Electric pump well liquid quantity calculation method

Abstract

The invention relates to an electric pump well liquid quantity calculation method, and belongs to the technical field of oil exploitation underground electric pumps. The method comprises the steps of firstly obtaining test data of an electric submersible pump unit under a normal working condition and a stable production period, obtaining a relation between motor power of an electric pump well and liquid quantity of the electric pump well in a mode of drawing a motor power-liquid quantity curve and then fitting the curve, and establishing an electric pump well liquid quantity calculation model based on the power-liquid quantity relation. In the testing process, the real-time power of an electric pump well motor is collected, the electric pump well liquid amount at the corresponding moment is obtained according to the power-liquid amount relation, and the electric pump well liquid amount is obtained by integrating the electric pump well liquid amount at each moment within the concerned time period. According to the method, in the testing process, the well does not need to be stopped, production is not affected, the cost and fault risks caused by the fact that an underground sensor needs to be placed in a traditional method are overcome, real-time metering of the electric pump well liquid amount is achieved, and the safety and reliability of operation of an electric submersible pump unit are guaranteed.

Description

Technical Field

[0001] This invention relates to a method for calculating the fluid volume of an electric pump well, belonging to the field of downhole electric pump technology in oil extraction. Background Technology

[0002] Electric pumped wells (EPBs) are the main method for increasing fluid and oil production and achieving stable and efficient production in the mid-to-late stages of oilfield development. Fluid volume measurement is crucial for EPB well operational condition diagnosis and production system adjustment. Currently, EPB well fluid volume is primarily measured through fluid discharged from the tubing. However, due to the unique location of the tubing, installing fluid volume sensors increases costs and the risk of malfunction. If the field environment does not support fluid volume sensing, real-time fluid volume data for the EPB well cannot be obtained.

[0003] To address this issue, Chinese patent application CN105888646A discloses a real-time online flow metering system and method for capillary pressure-measuring electric pump wells. This method uses a power balance method and a wellbore multiphase flow calculation method to measure the flow of fluid in the electric pump well. However, this method requires the installation of downhole pressure and temperature measuring devices, resulting in high costs.

[0004] The published text of Chinese patent application CN104298875A discloses a method for predicting the flow rate of a centrifugal pump based on power and differential pressure. The method calculates the flow rate by measuring the power of the centrifugal pump and the differential pressure between the inlet and outlet. However, this method requires the placement of a differential pressure sensor at the pump body downhole, which results in high costs.

[0005] Li Weiwei et al. published "Downhole Flow Measurement System for Submersible Electric Pumps" (see: Equipment Management and Maintenance, 2023(02):104-105). The method calculates the downhole flow rate of the pump by fitting the head-flow curve of the electric pump. However, this method requires the placement of a pressure sensor at the pump body, which is costly.

[0006] The Chinese patent application with publication number CN114412438A discloses a method for analyzing the operating conditions and measuring the flow rate of an electric pump well under digital conditions. The method corrects the head-flow characteristic curve of the electric pump by combining actual production data, calculates the head and obtains the flow rate of the electric pump. This method requires the installation of sensors to obtain the submersion degree of the well.

[0007] In summary, all existing electric pump well fluid metering systems require the installation of downhole sensors. Due to the harsh downhole environment of electric pump wells, the sensors are expensive, making the above-mentioned methods costly. Summary of the Invention

[0008] The purpose of this invention is to provide a method for calculating the fluid volume of an electric pump well, in order to solve the problem of high cost in existing electric pump well fluid volume calculation methods.

[0009] To achieve the above objectives, the present invention includes:

[0010] The technical solution of the present invention for calculating the fluid volume of an electric pump well includes the following steps: obtaining the real-time power value of the electric pump well motor, obtaining the corresponding instantaneous fluid volume according to the power-fluid volume relationship model; integrating the instantaneous fluid volume over the time range of interest to obtain the fluid volume of the electric pump well within the time range of interest;

[0011] The power-liquid volume relationship model is obtained by fitting the liquid volume of the electric pump well and the power of the electric pump well motor at the corresponding time when the electric pump well is in stable production under normal operating conditions.

[0012] Furthermore, the power-liquidity relationship model is fitted based on a bivariate quartic polynomial equation.

[0013] Furthermore, the bivariate quartic polynomial equation is:

[0014] Q = k1P + k2P 2 +k3P 3 +k4P 4 +k5

[0015] Where: Q represents liquid volume; P represents motor power; k1, k2, k3, and k4 are polynomial coefficients.

