A shale gas collection control system and shale gas separation method

Abstract

The application discloses a shale gas collection control system and a shale gas separation method. The shale gas collection control system comprises a cyclone desander, a three-phase separator, a pilot float liquid discharge valve and a controller. The inlet of the cyclone desander is connected with the system material inlet. The exhaust port of the cyclone desander is connected with the air inlet of the three-phase separator, and the liquid outlet of the cyclone desander is connected with the liquid inlet of the three-phase separator. The exhaust port of the three-phase separator is connected with the system gas phase outlet, and the liquid outlet of the three-phase separator is connected with the liquid inlet of the pilot float liquid discharge valve. The three-phase separator has a sand discharge port and a sand suction port. The liquid outlet of the pilot float liquid discharge valve is connected with the system pollution discharge port. The controller is used for controlling the sand discharge port and the sand suction port to alternately perform sand discharge and sand suction. The sand discharge and the sand suction are alternately performed, the phenomenon of sand blockage caused by sand deposition in the sand discharge pipeline is avoided, the safety is good, the environmental pollution caused by gas overflow is reduced, the automation is high, the labor cost consumption can be reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a shale gas collection and control system and a shale gas separation method. Background Technology

[0002] Hydraulic fracturing is frequently used in domestic shale gas extraction. After fracturing, the injected fracturing fluid carrying proppant is released using the bottom hole pressure as the driving force. Shale gas extraction requires a preliminary testing phase before entering a stable production phase. During the preliminary testing phase, the fluid released from the wellhead mainly consists of fracturing flowback fluid with low gas content. As the release process continues, the gas content gradually increases. The wellhead pressure fluctuates significantly during the release process, often resulting in intermittent flow interruptions, meaning the fracturing flowback fluid is released intermittently.

[0003] Fracturing reverse flow fluid is a mixture of gas, liquid, and sand. During production, it is necessary to separate the gas, liquid, and sand from each other. Existing separators used in shale gas extraction have a low degree of automation. Instrument viewing and valve operation require multiple people to be stationed on-site and to operate the equipment frequently, resulting in low production efficiency and high labor costs. On the other hand, although manual operation is effective for shale gas dehydration in the stable production stage, it is clearly insufficient for the early-stage extraction and testing phase, where sand content is high, the gas-liquid ratio varies greatly, and blockages frequently occur. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a shale gas collection and control system and a shale gas separation method that overcomes or at least partially solves the above problems.

[0005] In a first aspect, embodiments of the present invention provide a shale gas collection and control system, comprising: a cyclone desander, a three-phase separator, a pilot-operated float drain valve, and a controller;

[0006] The inlet of the cyclone desander is connected to the system material inlet for inputting fracturing reverse flow fluid; the exhaust port of the cyclone desander is connected to the air inlet of the three-phase separator, and the liquid outlet of the cyclone desander is connected to the liquid inlet of the three-phase separator.

[0007] The exhaust port of the three-phase separator is connected to the gas phase outlet of the system, and the liquid outlet of the three-phase separator is connected to the liquid inlet of the pilot float discharge valve; the three-phase separator has a sand discharge port and a sand suction port;

[0008] The outlet of the pilot float drain valve is connected to the system's drain outlet;

[0009] The controller is used to control the sand discharge port and the sand suction port to alternately discharge and suction sand.

[0010] The three-phase separator contains a vertically arranged sand baffle plate, which divides the inner cavity into a sand settling chamber and a liquid storage chamber.

[0011] The sand discharge port and the sand suction port are respectively located at the bottom of the sand settling chamber.

[0012] A phase interface instrument is also installed above the sedimentation chamber of the three-phase separator;

[0013] The sand discharge port is connected to the sand discharge pipeline, and a first switch valve is installed on the sand discharge pipeline;

[0014] The sand suction port is connected to the sand suction pipe, and a second switch valve is installed on the sand suction pipe;

[0015] The sand discharge pipeline and the sand suction pipeline are connected to the pipeline between the liquid outlet of the pilot float discharge valve and the sewage outlet of the system.

[0016] The controller is also used to start timing if the reading of the phase interface instrument is greater than a preset threshold; calculate the integer part of the ratio of the current timing time t to the preset time T; and control the opening and closing of the first switching valve and the second switching valve alternately according to the parity of the integer part, so that sand discharge and sand suction are carried out alternately.

[0017] The drain port of the three-phase separator is connected to the first branch pipe and the second branch pipe. The first branch pipe is connected to the inlet of the pilot float drain valve, and the outlet of the second branch pipe is connected to the outlet of the pilot float drain valve. After converging into a common pipe, they are connected to the system drain port.

[0018] A second regulating valve is installed in the second branch pipeline;

[0019] The liquid storage chamber of the three-phase separator is also equipped with a second liquid level transmitter;

[0020] The controller is also used to control the second regulating valve to open to discharge the liquid discharged from the three-phase separator drain port when the pilot-operated float drain valve malfunctions or is out of service.

[0021] A first safety shut-off valve is installed on the connecting pipeline between the exhaust port of the three-phase separator and the gas phase outlet of the system.

[0022] A second safety shut-off valve is also provided on the common pipeline formed by the connection between the outlet of the second branch pipeline and the outlet of the pilot float drain valve;

[0023] The controller is also used to control the first safety shut-off valve and the second safety shut-off valve to cut off the pipeline and issue an alarm message when the second level transmitter detects that the liquid level in the storage chamber has reached the upper or lower limit of the liquid level.

