Flow calculation method of layered water injection well and water injection device

Abstract

The invention relates to the technical field of oil field water injection wells, in particular to a flow calculation method of a separate layer water injection well and a water injection device, and aims to solve the problems that a flow meter is damaged and flow measurement data is inaccurate in an existing separate layer water injection technology. The method comprises the following steps that single-layer water injection is conducted, specifically, water injection is conducted on the ith layer, and the wellhead water injection flow is the actual water injection flow Qi of the layer; coefficient calculation: calculating a flow coefficient Di of the layer according to a flow formula; flow calculation: calculating Qi of each layer in real time according to a flow formula during water injection; and flow regulation and control, wherein when the difference value between the Qi and the injection allocation quantity Qpi exceeds a set value, the opening degree of the water nozzle is adjusted to change the Ki. According to the method, the quantity Qi of each layer can be calculated in real time according to a flow formula only by arranging a pressure sensor to obtain the nozzle front pressure P1i and the nozzle rear pressure P2i, a calculation model is simplified, the problems caused by a flow meter are avoided, and the calculation complexity, the degree of dependence on experimental data and the inaccurate calculation result caused by many parameters are reduced.

Description

Technical Field

[0001] This invention relates to the field of oilfield water injection well technology, and in particular to a method for calculating the flow rate of a stratified water injection well and a water injection device. Background Technology

[0002] The fourth-generation intelligent stratified water injection technology in oilfields has solved the technical challenge of remote online measurement and adjustment of stratified water injection wells. This technology connects the downhole water distributor and the surface control device via cables or wireless transmission to facilitate real-time control of the downhole nozzle opening and closing, enabling online testing and adjustment of the water injection volume for each layer. However, in practical applications, it has been found that the flow meters used in this technology are prone to damage under the influence of the high temperature and high pressure environment downhole, resulting in poor measurement accuracy and severe data drift, which seriously restricts the widespread application of stratified water injection technology. Summary of the Invention

[0003] The purpose of this invention is to provide a method for calculating the flow rate of a stratified water injection well and a water injection device to solve the problems of flow meter damage and inaccurate flow measurement data caused by the use of flow meters in existing stratified water injection technologies.

[0004] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0005] A method for calculating the flow rate of a stratified water injection well includes the following steps:

[0006] Single-layer water injection: Other water injection sections are closed, and water is injected only into the i-th layer. The wellhead injection flow rate is the actual injection flow rate Q for that layer. i ;

[0007] Coefficient Calculation: Calculate the flow coefficient D for this layer based on the flow formula. i The flow formula is

[0008] Among them, K i ΔP is the faucet opening value. i =P 1i -P 2i P 1i For the pressure in front of the mouth, P 2i ρ is the pressure behind the nozzle, and ρ is the density of the injected water.

[0009] Flow rate calculation: During water injection, the actual water injection flow rate Q of each layer is calculated in real time according to the flow rate formula. i ;

[0010] Flow control: Set the injection volume Q for each layer pi When the actual water injection flow rate Q i With the amount of injection Q piWhen the difference exceeds the set value, adjust the faucet opening to change the faucet opening value K. i Until the actual water injection flow rate Q i With the amount of injection Q pi The difference is not greater than the set value.

[0011] Furthermore, in the flow control step, the actual water injection flow rate Q i With the amount of injection Q pi The difference does not exceed the injection volume Q pi 10% of

[0012] |Q i -Q pi |≤10%×Q pi .

[0013] Furthermore, when the actual water injection flow rate Q i Exceeding the dosage Q pi After reducing the flow rate by 10%, decrease the nozzle opening; when the actual water injection flow rate Q... i Below the dosage Q pi After reducing it by 10%, increase the water tap opening.

[0014] Furthermore, pressure sensors are installed before and after the water tap to measure the pressure P in front of the tap. 1i And mouth pressure P 2i .

[0015] In another aspect of the present invention, a water injection device for a stratified water injection well is proposed, which adopts the above-mentioned method for calculating the flow rate of a stratified water injection well and includes a shell, a water distributor, a drive motor and a pressure sensor.

[0016] The water distributor and the drive motor are mounted on the housing, and the drive motor is used to adjust the opening of the water nozzle of the water distributor;

[0017] The two pressure sensors are used to measure the pressure P in front of the mouth. 1i And mouth pressure P 2i .

[0018] Furthermore, the water injection device of the stratified water injection well also includes a signal transmission unit;

[0019] The signal transmission unit is used for two-way communication between the surface and underground.

