Downhole throttling and gas lifting integrated tool and technological method

Abstract

The invention belongs to the technical field of natural gas field development, and particularly discloses an underground throttling and gas lifting integrated process method which comprises the following steps that S1, first wellbore data generated when underground throttling is not adopted under the production allocation condition are calculated, and the wellbore data comprise the well bottom flowing pressure, the well mouth temperature and the well mouth pressure; s2, calculating second wellbore data when underground throttling is adopted under the production allocation condition, wherein the wellbore data comprises wellhead temperature T1 and wellhead pressure P1 when throttling is carried out at different depths in a well; s3, calculating a hydrate forming temperature T2; s4, the minimum throttling depth Hmin is determined, and the minimum throttling depth where the hydrate is not formed is determined according to the wellhead temperature T1 and the hydrate forming temperature T2; s5, the depth of the gas lift valve is designed, and the depth of the gas lift valve is designed below the lowest throttling depth; and S6, a pipe column is put into the shaft, and the gas lift valve is installed on the outer wall of the pipe column. According to the invention, the problem of well repair caused by blockage of the underground throttling device and failure in salvage of the throttling device can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas field development, and in particular to an underground throttling gas lift integrated tool and a process method. Background Art

[0002] Natural gas accounts for a huge proportion of my country's energy structure. Research on natural gas extraction is of great significance to the environment and economic benefits. As an efficient, energy-saving and economical hydrate prevention and control technology, gas well downhole throttling technology has been widely used in Sichuan and Chongqing gas fields since the 1980s. It has played a significant role in simplifying ground processes, reducing ground investment and achieving fast construction and investment of gas wells. In recent years, as the company's development has advanced into deep carbonate gas reservoirs and tight gas reservoirs, higher requirements have been put forward for efficient development.

[0003] The downhole throttling process is to place the throttling seat at the appropriate position of the production string to achieve throttling and pressure reduction in the wellbore, and make full use of the ground temperature to heat the natural gas flow so that the temperature after throttling is higher than the hydrate formation temperature under the pressure conditions, thereby preventing the formation of hydrates, simplifying the ground process, achieving rapid construction and commissioning of gas wells, and reducing ground investment.

[0004] The gas lift process is an artificial lifting process that injects high-pressure gas into the oil pipe through a high-pressure gas source to reduce the flow pressure gradient above the gas injection point, reduce the slip loss during the lifting process, discharge the bottom hole liquid, increase the production pressure difference, and restore or improve the production capacity of the gas well. Compared with other processes, the gas lift process has great advantages. It has a wide range of applications and a low failure rate and a low workover cycle.

[0005] like Figure 1 As shown, let AA be the static liquid level position after the gas well is flooded. When high-pressure gas is injected from the casing, the high-pressure gas causes the casing liquid level to drop and the tubing liquid level to rise. When the casing liquid level drops to the inlet BB of the first gas lift valve, the gas lift valve is opened by the pressure of the high-pressure gas, and the high-pressure gas enters the tubing through the gas lift valve. Under the action of the gas expansion force, the liquid above the BB interface is lifted to the ground. At the same time, due to the large amount of high-pressure gas entering the tubing, the casing pressure is reduced. When the casing pressure drops to the closing pressure of the gas lift valve, the first gas lift valve is closed. Then, the high-pressure gas forces the casing liquid level to drop and the tubing liquid level to rise. When the casing liquid level drops to the inlet CC of the second gas lift valve, the second gas lift valve is opened by the high-pressure gas, and the liquid above the CC-BB interface is lifted to the ground. In this way, the liquid level in the tubing is continuously lowered until the gas well resumes production.

[0006] The main goals of implementing gas lift drainage are: (1) Gas lift resuscitation. This is a process drainage and gas production measure carried out in water-flooded shutdown wells and test wells to restore the gas well production capacity. (2) Continuous liquid drainage. This is a process drainage and gas production measure carried out in water wells or water-flooded wells for the purpose of achieving the overall drainage and gas production of the gas reservoir. It is used for gas wells with low gas-liquid ratio and insufficient liquid carrying capacity. The high-pressure gas source can be provided by the high-pressure gas source well or skid-mounted compressor unit through the high-pressure gas injection pipeline.

[0007] The downhole choke is installed in the production string by wire operation. It is divided into fixed downhole choke and movable downhole choke according to the placement type.

