Natural gas well injection pressurization process optimization design method and application thereof

Abstract

The invention discloses a natural gas well injection pressurization process optimization design method and application thereof. The optimization design method comprises the steps that evaluation indexes are determined; establishing an energy conservation equation; establishing a momentum conservation equation; introducing an empirical coefficient and a working equation of the nozzle; establishing a jet drainage tool characteristic equation and an optimal section ratio calculation formula; and calculating the axial size of the jet drainage tool. According to different working conditions, parameters such as the optimal nozzle throat area ratio of the corresponding mixing chamber, the injection coefficient under the optimal section ratio condition, the throat diameter of the mixing chamber and the areas of the nozzle and the throat are calculated, variable working condition performance analysis is carried out on different natural gas ejectors, and corresponding charts are made to guide field production. The optimization design time cost is greatly saved, and the optimization design efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas exploitation, and in particular relates to a natural gas well injection pressurization process optimization design method and application thereof. Background Art

[0002] At present, most of my country's gas fields have been developed to the middle and late stages, and the number of low-pressure wells and intermittent wells has continued to increase, with low wellhead pressure and close to shutdown. At present, the common treatment methods for low-pressure gas wells are well shut-in, trial production and pressurized production, and all three methods have certain disadvantages. The first method will cause the gas wells to be idle, affecting the increase in production capacity; the second method will cause a large amount of natural gas to be burned in vain during production, resulting in energy waste and environmental pollution; the third method is to use compressors to increase the pressure energy of the gas, so that it can enter the centralized production system to solve the problem of low-pressure gas well collection and transportation, but this method has problems such as high energy consumption and high maintenance costs during the implementation of the method. However, due to the heterogeneity of the formation, after years of development, there are still some high-pressure and high-yield wells in the same area that still maintain a relatively high pressure. High-pressure natural gas wells contain rich pressure energy and have a high utilization value, but in actual production, most high-pressure gas wells are exploited by throttling and pressure reduction, resulting in most of the energy waste, which does not meet the requirements of building energy-saving oil fields currently advocated. Therefore, how to utilize the pressure energy of high-pressure gas wells to solve the gathering and transportation problems of low-pressure gas wells and increase the production and production cycle of low-pressure gas wells is a topic of great practical significance.

[0003] The principle of natural gas injection and drainage technology is that high-pressure natural gas is throttled through the nozzle, forming a low-pressure area in the mixing chamber that is lower than the inlet pressure of the low-pressure gas. The low-pressure natural gas is sucked into the mixing section under the action of the pressure difference and mixed with the high-speed flowing natural gas to form a mixed gas flow with a certain speed. After the pressure is increased in the expansion section, it is transmitted to the outside. This technology can make full use of the pressure energy of high-pressure gas wells and explore a new way for pressurized exploitation of low-pressure gas wells. Among them, the natural gas ejector is a mechanical device that uses the surplus pressure of the high-pressure gas well to eject and pressurize the low-pressure natural gas. Since this device can increase the pressure of the low-pressure natural gas without consuming mechanical energy, it has the characteristics of energy saving. In addition, the natural gas ejector has a simple structure and is easy to operate. It can achieve the purpose of continuous use of low-pressure natural gas after pressurization. It has been applied to a certain extent on the spot in recent years. Then, in the related research on the optimization design method of the ejection boosting process, the computational fluid dynamics method is mostly used. Due to the interactive influence of the working condition parameters and structural parameters on the ejection coefficient, when carrying out the optimization design, a large number of physical models need to be established according to the changes in the structural parameters, which is a huge workload; secondly, the internal design of the ejection boosting tool is difficult to converge in the numerical calculation process from the compressible flow calculation, and the settlement result is unstable. The optimization design of the ejection boosting process based on the computational fluid dynamics method requires a certain theoretical foundation of fluid mechanics and experience in the use of computational fluid dynamics related software, and the optimization design process takes a long time. For on-site engineers, it is difficult to apply, and the optimization cycle is too long, and the practicality is poor. Therefore, it is very necessary to quickly calculate the optimal structural parameters of the ejection boosting device under different working conditions, perform variable working condition performance analysis on different injection devices, and make corresponding plates to guide on-site production. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing method using computational fluid dynamics has huge workload, poor stability of settlement results and poor practicality.

