Enhanced recovery mountain gas field ground gathering device

Abstract

The utility model discloses a mountain gas field ground gathering and transferring device of improving recovery ratio, including mountain top gas well unit, mountain top gas well unit is connected with siphon starting system through siphon conveying main pipeline, and siphon starting system is connected with mountain bottom gas gathering station. The utility model discloses a mountain gas field ground gathering and transferring device of improving recovery ratio, solves the problem of siphon easy gas block, interruption, thereby leading to the problem of too low recovery ratio of existing technology.

Description

Technical Field

[0001] This utility model belongs to the technical field of surface equipment for gas field development, specifically relating to a surface gathering and transportation device for mountain gas fields to enhance recovery rate. Background Technology

[0002] In recent years, the proportion of domestic mountain gas field development has gradually increased. These gas fields are generally characterized by complex terrain, scattered well locations, and large differences in production per well. Moreover, the gas reservoirs are mostly low-permeability and tight, and wellbore fluid accumulation is prone to occur in the middle and late stages of gas well production due to the decline in formation energy. Fluid accumulation increases the flow resistance of the wellbore, leading to a decrease in the production pressure differential of the gas well, and even causing the gas well to be shut down due to "water flooding," which seriously restricts the gas field's recovery rate.

[0003] Currently, surface gathering and transportation in mountain gas fields mainly adopts a wellhead pressurization and pipeline transportation model. This involves installing small booster units at the wellhead to pressurize the gas well's output before transporting it to the gathering station via surface pipelines. This model has several problems: First, the gas production of individual mountain gas wells fluctuates greatly, and some low-pressure wells require long-term reliance on booster units. A single unit can consume 80-120 kWh of energy per day, and intermittent well production leads to frequent start-ups and shutdowns, increasing equipment failure rates. Furthermore, the dispersed distribution of gas wells necessitates independent booster equipment for each well. When well production drops to the economic minimum and the well is shut down, the booster equipment remains idle for extended periods, resulting in significant resource waste. Second, traditional booster units rely on pressure to drive fluid discharge. For low-pressure wells with accumulated fluid below 0.5 MPa, insufficient inlet pressure from the booster unit can lead to cavitation, failing to effectively discharge the fluid accumulated at the bottom of the wellbore. This makes it difficult to extract the remaining natural gas in the reservoir, resulting in a recovery rate loss of 10%-15%. Moreover, the mountainous terrain is steep, and the pipeline laying from the wellhead to the gas gathering station requires the excavation of a large number of trenches. In some areas, boardwalks or tunnels need to be built, resulting in high engineering costs, long construction periods, and significant damage to the ecological environment.

[0004] Furthermore, existing siphon technology is rarely used in gas field gathering and transportation, mainly due to problems such as the easy disruption of siphon vacuum caused by gas-liquid two-phase flow and the interruption of the siphon effect caused by unstable elevation differences in mountainous terrain. Therefore, there is an urgent need for a ground-based device that can utilize the natural terrain of mountainous areas, stably achieve siphon transportation, and simultaneously handle liquid drainage and gathering and transportation, in order to solve the problems of low recovery rate and high development cost in mountainous gas fields. Utility Model Content

[0005] The purpose of this invention is to provide a surface gathering and transportation device for mountain gas fields to improve the recovery rate, and to solve the problems of siphon blockage and interruption that exist in the existing technology, which lead to low recovery rate.

[0006] The technical solution adopted in this utility model is a surface gathering and transportation device for mountain gas fields to improve recovery rate, including a mountain top gas well unit. The mountain top gas well unit is connected to a siphon start-up system through a siphon transportation main pipeline, and the siphon start-up system is connected to a mountain bottom gas gathering station.

[0007] The technical solution of this utility model is further characterized by the following: The mountaintop gas well unit includes a gas production tree, a wellbore liquid level gauge, and a wellhead filter; The bottom of the gas production tree is sealed and connected to the gas well shaft. Pressure sensors, temperature sensors and outlet valves are fixedly installed on the gas production tree. The liquid level gauge in the well shaft is an ultrasonic level gauge and is installed inside the gas well shaft. One end of the wellhead filter is sealed and connected to the outlet of the gas production tree, and the other end of the wellhead filter is sealed and connected to one end of the siphon delivery main pipeline.

[0008] The filter element of the wellhead filter is detachable, and the inlet end of the wellhead filter and the outlet end of the gas production tree are connected by flange sealing between the main siphon delivery pipeline.

