Horizontal well steam flooding section-selecting steam injection device

Abstract

The utility model provides a horizontal well steam flooding section-selecting steam injection device which comprises a steam injection pipe column which is sequentially provided with a deep well safety valve, a thermal recovery packer, a hydraulic control valve set, a section steam injection packer and an injection allocation valve, and the hydraulic control valve set, the section steam injection packer and the injection allocation valve are sequentially connected through an oil pipe. The sand control pipe column comprises a sand control packer, a first screen pipe section, a first subsection packer, a working barrel and a second screen pipe section. The steam injection tubular column is arranged in the sleeve and the sand prevention tubular column, and is positioned and sealed with the working barrel through the segmented steam injection packer; the first subsection packer is matched and sealed with the sleeve, forms a first sand prevention section with the sand prevention packer and the first screen pipe section, and forms a second sand prevention section with the second screen pipe section; the hydraulic control valve set is arranged in the first screen pipe section, the first screen pipe section is arranged in the first sand control section, the injection allocation valve is arranged in the second screen pipe section, and a thermal recovery exhaust valve is arranged on the thermal recovery packer. The section-selecting steam injection device can provide section-selecting steam injection under the condition of a steam-driven horizontal well.

Description

Technical Field

[0001] The utility model belongs to the technical field of oil and gas field development, and in particular relates to a horizontal well steam drive section-selective steam injection device. Background Art

[0002] my country has abundant reserves of offshore crude oil, and the production of offshore oil and gas has continued to grow in recent years. Since heavy oil accounts for about 70% of the proven crude oil reserves, thermal recovery of heavy oil has become an important direction for the development of offshore heavy oil fields. Most offshore heavy oil reservoirs are developed and put into production by steam huff and puff. This type of development method has a low recovery rate, and as the huff and puff cycle increases, the oil production rate, single well capacity, and cycle production gradually decrease, which is likely to cause an overall deterioration in economic benefits.

[0003] However, in order to improve the recovery rate of the overall utilized block, it is necessary to switch to steam drive development in a timely manner. Since horizontal wells can increase the oil leakage area, increase recoverable reserves, and reduce the cost per ton of oil, the number of horizontal wells in offshore heavy oil thermal recovery platforms currently accounts for more than 90%. However, due to the influence of the heterogeneity of the reservoir and the length of the horizontal section, there is a common contradiction of uneven utilization of the horizontal section reservoir when steam is injected into horizontal wells, which seriously restricts the improvement of horizontal well production capacity. The existing segmented steam injection pipe strings in onshore oil fields either cannot meet the requirements of safety control and wellbore insulation of offshore thermal recovery wells, or cannot meet the safety requirements of offshore steam drive horizontal well string lifting and lowering.

[0004] Therefore, technicians in this field urgently need to find a horizontal well steam drive section steam injection device to solve all or part of the above technical problems. Utility Model Content

[0005] In order to solve all or part of the above problems, the utility model aims to provide a horizontal well steam drive section steam injection device, which can provide a solution for section steam injection and wellbore insulation under steam drive horizontal well conditions.

[0006] The present application provides a horizontal well steam drive section-selective steam injection device, comprising: a steam injection string, on which a deep well safety valve, a thermal recovery packer are arranged in sequence from top to bottom, and a hydraulic control valve group, a sectioned steam injection packer, and an injection valve are connected in sequence through an oil pipe; and a sand control string, which comprises, from top to bottom, a sand control packer arranged inside a casing, a first screen pipe section, a first sectioned packer, a working cylinder, and a second screen pipe section. Among them, the steam injection string is arranged in the casing and the sand control string, and is positioned and sealed with the working cylinder through the segmented steam injection sealer; the first segmented sealer is sealed with the casing, and forms a first sand control section with the sand control sealer and the first screen section, and forms a second sand control section with the second screen section, the first sand control section and the second sand control section correspond to the first segment target layer and the second segment target layer respectively; the hydraulic control valve group is arranged in the first screen section, the first screen section is arranged in the first sand control section, and the injection valve is arranged in the second screen section; the hydraulic control valve group is arranged to be able to execute the opening and closing of the internal channel of the oil pipe and the opening and closing with the casing annulus, and the injection valve is constructed to be able to communicate with the casing annulus; a thermal recovery exhaust valve is arranged on the thermal recovery sealer.