[0005] The present invention provides a method for optimizing the design of a natural gas well ejector pressurization process, based on a natural gas ejector, comprising the following steps:

[0006] S1. Taking the ejection coefficient and expansion ratio as evaluation indicators;

[0007] S2. Establish the energy conservation equation

[0008] H p +uH H =(1+u)H c

[0009] In the formula, H P - Enthalpy of the working fluid before the injection tool, kJ / kg; H H - Enthalpy of the ejected fluid before the injection tool, kJ / kg; H C- Enthalpy of the mixed fluid after the injection tool, kJ / kg;

[0010] S3. Establish the momentum conservation equation

[0011] S4. Introducing the working equation of the nozzle

[0012]

[0013] In the formula, -Enter the empirical coefficient, P P -Pressure of the working fluid before the injection tool, MPa; P H -Pressure of the ejected fluid before the injection tool, MPa; A 1 —Nozzle outlet cross section; V p — working fluid velocity before throttling;

[0014] S5. Characteristic equation of jet drainage tool and calculation formula of optimal cross-sectional ratio

[0015] The characteristic equation of the jet drainage tool is as follows:

[0016]

[0017] The calculation formula for the optimal cross-section alignment is as follows:

[0018]

[0019] S6. Obtain the axial dimensions of the mixing chamber of the jet drainage tool

[0020] The axial length of the mixing chamber is 3 to 7 times that of the section where its diameter does not change;

[0021] S7. Obtain the axial dimensions of the diffusion chamber of the jet drainage tool

[0022] The calculation formula of the axial length of the diffusion chamber of the jet drainage tool is as follows:

[0023]

[0024] In the formula, I s -Axial length of the diffusion chamber, m; d s -Diameter of the outlet of the diffusion chamber, m; d 3 -Diameter of the mixing chamber where the diameter does not change, m.

[0025] As a possible design, the calculation formula of the induced coefficient in step S1 is as follows:

[0026]

[0027] Where M H —Mass flow rate of the ejected fluid, kg / s; M P—Mass flow rate of working fluid, kg / s.

[0028] As a possible design, the expansion ratio in step S1 is the ratio of the pressure difference between the working fluid and the ejection fluid to the pressure difference between the mixed fluid and the ejection fluid.

[0029] As a possible design, the momentum conservation equation in step S3 is as follows:

[0030]

[0031] In the formula, -mixing chamber throat velocity coefficient; V P2 - Working fluid velocity at throat inlet, m / s; V H2 - velocity of the ejected fluid at the throat entrance, m / s; V 3 - Flow rate of mixed fluid at throat outlet, m / s; p p2 - Static pressure of working fluid at throat inlet, Pa, P P2 =P H ;P H2 - static pressure of the ejected fluid at the throat entrance, Pa; P 3 - Static pressure of mixed fluid at throat outlet, Pa; A P2 - Flow cross-sectional area occupied by working fluid at the entrance of the throat mixing chamber m 2 ; A H2 - The cross-sectional area of ​​the fluid ejected from the throat mixing chamber entrance, m 2 ; A 3 -Throat cross-sectional area, m 2 .

[0032] As a possible design, the nozzle working equation is substituted into the momentum conservation equation to obtain the characteristic equation of the jet drainage tool:

[0033]

[0034] As a possible design, assume that the throat area A 3 The cross-sectional ratio to the nozzle outlet cross-sectional ratio A is A', and the quadratic equation of the ejection coefficient μ and the cross-sectional ratio A can be constructed. The ejection coefficient calculation formula is:

[0035]

[0036] As a possible design, when the ejection coefficient μ≤0.5,

[0037]

[0038] In the formula, l f1 is the length of the free beam, m; d 1is the nozzle diameter, a is an experimental constant, ranging from 0.07 to 0.09;

[0039]

[0040] Where, d 4 is the diameter of the free stream, m;

[0041] When the ejection coefficient μ>0.5,

[0042]

[0043] d 4 =1.55d 1 (1+μ).

[0044] As a possible design, the mixing chamber of the spray tool involved is conical with an angle of 45°.

