Adjustable zonal injection and production string for offshore thermal recovery wells and methods of use

Abstract

The application relates to a recoverable adjustable layered injection-production pipe column for offshore thermal recovery wells and a use method thereof, wherein the injection-production pipe column comprises a plurality of pipe column assemblies connected in sequence from top to bottom, packers, a tail-end tubing and a bottom plug; each pipe column assembly comprises a first tubing, a prefabricated working barrel, an adjustable injection-production core, a second tubing and a reverse circulation production valve; the upper end of the prefabricated working barrel is connected with the first tubing, and the lower end thereof is connected with the upper end of the second tubing; the lower end of the second tubing is connected with the reverse circulation production valve; the adjustable injection-production core is arranged in the prefabricated working barrel; the first tubing in each pipe column assembly is connected with a packer; the first tubing of the uppermost pipe column assembly is connected with a wellhead of a wellbore; the bottom of the reverse circulation production valve in the lowermost pipe column assembly is connected with the tail-end tubing, and the bottom plug is arranged at the bottom of the tail-end tubing; wherein the prefabricated working barrel and the adjustable injection-production core cooperate to guide part of steam injected from the wellhead into a stratum.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploitation, in particular to a recoverable adjustable separate layer injection and production pipe column for offshore thermal recovery well and a use method thereof. BACKGROUND

[0002] Steam huff and puff of heavy oil is the main technology for exploiting heavy oil in offshore thermal recovery well at present, but due to different characteristics and classifications of each heavy oil reservoir, different steam injection amounts need to be controlled through steam distribution device in the specific exploitation process. At present, general steam injection is mainly used for steam huff and puff development in offshore. Generally, the operation mode of separating injection heat pipe column and production pipe column is adopted: before injecting steam into the heavy oil well, the platform workover operation is carried out to replace the injection heat pipe column, and after the soaking and blowout are completed, the workover operation is carried out again to replace the production pipe column for production.

[0003] However, the existing steam huff and puff exploitation method can realize the development of offshore heavy oil field, but there are the following problems:

[0004] (1) The existing steam huff and puff process can only realize general steam huff and puff development, and for multi-layer heavy oil fields with large interlayer physical property difference, the steam absorption amount of main oil layer is too large, and thin and poor layers cannot be effectively developed, which affects the ultimate recovery of the oil field.

[0005] (2) For multi-layer heavy oil fields with large interlayer physical property difference, the existing steam huff and puff process can only adopt single-layer steam huff and puff, and the development is carried out in the mode of layer-by-layer upward return or layer-by-layer downward return, which needs to carry out multiple pipe column replacement operations during the development process, resulting in low development efficiency, long development period, high construction cost and other disadvantages. SUMMARY

[0006] In view of the above problems, the present application aims to provide a recoverable adjustable separate layer injection and production pipe column for offshore thermal recovery well and a use method thereof, which can realize multiple rounds of production without pipe column replacement in steam huff and puff, and realize the integration of steam injection, soaking and oil production.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The offshore thermal recovery well recovery adjustable layered injection-production pipe column is arranged in a wellbore, comprising a plurality of sequentially connected pipe column assemblies from top to bottom, packers, a terminal tubing and a bottom plug; each pipe column assembly comprises a first tubing, a prefabricated working barrel, an adjustable injection core, a second tubing and a reverse circulation production valve; the upper end of the prefabricated working barrel is connected with the first tubing, and the lower end thereof is connected with the upper end of the second tubing; the lower end of the second tubing is connected with the reverse circulation production valve; the adjustable injection core is arranged in the prefabricated working barrel; the first tubing in each pipe column assembly is connected with a packer; the first tubing of the uppermost pipe column assembly is connected with the wellhead of the wellbore; the bottom of the reverse circulation production valve in the lowermost pipe column assembly is connected with the terminal tubing, and the bottom plug arranged at the bottom of the terminal tubing is blocked; wherein the prefabricated working barrel and the adjustable injection core cooperate to guide a part of steam injected from the wellhead to the formation.

