Well cementation anti-rotation rubber plug testing device and method

Abstract

The invention relates to the technical field of oil casing well cementation operation tools, in particular to a well cementation anti-rotation rubber plug testing device and method, and aims to solve the problem that drilling speed is affected due to lack of anti-rotation data of a well cementation anti-rotation rubber plug. The invention provides a well cementation anti-rotation rubber plug testing device which comprises an upper locking mechanism, a lower locking mechanism and a pressing mechanism. The upper rubber plug is inserted into the upper locking mechanism and connected with the upper locking mechanism, the lower rubber plug is inserted into the lower locking mechanism and connected with the lower locking mechanism, and the pressing mechanism abuts against the upper locking mechanism so that the upper rubber plug can be meshed with the lower rubber plug. An upper rubber plug and a lower rubber plug are installed on an upper locking mechanism and a lower locking mechanism respectively, the upper rubber plug and the lower rubber plug are pressed through a pressing mechanism to be meshed so as to simulate the working conditions of the upper rubber plug and the lower rubber plug, then a torque wrench is used for rotating so as to obtain anti-rotation data of the well cementation anti-rotation rubber plug, and a basis is provided for selecting the rotating speed and torque when the rubber plugs are drilled and removed; and the rubber plug is drilled and removed as soon as possible.

Description

Technical Field

[0001] The invention relates to the technical field of oil casing cementing operation tools, in particular to a cementing anti-rotation rubber plug testing device and method. Background Art

[0002] With the development of drilling technology, the drilling depth continues to increase, and the length of the casing string is getting longer and longer. In order to reinforce the well wall, ensure continued drilling, and seal the oil, gas and water layers, ensure oil testing during exploration and reasonable oil and gas production during the entire mining process, cementing operations are required, that is, running casing and filling cement in the wellbore and steel pipe annulus.

[0003] The cementing anti-rotation plug includes an upper plug and a lower plug. The lower plug is placed first before cementing to separate the cement slurry from the mud and prevent the cement slurry from being contaminated. After the collision and pressure, since the lower plug is hollow, the pressure is held and the rubber membrane is broken to provide a channel for the cement slurry to establish circulation. Then, cement is injected, the upper plug is placed, pumping, collision and pressure are applied, and cementing is completed.

[0004] Cementing anti-rotation plugs can be used to isolate cement slurry, clean casing walls, and prevent cement slurry contamination. After the plug hits the float collar, it can accurately indicate the cement slurry replacement position and casing sealing performance. Cementing anti-rotation plugs, combined with anti-rotation float collars and float shoes, can effectively prevent relative rotation between the upper and lower plugs, which can greatly increase the drilling speed. In actual use, due to the lack of anti-rotation data for cementing anti-rotation plugs, it is difficult to select a reasonable speed and torque, which is not conducive to increasing the drilling speed. Summary of the invention

[0005] The object of the present invention is to provide a cementing anti-rotation plug testing device and method to solve the problem of affecting the drilling speed due to the lack of anti-rotation data of the cementing anti-rotation plug.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] A cementing anti-rotation rubber plug testing device comprises an upper locking mechanism, a lower locking mechanism and a pressing mechanism; the upper rubber plug is inserted into the upper locking mechanism and connected to the upper locking mechanism, the lower rubber plug is inserted into the lower locking mechanism and connected to the lower locking mechanism, and the pressing mechanism abuts against the upper locking mechanism to make the upper rubber plug and the lower rubber plug mesh.

[0008] Furthermore, the upper locking mechanism includes an upper fixing sleeve, an upper fixing bolt and an upper fixing cap; the upper fixing cap is installed on the upper end of the upper fixing sleeve, the upper rubber plug is inserted into the upper fixing sleeve and abuts against the upper fixing cap; the upper fixing bolt is inserted into the side wall of the upper fixing sleeve and is threadedly connected to the upper fixing sleeve, and the upper fixing bolt abuts against the upper rubber plug; a wrench connecting port is opened on the upper fixing cap, and the wrench connecting port is coaxial with the upper rubber plug.