[0008] The fixed downhole choke consists of two parts: a working barrel and a choke. The working barrel needs to be lowered into the production string. The choke is anchored in the matching working barrel by slips. The sealing ring and the working barrel are reliably sealed. It has the advantages of reliable anchoring and high pressure rating, but the working barrel affects the efficiency of the plunger process.

[0009] The movable downhole choke does not require a downhole working tube and is anchored to the inner wall of the oil pipe through slips. The anchoring reliability with the oil pipe is not as good as that of the fixed choke, and the pressure difference rating is also relatively low.

[0010] The main reasons affecting the success rate of throttle salvage are:

[0011] Dirt in the formation blocks the throttle nozzle or even buries the throttle, causing the throttle to fail or be difficult to salvage, resulting in the need for well repair. In the existing technology, some wells are successfully salvaged by using a combination of continuous tubing to clean the wellbore + wireline operations, but the cost is relatively high. Summary of the invention

[0012] The invention provides a downhole throttling gas lift integrated tool and process method, aiming to solve the problem of well repair caused by downhole throttling choke blockage and throttling choke fishing failure.

[0013] The present invention is implemented by the following technical scheme: A downhole throttling gas lift integrated process method comprises the following steps:

[0014] S1, calculating the first wellbore data when downhole throttling is not used under the production allocation condition, the wellbore data including bottom hole flowing pressure, wellhead temperature and wellhead pressure;

[0015] S2, calculating the second wellbore data when downhole throttling is used under the production allocation condition, wherein the wellbore data includes the wellhead temperature T1 and the wellhead pressure P1 when throttling is carried out at different depths in the well;

[0016] S3, calculate the hydrate formation temperature T2;

[0017] S4, determining the minimum throttling depth Hmin, and determining the minimum throttling depth at which hydrates are not formed according to the wellhead temperature T1 and the hydrate formation temperature T2;

[0018] S5, the depth of the designed gas lift valve, the depth of the designed gas lift valve is below the minimum throttling depth;

[0019] S6, lowering a tubing string into the wellbore, wherein the gas lift valve is installed on the outer wall of the tubing string;

[0020] S7, when hydrates are initially formed, the gas well pressure and wellbore pressure are high, and the gas lift valve is in the open state. At this time, the gas lift valve acts as a throttle to throttle; as the gas well pressure decreases, hydrates are not formed in the wellbore, and production becomes difficult, the gas lift valve acts as a gas lift channel to drain water and produce gas.

[0021] Furthermore, if a well repair operation without well killing is adopted, a rupture disk or a plug is lowered into the interior of the tubing and below the gas lift valve; if a well killing operation is adopted, a plug is lowered into the lower part of the tubing.

[0022] Furthermore, two gas lift valves are provided, and the two gas lift valves are sequentially distributed along the axial direction of the wellbore to form a first-stage gas lift valve and a second-stage gas lift valve, and the second-stage gas lift valve is located below the first-stage gas lift valve.

[0023] Furthermore, when the gas well pressure and gas production decrease, the throttling gas nozzle is adjusted to be larger, and a plugging device is lowered below the second-stage gas lift valve.

[0024] Furthermore, a throttling gas lift working cylinder is provided in the tubing string, the gas lift valve is communicated with the throttling gas lift working cylinder, and the plug is connected in the throttling gas lift working cylinder.

[0025] Furthermore, a step matching the outer contour of the plug is provided on the inner side wall of the throttling gas lift working cylinder, and the plug is installed on the step.

[0026] Furthermore, the depth design of the gas lift valve in S5 uses the nozzle flow formula to determine the aperture d1 that meets the production allocation requirements for throttling in the wellbore, and calculates the pressure P2 of the gas lift valve at the wellbore position; the downhole opening pressure P3 (P3 <P2);

[0027]

[0028] d2 is the aperture of the gas lift valve bellows.

[0029] Furthermore, it also includes predicting the relationship between airflow and throttling pressure drop:

[0030] Determine whether the critical flow of the nozzle has reached the critical flow state. According to the principles of thermodynamics, the critical pressure ratio is:

[0031]

[0032] Where k is the gas adiabatic index;

[0033] when When , it is critical flow; otherwise, it is subcritical flow;

[0034] According to the isentropic principle of gas nozzle flow, for the subcritical flow state, the relationship between flow rate and pressure ratio can be expressed as:

[0035]

[0036] Where q sc ——Volume flow rate through the oil nozzle (under standard conditions), 10 4 m 3 / d;

[0037] P——pressure, MPa;

[0038] d——mouth diameter, mm;

[0039] T——temperature, K;

[0040] Z——gas deviation coefficient;

[0041] The subscripts 1 and 2 in the formula represent the positions before and after the throttle nozzle, respectively.