[0045] As a possible design, the diffusion chamber of the injection tool involved is conical with an angle of 8° to 10°.

[0046] Beneficial effects of the present invention:

[0047] Based on the existing natural gas ejectors, the present invention can calculate the corresponding parameters such as the optimal nozzle throat area ratio of the mixing chamber, the ejection coefficient under the optimal cross-sectional ratio condition, the mixing chamber throat diameter and the area of ​​the nozzle and the throat according to different working conditions, conduct variable working condition performance analysis on different natural gas ejectors, and make corresponding drawings to guide on-site production, which greatly saves the time cost of optimization design and improves the efficiency of optimization design. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0049] Figure 1 is a schematic diagram of an existing natural gas ejector;

[0050] Figure 2 It is a working principle diagram of the jet drainage tool of the existing natural gas ejector;

[0051] Figure 3 Schematic diagram of a free stream beam.

[0052] Among them, the reference numerals in the figure are:

[0053] 1-Suction chamber; 2-Obliteration layer; 3-Mixing chamber; 4-Diffusion chamber. DETAILED DESCRIPTION

[0054] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0055] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0056] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0057] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0058] The existing computational fluid dynamics methods have huge workload, poor stability of settlement results and poor practicality.

[0059] The structure of the natural gas ejector used in the present invention is as follows: Figure 1 As shown, it comprises a suction chamber, a mixing chamber and a diffusion chamber which are connected in sequence. When in use, the axial opening of the suction chamber receives the working fluid from the main nozzle, the radial opening of the suction chamber receives the ejection fluid, and the outlet end of the diffusion chamber is used for the outflow of the mixed fluid.

[0060] Figure 2 Shows Figure 1 The working principle of the natural gas ejector is shown.

[0061] The invention discloses a method for optimizing the design of a natural gas well injection pressurization process, which uses constant pressure mixing theory or constant area mixing theory as a guide, applies a gas dynamics method, uses natural gas as a working fluid, and designs and determines process optimization, and has the characteristics of being fast and convenient.

[0062] A method for optimizing the design of a natural gas well injection pressurization process comprises the following steps:

[0063] Step 1: Determine the evaluation index. In the design of jet drainage tools, an important technical parameter, the ejection coefficient, must be introduced first. It is defined as the ratio of the mass flow rate of the ejected fluid to the mass flow rate of the working fluid during the operation of the jet tool.

[0064] The ejection coefficient is the most important indicator for evaluating the working effect of jet drainage tools.

[0065]

[0066] Where M H —Mass flow rate of the ejected fluid, kg / s; M P —Mass flow rate of working fluid, kg / s.

[0067] In addition, another very important technical parameter is introduced, namely the expansion ratio: it is defined as the ratio of the pressure difference between the working fluid and the ejection fluid to the pressure difference between the mixed fluid and the ejection fluid. The expansion ratio is an important indicator reflecting the pressure-increasing ability of the jet drainage tool.

[0068] Step 2: Establish the energy equation. Take the gas in the tool as the research object and list the energy conservation equation:

[0069] H P +uH H =(1+u)H c (2)

[0070] In the formula, H P —Enthalpy of the working fluid before the injection tool, kJ / kg; H H —Enthalpy of the ejected fluid before the injection tool, kJ / kg; H C —Enthalpy of the mixed fluid after the injection tool, kJ / kg.

[0071] Step 3: Establish the momentum equation. Take the gas in the throat section of the mixing chamber as the research object and list the momentum conservation equation:

[0072]

[0073] In the formula, —mixing chamber throat velocity coefficient; V P2 —Flow rate of working fluid at throat inlet, m / s; V H2 — velocity of ejected fluid at throat entrance, m / s; V 3 Mixed fluid velocity at the throat outlet, m / s; p p2 Static pressure of working fluid at the throat entrance, Pa; P H2—static pressure of ejected fluid at throat entrance, Pa; P 3 Static pressure of mixed fluid at the throat outlet, Pa; A P2 —Flow cross-sectional area occupied by working fluid at the entrance of the throat mixing chamber m 2 ; A H2 —The flow cross-sectional area occupied by the jet fluid at the entrance of the throat mixing chamber, m 2 ; A 3 —Throat cross-sectional area, m 2 ;

