Mixed injection device

Abstract

The invention relates to the technical field of oilfield development, in particular to a mixed injection device. The embodiment of the invention provides a mixed injection device. The mixed injection device comprises an inner tubular column, a mixing body and an injection space. The inner pipe column is arranged underground; the mixing body is connected with the lower portion of the inner tubular column and provided with a suction cavity and a mixing cavity which are sequentially communicated from top to bottom, the suction cavity is provided with a throttling part, a suction channel is arranged on the inner wall of the throttling part, one end of the suction channel is communicated with the injection space, the other end of the suction channel is communicated with the suction cavity, and an outlet is formed in the lower portion of the mixing cavity and is close to the communicating groove. Wherein the communicating groove is formed in the well wall and communicates with the stratum; the injection space is arranged on the outer sides of the inner pipe column and the suction cavity, the inner pipe column is used for injecting a first medium, and the injection space is used for injecting a second medium; when the first medium flows through the throttling part, the second medium in the injection space can be sucked into the suction cavity through the suction channel, and then the second medium and the first medium are mixed in the mixing cavity and then enter the stratum through the outlet.

Description

Technical Field

[0001] The invention relates to the technical field of oil field development, in particular to a mixing injection device. Background Art

[0002] With the development of oil fields, the contradictions within and between layers of heterogeneous multi-layer sandstone oil fields have further intensified. In the process of water flooding and polymer flooding, when the oil layers with different permeabilities are co-injected and co-produced, the injected water and polymer advance along the high permeability layer, forming a single layer advance in the vertical direction and a tongue advance in the plane, causing the injected water and polymer to break through in advance, resulting in low sweep of the medium and low permeability layers and poor oil recovery effect. In order to improve the utilization of medium and low permeability oil layers and adjust the contradictions between layers and within layers, it is necessary to use profile adjustment technology to plug the high permeability layer, improve the effect of water flooding and polymer flooding, and achieve the purpose of stabilizing oil and controlling water.

[0003] In the related technology, in order to improve the profile control effect, gas foam profile control is used as a common method. Gas, foam and profile control agent are often mixed on the ground and then injected into the well. However, since the wellhead is far away from the formation, the mixed medium may be stratified due to density differences in the process of entering the formation from the wellhead, resulting in poor mixing effect and failure to achieve the effect of mixed injection. Summary of the invention

[0004] The present application provides a mixing injection device, which to some extent improves the technical problem in the related art that due to the long distance between the wellhead and the formation, the mixed medium may be stratified due to density differences in the process of entering the formation from the wellhead, resulting in poor mixing effect and failure to achieve the mixed injection effect.

[0005] The embodiment of the present application provides a mixing injection device, comprising:

[0006] An inner pipe string is set downhole;

[0007] A mixing body is connected to the lower part of the inner pipe column, and the mixing body has a suction chamber and a mixing chamber which are connected in sequence from top to bottom. The suction chamber has a throttling part, and the inner wall of the throttling part is provided with a suction channel, one end of the suction channel is connected to the injection space, and the other end is connected to the suction chamber. An outlet is provided at the lower part of the mixing chamber, and the outlet is arranged close to the connecting groove; wherein the connecting groove is arranged on the well wall and is connected to the formation;

[0008] An injection space is arranged outside the inner tube column and the suction chamber, the inner tube column is used to inject a first medium, and the injection space is used to inject a second medium;

[0009] When the first medium flows through the throttling portion, the second medium in the injection space can be sucked into the suction chamber through the suction channel, and then mixed with the first medium in the mixing chamber and enter the formation through the outlet and the connecting groove.

[0010] In some embodiments, the mixing body includes a first shell, a second shell and an injection sleeve which are connected in sequence from top to bottom, the suction chamber is arranged in the first shell, the mixing chamber is arranged in the second shell, and the outlet is arranged at the lower end of the injection sleeve.

[0011] In some embodiments, the inner diameter of the lower end of the injection sleeve is larger than the inner diameter of the upper end.