[0042] Furthermore, for critical flow, the critical pressure ratio (p2 / p1) is calculated c , maximum mouth flow q max for:

[0043]

[0044] A downhole throttling gas lift integrated tool, characterized in that it includes a tubing string, on which a first-stage gas lift valve and a second-stage gas lift valve are sequentially arranged along its axial direction, a throttling gas lift working cylinder is installed in the tubing string, the second-stage gas lift valve is connected to the throttling gas lift working cylinder, and the throttling gas lift working cylinder is located at the lower part of the tubing string, and a plug is connected in the throttling gas lift working cylinder.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] Natural gas hydrates are crystals formed under a certain pressure when the temperature of natural gas is higher than the freezing point of water. The temperature at which hydrates are formed is called the "hydration temperature". When the temperature of natural gas is equal to or lower than the dew point temperature under a certain pressure, free water will condense from the natural gas. This condensed water is an indispensable condition for the formation of hydrates.

[0047] The main conditions for the formation of natural gas hydrates are summarized as follows:

[0048] (1) The temperature of natural gas must be equal to or lower than the dew point temperature of water vapor in natural gas, and condensate water exists in natural gas;

[0049] (2) Under certain pressure and natural gas composition conditions, the natural gas temperature is lower than the hydration temperature;

[0050] (3) High operating pressure will cause the hydration temperature to rise to the operating temperature.

[0051] There are many ways to prevent hydrates, such as increasing temperature, reducing pressure, adding inhibitors, and drying gas. Increasing temperature and adding inhibitors are commonly used in mines.

[0052] 1. Inhibitor method

[0053] Under certain operating conditions, in order to prevent the formation of natural gas hydrates, the method of injecting hydrate inhibitors is usually adopted to reduce the formation temperature of hydrates, thereby achieving the purpose of preventing the formation of hydrates; after the addition of inhibitors, the water in the gas flow will dissolve in the inhibitors, changing the interaction between water molecules, thereby reducing the partial pressure of water vapor on the surface, achieving the purpose of inhibiting the formation of hydrates, so that the gas flow does not form hydrates at a lower temperature. There are many types of inhibitors, including organic inhibitors (methanol, ethanol, ethylene glycol, diethylene glycol, etc.) and inorganic inhibitors (sodium chloride, magnesium chloride and calcium chloride, etc.), and ethylene glycol is commonly used in gas production.

[0054] Methanol can be used at any operating temperature. Since methanol has a low boiling point and high vapor pressure, it is more suitable for lower operating temperatures. If it is used at higher temperatures, the evaporation loss will be greater. Methanol has a moderate degree of toxicity and can enter the human body through the respiratory tract, esophagus and skin. The toxic dose of methanol to humans is 5 to 10 ml, and the lethal dose is 30 ml. When the methanol content in the air reaches a concentration of 39 to 65 ml / m3, people will be poisoned within 30 to 60 minutes. Therefore, when using methanol as an inhibitor, you should take appropriate safety measures.

[0055] Glycol inhibitors are non-toxic, have a higher boiling point than methanol, have a lower evaporation loss, and can generally be recycled and reused. Glycol is suitable for antifreeze treatment of gas wells and gas gathering stations with large gas volumes. Glycol inhibitors have a high viscosity and will increase the system pressure drop after injection. Especially in the presence of liquid hydrocarbons, too low an operating temperature will make it difficult to separate the glycol solution from the liquid hydrocarbons, and increase the dissolution loss and carryover loss in the liquid hydrocarbons.

[0056] 2. Heating method

[0057] The essence of this method is to raise the temperature of the gas flow above the temperature at which hydrates are formed. Steam heating and jacket furnace heating are often used. The former uses the steam generated by a boiler to heat natural gas, and the latter is indirect heating with water and steam as the heat transfer medium.

[0058] Adopt downhole throttling to reduce the wellhead pressure of gas wells:

[0059] Installing a downhole throttler in a gas well to reduce the wellhead pressure and gas transmission pressure of the gas well can not only prevent the formation of hydrates in the gas well, but also increase the flow velocity of natural gas in the wellbore, which helps the gas well to drain liquid.

