CN106439502B - Slug flow on-Line Monitor Device and removing method in a kind of standpipe - Google Patents

Abstract

The invention relates to an online monitoring device for slug flow in a standpipe and a method for eliminating it. An ERT sensor with adjustable length is designed to closely fit the standpipe wall to ensure the accuracy of imaging; the ERT sensors are evenly distributed on the standpipe at the same central angle The outer wall is combined with a certain image restoration algorithm to obtain a real-time image of slug flow to realize online monitoring of slug flow in the riser; the clamping structure and compression structure of the ERT sensor fixing ring are designed to meet the environmental conditions of high pressure and low temperature in the ocean; through data The transmission system transmits the obtained data to the central control room of the offshore production platform, combined with the slug flow elimination method, to provide data support for the adjustment of the valve action of the terminal production separator.

Description

An on-line monitoring device and elimination method for slug flow in a standpipe

technical field

The invention relates to an online monitoring device for slug flow in a standpipe and a method for eliminating it, belonging to the technical field of marine gathering and transportation.

Background technique

In the process of offshore oil and gas exploitation, the riser is used to connect the subsea mixed transportation pipeline with the offshore central processing platform. Slug flow is easy to occur in the riser system, and the risk of transportation is high.

The slug flow sharply increases the pressure drop in the standpipe, leading to an increase in the back pressure at the wellhead and a reduction in the production of oil and gas wells. Gas and liquid flow out alternately at the outlet of the standpipe, causing the downstream production separator to overflow or stop flow. Severe pressure fluctuations aggravate the corrosion of the standpipe wall, causing pipeline vibration, and cavitation of the booster equipment on the treatment platform. The temperature drop effect occurs during the gas eruption process, leading to wax deposition on the pipe wall and the formation of hydrates.

In the open literature, foreign researchers have not proposed the design scheme of the online monitoring device for slug flow in the standpipe, and most domestic researchers are still in the theoretical research stage, and there are no reports of relevant tangible research results.

The methods for eliminating slug flow in the standpipe mainly include: (1) Gas injection at the bottom of the standpipe to reduce the static pressure of the gas-liquid mixing column in the standpipe and enhance the liquid-carrying capacity of the gas. (2) Subsea gas-liquid production separator is adopted. (3) Use a multiphase pump to pressurize on the seabed or on the platform. (4) Throttling at the top of the riser. (5) Increase back pressure. The implementation of the above method does not carry out on-line monitoring of slug flow in the standpipe, lack of relevant data support for slug flow, and the effect of slug flow elimination is limited.

Therefore, it is of great significance to design the on-line monitoring device for slug flow in the standpipe and study the slug flow elimination method based on the function of the on-line slug flow monitoring device in the standpipe to ensure the safe operation of the riser system and oil and gas processing equipment.

Contents of the invention

The purpose of the present invention is to provide an on-line monitoring device for slug flow, which can realize the visual measurement of slug flow in the standpipe and ensure the stable operation of the ocean gathering and transportation pipeline.

The present invention mainly solves the following problems:

(1) Design the ERT sensor, and set the spring in the sensor to realize the free expansion and contraction of the sensor, and closely fit the outer wall of the riser;

(2) Design the clamping structure and compression structure of the sensor fixing ring. The compression structure is made of stainless steel A2-70 material, and the elastic clamping structure is made of polytetrafluoroethylene material to meet the environmental conditions of high pressure and low temperature in the ocean;

(3) ERT sensors are evenly distributed on the outer wall of the pipeline at the same central angle, combined with a certain image restoration algorithm to obtain a real-time image of slug flow, and realize online monitoring of slug flow in the riser;

(4) Based on the slug flow elimination method based on the function of the slug flow online monitoring device in the standpipe, the valve action of the production separator at the end is adjusted to realize the slug flow elimination.

In order to achieve the above object, the technical solution of the present invention is as follows.

An on-line monitoring device and elimination method for slug flow in a standpipe, characterized in that it includes a first ERT sensor 11, a second ERT sensor 12, a third ERT sensor 13, a fourth ERT sensor 14, a fifth ERT sensor 15, a Six ERT sensors 16, first fixing bolt 211, second fixing bolt 212, third fixing bolt 221, fourth fixing bolt 222, fifth fixing bolt 231, sixth fixing bolt 232, seventh fixing bolt 241, eighth fixing bolt Bolt 242 , ninth fixing bolt 251 , tenth fixing bolt 252 , eleventh fixing bolt 261 , twelfth fixing bolt 262 , sensor fixing ring 3 , standpipe outer wall 4 , standpipe inner wall 5 .