[0012] In some embodiments, a plurality of the suction channels are arranged at intervals along the circumference of the throttling portion.

[0013] In some embodiments, the suction channel is arranged to be tilted downward relative to a center line of the suction chamber.

[0014] In some embodiments, the injection space is formed between the inner pipe string and the outer wall of the suction cavity and the well wall.

[0015] In some embodiments, the device further comprises an outer tube column, which is spaced apart from the inner tube column and the outer side of the suction chamber, and the injection space is formed between the outer wall of the inner tube column and the suction chamber and the inner wall of the outer tube column.

[0016] In some embodiments, a sealing member is provided on the circumference of the mixing body, and the sealing member is disposed at the lower portion of the suction chamber, and the sealing member seals the lower portion of the injection space.

[0017] In some embodiments, a packer is provided between the outer tubing string and the well wall.

[0018] In some embodiments, the first medium is steam, and the second medium is nitrogen or nitrogen foam.

[0019] The beneficial effects of this application are as follows:

[0020] The present application provides a mixing injection device. When the first medium flows through a throttling portion, the speed increases and the pressure decreases, forming a low-pressure area, thereby generating suction to suck the second medium in the injection space into the suction chamber through the suction channel, and then mix with the first medium in the mixing chamber and enter the formation through the outlet. Since the outlet is arranged close to the connecting groove, the first medium and the second medium can reach the formation immediately through the connecting groove after mixing, thereby improving the medium mixing effect. To a certain extent, it improves the technical problem that due to the long distance between the wellhead and the formation, the mixed medium may be stratified due to density differences in the process of entering the formation from the wellhead, resulting in poor mixing effect and failure to achieve the effect of mixed injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0022] Figure 1 The structure of the mixing injection device is shown Figure 1 ;

[0023] Figure 2 for Figure 1 A partial cross-sectional view of the mixing body;

[0024] Figure 3 The structure of the mixing injection device is shown Figure 2 .

[0025] Description of reference numerals:

[0026] 1-mixing injection device, 2-well wall, 3-formation, 4-connecting groove, 100-inner tubular column, 200-mixing body, 210-first shell, 211-suction chamber, 2111-throttling part, 2112-suction channel, 220-second shell, 221-mixing chamber, 230-injection space, 240-injection sleeve, 241-outlet, 250-outer tubular column, 260-seal, 270-packer. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that all directional indications in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between various components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] Combination Figure 1 and Figure 2 The embodiment of the present application provides a mixing injection device 1, comprising an inner pipe column 100, a mixing body 200 and an injection space 230. The inner pipe column 100 is arranged underground; the mixing body 200 is connected to the lower part of the inner pipe column 100, and the mixing body 200 has a suction chamber 211 and a mixing chamber 221 which are connected from top to bottom in sequence, the suction chamber 211 has a throttling part 2111, and the inner wall of the throttling part 2111 is provided with a suction channel 2112, one end of the suction channel 2112 is connected to the injection space 230, and the other end is connected to the suction chamber 211, and the lower part of the mixing chamber 221 is provided with an outlet 241, and the outlet 241 is arranged near the connecting groove 4, and the connecting groove 4 is connected to the mixing chamber 221. The through groove 4 is arranged on the well wall 2 and is connected with the formation 3; the injection space 230 is arranged on the outside of the inner pipe column 100 and the suction chamber 211, the inner pipe column 100 is used to inject the first medium, and the injection space 230 is used to inject the second medium; wherein, when the first medium flows through the throttling portion 2111, the second medium in the injection space 230 can be sucked into the suction chamber 211 through the suction channel 2112, and then mixed with the first medium in the mixing chamber 221, and then pass through the outlet 241 and enter the formation 3 through the connecting groove 4.

