A remote monitoring method and intelligent control system for gas wellhead

Abstract

The present invention relates to the field of gas wellhead management technology, and specifically discloses a gas wellhead remote monitoring method and an intelligent control system, wherein the method comprises the following steps: S1: obtaining a curve of the minimum liquid-carrying flow rate changing with the production pressure difference and an opening-flow function; S2: obtaining the optimal production pressure difference of the gas well and setting the production pressure difference range; obtaining the optimal critical liquid-carrying flow rate and substituting it into the opening-flow function, and adjusting the opening of the valve on the gas production tree; S3: obtaining the formation pressure and the bottom hole flow pressure in real time, and calculating the comparative production pressure difference; when the comparative production pressure difference does not belong to the production pressure difference range, adjusting the casing pressure until the comparative production pressure difference is equal to the optimal production pressure difference. The present invention can maintain the production pressure difference of the gas well while preventing liquid accumulation, thereby ensuring the economic benefits and recovery rate of the gas well.

Description

Technical Field

[0001] The present invention relates to the technical field of gas wellhead management, and in particular to a gas wellhead remote monitoring method and an intelligent control system. Background Art

[0002] At present, the valve control on the gas production tree generally uses the most primitive manual operation. The well site needs to assign special personnel to be on duty or arrange personnel to patrol the wells irregularly. Manual operation of the valves on the gas production tree wastes a lot of manpower. Relying on the operator's experience, the valve opening adjustment on the gas production tree may not be accurate enough. A small number of gas production wellheads use remote switching strategies to switch valves and adjust the flow of wellhead throttle valves. According to the operating instructions issued by the on-duty personnel, the electric actuator performs various operations, which reduces the manpower investment to a certain extent. However, it still relies on remote on-duty personnel to analyze and judge before performing various operations, which may also cause the problem of inaccurate valve opening adjustment on the gas production tree.

[0003] In a Chinese patent with patent announcement number CN114233272B, a method for intelligent production control of natural gas wells is disclosed, and the scheme mainly includes well opening and closing control and valve opening control on the gas tree. However, in the process of valve opening control on the gas tree, the scheme does not give a specific degree of adjustment of the valve opening on the gas tree. The adjustment of the valve opening on the gas tree is not accurate enough, and the adjustment of the valve on the gas tree will affect the bottom hole pressure, and then affect the production pressure difference. If the production pressure difference is too small, the economic benefits are poor, and if the production pressure difference is too large, the gas well production will decrease rapidly and the recovery rate will be low. Summary of the invention

[0004] The purpose of the present invention is to provide a gas wellhead remote monitoring method and an intelligent control system to solve the above technical problems.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for remote monitoring of a gas wellhead comprises the following steps:

[0007] S1: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences, where the critical liquid carrying flow rate is the flow rate corresponding to the gas flow velocity when liquid begins to accumulate in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method, and the fitting formula is f(Q), to obtain a curve of the minimum liquid carrying flow rate changing with the production pressure difference;

[0008] Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q(K) is obtained;

[0009] S2: Obtain the optimal production pressure difference ΔP of the gas wellopt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value;

[0010] The optimum production pressure difference ΔP opt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ;

[0011] The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q(K) to obtain the standard opening K of the valve on the gas tree. sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ;

[0012] S3: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ΔP com =P str -P wel ;

[0013] When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time to calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

[0014] As a further solution of the present invention: the specific steps of obtaining the opening-flow function Q(K) are as follows:

[0015] Slowly reduce the opening of the valve on the gas tree at a set speed, and measure the flow at the valve on the gas tree in real time;

[0016] With the opening K of the valve on the gas tree as the x-axis coordinate and the flow m as the y-axis coordinate, the corresponding database points are generated in the coordinate system, and the data points are fitted by the least squares method to obtain the opening-flow curve Q(K).

[0017] As a further solution of the present invention: in the process of measuring the flow at the valve on the gas tree, n flow sensors are set at preset fixed distance intervals, n is a preset value, and the average value of the flow of the n flow sensors at the same time is obtained as the flow corresponding to the opening of the valve on the gas tree at that moment.

[0018] As a further solution of the present invention: in the process of calculating the mean, when the difference between the flow rate of a certain flow sensor and the mean is greater than a preset value, the flow rate of the flow sensor is discarded and the mean is recalculated.

[0019] As a further solution of the present invention: in the step S2, the opening range [Kmin, Kmax] of the valve on the gas tree is set, and the following steps are performed:

[0020] When the standard opening K sta ≤K min When the valve opening on the gas tree is adjusted to K min ;

[0021] When the standard opening K sta ≥K max When the valve opening on the gas tree is adjusted to K max .

