calculating the dosing amount of the gas well is M=1.2×C×Q _water + 2×10 ^-5 ×C ×Q _gas , M is the dosage L/h of the gas well, C is the corrosion inhibitor concentration mg/L evaluated according to the standard method, Q _water is the liquid production rate of the gas well m ³ /h, and Q _gas is the gas production rate of the gas well ;

(2) According to the dosage L/h of the oil well, select the liquid flow valve e with the corresponding diameter calibrated by the indoor standard method;

(3) Install the selected liquid flow valve e in the flow regulator 2;

(4) Referring to Figure 2, connect the casing joint 12 of the environmental-friendly oil and gas well annulus continuous dosing automatic control device to the casing valve of the oil or gas well, valve 9, outlet valve 10 and balance pipe valve 11, start the flow rate Regulator 2, which adjusts the automatic controller 3 to operate according to the required time intervals,

(5) Referring to Figure 2, after all the chemicals in the pressure-resistant container 1 in the device have been added, connect the pipeline of the diesel engine dosing pump to the sewage outlet 8, open the valve of the sewage outlet 8, close the valve 9, and close the flow regulator 2 , turn on the resistance tester in the automatic controller 3, start the diesel engine dosing pump to replenish the container, stop replenishing the drug when the resistance tester indicates that the drug in the container reaches the liquid level, close the valve of the sewage outlet 8, open the valve 9, and restart Start the flow regulator 2 and the automatic controller 3, adjust or check whether the automatic controller is running normally and whether the time interval is correct, enter the normal dosing, when the medicine in the container is added again, repeat the same operation.

Claims (5)

1. The environment-friendly automatic control device for continuous dosing in the annulus of oil and gas wells is characterized in that it includes a pressure-resistant container (1), and the pressure-resistant container (1) is composed of at least two tubular pressure-resistant containers; the pressure-resistant container ( The bottom of 1) is connected with a sewage outlet (8); the outlet pipeline at the bottom of the pressure vessel (1) is connected to the valve (9) and the flow regulator (2), and the outlet of the flow regulator (2) is connected to the outlet valve (10). The upper part of the pressure vessel (1) is connected with a vent (7) and a resistance probe (5); the solar energy (4) is installed on the upper part of the pressure vessel (1); the automatic controller (3) is installed in the pressure vessel ( 1); the resistance probe (5) is connected to the resistance measuring instrument in the automatic controller (3); the power supply of the automatic controller (3) is connected to the solar energy (4); the inlet of the pressure balance tube (6) is connected to the The upper part of the pressure-resistant container (1) is connected; the outlet of the pressure balance pipe (6) is connected to the outlet valve (10), and the outlet of the outlet valve (10) is connected to the casing joint (12), and the pressure balance pipe (6) is provided with Balance pipe valve (11). the 2. The environment-friendly automatic control device for continuous dosing in the annulus of oil and gas wells according to claim 1, characterized in that, the flow regulator (2) includes a sealing pipe string (d), two sealing pipe strings (d) There is a screw thread at the end, the inlet is connected with the pressure vessel (1), the outlet is connected with the casing joint (12), and a magnetic ring (b) is connected outside the pipe wall of the sealed pipe string (d), and the magnetic ring (b) is connected with the moving track ( c) The contact surface is designed with grooves, a motor (a) and a moving track (c) are installed outside the sealing pipe string (d), and a baffle plate (j) with holes is installed inside the sealing pipe string (d), There is an opening channel (h) on the baffle plate (j) and a bearing (g) is installed. The magnetic needle (f) can reciprocate in the bearing (g), and a flow control device controlled by the hole diameter is installed in the sealing tube (d). Flow valve (e). the 3. The environment-friendly automatic control device for continuous dosing in the annular space of oil and gas wells according to claim 1, characterized in that the flow regulator (2) includes a sealing pipe string (d), two sealing pipe strings (d) There is a threaded thread at the end, the inlet is connected to the pressure vessel (1), the outlet is connected to the casing joint (12), and a magnetic ring (b) is connected to the outer wall of the sealed pipe column, and a magnetic ring (b) is installed on the left and right sides of the magnetic ring (b). DC electromagnetic coil (a) and DC electromagnetic coil (c), a baffle plate (j) with a hole is installed in the sealing pipe string (d), and the baffle plate (j) has a hole channel (h) and is installed The bearing (g), the magnetic needle (f) can reciprocate in the magnetic needle bearing (g), and the liquid flow valve (e) whose flow rate is controlled by the hole diameter is installed in the sealing pipe string (d). the 4. The environment-friendly automatic control device for continuous dosing in the annular space of oil and gas wells according to claim 1, characterized in that, the flow regulator (2) includes a sealing pipe string (d), two sealing pipe strings (d) There is a threaded thread at the end, the inlet is connected to the pressure vessel (1), the outlet is connected to the casing joint (12), a DC electromagnetic coil (a) is installed on the upper part of the sealing string (d), and a belt with The baffle plate (j) of the hole has an opening channel (h) on the baffle plate (j), and the magnetic needle (f) can reciprocate up and down in the middle hole of the baffle plate (j). Orifice-controlled flow valve (e). the 5. The dosing method based on the environmental protection type oil and gas well annulus continuous dosing automatic control device described in right 1, is characterized in that, comprises the following steps: (1) Determine the dosing amount of oil well or gas well: the calculation formula of dosing amount of oil well is M=1.35×C×Q×N, M is the dosing amount of oil well L/h; The concentration of etchant in mg/L, Q is the liquid production rate of the oil well in m ³ /h, N is the water cut in % of the oil well; the formula for calculating the dosing amount of the gas well is M=1.2×C×Q _water + 2×10 ^-5 ×C ×Q _gas , M is the dosage L/h of the gas well, C is the corrosion inhibitor concentration mg/L evaluated according to the standard method, Q _water is the liquid production rate of the gas well m ³ /h, and Q _gas is the gas production rate of the gas well ; (2) According to the dosage L/h of the oil well, select the liquid flow valve e with the corresponding diameter calibrated by the indoor standard method; (3) Install the selected liquid flow valve e in the flow regulator 2; (4) Connect the casing joint (12) of the environment-friendly oil and gas well annulus continuous dosing automatic control device to the casing valve of the oil well or gas well, the valve (9), the outlet valve (10) and the balance pipe valve (11) ), start the flow regulator (2), start the automatic controller (3) to run according to the designed time interval; (5) After all the chemicals in the pressure vessel (1) in the device have been added, connect the pipeline of the diesel engine dosing pump to the sewage outlet (8), open the valve of the sewage outlet (8), close the valve (9), and close the flow Regulator (2), turn on the automatic controller (3) resistance tester, start the diesel engine dosing pump to replenish the container, stop replenishing the drug when the resistance tester indicates that the drug in the container reaches the liquid level, and close the sewage outlet (8) Valve, open the valve (9), restart the flow regulator (2) and the automatic controller (3), adjust or check whether the automatic controller is running normally and whether the time interval is correct, enter the normal dosing, when the medicine in the container is filled again After adding, repeat the same operation. the

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