[0060] There are two types of downhole throttling tools for gas wells: movable downhole throttlers and fixed downhole throttlers. At present, this technology has been successfully used in multiple gas wells in gas fields such as Sichuan, Shengli, Zhongyuan, Qinghai, Xinjiang, and Changqing. However, due to certain difficulties in tripping the tools, it has not been widely promoted and applied at present.

[0061] The flow of the oil, gas, and water mixture through the throttling nozzle belongs to nozzle flow. The dynamic parameters of the mixture before entering the throttling nozzle are: pressure (P1), temperature (T1), specific volume (V1), and flow velocity (W1); the dynamic parameters at the outlet are: pressure (P2), temperature (T2), specific volume (V2), and flow velocity (W2). Throttling is generally considered an isentropic (adiabatic) expansion process, that is, the pressure drops (P2 < P1), the flow velocity increases (W2 > W1), and in the presence of gas, the temperature drops (T2 < T1). The throttling pressure ratio is:

[0062]

[0063] The purpose of throttling is to convert pressure energy into kinetic energy to obtain an increase in flow velocity. The higher the upstream pressure and the smaller the pore throat, the greater the velocity increment obtained downstream. However, this is not endless. When the ratio of the upstream and downstream pressures reaches a certain value, the flow velocity of the fluid through the choke will approach the speed of sound (a). At this time, no matter how much the downstream pressure is reduced, the flow velocity (W2) will no longer increase and will maintain the speed of sound wave or pressure wave propagation. This is the so-called critical flow state of the nozzle.

[0064] There are many drawbacks to surface throttling of high-pressure gas wells. For example, the wellhead and some surface pipelines before throttling still bear high pressure. Switching the pressure regulating valve will cause harmful agitation to the bottom hole during production. The liquid-carrying capacity of the gas flow is relatively low. Seriously, throttling pressure reduction will cause a temperature drop, which is likely to form an ice blockage at the throttling point, seriously affecting production. Therefore, high-pressure gas wells usually use a pressure regulating valve for multi-stage pressure reduction and heat preservation production on the surface. And surface heat preservation heating will waste a lot of natural gas resources and requires corresponding management personnel.

[0065] Through the research on downhole throttling technology and hydrate prevention and control technology for gas wells, it is possible to eliminate the single well ground water jacket heating furnace, simplify the ground process of the well site, reduce the number of well station management personnel and labor intensity, and improve the level of gas well automation management, which has significant economic and social benefits.

[0066] In terms of throttling control mechanism, there is not much difference between the surface throttle and the bottom hole throttle. In other words, the surface throttle with changed size placed at a proper position underground is the underground throttle. However, the former is on the surface and the latter is underground, and there are certain differences between the two. These differences are:

[0067] ⑴ The upstream and downstream pressures of the surface throttle nozzle are restricted by the wellhead pressure and the horizontal (undulating) pipe flow pressure gradient; the upstream and downstream pressures of the downhole throttle nozzle are restricted by the flow pressure at the depth and the vertical pipe flow pressure gradient.

[0068] ⑵ Because the two are in different positions (such as Figure 2 The geothermal conditions available to them are different, so their functions are also different.

[0069] Traditional ground water jacket boiler heating or electric blanket heating to prevent hydrates requires a large amount of electricity or burns natural gas, which easily leads to waste of natural gas and increased costs.

[0070] In addition, downhole throttling to prevent hydrates requires rope operations. Some gas wells, such as tight gas, obtain production capacity through large-scale fracturing. In the early stage, there will be sand and other dirt, which will also block the throttle, affecting the fixation and salvage of the throttle, and seriously causing salvage failure and well repair.

[0071] Traditional downhole throttling is to lower a throttle into the wellbore and work for a long time. Due to sand production and other reasons, it often leads to failure to salvage the throttle, which consumes a lot of manpower, material and financial resources, and seriously leads to the need to rework the gas well. The present technical solution proposes a method of combining downhole throttling with gas lift technology. The throttling is performed on the outside of the tubing, so there is no need to salvage it at all. This not only solves the problem of downhole throttling salvage failure and achieves the purpose of preventing hydrates, but also combines the function of achieving gas lift drainage and gas production in the later stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0073] Figure 1 It is the principle diagram of the gas lift drainage gas production process in the background technology;

[0074] Figure 2 It is a schematic diagram of a choke (throttle nozzle) in a multiphase flow in the background technology;

