Metering method and system for low water yield of coal-bed gas well

Abstract

The invention relates to the field of coal-bed gas exploration and development, and particularly discloses a method and a system for metering the low water yield of a coal-bed gas well, which are used for solving the technical problems in the prior art that the water yield of the coal-bed gas well with low yield and intermittent water output is not accurately metered, the efficiency is low, and the whole-process closed-loop management cannot be realized. The system mainly comprises a wellhead metering device composed of a collecting barrel and a metering barrel, a transportation metering unit, a processing station receiving metering unit and a data recording and analyzing platform. According to the invention, a wellhead metering method of double-barrel isolation and static measurement is designed, intermittent incoming water is buffered and collected by the collecting barrel, and then high-precision volume metering is carried out when the metering barrel is in a completely static state, so that the interference of liquid level fluctuation on low-flow measurement is thoroughly overcome.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane exploration and development, specifically a method and system for measuring low water production in coalbed methane wells. Background Technology

[0002] In the field of coalbed methane (coal mine gas) exploration and development, the production process of coalbed methane wells relies on the continuous pumping of pressurized water from the coal reservoir through drainage equipment to reduce reservoir pressure and promote the desorption and production of methane gas adsorbed on the coal matrix surface. The daily water production at the wellhead is one of the key parameters reflecting reservoir dynamics, evaluating the effectiveness of drainage and pressure reduction, and optimizing drainage operation procedures (such as pump speed and pumping frequency). Accurate measurement of water production is of vital engineering guiding significance for calculating wellbore fluid column height, inverting bottom hole flowing pressure, evaluating pump efficiency, and preventing reservoir damage. It also forms the quantitative basis for achieving closed-loop management of the entire chain of drainage water from production, collection, transportation to harmless treatment, ensuring environmental compliance.

[0003] However, coalbed methane wells, especially low-yield wells in the later stages of production, exhibit significantly low flow rates and strong intermittency in their water production characteristics. The average daily water production is often less than 0.5 cubic meters, and the water output is uneven, with prolonged periods of dripping or even flow interruption. Faced with this unique operating condition, existing conventional continuous online flow meters (such as turbine flow meters and electromagnetic flow meters), due to their measurement principles requiring minimum flow rates and fluid continuity, often cannot accurately measure the water output, or may even fail to start. Currently, the industry commonly relies on manual inspection and measurement methods, where inspectors use a fixed-volume measuring cylinder to collect water output at the wellhead for a period of time, record the time it takes to fill, and then convert it into 24-hour water production. While this method is simple and direct, it has fundamental and insurmountable flaws: because the water output is intermittent and uneven, the short sampling measurement time (usually a few minutes to a dozen minutes) cannot represent the complex dynamics of water production throughout the day, leading to significant errors in the conversion results; if the measurement time is extended to pursue accuracy, then the practical constraints of on-site inspection timeliness and labor costs become apparent. This point-based measurement method, which relies heavily on human experience and has uncontrollable errors, not only distorts production data and affects scientific decision-making, but also makes it impossible to accurately verify the wellhead water production, subsequent transport volume, and treatment plant reception volume. This breaks the data chain, leaving hidden space for unauthorized discharge or transfer losses and creating dual risks to environmental protection and management. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for measuring low water production in coalbed methane wells. This method solves the problems in the prior art where intermittent low flow rates lead to insufficient measurement accuracy, and manual inspection methods suffer from significant errors and low efficiency, resulting in distorted production management decisions and environmental risks.

[0005] A method for measuring low water production in coalbed methane wells includes the following steps:

[0006] S1. Drained water is produced from the wellhead of the coalbed methane well, filtered, and then flows into the collection bucket of the wellhead metering device.

[0007] S2. When the liquid level in the collection tank reaches the preset high value H1, and the liquid level in the metering tank connected to the collection tank is 0, open valve V1 to allow the drainage water in the collection tank to flow into the metering tank.

[0008] S3. When the liquid level in the collection tank drops to the preset low value H2, close the valve V1;

[0009] S4. After the liquid level in the metering tank stabilizes, read its liquid level value H3 multiple times until the values ​​are consistent. Then open valve V2 to drain the water from the metering tank and calculate the volume of the water drained this time based on the volume parameters of the metering tank and the liquid level value H3.