[0032] The inner pipe string 100 can be lowered from the injection wellhead to the oil layer. The inner pipe string 100 can be an oil pipe or an insulated pipe. The oil pipe is a conventional injection medium channel, such as a water injection channel or a gas injection channel. When the injection medium is steam, an insulated pipe is required as the injection medium channel to reduce heat loss. The inner pipe string 100 and the mixing body 200 can be detachably connected by screw connection, clamping connection, etc. The inner pipe string 100 is connected to the suction chamber 211. After the medium leaves the outlet 241 of the inner pipe string 100, it can enter the suction chamber 211.

[0033] The relationship between flow rate, flow velocity and cross-sectional area is: Q = v*S, where Q is flow rate, v is flow velocity, and S is cross-sectional area. The throttle portion 2111 is the area where the cross section becomes narrower, and the first medium and the second medium can be injected at the same time. When the first medium enters the suction chamber 211, when it flows through the throttle portion 2111, under the condition that Q remains unchanged, the cross-sectional area S becomes smaller, so the flow velocity v increases, the pressure becomes smaller, and suction is generated. Since the suction channel 2112 connects the suction chamber 211 and the injection space 230, the second medium injected into the space 230 can be sucked into the suction chamber 211 and fully mixed with the first medium in the mixing chamber 221 to form a mixed medium, and then enter the formation 3 from the outlet 241.

[0034] It is obvious that the outlet 241 is arranged close to the horizontal extension line of the connecting groove 4, that is, the first medium and the second medium can immediately reach the formation 3 through the connecting groove 4 after being mixed, thereby improving the medium mixing effect. To a certain extent, it improves the technical problem that due to the long distance between the wellhead and the formation 3, the mixed medium may be stratified due to the density difference in the process of entering the formation 3 from the wellhead, resulting in poor mixing effect and failure to achieve the effect of mixed injection.

[0035] The cross section of the suction chamber 211 may be a structure that narrows and then widens from top to bottom, that is, the inner wall of the middle of the suction chamber 211 bulges inward to form a throttling portion 2111. Specifically, the inner wall of the suction chamber 211 may be arc-shaped, that is, the change in the width of the suction chamber 211 cross section is a smooth transition.

[0036] In some embodiments, the mixing body 200 includes a first shell 210, a second shell 220 and an injection sleeve 240 which are connected to each other in sequence from top to bottom, the suction chamber 211 is arranged in the first shell 210, the mixing chamber 221 is arranged in the second shell 220, and the outlet 241 is arranged at the lower end of the injection sleeve 240.

[0037] The suction chamber 211 and the mixing chamber 221 are arranged in different shells to facilitate the manufacture of the structure of the suction chamber 211. After the first medium and the second medium are mixed in the mixing chamber 221, they enter the formation 3 through the outlet 241 of the injection sleeve 240. The first shell 210 and the second shell 220, and the second shell 220 and the injection sleeve 240 can also be connected by screw connection, clamping connection, etc., which is not limited.

[0038] In some embodiments, in order to allow more mixed medium to flow out from the outlet 241 , the inner diameter of the lower end of the injection sleeve 240 is greater than the inner diameter of the upper end.

[0039] Since the first medium and the second medium need to be fully mixed in the mixing chamber 221, the cross-sectional width of the mixing chamber 221 can be narrower to facilitate full contact between the first medium and the second medium. In order to allow more mixed medium to flow out of the outlet 241 at one time to improve the injection effect, the inner diameter of the lower end of the injection sleeve 240 can be larger than the inner diameter of the upper end, that is, the inner diameter of the outlet 241 is larger than the inner diameter of the upper end of the injection sleeve 240.

[0040] In some embodiments, in order to allow the second medium injected into the space 230 to be fully sucked into the suction chamber 211 , a plurality of suction channels 2112 are provided at intervals along the circumference of the throttling portion 2111 .

[0041] Multiple groups of suction channels 2112 may be provided from top to bottom, and each group includes a plurality of suction channels 2112 spaced apart along the circumference of the throttling portion 2111 , so that the second medium injected into the space 230 can be fully sucked into the suction chamber 211 .