[0016] Furthermore, the power of the electric pump well motor is calculated based on the collected voltage, current, and power factor.

[0017] Furthermore, the formula for calculating the power of the electric pump well motor is as follows:

[0018]

[0019] Where: P represents the power of the motor; U represents the effective voltage of the motor; I represents the effective current of the motor; This represents the power factor of the motor.

[0020] Furthermore, the fluid volume of the electric pump well is obtained by a flow meter installed on the wellhead pipeline; the flow meter is installed and the fluid volume is obtained according to the following steps:

[0021] First, install a tee on the test valve. Install the upper valve on one of the tee ports for production. Connect the interface in the wellhead pipeline used to connect the integrated temperature and pressure transmitter 10 to the flow meter via a hose. Connect the other end of the flow meter to the other interface of the tee via a hose and the tee side valve. Open the tee side valve, back pressure valve, and oil jacket connecting valve, and close the upper valve and test valve to achieve liquid volume measurement.

[0022] This invention is a pioneering invention, and its beneficial effects are as follows: It obtains test data of submersible electric pump units under normal operating conditions and during stable production periods; obtains the relationship between the motor power and the well fluid volume by, for example, plotting a motor power-fluid volume curve and then fitting the curve; establishes a well fluid volume calculation model based on the power-fluid volume relationship; collects the real-time power of the electric pump motor during the test; obtains the well fluid volume at the corresponding time based on the power-fluid volume relationship; and then integrates the well fluid volume at each time point within the period of interest to obtain the well fluid volume.

[0023] The method of this invention does not require well shutdown and does not affect production during the testing process. It also overcomes the cost and failure risk caused by the need to place downhole sensors in traditional methods, and realizes real-time measurement of the fluid volume in the electric pump well, ensuring the safety and reliability of the submersible electric pump unit.

[0024] The present invention provides a technical solution for an electric pump well fluid volume calculation system, comprising a processor, the processor being used to execute a computer program to implement the following method steps: obtaining the real-time power value of the electric pump well motor, obtaining the corresponding instantaneous fluid volume according to the power-fluid volume relationship model; integrating the instantaneous fluid volume over a time range of interest to obtain the electric pump well fluid volume within the time range of interest;

[0025] The power-liquid volume relationship model is obtained by fitting the liquid volume of the electric pump well and the power of the electric pump well motor at the corresponding time when the electric pump well is in stable production under normal operating conditions.

[0026] Furthermore, the power-liquidity relationship model is fitted based on a bivariate quartic polynomial equation.

[0027] Furthermore, the bivariate quartic polynomial equation is:

[0028] Q = k1P + k2P 2 +k3P 3 +k4P 4 +k5

[0029] Where: Q represents liquid volume; P represents motor power; k1, k2, k3, and k4 are polynomial coefficients.

[0030] Furthermore, the power of the electric pump well motor is calculated based on the collected voltage, current, and power factor.

[0031] Furthermore, the formula for calculating the power of the electric pump well motor is as follows:

[0032]

[0033] Where: P represents the power of the motor; U represents the effective voltage of the motor; I represents the effective current of the motor; This represents the power factor of the motor.

[0034] Furthermore, the fluid volume of the electric pump well is obtained by a flow meter installed on the wellhead pipeline; the flow meter is installed and the fluid volume is obtained according to the following steps:

[0035] First, install a tee on the test valve. Install the upper valve on one of the tee ports for production. Connect the interface in the wellhead pipeline used to connect the integrated temperature and pressure transmitter 10 to the flow meter via a hose. Connect the other end of the flow meter to the other interface of the tee via a hose and the tee side valve. Open the tee side valve, back pressure valve, and oil jacket connecting valve, and close the upper valve and test valve to achieve liquid volume measurement.

[0036] This invention is a pioneering invention, and its beneficial effects are manifested in that: the method steps are formed into computer-readable program instructions, enabling the execution of the electric pump well fluid volume calculation method of this invention using an electric pump well fluid volume calculation system with a processor. The method of this invention first acquires test data of the submersible electric pump unit under normal operating conditions and during stable production periods. The relationship between the electric pump well motor power and the electric pump well fluid volume is obtained by, for example, plotting a motor power-fluid volume curve and then fitting the curve. An electric pump well fluid volume calculation model based on the power-fluid volume relationship is established. During the test, the real-time power of the electric pump well motor is collected, and the electric pump well fluid volume at the corresponding time is obtained according to the power-fluid volume relationship. Finally, the electric pump well fluid volume at each time is integrated within the period of interest to obtain the electric pump well fluid volume.

