Multi-dimensional differential pressure wet gas saturation measurement method

Abstract

The application discloses a kind of multi-dimensional differential pressure wet gas gas content determination methods, first, can determine the wet gas differential pressure measurement system between the inlet section and throat section of Venturi tube, between throat section and outlet section, and between inlet section and outlet section three-dimensional differential pressure value is arranged and obtains the three-dimensional differential pressure numerical value after wet gas flows through Venturi;Second, the density of the medium liquid phase of the wet gas to be measured, the density of gas phase, the structure parameters of Venturi tube and the flow loss of wet gas from inlet section to throat section are obtained by calibration;Finally, the gas content of the wet gas to be measured is calculated according to the above differential pressure, density, structure parameters and flow loss.The effect of the present application is that the gas content of wet gas is calculated only by multi-dimensional differential pressure value, without the help of radioactive source, sound wave, electromagnetic wave technology, which can reduce the cost of wet gas measurement equipment;The measurement result of gas content is relatively accurate, which can be applied to actual production to some extent.

Description

Technical Field

[0001] This invention relates to the field of oil and gas engineering, and specifically to a flow measurement method during the oil and gas extraction process. Background Technology

[0002] In the oil and gas industry, "wet gas" refers to natural gas extracted directly from the wellhead without dehydration and dehydrocarbonization treatment, containing small amounts of condensate oil, condensate water, and saturated water vapor, and with a high liquid holdup. Measuring the flow rate and gas content of wet gas has always been a challenge in wet gas meter technology, as its measurement error is significantly greater than that of other wet gases.

[0003] Current technologies for measuring moisture content mostly rely on radiation sources, which pose certain safety risks. Other methods use sound waves and electromagnetic waves, but these also involve more components and higher costs. Summary of the Invention

[0004] To address the above technical problems, this invention provides a method for measuring the gas content in moisture based on multi-dimensional differential pressure. This method relies solely on traditional differential pressure sensors for gas content measurement, eliminating safety hazards and requiring no additional measuring components, thus avoiding increased measurement costs. The main technical solutions employed are as follows: A method for determining the gas content of moist gas under multidimensional differential pressure includes the following steps: Step 1: Set up the moisture differential pressure measurement system; The moisture differential pressure measurement system includes a venturi tube. The moisture to be measured is connected to the venturi tube, and the differential pressure ΔP between the inlet section and the throat section of the venturi tube is obtained. 12 The differential pressure ΔP between the throat segment and the outlet segment 23 and the differential pressure ΔP between the inlet and outlet sections. 13 ; Step 2: Calibrate the density of the liquid phase in the moisture to be tested. and the density of the middle gas phase of moisture. ; Step 3: Calculate the gas content of the moisture to be measured. ; ; This refers to the flow loss of moisture from the inlet section to the throat section; These are the structural parameters of the Venturi tube; Density of the liquid phase in moisture ; Density of the middle gas phase of moisture . Attached Figure Description

[0005] Figure 1 This is a schematic diagram of the structure of a moisture differential pressure measurement system; Figure 2 This is a schematic diagram showing the distribution of the two differential pressure measuring components; Figure 3 This is a three-dimensional schematic diagram of the internal structure of rack 1; Figure 4 As in Example 2 Distribution diagram; Figure 5 For the numerous calibration groups in Example 2 Distribution map; Figure 6 This is a percentage error distribution chart of the gas content calculated from numerous experimental cases. Detailed Implementation

[0006] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0007] Example 1: A method for determining the gas content of moisture under multidimensional differential pressure includes the following steps: Step 1: Set up the moisture differential pressure measurement system; The moisture differential pressure measurement system includes a Venturi tube 2. The moisture to be measured is connected to the Venturi tube 2, and the differential pressure ΔP between the inlet section and the throat section of the Venturi tube 2 is obtained. 12 The differential pressure ΔP between the throat segment and the outlet segment 23 and the differential pressure ΔP between the inlet and outlet sections. 13 ; Step 2: Calibrate the density of the liquid phase in the moisture to be tested. and the density of the middle gas phase of moisture. ; Step 3: Calculate the gas content of the moisture to be measured. ; ; This refers to the flow loss of moisture from the inlet section to the throat section; These are the structural parameters of the Venturi tube; Density of the liquid phase in moisture ; Density of the middle gas phase of moisture ; Moisture flow loss from the inlet section to the throat section Venturi tube structural parameters Density of the liquid phase in moisture The density of the middle gas phase of moisture All were obtained through calibration.