[0009] Furthermore, the upper locking mechanism also includes an upper connecting bolt, which is inserted into the upper fixing sleeve and the upper fixing cap at the same time and is threadedly connected to the upper fixing sleeve.

[0010] Furthermore, the lower locking mechanism includes a lower fixing sleeve, a lower fixing bolt and a lower fixing cap; the lower fixing cap is installed at the lower end of the lower fixing sleeve, the lower rubber plug is inserted into the lower fixing sleeve and abuts against the lower fixing cap; the lower fixing bolt is inserted into the side wall of the lower fixing sleeve and is threadedly connected to the lower fixing sleeve, and the lower fixing bolt abuts against the lower rubber plug.

[0011] Furthermore, the lower locking mechanism also includes a lower connecting bolt, which is inserted into the lower fixing sleeve and the lower fixing cap at the same time and is threadedly connected to the lower fixing sleeve.

[0012] Furthermore, the clamping mechanism includes a rotating assembly, which includes an upper pressing cap and a lower pressing cap, the upper pressing cap is rotatably connected to the lower pressing cap, and the end of the lower pressing cap facing away from the upper pressing cap abuts against the upper fixed cap; the upper pressing cap presses the lower pressing cap so that the lower pressing cap presses the upper fixed cap; the side wall of the lower pressing cap has a hole.

[0013] Furthermore, the rotating assembly also includes a thrust bearing, which is installed between the upper pressure cap and the lower pressure cap.

[0014] Furthermore, the clamping mechanism also includes a screw rod, which is inserted into the upper pressure cap and rotatably connected to the upper pressure cap. The screw rod rotates around its own axis to push the rotating component to clamp the upper locking mechanism.

[0015] Furthermore, the clamping mechanism also includes a bracket, the screw rod is inserted into the bracket and threadedly connected to the bracket, and the lower fixing cap is installed on the bracket.

[0016] Another aspect of the present invention provides a cementing anti-rotation plug test method, using the cementing anti-rotation plug test device, comprising the following steps:

[0017] Assemble the rubber plug: install the lower rubber plug into the lower fixing sleeve and tighten the lower fixing bolt to connect the lower rubber plug and the lower fixing sleeve, install the upper rubber plug into the upper fixing sleeve and tighten the upper fixing bolt to connect the upper rubber plug and the upper fixing sleeve, put the upper locking mechanism and the upper rubber plug on the lower rubber plug and mesh the upper rubber plug with the lower rubber plug;

[0018] Press the rubber plug: place the rotating assembly on the upper fixed cap, then rotate the screw rod so that the screw rod is inserted into the upper pressing cap and push the rotating assembly to press the upper locking mechanism;

[0019] Torque test: Insert the torque wrench into the wrench connection port and turn the torque wrench to drive the upper locking mechanism to rotate.

[0020] Based on the above technical solutions, the technical effects that can be achieved by the present invention are:

[0021] The cementing anti-rotation plug testing device provided by the present invention comprises an upper locking mechanism, a lower locking mechanism and a pressing mechanism; the upper rubber plug is inserted into the upper locking mechanism and connected to the upper locking mechanism, the lower rubber plug is inserted into the lower locking mechanism and connected to the lower locking mechanism, and the pressing mechanism abuts against the upper locking mechanism to make the upper rubber plug and the lower rubber plug mesh.

[0022] The cementing anti-rotation plug testing device provided by the present invention simulates the working conditions of the upper rubber plug and the lower rubber plug by installing the upper rubber plug and the lower rubber plug on the upper locking mechanism and the lower locking mechanism respectively, and pressing the upper rubber plug and the lower rubber plug with a pressing mechanism to make them mesh, thereby simulating the working conditions of the upper rubber plug and the lower rubber plug. Subsequently, the torque required for the upper rubber plug and the lower rubber plug to rotate relative to each other is rotated by a torque wrench to obtain the anti-rotation data of the cementing anti-rotation plug, providing a basis for selecting the rotation speed and torque when drilling out the plug, thereby achieving the fastest drilling out of the plug. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of a cementing anti-rotation plug testing device provided by an embodiment of the present invention;

[0025] Figure 2 A cross-sectional schematic diagram of a cementing anti-rotation plug testing device provided by an embodiment of the present invention;

[0026] Figure 3 It is a structural schematic diagram of the pressure cap;

[0027] Figure 4 It is a schematic diagram of the structure of the upper fixing cap.