[0074] As shown in the above constant pressure mixing theory assumption:

[0075] P P2 =P H (4)

[0076] Step 4: Introduce the empirical coefficient and the nozzle working equation. Introduce the nozzle working equation:

[0077]

[0078]

[0079]

[0080] Step 5: Transform to obtain the characteristic equation of the jet drainage tool and the calculation formula for the optimal cross-sectional ratio:

[0081] Substituting the nozzle working equation into the momentum conservation equation, the characteristic equation of the jet drainage tool can be obtained:

[0082]

[0083] The characteristic equation of the jet drainage tool is obtained by substitution:

[0084]

[0085] Assume throat area A 3 The cross-sectional ratio to the nozzle outlet cross-sectional ratio A is A', and a quadratic equation of the ejection coefficient μ and the cross-sectional ratio A can be constructed. Solving the equation, the ejection coefficient calculation formula can be approximately expressed as:

[0086]

[0087] When the ejection coefficient of the injection tool is the largest, the ratio of the throat cross-sectional area of ​​the mixing chamber to the nozzle outlet cross-sectional area is defined as the optimal cross-sectional ratio of the injection injection tool. Differentiate the ejection coefficient calculation formula, when du / dA=0, the ejection coefficient reaches the maximum value, and the calculation formula for the optimal cross-sectional ratio of the tool is:

[0088]

[0089] In the process optimization study of this paper, the nozzle size has been set in advance due to the limitations of the experimental facilities. Therefore, the cross-sectional area of ​​the throat of the cylindrical mixing chamber can be calculated by the optimal cross-sectional ratio.

[0090] Step 6: Calculate the axial dimensions of the jet drainage tool:

[0091] (1) Calculation of the distance between the nozzle and the mixing chamber throat

[0092] When the working fluid enters the suction chamber after being throttled by the nozzle, a part of the ejection fluid is entrained due to the turbulent mixing of the medium. At this time, the mixed fluid flow beam expands and the axial velocity decreases. We call the section from the nozzle outlet section to the inlet section of the mixing chamber of the injection tool the free flow beam of the mixed fluid. The flow beam section when the cross section of the central area where the velocity remains constant becomes zero is called the transition section. Sokolov divides the flow beam into two sections: the initial section and the basic section. The section of the flow beam between the nozzle outlet section and the transition section of the flow beam is called the initial section, and the section after the transition section is called the basic section. When designing the injection and drainage tool, it must be ensured that the cross section of the free flow beam is equal to or slightly smaller than the value of the throat inlet section of the mixing chamber. Therefore, the length In of the free flow beam and the diameter d4 of the free flow velocity section at this length must be calculated.

[0093] The length of the free stream In and the diameter d4 of the free stream at this distance are usually obtained by empirical formula: When the ejection coefficient μ≤0.5, that is, when the free stream does not exceed the starting section:

[0094]

[0095]

[0096] When the ejection coefficient μ>0.5, that is, when the free stream contains the starting section and the basic section:

[0097]

[0098] d 4 =1.55d 1 (1+μ) (15)

[0099] In the above empirical formula, a is an experimental constant. For elastic fluid media, the value range of a is generally recommended to be 0.07 to 0.09. When the ejection coefficient is small, it is recommended to use a smaller experimental constant value, and when the ejection coefficient is large, a larger value is selected.

[0100] The calculated length of the free stream is the distance between the nozzle outlet section and the cylindrical throat inlet section. At this time, the final cross-sectional diameter of the mixed fluid free stream is equal to the throat diameter. At the same time, if the nozzle throat distance is slightly smaller than the length of the free stream, it will not seriously affect the operation of the jet guide tool. However, if the nozzle position is moved to a position larger than the free stream, the final cross-sectional area of ​​the free stream will increase, which may cause the cross-sectional diameter of the free stream at the throat inlet to be larger than the diameter of the mixing chamber throat. At this time, the fluid brought in by the free stream is larger than the fluid flow allowed by the throat, so a part of the fluid will flow back from the mixing chamber to the suction chamber, causing backflow at the throat inlet section and additional energy loss associated with the backflow.