[0008] As a further specific implementation, the venturi tube is connected to multiple differential pressure measuring components, each including three differential pressure sensors 3, which respectively acquire the differential pressure ΔP between the inlet section and the throat section of the venturi tube 2. 12 The differential pressure ΔP between the throat segment and the outlet segment 23 and the differential pressure ΔP between the inlet and outlet sections. 13 ; Each differential pressure measurement unit outputs a set of ΔP. 12 ΔP 23 and ΔP 13 Input it into step three to calculate the gas content. Take the gas content calculated from the outputs of all differential pressure measuring components. The average value is used as the final gas content. This is to avoid the influence of inaccurate differential pressure measurement by a single differential pressure measuring component, which could lead to larger errors in the gas content calculation.

[0009] like Figure 1 , 2 As shown in Figure 3, the moisture differential pressure measurement system includes a frame 1, with the venturi tube 2 horizontally fixed on the frame 1. A differential pressure measuring component is provided on the frame 1. The differential pressure measuring component includes a differential pressure sensor 3 mounted on the frame 1. At least two pressure taps 4 are fixedly connected to the outer wall of the venturi tube 2. Each pressure tap 4 communicates with the inner cavity of the venturi tube 2. The free ends of the pressure taps 4 are respectively connected to a DBB valve assembly 5. The DBB valve assembly 5 is connected to the differential pressure sensor 3 through a pressure tapping pipe. The vent of the DBB valve assembly 5 is also connected to a drain pipe.

[0010] The frame 1 has a cubic frame structure. The frame 1 includes a horizontally arranged base frame, and two vertical supports are arranged opposite each other on the upper surface of the base frame. The top of the two vertical supports is connected to the same top frame. The Venturi tube 2 is located inside the frame structure of the frame 1. The Venturi tube 2 is installed on the frame 1 by clamps. More specifically, the Venturi tube 2 is installed on the upper surface of the base frame of the frame 1 by clamps. The structure of the Venturi tube 2 is prior art. Its inner cavity includes a constriction section, a throat section and an expansion section arranged in sequence. In order to facilitate the connection of the Venturi tube 2 to the underwater production pipeline, flange rings are fixed at both ends of the Venturi tube 2.

[0011] In one specific embodiment, the outer wall of the Venturi tube 2 is provided with three pressure taps 4 in sequence along its length. The pressure taps 4 are arranged radially along the Venturi tube 2. The three pressure taps 4 of the same differential pressure measuring component are distributed on the same straight line. The tube wall of the Venturi tube 2 is provided with three pressure taps connecting the inside and outside of the Venturi tube 2 in the radial direction. The pressure taps correspond one-to-one with the pressure taps 4. The inner end of the pressure tap 4 is fixedly inserted into the corresponding pressure tap. The outer wall of the inner end of the pressure tap 4 is welded to the tube wall of the Venturi tube 2 around the outer end of the pressure tap. The three pressure taps 4 are respectively connected to the constriction section, throat section and expansion section of the Venturi tube 2 through the corresponding pressure taps.