[0042] In some embodiments, in order to increase the speed at which the second medium enters the suction chamber 211 , the suction channel 2112 is tilted downward relative to the center line of the suction chamber 211 .

[0043] Since the second medium flows from the injection space 230 toward the center line of the suction chamber 211, the suction channel 2112 is tilted downward relative to the center line of the suction chamber 211, so that the second medium can flow faster under the action of gravity, thereby accelerating the mixing efficiency with the first medium.

[0044] In some embodiments, the injection space 230 is formed in two ways, such as Figure 1 As shown, the first method is to form an injection space 230 between the inner pipe string 100 and the outer wall of the suction chamber 211 and the well wall 2. That is, after the inner pipe string 100 is connected to the mixing body 200 and extended into the well, the injection space 230 is formed between the inner pipe string 100 and the outer wall of the suction chamber 211 and the well wall 2. When the injection space 230 is injected with gas, the injection space 230 can be formed in the first way.

[0045] like Figure 3 As shown, the second forming method needs to add an outer column 250, that is, the device also includes an outer column 250, and the outer column 250 is arranged at intervals outside the inner column 100 and the suction chamber 211, and an injection space 230 is formed between the outer walls of the inner column 100 and the suction chamber 211 and the inner wall of the outer column 250. When the inner column 100 needs to be injected with gas, the injection space 230 can be formed in the second way.

[0046] Of course, the injection space 230 formed by these two methods is an annular space.

[0047] In some embodiments, in order to ensure that the second medium injected into the space 230 can completely enter the suction chamber 211 , a seal 260 is provided on the circumference of the mixing body 200 . The seal 260 is disposed at the lower part of the suction chamber 211 and seals the lower part of the injection space 230 .

[0048] The seal 260 can be disposed on the outer wall of the mixing chamber 221 and seal the opening below the injection space 230, thereby preventing the second medium from directly entering the formation 3 without being mixed. The seal can be an annular block structure and is disposed around the outer side of the mixing body 200.

[0049] In some embodiments, in order to prevent the mixed medium from flowing back, a packer 270 is provided between the outer tubing string 250 and the well wall 2 .

[0050] When the injection space 230 is formed in the second manner, an annular space is also formed between the outer tubular column 250 and the well wall 2. In order to prevent the mixed medium from flowing back from the annular space, a packer 270 can be set between the outer tubular column 250 and the well wall 2 for isolation.

[0051] In order to more clearly introduce the embodiments of the present application, the following describes the usage of the embodiments of the present application.

[0052] The mixing body 200 is installed at the lower end of the oil pipe and extended into the well, so that the outlet 241 of the mixing body 200 is arranged close to the connecting groove 4, and then the profile control agent is injected into the oil pipe, and nitrogen is injected into the injection space 230. When the injected nitrogen reaches the suction chamber 211 of the mixing body 200, it is sucked into the mixing chamber 221 through the suction channel 2112 and mixed with the profile control agent, and then injected into the formation 3 through the outlet 241 and the connecting groove 4. Compared with the previous injection method of injecting nitrogen and profile control agent at the wellhead at the same time, this injection method can improve the mixing uniformity of the two media, thereby better improving the profile control effect.

[0053] It should be noted that the mixed injection device 1 provided in the embodiment of the present application can not only improve the profile control effect, but also play a role in other application scenarios by selecting different media. The following examples are given:

[0054] 1. In the heavy oil development scenario, the mixed injection device 1 provided in the embodiment of the present application is used, and the first medium is steam, and the second medium is nitrogen or nitrogen foam, which can improve the downhole steam dryness:

