Wellhead expansion machine type selection method and system, storage medium and electronic equipment

Abstract

The invention belongs to the technical field of oil and gas development, and provides a wellhead expansion machine type selection method and system, a storage medium and electronic equipment.The method comprises the steps that on the basis of parameters of a gas well wellhead, the volume flow of gas produced by the wellhead is calculated, and the total available isentropic specific enthalpy drop under the two conditions of wellhead pressure and gas collection pressure is obtained; determining the well mouth parallel connection number and the expansion machine configuration mode; the isentropic specific enthalpy drop of the expansion machine is calculated based on the configuration mode of the expansion machine, the impeller diameter of the expansion machine and the rated volume flow; based on the isentropic specific enthalpy drop of the expansion machine and the total available isentropic specific enthalpy drop under the two conditions of wellhead pressure and gas collection pressure, the number of stages of the expansion machine is calculated; based on the rated rotating speed and the isentropic specific enthalpy drop of the expansion machine, the rotating speed and the isentropic specific enthalpy drop of the expansion machine are calculated and adjusted, and the final rotating speed and the final isentropic specific enthalpy drop of the expansion machine are obtained; and calculating the power of the expansion machine. The pressure energy recycling rate is increased, electric heating and use of an anti-freezing agent are reduced, and the cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development technology, and in particular relates to a wellhead expander selection method, system, storage medium and electronic equipment. Background Technology

[0002] The wellhead pressure and gas production of gas wells vary across different oilfield blocks. Many gas wells have wellhead pressures exceeding 50 MPa, with some reaching over 100 MPa. Even with high-pressure gas gathering technology, the average gathering pressure is relatively low, around 12.5 MPa. Gas wellheads generally require multi-stage throttling and pressure reduction processes to meet overall pressure requirements. However, this throttling and pressure reduction process leads to temperature drops, potentially causing pipeline blockage. To prevent freezing caused by throttling and pressure reduction, measures such as electric heating and antifreeze are required. This not only fails to fully utilize residual pressure resources but also increases electricity and chemical consumption, raising the pressure for energy conservation and emission reduction.

[0003] Currently, domestic and international methods for recovering residual pressure at gas wellheads mainly include residual pressure power generation, residual pressure refrigeration, and combined cooling and power (CCHP). However, the key is to first convert pressure energy into mechanical energy. Installing an expander at the wellhead is a prerequisite for utilizing residual pressure in gas wells. Due to the high wellhead pressure, complex media, and significant variations in operating conditions (pressure, production, gas quality, etc.), it is difficult to design a specific expander for each operating condition. Therefore, several typical expanders can only be designed based on the conditions of oilfield wellheads. When encountering different wellhead conditions, the expanders are optimized and combined or connected in parallel at the wellheads to achieve energy conservation and environmental protection as efficiently as possible. Summary of the Invention

[0004] To address the above problems, this invention proposes a wellhead expander selection method, system, storage medium, and electronic equipment.

[0005] The present invention provides a method for selecting a wellhead expander, the method comprising:

[0006] Based on the parameters at the wellhead, the volumetric flow rate of gas produced at the wellhead is calculated, and the total available isentropic enthalpy drop is obtained under two conditions: wellhead pressure and gas gathering pressure.

[0007] Based on the rated volumetric flow rate of the expander and the volumetric flow rate of gas produced at the wellhead, determine the number of wellheads connected in parallel and the expander configuration mode;

[0008] Based on the expander configuration mode, the expander impeller diameter, and the expander rated volumetric flow rate, calculate the isentropic enthalpy drop of the expander;

[0009] The number of expander stages is calculated based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure.

[0010] Based on the expander's rated speed and isentropic enthalpy drop, the expander's speed and isentropic enthalpy drop are calculated and adjusted to obtain the expander's final speed and final isentropic enthalpy drop.

[0011] The power of the expander is calculated based on the final isentropic enthalpy drop of the expander.

