Completion and fracturing construction system

Abstract

The present invention relates to the technical field of oil and gas exploitation, and particularly to a completion fracturing construction system; it includes a process string, a control unit, a power supply unit and a number of control valves. When conducting the fracturing construction for completion, the process string can be lowered into the well for completion. Each control valve is arranged at intervals along the extension direction of the process string. The control valve is installed on the process string through an installation cylinder, a sliding sleeve and a control module. The control valve is installed on the process string through the installation cylinder. The surface of the installation cylinder is provided with construction holes. The sliding sleeve is slidably connected to the installation cylinder, and the control module is installed on the installation cylinder; since the control unit controls the start and stop of the electrical connection of each control module, the construction holes of each installation cylinder are opened or closed. During the fracturing construction process, the construction holes of the corresponding layers can be controlled to be opened or closed according to the needs of the fracturing construction, and each production layer section can be evenly transformed to improve the comprehensive oil and gas exploitation efficiency of long horizontal wells.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and particularly to a completion fracturing construction system. Background Art

[0002] With the increasingly prominent contradiction between energy supply and demand, the development of oil and gas has moved towards the development of deep shale gas. The deep shale gas reservoirs in China have extremely complex characteristics rare in the world, such as complex structures, developed bedding / microfractures, thin targets, and poor drillability of rocks, resulting in extremely serious unbalanced drainage and production phenomena. Therefore, it is necessary to use a "barefoot packer + step-by-step ball-drop sliding sleeve" fracturing string for completion and fracturing.

[0003] Intelligent completion is an effective means for oil and gas fields to improve recovery efficiency, reduce costs, and enhance development effects, and it is also the development trend of the construction of intelligent oil and gas fields. Large foreign oil service companies have successively developed various forms of intelligent completion systems around aspects such as intelligent separate production, remote control, and layered fracturing. The research in the field of intelligent completion in China is still in its infancy, the research points are relatively scattered, the comprehensive control research on downhole control valves is not in-depth, and only some research has been carried out on downhole dynamic monitoring. Moreover, these technologies do not have mature field applications at present.

[0004] In the commonly used layered fracturing and cementing strings in the existing market, cementing sliding sleeves, ball seat sliding sleeves, and toe-end sliding sleeves are essential tools. In the coiled tubing operation process, due to the reduced diameter structure of the ball seat sliding sleeve, the number of stages of the conventional ball seat sliding sleeve is limited, and the through diameter becomes smaller and smaller. As a result, the existing staged fracturing process string cannot achieve balanced and effective transformation of each production layer section for formations with obvious geological differences. Therefore, it is urgent to promote the intelligent fluid control valve technology and combine it with the ground control technology system (including information transmission and energy supply) to perform repeated selective fracturing construction to extend the production cycle of deep shale reservoirs and improve the comprehensive oil and gas exploitation efficiency of long horizontal wells. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and propose a completion fracturing construction system to solve the technical problem that it is difficult for the fracturing construction process string in the existing technology to evenly transform each production layer section of the formation with obvious geological differences, which affects the comprehensive oil and gas exploitation efficiency of long horizontal wells.

[0006] To achieve the above technical purpose, the technical solution of the present invention provides a completion fracturing construction system, including:

[0007] A process string, which is used for being run into the well for completion;

[0008] A number of control valves, each of the control valves being spaced along the extension direction of the process string on the process string. The control valve includes a mounting cylinder, a sliding sleeve and a control module. The mounting cylinder is installed on the process string. A construction hole is provided on the surface of the mounting cylinder for fracturing construction. The sliding sleeve is slidably connected to the mounting cylinder. The control module is installed on the mounting cylinder and is used to drive the sliding sleeve to slide along the mounting cylinder to open or close the construction hole.

[0009] A control unit, the control unit being electrically connected to each of the control modules for controlling the start and stop of each control module.

[0010] Optionally, a hydraulic chamber is provided inside the mounting cylinder. Both ends of the hydraulic chamber are respectively connected to the sliding sleeve and the control module. The hydraulic chamber is used for filling hydraulic oil. The control module is used to drive the sliding sleeve to slide through the hydraulic oil in the hydraulic chamber.