[0010] S5. Record the start time, drainage time and drainage volume of each drainage, and calculate the cumulative drainage volume.

[0011] Preferably, it also includes a step of measuring the amount of goods transported:

[0012] Water is regularly transported and drained using water trucks equipped with level gauges.

[0013] Read and upload the liquid level value of the water truck, record the time and corresponding amount of each transport, and calculate the cumulative transport volume.

[0014] Preferably, it also includes a step of measuring the amount received at the processing station:

[0015] Install a water flow meter at the receiving point of the treatment station;

[0016] When receiving and draining water, record the cumulative flow values ​​of the water flow meter before and after receiving, calculate the amount received and the receiving time, and statistically analyze the cumulative amount received.

[0017] Preferably, it also includes a data comparison and analysis step:

[0018] The system performs statistical analysis on the cumulative values ​​of wellhead water production, transport volume, and reception volume within a specified time period, and compares the differences between the three values ​​to identify abnormalities in each stage.

[0019] A low-yield water production metering system for implementing the above-mentioned metering method in a coalbed methane well includes a wellhead metering device and a data recording and processing unit.

[0020] The wellhead metering device includes:

[0021] The collection bucket is used to receive filtered wellhead drainage water and is equipped with a first level gauge for monitoring the liquid level.

[0022] A metering tank is connected to the collection tank via a pipeline. The pipeline is equipped with a controlled valve V1, a second level gauge for monitoring the liquid level is installed inside the tank, and a drain port with a valve V2 is provided at the bottom.

[0023] The bottom of the collection bucket and / or the bottom of the metering bucket is designed as a funnel-shaped ramp structure;

[0024] The data recording and processing unit is used to receive the liquid level signals from the first liquid level gauge and the second liquid level gauge, control the opening and closing of valves V1 and V2, record time and liquid level data, and calculate the single and cumulative discharge volume.

[0025] Preferably, it also includes a transport metering unit, which includes a level gauge and a data transmission module installed on the water truck, for measuring and uploading the water truck's level data to the data recording and processing unit.

[0026] Preferably, it also includes a treatment station receiving metering unit, which includes a water flow meter installed at the treatment station receiving point for measuring the received discharge water flow rate and transmitting the data to the data recording and processing unit.

[0027] Preferably, the data recording and processing unit is further configured to: store, statistically analyze, and compare the received wellhead water production data, transport data, and receiving data, and to perform anomaly monitoring and tracing by comparing water volume data at different stages.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] By employing a dual-bucket isolation and static measurement method, high-precision automated metering of water production in coalbed methane wells with low and intermittent water output is achieved. The collection bucket of this invention is responsible for buffering and collecting water, while the metering bucket performs volumetric measurement in a completely static state, fundamentally eliminating dynamic interference, minimizing metering errors, and providing a reliable data foundation for the precise control of subsequent drainage and production systems.

[0030] By constructing an IoT data acquisition network covering the entire process of water production, transportation, and treatment, the management of water production and drainage has achieved a digital closed loop from single-point metering to full traceability. The system automatically collects the wellhead water production, the real-time liquid level of the transportation vehicle, and the flow rate received by the treatment station, and automatically correlates and summarizes the three data on the central platform. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for measuring low water production in coalbed methane wells according to Embodiment 1 of the present invention.

[0032] Figure 2 This is a system architecture diagram of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: Measurement method for low water production in coalbed methane wells

[0035] Reference Figure 1 The first embodiment of the present invention provides a method for measuring low water production in coalbed methane wells, comprising the following steps:

[0036] S101: Automated and precise measurement of wellhead water production.

[0037] Specifically, the automated and precise metering of wellhead water production is achieved through a dual-bucket isolation and static measurement method, enabling high-precision metering of low-yield and intermittent water output. The specific implementation is as follows:

[0038] Data Acquisition and Preprocessing: After being produced from the coalbed methane wellhead, the produced water first passes through a pipeline filter (using multi-stage filtration, including a primary coarse filter and a secondary precision filter) to remove any solid impurities such as coal dust and rock fragments that may be present in the water, preventing them from entering the metering device and causing blockage or wear. The filtered produced water flows into the collection tank of the wellhead metering device. A first level gauge L1 is installed in the collection tank for real-time, continuous monitoring of the liquid level. ,in Indicates time.