[0024] A first regulating valve is also installed on the pipeline connecting the material inlet of the system and the inlet of the cyclone separator; an orifice plate flow meter is also installed on the pipeline connecting the exhaust port of the three-phase separator and the gas phase outlet of the system; a liquid flow meter is also installed on the pipeline between the liquid outlet of the pilot float drain valve and the sewage outlet of the system.

[0025] The controller is also used to calculate the ratio of the flow rate of the currently discharged gas collected by the orifice plate flow meter to the flow rate of the currently discharged liquid collected by the liquid flow meter;

[0026] If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0027] If the ratio is less than a preset ratio threshold and the current flow rate of the discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0028] A mist eliminator is also installed at the exhaust port of the three-phase separator.

[0029] The three-phase separator is also equipped with a three-phase separator pressure equalization interface, and the pilot-operated float drain valve is also equipped with a pilot-operated float drain valve pressure equalization interface.

[0030] The pressure equalization port of the three-phase separator is connected to the pressure equalization port of the pilot-operated float drain valve.

[0031] A first manual ball valve is also installed on the pipeline between the material inlet of the system and the inlet of the cyclone separator;

[0032] A second manual ball valve is installed on the connecting pipe between the exhaust port of the cyclone separator and the air inlet of the three-phase separator.

[0033] A seventh manual ball valve is installed on the connecting pipeline between the drain port of the cyclone separator and the inlet of the sand settling chamber of the three-phase separator.

[0034] A fifth manual ball valve is also installed on the pipeline connecting the exhaust port of the three-phase separator to the gas phase outlet of the system.

[0035] The sand discharge pipeline is also equipped with an eighth manual ball valve;

[0036] The sand suction pipe is also equipped with a ninth manual ball valve.

[0037] Secondly, embodiments of the present invention provide a method for shale gas separation using the aforementioned shale gas collection and control system.

[0038] When the three-phase separator separates gas, liquid and sand, the controller controls the sand discharge port and sand suction port of the three-phase separator to alternately discharge and suction sand.

[0039] The sand discharge port and sand suction port are controlled to alternately discharge and suction sand using the following method:

[0040] If the controller determines that the reading of the phase interface meter is greater than a preset threshold, then the timing is started;

[0041] Calculate the integer part of the ratio of the current time t to the preset time T; based on the parity of the integer part, alternately control the opening and closing of the first and second switching valves so that sand discharge and sand suction are performed alternately.

[0042] The shale gas separation method further includes:

[0043] The controller calculates the ratio of the current discharge gas flow rate collected by the orifice plate flow meter to the current discharge liquid flow rate collected by the liquid flow meter;

[0044] If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0045] If the ratio is less than a preset ratio threshold and the current flow rate of the discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0046] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0047] The shale gas collection control system and shale gas separation method of this invention adopt an alternating sand suction and sand discharge control mode, which not only realizes the automatic sand discharge function, but also has the function of clearing blocked pipes, thus avoiding pipe blockage during the automatic sand discharge process.

[0048] The shale gas collection and control system of this invention can automatically adjust according to changes in the gas-liquid ratio of the material, and maximize the processing efficiency and improve the equipment utilization efficiency while ensuring that the exhaust water content and the exhaust liquid gas content meet the process requirements.

[0049] The shale gas collection and control system of this invention is equipped with a second safety shut-off valve in the drainage pipeline to prevent shale gas from flowing into the atmosphere and causing environmental pollution when the liquid level drops rapidly due to changes in material pressure and component ratio; thus ensuring production safety, reducing losses and avoiding environmental pollution.

[0050] The shale gas collection and control system of this invention is equipped with a first safety shut-off valve in the exhaust pipeline. This prevents the backflow liquid from directly entering the pipeline network through the exhaust pipeline when the liquid level rises rapidly due to changes in material pressure and component ratio, which would increase the water content of the output gas, cause dehydration failure, and fail to meet process requirements.

[0051] The shale gas collection and control system of this invention adopts two independent drainage control methods, namely a second regulating valve and a pilot-operated float drainage valve, which serve as backups for each other. When the pilot-operated float drainage valve fails and needs to be repaired, the regulating valve is intelligently switched to control the drainage, without stopping production and without affecting the mining progress.

[0052] The shale gas collection and control system of this invention has a high degree of automation, enabling unattended operation and effectively reducing personnel costs.

[0053] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0055] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0056] Figure 1 This is a schematic diagram of the shale gas collection and control system in an embodiment of the present invention;

[0057] Figure 2 This is a schematic diagram of a three-phase separator in an embodiment of the present invention;

[0058] Figure 3 This is a schematic diagram of a cyclone sand separator in an embodiment of the present invention;

[0059] Figure 4 This is a schematic diagram of a pilot-operated float drain valve in an embodiment of the present invention;

[0060] Figure 5 This is a control flowchart of the working process in an embodiment of the present invention.