[0011] Optionally, a first driving chamber and a second driving chamber are provided between the sliding sleeve and the mounting cylinder at intervals along the axial direction of the sliding sleeve. The control module includes a first control component and a second control component. The first control component and the second control component are used to drive the pressure supply liquid in the hydraulic chamber to alternately enter the first driving chamber or the second driving chamber.

[0012] Optionally, the second driving chamber is an annular chamber.

[0013] Optionally, the hydraulic chamber includes a first connection chamber and a second connection chamber. The first connection chamber is communicated with the first driving chamber. The second connection chamber is communicated with the second driving chamber. The first connection chamber and the second connection chamber are respectively connected to the first control component and the second control component.

[0014] Optionally, the second driving chamber is also communicated with the first connection chamber.

[0015] Optionally, the first control component includes a motor, a lead screw and a transmission component. The motor is fixed to the mounting cylinder. One end of the lead screw is slidably connected to the first connection chamber. The other end of the lead screw extends towards the direction of the motor. The transmission component is connected to the lead screw and the motor shaft. The motor is used to drive the lead screw to slide along the first connection chamber through the transmission of the transmission component.

[0016] Optionally, the transmission component includes a lead screw sleeve and a transmission gear. The lead screw sleeve is sleeved on the surface of the lead screw and is threadedly connected to the lead screw. The transmission gear is fixed to the motor shaft and meshes with the lead screw sleeve.

[0017] Optionally, the control valve further includes a limit post and a plunger. The limit post is installed in the installation cylinder and extends into the first drive cavity for restricting the rotation of the sliding sleeve. The plunger is threadedly connected to the installation cylinder and abuts against the limit post.

[0018] Optionally, a connection hole is formed on the surface of the sliding sleeve, and the sliding sleeve can be connected to the construction hole by sliding along the inner wall of the installation cylinder.

[0019] Compared with the prior art, the beneficial effects of the completion fracturing construction system provided by the present invention include: by providing a process string, a control unit and a plurality of control valves, when performing completion fracturing construction, the process string can be lowered into the well completion. Each control valve is arranged at intervals along the extension direction of the process string. The control valve is installed on the process string through the installation cylinder. The surface of the installation cylinder is provided with a construction hole for fracturing construction. The sliding sleeve is slidably connected to the installation cylinder, and the control module is installed in the installation cylinder. The control module can drive the sliding sleeve to slide along the installation cylinder to open or close the construction hole; since the control unit is electrically connected to each control module, the control unit can start or stop the control module to open or close the construction hole of each installation cylinder, so that during the fracturing construction process, the construction hole of any layer can be selectively opened or closed through the control of the control unit, and thus the construction hole of the corresponding layer can be controlled to be opened or closed according to the needs of the fracturing construction, and each production layer section can be evenly transformed to extend the production cycle of the deep shale reservoir and improve the comprehensive oil and gas production efficiency of the long horizontal well. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the completion fracturing construction system provided by the embodiment of the present invention.

[0021] Figure 2 It is a schematic structural diagram of the process string of the completion fracturing construction system provided by the embodiment of the present invention.

[0022] Figure 3 It is a schematic structural diagram of the control valve of the completion fracturing construction system provided by the embodiment of the present invention.

[0023] Figure 4 is Figure 3 The partial enlarged view of part A in

[0024] Figure 5 is Figure 3 The partial enlarged view of part B in

[0025] Figure 6 is Figure 3 The partial enlarged view of part C in

[0026] Figure 7is a sectional view taken along line A-A in Figure 3 in the figure.

[0027] Figure 8 It is a schematic structural diagram of a control valve when the construction hole of the well completion fracturing construction system provided by the embodiment of the present invention is in a closed state.

[0028] Figure 9 It is a schematic structural diagram of a control valve when the construction hole of the well completion fracturing construction system provided by the embodiment of the present invention is in an open state.