[0039] Metering Trigger and Transfer: When the first level gauge L1 detects that the liquid level in the collection tank has reached the preset high-level threshold H1 (e.g., 80% of the effective height of the tank), and the system confirms through the second level gauge L2 that the current liquid level in the metering tank connected to the collection tank is 0 (i.e., in an emptying standby state), the data recording and processing unit (such as a PLC controller or RTU) issues a control command to open the valve V1 connecting the two tanks. At this time, the drained water in the collection tank flows smoothly into the metering tank through the connecting pipeline under the action of gravity. This design ensures that the metering process starts from zero in the metering tank, avoiding the accumulation error of residual water.

[0040] Transfer Stop and Isolation: As the water flows, the liquid level in the collection tank drops. When the first level gauge L1 detects that the liquid level has dropped to a preset low threshold H2 (e.g., 5% of the effective height of the tank), the data recording and processing unit closes valve V1, severing the hydraulic connection between the two tanks. At this point, the metering tank becomes an independent, closed metering unit, and the water volume inside represents a single batch to be metered. Setting H2>0 prevents gas from being drawn into the pipeline, ensuring that only liquid is being metered.

[0041] Static precision metering: After valve V1 is closed, the system waits for a preset settling time. (For example, 30 seconds to 2 minutes, which can be adjusted according to the gas content of the water) to allow the liquid level in the metering tank to stabilize fully, eliminating fluctuations and air bubbles caused by water ingress. After the liquid level stabilizes, the system uses a high-precision second level gauge L2 to collect the liquid level value in the metering tank multiple times (for example, 3-5 times). When the maximum deviation between multiple consecutively collected liquid level values ​​is less than the preset allowable error. When the liquid level is ±0.5 mm (for example), it is considered that the liquid level has stabilized, and the average value of these readings is taken as the final liquid level value H3 for this measurement.

[0042] Subsequently, the system uses the pre-calibrated "level-volume" function of the metering tank. The precise volume of water extracted in this operation was calculated. The function Accuracy can be ensured by calibrating the metering cylinder segment by segment at the factory or on-site. The calculation formula can be expressed as:

[0043]

[0044] Drainage and Data Recording: After the volume calculation is completed, the data recording and processing unit opens the drain valve V2 at the bottom of the metering tank to completely drain the metered water into the downstream pipeline or temporary storage facility. Simultaneously, the system automatically records and stores the key data tuples for this metering event:

[0045]

[0046] in, This is the start time of valve V1 opening (i.e., the start of this metering cycle). The time for draining (or closing) valve V2 to open. This is the calculated single-batch water production volume. The system will use this... Cumulative water production added to this well middle:

[0047]

[0048] Afterward, the system resets, the metering tank is ready, and it waits for the liquid level in the collection tank to reach H1 again before starting the next automatic metering cycle. Through this cycle of "collection-isolation-static measurement-draining", the problem of inaccurate metering caused by continuous fluctuations in liquid level under low flow and intermittent flow conditions in traditional flow-through metering or single-tank metering is completely solved.

[0049] S102: Water volume measurement during transportation.

[0050] As a preferred embodiment of the metering method of the present invention, in order to realize the monitoring of water transfer after production, a step of measuring the transport volume is also included:

[0051] Specialized water trucks equipped with level gauges (such as radar level gauges or hydrostatic level sensors) and wireless data transmission modules (such as 4G / 5G DTUs) are used to regularly transport and drain water from various well sites. Specifically:

[0052] After the water truck finishes loading water and before unloading at the treatment station, the onboard system automatically reads the tank level. The corresponding water volume is calculated by combining the geometric dimensions of the tank (obtained through a "liquid level-volume" lookup table obtained from calibration). and The volume of goods transported this time. At the same time, the system automatically records the transportation time. The associated well number and vehicle ID are uploaded to the central data recording and processing unit via wireless network. The central unit aggregates the data from each vehicle to form a cumulative transport volume. database.

[0053] S103: Water volume measurement at the receiving stage of the treatment station.