[0075] Figure 3 It is a structural schematic diagram of a downhole throttling gas lift integrated tool in an embodiment of the present invention;

[0076] Figure 4 It is a structural schematic diagram of a throttling gas lift mandrel in a downhole throttling gas lift integrated tool according to an embodiment of the present invention;

[0077] Figure 5 It is a structural schematic diagram of a downhole throttling gas lift integrated tool after a plug is inserted into a throttling gas lift working cylinder in an embodiment of the present invention;

[0078] Figure 6 It is the fitting curve of gas production and bottom hole pressure under the production allocation condition;

[0079] Figure 7 It is the fitting curve diagram of different gas production and wellbore pressure when downhole throttling is not used;

[0080] Figure 8 It is the fitting curve diagram of different gas production and wellbore temperature when downhole throttling is not adopted;

[0081] Fig. 9 It is the fitting curve diagram of different gas production and wellbore pressure when downhole throttling is adopted;

[0082] Fig.10 It is the fitting curve diagram of different gas production and wellbore temperature when downhole throttling is adopted;

[0083] Fig.11 The fitting curves of hydrate formation temperature obtained by different methods are shown in Figure 2.

[0084] Fig.12 Schematic diagram of mouth flow;

[0085] Fig.13 Mouth flow characteristics.

[0086] Marks and corresponding parts names in the attached drawings:

[0087] Wellbore 1, tubing string 2, first-stage gas lift valve 3, second-stage gas lift valve 4, throttling gas lift working cylinder 5, rupture disk 6, plug 7. DETAILED DESCRIPTION

[0088] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0089] like Figure 3As shown, this embodiment provides a downhole throttling gas lift integrated tool, including a tubing string 2, on which a first-stage gas lift valve 3 and a second-stage gas lift valve 4 are arranged in sequence along the axial direction, the second-stage gas lift valve 4 is located below the first-stage gas lift valve 3, a throttling gas lift working cylinder 5 is installed in the tubing string 2, the second-stage gas lift valve is connected to the throttling gas lift working cylinder 5, and the throttling gas lift working cylinder 5 is located at the lower part of the tubing string 2, and a plug 7 is connected to the throttling gas lift working cylinder 5.

[0090] In this embodiment, two rupture disks 6 are further installed inside the pipe string 2, and the two rupture disks 6 are respectively located below the first-stage gas lift valve and the second-stage gas lift valve.

[0091] This embodiment also discloses an underground throttling gas lift integrated process method, including the following steps:

[0092] S1, calculates the first wellbore data when downhole throttling is not used under production allocation conditions. The wellbore data includes bottom hole flowing pressure, wellhead temperature and wellhead pressure, such as Figure 6 , Figure 7 and Figure 8 As shown;

[0093] S2, calculate the second wellbore data when downhole throttling is used under the production allocation condition, the wellbore data includes the wellhead temperature T1 and the wellhead pressure P1 when throttling is carried out at different depths in the well, such as Fig. 9 and Fig.10 As shown;

[0094] S3, calculate the hydrate formation temperature T2, according to the statistical data in Table 1, the formation temperature is as follows Fig.11 In this embodiment, the wellhead temperature, wellhead pressure, bottom hole flowing pressure and hydrate formation temperature are calculated by using the multiphase flow calculation method and the mouth flow formula;

[0095] Table 1 Hydrate formation temperature ℃

[0096] Pressure MPa Ponomarev Chart Regression Statistical Thermodynamics 1 17.5118 23.90 21.69 20.03 2 14.1361 22.18 20.79 18.59 3 13.0437 21.53 20.46 18.05 4 12.273 21.04 20.20 17.64 5 11.6636 20.64 19.99 17.30 6 11.5533 20.56 19.95 17.24 7 11.6793 20.65 20.00 17.31 8 11.8508 20.76 20.06 17.41 9 12.0029 20.87 20.11 17.50 10 12.1008 20.93 20.15 17.55 11 11.8571 20.77 20.06 17.41 12 11.6291 20.61 19.98 17.28 13 11.4146 20.46 19.90 17.16 14 11.2118 20.32 19.83 17.04 15 11.0191 20.18 19.75 16.92 16 10.8355 20.04 19.68 16.81

[0097] S4, determine the minimum throttling depth H min , the minimum throttling depth without hydrate formation is determined according to the wellhead temperature T1 and the hydrate formation temperature T2, such as Fig.11 As shown in the figure, the existing gas-liquid two-phase flow temperature and pressure prediction model is used to accurately predict the temperature and pressure at any position of the wellbore. On this basis, the minimum throttling depth H is calculated by an iterative method. min ;