[0101] Therefore, in the optimization design, in order to study the influence of nozzle throat distance on the jet drainage tool in subsequent experiments, the nozzle component was designed as a structure that can be moved axially through threads during tool design, so as to change the axial position of the nozzle and thus change the nozzle throat distance.

[0102] (2) Calculation of axial dimensions of mixing chamber

[0103] In the jet drainage tool, the velocity of the working fluid ejected from the nozzle is parallel to the velocity direction of the entrained entrained fluid, which can be regarded as a parallel jet in the forward direction. The mixed gas exchanges energy in the cylindrical throat of the mixing chamber, and the temperature field and velocity field are constantly uniform in this process. At the same time, the axial static pressure of the mixed gas is gradually restored. When the mixed fluid moves evenly to a certain section of the throat, the velocity field and temperature field tend to be stable, and at this time, the axial static pressure is also restored. After this section of the fluid, the velocity field of the mixed fluid will theoretically no longer change, and the fluid will move in a stable turbulent state. However, due to the influence of wall friction resistance, the energy of the mixed fluid is lost, and the static pressure will gradually decrease with the increase of the throat distance. Therefore, the throat section when the axial mixed gas static pressure returns to the maximum value is the optimal terminal section of the mixing chamber throat, and the distance between this section and the throat entrance is the optimal length of the mixing chamber throat. Therefore, when designing the throat length of the mixing chamber of the jet drainage tool, it should be ensured that the throat length is slightly larger than the optimal length.

[0104] According to experimental data, the throat length L of the cylindrical mixing chamber of the jet drainage tool m It is usually taken as 3 to 7 times the diameter of the mixing chamber throat d 3 ,Right now

[0105] I m =(3~7)d 3 (16)

[0106] For the inlet section of the mixing chamber, since the conical inlet section has a relatively large velocity coefficient, the injection tool can obtain a higher efficiency. According to the current general design ideas, the inlet of the mixing chamber adopts a cone shape with an angle of 45°.

[0107] For the diffuser at the rear of the mixing chamber throat, the deceleration and expansion of the subsonic mixed fluid must be carried out in the gradually expanding diffuser. The cone angle is usually set to 8°~10°. When the diffuser outlet diameter ds is given, the axial length Is of the diffuser is obtained according to the empirical formula:

[0108]

[0109] The units of each parameter in the above formulas are all international standard systems.

[0110] The following example illustrates

[0111] Combined with the actual conditions of the experimental site and facilities, such as specifications and gas supply pressure, the structural parameters of the jet drainage trial tool used to verify the numerical simulation are designed and calculated. The original design conditions of the tool are shown in the table

[0112] Table 1 Tool design conditions

[0113]

[0114] According to the concept of expansion ratio, the lower the expansion ratio, the better the tool boosting effect. However, in actual situations, the designed tool often cannot meet the initial design boosting requirements. Therefore, in the design process, the more conservative condition of an expansion ratio of 5 is first selected for calculation, and simulation and experiment are used to verify whether the tool can achieve this indicator. If successful, the expansion ratio is appropriately reduced for calculation according to the previous design steps to ensure the success rate of the design.

[0115] According to the conditions given in Table 1, the structural parameters of the jet drainage tool are calculated:

[0116] (1) Optimal nozzle throat section ratio A' best :

[0117]

[0118] (2) Limit ejection ratio μ under the optimal cross-sectional ratio condition:

[0119]

[0120] (3) Cylindrical mixing chamber throat diameter d 3 :

[0121]

[0122] (4) Distance between nozzle and throat l f:

[0123]

[0124] (5) Free stream final cross-sectional diameter d 4 :

[0125]

[0126] (6) Cylindrical mixing chamber throat length 1m:

[0127] 1 m =(3~7)d 3 =(3~7)×4.2≈13~30mm

[0128] (7) Diffuser chamber length l s :

[0129]

[0130] In the above calculation, since the diameter of the mixing chamber throat must be larger than the diameter of the free stream final section, the optimal throat is determined to be 4.3 mm.