[0028] Icons: 100-upper locking mechanism; 200-lower locking mechanism; 300-clamping mechanism; 110-upper fixing sleeve; 120-upper fixing bolt; 130-upper fixing cap; 140-upper connecting bolt; 131-wrench connecting port; 210-lower fixing sleeve; 220-lower fixing bolt; 230-lower fixing cap; 240-lower connecting bolt; 310-rotating assembly; 320-screw rod; 330-bracket; 340-handle; 311-upper pressure cap; 312-lower pressure cap; 313-thrust bearing; 10-upper rubber plug; 20-lower rubber plug; a-torque wrench. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0032] The cementing anti-rotation plug, combined with the anti-rotation float collar and float shoe, can effectively prevent the upper and lower plugs from rotating relative to each other, which can greatly increase the drilling speed. In actual use, due to the lack of anti-rotation data for cementing anti-rotation plugs, it is difficult to select a reasonable speed and torque, which is not conducive to increasing the drilling speed.

[0033] In view of this, the present invention provides a cementing anti-rotation plug testing device, including an upper locking mechanism 100, a lower locking mechanism 200 and a pressing mechanism 300; the upper rubber plug 10 is inserted into the upper locking mechanism 100 and connected to the upper locking mechanism 100, the lower rubber plug 20 is inserted into the lower locking mechanism 200 and connected to the lower locking mechanism 200, and the pressing mechanism 300 abuts against the upper locking mechanism 100 to make the upper rubber plug 10 and the lower rubber plug 20 engage.

[0034] The cementing anti-rotation plug test device provided by the present invention simulates the working conditions of the upper rubber plug 10 and the lower rubber plug 20 by respectively installing the upper rubber plug 10 and the lower rubber plug 20 on the upper locking mechanism 100 and the lower locking mechanism 200, and pressing the upper rubber plug 10 and the lower rubber plug 20 with the pressing mechanism 300, and then rotating the upper locking mechanism 100 with a torque wrench a to test the torque required for the upper rubber plug 10 and the lower rubber plug 20 to rotate relative to each other, so as to obtain the anti-rotation data of the cementing anti-rotation plug, provide a basis for selecting the rotation speed and torque when drilling out the plug, and realize the fastest drilling out of the plug.

[0035] The following combination Figure 1-Figure 4 The structure and shape of the cementing anti-rotation plug test device provided in this embodiment are described in detail:

[0036] In an optional solution of this embodiment, the upper locking mechanism 100 includes an upper fixing sleeve 110, an upper fixing bolt 120, an upper fixing cap 130 and an upper connecting bolt 140. Figure 1 , Figure 2 As shown. The upper fixing cap 130 is sleeved on the upper end of the upper fixing sleeve 110, and the upper connecting bolt 140 is inserted into the side walls of the upper fixing sleeve 110 and the upper fixing cap 130 at the same time and is threadedly connected to the upper fixing sleeve 110, so that the upper fixing sleeve 110 and the upper fixing cap 130 are connected as a whole. The upper rubber plug 10 is inserted into the upper fixing sleeve 110 and abuts against the upper fixing cap 130, and the upper fixing bolt 120 is inserted into the side wall of the upper fixing sleeve 110 and is threadedly connected to the upper fixing sleeve 110, and at the same time, the upper fixing bolt 120 abuts against the upper rubber plug 10 to lock the upper rubber plug 10 to prevent relative rotation between the upper rubber plug 10 and the upper fixing sleeve 110, so that the upper rubber plug 10 can be driven by the rotation of the upper fixing sleeve 110. Specifically, in this embodiment, four upper fixing bolts 120 are evenly distributed in an annular shape to ensure uniform force and reliable locking. Furthermore, a wrench connection port 131 is provided on the upper fixing cap 130, and the wrench connection port 131 is coaxial with the upper rubber plug 10. Figure 4 As shown, the wrench connection port 131 is a square hole, which is used to cooperate with the torque wrench a to transmit torque.