[0022] As a further solution of the present invention: when the comparative production pressure difference ΔP com ∈[ΔP opt -p, ΔP opt +p], the casing pressure is not adjusted.

[0023] As a further solution of the present invention: when adjusting the casing pressure P cas To complete the set process, perform the following steps:

[0024] Set casing pressure adjustment range [P' cas ,P" cas ];

[0025] When the casing pressure P cas In the casing pressure adjustment range [P' cas ,P" cas ], it is impossible to make the comparative production pressure difference equal to ΔP opt When adjusting the casing pressure P cas The set makes the comparative production pressure difference ΔP com ∈[ΔP opt -p, ΔP opt +p].

[0026] A remote intelligent control system for a gas production wellhead, comprising:

[0027] Fitting module: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences. The critical liquid carrying flow rate is the flow rate corresponding to the gas flow rate when liquid accumulation begins in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method. The fitting formula is f(Q), and the curve of the minimum liquid carrying flow rate changing with the production pressure difference is obtained.

[0028] Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q(K) is obtained;

[0029] Adjustment module: Obtain the optimal production pressure difference ΔP of the gas well opt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value;

[0030] The optimum production pressure difference ΔP opt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ;

[0031] The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q(K) to obtain the standard opening K of the valve on the gas tree. sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ;

[0032] Optimization module: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ΔP com =P str -P wel ;

[0033] When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time, and calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

[0034] Beneficial effects of the present invention: In the present invention, the critical liquid carrying flow rate under different production pressure differences is first determined and fitted. In actual situations, the production pressure difference of the gas well will affect the critical liquid carrying flow rate. When the production pressure difference of the gas well increases, the flow loss in the oil pipe is large, the liquid carrying capacity is insufficient, the lifting is abnormal, the liquid accumulation is large, and the liquid cannot be completely carried out by the gas. The currently commonly used critical liquid carrying flow rate calculation formula is: q is the critical liquid-carrying flow rate, T is the reservoir temperature, Z is the compression coefficient of natural gas at T temperature and Pwel, and d is the diameter of the oil pipe; then determine the optimal production differential pressure of the gas well, and determine the critical liquid-carrying flow rate of the gas well based on the optimal production differential pressure, and adjust the opening of the valve on the gas tree. The opening adjustment of the valve on the gas tree will affect the bottom hole flow pressure, and then affect the production differential pressure. Therefore, first determine the opening of the valve on the gas tree to prevent the subsequent adjustment of the opening of the valve on the gas tree from affecting the production differential pressure. At the same time, adjust the opening of the valve on the gas tree according to the critical liquid-carrying flow rate to prevent liquid accumulation in the gas well; then adjust the casing pressure to ensure a reasonable production differential pressure. While preventing liquid accumulation, maintain the production differential pressure of the gas well to ensure the economic benefits and recovery rate of the gas well. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] Figure 1 The present invention is a flow chart of a method for remotely monitoring a gas wellhead. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1 As shown, the present invention is a method for remote monitoring of a gas wellhead, comprising the following steps:

[0039] S1: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences, where the critical liquid carrying flow rate is the flow rate corresponding to the gas flow velocity when liquid begins to accumulate in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method, and the fitting formula is f(Q), to obtain a curve of the minimum liquid carrying flow rate changing with the production pressure difference;

[0040] Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q(K) is obtained;

[0041] S2: Obtain the optimal production pressure difference ΔP of the gas well opt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value;

[0042] The optimum production pressure difference ΔP opt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ;

[0043] The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q(K) to obtain the standard opening K of the valve on the gas tree. sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ;

[0044] S3: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ΔPcom =P str -P wel ;

[0045] When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time to calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

[0046] It should be noted that the critical liquid carrying flow rate under different production pressure differences is first determined and fitted. In actual situations, the production pressure difference of the gas well will affect the critical liquid carrying flow rate. When the production pressure difference of the gas well increases, the flow loss in the tubing is large, the liquid carrying capacity is insufficient, the lifting is abnormal, the liquid accumulation is large, and the liquid cannot be completely carried out by the gas. The commonly used critical liquid carrying flow rate calculation formula is: q is the critical liquid-carrying flow rate, T is the reservoir temperature, Z is the compression coefficient of natural gas at T temperature and Pwel, and d is the diameter of the oil pipe; then determine the optimal production differential pressure of the gas well, and determine the critical liquid-carrying flow rate of the gas well based on the optimal production differential pressure, and adjust the opening of the valve on the gas tree. The opening adjustment of the valve on the gas tree will affect the bottom hole flow pressure, and then affect the production differential pressure. Therefore, first determine the opening of the valve on the gas tree to prevent the subsequent adjustment of the opening of the valve on the gas tree from affecting the production differential pressure. At the same time, adjust the opening of the valve on the gas tree according to the critical liquid-carrying flow rate to prevent liquid accumulation in the gas well; then adjust the casing pressure to ensure a reasonable production differential pressure. On the premise of preventing liquid accumulation, maintain the production differential pressure of the gas well to ensure the economic benefits and recovery rate of the gas well.