[0061] Explanation of reference numerals in the attached figures:

[0062] 1-System material inlet, 2-Manual ball valve 1, 3-First regulating valve, 4-Cyclone sand separator, 5-Three-phase separator, 6-Second manual ball valve, 7-Phase interface meter, 8-Pressure gauge, 9-Third manual ball valve, 10-Safety valve, 11-Fourth manual ball valve, 12-First vent valve, 13-Fifth manual ball valve, 14-System gas phase outlet, 15-System vent port, 16-First safety shut-off valve (for gas), 17-Orifice plate flow meter, 18-Second vent valve 19-Pilot-operated float drain valve, 20-Sixth manual ball valve, 21-First flat gate valve, 22-Second flat gate valve, 23-Third flat gate valve, 24-Second regulating valve, 25-Fourth flat gate valve, 26-Second safety shut-off valve (responsible for liquid), 27-Liquid flow meter, 28-Seventh manual ball valve, 29-Eighth manual ball valve, 30-First switching valve, 31-Ninth manual ball valve, 32-Drain valve, 33-System drain port, 34-Second switching valve;

[0063] 35-First level transmitter, 36-Air inlet of three-phase separator, 37-Grit chamber, 38-Sand baffle, 39-Second level transmitter, 40-Safety valve venting port, 41-Storage chamber, 42-Venting valve venting port, 43-Three-phase separator exhaust port, 44-Wire mesh mist eliminator, 45-Three-phase separator pressure equalization port, 46-Three-phase separator drain port, 47-Three-phase separator grit chamber inlet, 48-Sand discharge port, 49-Sand suction port, 50-Cyclone sand separator exhaust port, 51-Cyclone sand separator inlet, 52-Cyclone sand separator drain port, 53-Pilot-operated float drain valve pressure equalization port, 54-Pilot-operated float drain valve inlet, 55-Pilot-operated float drain valve outlet, 56-Pilot-operated float drain valve venting port. Detailed Implementation

[0064] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0065] This invention provides a shale gas collection and control system, referring to... Figures 1-4 As shown, it includes: a cyclone separator 4, a three-phase separator 5, a pilot-operated float drain valve 19, and a controller ( Figures 1-4 (Not shown in the text); Among them:

[0066] The inlet of the cyclone desander 4 is connected to the system material inlet 1 for inputting fracturing reverse flow fluid; the exhaust port 50 of the cyclone desander 4 is connected to the air inlet 36 of the three-phase separator 5, and the liquid outlet 52 of the cyclone desander 4 is connected to the liquid inlet 47 of the three-phase separator 5.

[0067] The exhaust port 43 of the three-phase separator 5 is connected to the gas phase outlet of the system, and the liquid discharge port of the three-phase separator 5 is connected to the liquid inlet of the pilot float discharge valve; the three-phase separator 5 has a sand discharge port 48 and a sand suction port 49.

[0068] The outlet 55 of the pilot float drain valve is connected to the system's drain outlet;

[0069] Controller ( Figure 1 and Figure 2 (Not shown in the diagram) is used to control the sand discharge port 48 and the sand suction port 49 to alternately discharge and suction sand.

[0070] In this embodiment of the invention, the material refers to the fracturing reverse discharge fluid; the controller can be a variety of controllers, such as a PLC programmable logic controller, and this embodiment of the invention does not limit the type of controller.

[0071] In this embodiment of the invention, fracturing reverse flow fluid is first fed into a hydrocyclone desander 4. Under the action of centrifugal force and gravity, the liquid and sand particles are deposited to the bottom along the conical structure of the hydrocyclone desander 4, achieving the separation of larger sand particles from liquid and gas. The liquid passes through the discharge port 52 of the hydrocyclone desander 4 and connects to the inlet 47 of the three-phase separator 5, further entering the three-phase separator 5. Meanwhile, the smaller liquid and sand particles continue to mix with the gas and enter the three-phase separator 5 through the gas phase outlet of the hydrocyclone desander 4. In the three-phase separator 5, due to the further reduction of gas pressure, the gas in the liquid is released and the sand particles are deposited, further achieving the separation of gas, liquid and sand. During this process, due to the high pressure of the input fracturing flowback fluid and the potential for blockages caused by high sand content and large changes in the gas-liquid ratio during the early production testing phase, the cyclone desander 4 acts as a good buffer. The intermittently discharged fracturing flowback fluid is collected in the cyclone desander 4 into a more stable and continuous state before being output to the three-phase separator 5 at a lower pressure for further separation of liquid, sand, and gas. Furthermore, an alternating sand discharge and sand suction working mode is adopted in this process. This alternation of sand discharge and sand suction avoids the long-term deposition of sand sludge in the sand discharge pipe under gravity, preventing blockages. Additionally, the alternation of sand suction and discharge also avoids the problem of incomplete sand discharge that can occur with simultaneous sand suction and discharge. In addition, during the drainage process of the three-phase separator 5, the flow rate is controlled by a pilot-operated float drainage valve 19. The liquid level in the drainage valve is consistent with the liquid level in the three-phase separator 5. The opening of the drainage valve is adjusted by the up and down movement of its own float to keep the liquid level in the storage chamber 41 of the three-phase separator 5 stable, which improves safety and reduces environmental pollution caused by gas overflow.

[0072] Furthermore, the controller can control the valves and actuators in the shale gas collection and control system, thereby solving the problems of low automation and cumbersome operation of existing shale gas separators, and effectively addressing the issues of low production efficiency and high labor costs.

[0073] Reference Figure 2 As shown, in the settling chamber 37, a large amount of sand and gravel settles to the bottom and is discharged from the sand discharge port 48 of the three-phase separator. The liquid rises and enters the liquid storage chamber 41 after passing over the baffle. During the settling process, the gas in the liquid floats up to achieve gas-liquid separation and is finally discharged from the liquid discharge port 46. The gas enters the upstream space of the three-phase separator 5. As the pressure decreases, the gas in the liquid gradually precipitates out. Under the action of gravity, the liquid droplets in the gas sink to achieve gas-liquid separation. Finally, the gas passes through the wire mesh mist eliminator 44 (set at the exhaust port of the three-phase separator) to filter out droplets with a particle size greater than 10μm and is discharged from the three-phase separator and enters the pipeline network.