[0009] The probe of the wellbore liquid level gauge is fixedly inserted into the wellbore, and the probe and the outlet of the gas production tree are on the same vertical plane.

[0010] The siphon start system includes a gas-liquid buffer tank, a vacuum pump, and a start valve assembly. The gas-liquid buffer tank is a tank-shaped structure with openings at both ends. The gas-liquid buffer tank is sealed to the main siphon conveying pipeline. One end of the start valve assembly is sealed to the outlet of the vacuum pump, and the other end is sealed to the main siphon conveying pipeline.

[0011] The starting valve group is a series pipeline valve assembly, including an electric shut-off valve and a check valve that are sealed and connected in sequence. One end of the electric shut-off valve is sealed and connected to the outlet of the vacuum pump through a flange, and the other end is sealed and connected to the inlet of the check valve through a flange. The outlet of the check valve is sealed and connected to the siphon conveying main pipeline through a flange.

[0012] The gas gathering station at the foot of the mountain includes a gas-liquid stabilization system and a control cabinet; The gas-liquid stabilization system includes a gas-liquid separator and a back pressure regulating valve. The gas-liquid separator is sealed to the siphon delivery main pipeline. The back pressure regulating valve is sealed to the outlet pipe section of the gas-liquid separator. The outlet pipe section of the gas-liquid separator is also connected to a compressor. A flow sensor is installed at the connection between the siphon delivery main pipeline and the inlet of the gas-liquid separator. The flow sensor is electrically connected to the control cabinet. The control cabinet is electrically connected to the outlet valve of the gas production tree, the pressure sensor, the temperature sensor, the wellbore liquid level gauge, the vacuum pump, the start valve group, the back pressure regulating valve, and the flow sensor at the outlet of the gas-liquid separator.

[0013] The gas-liquid buffer tank is equipped with a pressure relief valve at the top, which is electrically connected to the control cabinet.

[0014] A fixed bracket is fixed near the siphon start system on the main siphon conveying pipeline. The top of the fixed bracket is provided with an arc-shaped groove. The main siphon conveying pipeline is snapped into the arc-shaped groove, and a rubber buffer pad is provided between the main siphon conveying pipeline and the arc-shaped groove.

[0015] Compared with the prior art, the beneficial effects of this utility model are: (1) The surface gathering and transportation device for mountain gas fields provided by this utility model addresses the common problem of gas blockage or siphon effect interruption when traditional siphon technology is applied to gas field gathering and transportation. This is because the gas-liquid two-phase flow impact damages the pipeline vacuum, and the pressure difference fluctuation caused by the mountain elevation difference leads to pressure imbalance. Frequent manual intervention is required to restart the device, which seriously affects the continuity of gathering and transportation. The gas-liquid buffer tank can buffer the impact of the gas-liquid mixture flow and avoid local airflow turbulence from damaging the vacuum environment. When the pipeline vacuum drops below -0.05MPa (which is prone to causing gas blockage), the control cabinet can start the vacuum pump to replenish the vacuum and simultaneously adjust the pressure inside the tank through the pressure relief valve at the top of the gas-liquid buffer tank to ensure that the vacuum in the pipeline is stably maintained within the effective range of -0.06 to -0.08MPa. This design enables the continuous operation cycle of siphon transportation to reach more than 30 days, and the equipment failure rate is reduced to ≤1% / year, completely solving the core problem of frequent interruption of traditional siphon technology, thereby improving the recovery rate.

[0016] (2) The surface gathering and transportation device for mountain gas fields provided by this utility model does not require a wellhead booster unit, and only consumes a small amount of electricity during the siphon start-up stage (average daily energy consumption ≤20kWh, which saves more than 90% energy compared to traditional booster units); the surface pipeline does not require the excavation of high-cost trenches and can be laid naturally along the mountain, reducing the engineering cost by 40%-60%. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the surface gathering and transportation device for mountain gas fields to improve recovery rate according to this utility model; In the diagram, 1. Gas production tree, 2. Wellbore liquid level gauge, 3. Wellhead filter, 4. Siphon delivery main pipeline, 5. Fixed support, 6. Gas-liquid buffer tank, 7. Vacuum pump, 8. Gas-liquid separator, 9. Back pressure regulating valve, 10. Control cabinet, 11. Compressor. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] This utility model provides a surface gathering and transportation device for mountain gas fields to enhance oil recovery, such as... Figure 1 As shown, it includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline 4, and the siphon start-up system is connected to a mountain bottom gas gathering station.