[0054] As a preferred embodiment of the metering method of the present invention, to further close the management chain, a step of metering the amount received at the processing station is also included:

[0055] A high-precision flow meter (such as an electromagnetic flow meter) is installed at the inlet of the receiving pool or receiving pipeline of the wastewater treatment plant. When the water truck unloads water, the treatment plant system records the cumulative reading of the flow meter at the instant the receiving begins. Record the cumulative reading at the moment the reception ends. The amount received this time. The system also records the reception time. The corresponding water truck ID is then used to upload the data to the central unit, where it is aggregated into a cumulative receipt count. .

[0056] S104: Full-process data comparison and analysis and anomaly identification.

[0057] As a preferred embodiment of the measurement method of the present invention, in order to achieve intelligent management, a data comparison and analysis step is also included:

[0058] The central data recording and processing unit has a built-in data analysis engine that can perform statistical analysis according to specified time periods such as day, week, or month, or on a single well, single vehicle, or area basis. Core analyses include:

[0059] Production-transportation balance analysis: Calculates the production-transportation balance of a single well or a group of wells within the same time period. .in It refers to the cumulative amount of water that is clearly taken from that well (or that group of wells) in the transport record.

[0060] Operation-displacement balance analysis: Calculate the balance within the same time period. .in It represents the total volume transported by all water trucks.

[0061] Anomaly warning: The system sets a reasonable deviation threshold. and (For example, a percentage threshold or an absolute threshold). When The system will issue a warning, indicating a possible malfunction in the wellhead metering equipment, missing transport records, or unauthorized discharge at the well site. In such cases, the system issues an early warning, indicating potential leaks during transportation, metering errors at the treatment station, or data upload errors. The warning information is then communicated to management personnel via the monitoring platform and SMS, enabling rapid problem detection and tracing.

[0062] Example 2: Low-yield water metering system for coalbed methane wells

[0063] A second embodiment of the present invention provides a low-yield water production metering system for implementing the above-described metering method in coalbed methane wells. See [link to relevant documentation]. Figure 2 The system includes: a wellhead metering device, a data recording and processing unit, a transport metering unit, a processing station receiving metering unit, and a data fusion and analysis platform.

[0064] The wellhead metering device is the core of the system, and it includes:

[0065] Collection tank: The tank body is made of corrosion-resistant material, and its bottom is designed with a funnel-shaped sloping structure to facilitate the collection of deposited solid impurities to the drain valve at the lowest point, which can be manually or automatically drained periodically to prevent sludge from affecting liquid level measurement. The first liquid level gauge L1 is installed inside the tank.

[0066] Measuring tank: Connected to the bottom of the collection tank via a connecting pipe, which is equipped with a valve V1 controlled by the control system. The bottom of the measuring tank is also designed with a funnel-shaped sloping structure and is connected to a drain valve V2 to ensure that the water is completely drained after each measurement, eliminating "dead water zones" and improving measurement accuracy. A high-precision second level gauge L2 is installed inside the tank.

[0067] Control box: The field section with embedded data recording and processing unit (such as PLC / RTU), responsible for acquiring analog or digital signals from L1 and L2, controlling the switching of V1 and V2 according to preset logic (H1, H2, settling time, etc.), and calculating the single-cycle water volume. This unit is typically equipped with a wireless communication module (such as NB-IoT, 4G) to remotely transmit metering data to a central server.

[0068] The water transport metering unit consists of an onboard level gauge, a GPS positioning module, and an onboard terminal (including a data transmission module) installed on each water truck. The onboard terminal packages and uploads the level data, time, and location information.

[0069] The receiving metering unit of the treatment station consists of a water flow meter installed at the receiving point and its data acquisition and transmission device, which is responsible for uploading the received data.

[0070] The data fusion and analysis platform is the "brain" of the system, typically deployed in the cloud or as a central server in the mining area. It receives data streams from all wellheads, vehicles, and processing stations, and performs unified storage, correlation, and cleaning. The platform's built-in software modules implement:

[0071] Data warehouse: Stores raw data and calculation results in multiple dimensions such as time, hash number, and vehicle ID.

[0072] Calculation engine: Real-time calculation of cumulative water production Cumulative transport volume Cumulative number of received .

[0073] Analysis and early warning module: Executes the data comparison and analysis logic as described in S104, and dynamically calculates... and It then compares the results with a threshold and automatically generates an early warning event.