[0037] The method of this invention does not require well shutdown and does not affect production during the testing process. It also overcomes the cost and failure risk caused by the need to place downhole sensors in traditional methods, and realizes real-time measurement of the fluid volume in the electric pump well, ensuring the safety and reliability of the submersible electric pump unit. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the electric pump unit structure used in existing electric pump wells;

[0039] Figure 2 This is a schematic diagram of the wellhead pipeline and liquid flow direction before the flow meter is installed;

[0040] Figure 3 This is a schematic diagram showing the flow direction of the wellhead pipeline and the liquid after the flow meter is installed;

[0041] Figure 4 This is a schematic diagram of the power-flow curve and its fitting equation obtained in the embodiment.

[0042] The diagram includes: 1. Motor; 2. Protector; 3. Separator; 4. Centrifugal pump; 5. Pump outlet; 6. Pressure transmission sub; 7. Oil pipe; 8. Cable; 10. Temperature and pressure transmitter; 11. Flow meter; 12. Hose; 13. Tee. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0044] In the prior art, a typical submersible pump motor assembly used in an electric pump well is as follows: Figure 1 As shown, the system includes a motor 1, a protector 2, a separator 3, a centrifugal pump 4, a pump outlet 5, a pressure transmission sub 6, and an oil pipe 7 connected in series downhole to the wellhead of the electric pump well. The motor cable 8 connects to the surface from the side. The metering of the fluid volume of the electric pump unit is of great significance for the diagnosis of the operating conditions of the electric pump well and the adjustment of the production system.

[0045] To obtain the liquid volume of the electric pump unit at low cost, this invention connects a flow meter to the test valve to obtain sample data of flow rate and motor power 1 and fits them into a multivariate relationship model. Then, the motor power data is collected and calculated in real time, and the corresponding flow rate is obtained by substituting it into the fitted multivariate relationship model. The liquid volume of the electric pump well in the time period of interest is obtained by integrating the obtained real-time flow rate within the time range of interest.

[0046] Method Implementation Examples:

[0047] The present invention provides a method for calculating the fluid volume in an electric pump well, comprising the following steps:

[0048] Step 1) Set the motor pump frequency converter to the power frequency, select a time period when the electric pump well is in normal working condition, production is stable, and working status is good, connect a flow meter at the test valve to obtain the electric pump well liquid volume per second, calculate the electric pump well motor power at the corresponding time, and obtain sample data of liquid volume and power.

[0049] The wellhead pipe and liquid flow direction before the flow meter is installed are as follows: Figure 2 As shown, in step 1), the flow meter is installed as follows: First, install a tee 13 on the test valve (4#), connect the tank truck hose to the upper valve (5#) of the tee, open the upper valve (5#) and the test valve (4#) to enter the tank truck for production, and then (after meeting the conditions of normal operation and stable production) close the production valve (1#), back pressure valve (2#), and oil jacket connection valve (3#), vent the pipeline, remove the integrated temperature and pressure transmitter 10 and connect it to the hose 12, connect the hose to the flow meter 11, and connect the other end of the flow meter 11 to the tee side valve (6#) through the hose, as shown. Figure 3As shown; after fixing the flow meter 11, open the three-way side valve (6#), open the back pressure valve (2#), open the oil jacket connection valve (3#), and close the three-way upper valve (5#). At this time, the product enters the underground pipeline through the back pressure valve (2#) and is transported for production through the underground pipeline. After stabilization, start measurement. After the measurement is completed, close the three-way side valve (6#), open the three-way upper valve (5#) and the test valve (4#) to enter the tanker for production. Then close the back pressure valve (2#) and the oil jacket connection valve (3#), vent the system, install the integrated temperature and pressure transmitter 10, and disassemble the hose 12 and the flow meter 11. Then open the production valve (1#), the back pressure valve (2#), and the oil jacket connection valve (3#), close the three-way upper valve (5#) and the test valve (4#), and disassemble the three-way valve 13.

[0050] Repeat the above steps, take multiple measurements, and eliminate outliers. As the electric pump well operates over a long period, the pump unit may age or the well's operating conditions may change, requiring retesting to obtain new sample data.

[0051] Step 2) Use the sample data to plot the motor power-fluid volume curve and fit a polynomial equation;

[0052] In step 2), a motor power-liquid volume curve (PQ curve) is plotted with motor power as the abscissa and pump fluid volume as the ordinate, and fitted into a polynomial equation. The fitting formula is shown in formula (1):

[0053] Q = k1P + k2P 2 +k3P 3 +k4P 4 +k5 (1)

[0054] In the formula, Q represents the liquid volume, m 3 / s; P represents motor power, kW; k1~k4 are polynomial coefficients.