[0047] In another preferred implementation of the present invention, the specific steps for obtaining the opening-flow function Q(K) are as follows:

[0048] Slowly reduce the opening of the valve on the gas tree at a set speed, and measure the flow at the valve on the gas tree in real time;

[0049] With the opening K of the valve on the gas tree as the x-axis coordinate and the flow m as the y-axis coordinate, the corresponding database points are generated in the coordinate system, and the data points are fitted by the least squares method to obtain the opening-flow curve Q(K).

[0050] It is worth noting that first, by changing the valve opening to observe and measure the corresponding flow changes, a set of data points about the opening and flow are collected; then these data points are intuitively displayed in a two-dimensional coordinate system to show the relationship between the opening and flow; finally, the least squares method is used to find the best function match for the data by minimizing the sum of squares of the errors, and to find a curve that best represents the actual data, thereby more accurately describing the functional relationship between the opening and flow.

[0051] In another preferred implementation of the present invention, in the process of measuring the flow at the valve on the gas tree, n flow sensors are set at preset fixed distance intervals, n is a preset value, and the average value of the flow of the n flow sensors at the same time is obtained as the flow corresponding to the opening of the valve on the gas tree at that moment.

[0052] It can be understood that by setting up multiple flow sensors at preset fixed distance intervals, the flow can be measured from different angles and positions, thereby reducing the problem of inaccurate flow measurement caused by individual sensor failure or errors. Calculating the mean can effectively eliminate the random error of a single measurement point and improve the accuracy and stability of flow measurement.

[0053] In another preferred implementation of the present invention, in the process of calculating the mean, when the difference between the flow rate of a certain flow sensor and the mean is greater than a preset value, the flow rate of the flow sensor is discarded and the mean is recalculated.

[0054] It should be noted that the benefits of doing so include: since the flow sensor may have faults or errors, resulting in a large difference between the flow data measured by it and the data of other sensors, by setting a preset difference threshold, these outliers can be effectively excluded to avoid a large impact on the final mean calculation result. After discarding the outliers, the recalculated mean can better reflect the actual situation, thereby improving the accuracy of flow measurement.

[0055] In another preferred implementation of the present invention, in step S2, the opening range [Kmin, Kmax] of the valve on the gas tree is set, and the following steps are performed:

[0056] When the standard opening K sta ≤K min When the valve opening on the gas tree is adjusted to K min ;

[0057] When the standard opening K sta ≥K max When the valve opening on the gas tree is adjusted to K max .

[0058] It should be noted that the benefit of this is to protect the equipment and extend its service life, while also ensuring production safety and efficiency. The specific reasons include: ensuring that the gas tree can still work normally at the minimum opening, preventing the natural gas from not flowing normally due to too small an opening; preventing safety hazards caused by too large an opening and problems beyond the working range of the equipment, and ensuring that the gas tree can still operate stably at the maximum opening.

[0059] In another preferred embodiment of the present invention, when the comparative production pressure difference ΔP com ∈[ΔP opt -p, ΔP opt +p], the casing pressure is not adjusted.

[0060] In another preferred embodiment of the present invention, when adjusting the casing pressure P cas To complete the set process, perform the following steps:

[0061] Set casing pressure adjustment range [P' cas ,P" cas ];

[0062] When the casing pressure P cas In the casing pressure adjustment range [P' cas ,P" cas ], it is impossible to make the comparative production pressure difference equal to ΔP opt When adjusting the casing pressure P cas The set makes the comparative production pressure difference ΔP com ∈[ΔP opt -p, ΔP opt +p].

[0063] It is worth noting that this is because setting the casing pressure adjustment range can prevent the casing pressure from being too high or too low. If the casing pressure is too high, it may cause oil and gas to be discharged from the formation prematurely, thereby affecting production; if the casing pressure is too low, it may not be possible to effectively extract oil and gas from the formation, which will also affect production.

[0064] A remote intelligent control system for a gas production wellhead, comprising:

[0065] Fitting module: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences. The critical liquid carrying flow rate is the flow rate corresponding to the gas flow rate when liquid accumulation begins in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method. The fitting formula is f(Q), and the curve of the minimum liquid carrying flow rate changing with the production pressure difference is obtained.