The sensor fixing ring 3 fixes the first ERT sensor 11, the second ERT sensor 12, the third ERT sensor 13, the fourth ERT sensor 14, the fifth ERT sensor 15, and the sixth ERT sensor 16 in the same central angle. Standpipe outer wall 4, the first fixing bolt 211 and the second fixing bolt 212 are inserted into the sensor fixing ring 3 to fix the first ERT sensor 11, and the third fixing bolt 221 and the fourth fixing bolt 222 are inserted into the sensor fixing ring 3. The sensor fixing ring 3 fixes the second ERT sensor 12, the fifth fixing bolt 231 and the sixth fixing bolt 232 are inserted into the sensor fixing ring 3, fixing the third ERT sensor 13, and the seventh fixing The bolt 241 and the eighth fixing bolt 242 are inserted into the sensor fixing ring 3 to fix the fourth ERT sensor 14, and the ninth fixing bolt 251 and the tenth fixing bolt 252 are inserted into the sensor fixing ring 3 to fix the fourth ERT sensor 14. The fifth ERT sensor 15, the eleventh fixing bolt 261 and the twelfth fixing bolt 262 are inserted into the sensor fixing ring 3 to fix the sixth ERT sensor 16, and the outer wall 4 of the riser is concentric with the inner wall 5 of the riser .

Further, the first ERT sensor 11 , the second ERT sensor 12 , the third ERT sensor 13 , the fourth ERT sensor 14 , the fifth ERT sensor 15 and the sixth ERT sensor 16 are of the same type and specification.

Further, the first fixing bolt 211, the second fixing bolt 212, the third fixing bolt 221, the fourth fixing bolt 222, the fifth fixing bolt 231, the sixth fixing bolt 232, the seventh fixing bolt 241, the eighth fixing bolt The bolt 242 , the ninth fixing bolt 251 , the tenth fixing bolt 252 , the eleventh fixing bolt 261 , and the twelfth fixing bolt 262 are of the same type and specification, and are fixed in the same way in the sensor fixing ring 3 .

Further, the inner spring 102 of the first ERT sensor 11 connects the base 101 with the sensor patch 103 , and the spring 102 exerts pressure on the sensor patch 103 .

Further, between the fifth fixing bolt 231 and the sixth fixing bolt 232 is a compression structure 234 and an elastic clamping structure 235, the compression structure 234 and the elastic clamping structure 235 form an installation channel, and the second Three ERT sensors 13 are fixed.

Further, the installation channel formed by the pressing structure 234 and the elastic clamping structure 235 has the same diameter as the third ERT sensor 13 .

Further, the pressing structure 234 is made of stainless steel A2-70, and the elastic clamping structure 235 is made of polytetrafluoroethylene.

The on-line monitoring device for slug flow in the standpipe further includes the slug flow elimination method adopted by the above-mentioned device:

a: Based on the images of the fluid in the standpipe provided by the first slug flow on-line monitoring device 19, the second slug flow on-line monitoring device 20, and the third slug flow on-line monitoring device 21, determined by the first pressure sensor 18 at the bottom of the standpipe 30 The pressure threshold P ₁ when the slug flow is just formed;

b: When the first pressure sensor 18 measures the pressure value _P2 at the bottom of the standpipe 30 to be greater than the pressure threshold _P1 , the opening of the first valve 28 is increased, the gas phase flow rate in the standpipe 30 increases, and the slug flow pattern changes to eliminate For the purpose of slug flow, when the first pressure sensor 18 measures the pressure value _P2 at the bottom of the standpipe 30 is less than the pressure threshold _P1 , no slug flow occurs, and the opening of the first valve 28 is reduced;

c: According to the above steps a and b, the opening of the first valve 28 is determined by the pressure threshold P ₁ and the pressure value P ₂ at the bottom of the riser 30 measured by the first pressure sensor 18;

d: The production separator 29 is provided with a first liquid level gauge 31 and a second liquid level gauge 32. When the liquid level is higher than the position of the first liquid level gauge 31, the opening degree of the second valve 37 is increased, and the liquid level is lower than that of the first liquid level gauge 31. When the second liquid level gauge 32 is at the position, close the second valve 37 until the liquid level increases to the position of the second liquid level gauge 32 again, and open the second valve 37;

e: When there is no slug flow in the standpipe 30, the gas phase pressure in the production separator 29 is measured by the second pressure sensor 24, and the data is fed back to the second controller 23 to control the opening of the first valve 28 and adjust the production pressure in the separator 29;

f: When slug flow occurs in the standpipe 30, the second controller 23 fails, and the first controller 25 receives the pressure information at the bottom of the standpipe 30 to control the opening of the first valve 28, and the first controller 25 is a PID controller.