[0055] Step 3) Based on the polynomial equation obtained by fitting, the instantaneous liquid volume of the electric pump well is obtained through the real-time power value of the motor;

[0056] In step 3), the real-time power of the motor is calculated by the voltage, current and power factor collected in real time by the data acquisition device. The calculation method is shown in formula (2):

[0057]

[0058] In the formula, P represents the motor power (kW); U represents the effective voltage of the motor (V); and I represents the effective current of the motor (A). It represents the power factor and has no dimensions.

[0059] The instantaneous power is calculated using formula (2), and then substituted into formula (1) to solve for the instantaneous liquid volume.

[0060] Step 4) Integrate the instantaneous liquid volume to obtain the cumulative liquid volume value of the electric pump well;

[0061] In step 4), the instantaneous liquid volume is integrated to obtain the cumulative liquid volume. The calculation method is shown in formula (3):

[0062]

[0063] In the formula, Q represents the liquid volume value, m 3 / d; t1 represents the start time of flow accumulation, s; t2 represents the end time of flow accumulation, s; P represents the motor power, kW; k1~k4 are polynomial coefficients.

[0064] The method for calculating the fluid volume of an electric pump well according to the present invention will be further described in detail below with specific examples.

[0065] Step 1) In this example, the rated liquid volume is 150m³. 3 A submersible pump with a rated head of 1800m and a rated speed of 2850r / min was used as the test object. During the test, the pump inlet pressure was 5MPa, the pump inlet temperature was 95 degrees Celsius, and the operating frequency was 50HZ.

[0066] like Figure 2 , Figure 3 As shown, first install a tee 13 on the test valve (4#), connect the tank truck hose to the upper valve (5#) of the tee, open the upper valve (5#) and the test valve (4#) to enter the tank truck for production, then close the production valve (1#), back pressure valve (2#), and oil jacket connection valve (3#), vent the pipeline, remove the integrated temperature and pressure transmitter 10 and connect it to the hose 12, connect the hose 12 to the flow meter 11 (a mass flow meter is used in this embodiment), connect the other end of the flow meter 11 to the tee side valve (6#) through the hose, fix the flow meter, open the tee side valve (6#), open the back pressure valve (2#), open the oil jacket connection valve (3#), close the upper valve (5#) and the test valve (4#), and start the measurement after stabilization. After measurement, close the tee side valve (6#), open the tee upper valve (5#) and test valve (4#) to allow production in the tanker truck. Then close the back pressure valve (2#) and oil jacket connection valve (3#), vent the system, install the integrated temperature and pressure transmitter 10, and disassemble the hose 12 and flow meter 11. Subsequently, open the production valve (1#), back pressure valve (2#), and oil jacket connection valve (3#), close the tee upper valve (5#) and test valve (4#), and disassemble the tee 13.

[0067] Sample data of motor power for submersible electric pump units with different fluid volumes were obtained, and the sample data are shown in Table 1.

[0068] Table 1 Test Sample Data of Submersible Electric Pump Unit

[0069]

[0070] Step 2) Use the sample data to plot the motor input power-fluid volume curve and fit a polynomial equation;

[0071] Plot the motor input power-liquid volume curve with motor power on the x-axis and pump fluid volume on the y-axis. The fitted PQ curve is shown below. Figure 4 As shown in the figure (B1, B2, B3, and B4 in the table represent polynomial coefficients), the fitted polynomial equation is as follows:

[0072] Q = 0.00583P - 1.45715e -4 P 2 +1.62697e -6 P 3 -6.7537e -9 P 4 -0.08748 (4)

[0073] In the formula, Q represents the liquid volume, m 3 / s; P represents motor power, kW.

[0074] from Figure 4 From the fitting parameters, it can be seen that the fitted power-liquid volume curve R... 2 The sum of squared residuals equals 1, and the sum of squared residuals equals 6.59287E. -29 A value close to 0 indicates that the curve fits well.

[0075] Step 3) Based on the polynomial equation, obtain the instantaneous liquid volume of the electric pump well through the real-time power value of the motor;

[0076] The electrical parameters collected by the data acquisition device include voltage, current, and power factor. The acquisition frequency is once every 1 second. The instantaneous power is calculated by formula (5) and substituted into formula (4) to solve for the instantaneous liquid volume.

[0077]

[0078] In the formula, P represents the motor power (kW); U represents the effective voltage of the motor (V); and I represents the effective current of the motor (A). It represents the power factor and has no dimensions.