[0029] Among them, the reference numerals in the figure are as follows:

[0030] 10—process string; 20—control unit; 30—power supply unit

[0031] 40—control valve; 41—construction hole; 42—installation cylinder

[0032] 43—sliding sleeve; 44—control module; 45—first driving cavity

[0033] 46—second driving cavity; 47—limiting post; 48—plunger

[0034] 421—hydraulic cavity; 431—connection hole; 441—first control component

[0035] 442—second control component; 443—motor; 444—lead screw

[0036] 445—transmission component; 446—circuit board; 4211—first connection cavity

[0037] 4212—second connection cavity; 4451—lead screw sleeve; 4452—transmission gear. Detailed implementation manners

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] The present invention provides a well completion fracturing construction system, as Figures 1 - 2 shown, which includes a process string 10, a control unit 20, a power supply unit 30 and a plurality of control valves 40. The process string 10 is used for running into the well for completion; each control valve 40 is arranged on the process string 10 at intervals along the extension direction of the process string 10, and each control valve 40 is provided with a construction hole 41 for fracturing construction; the control unit 20 is electrically connected to each control valve 40 and is used to control the control valve 40 to open or close the construction hole 41; the power supply unit 30 is electrically connected to the control unit 20 and is used to supply power to the control unit 20.

[0040] Specifically, when the completion fracturing construction system sets up the process string 10, the control unit 20, the power supply unit 30 and several control valves 40 to perform the fracturing construction of the completion, the process string 10 can be lowered into the well for completion. Each control valve 40 is arranged at intervals along the extending direction of the process string 10, and each control valve 40 is provided with a construction hole 41. The process string 10 can carry out the fracturing construction through the construction hole 41. Since the control unit 20 is electrically connected to each control valve 40, the control unit 20 can control the control valve 40 to open or close the construction hole 41 of each control valve 40. When performing the fracturing construction, the construction hole 41 at any layer can be selectively opened or closed through the control of the control unit 20. When performing the fracturing construction, sequential construction can be carried out through each construction hole 41, or the construction hole 41 at the corresponding layer can be controlled to open or close according to the needs of the fracturing construction to perform the separate construction of this layer, so as to evenly transform each production interval and extend the production cycle of the deep shale reservoir and improve the comprehensive oil and gas exploitation benefit of the long horizontal well.

[0041] It can be understood that the power supply unit 30 can be the commercial power or any power supply device installed at the construction site.

[0042] In this embodiment, as Figure 3 and 8 shown in FIGS. 8-9, the control valve 40 includes an installation cylinder 42, a sliding sleeve 43 and a control module 44. The installation cylinder 42 is installed on the process string 10, the construction hole 41 is installed on the surface of the installation cylinder 42, the sliding sleeve 43 is slidably connected to the inner wall of the installation cylinder 42 and is located on one side of the construction hole, and the control module 44 is installed on the installation cylinder 42 and is electrically connected to the control unit 20. The control unit 20 is used to control the start and stop of the control module 44, so that the control module 44 drives the sliding sleeve 43 to slide along the inner wall of the installation cylinder 42 to open or close the construction hole. Specifically, when performing the fracturing construction, the control unit 20 sends a control signal to the control module 44, and the control module 44 controls the sliding sleeve 43 to slide, so that the sliding sleeve 43 exposes or shields the construction hole 41, thereby controlling the opening or closing of the construction hole 41.

[0043] In this embodiment, further, as Figure 3 、 5 shown in FIGS. 8-9, the surface of the sliding sleeve 43 is provided with a connection hole 431, and the sliding sleeve 43 can be slidably connected to the construction hole along the inner wall of the installation cylinder 42. Specifically, the control module 44 controls the sliding sleeve 43 to slide, so that the connection hole 431 and the construction hole are aligned or staggered, thereby realizing the opening or closing of the construction hole.

[0044] In this embodiment, further, as Figures 3 - 4As shown in FIGS. 8 - 9, a hydraulic chamber 421 is provided inside the mounting cylinder 42. Both ends of the hydraulic chamber 421 are respectively connected to the sliding sleeve 43 and the control module 44. The hydraulic chamber 421 is filled with hydraulic oil, and the control module 44 is used to drive the sliding sleeve 43 to slide through the hydraulic oil in the hydraulic chamber 421. Specifically, the control module 44 can drive the hydraulic oil in the hydraulic chamber 421 to make the hydraulic oil push the sliding sleeve 43 to slide.