[0037] In an optional solution of this embodiment, the lower locking mechanism 200 includes a lower fixing sleeve 210, a lower fixing bolt 220, a lower fixing cap 230, and a lower connecting bolt 240. Figure 2 As shown. The lower fixing cap 230 is sleeved on the lower end of the lower fixing sleeve 210, and the lower connecting bolt 240 is inserted into the side walls of the lower fixing sleeve 210 and the lower fixing cap 230 at the same time and is threadedly connected to the lower fixing sleeve 210, so that the lower fixing sleeve 210 and the lower fixing cap 230 are connected as a whole. The lower rubber plug 20 is inserted into the lower fixing sleeve 210 and abuts against the lower fixing cap 230, and the lower fixing bolt 220 is inserted into the side wall of the lower fixing sleeve 210 and is threadedly connected to the lower fixing sleeve 210, and at the same time, the lower fixing bolt 220 abuts against the lower rubber plug 20 to lock the lower rubber plug 20 to prevent the lower rubber plug 20 and the lower fixing sleeve 210 from rotating relative to each other, so that the lower rubber plug 20 can be locked by the lower fixing sleeve 210 to prevent the lower rubber plug 20 from rotating. In this embodiment, four lower fixing bolts 220 are evenly distributed in an annular shape to ensure uniform force and reliable locking.

[0038] In this embodiment, the upper rubber plug 10 and the upper fixing sleeve 110 are interference fit, and the lower rubber plug 20 and the lower fixing sleeve 210 are interference fit. The interference fit increases the connection between the rubber plug and the fixing sleeve to avoid relative rotation.

[0039] In an optional solution of this embodiment, the pressing mechanism 300 includes a rotating assembly 310, a screw rod 320, a bracket 330 and a handle 340. Figure 1 , Figure 2 As shown. Specifically, the rotating assembly 310 includes an upper pressure cap 311, a lower pressure cap 312 and a thrust bearing 313. The thrust bearing 313 is respectively inserted into the upper pressure cap 311 and the lower pressure cap 312, so that the upper pressure cap 311 and the lower pressure cap 312 are rotatably connected and can transmit pressure. The screw rod 320 is inserted into the bracket 330 and is threadedly connected to the bracket 330; one end of the screw rod 320 is inserted into the upper pressure cap 311 and is rotatably connected to the upper pressure cap 311, and abuts against the upper pressure cap 311, and the other end of the screw rod 320 is connected to the handle 340. The handle 340 is rotated to rotate the screw rod 320 around its own axis, so that the screw rod 320 pushes the rotating assembly 310 downward, and the upper pressing cap 311 presses the lower pressing cap 312 through the thrust bearing 313, so that the rotating assembly 310 presses the upper locking mechanism 100, that is, the lower pressing cap 312 presses the upper fixing cap 130, and finally the anti-rotation teeth of the upper rubber plug 10 and the lower rubber plug 20 are reliably engaged. The screw rod 320 limits the rotating assembly 310 while pushing the rotating assembly 310, preventing the rotating assembly 310 from moving in the radial direction.

[0040] In order to ensure that the torque wrench a can be inserted into the wrench connection hole and the torque wrench a can be rotated, the side wall of the pressing cap 312 is opened, such as Figure 3 As shown, when the torque wrench a is rotated, the pressing cap 312 rotates simultaneously.