[0020] The mountaintop gas well unit includes a gas production tree 1, a wellbore liquid level gauge 2, and a wellhead filter 3. The bottom of the gas production tree 1 is sealed to the gas wellbore. Pressure sensors, temperature sensors, and an outlet valve are fixedly installed on the gas production tree 1. The wellbore liquid level gauge 2 is an ultrasonic level gauge installed inside the gas wellbore. One end of the wellhead filter 3 is sealed to the outlet of the gas production tree 1, and the other end of the wellhead filter 3 is sealed to one end of the siphon delivery main pipeline 4. The filter element of the wellhead filter 3 has a detachable structure. The inlet end of the wellhead filter 3 and the outlet end of the gas production tree 1 are both sealed with flanges to the siphon delivery main pipeline 4. The probe of the wellbore liquid level gauge 2 is fixedly inserted into the gas wellbore, and the probe and the outlet of the gas production tree 1 are on the same vertical plane.

[0021] The siphon start-up system includes a gas-liquid buffer tank 6, a vacuum pump 7, and a start-up valve assembly. The gas-liquid buffer tank 6 is a tank-shaped structure with openings at both ends, and it is sealed to the main siphon conveying pipeline 4. The gas-liquid buffer tank 6 is located at a critical bend in the main siphon conveying pipeline 4. One end of the start-up valve assembly is sealed to the outlet of the vacuum pump 7, and the other end is sealed to the main siphon conveying pipeline 4. The start-up valve assembly is a series-connected pipeline valve assembly, including an electrically operated shut-off valve and a check valve that are sealed to each other in sequence. One end of the electrically operated shut-off valve is sealed to the outlet of the vacuum pump 7 via a flange, and the other end is sealed to the inlet of the check valve via a flange. The outlet of the check valve is sealed to the main siphon conveying pipeline 4 via a flange. The gas gathering station at the foot of the mountain includes a gas-liquid stabilization system and a control cabinet 10. The gas-liquid stabilization system includes a gas-liquid separator 8 and a back pressure regulating valve 9. The gas-liquid separator 8 is sealed to the siphon conveying main pipeline 4. The back pressure regulating valve 9 is sealed to the outlet pipe section of the gas-liquid separator 8. The outlet pipe section of the gas-liquid separator 8 is also connected to a compressor 11, which supplies gas to the downstream pipeline. A flow sensor is installed at the connection between the siphon conveying main pipeline 4 and the inlet of the gas-liquid separator 8. The flow sensor is electrically connected to the control cabinet 10. The control cabinet 10 is connected to the gas gathering tree. The outlet valve, pressure sensor, temperature sensor, wellbore liquid level gauge 2, vacuum pump 7, start valve group, back pressure regulating valve 9, and flow sensor of gas-liquid separator 8 are electrically connected; the top of gas-liquid buffer tank 6 is equipped with a pressure relief valve, which is electrically connected to control cabinet 10; a fixed bracket 5 is fixed near the siphon start system of siphon conveying main pipeline 4, the top of fixed bracket 5 is equipped with an arc-shaped groove, the siphon conveying main pipeline 4 is clamped in the arc-shaped groove, and a rubber buffer pad is provided between the siphon conveying main pipeline 4 and the arc-shaped groove.

[0022] The working principle of this utility model is as follows: First, the foundation for siphon operation is established by fixing the gas wellbore, gas production tree 1, wellbore liquid level gauge 2, and wellhead filter 3 at the top of the mountain gas field or at a higher elevation. The gas-liquid separator 8, back pressure regulating valve 9, and control cabinet 10 are fixed at the bottom of the mountain or at a lower elevation, so that a natural height difference of 50-200m is formed between the wellhead at the top of the mountain and the gas gathering station at the bottom of the mountain. This height difference can generate the gravitational potential energy required for the siphon effect, providing the basic driving force for subsequent gas-liquid transportation. At the same time, the gas-liquid separator 8 at the gas gathering station at the bottom of the mountain is connected to the wellhead filter 3 at the top of the mountain through the siphon transportation main pipeline 4, and the main pipeline is fixed by the fixed bracket 5 to prevent the pipeline from shifting due to gravity and damaging the transportation path.

[0023] Before starting the siphon, a preliminary status check is performed via control cabinet 10: Read the data from the pressure and temperature sensors on the gas production tree 1 to confirm that the wellhead pressure is ≥0.2MPa; then read the monitoring data from the wellbore liquid level gauge 2 to confirm that the liquid level in the gas wellbore is ≥0.5m, ensuring that there is enough liquid to fill the pipeline and avoid evacuation during startup; next, check the valve status: close the outlet valve of the gas production tree 1 and the inlet valve of the gas-liquid separator 8, and open the valve connected to the vacuum pump 7 to ensure that the vacuum pump and the siphon delivery main pipeline 4 are unobstructed.