[0131] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for optimizing the design of a natural gas well ejector pressurization process, based on a natural gas ejector. Features: The following steps are involved: S1. Taking the ejection coefficient and expansion ratio as evaluation indicators; S2. Establish the energy conservation equation H P +uH H =(1+u)H c In the formula, H P - Enthalpy of the working fluid before the injection tool, kJ / kg; H H - Enthalpy of the ejected fluid before the injection tool, kJ / kg; H C - Enthalpy of the mixed fluid after the injection tool, kJ / kg; S3. Establish the momentum conservation equation S4. Introducing the working equation of the nozzle In the formula, -Enter the empirical coefficient, P P -Pressure of the working fluid before the injection tool, MPa; P H -Pressure of the ejected fluid before the injection tool, MPa; A 1 —Nozzle outlet cross section; V p — working fluid velocity before throttling; S5. Characteristic equation of jet drainage tool and calculation formula of optimal cross-sectional ratio The characteristic equation of the jet drainage tool is as follows: —The velocity coefficient of the mixing chamber throat is 0.975; The empirical coefficients are 0.95, 0.9, and 0.93 respectively; A 3 —Throat cross-sectional area, m 2 ; A 1 —Nozzle outlet cross section; P p —Working fluid pressure after throttling; P H —initial working fluid pressure; V H —initial fluid velocity; V c —Fluid velocity in the diffusion section; P 3 —Working fluid pressure at the inlet of the diffusion chamber; P c —Working fluid pressure at the outlet of the diffusion section; V p — working fluid velocity before throttling; The calculation formula for the optimal cross-section alignment is as follows: S6. Obtain the axial dimensions of the mixing chamber of the jet drainage tool The axial length of the mixing chamber is 3 to 7 times that of the section where its diameter does not change; S7. Obtain the axial dimensions of the diffusion chamber of the jet drainage tool The calculation formula of the axial length of the diffusion chamber of the jet drainage tool is as follows: In the formula, I s -Axial length of the diffusion chamber, m; d s -Diameter of the outlet of the diffusion chamber, m; d 3 -Diameter of the mixing chamber where the diameter does not change, m.

2. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: The calculation formula of the ejection coefficient in step S1 is as follows: Where M H —Mass flow rate of the ejected fluid, kg / s; M P —Mass flow rate of working fluid, kg / s.

3. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: In step S1, the expansion ratio is the ratio of the pressure difference between the working fluid and the ejection fluid to the pressure difference between the mixed fluid and the ejection fluid.

4. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: The momentum conservation equation in step S3 is as follows: In the formula, -mixing chamber throat velocity coefficient; V P2 - Working fluid velocity at throat inlet, m / s; V H2 - velocity of the ejected fluid at the throat entrance, m / s; V 3 - Flow rate of mixed fluid at throat outlet, m / s; p p2 - Static pressure of working fluid at throat inlet, Pa, P P2 =P H ;P H2 - static pressure of the ejected fluid at the throat entrance, Pa; P 3 - Static pressure of mixed fluid at throat outlet, Pa; A P2 - Flow cross-sectional area occupied by working fluid at the entrance of the throat mixing chamber m 2 ; A H2 - The cross-sectional area of ​​the fluid ejected from the throat mixing chamber entrance, m 2 ; A 3 -Throat cross-sectional area, m 2 .

5. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: Substituting the nozzle working equation into the momentum conservation equation, the characteristic equation of the jet drainage tool can be obtained:

6. The method for optimizing the design of the natural gas well injection pressurization process according to claim 5, Features: Assume throat area A 3 The cross-sectional ratio to the nozzle outlet cross-sectional ratio A is A', and the quadratic equation of the ejection coefficient μ and the cross-sectional ratio A can be constructed. The ejection coefficient calculation formula is:

7. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: When the ejection coefficient μ≤0.5, In the formula, l f1 is the length of the free beam, m; d 1 is the nozzle diameter, a is an experimental constant, ranging from 0.07 to 0.09; Where, d 4 is the diameter of the free stream, m; When the ejection coefficient μ>0.5, d 4 =1.55d 1 (1+μ).

8. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1, Features: The mixing chamber of the spray tool in question is conical with an angle of 45°.

9. The method for optimizing the design of the natural gas well injection pressurization process according to claim 1 or 8, Features: The diffusion chamber of the injection tool involved is conical with an angle of 8° to 10°.

10. Application of the method for optimizing the design of the natural gas well injection and pressurization process according to any one of claims 1 to 9 in natural gas production.

Images