[0020] Furthermore, the water injection device for the stratified water injection well also includes a ground control unit;

[0021] The ground control unit receives the signal from the pressure sensor through the signal transmission unit and sends a flow regulation signal to the water distributor to control the opening of the water tap.

[0022] Furthermore, the water injection device of the stratified water injection well also includes an upper connector and a lower connector, which are respectively connected to the two ends of the outer shell for pipe string connection.

[0023] Furthermore, the water distributor includes a control calculation module, which receives instructions from the ground control unit and controls the drive motor to adjust the water nozzle opening.

[0024] Furthermore, the water injection device of the stratified water injection well also includes a transmission component, which is used to connect the transmission motor and the water distributor. The transmission motor adjusts the opening of the water nozzle through the transmission component.

[0026] In summary, the technical effects achieved by this invention are as follows:

[0027] The method for calculating the flow rate of a stratified water injection well provided by this invention includes the following steps:

[0028] Single-layer water injection: Other water injection sections are closed, and water is injected only into the i-th layer. The wellhead injection flow rate is the actual injection flow rate Q for that layer. i ;

[0029] Coefficient Calculation: Calculate the flow coefficient D for this layer based on the flow formula. i The flow formula is

[0030] Among them, K i ΔP is the faucet opening value. i =P 1i -P 2i P 1i For the pressure in front of the mouth, P 2i ρ is the pressure behind the nozzle, and ρ is the density of the injected water.

[0031] Flow rate calculation: During water injection, the actual water injection flow rate Q of each layer is calculated in real time according to the flow rate formula. i ;

[0032] Flow control: Set the injection volume Q for each layer pi When the actual water injection flow rate Q i With the amount of injection Q pi When the difference exceeds the set value, adjust the faucet opening to change the faucet opening value K. i Until the actual water injection flow rate Q i With the amount of injection Q pi The difference is not greater than the set value.

[0033] The flow rate calculation method for stratified water injection wells provided by this invention only requires conducting a single-layer water injection test beforehand to obtain the flow rate coefficient D of that layer when performing simultaneous multi-layer water injection.i Then, multiple layers of water can be injected simultaneously. During water injection, there is no need to install a flow meter downhole; only pressure sensors need to be installed before and after the nozzle to obtain the pressure P before the nozzle. 1i And mouth pressure P 2i The actual water injection flow rate Q of each layer can be calculated in real time based on the flow formula. i , and then based on the actual water injection flow rate Q i With the amount of injection Q pi The difference is used to determine whether the nozzle opening needs adjustment. Since there's no need to use a flow meter downhole, problems such as flow meter damage and inaccurate flow data measurement are avoided. Simultaneously, the flow coefficient D... i The use of this method simplifies the flow formula, reduces the complexity of the flow calculation model, and improves the model's practicality and computational efficiency. Because it uses fewer parameters, it is more suitable for practical engineering applications, especially when dealing with complex geological conditions and dynamically changing nozzle openings. It provides a more intuitive and easy-to-implement solution, avoiding computational complexity, dependence on experimental data, and inaccurate calculation results caused by a large number of parameters. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the water injection device for a stratified water injection well provided in an embodiment of the present invention.

[0036] Icons: 100 - outer casing; 200 - water distributor; 300 - drive motor; 400 - upper connector; 500 - lower connector. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0039] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0040] In practical applications, it has been found that using flow meters to measure the water injection volume of each layer is prone to damage under the influence of the high temperature and high pressure environment downhole, as well as poor data accuracy and severe data drift, which seriously restricts the promotion and use of layered water injection technology.

[0041] In view of this, the present invention provides a method for calculating the flow rate of a stratified water injection well, comprising the following steps:

[0042] Single-layer water injection: Other water injection sections are closed, and water is injected only into the i-th layer. The wellhead injection flow rate is the actual injection flow rate Q for that layer. i ;

[0043] Coefficient Calculation: Calculate the flow coefficient D for this layer based on the flow formula. i The flow formula is

[0044] Among them, K i ΔP is the faucet opening value. i =P 1i -P 2i P 1i For the pressure in front of the mouth, P 2i ρ is the pressure behind the nozzle, and ρ is the density of the injected water.

[0045] Flow rate calculation: During water injection, the actual water injection flow rate Q of each layer is calculated in real time according to the flow rate formula. i ;

[0046] Flow control: Set the injection volume Q for each layer pi When the actual water injection flow rate Q i With the amount of injection Q pi When the difference exceeds the set value, adjust the faucet opening to change the faucet opening value K. i Until the actual water injection flow rate Q i With the amount of injection Q pi The difference is not greater than the set value.