[0007] In some embodiments, the hydraulically controlled valve group includes a hydraulically controlled sleeve and a hydraulically controlled switch which are arranged in sequence, wherein the hydraulically controlled sleeve is constructed as a hydraulically controlled valve which can connect the oil pipe with the casing annulus.

[0008] In some embodiments, the hydraulically controlled switch is configured as a hydraulically controlled valve capable of controlling the opening and closing of an internal passage of the oil pipe, so as to control the flow of fluid in the oil pipe.

[0009] In some embodiments, a hydraulic control pipeline is also included, and the hydraulic control pipeline is electrically connected to the hydraulic control sleeve and the hydraulic control switch to control the start and end of the hydraulic control sleeve and the hydraulic control switch.

[0010] In some embodiments, the thermal recovery packer cooperates with the casing seal to isolate the annulus between the tubing and the casing.

[0011] In some embodiments, a hydraulic control pipeline is also included, and the hydraulic control pipeline is electrically connected to the thermal recovery exhaust valve to control the opening and closing of the casing annulus by controlling the thermal recovery packer.

[0012] In some embodiments, a hydraulic control pipeline is also included, and the hydraulic control pipeline is electrically connected to the deep well safety valve to control the opening and closing of the channel in the oil pipe.

[0013] In some embodiments, the oil pipe of the steam injection string includes an insulated oil pipe and a connecting oil pipe connected to the insulated oil pipe, the deep well safety valve and the thermal recovery packer are arranged on the insulated oil pipe, the hydraulic control valve group, the segmented steam injection packer, and the injection valve are connected to the connecting oil pipe, wherein the steam injection string also includes an insulating compensator for connecting the insulated oil pipe and the connecting oil pipe.

[0014] In some embodiments, the steam injection string further comprises a heat-sensitive packer, which is sealingly matched to connect the oil pipe and the casing annulus.

[0015] In some embodiments, the steam injection string includes a plurality of hydraulically controlled control valve groups, a plurality of segmented steam injection packers, and a plurality of injection valves. The horizontal well steam drive segmented steam injection device includes a plurality of sand control strings. A plurality of hydraulically controlled control valve groups, a plurality of segmented steam injection packers, and a plurality of injection valves are respectively grouped and arranged in different sand control strings.

[0016] The utility model provides a horizontal well steam drive segmented steam injection device with the following advantages: 1) different segments are isolated by the cooperation of segmented steam injection packers and the sand control pipe column working tube, so that the resistance is small under the steam drive horizontal well condition, and it is convenient to lift and lower; 2) through the arrangement of the segmented packers of the sand control pipe column and the segmented steam injection packers of the steam injection pipe column, the effect of effective isolation inside and outside the pipe is achieved, so that segmented steam injection can be realized and the "heel and toe effect" can be effectively reduced; 3) the steam injection pipe column reasonably combines tools such as thermal recovery packers, deep well safety valves, hydraulic control valve groups and injection valves, so as to realize the organic combination of segmented steam injection and wellbore insulation and wellbore safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural schematic diagram of a horizontal well steam flooding section-selective steam injection device according to an embodiment of the utility model;

[0018] Figure 2 Inject heat into the first segmented target layer of the horizontal well steam drive segmented steam injection device according to the embodiment of the utility model;

[0019] Figure 3 This is a schematic diagram of heat injection into the second segmented target layer of the horizontal well steam flooding segmented steam injection device according to an embodiment of the utility model;

[0020] Figure 4 This is a schematic diagram of simultaneously injecting heat into the first segmented target layer and the second segmented target layer of the horizontal well steam drive segmented steam injection device according to an embodiment of the utility model. DETAILED DESCRIPTION

[0021] In order to better understand the purpose, structure and function of the utility model, a horizontal well steam drive section steam injection device of the utility model is further described in detail below in conjunction with the accompanying drawings.