[0012] Furthermore,

[0013] The volumetric flow rate of gas produced at the wellhead is calculated using the volumetric flow rate calculation formula, specifically as follows:

[0014] Q ji =mRZT0 / p0 / M,

[0015] In the formula, Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s; m is the wellhead gas mass flow rate, in kg / s; R is the universal gas molar constant, R = 8.3143 kJ / (kmol K); Z is the compressibility factor; T0 is the wellhead temperature, in K; p0 is the wellhead pressure, in Pa; M is the molar mass of gas produced at the wellhead, in kg / kmol.

[0016] Furthermore,

[0017] The number of wellheads connected in parallel and the configuration mode of the expander are determined using wellhead and expander configuration equations, specifically as follows:

[0018]

[0019] In the formula, X represents the number of small-sized expanders; Y represents the number of large-sized expanders; Q I This refers to the rated volumetric flow rate of a small-sized expander, in cubic meters per second (m³). 3 / s;Q II This refers to the rated volumetric flow rate of a large-scale expander, in cubic meters per second (m³). 3 / s; ξ is the number of parallel wellheads; Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s;

[0020] The number of small-sized expanders and the number of large-sized expanders belong to the expander configuration mode.

[0021] Furthermore,

[0022] The isentropic enthalpy drop of the expander is calculated using empirical formulas for expander specifications, specifically as follows:

[0023] h s =1365.7Q 2 / D4 ,

[0024] In the formula, h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s; D is the impeller diameter of the expander, in meters (m).

[0025] Furthermore,

[0026] The number of expander stages is calculated using the expander stage calculation formula, specifically as follows:

[0027] ε=h z / h s ,

[0028] In the formula, ε represents the number of expander stages; h z The total available isentropic enthalpy drop under wellhead and gas gathering pressure conditions, expressed in J / kg; h s This is the isentropic enthalpy drop of the expander, expressed in J / kg.

[0029] Furthermore,

[0030] The rotational speed of the expander is calculated using the rotational speed characteristic formula, specifically as follows:

[0031] n = 1.839h s 0.75 / Q 0.5 ,

[0032] In the formula, n is the rotational speed of the expander, in r / min; h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s.

[0033] Furthermore,

[0034] The power of the expander is calculated using the expander power calculation formula, specifically as follows:

[0035] P T =ηh s q m / 1000,

[0036] In the formula, P T η represents the power of the expander, measured in kW; η is the efficiency of the expander; h s The isentropic enthalpy drop of the expander is expressed in J / kg; q m This represents the mass flow rate of the expander, measured in kg / s.

[0037] This invention also proposes a wellhead expander selection system for implementing the aforementioned wellhead expander selection method, the system comprising:

[0038] The volumetric flow rate calculation and total available isentropic enthalpy drop acquisition module is used to calculate the volumetric flow rate of gas produced at the wellhead based on the parameters at the wellhead, and to obtain the total available isentropic enthalpy drop under two conditions: wellhead pressure and gas gathering pressure.

[0039] The module for determining the number of wellheads connected in parallel and the configuration mode of the expander is used to determine the number of wellheads connected in parallel and the configuration mode of the expander based on the rated volumetric flow rate of the expander and the volumetric flow rate of the gas produced at the wellhead.

[0040] The isentropic enthalpy drop calculation module is used to calculate the isentropic enthalpy drop of the expander based on the expander configuration mode, the expander impeller diameter, and the expander rated volumetric flow rate.

[0041] The stage calculation module is used to calculate the number of stages of the expander based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure.

[0042] The final speed and final isentropic enthalpy drop acquisition module is used to calculate and adjust the speed and isentropic enthalpy drop of the expander based on the rated speed and the isentropic enthalpy drop of the expander, and to obtain the final speed and final isentropic enthalpy drop of the expander.

[0043] The power calculation module is used to calculate the power of the expander based on the final isentropic enthalpy drop of the expander.