[0047] The flow rate calculation method for stratified water injection wells provided by this invention only requires conducting a single-layer water injection test beforehand to obtain the flow rate coefficient D of that layer when performing simultaneous multi-layer water injection. i Then, multiple layers of water can be injected simultaneously. During water injection, there is no need to install a flow meter downhole; only pressure sensors need to be installed before and after the nozzle to obtain the pressure P before the nozzle. 1i And mouth pressure P 2i The actual water injection flow rate Q of each layer can be calculated in real time based on the flow formula. i , and then based on the actual water injection flow rate Q i With the amount of injection Q pi The difference is used to determine whether the nozzle opening needs adjustment. Since there's no need to use a flow meter downhole, problems such as flow meter damage and inaccurate flow data measurement are avoided. Simultaneously, the flow coefficient D... i The use of this method simplifies the flow formula, reduces the complexity of the flow calculation model, and improves the model's practicality and computational efficiency. Because it uses fewer parameters, it is more suitable for practical engineering applications, especially when dealing with complex geological conditions and dynamically changing nozzle openings. It provides a more intuitive and easy-to-implement solution, avoiding computational complexity, dependence on experimental data, and inaccurate calculation results caused by a large number of parameters.

[0048] Specifically, in the flow control step, the actual water injection flow rate Q i With the amount of injection Q pi The difference does not exceed the injection volume Q pi 10% of

[0049] |Q i -Q pi |≤10%×Q pi .

[0050] When the actual water injection flow rate Q i Exceeding the dosage Q pi After reducing the flow rate by 10%, decrease the nozzle opening; when the actual water injection flow rate Q... i Below the dosage Q pi After reducing it by 10%, increase the water tap opening.

[0051] The flow rate calculation method for stratified water injection wells provided in this embodiment requires pressure sensors to be installed before and after the water nozzle, respectively, to measure the pressure P before the nozzle. 1i And mouth pressure P 2i .

[0052] The derivation process of the flow rate formula provided in this embodiment is as follows:

[0053] a) Based on the continuity equation and Bernoulli's equation, construct the actual injection flow rate Q of the i-th layer. i _ Water tap opening value K i Pre-mouth pressure P1i And mouth pressure P 2i The mathematical model between them. Assuming the fluid is incompressible and the flow is in steady state, and neglecting frictional losses, Bernoulli's equation can be simplified to:

[0054]

[0055] Where ρ is the fluid density; v 1i Let v be the flow velocity in front of the mouth of the i-th layer. 2i The velocity after the i-th layer of the nozzle is g; g is the acceleration due to gravity; h 1i h is the height of the mouth of the i-th layer. 2i Let be the height of the mouth of the i-th layer.

[0056] Due to h 1i ≈h 2i Therefore, the influence of gravitational potential energy can be ignored; at the same time, in practical applications, especially when the faucet has a significant throttling effect on the fluid, the flow velocity in front of the faucet is much smaller than the flow velocity behind the faucet, that is, during the water injection process, v 2i >>v 1i The two differ significantly in magnitude, reaching 10. 7 , such as v 2i Up to 10,000, v 1i Therefore, v is only 0.001. 1i ≈0.

[0057] In summary, Bernoulli's equation can be further simplified to:

[0058]

[0059] It can be obtained

[0060] Where: ΔP i =P 1i -P 2i .

[0061] b) Due to the faucet opening value K i The flow rate can be influenced by a flow coefficient A. i To represent the relationship between the faucet opening value and the flow velocity:

[0062]

[0063] It should be noted that v obtained by formula (1) 2i There is a certain deviation from the actual flow velocity, so a flow coefficient A is introduced here. i Water tap opening value K i For v 2i Corrections are made to improve the accuracy of the results; these corrections are derived through experimental verification and work experience.

[0064] c) The actual injection flow rate Q is given by the continuity equation Q = Bv. i With flow velocity v 2i The relationship between the flow cross-sectional area B of the faucet and the water flow area:

[0065] Q i =B·v 2i (3)

[0066] Wherein, the flow cross-sectional area B of the faucet is the faucet opening value K. i For regulation and control of changes, a linear coefficient C can be introduced. i Constructing linear equations:

[0067] B = C i ·K i (4)

[0068] Combining equations (1), (2), (3), and (4) above, the flow rate Q can be obtained. i With water tap opening K i and pressure difference ΔP i Relationship:

[0069]

[0070] For the same layer, the flow coefficient A i and linear coefficient C i These are all fixed constants and can be combined into a flow coefficient D. i =A i C i Therefore, equation (5) above can be simplified to:

[0071]