[0074] Visualization and Human-Machine Interface: Through PC client or mobile APP, managers can be shown real-time water production curves, historical data reports, water production-transportation-disposal balance diagrams, early warning lists, etc. for each well, and data traceability and query are supported.

[0075] System workflow and closed-loop management:

[0076] The system constructs a complete digital closed loop of "production-transfer-processing". Wellhead metering devices provide accurate "source data"; transportation and processing metering provide "process data" and "endpoint data"; and a data analysis platform performs comparisons throughout the entire process. If any link in the data is abnormal, the system can issue an alarm within minutes and quickly pinpoint the specific well, vehicle, or time period, transforming management from passive inspection to proactive monitoring, and from rough estimation to refined management, effectively eliminating blind spots in water management and environmental risks.

[0077] It should be noted that the parameters in the above embodiments, such as the high-order threshold H1, the low-order threshold H2, and the settling time, are... Deviation threshold All of these can be debugged and set by the implementers in actual application scenarios according to specific well conditions, water quality, communication conditions, etc., in order to achieve the best metering and management effect.

[0078] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring low water production in coalbed methane wells, characterized in that, Includes the following steps: S1. Drained water is produced from the wellhead of the coalbed methane well, filtered, and then flows into the collection bucket of the wellhead metering device. S2. When the liquid level in the collection tank reaches the preset high value H1, and the liquid level in the metering tank connected to the collection tank is 0, open valve V1 to allow the drainage water in the collection tank to flow into the metering tank. S3. When the liquid level in the collection tank drops to the preset low value H2, close the valve V1; S4. After the liquid level in the metering tank stabilizes, read its liquid level value H3 multiple times until the values ​​are consistent. Then open valve V2 to drain the water from the metering tank and calculate the volume of the water drained this time based on the volume parameters of the metering tank and the liquid level value H3. S5. Record the start time, drainage time and drainage volume of each drainage, and calculate the cumulative drainage volume.

2. The measurement method according to claim 1, characterized in that, It also includes the step of measuring the amount of goods transported: Water is regularly transported and drained using water trucks equipped with level gauges. Read and upload the liquid level value of the water truck, record the time and corresponding amount of each transport, and calculate the cumulative transport volume.

3. The measurement method according to claim 1 or 2, characterized in that, It also includes the process of measuring the amount received at the processing station: Install a water flow meter at the receiving point of the treatment station; When receiving and draining water, record the cumulative flow values ​​of the water flow meter before and after receiving, calculate the amount received and the receiving time, and statistically analyze the cumulative amount received.

4. The measurement method according to claim 3, characterized in that, It also includes data comparison and analysis steps: The system performs statistical analysis on the cumulative values ​​of wellhead water production, transport volume, and reception volume within a specified time period, and compares the differences between the three values ​​to identify abnormalities in each stage.

5. A low-yield water production metering system for implementing the metering method according to any one of claims 1 to 4, characterized in that, Includes wellhead metering devices and data recording and processing units; The wellhead metering device includes: The collection bucket is used to receive filtered wellhead drainage water and is equipped with a first level gauge for monitoring the liquid level. A metering tank is connected to the collection tank via a pipeline. The pipeline is equipped with a controlled valve V1, a second level gauge for monitoring the liquid level is installed inside the tank, and a drain port with a valve V2 is provided at the bottom. The bottom of the collection bucket and / or the bottom of the metering bucket is designed as a funnel-shaped ramp structure; The data recording and processing unit is used to receive the liquid level signals from the first liquid level gauge and the second liquid level gauge, control the opening and closing of valves V1 and V2, record time and liquid level data, and calculate the single and cumulative discharge volume.

6. The metering system according to claim 5, characterized in that, It also includes a transport metering unit, which includes a level gauge and a data transmission module installed on the water truck, used to measure and upload the water level data of the water truck to the data recording and processing unit.

7. The metering system according to claim 6, characterized in that, It also includes a treatment station receiving and metering unit, which includes a water flow meter installed at the receiving point of the treatment station for measuring the received discharge water flow and transmitting the data to the data recording and processing unit.

8. The metering system according to claim 7, characterized in that, The data recording and processing unit is further configured to store, statistically analyze, and compare the received wellhead water production data, transport data, and receiving data, and to monitor and trace anomalies by comparing water volume data at different stages.

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