[0098] S5, design the depth of the gas lift valve, design the depth of the gas lift valve below the minimum throttling depth, such as Fig.12 , Fig.13 As shown;

[0099] The depth design of the gas lift valve uses the nozzle flow formula to determine the aperture d1 that meets the production requirements for throttling in the wellbore 1, and calculates the pressure P2 of the gas lift valve at the wellbore position; according to the throttling aperture d1 and the wellbore depth H, the downhole opening pressure P3 (P3 <P2);

[0100]

[0101] d2 is the aperture of the gas lift valve bellows.

[0102] Choke critical flow refers to the flow state when the fluid flows through the choke at a high speed, reaching the propagation speed of the pressure wave in the fluid medium, that is, the speed of sound. In the critical flow state, the pressure change downstream of the choke has no effect on the gas flow rate, because the pressure disturbance will not propagate upstream faster than the speed of sound. Therefore, in order to predict the choke flow dynamics, that is, the relationship between the gas flow rate and the throttling pressure drop, it is necessary to determine whether the critical flow state is reached.

[0103] Therefore, a downhole throttling gas lift integrated process method in this embodiment also includes predicting the relationship between the gas flow and the throttling pressure drop:

[0104] Determine whether the critical flow of the nozzle has reached the critical flow state. According to the principles of thermodynamics, the critical pressure ratio is:

[0105]

[0106] Where k is the gas adiabatic index;

[0107] when When , it is critical flow; otherwise, it is subcritical flow;

[0108] According to the isentropic principle of gas nozzle flow, for the subcritical flow state, the relationship between flow rate and pressure ratio can be expressed as:

[0109]

[0110] Where q sc ——Volume flow rate through the oil nozzle (under standard conditions), 10 4 m 3 / d;

[0111] P——pressure, MPa;

[0112] d——mouth diameter, mm;

[0113] T——temperature, K;

[0114] Z——gas deviation coefficient;

[0115] Pc——critical pressure

[0116] The subscripts 1 and 2 in the formula respectively represent the parameters before and after the throttle nozzle.

[0117] For critical flow, calculate the critical pressure ratio (p2 / p1)c, the maximum nozzle flow rate q max for:

[0118]

[0119] S6, a tubing string is lowered into the wellbore, and a gas lift valve is installed on the outer wall of the tubing string. If a well repair operation without well killing is adopted, a rupture disk or a plug is lowered inside the tubing string and below the gas lift valve. If a well killing operation is adopted, a plug is lowered into the lower part of the tubing string. If there is no rupture disk in the wellbore on the basis of a traditional gas lift working cylinder, a plug can be lowered below the gas lift valve. If the throttling gas nozzle needs to be adjusted due to a decrease in gas well pressure and a decrease in production, a plug can be lowered below the second-stage gas lift valve.

[0120] Combination Figure 4 and Figure 5 As shown, in this embodiment, a throttling gas lift working cylinder is lowered into the tubing, the gas lift valve is connected to the throttling gas lift working cylinder, the plug is connected in the throttling gas lift working cylinder, and a step matching the outer contour of the plug is provided on the inner wall of the throttling gas lift working cylinder, and the plug is installed on the step.

[0121] S7, when hydrates are initially formed, the gas well pressure and wellbore pressure are high, and the gas lift valve is in an open state. At this time, the gas lift valve acts as a throttle to throttle. As the gas well pressure decreases, hydrates are not formed in the wellbore, and when production becomes difficult, the gas lift valve acts as a gas lift channel to drain water and produce gas. If the well is initially pressured and repaired, the workover fluid can be discharged from the wellbore through gas lift after the workover.

[0122] In this embodiment, when the gas well pressure and gas production decrease, the throttling gas nozzle is adjusted to be larger, and a plugging device is lowered below the second-stage gas lift valve.

[0123] According to actual needs, if the well repair operation without well killing is adopted, there may be a rupture disk or a plug. If the well killing operation is adopted, if there is no rupture disk, a plug can be lowered later. The lower part of the throttling gas lift working cylinder and the inner side thereof can be made into a raised or recessed step, and the plug can be placed through the step. In actual operation, the throttling working cylinder can also be combined with the throttling working cylinder at the lower part of the gas lift working cylinder to form a throttling gas lift working cylinder.