[0024] When the siphon starts, a vacuum environment is established in the pipeline, triggering gas-liquid flow: Start vacuum pump 7. The vacuum pump removes air from the main siphon delivery pipeline 4 through the series electric shut-off valve → check valve. The check valve can prevent gas and liquid in the main pipeline from flowing back into the vacuum pump and avoid equipment damage. Control cabinet 10 monitors the vacuum degree in the main pipeline in real time. When the vacuum degree reaches -0.08MPa and stabilizes for 5 minutes, the vacuum pump is stopped and the electric shut-off valve of the start valve group is closed. Slowly open the inlet valve of the gas-liquid separator 8, and then gradually open the outlet valve of the gas production tree 1. At this time, the natural gas and accumulated liquid in the wellbore are driven by the dual forces of the wellhead pressure of 0.2-1MPa and the negative pressure of the main pipeline, passing through the gas production tree 1 and the wellhead filter 3 in sequence, and entering the siphon conveying main pipeline 4. When the flow rate of the gas-liquid mixture in the main pipeline reaches more than 100m³ / h, the siphon effect is officially established.

[0025] After the siphon is established, a continuous gas-liquid two-phase flow is formed in the main pipeline: the height difference between the wellhead at the top of the mountain and the gas gathering station at the bottom of the mountain generates gravitational potential energy, which is superimposed with the pressure difference between the wellhead pressure (0.2-1 MPa) and the gas gathering station pressure (0.1-0.3 MPa) at the bottom of the mountain, and together drive the gas-liquid mixture to flow along the main pipeline to the bottom of the mountain. The gas-liquid buffer tank 6 at the bend of the siphon conveying main pipeline 4 can buffer the impact of gas-liquid flow, avoid local airflow turbulence from disrupting the vacuum environment, and ensure the stable advancement of the gas-liquid two-phase flow. After the gas-liquid mixture is transported to the bottom of the mountain, it enters the interior of the gas-liquid separator 8 through the inlet. The separator separates the gas and liquid according to the density difference. The separated natural gas is transported by the compressor 11 on the outlet pipe section. The separated liquid water / condensate oil flows into the sewage treatment stage through the bottom outlet of the separator, and is reinjected or discharged after treatment. The back pressure regulating valve 9 is connected in series on the natural gas outlet pipe section of the gas-liquid separator 8. The control cabinet 10 stabilizes the pressure at the end of the main pipeline at 0.1-0.3MPa by adjusting its opening, maintaining the pressure difference balance required for siphoning.

[0026] When an airlock occurs in the siphon pipe, the control cabinet 10 starts the vacuum pump 7 and opens the start valve group to replenish the vacuum until the vacuum level is restored to above -0.06MPa, thus eliminating the airlock. If the wellbore liquid level gauge 2 detects that the liquid level is below 0.3m, the control cabinet 10 will automatically close the outlet valve of the gas production tree 1 and stop the gas-liquid delivery. After the liquid level rises to above 0.5m, the siphon start-up process will be repeated. If the pressure inside the gas-liquid buffer tank 6 exceeds 1.2MPa, the pressure relief valve at the top of the tank will open under the control of the control cabinet 10 to release pressure and prevent the pressure inside the tank from being too high and damaging the main pipeline seal.

[0027] In summary, this invention utilizes the physical height difference to create a vacuum negative pressure to construct a siphon driving force, combined with control and gas-liquid stabilization components, to achieve low-energy and stable transportation of gas-liquid mixtures in mountain gas fields, while solving the problems of difficult drainage of accumulated liquid and easy interruption of siphon in traditional gathering and transportation methods.

[0028] Example 1 This embodiment provides a surface gathering and transportation device for mountain gas fields to enhance oil recovery, such as... Figure 1 As shown, it includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline 4, and the siphon start-up system is connected to a mountain bottom gas gathering station.