[0044] The present invention also proposes a computer-readable storage medium storing a program or instructions that, when run on a computer, cause the computer to execute the aforementioned wellhead expander selection method.

[0045] The present invention also proposes an electronic device, including a processor coupled to a memory; the processor is used to read and execute a computer program stored in the memory to implement the aforementioned wellhead expander selection method.

[0046] Compared with the prior art, the beneficial effects of this invention are:

[0047] This invention enables the wellhead parameters and expander specifications to achieve optimal matching, making it possible to utilize residual pressure at the wellhead of oil and gas wells with variable wellhead parameters. It reduces the use of electric heating and antifreeze, saves costs, improves the pressure energy recovery rate, and has significant economic benefits. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the 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 based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of the wellhead expander selection method of the present invention;

[0050] Figure 2 This is a schematic diagram of the configuration of the wellhead and expander for wellhead pressure and low volumetric flow rate according to the present invention.

[0051] Figure 3 This is a schematic diagram of the configuration of the wellhead and expander in the present invention, which features high wellhead pressure and low volumetric flow rate.

[0052] Figure 4 This is a schematic diagram of the configuration of the wellhead and expander in the present invention, which features high wellhead pressure and large volumetric flow rate.

[0053] Figure 5 This is a schematic diagram of the wellhead expander selection system of the present invention;

[0054] Figure 6 This is a schematic diagram of the structure of the electronic device of the present invention.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1-Wellhead, 2-Expander, 201-Volume flow rate calculation and total available isentropic enthalpy drop acquisition module, 201, 202-Wellhead parallel quantity and expander configuration mode determination module, 203-Isentropic enthalpy drop calculation module, 204-Series calculation module, 205-Final rotational speed and final isentropic enthalpy drop acquisition module, 206-Power calculation module, 301-Processor, 302-Memory. Detailed Implementation

[0057] 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Before proceeding with the following steps, determine two sizes of expanders based on the production distribution of oilfield gas wells.

[0059] Specifically, the impeller diameter of a small-scale expander is defined as D.I The rated volumetric flow rate is defined as Q. I Rated speed is defined as n I Efficiency is defined as η Ⅰ Mass flow rate q mⅠ The impeller diameter of a large-scale expander is defined as D. II The rated volumetric flow rate is defined as Q. II Q II =1.5Q I Rated speed is defined as n II Efficiency is defined as η Ⅱ Mass flow rate q mⅡ .

[0060] Figure 1 This is a flowchart of a wellhead expander selection method provided by an embodiment of the present invention. In one embodiment, it specifically includes the following steps:

[0061] S101: Based on the parameters at the wellhead, calculate the volumetric flow rate of gas produced at the wellhead and obtain the total available isentropic enthalpy drop under two conditions: wellhead pressure and gas gathering pressure.

[0062] The parameters at the wellhead of a gas well include pressure, temperature, composition, and gas mass flow rate.

[0063] Based on the parameters at the wellhead, the compressibility factor and general gas molar constant of the wellhead gas production are determined. The volumetric flow rate of the wellhead gas production is then calculated using the volumetric flow rate calculation formula, as shown in equation (1).

[0064] Q ji =mRZT0 / p0 / M (1),

[0065] In the formula, Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s; m is the wellhead gas mass flow rate, in kg / s; R is the universal gas molar constant, R = 8.3143 kJ / (kmol K); Z is the compressibility factor; T0 is the wellhead temperature, in K; p0 is the wellhead pressure, in Pa; M is the molar mass of gas produced at the wellhead, in kg / kmol.

[0066] Obtain the specific enthalpy under the conditions of gas gathering pressure and wellhead pressure, and the specific enthalpy under the condition of gas gathering pressure. Subtract the specific enthalpy under the condition of gas gathering pressure from the specific enthalpy under the condition of wellhead pressure to obtain the difference. This difference is the total available isentropic specific enthalpy drop under both wellhead pressure and gas gathering pressure conditions.