[0022] Figure 1 The structure of the steam injection device 100 for horizontal well steam flooding selected section according to the embodiment of the utility model is shown. Figure 1As shown, the horizontal well steam drive section steam injection device 100 includes: a steam injection string, on which a deep well safety valve 3, a thermal recovery packer 5, and a hydraulic control valve group, a segmented steam injection packer 13, and an injection valve 16 are sequentially connected through oil pipes from top to bottom; and a sand control string, which includes a sand control packer 8, a first screen section 9, a first segmented packer 11, a working cylinder 12, and a second screen section 14 arranged inside the casing 21 from top to bottom. Among them, the steam injection string is arranged in the casing 21 and the sand control string, and is positioned and sealed with the working cylinder 12 through the segmented steam injection sealer 13; the first segmented sealer 11 cooperates with the casing 21 to seal, and forms a first sand control section 10 with the sand control sealer 8 and the first screen section 9, and forms a second sand control section 15 with the second screen section 14, the first sand control section 10 and the second sand control section 15 correspond to the first segment target layer 20 and the second segment target layer 17 respectively; the hydraulic control valve group is arranged in the first screen section 9, the first screen section 9 is arranged in the first sand control section 10, and the injection valve 16 is arranged in the second screen section 14; the hydraulic control valve group is arranged to be able to execute the opening and closing of the internal channel of the oil pipe and the opening and closing of the annulus of the casing 21, and the injection valve 16 is constructed to be able to communicate with the annulus of the casing 21; a thermal recovery exhaust valve 4 is arranged on the thermal recovery sealer 5.

[0023] The horizontal well steam flooding section steam injection device 100 of the utility model embodiment can realize the heavy oil thermal recovery horizontal well steam flooding section steam injection, which can be implemented as follows: heel steam injection, toe stop injection (such as Figure 2 as shown); add steam to the tip of the foot and stop at the heel (as shown Figure 3 As shown); inject steam at the toes and heels at the same time (as shown Figure 4 As shown); three working conditions. In combination with the horizontal well steam drive segmented steam injection device 100 of the embodiment of the utility model, it can be understood that the heel is located at the first segment target layer 20, and the toe is located at the second segment target layer 17. In this application, the deep well safety valve 3 is a high temperature resistant deep well safety valve, and the thermal recovery packer 5 is a high temperature resistant thermal recovery packer. In this application, the injection valve 16 is a critical injection valve.

[0024] When the horizontal well steam drive section steam injection device 100 of the utility model is used, it can open and close the internal channel of the oil pipe and the annulus of the casing 21 through the control of the hydraulic control valve group. Figure 2 As shown, when the internal channel of the oil pipe is closed by the hydraulic control valve group, the hydraulic control valve group is connected with the annulus of the casing 21, and the fluid can enter the first screen pipe section 9 through the hydraulic control valve group, thereby implementing the working conditions of heel steam injection and toe stop injection; combined with Figure 3As shown, when the internal channel of the oil pipe is connected through the hydraulic control valve group, the hydraulic control valve group and the annulus of the casing 21 are closed, and the fluid can enter the injection valve 16 through the oil pipe. The injection valve 16 is connected with the annulus of the casing 21, and the fluid can enter the second screen pipe section 14 through the injection valve 16, thereby implementing the working conditions of toe steam injection and heel stop injection; combined with Figure 4 As shown, the internal channel of the oil pipe is connected through the hydraulic control valve group. When the hydraulic control valve group is connected with the annulus of the casing 21, the fluid can enter the first screen pipe section 9 through the hydraulic control valve group, and at the same time, enter the injection valve 16 through the oil pipe, and then enter the second screen pipe section 14 through the injection valve 16, thereby implementing the working condition of simultaneous steam injection at the toe and heel.