[0029] Example 2 This embodiment provides a surface gathering and transportation device for mountain gas fields to enhance oil recovery, such as... Figure 1As shown, the system includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline 4. The siphon start-up system is connected to a mountain bottom gas gathering station. The mountaintop gas well unit includes a gas production tree 1, a wellbore liquid level gauge 2, and a wellhead filter 3. The bottom of the gas production tree 1 is sealed to the gas wellbore. A pressure sensor, a temperature sensor, and an outlet valve are fixedly installed on the gas production tree 1. The wellbore liquid level gauge 2 is an ultrasonic level gauge installed inside the gas wellbore. One end of the wellhead filter 3 is sealed to the outlet of the gas production tree 1, and the other end of the wellhead filter 3 is sealed to one end of the siphon delivery main pipeline 4. The filter element of the wellhead filter 3 is a detachable structure. The inlet end of the wellhead filter 3 and the outlet end of the gas production tree 1 are both sealed with flanges to the siphon delivery main pipeline 4. The probe of the wellbore liquid level gauge 2 is fixedly inserted into the gas wellbore, and the probe and the outlet of the gas production tree 1 are on the same vertical plane.

[0030] Among them, the wellbore liquid level gauge 2 is ultrasonic with a measurement accuracy of ±5mm, and the wellhead filter 3 has a filtration accuracy of 10μm to prevent impurities from clogging the pipeline.

[0031] Example 3 This embodiment provides a surface gathering and transportation device for mountain gas fields to enhance oil recovery, such as... Figure 1 As shown, the system includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline 4. The siphon start-up system is connected to a mountain bottom gas gathering station. The mountaintop gas well unit includes a gas production tree 1, a wellbore liquid level gauge 2, and a wellhead filter 3. The bottom of the gas production tree 1 is sealed to the gas wellbore. A pressure sensor, a temperature sensor, and an outlet valve are fixedly installed on the gas production tree 1. The wellbore liquid level gauge 2 is an ultrasonic level gauge installed inside the gas wellbore. One end of the wellhead filter 3 is sealed to the outlet of the gas production tree 1, and the other end of the wellhead filter 3 is sealed to one end of the siphon delivery main pipeline 4. The filter element of the wellhead filter 3 is a detachable structure. The inlet end of the wellhead filter 3 and the outlet end of the gas production tree 1 are both sealed with flanges to the siphon delivery main pipeline 4. The probe of the wellbore liquid level gauge 2 is fixedly inserted into the gas wellbore, and the probe and the outlet of the gas production tree 1 are on the same vertical plane.

[0032] The siphon start-up system includes a gas-liquid buffer tank 6, a vacuum pump 7, and a start-up valve assembly. The gas-liquid buffer tank 6 is a tank-shaped structure with openings at both ends, and it is sealed to the main siphon conveying pipeline 4. The gas-liquid buffer tank 6 is located at a critical bend in the main siphon conveying pipeline 4. One end of the start-up valve assembly is sealed to the outlet of the vacuum pump 7, and the other end is sealed to the main siphon conveying pipeline 4. The start-up valve assembly is a series-connected pipeline valve assembly, including an electrically operated shut-off valve and a check valve that are sealed to each other in sequence. One end of the electrically operated shut-off valve is sealed to the outlet of the vacuum pump 7 via a flange, and the other end is sealed to the inlet of the check valve via a flange. The outlet of the check valve is sealed to the main siphon conveying pipeline 4 via a flange.

[0033] The siphon conveying main pipeline 4 uses L360N seamless steel pipe with a diameter of DN150-DN200, a design pressure of 6MPa, and a wall thickness determined by the height difference. The outer wall of the pipeline is coated with a 3PE anti-corrosion layer. A gas-liquid buffer tank 6 is installed at the critical inflection point of the siphon conveying main pipeline 4. The gas-liquid buffer tank 6 has a volume of 0.5-1m³ to prevent gas-liquid impact from damaging the siphon. The vacuum pump 7 has a rated vacuum of -0.098MPa and a power of 5.5kW. It is used to quickly remove air from the pipeline and establish a siphon vacuum environment.

[0034] Example 4 Based on Example 3, the bottom gas gathering station includes a gas-liquid stabilization system and a control cabinet 10; the gas-liquid stabilization system includes a gas-liquid separator 8 and a back pressure regulating valve 9, and the gas-liquid separator 8 is sealed to the siphon conveying main pipeline 4; the back pressure regulating valve 9 is sealed to the outlet pipe section of the gas-liquid separator 8, and the outlet pipe section of the gas-liquid separator 8 is also connected to a compressor 11; a flow sensor is provided at the connection between the siphon conveying main pipeline 4 and the inlet of the gas-liquid separator 8, and the flow sensor is electrically connected to the control cabinet 10; the control cabinet 10 is electrically connected to the outlet valve of the gas gathering tree 1, the pressure sensor, the temperature sensor, the wellbore liquid level gauge 2, the vacuum pump 7, the start valve group, the back pressure regulating valve 9, and the flow sensor at the outlet of the gas-liquid separator 8.