[0055] In the related technologies, heavy oil development is mainly based on throughput, steam drive and SAGD. Steam injection is the main means of heavy oil production, but there is a problem of large heat loss along the injected steam, which leads to the fact that under the existing ground boiler and wellbore insulation process limit conditions, for heavy oil reservoirs with a well depth greater than 1300m, the injected steam reaches the bottom of the well to meet the development requirements of steam drive or SAGD. (Steam drive requires the bottom of the well to have a dryness greater than 50%, and SAGD requires the bottom of the well to have a dryness greater than 70%). Therefore, how to improve the bottom of the well steam dryness has become an urgent problem to be solved. At present, new processes and methods for improving the downhole steam dryness, such as superheated steam injection, can improve the bottom of the well steam dryness to a certain extent, but there are limitations such as limited superheat, and superheated steam has higher requirements on the performance of the wellhead, steam injection pipeline, and wellbore string, and cannot be widely promoted and applied. Under the current electricity price conditions, downhole electric heating, as a method to assist in improving the downhole steam dryness, is affected by factors such as economy and ground power grid constraints, and cannot be promoted and applied on a large scale.

[0056] Based on this, the mixed injection device 1 provided in the embodiment of the present application can be used, and the first medium is steam, and the second medium is nitrogen or nitrogen foam. That is, steam is injected into the insulation tube, and nitrogen or nitrogen foam is injected into the injection space 230. When the nitrogen or nitrogen foam reaches the suction chamber 211, it is sucked into the mixing chamber 221 and mixed with steam, and then injected into the formation 3 through the outlet 241. As the insulation effect of the insulation tube decreases with the extension of the service life, nitrogen or nitrogen foam is injected into the injection space 230, which can play a role in insulation and improve the steam injection dryness at the bottom of the well. In addition, nitrogen can be mixed with steam through the mixing body 200 and injected into the formation 3. Due to the low density of nitrogen, an insulation zone can be formed on the upper part of the oil layer after being injected into the formation 3, thereby further allowing the injected steam to bring more heat enthalpy into the formation 3 to improve the steam injection effect.

[0057] 2. In the process of chemical flooding of thick oil reservoirs, the mixed injection device 1 provided in the embodiment of the present application is used, and different media are selected at different stages to improve the chemical flooding effect of thick oil reservoirs:

[0058] In the related technology, during the chemical flooding process of thick oil reservoirs, due to the gravity of the injected fluid, the lower oil layer is better utilized, while the upper oil layer is less utilized. At the same time, due to the underdeveloped interlayers in the thick oil reservoirs, the traditional concentric injection or packer injection is not effective. Therefore, how to solve the chemical flooding effect of thick oil reservoirs has become an urgent problem to be solved.

[0059] Based on this, the mixed injection device 1 provided in the embodiment of the present application can be used, and the chemical flooding process of thick oil reservoirs can be divided into three stages, each stage using different media, the first stage improving the profile adjustment effect, the second stage improving the upper oil layer utilization, and the third stage uniform utilization, thereby achieving improved chemical flooding effect of thick oil reservoirs.

[0060] Specifically, in the first stage, nitrogen or nitrogen foam is injected into the inner pipe column 100, and polymer is injected into the injection space 230. When the polymer reaches the suction chamber 211, it is sucked into the mixing chamber 221 and mixed with the nitrogen or nitrogen foam, and then injected into the formation 3 through the outlet 241. Due to the difference in density between nitrogen or nitrogen foam and polymer, and the more uniform mixing of gas and liquid after passing through the mixing body 200, the gas-liquid mixture will help carry more polymer into the upper oil layer first, thereby achieving a certain profile control effect.

[0061] In the second stage, nitrogen or nitrogen foam is injected into the inner pipe column 100, and surfactant is injected into the injection space 230 at the same time. The injected surfactant reaches the suction chamber 211, is sucked into the mixing chamber 221 and mixed with nitrogen or nitrogen foam, and then injected into the formation 3 through the outlet 241. Since the gas-liquid mixture is more uniform after passing through the mixing body 200, the gas-liquid mixture will help to carry more surfactants to enter the upper oil layer first (due to the large thickness of the oil layer, the conventional chemical flooding injection medium enters the lower oil layer first due to its high density, the lower oil layer is well utilized, and the upper oil layer has more residual oil), and the oil washing effect of the surfactant is brought into play, thereby improving the utilization of the oil layer.