The beneficial effects of the invention are:

(1) On-line monitoring devices for slug flow are installed at the bottom, middle and upper parts of the standpipe to realize real-time monitoring of the flow pattern at key points of the standpipe and generate images of the three-phase distribution of oil, gas and water in the pipe;

(2) The sensor is fixed in a circular shape with the same central angle through the high-pressure resistant and low-temperature resistant sensor fixing ring, which provides guarantee for the normal operation of the sensor under the harsh conditions of the ocean;

(3) The on-line monitoring device for slug flow in the standpipe provides image and data support for the adjustment of the valve action of the terminal production separator, combined with the slug flow elimination method, the elimination of slug flow is realized.

Description of drawings

Figure 1 is a schematic diagram of the installation of an online slug flow monitoring device in an embodiment of the present invention.

Fig. 2 is a schematic diagram of on-line monitoring of slug flow in an embodiment of the present invention.

Fig. 3 is a schematic diagram of an on-line monitoring device for slug flow in an embodiment of the present invention.

Fig. 4 is a schematic diagram of an ERT sensor in an embodiment of the present invention.

Fig. 5 is a partial schematic diagram of the sensor fixing ring in the embodiment of the present invention.

Fig. 6 is a schematic diagram of a slug flow elimination system in an embodiment of the present invention.

Fig. 7 is a schematic diagram of a slug flow formation cycle in an embodiment of the present invention.

Fig. 8 is a schematic diagram showing the variation of the pressure at the bottom of the standpipe with the opening of the valve in the embodiment of the present invention.

Detailed ways

Specific embodiments of the present invention will be described below in conjunction with the accompanying drawings, so as to better understand the present invention.

Example

In this embodiment, the slug flow on-line monitoring device is installed at the bottom, middle and upper part of the riser, as shown in FIG. 1 . The three-phase oil, gas and water produced from reservoir 1, reservoir 2 and reservoir 3 enter the offshore platform for processing through the submarine gathering pipeline and riser, and the slug flow online monitoring device can move freely on the riser through the transmission device , real-time monitoring of flow pattern changes in the standpipe.

The principle of on-line monitoring of slug flow is shown in Figure 2. Six ERT probes are evenly distributed on the outer wall of the pipeline at the same central angle. For each measurement, one probe is activated and the remaining 5 probes are inactive. In the first stage, a voltage of 5V is applied to the first active probe to run through the entire pipe wall system, and the voltage drop U _m from the active state probe to the inactive state probe is measured, and the current current value i of the inactive state probe is measured _m , therefore, according to Ohm's law, the resistance r _m and the resistivity G _m from the active state probe to the inactive state probe can be measured:

In the second stage, another probe (such as the second activation probe shown in the figure) is in the activated state, and the rest of the probes are in the inactive state. After six activations, each probe has an activated state once, depicting a A complete pipeline cross-sectional resistivity grid, the subscript m refers to the signals received in one measurement process (5 signals under the condition of 6 probes), a total of 30 signal processing (6×5=30), with the probe As the number increases, the accuracy of the image increases, and at the same time, the computational burden increases, and the delay of the real-time image increases.

The on-line monitoring device for slug flow in the standpipe is shown in Figure 3. Including the first ERT sensor 11, the second ERT sensor 12, the third ERT sensor 13, the fourth ERT sensor 14, the fifth ERT sensor 15, the sixth ERT sensor 16, the first fixing bolt 211, the second fixing bolt 212, the Three fixing bolts 221, fourth fixing bolts 222, fifth fixing bolts 231, sixth fixing bolts 232, seventh fixing bolts 241, eighth fixing bolts 242, ninth fixing bolts 251, tenth fixing bolts 252, eleventh fixing bolts The fixing bolt 261 , the twelfth fixing bolt 262 , the sensor fixing ring 3 , the outer wall 4 of the standpipe, and the inner wall 5 of the standpipe.