[0066] Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q(K) is obtained;

[0067] Adjustment module: Obtain the optimal production pressure difference ΔP of the gas well opt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value;

[0068] The optimum production pressure difference ΔPopt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ;

[0069] The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q(K) to obtain the standard opening K of the valve on the gas tree. sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ;

[0070] Optimization module: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ΔP com =P str -P wel ;

[0071] When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time, and calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

[0072] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A remote monitoring method for a gas wellhead, It is characterized in that The following steps are involved: S1: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences. The critical liquid carrying flow rate is the flow rate corresponding to the gas flow velocity when liquid begins to accumulate in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method. The fitting formula is f(Q), and the curve of the minimum liquid carrying flow rate changing with the production pressure difference is obtained. Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q (K) is obtained; S2: Obtain the optimal production pressure difference ΔP of the gas well opt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value; The optimum production pressure difference ΔP opt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ; The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q (K) to obtain the standard opening K of the valve on the gas tree sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ; S3: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ∆P com =P str -P wel ; When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time to calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

2. A gas wellhead remote monitoring method according to claim 1, It is characterized in that The specific steps for obtaining the opening-flow function Q (K) are as follows: Slowly reduce the opening of the valve on the gas tree at a set speed, and measure the flow at the valve on the gas tree in real time; With the opening K of the valve on the gas tree as the x-axis coordinate and the flow Q as the y-axis coordinate, the corresponding database points are generated in the coordinate system, and the data points are fitted by the least squares method to obtain the opening-flow curve Q (K).

3. A gas wellhead remote monitoring method according to claim 2, It is characterized in that In the process of measuring the flow at the valve on the gas tree, n flow sensors are set at preset fixed distance intervals, n is a preset value, and the average flow of the n flow sensors at the same time is obtained as the flow corresponding to the opening of the valve on the gas tree at that moment.

4. A gas wellhead remote monitoring method according to claim 3, It is characterized in that In the process of calculating the mean value, when the difference between the flow rate of a certain flow sensor and the mean value is greater than a preset value, the flow rate of the flow sensor is discarded and the mean value is recalculated.

5. A gas wellhead remote monitoring method according to claim 1, It is characterized in that In step S2, the opening range of the valve on the gas tree is set [K min , K max ] and perform the following steps: When the standard opening K sta ≤K min When the valve opening on the gas tree is adjusted to K min ; When the standard opening K sta ≥K max When the valve opening on the gas tree is adjusted to K max .

6. A gas wellhead remote monitoring method according to claim 1, It is characterized in that When the comparative production pressure difference When the casing pressure is not adjusted.

7. A gas wellhead remote monitoring method according to claim 1, It is characterized in that When adjusting the casing pressure P cas During the process, perform the following steps: Set casing pressure adjustment range [P' cas， P'' cas ]; When the casing pressure P cas In the casing pressure adjustment range [P' cas， P'' cas ], it is impossible to make the comparative production pressure difference equal to ΔP opt When adjusting the casing pressure P cas Make the comparative production pressure difference .

8. A remote intelligent control system for gas wellheads. It is characterized in that include: Fitting module: Calculate the critical liquid carrying flow rate Q of the gas well under different production pressure differences. The critical liquid carrying flow rate is the flow rate corresponding to the gas flow rate when liquid accumulation begins in the wellbore, and generate corresponding data points in the coordinate system. Fit the data points by the least squares method. The fitting formula is f(Q), and the curve of the minimum liquid carrying flow rate changing with the production pressure difference is obtained. Taking the opening degree K of the valve on the gas tree as the independent variable and the flow rate Q of the valve on the gas tree as the dependent variable, the opening degree-flow rate function Q (K) is obtained; Adjustment module: Obtain the optimal production pressure difference ΔP of the gas well opt , set the production pressure difference range [ΔP opt -p, ΔP opt +p], where p is the preset pressure difference deviation value; The optimum production pressure difference ΔP opt Substitute into the fitting formula f(Q) to obtain the optimal critical liquid carrying flow rate Q opt ; The optimal critical liquid carrying flow rate Q opt Substitute the opening-flow function Q (K) to obtain the standard opening K of the valve on the gas tree sta , and adjust the opening of the valve on the gas tree to the standard opening K sta ; Optimization module: Real-time acquisition of formation pressure P str and bottom hole pressure P wel , and calculate the comparative production pressure difference ΔP com =P str -P wel ; When the comparative production pressure difference When the casing pressure P is adjusted at a preset fixed pressure interval cas , and obtain the bottom hole flow pressure in real time, and calculate the comparative production pressure difference until the comparative production pressure difference is equal to ΔP opt .

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