[0062] In the third stage, through the profile adjustment in the first stage and the potential tapping of the upper oil layer in the second stage, in the final stage, the surfactant is injected into the inner pipe string 100, and the polymer is injected into the injection space 230 at the same time. The injected polymer reaches the suction chamber 211, is sucked into the mixing chamber 221 and mixed with the surfactant, and then injected into the formation 3 through the outlet 241. Compared with the previous method of injecting polymer and surfactant at the wellhead at the same time, this method can improve the mixing uniformity of the two media, thereby better improving the chemical flooding effect.

[0063] The present application provides a mixing injection device 1. When the first medium flows through the throttling portion 2111, the speed increases and the pressure decreases, forming a low-pressure area, thereby generating suction to suck the second medium in the injection space 230 into the suction chamber 211 through the suction channel 2112, and then mix with the first medium in the mixing chamber 221 and enter the formation 3 through the outlet 241. Since the outlet 241 is connected to the formation 3, that is, the first medium and the second medium reach the formation 3 immediately after mixing, thereby improving the medium mixing effect. To a certain extent, it improves the technical problem that due to the long distance between the wellhead and the formation 3, the mixed medium may be stratified due to density differences in the process of entering the formation 3 from the wellhead, resulting in poor mixing effect and failure to achieve the effect of mixed injection.

[0064] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0065] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A mixing injection device, characterized in that: include: An inner pipe string is arranged underground, and the inner pipe string is used to inject a first medium; A mixing body connected to the lower part of the inner pipe column, the mixing body having a suction chamber and a mixing chamber connected in sequence from top to bottom, the suction chamber having a throttling portion, the inner wall of the throttling portion being provided with a suction channel, one end of the suction channel being connected to the injection space, and the other end being connected to the suction chamber, an outlet being provided at the lower part of the mixing chamber, and the outlet being provided close to the connecting groove; wherein the connecting groove is provided on the well wall and connected to the formation; An injection space is provided outside the inner pipe column and the suction chamber, and the injection space is used to inject a second medium; When the first medium flows through the throttling portion, the second medium in the injection space can be sucked into the suction chamber through the suction channel, and then mixed with the first medium in the mixing chamber and enter the formation through the outlet and the connecting groove.

2. The mixing injection device according to claim 1, characterized in that: The mixing body includes a first shell, a second shell and an injection sleeve which are connected in sequence from top to bottom. The suction chamber is arranged in the first shell, the mixing chamber is arranged in the second shell, and the outlet is arranged at the lower end of the injection sleeve.

3. The mixing injection device according to claim 2, characterized in that: The inner diameter of the lower end of the injection sleeve is greater than the inner diameter of the upper end.

4. The mixing injection device according to claim 1, characterized in that: A plurality of the suction passages are provided at intervals along the circumference of the throttle portion.

5. The mixing injection device according to claim 1, characterized in that: The suction channel is arranged to be inclined downward relative to the center line of the suction chamber.

6. The mixing injection device according to any one of claims 1 to 5, characterized in that: The injection space is formed between the inner pipe column and the outer wall of the suction cavity and the well wall.

7. The mixing injection device according to any one of claims 1 to 5, characterized in that: The device further comprises an outer tube column, which is arranged at intervals outside the inner tube column and the suction chamber, and the injection space is formed between the outer wall of the inner tube column and the suction chamber and the inner wall of the outer tube column.

8. The mixing injection device according to claim 7, characterized in that: A sealing member is provided on the peripheral side of the mixing body, and the sealing member is arranged at the lower part of the suction chamber, and the sealing member seals the lower part of the injection space.

9. The mixing injection device according to claim 7, characterized in that: A packer is arranged between the outer pipe string and the well wall.

10. The mixing injection device according to claim 1, characterized in that: The first medium is steam, and the second medium is nitrogen or nitrogen foam.

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