[0009] Preferably, the prefabricated working barrel comprises a first upper joint, an outer sleeve, a central pipe, a valve seat, a spring and a first lower joint; the lower part of the first upper joint is connected with the upper part of the outer sleeve; the central pipe is sleeved in the whole formed by the first upper joint and the outer sleeve, and the upper part thereof is connected with the lower part of the first upper joint; the central pipe and the outer sleeve define an annular gas flow channel for steam flow; both sides of the central pipe are respectively provided with gas outlets extending into the gas flow channel and communicating with the gas flow channel; the inner wall of the central pipe is provided with an upper sealing surface and a lower sealing surface, and the upper sealing surface and the lower sealing surface are respectively arranged on both sides of the gas outlet; the valve seat is sleeved outside the central pipe, and the upper part of the valve seat is provided with a first sealing surface; the lower part of the outer sleeve is provided with a second sealing surface, and the first sealing surface and the second sealing surface are in contact; the upper part of the first lower joint is connected with the lower part of the central pipe; the spring is sleeved outside the central pipe and located between the valve seat and the first lower joint.

[0010] Preferably, the top of the central pipe is provided with a limiting step for cooperating with a positioning step on the adjustable injection core to assemble and position the prefabricated working barrel and the adjustable injection core.

[0011] Preferably, the prefabricated working barrel further comprises a gasket sleeved outside the central pipe and located between the spring and the first lower joint.

[0012] The offshore thermal recovery well recovery adjustable layered injection and production pipe column, preferably, the adjustable injection core comprises a second upper joint, an injection core body, an upper sealing ring, a lower sealing ring and a second lower joint; the lower inner wall of the second upper joint is connected with the upper part of the injection core body; the upper sealing ring is sleeved outside the injection core body and located between the lower end surface of the second upper joint and the first stepped surface of the injection core body, and the second upper joint and the injection core body axially compress the upper sealing ring; the upper inner wall of the second lower joint is connected with the lower part of the injection core body; the lower sealing ring is sleeved outside the injection core body and located between the upper end surface of the second lower joint and the second stepped surface of the injection core body, and the second lower joint and the injection core body axially compress the lower sealing ring; the two sides of the injection core body are respectively provided with throttle nozzles.

[0013] The offshore thermal recovery well recovery adjustable layered injection and production pipe column, preferably, a positioning step is arranged on the second upper joint, the positioning step abuts against the limiting step of the prefabricated working barrel, so that the prefabricated working barrel and the adjustable injection core are positioned.

[0014] The offshore thermal recovery well recovery adjustable layered injection and production pipe column, preferably, further comprises a fishing tool and a steel wire; the fishing tool is hung in the first oil pipe of the uppermost layer by the steel wire and can enter the adjustable injection core from the first oil pipe, and the fishing tool is used for launching or fishing the adjustable injection core to replace the adjustable injection core.

[0015] The use method of the offshore thermal recovery well recovery adjustable layered injection and production pipe column, comprising the following steps:

[0016] The adjustable injection core in each pipe column assembly is matched with a throttle nozzle, the adjustable injection core is prefabricated in the prefabricated working barrel on the ground, and the whole injection and production pipe column is connected and then lowered into the wellbore.

[0017] The well mouth is connected with a steam injection device, steam injection is started, the upper sealing ring and the lower sealing ring of the adjustable injection core are sealed with the upper sealing surface and the lower sealing surface of the prefabricated working barrel respectively when the steam passes through the prefabricated working barrel and the adjustable injection core of the uppermost layer, the first sealing surface and the second sealing surface of the prefabricated working barrel are sealed, the injected steam is divided into two parts, one part passes through the throttle nozzles of the adjustable injection core of the uppermost layer and the gas outlet of the prefabricated working barrel of the uppermost layer to push away the valve seat and then enters the formation, and the other part is injected downward along the second oil pipe to the lower pipe column assembly, the steam flowing downward enters the corresponding formation through the corresponding throttle nozzles, and the steam is injected in layers.