The sensor fixing ring 3 fixes the first ERT sensor 11, the second ERT sensor 12, the third ERT sensor 13, the fourth ERT sensor 14, the fifth ERT sensor 15, and the sixth ERT sensor 16 in the same central angle. Standpipe outer wall 4, the first fixing bolt 211 and the second fixing bolt 212 are inserted into the sensor fixing ring 3 to fix the first ERT sensor 11, and the third fixing bolt 221 and the fourth fixing bolt 222 are inserted into the sensor fixing ring 3. The sensor fixing ring 3 fixes the second ERT sensor 12, the fifth fixing bolt 231 and the sixth fixing bolt 232 are inserted into the sensor fixing ring 3, fixing the third ERT sensor 13, and the seventh fixing The bolt 241 and the eighth fixing bolt 242 are inserted into the sensor fixing ring 3 to fix the fourth ERT sensor 14, and the ninth fixing bolt 251 and the tenth fixing bolt 252 are inserted into the sensor fixing ring 3 to fix the fourth ERT sensor 14. The fifth ERT sensor 15, the eleventh fixing bolt 261 and the twelfth fixing bolt 262 are inserted into the sensor fixing ring 3 to fix the sixth ERT sensor 16, and the outer wall 4 of the riser is concentric with the inner wall 5 of the riser .

The first ERT sensor 11 , the second ERT sensor 12 , the third ERT sensor 13 , the fourth ERT sensor 14 , the fifth ERT sensor 15 and the sixth ERT sensor 16 are of the same type and specification.

The first fixing bolt 211, the second fixing bolt 212, the third fixing bolt 221, the fourth fixing bolt 222, the fifth fixing bolt 231, the sixth fixing bolt 232, the seventh fixing bolt 241, the eighth fixing bolt 242, The ninth fixing bolt 251 , the tenth fixing bolt 252 , the eleventh fixing bolt 261 , and the twelfth fixing bolt 262 are of the same type and specification, and are fixed in the same way in the sensor fixing ring 3 .

The ERT sensor is shown in Figure 4. The spring 102 connects the base 101 with the sensor patch 103, and the spring 102 exerts pressure on the sensor patch 103 to ensure that the ERT sensor is closely attached to the outer wall of the riser. In order to achieve a better imaging effect, the ERT probe needs to be selected. Type, the selection table is as follows, in order to ensure the accuracy of imaging and reduce the delay of real-time imaging, the ERT sensor with a conductor ring is selected.

A partial view of the sensor fixing ring is shown in Figure 5. Between the fifth fixing bolt 231 and the sixth fixing bolt 232 is a compression structure 234 and an elastic clamping structure 235. The compression structure 234 and the elastic clamping structure 235 form an installation channel, and the third ERT sensor 13 fixed.

The mounting channel formed by the pressing structure 234 and the elastic clamping structure 235 has the same diameter as the third ERT sensor 13 . The pressing structure 234 is made of stainless steel A2-70, and the elastic clamping structure 235 is made of polytetrafluoroethylene.

The slug elimination system is shown in Figure 6. The slug flow elimination method adopted by the system is as follows, a: based on the fluid image in the standpipe provided by the first slug flow online monitoring device 19, the second slug flow online monitoring device 20, and the third slug flow online monitoring device 21, through The first pressure sensor 18 at the bottom of the standpipe 30 determines the pressure threshold P ₁ when the slug flow is just formed; b: when the first pressure sensor 18 measures the pressure value P ₂ at the bottom of the standpipe 30 is greater than the pressure threshold P ₁ , increase the first valve 28 degrees of opening, so that the gas phase flow rate in the standpipe 30 increases, the slug flow pattern changes, and the purpose of eliminating the slug flow is achieved. When the first pressure sensor 18 measures the pressure value _P2 at the bottom of the standpipe 30 is less than the pressure threshold _P1 , No slug flow occurs, reduce the opening of the first valve 28; c: According to the above steps a and b, the opening of the first valve 28 is measured by the pressure threshold P ₁ and the pressure value at the bottom of the riser 30 by the first pressure sensor 18 P ₂ decision; d: the production separator 29 is provided with a first liquid level gauge 31 and a second liquid level gauge 32, when the liquid level is higher than the position of the first liquid level gauge 31, increase the opening degree of the second valve 37, When the liquid level is lower than the position of the second liquid level gauge 32, close the second valve 37 until the liquid level increases to the position of the second liquid level gauge 32 again, and open the second valve 37; e: there is no slug in the standpipe 30 When the flow is formed, the gas phase pressure in the production separator 29 is measured by the second pressure sensor 24, the data is fed back to the second controller 23, the opening of the first valve 28 is controlled, and the pressure in the production separator 29 is adjusted; f: immediately When slug flow occurs in the pipe 30, the second controller 23 fails, and the first controller 25 receives the pressure information at the bottom of the riser 30 to control the opening of the first valve 28. The first controller 25 is a PID controller, 17 is a submarine gathering and transportation production pipeline, which is used to transport three-phase oil, gas and water, and the end is connected with the standpipe 30. 22, 26, 33, 34, and 36 are all control lines.