[0067] S102: Determine the number of wellhead parallel connections and the expansion unit configuration mode based on the rated volumetric flow rate of the expander and the volumetric flow rate of gas produced at the wellhead.

[0068] Based on the expander's rated volumetric flow rate and the wellhead gas production volumetric flow rate, the number of wellheads connected in parallel and the expander configuration mode are determined using the wellhead and expander configuration equations to ensure that the expander's inlet volumetric flow rate matches the expander's rated volumetric flow rate.

[0069] Expander configuration modes include: configuring only one small-sized expander, configuring only one large-sized expander, multiple small-sized expanders in parallel, multiple large-sized expanders in parallel, and one or more small-sized expanders and one or more large-sized expanders in parallel.

[0070] The configuration equations for the wellhead and expander are shown in equation (2).

[0071]

[0072] In the formula, X represents the number of small-scale expanders; Y represents the number of large-scale expanders; Q I This refers to the rated volumetric flow rate of a small-sized expander, in cubic meters per second (m³). 3 / s;Q II This refers to the rated volumetric flow rate of a large-scale expander, in cubic meters per second (m³). 3 / s; ξ is the number of parallel wellheads; Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s.

[0073] In the formula, ξ and (X+Y) both take the minimum value.

[0074] S103: Calculate the isentropic specific enthalpy drop of the expander based on the expander configuration mode, expander impeller diameter, and expander rated volumetric flow rate.

[0075] Based on the expander configuration mode determined in step S102, and the expander impeller diameter and rated volume flow rate corresponding to the expander configuration mode, the isentropic enthalpy drop of the expander is calculated using empirical formulas for expander specifications. For example, if the expander configuration mode determined in step S102 is to configure only a small-scale expander, then the impeller diameter and rated volume flow rate of the small-scale expander are used as the basis for subsequent calculations.

[0076] The calculation formula is shown in equation (3).

[0077] h s =1365.7Q 2 / D 4 (3),

[0078] In the formula, h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s; D is the impeller diameter of the expander, in meters (m).

[0079] S104: Calculate the number of expander stages based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure.

[0080] Based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure, the number of expander stages is calculated using the expander stage calculation formula, as shown in equation (4).

[0081] ε=h z / h s (4),

[0082] In the formula, ε represents the number of expander stages; h z The total available isentropic enthalpy drop under both wellhead pressure and gas gathering pressure conditions, expressed in J / kg; h s This is the isentropic enthalpy drop of the expander, expressed in J / kg.

[0083] When the decimal part of the expander stage number is less than 0.5, the stage number is rounded down; when it is greater than or equal to 0.5, the stage number is rounded up.

[0084] S105: Based on the expander's rated speed and isentropic enthalpy drop, calculate and adjust the expander's speed and isentropic enthalpy drop to obtain the expander's final speed and final isentropic enthalpy drop.

[0085] S105-1: Based on the isentropic enthalpy drop of the expander, the speed of the expander is initially calculated using the speed characteristic formula, as shown in equation (5).

[0086] n = 1.839h s 0.75 / Q 0.5 (5),

[0087] In the formula, n is the rotational speed of the expander, in r / min; h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s.

[0088] S105-2: Determine whether the initially calculated expander speed is less than or equal to the expander's rated speed. If it is less than or equal to, the expander's isentropic enthalpy drop calculated in step S103 is the expander's final isentropic enthalpy drop, which is used as the data basis for executing step S106. If it is greater than, adjust the expander's isentropic enthalpy drop, recalculate the expander speed based on the adjusted expander speed, and repeat the above judgment until the adjusted expander speed is less than or equal to the expander's rated speed. At this point, the expander's final speed and final isentropic enthalpy drop are obtained, which is used as the data basis for executing step S106.

[0089] Adjusting the isentropic enthalpy drop of the expander does not affect the calculation results of the expander stages.