[0025] Through the above-mentioned arrangement, the horizontal well steam drive segmented steam injection device 100 of the utility model embodiment has the following advantages: 1) the segmented steam injection packer 13 cooperates with the sand control pipe column working tube 12 to isolate different sections, and the resistance is small under the steam drive horizontal well condition, which is convenient for lifting and lowering; 2) through the arrangement of the segmented steam injection packer 13 of the sand control pipe column and the segmented steam injection packer 13 of the steam injection pipe column, the effect of effective isolation inside and outside the pipe is achieved, so that segmented steam injection can be realized, and the "heel-toe effect" can be effectively reduced; 3) the steam injection pipe column reasonably combines the thermal recovery packer 5, the deep well safety valve 3, the hydraulic control valve group and the injection valve 16 and other tools, thereby realizing the organic combination of segmented steam injection and wellbore insulation and wellbore safety.

[0026] In some embodiments, the hydraulic control valve group may include a hydraulic control sleeve 19 and a hydraulic control switch 18 arranged in sequence. The hydraulic control sleeve 19 may be configured as a hydraulic control valve that can connect the oil pipe with the annulus of the casing 21.

[0027] In some embodiments, the hydraulically controlled switch 18 may be configured as a hydraulically controlled valve capable of controlling the opening and closing of an internal passage of the oil pipe, so as to control the flow of the fluid in the oil pipe.

[0028] In some embodiments, the horizontal well steam drive section steam injection device 100 may also include a hydraulic control pipeline 2, which is electrically connected to the hydraulic control sleeve 19 and the hydraulic control switch 18 to control the start and end of the hydraulic control sleeve 19 and the hydraulic control switch 18.

[0029] In some embodiments, the thermal recovery packer 5 is sealed and matched with the casing 21 to isolate the annulus between the oil pipe and the casing 21 .

[0030] In some embodiments, the horizontal well steam drive section injection device 100 may also include a hydraulic control pipeline 2, which is electrically connected to the thermal recovery exhaust valve 4 to control the opening and closing of the annulus of the casing 21 by controlling the thermal recovery packer 5.

[0031] In some embodiments, the horizontal well steam drive section steam injection device 100 may further include a hydraulic control pipeline 2, which is electrically connected to the deep well safety valve 3 to control the opening and closing of the channel in the oil pipe.

[0032] In some embodiments, the oil pipe of the steam injection string may include an insulated oil pipe 1 and a connecting oil pipe 22 connected to the insulated oil pipe 1, the deep well safety valve 3 and the thermal recovery packer 5 are arranged on the insulated oil pipe 1, the hydraulic control valve group, the segmented steam injection packer 13, and the injection valve 16 are connected to the connecting oil pipe 22, wherein the steam injection string also includes an insulating compensator 6 for connecting the insulated oil pipe 1 and the connecting oil pipe 22.

[0033] In some embodiments, the steam injection string may further include a heat-sensitive packer 7 , which is sealed and matched to the annulus connecting the oil pipe 22 and the casing 21 .

[0034] In combination with the above, according to the embodiment of the utility model, the horizontal well steam flooding section steam injection device 100 implements three working conditions of heel steam injection, toe stop injection, toe steam injection, foot stop injection, toe and foot and toe steam injection at the same time, as shown in the accompanying drawings:

[0035] like Figure 2 As shown, it is the working condition of heel steam injection and toe stop injection. Specifically, after high-temperature steam is injected into the wellbore, it passes through the insulated oil pipe 1, deep well safety valve 3, thermal recovery packer 5, insulated compensator 6, connecting oil pipe 22 in sequence, and finally passes through the high-temperature resistant hydraulic control sliding sleeve 19 and enters the first screen section 9. Then, it passes through the first sand control section 10 and finally enters the first segment target layer 20.