[0035] Among them, the gas-liquid separator 8 has a processing capacity of 10×10 4 m 3 / d, working pressure 2-4MPa, back pressure regulating valve 9 controls the pressure at the end of the pipeline to maintain the stability of the siphon pressure difference; control cabinet 10 is based on PLC controller (model S7-1200) and equipped with touch screen operation panel, which can monitor wellhead pressure, pipeline vacuum degree, liquid level, gas-liquid separator outlet flow in real time, and alarm and adjust when the parameters are abnormal.

[0036] Example 5 Based on Example 4, the gas-liquid buffer tank 6 is provided with a pressure relief valve at the top, and the pressure relief valve is electrically connected to the control cabinet 10; a fixed bracket 5 is fixed near the siphon start system of the siphon conveying main pipe 4, and an arc-shaped groove is provided at the top of the fixed bracket 5. The siphon conveying main pipe 4 is snapped into the arc-shaped groove, and a rubber buffer pad is provided between the siphon conveying main pipe 4 and the arc-shaped groove.

[0037] Example 6 This embodiment provides a surface gathering and transportation device for mountain gas fields to enhance oil recovery, such as... Figure 1 As shown, it includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline 4, and the siphon start-up system is connected to a mountain bottom gas gathering station.

[0038] The mountaintop gas well unit includes a gas production tree 1, a wellbore liquid level gauge 2, and a wellhead filter 3. The bottom of the gas production tree 1 is sealed to the gas wellbore. Pressure sensors, temperature sensors, and an outlet valve are fixedly installed on the gas production tree 1. The wellbore liquid level gauge 2 is an ultrasonic level gauge installed inside the gas wellbore. One end of the wellhead filter 3 is sealed to the outlet of the gas production tree 1, and the other end of the wellhead filter 3 is sealed to one end of the siphon delivery main pipeline 4. The filter element of the wellhead filter 3 has a detachable structure. The inlet end of the wellhead filter 3 and the outlet end of the gas production tree 1 are both sealed with flanges to the siphon delivery main pipeline 4. The probe of the wellbore liquid level gauge 2 is fixedly inserted into the gas wellbore, and the probe and the outlet of the gas production tree 1 are on the same vertical plane.

[0039] The siphon start-up system includes a gas-liquid buffer tank 6, a vacuum pump 7, and a start-up valve assembly. The gas-liquid buffer tank 6 is a tank-shaped structure with openings at both ends, and it is sealed to the main siphon conveying pipeline 4. The gas-liquid buffer tank 6 is located at a critical bend in the main siphon conveying pipeline 4. One end of the start-up valve assembly is sealed to the outlet of the vacuum pump 7, and the other end is sealed to the main siphon conveying pipeline 4. The start-up valve assembly is a series-connected pipeline valve assembly, including an electrically operated shut-off valve and a check valve that are sealed to each other in sequence. One end of the electrically operated shut-off valve is sealed to the outlet of the vacuum pump 7 via a flange, and the other end is sealed to the inlet of the check valve via a flange. The outlet of the check valve is sealed to the main siphon conveying pipeline 4 via a flange. The bottom gas gathering station includes a gas-liquid stabilization system and a control cabinet 10. The gas-liquid stabilization system includes a gas-liquid separator 8 and a back pressure regulating valve 9. The gas-liquid separator 8 is sealed to the siphon conveying main pipeline 4. The back pressure regulating valve 9 is sealed to the outlet pipe section of the gas-liquid separator 8. A flow sensor is installed at the connection between the siphon conveying main pipeline 4 and the inlet of the gas-liquid separator 8. The flow sensor is electrically connected to the control cabinet 10. The control cabinet 10 is electrically connected to the outlet valve of the gas gathering tree 1, the pressure sensor, the temperature sensor, the wellbore liquid level gauge 2, the vacuum pump 7, the start valve group, the back pressure regulating valve 9, and the flow sensor at the outlet of the gas-liquid separator 8. A pressure relief valve is installed on the top of the gas-liquid buffer tank 6. The pressure relief valve is electrically connected to the control cabinet 10. A fixed bracket 5 is fixed near the siphon start system of the siphon conveying main pipeline 4. The top of the fixed bracket 5 is provided with an arc-shaped groove. The siphon conveying main pipeline 4 is clamped in the arc-shaped groove, and a rubber buffer pad is provided between the siphon conveying main pipeline 4 and the arc-shaped groove.