[0018] The use method of the offshore thermal recovery well recovery adjustable layered injection and production pipe column, preferably, further comprises the following steps:

[0019] When the injection is stopped, the valve seat of each prefabricated working cylinder is reset under the push of the spring, the first sealing surface and the second sealing surface are in close contact again, forming a sealing structure, at this time, the soak operation is carried out;

[0020] When the soak operation is over and the blowout is started, the formation pressure is higher than the tubing pressure, the first sealing surface and the second sealing surface of each prefabricated working cylinder are still in close contact, maintaining the sealing structure, the oil and gas fluid of the formation enters the inside of the tubing through the reverse circulation production valve of each layer, and then the production operation is realized.

[0021] The present application has the following advantages due to the above technical scheme:

[0022] (1) The present application can realize multi-cycle production without replacing the string in steam stimulation, realizing the integration of steam injection-soak-well production.

[0023] (2) The present application can realize simultaneous development of multi-layer heavy oil field by layering steam stimulation, and can adjust the steam injection amount of each layer by wire fishing.

[0024] (3) The present application can adjust the injection core, which can be conveyed into the wellbore by wire operation and docked with the corresponding prefabricated working cylinder to control the injection amount of each layer.

[0025] (4) The present application can install a throttle nozzle on the adjustable injection core, which can replace various sizes of throttle nozzles according to the geological conditions of different oil layers to meet the injection requirements. BRIEF DESCRIPTION OF DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. Throughout the drawings, the same reference numerals are used for the same components. In the drawings:

[0027] Figure 1 is a schematic diagram of the overall structure of the injection and production string of the present application;

[0028] Figure 2 is Figure 1 a schematic diagram of the specific structure of the prefabricated working cylinder in the present application;

[0029] Figure 3 is Figure 1 a schematic diagram of the specific structure of the adjustable injection core in the present application;

[0030] Figure 4 is a schematic diagram of the structure of the injection and production string in the steam injection state;

[0031] Figure 5 is a schematic diagram of the assembly structure of the prefabricated working cylinder and the adjustable injection core in the steam injection state;

[0032] Figure 6 is a structural schematic diagram of the injection-production string in the oil production state.

[0033] The various marks in the drawings represent the following:

[0034] 1 - first oil pipe; 2 - prefabricated working barrel; 201 - first upper joint; 202 - outer sleeve; 203 - central pipe; 204 - valve seat; 205 - spring; 206 - first lower joint; 207 - gas flow channel; 208 - gas outlet; 209 - upper sealing surface; 210 - lower sealing surface; 211 - first sealing surface; 212 - second sealing surface; 213 - limiting step; 214 - gasket; 3 - adjustable injection core; 301 - second upper joint; 302 - injection core body; 303 - upper sealing ring; 304 - lower sealing ring; 305 - second lower joint; 306 - throttling gas nozzle; 307 - positioning step; 4 - second oil pipe; 5 - reverse circulation production valve; 6 - packer; 7 - terminal oil pipe; 8 - bottom plug; 9 - fishing tool; 10 - wireline; 11 - wellbore. DETAILED DESCRIPTION

[0035] Exemplary embodiments of the present application will be described in greater detail below with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it is understood that the present application can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0036] The present application provides a recoverable adjustable layered injection-production string for offshore thermal recovery wells and a method for using the same, which includes a plurality of pipe string assemblies connected in sequence from top to bottom, realizes multi-layer steam injection through the cooperation of the prefabricated working barrel and the adjustable injection core in each pipe string assembly, and can realize multi-cycle production without changing the pipe string in steam stimulation, thereby realizing the integration of steam injection, soaking and oil production.

[0037] As Figure 1As shown, the offshore thermal recovery well adjustable layered injection-production pipe column provided by the present application is arranged in the wellbore 11, and comprises a plurality of pipe column assemblies connected in sequence from top to bottom, packers 6, a terminal oil pipe 7 and a bottom plug 8; each of the pipe column assemblies comprises a first oil pipe 1, a prefabricated working cylinder 2, an adjustable injection core 3, a second oil pipe 4 and a reverse circulation production valve 5; the upper end of the prefabricated working cylinder 2 is connected with the first oil pipe 1, and the lower end thereof is connected with the upper end of the second oil pipe 4, and the lower end of the second oil pipe 4 is connected with the reverse circulation production valve 5; the adjustable injection core 3 is arranged in the prefabricated working cylinder 2; the first oil pipe 1 in each of the pipe column assemblies is connected with the packer 6; the first oil pipe 1 of the uppermost pipe column assembly is connected with the wellhead of the wellbore; the bottom of the reverse circulation production valve 5 in the lowermost pipe column assembly is connected with the terminal oil pipe 7, and the bottom plug 8 is arranged at the bottom of the terminal oil pipe 7; wherein the prefabricated working cylinder 2 and the adjustable injection core 3 cooperate to guide a part of steam injected from the wellhead into the formation.