[0090] S106: Calculate the power of the expander based on the final isentropic enthalpy drop of the expander.

[0091] Based on the final isentropic enthalpy drop of the expander, the power of the expander is calculated using the expander power calculation formula, as shown in equation (6).

[0092] P T =ηh s q m / 1000 (6),

[0093] In the formula, P T η represents the power of the expander, measured in kW; η is the efficiency of the expander; h s The isentropic enthalpy drop of the expander is expressed in J / kg; q m This represents the mass flow rate of the expander, measured in kg / s.

[0094] Verification Example

[0095] Based on the production distribution of oilfield gas wells, two sizes of expanders were determined: specifically, for the smaller expander, the impeller diameter is 50mm and the rated volumetric flow rate is 50m³ / h. 3 / h, rated speed of 35000r / min, efficiency of 0.66, mass flow rate of 3.5kg / s; for large-scale expanders, the impeller diameter is 60mm, and the rated volumetric flow rate is 75m³ / s. 3 / h, rated speed is 60000r / min, efficiency is 0.66, and mass flow rate is 3.5kg / s.

[0096] Figure 2 It demonstrates the configuration modes of wellhead and expander with high wellhead pressure and low volumetric flow rate.

[0097] The wellhead gas mass flow rate is 1.75 kg / s, the wellhead pressure is 50 MPa, the wellhead temperature is 333.15 K, the compressibility factor is 1.1795, the molar mass of methane molecules at the wellhead is 16.04 kg / kmol, the specific enthalpy under wellhead pressure conditions is 792.79 kJ / kg, the gas gathering pressure is 11 MPa, and the specific enthalpy under gas gathering pressure conditions is 597.90 kJ / kg.

[0098] The volumetric flow rate of gas produced at the wellhead was calculated to be 26 m³ / s using the volumetric flow rate calculation formula. 3 / h.

[0099] The total available specific enthalpy drop under both wellhead pressure and gas gathering pressure conditions was calculated to be 194.89 kJ / kg.

[0100] By comparing the flow rate with the expander's rated volumetric flow rate, it was determined that two wellheads should be connected in parallel. Using the wellhead and expander configuration equations, the volumetric flow rate of the two wellheads is 52 m³ / s. 3 / h, which is close to the rated volumetric flow rate of a small-sized expander, so the configuration mode of the first-stage expander is to configure only one small-sized expander.

[0101] The isentropic enthalpy drop of the expander was calculated using empirical formulas, and the isentropic enthalpy drop of the expander was found to be approximately 45600 J / kg, thus indicating that the number of expander stages was 4.

[0102] The expander's rotational speed was calculated using the rotational speed characteristic formula, yielding a speed n of 47740 r / min. However, this is unreasonable because 47740 r / min exceeds the rated speed of 35000 r / min for a small-sized expander. Therefore, the expander's rotational speed needs to be adjusted by changing its isentropic enthalpy drop. The adjusted isentropic enthalpy drop was 30138 J / kg, satisfying the requirements of the rotational speed characteristic formula. This adjusted isentropic enthalpy drop of 30138 J / kg represents the final isentropic enthalpy drop of the expander.

[0103] The power of the expander was calculated based on the final isentropic enthalpy drop of 30138 J / kg, resulting in a power of 69.6 kW for the first stage expander.

[0104] Figure 3 It demonstrates a wellhead and expander configuration mode with high wellhead pressure and low volumetric flow rate.

[0105] The wellhead pressure is 35MPa. By comparing it with the rated flow rate of the expander, it was determined that two wellheads should be connected in parallel. The configuration mode of the first-stage expander is to configure only one small-sized expander, and the number of expander stages is 2.

[0106] Figure 4 It demonstrates the configuration modes of wellhead and expander with high wellhead pressure and large volumetric flow rate.

[0107] The wellhead pressure is 35MPa. By comparing it with the rated flow rate of the expander, it was determined that one wellhead would be used. The configuration mode of the first-stage expander is two small-sized expanders connected in parallel, and the number of expander stages is 2.