[0074] Reference Figure 2As shown, the three-phase separator 5 contains a vertically arranged sand baffle plate, which divides the inner cavity into a sand settling chamber 37 and a liquid storage chamber 41.

[0075] The sand discharge port 48 and the sand suction port 49 are respectively located at the bottom of the sand settling chamber 37.

[0076] Reference Figure 1 and Figure 2 As shown, a phase interface instrument 7 is also provided above the sedimentation chamber 37 of the three-phase separator 5;

[0077] The sand discharge port 48 is connected to the sand discharge pipeline, and the first switch valve 30 is installed on the sand discharge pipeline;

[0078] The sand suction port 49 is connected to the sand suction pipe, and a second switch valve 34 is installed on the sand suction pipe;

[0079] The sand discharge pipeline and the sand suction pipeline are connected to the pipeline between the outlet 55 of the pilot float discharge valve and the system's drain outlet;

[0080] The phase interface meter 7 is used to measure the height of sand content in the container. When the measured value is higher than the preset value, the sand discharge and suction functions are automatically activated. When the measured value is lower than the preset value, the function is stopped. Based on this, the controller is also used to start timing if the reading of the phase interface meter 7 (indicating the amount of sand) is greater than the preset threshold; calculate the integer part of the ratio of the current timing time t to the preset time T; and control the opening and closing of the first switching valve 30 and the second switching valve 34 alternately according to the parity of the integer part, so that sand discharge and sand suction are carried out alternately.

[0081] The pilot float drain valve's valve core and seat are constantly in a state of relative friction, making it prone to damage. To avoid production delays during drain valve maintenance and parts replacement, a backup regulating valve automatic drain line is designed into the automatic drain pipeline. This allows for timely switching to the backup regulating valve automatic drain line to continue drain control during maintenance of the original automatic drain line, without requiring machine shutdown and offering convenient operation. Specifically, refer to... Figure 1 As shown, the drain port 46 of the three-phase separator is connected to the first branch pipe and the second branch pipe. The first branch pipe is connected to the inlet 54 of the pilot float drain valve, and the outlet of the second branch pipe is connected to the outlet 55 of the pilot float drain valve. After the two branches are connected to the common pipe, they are connected to the system drain port 33.

[0082] A second regulating valve 24 is installed in the second branch pipeline; a second level transmitter 39 is also installed in the liquid storage chamber 41 of the three-phase separator 5; the controller is also used to control the second regulating valve 24 to open to discharge the liquid discharged from the three-phase separator drain port when the pilot float drain valve 19 malfunctions or is out of service for maintenance.

[0083] The second branch pipeline serves as a backup for the first branch pipeline, and can continue to automatically drain liquid when the pilot float drain valve 19 on the first branch fails.

[0084] Furthermore, referring to Figure 1 As shown, a first safety shut-off valve 16 is installed on the connecting pipeline between the exhaust port of the three-phase separator and the gas phase outlet 14 of the system;

[0085] A second safety shut-off valve 26 is also provided on the common pipeline formed by the connection between the outlet of the second branch pipeline and the outlet 55 of the pilot float drain valve.

[0086] The controller is also used to control the first safety shut-off valve 16 and the second safety shut-off valve 26 to cut off the pipeline and issue an alarm message when the second level transmitter 39 detects that the liquid level in the liquid storage chamber 41 has reached the upper or lower limit of the liquid level.

[0087] During the early testing phase of shale gas extraction, unstable bottom-hole pressure frequently leads to blockages in the fracturing backflow fluid entering the separator, causing significant fluctuations in the fluid level. Although the pilot-operated float-type backflow valve 19 ensures stable fluid levels during the backflow process, delays in control prevent timely adjustments to address sudden, large fluctuations. This can result in sharp drops or rises in the fluid level. A sharp drop could cause shale gas to leak into the atmosphere through the backflow pipeline, causing environmental pollution. A sharp rise could cause backflow fluid to flow directly into the gas pipeline network through the exhaust pipeline, resulting in high water content in the exhaust gas and degassing failure. Therefore, safety shut-off valves should be installed on the backflow and exhaust pipelines. These valves should be activated promptly when the fluid level drops to the lower limit or rises to the upper limit to close the backflow and exhaust pipelines, improving safety, reducing losses, and preventing environmental pollution.

[0088] Reference Figure 1 As shown, a first regulating valve 3 is also installed on the pipeline connecting the system material inlet 1 and the inlet of the cyclone separator 4; an orifice plate flow meter 17 is also installed on the pipeline connecting the three-phase separator exhaust port 43 and the system gas phase outlet 14; and a liquid flow meter 27 is also installed on the pipeline between the liquid outlet 55 of the pilot float drain valve and the system drain port 33.

[0089] The controller is also used to calculate the ratio of the flow rate of the currently discharged gas collected by the orifice plate flow meter 17 to the flow rate of the currently discharged liquid collected by the liquid flow meter.

[0090] If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve 3 is controlled to decrease its opening; otherwise, the first regulating valve 3 is controlled to increase its opening.

[0091] If the ratio is less than a preset ratio threshold and the current flow rate of the discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve 3 is controlled to reduce its opening; otherwise, the first regulating valve 3 is controlled to increase its opening.