[0072] Thus, the flow rate formula provided in this embodiment is obtained. Where, D i The flow rate can be measured using a single-layer injection method, i.e., closing other injection layers and injecting water only into the i-th layer. In this case, the wellhead pressure P and the wellhead injection flow rate Q are the actual injection pressure and actual injection flow rate Q of the i-th layer. i Then the actual water injection flow rate Q i Pre-mouth pressure P 1i And mouth pressure P 2i Substituting into the flow formula, we can obtain the flow coefficient D of the i-th layer. i Following this method, the flow coefficient D of each injection layer is obtained. i Then, multi-layer water injection can be carried out, based on the flow formula and the real-time pressure P at the nozzle of each injection layer. 1i And mouth pressure P 2i The actual water injection flow rate Q of each layer was calculated. i ; and then the actual water injection flow rate Q iWith the amount of injection Q pi This allows for comparison to facilitate real-time adjustment of the faucet opening value.

[0073] In this embodiment, the faucet opening is measured as a percentage, i.e., 0-100%, with each opening value K. i This data corresponds to a certain area and can be obtained when manufacturing the faucet.

[0074] Based on the flow calculation method for stratified water injection wells provided in this embodiment, a water injection device for stratified water injection wells is proposed. Employing the aforementioned flow calculation method, the device includes a housing 100, a water distributor 200, a drive motor 300, an upper connector 400, a lower connector 500, transmission components, a pressure sensor, a signal transmission unit, and a ground control unit. Figure 1 As shown.

[0075] Specifically, the upper connector 400 and the lower connector 500 are connected to the two ends of the housing 100 respectively for pipe string connection. The upper connector 400 connects the wellhead equipment and the downhole device, ensuring the entire device can be securely installed and reliably connected to surface equipment; the lower connector 500 connects the downhole pipeline system, ensuring smooth fluid flow through the device. The housing 100 protects the internal precision components from damage caused by external pressure and corrosive fluids.

[0076] The water distributor 200 and the drive motor 300 are mounted on the housing 100. A transmission component connects the drive motor 300 and the water distributor 200. The drive motor 300 adjusts the faucet opening via the transmission component. Two pressure sensors are used to measure the pressure P at the faucet. 1i And mouth pressure P 2i The signal transmission unit is used for two-way communication between the surface and the well. It is responsible for transmitting commands from the surface control unit to the well and feeding back the well's operating status and measurement data to the surface. The surface control unit receives signals from the pressure sensor through the signal transmission unit and sends flow regulation signals to the water distributor 200 to control the nozzle opening.

[0077] The water distributor 200 includes a control calculation module, which receives instructions from the ground control unit and controls the drive motor 300 to adjust the water nozzle opening.

[0078] In addition, the water injection device of the stratified water injection well also includes a centralizer and a guide. The centralizer is installed on the outer shell 100 to ensure the stability of the device downhole and prevent it from shifting position in a high-pressure fluid environment. The guide is used to guide the movement of the transmission components to ensure that the transmission motor 300 can accurately control the opening and closing of the water nozzle, thereby accurately controlling the amount of fluid injected and ensuring that the water injection flow rate of each layer can meet the geological injection requirements.

[0079] In actual operation, the ground control unit sends flow regulation signals to the downhole water distributor 200 via a signal transmission unit. Upon receiving the signal, the water distributor 200 adjusts the opening and closing of the nozzles via the drive motor 300, thereby controlling the water injection flow rate. The upper connector 400 and lower connector 500 ensure reliable connection between the device and the wellhead and downhole piping system, allowing fluid to flow smoothly into and out of the device. The centralizer and housing 100 ensure the stability and safety of the device in the harsh downhole environment, preventing damage from external pressure and corrosion. The guide ensures precise movement of the transmission components, preventing control failure due to errors. Through the cooperation of these components, precise control and regulation of the water injection flow rate at each layer is achieved, ensuring that the water injection system can meet the needs of different formations, improving water injection efficiency and geological adaptability.

[0080] Throughout the water injection process, the surface control unit continuously collects data and performs real-time monitoring and analysis. The signal transmission unit is not only responsible for transmitting surface commands, but also provides real-time feedback on the operating status and measurement data of downhole equipment, providing real-time basis for surface control. This enables precise control and calculation of the flow rate in the stratified water injection well sections, improving the oilfield's production efficiency and economic benefits, while reducing operating costs and maintenance workload.