[0038] It should be noted that, Figure 1 The pipe column assemblies in the embodiment shown are three, and are arranged in three layers of formations, wherein the reverse circulation production valve 5 of the first (uppermost) pipe column assembly is connected with the first oil pipe 1 of the second (middle layer) pipe column assembly, and the reverse circulation production valve 5 of the second (middle layer) pipe column assembly is connected with the first oil pipe 1 of the third (lowermost) pipe column assembly; of course, a plurality of pipe column assemblies can be arranged according to the formation and wellbore requirements, and the connection mode is in accordance with the connection rules. Figure 1

[0039] In the above embodiment, preferably, as Figure 2 ​As shown, the prefabricated working cylinder 2 comprises a first upper joint 201, an outer sleeve 202, a central pipe 203, a valve seat 204, a spring 205 and a first lower joint 206; the lower part of the first upper joint 201 is connected with the upper part of the outer sleeve 202, and specifically, a threaded connection can be adopted; the central pipe 203 is sleeved in the whole formed by the first upper joint 201 and the outer sleeve 202, and the upper part thereof is connected with the lower part of the first upper joint 201; the annular space between the central pipe 203 and the outer sleeve 202 defines a gas flow channel 207 for steam flow; two sides of the central pipe 203 are respectively provided with gas outlets 208, which extend into the gas flow channel 207 and communicate with the gas flow channel 207; the inner wall of the central pipe 203 is provided with an upper sealing surface 209 and a lower sealing surface 210, which are respectively arranged on the two sides of the gas outlet 208; the valve seat 204 is sleeved outside the central pipe 203, and the outer wall of the upper part of the valve seat 204 is provided with a first sealing surface 211; the inner wall of the lower part of the outer sleeve 202 is provided with a second sealing surface 212, and the first sealing surface 211 is in contact with the second sealing surface 212; the upper part of the first lower joint 206 is connected with the lower part of the central pipe 203; the spring 205 is sleeved outside the central pipe 203 and located between the valve seat 204 and the first lower joint 206.

[0040] In the above embodiment, preferably, the top of the central pipe 203 is provided with a limiting step 213 for cooperating with a positioning step 307 on the adjustable injection core 3, so as to position the prefabricated working cylinder 2 and the adjustable injection core 3.

[0041] In the above embodiment, preferably, the prefabricated working cylinder 2 further comprises a gasket 214, which is sleeved outside the central pipe 203 and located between the spring 205 and the first lower joint 206.

[0042] In the above embodiment, preferably, as shown, Figure 3 the adjustable injection core 3 comprises a second upper joint 301, an injection core body 302, an upper sealing ring 303, a lower sealing ring 304 and a second lower joint 305; the lower part of the second upper joint 301 is connected with the upper part of the injection core body 302; the upper sealing ring 303 is sleeved outside the injection core body 302 and located between the lower end face of the second upper joint 301 and the first step face of the injection core body 302, and the second upper joint 301 and the injection core body 302 axially press the upper sealing ring 303; the upper part of the second lower joint 305 is connected with the lower part of the injection core body 302; the lower sealing ring 304 is sleeved outside the injection core body 302 and located between the upper end face of the second lower joint 305 and the second step face of the injection core body 302, and the second lower joint 305 and the injection core body 302 axially press the lower sealing ring 304; the two sides of the injection core body 302 are respectively provided with throttle gas nozzles 306.

[0043] In the above embodiment, preferably, the second upper joint 301 is provided with a positioning step 307, which abuts against the limiting step 213 of the prefabricated working barrel 2 to position the prefabricated working barrel 2 and the adjustable injection core 3.