[0040] In this implementation, a certain block of a mountain gas field was selected, and the elevation difference between the wellhead of the gas well at the top of the mountain and the gas gathering station at the bottom of the mountain met the requirement of a minimum height difference of 50m for siphon start-up; a DN150L360N seamless steel pipe with a total length of 800m was laid from the wellhead at the top of the mountain to the gas gathering station at the bottom of the mountain. A gas-liquid buffer tank was installed every 200m along the pipeline, and fixed supports were installed at the turning points to prevent the pipeline from shifting due to gravity; A gas production tree 1 is installed at the wellhead on the mountain top. The gas production tree 1 is equipped with a pressure sensor, an ultrasonic level gauge, and a filter 3. A gas-liquid separator 8, a back pressure regulating valve 9, and a vacuum pump 7 are installed at the gas gathering station at the bottom of the mountain. The control cabinet 10 is installed in the operating room of the gas gathering station and connects all sensors and actuators.

[0041] First, check the pressure at the top of the well (pressure ≥ 0.2 MPa) and the liquid level (liquid level ≥ 0.5 m to ensure there is enough liquid to start the siphon). Then check the status of the siphon pipeline valves: close the outlet valve of gas sampling tree 1 and the inlet valve of gas-liquid buffer tank 6, and open the valve connecting vacuum pump 7 to the siphon delivery main pipeline 4. Check control cabinet 10 to ensure that the pressure, liquid level, and vacuum sensors are displaying normally and there are no alarm signals.

[0042] Start vacuum pump 7 to begin evacuating air from the pipeline. Observe the pipeline vacuum level through control cabinet 10: when the vacuum level reaches -0.08MPa and stabilizes for 5 minutes, stop the vacuum pump and close the vacuum pump valve. Slowly open the inlet valve of gas-liquid separator 8, and then slowly open the outlet valve of gas harvesting tree 1, gradually increasing the opening to avoid excessive flow velocity impacting the pipeline; observe the pipeline flow sensor, when the flow rate reaches 100 m³ / h or more, it indicates that the siphon has been established, and gradually open the outlet valve of gas harvesting tree 1 and the inlet valve of gas-liquid separator 8 to full opening.

[0043] Then the control cabinet displays the following parameters in real time: wellhead pressure (target 0.2-0.8MPa), pipeline vacuum (target -0.06 to -0.08MPa), liquid level (target 0.3-1m), and natural gas flow rate at the gas-liquid separator outlet (record cumulative production). If the following abnormalities occur, adjust them via the control cabinet: If the pipeline vacuum level drops below -0.05MPa: start the vacuum pump to replenish the vacuum until the vacuum level recovers to above -0.06MPa; If the wellhead liquid level is below 0.3m: close the gas tree outlet valve and wait for the liquid level to rise to above 0.5m before repeating the siphon start-up steps; if the outlet pressure of gas-liquid separator 8 is above 0.3MPa: automatically open the back pressure regulating valve to reduce the end pressure and maintain the siphon pressure difference.

[0044] When the gas well is under maintenance or the production is too low, slowly close the outlet valve of the gas production tree 1, and then close the inlet valve of the gas-liquid separator 8; stop the control cabinet 10, record the daily gas production and liquid production data, and check the equipment status.

[0045] In this embodiment, the control cabinet 10 includes a Siemens S7-1200 PLC and a touch screen. The Siemens S7-1200 PLC is connected to the pressure sensor and temperature sensor on the gas production tree 1 of the mountain top gas well unit via analog signal lines to obtain wellhead pressure and temperature signals. It is also connected to the ultrasonic wellbore liquid level gauge 2 inside the gas well via analog signal lines. At the same time, it obtains the gas-liquid mixture flow signal from the flow sensor at the inlet connection of the siphon conveying main pipeline 4 and the gas-liquid separator 8, as well as the pressure signal from the pressure release valve at the top of the gas-liquid buffer tank 6, through electrical connection, providing comprehensive data support for siphon status judgment and control. Meanwhile, the PLC is connected to the outlet valve of the gas production tree 1 via control signal lines to control the opening and closing of the valve, and to the vacuum pump 7 of the siphon start system to control the start and stop (to replenish the vacuum, and to the electric shut-off valve of the start valve group to control the pipeline opening and closing). It is also connected to the back pressure regulating valve 9 of the bottom gas-liquid stabilization system to adjust the opening degree to maintain a pressure difference balance of 0.1-0.3MPa at the end of the main pipeline, ensuring the stability of the siphon effect. Meanwhile, the PLC is connected to the touch screen control panel of the control cabinet via an Ethernet interface, transmitting real-time data such as wellhead pressure, temperature, liquid level, pipeline vacuum, gas-liquid flow, equipment operating status, and alarm information (e.g., vacuum below -0.05MPa, liquid level below 0.3m) to the touch screen. Operators can view the data directly on the screen and manually preset parameters such as the lower limit of wellhead pressure (≥0.2MPa), liquid level threshold (≥0.5m for startup, ≤0.3m for shutdown), and pipeline vacuum range (-0.06 to -0.08MPa). They can also query historical equipment operating data. When parameters are abnormal, the PLC will trigger an alarm and automatically execute controls (e.g., starting the vacuum pump to replenish vacuum, closing the outlet valve) to ensure continuous and stable siphon delivery.