[0092] In this embodiment of the invention, the gas-to-liquid ratio in the material (fracturing reverse runoff fluid) changes continuously with the shale gas extraction process. Generally, the changes are more pronounced during the initial testing phase and relatively stable during conventional extraction. With the container structure dimensions fixed, the system's processing capacity remains almost constant. The changing gas-to-liquid ratio necessitates adjustments to the feed rate to meet the separator's processing capacity requirements. Automatic optimization calculations are performed using exhaust and liquid flow rates to control the material delivery flow rate, maximizing processing capacity while ensuring effective exhaust and liquid separation.

[0093] Or refer to Figure 1 and Figure 2 The structural diagram shown illustrates that, based on the aforementioned structure, the shale separation system provided in this embodiment of the invention can also be equipped with various valves, pressure gauges, etc., on the pipeline to enhance the overall system's automation control capabilities. The following section will use... Figures 1-4 Taking this as an example, the components of the shale gas collection and control system of this embodiment of the invention will be described in detail.

[0094] Specifically, the shale separation system mainly includes: system material inlet 1, first manual ball valve 2, first regulating valve 3, cyclone sand separator 4, three-phase separator 5, second manual ball valve 6, phase interface meter 7, pressure gauge 8, third manual ball valve 9, safety valve 10, fourth manual ball valve 11, first manual ball valve 12, fifth manual ball valve 13, system gas phase outlet 14, system vent 15, first safety shut-off valve 16, orifice plate flow meter 17, second manual ball valve 18, pilot-operated float drain valve 19, sixth manual ball valve 20, first flat gate valve 21, second flat gate valve 22, third flat gate valve 23, second regulating valve 24, fourth flat gate valve 25, second safety shut-off valve 26, flow meter 27, seventh manual ball valve 28, eighth manual ball valve 29, first on / off valve 30, ninth manual ball valve 28, and ninth manual ball valve 29. Ball valve 31, drain valve 32, system drain port 33, second switching valve 34, first level transmitter 35, three-phase separator air inlet 36, sand settling chamber 37, sand baffle 38, second level transmitter 39, safety valve venting port 40, liquid storage chamber 41, venting valve venting port 42, three-phase separator exhaust port 43, wire mesh mist eliminator 44, three-phase separator equalization port 45, three-phase separator drain port 46, three-phase separator sand settling chamber inlet 47, sand discharge port 48, sand suction port 49, cyclone sand separator exhaust port 50, cyclone sand separator inlet 51, cyclone sand separator drain port 52, pilot-operated float drain valve equalization port 53, pilot-operated float drain valve inlet 54, pilot-operated float drain valve outlet 55, pilot-operated float drain valve venting port 56, PLC programmable logic controller (PLC) Figure 1 and Figure 2 (Not shown in the text) etc.

[0095] like Figure 2As shown, the three-phase separator 5 is divided into a sand settling chamber 37 and a liquid storage chamber 41 by a sand baffle 38. The sand settling chamber 37 is almost entirely filled with sand and gravel. It has a sand discharge port 48 and a sand suction port 49 at the bottom, and a liquid inlet 47 for the sand settling chamber of the three-phase separator is located next to it. The liquid storage chamber 41 stores the liquid after the sand and gravel have been filtered out by the sand baffle 38. The liquid storage chamber 41 is large enough to facilitate the full floating and separation of the gas carried in the liquid, avoiding environmental pollution caused by the escape of shale gas during the liquid discharge. A three-phase separator drain port 46 is set at the bottom of the liquid storage chamber 41. A first liquid level transmitter 35 and a second liquid level transmitter 39 are respectively set in the sand settling chamber 37 and the liquid storage chamber 41. A three-phase separator air inlet 36, a safety valve venting port 40, a venting valve venting port 42, and a three-phase separator exhaust port 43 are respectively set in the upper part of the three-phase separator 5. A phase interface meter 7 is set directly above the sand settling chamber 37, and a pressure gauge 8 is set in the middle of the upper part of the three-phase separator 5. The cyclone separator 4 has a cyclone separator inlet 51, a cyclone separator exhaust port 50, and a cyclone separator drain port 52 located directly in front, directly above, and directly below, respectively. The pilot-operated float drain valve 19 has a pilot-operated float drain valve equalization port 53, a pilot-operated float drain valve inlet 54, a pilot-operated float drain valve vent port 56, and a pilot-operated float drain valve outlet 55 located on the upper left, lower left, upper right, and directly below, respectively.

[0096] Reference Figure 1 As shown in the figure, the material inlet 1 of the shale gas collection and control system provided in this embodiment of the invention is connected to the inlet 51 of the cyclone separator via a pipeline, and a first manual ball valve 2 is installed on the pipeline. The exhaust port 50 of the cyclone separator is connected to the air inlet 36 of the three-phase separator via a pipeline, and a second manual ball valve 6 is installed on the pipeline.

[0097] The cyclone separator drain port 52 is connected to the three-phase separator settling chamber inlet 47 via a pipeline, and a seventh manual ball valve 28 is installed on the pipeline. The three-phase separator exhaust port 43 is connected to the gas phase outlet 14 of the system via a pipeline, and an orifice flow meter 17, a first safety shut-off valve 16, and a fifth manual ball valve 13 are installed on the pipeline. The three-phase separator drain port 46 is connected to the pilot-operated float drain valve inlet 54 via a pipeline, and a first flat gate valve 21 is installed on the pipeline.