[0079] Step 4) Integrate the instantaneous liquid volume to obtain the cumulative liquid volume value of the electric pump well.

[0080] Oilfields are more concerned with the daily production of electric pump wells. The daily production is integrated on a daily basis. Table 2 shows the calculation results and error analysis of the daily fluid production of electric pump wells from January 20, 2024 to January 24, 2024 and January 31, 2024. The average relative error is 2.6%, which meets the needs of field use. This shows that the fluid production calculation method of electric pump wells based on the PQ curve can stably and accurately predict the fluid production of electric pump wells.

[0081] Table 2 Calculation results of fluid production from electric pump wells

[0082] date 1.20 1.21 1.22 1.23 1.24 1.31 <![CDATA[Calculating liquid production rate (m 3 / d)]]> 175.90 176.54 178.38 181.46 186.67 217.17 <![CDATA[Actual liquid production rate (m 3 / d)]]> 184 184.2 184.2 184.2 184.1 220.3 <![CDATA[Absolute error (m 3 / d)]]> 8.1 7.66 5.82 1.86 2.74 3.13 Relative error (%) 4.4％ 4.15％ 3.15％ 1％ 1.48％ 1.42％

[0083] In summary, the method for calculating fluid volume in electric pump wells of the present invention can stably and accurately obtain the instantaneous and cumulative fluid volume values ​​of electric pump wells without installing downhole sensing devices, providing a reliable reference for judging the operating conditions of submersible electric pump units and ensuring the safe operation of electric pump wells.

[0084] This embodiment presents a method for calculating fluid volume in electric submersible pump (ESP) wells. It acquires test data from the ESP unit using a flow meter, plots a motor power-fluid volume curve, and establishes a formula for calculating ESP well fluid volume based on this curve. The testing process does not require well shutdown and does not affect production. Furthermore, it overcomes the cost and failure risks associated with traditional methods that require downhole sensors, enabling real-time measurement of ESP well fluid volume and ensuring the safety and reliability of the ESP unit's operation. This method is simple to operate, low-cost, and highly stable for calculating ESP well fluid volume.

[0085] System Implementation Example:

[0086] The present invention provides an electric pump well fluid volume calculation system, including a processor, which executes a computer program stored in a memory to implement an electric pump well fluid volume calculation method of the present invention. The electric pump well fluid volume calculation method of the present invention has been described sufficiently in the method embodiments and will not be repeated here.

Claims

1. A method for calculating the fluid volume in an electric pump well, characterized in that, Includes the following steps: Obtain the real-time power value of the electric pump well motor, and obtain the corresponding instantaneous liquid volume according to the power-liquid volume relationship model; integrate the instantaneous liquid volume over the time range of interest to obtain the electric pump well liquid volume within the time range of interest. The power-liquid volume relationship model is obtained by fitting the liquid volume of the electric pump well and the power of the electric pump well motor at the corresponding time when the electric pump well is in stable production under normal operating conditions.

2. The method for calculating the fluid volume of an electric pump well according to claim 1, characterized in that, The power-liquidity relationship model is based on a binary quartic polynomial equation.

3. The method for calculating the fluid volume of an electric pump well according to claim 2, characterized in that, The bivariate quartic polynomial equation is: Q=k1P+k2P 2 +k3P 3 +k4P 4 +k5 Where: Q represents liquid volume; P represents motor power; k1, k2, k3, and k4 are polynomial coefficients.

4. The method for calculating the fluid volume of an electric pump well according to claim 1, characterized in that, The power of the electric pump well motor is calculated based on the motor's effective voltage, effective current, and power factor.

5. The method for calculating the fluid volume of an electric pump well according to claim 4, characterized in that, The formula for calculating the power of the electric pump well motor is as follows: Where: P represents the power of the motor; U represents the effective voltage of the motor; I represents the effective current of the motor; This represents the power factor of the motor.

6. The method for calculating the fluid volume of an electric pump well according to claim 1, characterized in that, The fluid volume of the electric pump well is obtained by using a flow meter installed on the wellhead pipeline; the flow meter is installed and the fluid volume is obtained according to the following steps: First, install a tee on the test valve. Install the upper valve on one of the tee ports for production. Connect the interface in the wellhead pipeline used to connect the integrated temperature and pressure transmitter 10 to the flow meter via a hose. Connect the other end of the flow meter to the other interface of the tee via a hose and the tee side valve. Open the tee side valve, back pressure valve, and oil jacket connecting valve, and close the upper valve and test valve to achieve liquid volume measurement.

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