Claims

1. A surface gathering and transportation system for enhanced oil recovery in mountain gas fields, characterized in that, It includes a mountaintop gas well unit, which is connected to a siphon start-up system via a siphon delivery main pipeline (4), and the siphon start-up system is connected to a mountain bottom gas gathering station.

2. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 1, characterized in that, The mountaintop gas well unit includes a gas production tree (1), a wellbore liquid level gauge (2), and a wellhead filter (3); The bottom of the gas production tree (1) is sealed and connected to the gas well shaft. A pressure sensor, a temperature sensor and an outlet valve are fixedly installed on the gas production tree (1). The well shaft liquid level gauge (2) is an ultrasonic level gauge and is installed inside the gas well shaft. One end of the wellhead filter (3) is sealed and connected to the outlet of the gas production tree (1), and the other end of the wellhead filter (3) is sealed and connected to one end of the siphon conveying main pipeline (4).

3. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 2, characterized in that, The filter element of the wellhead filter (3) is a detachable structure. The inlet end of the wellhead filter (3) and the outlet end of the gas production tree (1) are connected by a flange seal between the main siphon conveying pipeline (4).

4. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 2, characterized in that, The probe of the wellbore liquid level gauge (2) is fixedly inserted into the wellbore, and the probe and the outlet of the gas production tree (1) are on the same vertical plane.

5. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 2, characterized in that, The siphon start system includes a gas-liquid buffer tank (6), a vacuum pump (7), and a start valve group; the gas-liquid buffer tank (6) is a tank-shaped structure with openings at both ends. The gas-liquid buffer tank (6) is sealed to the siphon conveying main pipeline (4). One end of the start valve group is sealed to the outlet of the vacuum pump (7), and the other end is sealed to the siphon conveying main pipeline (4).

6. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 5, characterized in that, The starting valve group is a series pipeline valve assembly, including an electric shut-off valve and a check valve that are sealed and connected in sequence; one end of the electric shut-off valve is sealed and connected to the outlet of the vacuum pump (7) through a flange, and the other end is sealed and connected to the inlet of the check valve through a flange; the outlet of the check valve is sealed and connected to the siphon conveying main pipeline (4) through a flange.

7. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 5, characterized in that, The gas gathering station at the bottom of the mountain includes a gas-liquid stabilization system and a control cabinet (10). The gas-liquid stabilization system includes a gas-liquid separator (8) and a back pressure regulating valve (9). The gas-liquid separator (8) is sealed to the siphon conveying main pipeline (4). The back pressure regulating valve (9) is sealed to the outlet pipe section of the gas-liquid separator (8). The outlet pipe section of the gas-liquid separator (8) is also connected to a compressor (11). A flow sensor is provided at the connection between the siphon conveying main pipeline (4) and the inlet of the gas-liquid separator (8). The flow sensor is electrically connected to the control cabinet (10). The control cabinet (10) is electrically connected to the outlet valve of the gas production tree (1), the pressure sensor, the temperature sensor, the wellbore liquid level gauge (2), the vacuum pump (7), the start valve group, the back pressure regulating valve (9), and the flow sensor at the outlet of the gas-liquid separator (8).

8. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 7, characterized in that, The gas-liquid buffer tank (6) is equipped with a pressure relief valve at the top, and the pressure relief valve is electrically connected to the control cabinet (10).

9. The enhanced oil recovery surface gathering and transportation device for mountain gas fields according to claim 1, characterized in that, The siphon conveying main pipe (4) is fixed with a fixed bracket (5) near the siphon start system. The top of the fixed bracket (5) is provided with an arc-shaped groove. The siphon conveying main pipe (4) is clamped in the arc-shaped groove, and a rubber buffer pad is provided between the siphon conveying main pipe (4) and the arc-shaped groove.

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