[0045] It can be understood that the hydraulic chamber 421 can be arranged on one side of the end of the sliding sleeve 43, and the control module 44 can control the reciprocating movement of the hydraulic oil in the hydraulic chamber 421 to realize the reciprocating sliding of the sliding sleeve 43 inside the mounting cylinder 42.

[0046] In this embodiment, as Figures 3 - 4 As shown in FIGS. 8 - 9, a first driving chamber 45 and a second driving chamber 46 are arranged between the sliding sleeve 43 and the mounting cylinder at intervals along the axial direction of the sliding sleeve 43. The control module 44 includes a first control component 441 and a second control component 442. The first control component 441 and the second control component 442 are used to drive the pressure - supplying liquid in the hydraulic chamber 421 to alternately enter the first driving chamber 45 or the second driving chamber 46. Specifically, when the first control component 441 controls the hydraulic oil to enter the first driving chamber 45, the hydraulic oil will drive the sliding sleeve 43 to slide toward the side where the first driving chamber 45 is located. When the second control component 442 controls the hydraulic oil to enter the second driving chamber 46, the hydraulic oil will drive the sliding sleeve 43 to slide toward the side where the second driving chamber 46 is located, thereby realizing the reciprocating sliding of the sliding sleeve 43 and opening or closing the construction hole 41.

[0047] In this embodiment, further, the second driving chamber 46 is an annular chamber. Specifically, by setting the second driving chamber 46 as an annular chamber, the force on the circumferential direction of the sliding sleeve 43 can be balanced, which is convenient for the balanced sliding of the sliding sleeve inside the mounting cylinder 42.

[0048] In this embodiment, as Figures 3 - 4 As shown in FIGS. 8 - 9, the hydraulic chamber 421 includes a first connection chamber 4211 and a second connection chamber 4212. The first connection chamber 4211 is communicated with the first driving chamber 45, the second connection chamber 4212 is communicated with the second driving chamber 46, and the first connection chamber 4211 and the second connection chamber 4212 are respectively connected to the first control component 441 and the second control component 442.

[0049] Specifically, the first control component 441 is used to drive the hydraulic oil in the first connection chamber 4211 to enter the first driving chamber 45, or pump the driving liquid from the first driving chamber 45 to the first connection chamber 4211. The second control component 442 is used to drive the hydraulic oil in the second connection chamber 4212 to enter the second driving chamber 46, or pump the driving liquid from the second driving chamber 46 to the second connection chamber 4212.

[0050] When the first control component 441 drives the hydraulic oil of the first connecting chamber 4211 to enter the first driving chamber 45, the second control component 442 drives the driving liquid of the second driving chamber 46 to enter the second connecting chamber 4212, thereby increasing the volume of the first driving chamber 45 and reducing the volume of the second driving chamber 46, so that the sleeve 43 slides toward the side of the first driving chamber 45, so that the connecting hole 431 and the construction hole 41 are staggered, and the construction hole 41 is closed; when the first control component 441 drives the hydraulic oil of the first driving chamber 45 to enter the first connecting chamber 4211, the second control component 442 drives the driving liquid of the second connecting chamber 4212 to enter the second driving chamber 46, thereby reducing the volume of the first driving chamber 45 and increasing the volume of the second driving chamber 46, so that the sleeve 43 slides toward the side of the second driving chamber 46, so that the connecting hole 431 and the construction hole 41 are connected, and the construction hole 41 is opened.

[0051] In this embodiment, further, Figures 3 - 4 As shown in FIGS. 8 and 9 , the second driving cavity 46 is also connected to the first connecting cavity 4211 . Specifically, if the second drive chamber 46 is in a disconnected state with the first connecting chamber 4211, in order to avoid mutual influence between the first control component 441 and the second control component 442, the operating speeds of the first control component 441 and the second control component 442 need to be kept synchronized. Through the connection setting between the second drive chamber 46 and the first connecting chamber 4211, even if there is a partial deviation in the operation of the first control component 441 and the second control component 442, the hydraulic oil can enter the second drive chamber 46 through the first connecting chamber 4211, or enter the first connecting chamber 4211 from the second drive chamber 46; that is, if the operating speed of the first control component 441 is greater than that of the second control component 442, the hydraulic oil can enter the first connecting chamber 4211 from the second drive chamber 46 to supplement the hydraulic oil in the first drive chamber 45 and the first connecting chamber 4211; if the operating speed of the second control component 442 is greater than that of the first control component 441, the hydraulic oil can enter the second drive chamber 46 from the first connecting chamber 4211 to supplement the hydraulic oil in the second drive chamber 46 and the second connecting chamber 4212.