[0108] Embodiments of the present invention also provide a wellhead expander selection system, such as... Figure 5 As shown, it includes:

[0109] The volumetric flow rate calculation and total available isentropic enthalpy drop acquisition module 201 is used to calculate the volumetric flow rate of gas produced at the wellhead based on the parameters of the gas wellhead, and to obtain the total available isentropic enthalpy drop under two conditions: wellhead pressure and gas gathering pressure.

[0110] The module 202 for determining the number of wellhead parallel connections and the expander configuration mode is used to determine the number of wellhead parallel connections and the expander configuration mode based on the rated volumetric flow rate of the expander and the volumetric flow rate of gas produced at the wellhead.

[0111] The isentropic enthalpy drop calculation module 203 is used to calculate the isentropic enthalpy drop of the expander based on the expander configuration mode, the expander impeller diameter, and the expander rated volumetric flow rate.

[0112] The stage calculation module 204 is used to calculate the number of expander stages based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under two conditions: wellhead pressure and gas gathering pressure.

[0113] The final speed and final isentropic enthalpy drop acquisition module 205 is used to calculate and adjust the speed and isentropic enthalpy drop of the expander based on the rated speed and isentropic enthalpy drop of the expander, and to obtain the final speed and final isentropic enthalpy drop of the expander.

[0114] The power calculation module 206 is used to calculate the power of the expander based on the final isentropic enthalpy drop of the expander.

[0115] It should be noted that the above-mentioned modules 201 for calculating volumetric flow rate and obtaining total available isentropic enthalpy drop, 202 for determining the number of parallel wellhead units and expander configuration mode, 203 for calculating isentropic enthalpy drop, 204 for calculating series, 205 for obtaining final rotational speed and final isentropic enthalpy drop, and 206 for calculating power correspond to steps S101 to S106 in the embodiment of the wellhead expander selection method. The examples and application scenarios implemented by the above modules and corresponding steps are the same, but are not limited to the content disclosed in the above embodiment.

[0116] Embodiments of the present invention also provide a computer-readable storage medium storing a program or instructions that, when executed on a computer, cause the computer to perform the wellhead expander selection method as described in the above method embodiments.

[0117] like Figure 6 As shown, an embodiment of the present invention also provides an electronic device, including: a processor 301, the processor 301 being coupled to a memory 302, the processor 301 being used to read and execute a computer program stored in the memory 302 to implement the wellhead expander selection method as described in the above method embodiment.

[0118] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for selecting a wellhead expander, characterized in that, include: Based on the parameters at the wellhead, the volumetric flow rate of gas produced at the wellhead is calculated, and the total available isentropic enthalpy drop is obtained under two conditions: wellhead pressure and gas gathering pressure. Based on the rated volumetric flow rate of the expander and the volumetric flow rate of gas produced at the wellhead, determine the number of wellheads connected in parallel and the expander configuration mode; Based on the expander configuration mode, the expander impeller diameter, and the expander rated volumetric flow rate, calculate the isentropic enthalpy drop of the expander; The number of expander stages is calculated based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure. Based on the expander's rated speed and isentropic enthalpy drop, the expander's speed and isentropic enthalpy drop are calculated and adjusted to obtain the expander's final speed and final isentropic enthalpy drop. The power of the expander is calculated based on the final isentropic enthalpy drop of the expander.

2. The method according to claim 1, characterized in that, The volumetric flow rate of gas produced at the wellhead is calculated using the volumetric flow rate calculation formula, specifically as follows: Q ji =mRZT0 / p0 / M, In the formula, Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s; m is the wellhead gas mass flow rate, in kg / s; R is the universal gas molar constant, R = 8.3143 kJ / (kmol K); Z is the compressibility factor; T0 is the wellhead temperature, in K; p 0 represents the wellhead pressure in Pa; M represents the molar mass of gas produced at the wellhead in kg / kmol.