[0036] Due to the sealing effect of the segmented steam injection packer 13 and the working cylinder 12, the first segmented packer 11 and the casing 21, the first screen pipe section 9 and the second screen pipe section 14 are in a sealed state inside and outside the pipe, so there is no disturbance between the high temperature resistant hydraulic control sleeve 19 and the hot fluid flowing out of the injection valve 16. Under the control of the hydraulic control pipeline 2, the high temperature resistant hydraulic control sleeve 19 is opened and the high temperature resistant hydraulic control switch 18 is closed, so as to control the steam in the oil pipe to be injected only into the first segmented target layer 20 to meet the steam injection demand of the layer reservoir.

[0037] like Figure 3 As shown, it is a condition of steam injection at the tip and stop injection at the root. Specifically, after high-temperature steam is injected into the wellbore, it passes through the insulated oil pipe 1, deep well safety valve 3, thermal recovery packer 5, insulated compensator 6, connecting oil pipe 22, high-temperature resistant hydraulic control sliding sleeve 19, high-temperature resistant hydraulic control switch 18 in sequence, and finally enters the second screen section 14 through the injection valve 16. Then, it passes through the second sand control section 15 and finally enters the second segment target layer 17.

[0038] Due to the sealing effect of the segmented steam injection packer 13 and the working cylinder 12, the first segmented packer 11 and the casing 21, the first screen pipe section 9 and the second screen pipe section 14 are in a sealed state inside and outside the pipe, so there is no disturbance between the high temperature resistant hydraulic control sleeve 19 and the hot fluid flowing out of the injection valve 16. Under the control of the hydraulic control pipeline 2, the high temperature resistant hydraulic control sleeve 19 is closed and the high temperature resistant hydraulic control switch 18 is opened, so as to control the steam in the oil pipe to be injected only into the second segmented target layer 17 to meet the steam injection demand of the layer reservoir.

[0039] like Figure 4 As shown, it is a condition of simultaneous steam injection at the toe and the heel. Specifically, after high-temperature steam is injected into the wellbore, it passes through the insulated oil pipe 1, deep well safety valve 3, thermal recovery packer 5, insulated compensator 6, connecting oil pipe 22, high-temperature resistant hydraulic control switch 18 in sequence, and finally passes through the high-temperature resistant hydraulic control sliding sleeve 19 and the injection valve 16 to enter the first screen pipe section 9 and the second screen pipe section 14. Then, it passes through the first sand control section 10 and the second sand control section 15, and finally enters the first segment target layer 20 and the second segment target layer 17.

[0040] Due to the sealing effect of the segmented steam injection packer 13 and the working cylinder 12, the first segmented packer 11 and the casing 21, the first screen tube section 9 and the second screen tube section 14 are in a sealed state inside and outside the pipe, so there is no disturbance between the high temperature resistant hydraulic control sleeve 19 and the hot fluid flowing out of the injection valve 16. Under the control of the hydraulic control pipeline 2, the high temperature resistant hydraulic control sleeve 19 is opened, and the high temperature resistant hydraulic control switch 18 is opened, so that the steam in the oil pipe can be injected into the first segmented target layer 20 and the second segmented target layer 17 to meet the steam injection demand of the reservoir in the layer.

[0041] In some embodiments, the steam injection string may include a plurality of hydraulic control valve groups, a plurality of segmented steam injection packers 13, and a plurality of injection valves 16. The horizontal well steam drive segmented steam injection device 100 includes a plurality of sand control strings. The plurality of hydraulic control valve groups, a plurality of segmented steam injection packers 13, and a plurality of injection valves 16 are respectively arranged in groups in different sand control strings. Through this arrangement, the horizontal well steam drive segmented steam injection device 100 of the utility model embodiment can be applied to the reservoir steam injection requirements of various segmented target layers, so as to improve the practicality of the horizontal well steam drive segmented steam injection device 100 of the utility model embodiment.

[0042] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by technicians in the field to which the utility model belongs.

[0043] In the description of the present application, it should be understood that the terms “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “axial”, “radial”, “circumferential”, etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0044] In addition, the terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present utility model, the meaning of "plurality" is more than two, unless otherwise clearly and specifically limited.