[0052] In this embodiment, Figure 3 and 7As shown in FIGS. 1 to 9, the first control assembly 441 includes a motor 443, a lead screw 444, and a transmission assembly 445. The motor 443 is fixed to the mounting cylinder 42. One end of the lead screw 444 is slidably connected to the first connection cavity 4211, and the other end of the lead screw 444 extends toward the direction of the motor 443. The transmission assembly 445 is connected to the lead screw 444 and the shaft of the motor 443. The motor 443 is used to drive the lead screw 444 to slide along the first connection cavity 4211 through the transmission of the transmission assembly 445. Specifically, when performing the hydraulic drive of the sliding sleeve 43, the control unit 20 controls the motor 443 to start. The motor 443 drives the lead screw 444 to rotate through the transmission assembly 445 and slide along the first connection cavity 4211, driving the drive fluid from the first connection cavity 4211 to the first drive cavity 45, or pumping the drive fluid from the first drive cavity 45 to the first connection cavity 4211.

[0053] In this embodiment, as Figure 7 shown, the first control assembly 441 further includes a circuit board 446, and the circuit board 446 is electrically connected to the control unit 20 and the motor 443.

[0054] In this embodiment, the second control assembly 442 has the same structure as the first control assembly 441, and the lead screw 444 of the second control assembly 442 is slidably connected to the second connection cavity 4212.

[0055] In this embodiment, as Figure 3 and 8 shown in FIGS. 1 to 9, the transmission assembly 445 includes a lead screw sleeve 4451 and a transmission gear 4452. The lead screw sleeve 4451 is sleeved on the surface of the lead screw 444 and is threadedly connected to the lead screw 444. The transmission gear 4452 is fixed to the shaft of the motor 443 and meshes with the lead screw sleeve 4451. Specifically, when performing the hydraulic drive of the sliding sleeve 43, the motor 443 drives the transmission gear 4452 to rotate. When the transmission gear 4452 rotates, it drives the lead screw sleeve 4451 to rotate. When the lead screw sleeve 4451 rotates, it can drive the lead screw 444 to slide along the first connection cavity 4211.

[0056] In this embodiment, as Figures 3 - 4 shown in FIGS. 1 and 8 - 9, the control valve 40 further includes a limit post 47 and a plunger 48. The limit post 47 is installed in the mounting cylinder 42 and extends into the first drive cavity 45 for restricting the rotation of the sliding sleeve 43. The plunger 48 is threadedly connected to the mounting cylinder 42 and abuts against the limit post 47. Specifically, by extending into the first drive cavity 45, the limit post 47 can effectively restrict the rotation of the sleeve inside the mounting cylinder 42. By being threadedly connected to the mounting cylinder 42, the plunger 48 can fix the limit post 47, and at the same time, it is convenient for the disassembly and assembly of the limit post 47, thus facilitating the disassembly and assembly of the sliding sleeve 43.

[0057] In this embodiment, in addition to supplying power to the control unit 20, the power supply unit 30 can also supply power to devices such as the control valve 40. The output voltage of the power supply unit 30 is an adjustable voltage of AC220V and DC1471V, and can provide a voltage of 48V to the process string 10. The common engineering power supply of 380V three-phase alternating current passes through a three-phase dry isolation transformer to output alternating current of 703V, and is output and regulated to direct current of 1471V through a three-phase bridge rectifier (after passing through the three-phase bridge rectifier, the output voltage is 2.34 times the input voltage), and is transmitted to 5000m underground. Due to line resistance loss, the final output is direct current of 48V, and then after step-down and voltage stabilization by the power supply module, it is output to the working voltages (such as 12V, 24V, etc.) required by each sensor or the motor 443.