[0012] Each pressure tapping tube 4 has a DBB valve assembly 5 connected to its free end. The DBB valve assembly 5 includes a connecting pipe section with an upstream shut-off valve, an intermediate vent valve, and a downstream shut-off valve connected in series. One end of the connecting pipe section is connected to the corresponding pressure tapping tube 4 via a flange, and the other end is connected to a shunt tee 6 via a flange. The differential pressure measuring assembly includes three differential pressure sensors 3, which are fixed to the vertical support of the frame 1. The shunt tee 6 is connected to each differential pressure sensor 3 via a pressure tapping tube. The first port of the shunt tee 6 is connected to the corresponding DBB valve assembly 5, the second port is connected to any one of the differential pressure sensors 3, and the third port is connected to any one of the other two differential pressure sensors 3. Thus, the three differential pressure sensors 3 can respectively measure the differential pressure ΔP between the venturi constriction section and the throat section. 12 The differential pressure ΔP between the laryngeal segment and the dilated segment 23 and the differential pressure ΔP between the contraction and expansion sections. 13 .

[0013] During routine measurements, the upstream and downstream shut-off valves are open, while the intermediate vent valve is closed, not the inner cavity of the connecting pipe section. The humid medium passes sequentially through the pressure tap 4, DBB valve assembly 5, shunt tee 6, and pressure tapping pipe to the differential pressure sensor 3. The DBB valve assembly (Double Block and Bleed, also known as a DBB valve, double-block vent valve, or double-closing double-stop valve) typically includes an upstream shut-off valve, a downstream shut-off valve, and an intermediate vent valve located between the upstream and downstream shut-off valves. The intermediate vent valve has a vent port, providing a sand / oil discharge opening for the pressure tap / pressure tapping pipe. During system operation, the vent port of the DBB valve assembly is opened periodically to allow small amounts of fine sand / heavy oil in the pressure tap / pressure tapping pipe to drain, preventing blockage caused by long-term accumulation of fine sand / heavy oil. The pressure tapping pipe is located outside the venturi tube, avoiding the need for complex pressure tapping channels inside the solid part of the venturi tube, thus reducing the system's manufacturing difficulty and cost. After the system has been running for a period of time, close the upstream and downstream shut-off valves and open the intermediate vent valve to release the sand and heavy oil in the DBB valve group 5, thus preventing blockage of the pressure tapping / pressure priming channel. Alternatively, close only the upstream shut-off valve and open the downstream shut-off valve and intermediate vent valve to release the sand and heavy oil in the diversion tee 6 and the pressure priming pipe. Figure 2 , 3 In this case, the pressure tapping pipe is not set completely upwards, but in order to enhance the discharge effect, the channel downstream of the vent is preferably extended upwards in sequence and finally reaches the differential pressure sensor 3, so that sand and heavy oil are discharged from the vent under the action of weight.

[0014] Because the system operates online for extended periods, two sets of the differential pressure measurement components are installed on rack 1 to improve redundancy and simultaneously measure gas content. This provides a more comprehensive computational basis. The two sets of differential pressure measuring components are located on either side of the centerline of the venturi tube 2. The free ends of the pressure tapping tubes 4 of the differential pressure measuring components are set obliquely upward, and the angle between the centerline of the pressure tapping tubes 4 and the horizontal plane is 45°.

[0015] Two sets of differential pressure measuring components are symmetrically arranged along the center line of the venturi tube 2. Three stabilizing rods 71 ​​are also strung between the two sets of differential pressure measuring components. Each stabilizing rod 71 corresponds to a shunt tee 6. The two ends of each stabilizing rod 71 are connected to the outer wall of the shunt tee 6 of the two sets of differential pressure measuring components. A stabilizing support 72 is connected to the middle of each stabilizing rod 71, and the stabilizing support 72 abuts against the outer wall of the venturi tube 2.

[0016] The vents of all DBB valve groups 5 are connected to the main vent pipe via vent pipes.

[0017] A temperature sensor 8 is also fixedly installed on the outer wall of the Venturi tube 2. The probe of the temperature sensor 8 is in contact with the Venturi tube 2. Specifically, a temperature measuring hole is provided at the end of the Venturi tube 2. This temperature measuring hole is a blind hole, and the bottom of the hole is preferably 2-5mm away from the inner wall of the Venturi tube 2. The probe of the temperature sensor 8 extends into the temperature measuring hole and is in contact with its bottom. The temperature sensor 8 is used to detect the temperature of the moisture inside the Venturi tube 2. Lifting lugs are fixed on the top frame of the frame 1 to facilitate the hoisting of the entire system.