The cycle of slug flow formation is shown in Fig. 7. t ₀ to t ₁ is the stage of liquid blockage and liquid slug growth. Under the small air flow velocity in the standpipe, the liquid in the pipe flows downward and accumulates at the bottom of the standpipe, blocking the gas-liquid mixture flowing into the pipe, making the pipeline pressure upstream of the liquid slug Increase, the liquid plug becomes longer, only a small amount of gas-liquid two-phase outflow at the outlet of the standpipe. From t ₁ to t ₂ is the stage of gas pressure increase, the pressure in the pipeline increases, and at the same time, the liquid continues to accumulate, the liquid plug grows, and the liquid level in the standpipe gradually rises. When the pipeline pressure is higher than the static head of the standpipe, the liquid begins to flow from Outflow from the top of the riser. From t ₂ to t ₃ is the liquid plug outflow stage. When the pipeline pressure is sufficient to lift the liquid column in the standpipe, the liquid starts to discharge from the top of the standpipe. At first, the liquid discharge speed is low. When the gas enters the standpipe, the liquid accelerates. Liquid flow reaches peak flow. From _t3 to _t4 is the gas discharge stage in the standpipe. The gas accumulated upstream of the liquid plug is discharged out of the standpipe very quickly. After entering the receiving device of the platform, the gas flow rate in the standpipe decreases, the pipeline pressure drops, and a new cycle begins.

The pressure at the bottom of the standpipe varies with the opening of the valve as shown in Figure 8. Adjust the opening degree of the first valve 28, and provide an image of the internal flow pattern of the standpipe through the first slug flow online monitoring device 19, the second slug flow online monitoring device 20, and the third slug flow online monitoring device 21, when the standpipe When the slug flow just appears at the bottom of the standpipe 30, the pressure threshold _P1 at the bottom of the riser 30 is measured by the first pressure sensor 18. When the pressure value _P2 measured by the first pressure sensor 18 at the bottom of the standpipe 30 is greater than the pressure threshold _P1 , Increase the opening degree of the first valve 28, increase the gas phase flow rate, eliminate the slug flow in the standpipe 30, and stabilize the pressure in the standpipe 30.

The above description is a preferred embodiment of the present invention, and it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered Be the protection scope of the present invention.

Claims (8)