[0098] The outlet 55 of the pilot-operated float discharge valve is connected to the drain outlet 33 of the system by a pipeline. A second flat gate valve 22, a second safety shut-off valve 26, a flow meter 27, and a drain valve 32 are installed on the pipeline. Branch pipe interfaces are installed and connected to the pipeline connecting the three-phase separator drain outlet 46 to the first flat gate valve 21 and the pipeline connecting the second flat gate valve 22 to the second safety shut-off valve 26. A fourth flat gate valve 25, a second regulating valve 24, and a third flat gate valve 23 are installed on these pipelines. Two branch pipe interfaces are installed on the pipeline connecting the flow meter 27 to the drain valve 32, respectively connected to the three-phase separator sand discharge outlet 48 and sand suction outlet 49. A first switch valve 30 and an eighth manual ball valve 29 are installed on the sand discharge pipeline, and a second switch valve 34 and a ninth manual ball valve 31 are installed on the sand suction pipeline.

[0099] The three-phase separator safety valve vent port 40 is connected to the system vent port 15 via a pipeline, and a third manual ball valve 9 and a safety valve 10 are installed on the pipeline. Two branch pipe interfaces are installed on the pipeline connecting the safety valve 10 to the system vent port 15 of this invention, respectively connected to the three-phase separator vent valve vent port 42 and the pilot-operated float drain valve vent port 56. A fourth manual ball valve 11 and a first manual ball valve 12 are installed on the vent valve vent pipeline, and a second manual ball valve 18 is installed on the vent pipeline of the pilot-operated float drain valve 19. The three-phase separator equalization port 45 is connected to the pilot-operated float drain valve equalization port 53 via a pipeline, and a sixth manual ball valve 20 is installed on the pipeline.

[0100] The first regulating valve 3 is interlocked with the flow meter 27 and the orifice plate flow meter 17 respectively. The opening of the first regulating valve 3 is adjusted according to the exhaust and liquid discharge flow to control the flow, so as to maximize the treatment capacity while ensuring the treatment effect.

[0101] The first switching valve 30 and the second switching valve 34 are interlocked with the phase interface instrument 7 to control sand discharge and suction based on the sand content in the three-phase separator, thereby achieving automatic sand discharge.

[0102] The second regulating valve 24 is interlocked with the second liquid level transmitter 39 of the three-phase separator storage chamber. When the pilot-operated float drain valve 19 is in a fault or maintenance state, the liquid level control of the second regulating valve 24 is used to achieve automatic draining without stopping the machine and without affecting the production progress.

[0103] The first safety shut-off valve 16 and the second safety shut-off valve 26 are interlocked with the second liquid level transmitter 39 of the three-phase separator storage chamber. When the liquid level reaches the upper or lower limit, the pipeline is shut off in time and a safety alarm is triggered to improve safety and avoid unnecessary losses.

[0104] The first regulating valve 3, the second regulating valve 24, the first switching valve 30, the second switching valve 34, the first safety shut-off valve 16, and the second safety shut-off valve 26 are powered by instrument air supplied by an air compressor.

[0105] The shale gas collection and control system and its operation method provided in this invention integrate all the cumbersome processes such as manual operation, instrument reading, and on-site emergency handling into the PLC program, realizing fully automated intelligent control and unattended operation of the device.

[0106] Reference Figure 5 As shown, the control process of this shale gas collection and control system is briefly described below:

[0107] Before starting the shale gas collection and control system, it is necessary to perform peripheral equipment operation, manual inspection, and system self-test. After confirming there are no faults, the system can be started. If a fault occurs after the air compressor starts, troubleshooting is required. After the air compressor is running normally, perform a manual inspection to confirm that the first manual ball valve 2, the fifth manual ball valve 13, the first manual ball valve 12, and the second manual ball valve 18 are closed; confirm that the second manual ball valve 6, the third manual ball valve 9, the fourth manual ball valve 11, the sixth manual ball valve 20, the seventh manual ball valve 28, the eighth manual ball valve 29, the ninth manual ball valve 31, the first flat gate valve 21, the second flat gate valve 22, the third flat gate valve 23, and the fourth flat gate valve 25 are fully open; ensure that safety valve 10, the first safety shut-off valve 16, and the second safety shut-off valve 26 are in good condition and that there are no leaks. After the manual inspection confirms everything is normal, perform a system self-test. First, confirm whether the signal lines are normal; if a disconnection occurs, promptly trigger an alarm and troubleshoot the problem. After a cable failure, all valves are opened. The valve opening status is determined based on the returned signal. If a fault is confirmed, an alarm is triggered and the fault is rectified. Once normal operation is confirmed, all valves are closed. If a fault occurs during the closing process, an alarm is triggered and the fault is rectified. Once no fault is confirmed, system startup preparation can begin. Before the shale gas collection and control system starts operating, the fifth manual ball valve 13 is opened to connect the device to the external pipeline and downstream station. The first manual ball valve 2 is then slowly opened until fully open. After system startup, a safety check is performed to determine if the actual liquid level exceeds the set upper limit (LL2) or lower limit (LL1). If the limit is exceeded, the first safety shut-off valve 16 and the second safety shut-off valve 26 are opened, an alarm is triggered, and the equipment stops operating, ensuring both degassing and dehydration effects while avoiding environmental pollution. After the safety check is successful, automatic sand discharge control, automatic material flow regulation, and intelligent switching to backup liquid discharge control are implemented.

[0108] The automatic sand discharge control process includes: first, determining whether the reading of the phase interface instrument 7 exceeds the set value (Q1); if the reading is confirmed to be within the limit range, closing the first switch valve 30 and the second switch valve 34; if the reading exceeds the limit, starting the timer and determining whether the integer part of the ratio of the actual time value (t1) of the phase interface instrument 7 to the set value (T) is even; if the reading is even, opening the first switch valve 30 and closing the second switch valve 34 to perform sand discharge; if the reading is not even, closing the first switch valve 30 and opening the second switch valve 34 to perform sand suction, ensuring that the sand discharge and sand suction processes alternate.