[0018] Example 2: A Venturi tube structural parameter And the flow loss of moisture from the inlet section to the throat section. Calibration method: The parameters of Venturi tube No. 1 were set as follows: diameter of the contraction section = diameter of the expansion section = 119.94 mm; diameter of the throat section = 89.94 mm; multiple sets of calibration moisture were introduced into Venturi tube No. 1 to calibrate the structural parameters of the Venturi tube. And the flow loss of moisture from the inlet section to the throat section. ; The parameters of Venturi tube No. 2 were set as follows: diameter of the contraction section = diameter of the expansion section = 167.08 mm; diameter of the throat section = 93 mm; multiple sets of calibration moisture were introduced into Venturi tube No. 2 to calibrate the structural parameters of the Venturi tube. And the flow loss of moisture from the inlet section to the throat section. ; The parameters of Venturi No. 3 were set as follows: diameter of the contraction section = diameter of the expansion section = 165 mm; diameter of the throat section = 85 mm; multiple sets of calibration moisture were introduced into Venturi No. 2 to calibrate the structural parameters of the Venturi tube. And the flow loss of moisture from the inlet section to the throat section. ; The calibration moisture content covers a range of 90%-100%, and the volumetric flow rate of the gas phase in the calibration moisture covers a range of 100-1500 m³ / s. 3 / h, the temperature range for calibrated humidity is 18-22℃; any combination of the above parameters for humidity. Venturi tube structural parameters ; Calibrate the flow loss of moisture from the inlet section to the throat section. ; To calibrate the velocity of the humidified airflow through the Venturi inlet section; To calibrate the flow velocity of the moist airflow through the throat section of Venturi; To calibrate the differential pressure of the humidified airflow through the Venturi inlet and throat sections; To calibrate the mixed density of moisture; The mixed density of moisture in multiple Venturi calibration groups and the flow velocity through the Venturi inlet and throat sections were determined. , After extensive testing and calibration, it was found that... and It has a rough segmented correspondence, and a portion of the calibration results are randomly selected for plotting. Distribution relationship diagram, results as follows Figure 4 As shown; according to Figure 4 A proposed venturi tube structural parameter The possible values ​​are as follows: ; Based on the above Venturi tube structural parameters Several calibration groups were calculated. Although the specific values ​​of are different for each individual value, they fluctuate within a very small range, so they can be considered as constants. A portion of the calibration groups were randomly selected. The calculated values ​​were plotted, and the distribution map was drawn. The results are shown in Table 5. Figure 5 It can be seen that the flow loss of moisture from the inlet section to the throat section measured by multiple calibration groups The distribution is relatively concentrated, so a value of 1.5 is recommended.

[0019] Experimental example: Based on the calibration of Example 2 above and The value of is determined according to the method in Example 1, and the gas content GVF in the moisture is calculated. J (Calculation group), and compare it with the corresponding true gas content GVF T To compare them, calculate the relative percentage error (MAE) between the two, MAE = (GVF) / (GVF) J -GVF T ) / GVF T *100%; The percentage error distribution of a randomly selected portion of the test cases is shown in the figure. Figure 6 ;from Figure 6 It can be seen that the calibration used in Example 2 Value and The percentage error between the gas content calculated using the method of Example 1 and the actual gas content is within ±10%, indicating that the gas content calculated by the method of the present invention is relatively accurate and can be used as a practical reference.

[0020] Beneficial effects: The method of the present invention calculates the moisture content of gas solely through multidimensional differential pressure values, eliminating the need for radiation sources, sound waves, and electromagnetic wave technologies, thus reducing the cost of moisture metering equipment; the moisture content measurement results are relatively accurate and can be applied to actual production to a certain extent.