1. A slug flow online monitoring device in a riser is characterized in that: comprising a first ERT sensor (11), a second ERT sensor (12), a third ERT sensor (13), a fourth ERT sensor (14), The fifth ERT sensor (15), the sixth ERT sensor (16), the first fixing bolt (211), the second fixing bolt (212), the third fixing bolt (221), the fourth fixing bolt (222), the fifth Fixing bolts (231), sixth fixing bolts (232), seventh fixing bolts (241), eighth fixing bolts (242), ninth fixing bolts (251), tenth fixing bolts (252), eleventh fixing bolts Bolt (261), twelfth fixing bolt (262), sensor fixing ring (3), outer wall of standpipe (4), inner wall of standpipe (5); The sensor fixing ring (3) connects the first ERT sensor (11), the second ERT sensor (12), the third ERT sensor (13), the fourth ERT sensor (14), the fifth ERT sensor (15), the Six ERT sensors (16) are uniformly fixed on the outer wall of the riser (4) at the same central angle, and the first fixing bolt (211) and the second fixing bolt (212) are inserted into the sensor fixing ring (3), and the fixed The first ERT sensor (11), the third fixing bolt (221) and the fourth fixing bolt (222) are inserted into the sensor fixing ring (3) to fix the second ERT sensor (12), the second Five fixing bolts (231), the sixth fixing bolt (232) are inserted into the sensor fixing ring (3), and the third ERT sensor (13) is fixed, the seventh fixing bolt (241), the eighth fixing bolt ( 242) Insert the sensor fixing ring (3), fix the fourth ERT sensor (14), insert the ninth fixing bolt (251) and the tenth fixing bolt (252) into the sensor fixing ring (3), Fix the fifth ERT sensor (15), insert the eleventh fixing bolt (261) and the twelfth fixing bolt (262) into the sensor fixing ring (3), and fix the sixth ERT sensor (16) , the outer wall (4) of the riser is concentric with the inner wall (5) of the riser. 2. The on-line monitoring device for slug flow in the standpipe according to claim 1, characterized in that: the first ERT sensor (11), the second ERT sensor (12), the third ERT sensor (13), the fourth ERT sensor (14), the 5th ERT sensor (15), the 6th ERT sensor (16) are identical model specifications. 3. The on-line monitoring device for slug flow in the standpipe according to claim 1, characterized in that: the first fixing bolt (211), the second fixing bolt (212), the third fixing bolt (221), the fourth Fixing bolts (222), fifth fixing bolts (231), sixth fixing bolts (232), seventh fixing bolts (241), eighth fixing bolts (242), ninth fixing bolts (251), tenth fixing bolts (252), the eleventh fixing bolt (261), and the twelfth fixing bolt (262) are the same type and specification, and the fixing methods in the sensor fixing ring (3) are the same. 4. The on-line monitoring device for slug flow in the standpipe according to claim 1, characterized in that: the inner spring (102) of the first ERT sensor (11) connects the base (101) with the sensor patch (103), The spring (102) exerts pressure on the sensor patch (103). 5. The on-line monitoring device for slug flow in the standpipe according to claim 1, characterized in that: there is a compression structure (234) between the fifth fixing bolt (231) and the sixth fixing bolt (232), with The elastic clamping structure (235), the pressing structure (234), and the elastic clamping structure (235) form an installation channel to fix the third ERT sensor (13). 6. The on-line monitoring device for slug flow in the riser according to claim 5, characterized in that: the installation channel formed by the pressing structure (234), the elastic clamping structure (235) and the third ERT The sensors (13) have the same diameter. 7. The on-line monitoring device for slug flow in the standpipe according to claim 5, characterized in that: the clamping structure (234) is made of stainless steel A2-70 material, and the elastic clamping structure (235) is made of polystyrene Made of vinyl fluoride. 8. The on-line monitoring device for slug flow in the standpipe according to claim 1, characterized in that: the slug flow elimination method adopted by the above-mentioned device: a: based on the images of the fluid in the standpipe provided by the first slug flow on-line monitoring device (19), the second slug flow on-line monitoring device (20), and the third slug flow on-line monitoring device (21), through the standpipe (30 ) The first pressure sensor (18) at the bottom determines the pressure threshold P ₁ when the slug flow is just formed; b: When the first pressure sensor (18) measures the pressure value _P2 at the bottom of the standpipe (30) greater than the pressure threshold _P1 , increase the opening of the first valve (28), and the first pressure sensor (18) measures the standpipe (30) ) When the bottom pressure value P ₂ is less than the pressure threshold P ₁ , reduce the opening of the first valve (28); c: According to the above steps a and b, the opening of the first valve (28) is determined by the pressure threshold _P1 and the pressure value _P2 at the bottom of the riser (30) measured by the first pressure sensor (18); d: The production separator (29) is provided with a first liquid level gauge (31) and a second liquid level gauge (32). When the liquid level is higher than the position of the first liquid level gauge (31), increase the second valve (37) Opening degree, when the liquid level is lower than the position of the second liquid level gauge (32), close the second valve (37) until the liquid level increases to the position of the second liquid level gauge (32), open the second valve valve (37); e: When no slug flow is formed in the standpipe (30), the gas phase pressure in the production separator (29) is measured by the second pressure sensor (24), and the data is fed back to the second controller (23). (28) the opening is controlled to regulate the pressure in the production separator (29); f: When slug flow occurs in the standpipe (30), the second controller (23) fails, and the pressure information at the bottom of the standpipe (30) is received by the first controller (25), and the opening degree of the first valve (28) is controlled. To control, the first controller (25) is a PID controller.