[0044] It should be noted that, as Figure 5 shown, when the prefabricated working barrel 2 and the adjustable injection core are assembled, the positioning step 307 abuts against the limiting step 213, and the throttling air nozzle 306 and the air outlet 208 are arranged correspondingly.

[0045] In the above embodiment, preferably, the application further comprises a fishing tool 9 and a wire 10; the fishing tool 9 is hung in the uppermost first oil pipe 1 by the wire 10 and can enter the adjustable injection core 3 from the first oil pipe, and the fishing tool is used to deliver or fish the adjustable injection core to replace the adjustable injection core.

[0046] It should be noted that the application can realize simultaneous development of multi-layer steam injection in heavy oil fields, and the injection amount of steam in each layer can be adjusted by wire fishing; the adjustable injection core of the application can be conveyed into the wellbore by wire operation and docked with the corresponding prefabricated working barrel to control the injection amount of each layer.

[0047] The application further provides a use method of the adjustable layered injection and production pipe column for offshore thermal recovery wells, which comprises the following steps:

[0048] As Figure 5 shown, a throttling air nozzle 306 is matched and installed in each pipe column assembly, the adjustable injection core 3 is prefabricated in the prefabricated working barrel 2 on the ground, and the whole injection and production pipe column is connected and then lowered into the wellbore 11.

[0049] As Figure 4 and Figure 5 shown, a steam injection device (not shown in the figure) is connected to the wellhead, steam injection is started, when the steam passes through the uppermost prefabricated working barrel 2 and the adjustable injection core 3, the upper sealing ring 303 and the lower sealing ring 304 of the adjustable injection core 3 are respectively sealed with the upper sealing surface 209 and the lower sealing surface 210 of the prefabricated working barrel 2, the first sealing surface 211 and the second sealing surface 212 of the prefabricated working barrel 2 are sealed, the injected steam is divided, a part of the steam passes through the throttling air nozzle 306 of the uppermost adjustable injection core 3 and the air outlet 208 of the uppermost prefabricated working barrel 2 to push away the valve seat 204 and thus enters the formation, and the other part of the steam is injected downward along the second oil pipe 4 to the lower pipe column assembly, the steam flowing downward enters the corresponding formation through the corresponding throttling air nozzle 306, and the steam is injected in layers.

[0050] In the above embodiment, preferably, the following steps are further included:

[0051] When the injection stops, the valve seat 204 of each prefabricated working cylinder 2 is reset under the push of the spring 205, and the first sealing surface 211 and the second sealing surface 212 are in close contact again to form a sealing structure. At this time, the well-clogging operation is carried out.