[0045] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it 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. For ordinary technicians in this field, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it; although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the utility model, and they should all be included in the scope of the claims and description of the utility model. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The utility model is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A steam injection device for horizontal well steam flooding, characterized in that: include: The steam injection string is provided with a deep well safety valve, a thermal recovery packer, and a hydraulic control valve group, a segmented steam injection packer, and an injection valve connected in sequence through an oil pipe from top to bottom; and, A sand control pipe string, which includes, from top to bottom, a sand control packer arranged inside the casing, a first screen section, a first segmented packer, a mandrel, and a second screen section; Wherein, the steam injection string is arranged in the casing and the sand control string, and is positioned and sealed with the working cylinder through the segmented steam injection packer; the first segmented packer is sealed with the casing, and forms a first sand control section with the sand control packer and the first screen section, and forms a second sand control section with the second screen section, the first sand control section and the second sand control section correspond to the first segment target layer and the second segment target layer respectively; the hydraulic control valve group is arranged in the first screen section, the first screen section is arranged in the first sand control section, and the injection valve is arranged in the second screen section; the hydraulic control valve group is arranged to be able to execute the opening and closing of the internal channel of the oil pipe and the opening and closing with the casing annulus, and the injection valve is constructed to be able to communicate with the casing annulus; a thermal recovery exhaust valve is arranged on the thermal recovery packer.

2. The horizontal well steam flooding section-selected steam injection device according to claim 1, characterized in that: The hydraulic control valve group comprises a hydraulic control sleeve and a hydraulic control switch which are arranged in sequence, wherein the hydraulic control sleeve is constructed as a hydraulic control valve which can connect the oil pipe with the casing annulus.

3. The horizontal well steam flooding section-selected steam injection device according to claim 2, characterized in that: The hydraulically controlled switch is constructed as a hydraulically controlled valve capable of controlling the opening and closing of an internal passage of the oil pipe, so as to control the flow of the fluid in the oil pipe.

4. The horizontal well steam flooding section-selected steam injection device according to claim 3, characterized in that: It also includes a hydraulic control pipeline, which is electrically connected to the hydraulic control sleeve and the hydraulic control switch to control the start and end of the hydraulic control sleeve and the hydraulic control switch.

5. The horizontal well steam flooding section-selective steam injection device according to any one of claims 1 to 4, characterized in that: The thermal recovery packer is in sealing cooperation with the casing to seal the annulus between the oil pipe and the casing.

6. The horizontal well steam flooding section-selected steam injection device according to claim 5, characterized in that: It also includes a hydraulic control pipeline, which is electrically connected to the thermal recovery exhaust valve to control the opening and closing of the casing annulus by controlling the thermal recovery packer.

7. The horizontal well steam flooding section-selected steam injection device according to claim 6, characterized in that: It also includes a hydraulic control pipeline, which is electrically connected to the deep well safety valve to control the opening and closing of the channel in the oil pipe.

8. The horizontal well steam flooding section-selective steam injection device according to any one of claims 1 to 4, characterized in that: The oil pipe of the steam injection string includes an insulated oil pipe and a connecting oil pipe connected to the insulated oil pipe. The deep well safety valve and the thermal recovery packer are arranged on the insulated oil pipe. The hydraulic control valve group, the segmented steam injection packer, and the injection valve are connected to the connecting oil pipe. The steam injection string also includes an insulating compensator for connecting the insulated oil pipe and the connecting oil pipe.

9. The horizontal well steam flooding section-selected steam injection device according to claim 8, characterized in that: The steam injection string also includes a heat-sensitive packer, which is sealed and matched with the connecting oil pipe and the casing annulus.

10. The horizontal well steam flooding section-selective steam injection device according to any one of claims 1 to 4, characterized in that: The steam injection string includes a plurality of the hydraulically controlled control valve groups, a plurality of the segmented steam injection packers, and a plurality of the injection valves. The horizontal well steam drive segmented steam injection device includes a plurality of the sand control strings. The plurality of the hydraulically controlled control valve groups, the plurality of the segmented steam injection packers, and the injection valves are respectively arranged in groups in different sand control strings.

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