[0109] The automatic material flow rate regulation process includes: First, determining whether the ratio of the actual exhaust flow rate to the drainage flow rate is not less than the set ratio of the exhaust flow rate to the set drainage flow rate (q1 / q2). Then, determining whether there is more exhaust or drainage. If it is confirmed that it is not less than the set ratio, it means that there is more exhaust. The process continues to determine whether the actual exhaust flow rate is not less than the set exhaust flow rate. If it is confirmed that it is not less than the set exhaust flow rate, the opening of the first regulating valve 3 is reduced. If it is confirmed that it is less than the set ratio, the opening of the first regulating valve 3 is increased to ensure that the exhaust processing capacity is maximized. If it is confirmed that it is less than the set ratio, it means that there is more drainage. The process continues to determine whether the actual drainage flow rate is not less than the set drainage flow rate. If it is confirmed that it is not less than the set ratio, the opening of the first regulating valve 3 is reduced. If it is confirmed that it is less than the set ratio, the opening of the first regulating valve 3 is increased to ensure that the drainage processing capacity is maximized and production efficiency is improved.

[0110] The automatic switching of standby drainage control includes: first, determining whether the switching drainage setpoint is set; if it is set, it indicates that switching drainage control has been initiated; then, determining whether the actual liquid level reading L1 is not greater than the liquid level setpoint L1; if it is not greater, reducing the opening of the second regulating valve 24; if it is greater, increasing the opening of the second regulating valve 24, which can effectively control the drainage flow and ensure stable liquid level; if it is reset, it indicates that drainage is still controlled by the pilot-operated float drainage valve 19, and the second regulating valve 24 will be closed.

[0111] The control flow of the above system is an infinite loop process, which can be terminated directly by the stop operation or system exit button set on the human-machine interface or the "pause" or "alarm" command in the program.

[0112] The present invention also provides a method for shale gas separation using the shale gas collection and control system as described above.

[0113] Furthermore, in the above method, when the three-phase separator separates gas, liquid and sand, the controller controls the sand discharge port and sand suction port of the three-phase separator to alternately discharge and suction sand.

[0114] Furthermore, the above method controls the sand discharge port and sand suction port to alternately discharge and suction sand in the following manner:

[0115] The sand discharge port and the sand suction port alternately discharge and suction sand.

[0116] If the controller determines that the reading of the phase interface meter is greater than a preset threshold, then the timing is started;

[0117] Calculate the integer part of the ratio of the current time t to the preset time T; based on the parity of the integer part, alternately control the opening and closing of the first and second switching valves so that sand discharge and sand suction are performed alternately.

[0118] Furthermore, the above method also includes:

[0119] The controller calculates the ratio of the current discharge gas flow rate collected by the orifice plate flow meter to the current discharge liquid flow rate collected by the liquid flow meter;

[0120] If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0121] If the ratio is less than a preset ratio threshold and the current flow rate of the discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

[0122] The shale gas collection and control system and shale gas separation method provided in the embodiments of the present invention have the following technical effects:

[0123] The shale gas collection control system and shale gas separation method of this invention adopt an alternating sand suction and sand discharge control mode, which not only realizes the automatic sand discharge function, but also has the function of clearing blocked pipes, thus avoiding pipe blockage during the automatic sand discharge process.

[0124] The shale gas collection and control system of this invention can automatically adjust according to changes in the gas-liquid ratio of the material, and maximize the processing efficiency and improve the equipment utilization efficiency while ensuring that the exhaust water content and the exhaust liquid gas content meet the process requirements.

[0125] The shale gas collection and control system of this invention is equipped with a second safety shut-off valve in the drainage pipeline to prevent shale gas from flowing into the atmosphere and causing environmental pollution when the liquid level drops rapidly due to changes in material pressure and component ratio; thus ensuring production safety, reducing losses and avoiding environmental pollution.

[0126] The shale gas collection and control system of this invention is equipped with a first safety shut-off valve in the exhaust pipeline. This prevents the backflow liquid from directly entering the pipeline network through the exhaust pipeline when the liquid level rises rapidly due to changes in material pressure and component ratio, which would increase the water content of the output gas, cause dehydration failure, and fail to meet process requirements.

[0127] The shale gas collection and control system of this invention adopts two independent drainage control methods, namely a second regulating valve and a pilot-operated float drainage valve, which serve as backups for each other. When the float drainage valve fails and needs to be repaired, the regulating valve is intelligently switched to control the drainage, without stopping production and without affecting the mining progress.

[0128] The shale gas collection and control system of this invention has a high degree of automation, enabling unattended operation and effectively reducing personnel costs.