3. The method according to claim 1, characterized in that, The number of wellheads connected in parallel and the configuration mode of the expander are determined using wellhead and expander configuration equations, specifically as follows: In the formula, X represents the number of small-scale expanders; Y represents the number of large-scale expanders; Q I This refers to the rated volumetric flow rate of a small-sized expander, in cubic meters per second (m³). 3 / s;Q II This refers to the rated volumetric flow rate of a large-scale expander, in cubic meters per second (m³). 3 / s; ξ is the number of parallel wellheads; Q ji The volumetric flow rate of gas produced at the wellhead, measured in cubic meters per second (m³). 3 / s; The number of small-sized expanders and the number of large-sized expanders constitute the expander configuration mode.

4. The method according to claim 1, characterized in that, The isentropic enthalpy drop of the expander is calculated using empirical formulas for expander specifications, specifically as follows: h s =1365.7Q 2 / D 4 , In the formula, h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s; D is the impeller diameter of the expander, in meters (m).

5. The method according to claim 1, characterized in that, The number of expander stages is calculated using the expander stage calculation formula, specifically as follows: ε=h z / h s , In the formula, ε represents the number of expander stages; h z The total available isentropic enthalpy drop under wellhead and gas gathering pressure conditions, expressed in J / kg; h s This is the isentropic enthalpy drop of the expander, expressed in J / kg.

6. The method according to claim 1, characterized in that, The rotational speed of the expander is calculated using the rotational speed characteristic formula, specifically as follows: n=1.839h s 0.75 / Q 0.5 , In the formula, n is the rotational speed of the expander, in r / min; h s The isentropic enthalpy drop of the expander is expressed in J / kg; Q is the inlet volumetric flow rate of the expander, expressed in m³ / kg. 3 / s.

7. The method according to claim 1, characterized in that, The power of the expander is calculated using the expander power calculation formula, specifically as follows: P T =ηh s q m / 1000, In the formula, P T η represents the power of the expander, measured in kW; η is the efficiency of the expander; h s The isentropic enthalpy drop of the expander is expressed in J / kg; q m This represents the mass flow rate of the expander, measured in kg / s.

8. A wellhead expander selection system, characterized in that, include: The volumetric flow rate calculation and total available isentropic enthalpy drop acquisition module is used to calculate the volumetric flow rate of gas produced at the wellhead based on the parameters at the wellhead, and to obtain the total available isentropic enthalpy drop under two conditions: wellhead pressure and gas gathering pressure. The module for determining the number of wellheads connected in parallel and the configuration mode of the expander is used to determine the number of wellheads connected in parallel and the configuration mode of the expander based on the rated volumetric flow rate of the expander and the volumetric flow rate of the gas produced at the wellhead. The isentropic enthalpy drop calculation module is used to calculate the isentropic enthalpy drop of the expander based on the expander configuration mode, the expander impeller diameter, and the expander rated volumetric flow rate. The stage calculation module is used to calculate the number of stages of the expander based on the isentropic enthalpy drop of the expander and the total available isentropic enthalpy drop under the two conditions of wellhead pressure and gas gathering pressure. The final speed and final isentropic enthalpy drop acquisition module is used to calculate and adjust the speed and isentropic enthalpy drop of the expander based on the rated speed and the isentropic enthalpy drop of the expander, and to obtain the final speed and final isentropic enthalpy drop of the expander. The power calculation module is used to calculate the power of the expander based on the final isentropic enthalpy drop of the expander.

9. A computer-readable storage medium, characterized in that, The system stores a program or instructions that, when executed on a computer, cause the computer to perform the wellhead expander selection method as described in any one of claims 1-7.

10. An electronic device, characterized in that, Includes a processor, which is coupled to a memory; The processor is used to read and execute the computer program stored in the memory to implement the wellhead expander selection method as described in any one of claims 1-7.

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