[0021] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A method for determining the gas content of multidimensional differential pressure moisture, characterized in that... Includes the following steps: Step 1: Set up the moisture differential pressure measurement system; The moisture differential pressure measurement system includes a venturi tube (2). The moisture to be measured is connected to the venturi tube (2), and the differential pressure ΔP between the inlet section and the throat section of the venturi tube (2) is obtained. 12 The differential pressure ΔP between the throat segment and the outlet segment 23 and the differential pressure ΔP between the inlet and outlet sections. 13 ; Step 2: Calibrate the density of the liquid phase in the moisture to be tested. and the density of the middle gas phase of moisture. ; Step 3: Calculate the gas content of the moisture to be measured. ; ； This refers to the flow loss of moisture from the inlet section to the throat section; These are the structural parameters of the Venturi tube; Density of the liquid phase in moisture ; Density of the middle gas phase of moisture .

2. The method for determining the gas content of multidimensional differential pressure moisture according to claim 1, characterized in that: The venturi tube is connected to multiple differential pressure measuring components, each including three differential pressure sensors (3). The three differential pressure sensors (3) respectively acquire the differential pressure ΔP between the inlet section and the throat section of the venturi tube (2). 12 The differential pressure ΔP between the throat segment and the outlet segment 23 and the differential pressure ΔP between the inlet and outlet sections. 13 ; Each differential pressure measurement unit outputs a set of ΔP. 12 ΔP 23 and ΔP 13 Input it into step three to calculate the gas content. ; Take the gas content calculated from the output of all differential pressure measuring components. The average value is used as the final gas content.

3. The method for determining the gas content of multidimensional differential pressure moisture according to claim 1, characterized in that: Moisture loss from the inlet section to the throat section Venturi tube structural parameters Density of the liquid phase in moisture The density of the middle gas phase of moisture All were obtained through calibration.

4. The method for determining the gas content of multidimensional differential pressure moisture according to claim 1, characterized in that: Venturi tube structural parameters The possible values ​​are as follows: 。 5. The method for determining the gas content of multidimensional differential pressure moisture according to claim 1, characterized in that: Moisture loss from the inlet section to the throat section The value is 1.

5.

6. A method for determining the gas content of multidimensional differential pressure moisture according to any one of claims 1-5, characterized in that: The moisture differential pressure measurement system includes a frame (1) on which a differential pressure measuring component is provided; The differential pressure measuring assembly includes a differential pressure sensor (3) mounted on the frame (1). At least two pressure taps (4) are fixedly connected to the outer wall of the venturi tube (2). The pressure taps (4) are all connected to the inner cavity of the venturi tube (2). The free ends of the pressure taps (4) are respectively connected to a DBB valve group (5). The DBB valve group (5) is connected to the differential pressure sensor (3) through a pressure tap. The vent of the DBB valve assembly (5) is also connected to a drain pipe.

7. The method for determining the gas content of multidimensional differential pressure moisture according to claim 6, characterized in that: The outer wall of the Venturi tube (2) is provided with three pressure tapping tubes (4) in sequence along its length direction. The pressure tapping tube between the DBB valve group (5) and the differential pressure sensor (3) is also provided with a shunt tee (6). The differential pressure measuring component includes three differential pressure sensors (3). The first port of the diversion tee (6) is connected to the corresponding DBB valve group (5), the second port of the diversion tee (6) is connected to any one of the differential pressure sensors (3), and the third port of the diversion tee (6) is connected to any one of the other two differential pressure sensors (3).

8. The method for determining the gas content of multidimensional differential pressure moisture according to claim 6, characterized in that: The vents of all DBB valve assemblies (5) are connected to the main vent pipe via vent pipes.

9. The method for determining the gas content of multidimensional differential pressure moisture according to claim 6, characterized in that: A temperature sensor (8) is also fixedly installed on the outer wall of the Venturi tube (2). The probe of the temperature sensor (8) is in contact with the Venturi tube (2) to detect the temperature of the moisture in the inner cavity of the Venturi tube (2).

Images