[0129] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A shale gas collection and control system, characterized in that, include: Hydrocyclone sand separator, three-phase separator, pilot-operated float drain valve and controller; The inlet of the cyclone desander is connected to the system material inlet for inputting fracturing reverse flow fluid; the exhaust port of the cyclone desander is connected to the air inlet of the three-phase separator, and the liquid outlet of the cyclone desander is connected to the liquid inlet of the three-phase separator. The exhaust port of the three-phase separator is connected to the gas phase outlet of the system, and the liquid outlet of the three-phase separator is connected to the liquid inlet of the pilot float discharge valve; the three-phase separator has a sand discharge port and a sand suction port; The outlet of the pilot float drain valve is connected to the system's drain outlet; The controller is used to control the sand discharge port and the sand suction port to alternately discharge and suction sand; The three-phase separator contains a vertically arranged sand baffle plate, which divides the inner cavity into a sand settling chamber and a liquid storage chamber. The sand discharge port and the sand suction port are respectively located at the bottom of the sand settling chamber; A phase interface instrument is also installed above the sedimentation chamber of the three-phase separator; The sand discharge port is connected to the sand discharge pipeline, and a first switch valve is installed on the sand discharge pipeline; The sand suction port is connected to the sand suction pipe, and a second switch valve is installed on the sand suction pipe; The sand discharge pipeline and the sand suction pipeline are connected to the pipeline between the liquid outlet of the pilot float discharge valve and the sewage outlet of the system. The controller is also configured to start timing if the reading of the phase interface instrument is greater than a preset threshold. Calculate the integer part of the ratio of the current time t to the preset time T; based on the parity of the integer part, alternately control the opening and closing of the first and second switching valves so that sand discharge and sand suction are performed alternately.

2. The system as described in claim 1, characterized in that, The drain port of the three-phase separator is connected to the first branch pipe and the second branch pipe. The first branch pipe is connected to the inlet of the pilot float drain valve, and the outlet of the second branch pipe is connected to the outlet of the pilot float drain valve. After converging into a common pipe, they are connected to the system drain port.

3. The system as described in claim 2, characterized in that, A second regulating valve is installed in the second branch pipeline; The liquid storage chamber of the three-phase separator is also equipped with a second liquid level transmitter; The controller is also used to control the second regulating valve to open to discharge the liquid discharged from the three-phase separator drain port when the pilot-operated float drain valve malfunctions or is out of service.

4. The system as described in claim 3, characterized in that, A first safety shut-off valve is installed on the connecting pipeline between the exhaust port of the three-phase separator and the gas phase outlet of the system. A second safety shut-off valve is also provided on the common pipeline formed by the connection between the outlet of the second branch pipeline and the outlet of the pilot float drain valve; The controller is also used to control the first safety shut-off valve and the second safety shut-off valve to cut off the pipeline and issue an alarm message when the second level transmitter detects that the liquid level in the storage chamber has reached the upper or lower limit of the liquid level.

5. The system as described in claim 1, characterized in that, A first regulating valve is also installed on the pipeline connecting the material inlet of the system and the inlet of the cyclone separator; an orifice plate flow meter is also installed on the pipeline connecting the exhaust port of the three-phase separator and the gas phase outlet of the system; a liquid flow meter is also installed on the pipeline between the liquid outlet of the pilot float drain valve and the sewage outlet of the system. The controller is also used to calculate the ratio of the flow rate of the currently discharged gas collected by the orifice plate flow meter to the flow rate of the currently discharged liquid collected by the liquid flow meter; If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve is controlled to reduce its opening. Otherwise, control the first regulating valve to increase its opening degree; If the ratio is less than a preset ratio threshold, and the flow rate of the currently discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve is controlled to reduce its opening. Otherwise, control the first regulating valve to increase its opening.

6. The system according to any one of claims 1-4, characterized in that, A mist eliminator is also installed at the exhaust port of the three-phase separator.

7. The system according to any one of claims 1-4, characterized in that, The three-phase separator is also equipped with a three-phase separator pressure equalization interface, and the pilot-operated float drain valve is also equipped with a pilot-operated float drain valve pressure equalization interface. The pressure equalization port of the three-phase separator is connected to the pressure equalization port of the pilot-operated float drain valve.

8. The system according to any one of claims 1-4, characterized in that, A first manual ball valve is also installed on the pipeline between the material inlet of the system and the inlet of the cyclone separator; A second manual ball valve is installed on the connecting pipe between the exhaust port of the cyclone separator and the air inlet of the three-phase separator. A seventh manual ball valve is installed on the connecting pipeline between the drain port of the cyclone separator and the inlet of the sand settling chamber of the three-phase separator. A fifth manual ball valve is also installed on the pipeline connecting the exhaust port of the three-phase separator to the gas phase outlet of the system.

9. The system as described in claim 1, characterized in that, The sand discharge pipeline is also equipped with an eighth manual ball valve; The sand suction pipe is also equipped with a ninth manual ball valve.

10. A method for shale gas separation using the shale gas collection and control system as described in claim 5; When the three-phase separator separates gas, liquid and sand, the controller controls the sand discharge port and sand suction port of the three-phase separator to alternately discharge and suction sand. The sand discharge port and sand suction port are controlled to alternately discharge and suction sand using the following method: If the controller determines that the reading of the phase interface meter is greater than a preset threshold, then the timing is started; Calculate the integer part of the ratio of the current time t to the preset time T; based on the parity of the integer part, alternately control the opening and closing of the first and second switching valves so that sand discharge and sand suction are performed alternately.

11. The method as described in claim 10, characterized in that, The method further includes: The controller calculates the ratio of the current discharge gas flow rate collected by the orifice plate flow meter to the current discharge liquid flow rate collected by the liquid flow meter; If the ratio is greater than or equal to a preset ratio threshold, and the current flow rate of the discharged gas is greater than or equal to a preset first flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening. If the ratio is less than a preset ratio threshold and the current flow rate of the discharged liquid is greater than or equal to a preset second flow rate threshold, then the first regulating valve is controlled to decrease its opening; otherwise, the first regulating valve is controlled to increase its opening.

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