[0052] like Figure 6 As shown, when the well-sealing operation is completed, the flow is released. During the flow, the formation pressure is higher than the tubing pressure. The first sealing surface 211 and the second sealing surface 212 on each prefabricated working cylinder 2 remain in close contact to maintain the sealing structure. The oil and gas fluid in the formation enters the tubing through the reverse circulation production valve 5 of each layer, thereby realizing the production operation.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some 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 using an adjustable layered injection-production tubing string for offshore thermal recovery wells, wherein the adjustable layered injection-production tubing string for offshore thermal recovery wells is installed in the wellbore and includes several tubing assemblies, packers, end tubing and bottom plugs connected sequentially from top to bottom. Each tubing string assembly includes a first tubing, a prefabricated working barrel, an adjustable core injector, a second tubing, and a reverse circulation production valve. The upper end of the prefabricated working barrel is connected to the first tubing, and its lower end is connected to the upper end of the second tubing. The lower end of the second tubing is connected to the reverse circulation production valve. The adjustable core injector is disposed within the prefabricated working barrel. A packer is connected to the first tubing in each tubing string assembly. The first tubing of the uppermost tubing string assembly is connected to the wellhead of the wellbore. The bottom of the reverse circulation production valve in the lowermost tubing string assembly is connected to the end tubing, and a bottom plug is disposed at the bottom of the end tubing. The prefabricated working cylinder and the adjustable core injection unit work together to guide a portion of the steam injected from the wellhead into the formation; The prefabricated working cylinder includes a first upper connector, an outer sleeve, a central tube, a valve seat, a spring, and a first lower connector. The lower part of the first upper connector is connected to the upper part of the outer sleeve. The central tube is sleeved within the integral formed by the first upper connector and the outer sleeve, and its upper part is connected to the lower part of the first upper connector. An annular airflow channel for steam to flow is defined between the central tube and the outer sleeve. Air outlets are respectively provided on both sides of the central tube, extending into and communicating with the airflow channel. An upper sealing surface and a lower sealing surface are provided on the inner wall of the central tube, respectively located on both sides of the air outlet. The valve seat is sleeved outside the central tube, and a first sealing surface is provided on the upper outer wall of the valve seat. A second sealing surface is provided on the lower inner wall of the outer sleeve, and the first sealing surface contacts the second sealing surface. The upper part of the first lower connector is connected to the lower part of the central tube. The spring is sleeved outside the central tube and located between the valve seat and the first lower connector. The top of the central tube is provided with a limiting step, which is used to cooperate with the positioning step on the adjustable injection core so that the prefabricated working cylinder and the adjustable injection core are assembled and positioned. The adjustable injection core includes a second upper connector, an injection core body, an upper sealing ring, a lower sealing ring, and a second lower connector; the lower inner wall of the second upper connector is connected to the upper part of the injection core body; the upper sealing ring is sleeved on the outside of the injection core body and is located between the lower end face of the second upper connector and the first step surface of the injection core body, and the second upper connector and the injection core body axially press the upper sealing ring together; the upper inner wall of the second lower connector is connected to the lower part of the injection core body; the lower sealing ring is sleeved on the outside of the injection core body and is located between the upper end face of the second lower connector and the second step surface of the injection core body, and the second lower connector and the injection core body axially press the lower sealing ring together; throttling nozzles are respectively provided on both sides of the injection core body; The second upper connector is provided with a positioning step, which abuts against the limiting step of the precast working cylinder to position the precast working cylinder and the adjustable core injection cylinder. The method of use is characterized by comprising the following steps: Install a throttle nozzle on the adjustable injection core in each tubing assembly. Pre-fabricate the adjustable injection core in the prefabricated working cylinder on the ground. After connecting the entire injection and production tubing, lower it into the wellbore. The wellhead is connected to a steam injection device, and steam injection begins. As the steam passes through the uppermost prefabricated working cylinder and the adjustable injection core, the upper and lower sealing rings of the adjustable injection core seal the upper and lower sealing surfaces of the prefabricated working cylinder, respectively. The first and second sealing surfaces of the prefabricated working cylinder are also sealed. The injected steam is split here. One part passes through the throttle nozzle of the uppermost adjustable injection core and the air outlet of the uppermost prefabricated working cylinder to push open the valve seat and enter the formation. The other part is injected downwards along the second tubing into the lower tubing assembly. The downward-flowing steam enters the corresponding formation through the corresponding throttle nozzle of that layer, thus achieving stratified steam injection.

2. The method for using the adjustable stratified injection-production tubing for offshore thermal recovery wells according to claim 1, characterized in that, It also includes the following steps: When the injection stops, the valve seat of each prefabricated working cylinder is pushed back to its original position by the spring, and the first sealing surface and the second sealing surface are in close contact again to form a sealing structure. At this time, the well-closing operation is carried out. After the well-sealing operation is completed, the blowout begins. During the blowout, the formation pressure is higher than the tubing pressure. The first and second sealing surfaces on each prefabricated working tube remain in close contact to maintain the sealing structure. The oil and gas fluids from the formation enter the tubing through the reverse circulation production valve of each layer, thereby realizing the production operation.

3. The method for using the adjustable stratified injection-production tubing for offshore thermal recovery wells according to claim 1, characterized in that, The prefabricated working cylinder also includes a gasket, which is sleeved outside the central tube and located between the spring and the first lower connector.

4. The method for using the adjustable stratified injection-production tubing for offshore thermal recovery wells according to claim 1, characterized in that, The adjustable stratified injection and production tubing for offshore thermal recovery wells also includes a retrieval device and a steel wire. The retrieval device is suspended by the steel wire in the uppermost first oil pipe and can enter the adjustable core through the first oil pipe. The retrieval device is used to deliver or retrieve the adjustable core for replacement.

Images