[0124] 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. An underground throttling gas lift integrated process method, characterized in that: The following steps are involved: S1, calculating the first wellbore data when downhole throttling is not used under the production allocation condition, the wellbore data including bottom hole flowing pressure, wellhead temperature and wellhead pressure; S2, calculating the second wellbore data when downhole throttling is used under the production allocation condition, wherein the wellbore data includes the wellhead temperature T1 and the wellhead pressure P1 when throttling is carried out at different depths in the well; S3, calculate the hydrate formation temperature T2; S4, determine the minimum throttling depth H min , determine the minimum throttling depth without hydrate formation based on the wellhead temperature T1 and the hydrate formation temperature T2; S5, the depth of the designed gas lift valve, the depth of the designed gas lift valve is below the minimum throttling depth; S6, lowering a tubing string into the wellbore, wherein the gas lift valve is installed on the outer wall of the tubing string; S7, when hydrates are initially formed, the gas well pressure and wellbore pressure are high, and the gas lift valve is in the open state. At this time, the gas lift valve acts as a throttle to throttle; as the gas well pressure decreases, hydrates are not formed in the wellbore, and production becomes difficult, the gas lift valve acts as a gas lift channel to drain water and produce gas.

2. The downhole throttling gas lift integrated process method according to claim 1, characterized in that: If a well-repair operation without well-killing is adopted in S6, a rupture disk or a plug is lowered into the interior of the tubing and below the gas lift valve. If a well-killing operation is adopted, a plug is lowered into the lower part of the tubing.

3. The downhole throttling gas lift integrated process method according to claim 1, characterized in that: The gas lift valves are provided with two, and the two gas lift valves are sequentially distributed along the axial direction of the wellbore to form a first-stage gas lift valve and a second-stage gas lift valve, and the second-stage gas lift valve is located below the first-stage gas lift valve.

4. The downhole throttling gas lift integrated process method according to claim 3 is characterized in that: When the gas well pressure and gas production decrease, the throttling gas nozzle is adjusted to be larger, and a plugging device is lowered below the second-stage gas lift valve.

5. A downhole throttling gas lift integrated process method according to any one of claims 2 to 4, characterized in that: A throttling gas lift working cylinder is arranged in the tubing string, the gas lift valve is communicated with the throttling gas lift working cylinder, and the plug is connected in the throttling gas lift working cylinder.

6. The downhole throttling gas lift integrated process method according to claim 5, characterized in that: A step matching the outer contour of the plug is provided on the inner side wall of the throttling gas lift working cylinder, and the plug is installed on the step.

7. The downhole throttling gas lift integrated process method according to claim 1, characterized in that: In S5, the depth design of the gas lift valve uses the nozzle flow formula to determine the aperture d1 that meets the production allocation requirements for throttling in the wellbore, and calculates the pressure P2 at the location of the gas lift valve in the wellbore; the downhole opening pressure P3 (P3 <P2); d2 is the aperture of the gas lift valve bellows.

8. The downhole throttling gas lift integrated process method according to claim 7, characterized in that: It also includes the prediction of the relationship between airflow and throttling pressure drop: Determine whether the critical flow of the nozzle has reached the critical flow state. According to the principles of thermodynamics, the critical pressure ratio is: Where k is the gas adiabatic index; when When , it is critical flow; otherwise, it is subcritical flow; According to the isentropic principle of gas nozzle flow, for the subcritical flow state, the relationship between flow rate and pressure ratio can be expressed as: Where q sc ——Volume flow rate through the oil nozzle (under standard conditions), 10 4 m 3 / d; P——pressure, MPa; d——mouth diameter, mm; T——temperature, K; Z——gas deviation coefficient; The subscripts 1 and 2 in the formula represent the positions before and after the throttle nozzle, respectively.

9. The downhole throttling gas lift integrated process method according to claim 8, characterized in that: For critical flow, calculate the critical pressure ratio (p2 / p1) c , maximum mouth flow q max for:

10. A downhole throttling gas lift integrated tool, characterized in that: It comprises a tubing string, on which a first-stage gas lift valve and a second-stage gas lift valve are sequentially arranged along the axial direction thereof, a throttling gas lift working cylinder is installed in the tubing string, the second-stage gas lift valve is connected to the throttling gas lift working cylinder, and the throttling gas lift working cylinder is located at the lower part of the tubing string, and a plug is connected in the throttling gas lift working cylinder.

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