[0041] In this embodiment, the bracket 330 includes a bottom plate, a round tube and square steel. Figure 1 As shown, the round tube is vertically mounted on the bottom plate, the lower fixing cap 230 is sleeved on the round tube and fixed by bolts, and the bolts are simultaneously inserted into the side walls of the lower fixing cap 230 and the side walls of the round tube and threadedly connected to the round tube, thereby fixing the lower locking mechanism 200. Three square steels form a U-shaped structure, and threaded holes are provided on the horizontally arranged square steels for threaded connection with the screw rod 320.

[0042] In this embodiment, the end of the screw rod 320 away from the upper pressure cap 311 can be set to a square shape for cooperating with a torque wrench a to obtain the pressure between the upper rubber plug 10 and the lower rubber plug 20 through the torque wrench a. The screw rod 320 can be set to a lead screw to make the rotation of the screw rod 320 more stable.

[0043] Based on the cementing anti-rotation plug test device provided in this embodiment, a cementing anti-rotation plug test method is proposed, using the cementing anti-rotation plug test device, including the following steps:

[0044] Assemble the rubber plug: install the lower rubber plug 20 into the lower fixing sleeve 210 and tighten the lower fixing bolt 220 to connect the lower rubber plug 20 with the lower fixing sleeve 210, install the upper rubber plug 10 into the upper fixing sleeve 110 and tighten the upper fixing bolt 120 to connect the upper rubber plug 10 with the upper fixing sleeve 110, put the upper locking mechanism 100 and the upper rubber plug 10 on the lower rubber plug 20 and mesh the anti-rotation teeth of the upper rubber plug 10 and the lower rubber plug 20;

[0045] Pressing the rubber plug: placing the rotating assembly 310 on the upper fixing cap 130, and then rotating the screw rod 320 so that the screw rod 320 is inserted into the upper pressing cap 311 and pushes the rotating assembly 310 to press the upper locking mechanism 100;

[0046] Torque test: insert the torque wrench a into the wrench connection port 131 and rotate the torque wrench a to drive the upper locking mechanism 100 to rotate. The torque value when the upper rubber plug 10 and the lower rubber plug 20 rotate relative to each other is measured by the torque wrench a.

[0047] In addition, when rotating the screw 320, a torque wrench a can be used to obtain the torque for tightening or tighten with a set torque to compress the rotating assembly 310, thereby obtaining the positive pressure between the upper plug 10 and the lower plug 20 according to the pitch of the screw 320.

[0048] The cementing anti-rotation plug testing device provided in this embodiment can test cementing anti-rotation plugs of different specifications by replacing the upper fixed sleeve 110 and the lower fixed sleeve 210 with different inner diameters, thereby obtaining anti-rotation data, providing parameters for actual plug removal, and achieving maximum speed of drilling and removal with reasonable pressure, torque and rotation speed, avoiding relative rotation of the upper plug 10 and the lower plug 20 during the drilling and removal process, thereby improving the drilling and removal efficiency.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cementing anti-rotation plug testing device, characterized in that: It comprises an upper locking mechanism (100), a lower locking mechanism (200) and a pressing mechanism (300); The upper rubber plug (10) is inserted into the upper locking mechanism (100) and connected to the upper locking mechanism (100), the lower rubber plug (20) is inserted into the lower locking mechanism (200) and connected to the lower locking mechanism (200), and the pressing mechanism (300) abuts against the upper locking mechanism (100) to enable the upper rubber plug (10) and the lower rubber plug (20) to mesh.

2. The cementing anti-rotation plug testing device according to claim 1, characterized in that: The upper locking mechanism (100) comprises an upper fixing sleeve (110), an upper fixing bolt (120) and an upper fixing cap (130); The upper fixing cap (130) is installed on the upper end of the upper fixing sleeve (110), and the upper rubber plug (10) is inserted into the upper fixing sleeve (110) and abuts against the upper fixing cap (130); The upper fixing bolt (120) is inserted into the side wall of the upper fixing sleeve (110) and is threadedly connected to the upper fixing sleeve (110), and the upper fixing bolt (120) abuts against the upper rubber plug (10); The upper fixing cap (130) is provided with a wrench connection opening (131), and the wrench connection opening (131) is coaxial with the upper rubber plug (10).