[0081] The flow rate calculation method for stratified water injection wells provided in this embodiment avoids problems such as easy damage to flow meters in the high-temperature and high-pressure environment downhole, poor data accuracy, and severe data drift by employing pressure measurement. Specifically, it controls the nozzle opening value through an intelligent water distributor and measures the pressure difference before and after the water nozzle, using a mathematical model to calculate the water injection flow rate of each layer downhole. This method not only improves the accuracy of flow data and avoids the problem of flow meter damage in high-temperature and high-pressure environments, but also simplifies the equipment structure and reduces maintenance and operating costs. By realizing automatic adjustment of nozzle opening and real-time monitoring of flow, it significantly improves operational efficiency and control accuracy, enabling the water injection system to meet the geological injection volume requirements, achieving the goal of intelligent stratified water injection, and improving economic benefits and operational efficiency.

[0082] The flow rate formula provided in this embodiment employs a mathematical model based on the continuity equation and Bernoulli's equation. This model simplifies Bernoulli's equation by assuming the fluid is incompressible, the flow is in a steady state, and frictional losses are neglected. The simplified flow rate is more suitable for practical engineering applications, especially when dealing with complex geological conditions and dynamically changing nozzle openings, providing a more intuitive and easy-to-implement solution. This formula reduces the number of required input parameters, avoiding instability and data processing difficulties caused by multiple parameter inputs, and reducing the model's dependence on specific experimental data, making the model more universal and flexible. In actual operation, it can effectively improve the automation level and operating efficiency of the water injection system, avoiding delays caused by processing large amounts of data.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the flow rate of a stratified water injection well, characterized in that, Includes the following steps: Single-layer water injection: Other water injection sections are closed, and water is injected only into the i-th layer. The wellhead injection flow rate is the actual injection flow rate Q for that layer. i ; Coefficient Calculation: Calculate the flow coefficient D for this layer based on the flow formula. i The flow formula is Among them, K i ΔP is the faucet opening value. i =P 1i -P 2i P 1i For the pressure in front of the mouth, P 2i ρ is the pressure behind the nozzle, and ρ is the density of the injected water. Flow rate calculation: During water injection, the actual water injection flow rate Q of each layer is calculated in real time according to the flow rate formula. i ; Flow control: Set the injection volume Q for each layer pi When the actual water injection flow rate Q i With the amount of injection Q pi When the difference exceeds the set value, adjust the faucet opening to change the faucet opening value K. i Until the actual water injection flow rate Q i With the amount of injection Q pi The difference is not greater than the set value.

2. The method for calculating the flow rate of a stratified water injection well according to claim 1, characterized in that, In the flow control step, the actual water injection flow rate Q i With the amount of injection Q pi The difference does not exceed the injection volume Q pi 10% of |Q i -Q pi |≤10%×Q pi 。 3. The method for calculating the flow rate of a stratified water injection well according to claim 2, characterized in that, When the actual water injection flow rate Q i Exceeding the dosage Q pi After reducing the water flow by 10%, decrease the water tap opening. When the actual water injection flow rate Q i Below the dosage Q pi After reducing it by 10%, increase the water tap opening.

4. The method for calculating the flow rate of a stratified water injection well according to claim 1, characterized in that, Pressure sensors are installed at both the front and rear of the faucet to measure the pressure P at the front of the faucet. 1i And mouth pressure P 2i .

5. A water injection device for a stratified water injection well, employing the flow rate calculation method for a stratified water injection well as described in any one of claims 1-4, characterized in that, It includes a housing (100), a water distributor (200), a drive motor (300), and a pressure sensor; The water distributor (200) and the drive motor (300) are installed on the housing (100), and the drive motor (300) is used to adjust the opening of the water nozzle of the water distributor (200); The two pressure sensors are used to measure the pressure P in front of the mouth. 1i And mouth pressure P 2i .

6. The water injection device for a stratified water injection well according to claim 5, characterized in that, It also includes a signal transmission unit; The signal transmission unit is used for two-way communication between the surface and underground.

7. The water injection device for a stratified water injection well according to claim 6, characterized in that, It also includes a ground control unit; The ground control unit receives the signal from the pressure sensor through the signal transmission unit and sends a flow regulation signal to the water distributor (200) to control the opening of the water tap.

8. The water injection device for a stratified water injection well according to claim 7, characterized in that, It also includes an upper connector (400) and a lower connector (500), which are respectively connected to the two ends of the housing (100) for pipe string connection.

9. The water injection device for a stratified water injection well according to claim 8, characterized in that, The water distributor (200) includes a control calculation module, which receives instructions from the ground control unit and controls the drive motor (300) to adjust the water nozzle opening.

10. The water injection device for a stratified water injection well according to claim 9, characterized in that, It also includes a transmission component for connecting the drive motor (300) and the water distributor (200), and the drive motor (300) adjusts the opening of the water nozzle through the transmission component.

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