[0058] In this embodiment, the controller of the control unit 20 is mainly responsible for controlling the sending of drive signals and the analysis, processing, and feedback of data reception, and remotely controlling the downhole control valve 40. The control unit 20 is operated by software and runs after setting parameters as needed. The device conducts self-checks and feeds back downhole information, including the input voltage of the motor 443 of the power supply module, downhole temperature and pressure, the switch state of the construction hole 41, and the rotation speed, rotation direction, and number of running circles of the motor 443. When necessary, the operator needs to adjust the ground power supply unit 30 to meet the usage requirements of downhole tools, and issue an execution command after confirmation. The ground controller is also responsible for functions such as storing test data and generating reports, and adopts a friendly software interaction interface to achieve the stable operation of the entire system.

[0059] The control unit 20 is composed of a main control computer, a PLC, and an optoelectronic signal converter. Current and signals are transmitted by the ground control unit 20 through an optoelectronic composite cable. The downhole circuit board 446 receives the current and signals. The current enters the power supply module of the downhole circuit board 446, and the signal enters the control module 44 (with sensors) of the circuit board 446. The control module 44 of the circuit board 446 controls the operation of the motor 443 (with sensors). The signals between the motor 443 and the control module 44 are fed back to the optoelectronic composite cable, transferred to the PLC by the optoelectronic signal converter, and finally displayed on the main control computer side. Based on this data and the actual switch situation of the downhole control valve 40, the accuracy of the transmission and execution of the control signal is judged.

[0060] The specific implementation manners of the present invention described above do not constitute a limitation to the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A completion and fracturing construction system, characterized in that, Comprising: A work string, which is used for running in hole for completion; A plurality of control valves, each of the control valves is arranged at intervals along the extending direction of the work string on the work string. The control valve includes an installation cylinder, a sliding sleeve and a control module. The installation cylinder is installed on the work string. A construction hole is arranged on the surface of the installation cylinder for fracturing construction. The sliding sleeve is slidably connected to the installation cylinder. The control module is installed in the installation cylinder and is used to drive the sliding sleeve to slide along the installation cylinder to open or close the construction hole; And A control unit, which is electrically connected to each of the control modules and is used to control the start and stop of each control module; Wherein, a hydraulic cavity is arranged inside the installation cylinder. Two ends of the hydraulic cavity are respectively connected to the sliding sleeve and the control module. The hydraulic cavity is used for filling hydraulic oil. The control module is used to drive the sliding sleeve to slide through the hydraulic oil in the hydraulic cavity; A first driving cavity and a second driving cavity which are arranged at intervals along the axial direction of the sliding sleeve are arranged between the sliding sleeve and the installation cylinder. The control module includes a first control component and a second control component. The first control component and the second control component are used to drive the pressure-supplying liquid in the hydraulic cavity to alternately enter the first driving cavity or the second driving cavity; The second driving cavity is an annular cavity; The hydraulic cavity includes a first connection cavity and a second connection cavity. The first connection cavity is communicated with the first driving cavity. The second connection cavity is communicated with the second driving cavity. The first connection cavity and the second connection cavity are respectively connected to the first control component and the second control component; The second driving cavity is also communicated with the first connection cavity; The first control component includes a motor, a lead screw and a transmission component. The motor is fixed on the installation cylinder. One end of the lead screw is slidably connected to the first connection cavity. The other end of the lead screw extends towards the direction of the motor. The transmission component is connected to the lead screw and the shaft of the motor. The motor is used to drive the lead screw to slide along the first connection cavity through the transmission of the transmission component.

2. The completion and fracturing construction system according to claim 1, wherein The transmission component includes a lead screw sleeve and a transmission gear. The lead screw sleeve is sleeved on the surface of the lead screw and is threadedly connected to the lead screw. The transmission gear is fixed on the shaft of the motor and meshes with the lead screw sleeve.

3. The completion and fracturing construction system according to claim 1, wherein The control valve further includes a limit post and a plunger. The limit post is installed on the installation cylinder and extends into the first driving cavity to limit the rotation of the sliding sleeve. The plunger is threadedly connected to the installation cylinder and abuts against the limit post.

4. The completion and fracturing construction system according to any one of claims 1 to 3, characterized in that, A connection hole is formed on the surface of the sliding sleeve. The sliding sleeve is slidably connected to the construction hole along the inner wall of the installation cylinder.

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