3. The cementing anti-rotation plug testing device according to claim 2, characterized in that: The upper locking mechanism (100) further comprises an upper connecting bolt (140), wherein the upper connecting bolt (140) is inserted into the upper fixing sleeve (110) and the upper fixing cap (130) at the same time and is threadedly connected to the upper fixing sleeve (110).

4. The cementing anti-rotation plug testing device according to claim 3, characterized in that: The lower locking mechanism (200) comprises a lower fixing sleeve (210), a lower fixing bolt (220) and a lower fixing cap (230); The lower fixing cap (230) is installed on the lower end of the lower fixing sleeve (210), and the lower rubber plug (20) is inserted into the lower fixing sleeve (210) and abuts against the lower fixing cap (230); The lower fixing bolt (220) is inserted into the side wall of the lower fixing sleeve (210) and is threadedly connected to the lower fixing sleeve (210), and the lower fixing bolt (220) abuts against the lower rubber plug (20).

5. The cementing anti-rotation plug testing device according to claim 4, characterized in that: The lower locking mechanism (200) further comprises a lower connecting bolt (240), wherein the lower connecting bolt (240) is inserted into the lower fixing sleeve (210) and the lower fixing cap (230) at the same time and is threadedly connected to the lower fixing sleeve (210).

6. The cementing anti-rotation plug testing device according to claim 5, characterized in that: The clamping mechanism (300) comprises a rotating assembly (310), wherein the rotating assembly (310) comprises an upper pressing cap (311) and a lower pressing cap (312), wherein the upper pressing cap (311) is rotatably connected to the lower pressing cap (312), and an end of the lower pressing cap (312) facing away from the upper pressing cap (311) abuts against the upper fixed cap (130); The upper pressing cap (311) presses the lower pressing cap (312) so that the lower pressing cap (312) presses the upper fixing cap (130); The side wall of the pressing cap (312) is opened.

7. The cementing anti-rotation plug testing device according to claim 6, characterized in that: The rotating assembly (310) further comprises a thrust bearing (313), wherein the thrust bearing (313) is installed between the upper pressure cap (311) and the lower pressure cap (312).

8. The cementing anti-rotation plug testing device according to claim 7, characterized in that: The clamping mechanism (300) further comprises a screw rod (320), wherein the screw rod (320) is inserted into the upper pressure cap (311) and is rotationally connected to the upper pressure cap (311), and the screw rod (320) rotates around its own axis to push the rotating assembly (310) to clamp the upper locking mechanism (100).

9. The cementing anti-rotation plug testing device according to claim 8, characterized in that: The pressing mechanism (300) further comprises a bracket (330), the screw rod (320) is inserted into the bracket (330) and threadedly connected to the bracket (330), and the lower fixing cap (230) is installed on the bracket (330).

10. A cementing anti-rotation plug test method, using the cementing anti-rotation plug test device as claimed in claim 9, characterized in that: The steps include: Assembling the rubber plug: installing the lower rubber plug (20) into the lower fixing sleeve (210) and tightening the lower fixing bolt (220) to connect the lower rubber plug (20) and the lower fixing sleeve (210); installing the upper rubber plug (10) into the upper fixing sleeve (110) and tightening the upper fixing bolt (120) to connect the upper rubber plug (10) and the upper fixing sleeve (110); placing the upper locking mechanism (100) and the upper rubber plug (10) on the lower rubber plug (20) and making the upper rubber plug (10) and the lower rubber plug (20) mesh; Pressing the rubber plug: placing the rotating assembly (310) on the upper fixed cap (130), and then rotating the screw rod (320) so that the screw rod (320) is inserted into the upper pressing cap (311) and pushes the rotating assembly (310) to press the upper locking mechanism (100); Torque test: insert the torque wrench (a) into the wrench connection port (131) and rotate the torque wrench (a) to drive the upper locking mechanism (100) to rotate.

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