Two-stage section milling device for underground casing pipe

Abstract

The invention provides a two-stage section milling device for an underground casing pipe. The two-stage section milling device comprises an upper-stage section milling mechanism and a lower-stage section milling mechanism which are axially connected, wherein the lower-stage section milling mechanism comprises a lower-stage shell, a driving assembly and a section milling part, the driving assembly and the section milling part are located in the lower-stage shell, a plurality of section milling openings are formed in the lower-stage shell, and the driving assembly movably abuts against the section milling part; the upper-stage section milling mechanism comprises an upper-stage shell, an auxiliary driving assembly and an auxiliary section milling part, the auxiliary driving assembly and the auxiliary section milling part are located in the upper-stage shell, at least one auxiliary section milling opening is formed in the upper-stage shell, and the auxiliary driving assembly is meshed with the auxiliary section milling part; wherein the interiors of the upper-stage shell and the lower-stage shell are respectively provided with a flow channel, and the lower-stage section milling mechanism opens or disconnects the two flow channels through the sliding sleeve component. By means of the section milling device, the problems that a traditional section milling tool is high in abrasion speed, low in section milling speed and short in single-trip footage are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas well workover, in particular to a two-stage section milling device for downhole casing. BACKGROUND

[0002] With the development of oilfield into the middle and later period, well pattern is imperfect due to casing damage or other reasons, and remaining oil is sporadically distributed. Section milling and window drilling is one of the important means to tap the potential of remaining oil and realize the recovery of old well productivity. For the plugging of old wells in gas storage construction, the Oil and Gas Energy

[2022] 495 document "Technical Specification for Drilling and Completion of Oil and Gas Reservoir Type Gas Storage and Old Well Treatment" clearly states that when the quality of the old well "direct cap layer section cementing is continuous and the length of the high-quality section is less than 25m and the cumulative length of the high-quality section is less than 50m, the casing section milling is carried out on the cap layer section above the reservoir top boundary, and the section milling length is not less than 40m". Therefore, the section miller is an essential tool for window drilling or section milling plugging of old wells in gas storage.

[0003] However, the traditional section milling tool has the disadvantages of fast wear, slow section milling speed and short single-trip footage. SUMMARY

[0004] In view of the above problems, the present application provides a two-stage section milling device for downhole casing to solve the problems of fast wear, slow section milling speed and short single-trip footage of the traditional section milling tool.

[0005] The technical scheme of the present application is:

[0006] A two-stage section milling device for downhole casing, comprising: an upper section milling mechanism and a lower section milling mechanism connected in the axial direction; wherein,

[0007] The lower section milling mechanism comprises a lower housing, a driving assembly and a section milling part located in the lower housing, a plurality of section milling openings are formed on the lower housing, and the driving assembly and the section milling part are in movable abutment;

[0008] The upper section milling mechanism comprises an upper housing, an auxiliary driving assembly and an auxiliary section milling part located in the upper housing, at least one auxiliary section milling opening is formed on the upper housing, and the auxiliary driving assembly and the auxiliary section milling part are in engagement;

[0009] Wherein, flow channels are respectively formed in the inner portions of the upper housing and the lower housing, and the lower section milling mechanism opens or disconnects the communication of the two flow channels through a sliding sleeve part; so as to be defined as:

[0010] When the two flow channels are in communication, the drilling fluid transmits driving force to the driving assembly, the driving assembly drives the section milling part to extend out of the section milling opening, and the downhole casing is section milled;

[0011] When the lower section milling mechanism stops milling the downhole casing, the two flow channels are disconnected by the sliding sleeve component, and the drilling fluid transmits driving force to the auxiliary driving assembly, which engages and drives the auxiliary section milling part to rotate and extend out of the auxiliary section milling port, thereby enhancing the milling of the downhole casing.

[0012] As one of the preferred solutions, the driving assembly comprises an axially connected lower transmission piston and a lower mandrel, and the flow channel penetrates through the lower transmission piston and the lower mandrel; the section milling part comprises a middle section milling structure and a lower section milling structure arranged axially and located at the plurality of section milling ports respectively; wherein the lower mandrel abuts against the middle section milling structure and the lower section milling structure.

[0013] The auxiliary driving assembly comprises an axially connected upper transmission piston and an upper mandrel, and the flow channel penetrates through the upper transmission piston and the upper mandrel; the auxiliary section milling part comprises at least one upper section milling cutter and is located at at least one auxiliary section milling port respectively; wherein the upper mandrel engages with each upper section milling cutter.

[0014] As one of the preferred solutions, the upper part of the lower housing is provided with a lower piston guide groove, and the lower transmission piston is arranged in the lower piston guide groove; the upper end of the lower piston guide groove is connected with an upper joint; wherein the lower transmission piston is provided with a flow distribution disc and a nozzle, and the lower end of the nozzle is connected with the corresponding flow channel.

[0015] The lower part of the upper housing is provided with an upper piston guide groove, and the upper transmission piston is arranged in the upper piston guide groove; the lower end of the upper piston guide groove is connected with a middle joint.

[0016] The upper joint and the middle joint are connected.

[0017] As one of the preferred solutions, the lower section milling mechanism further comprises a lower reset assembly, and the upper section milling mechanism further comprises an upper reset assembly; wherein,

[0018] The lower reset assembly comprises a lower spring sleeved on the lower mandrel, and the lower spring is installed in the lower piston guide groove; the top of the lower spring abuts against the lower surface of the lower transmission piston, and the bottom abuts against the stepped surface of the lower piston guide groove.

[0019] The lower reset assembly comprises an upper spring sleeved on the upper mandrel, and the upper spring is installed in the upper piston guide groove; the bottom of the upper spring abuts against the upper surface of the upper transmission piston, and the top abuts against the stepped surface of the upper piston guide groove.

[0020] As one of the preferred solutions, the segment milling port is a stepped through-hole structure, the large-diameter end of the through-hole structure is close to the outside of the lower shell, the small-diameter end is located at the inside of the lower shell, and the connection between the large-diameter end and the small-diameter end forms a stepped surface;

[0021] A plurality of the segment milling ports are respectively middle short tool grooves, middle long tool grooves, and lower tool grooves; a plurality of the middle short tool grooves and the middle long tool grooves are cross-distributed in the middle section of the lower shell and accommodate the middle section milling structure; and a plurality of the lower tool grooves are uniformly distributed in the lower section of the lower shell and accommodate the lower section milling structure.

[0022] As one of the preferred solutions, the middle section milling structure includes a middle short section milling structure and a middle long section milling structure.

[0023] The middle short section milling structure is composed of a middle short section milling cutter and a middle short tool holder, the middle short tool holder is connected with the stepped surface of the middle short tool groove, and the middle short section milling cutter is hinged with the middle short tool holder.

[0024] The middle long section milling structure is composed of a middle long section milling cutter and a middle long tool holder, the middle long section milling cutter is connected with the stepped surface of the middle long tool groove, and the middle long section milling cutter is hinged with the middle long tool holder.

[0025] The lower section milling structure is composed of a lower section milling cutter and a lower tool holder, the lower tool holder is connected with the stepped surface of the lower tool groove, and the lower section milling cutter is hinged with the lower tool holder.

[0026] As one of the preferred solutions, the lower core shaft is provided with a middle boss and a lower boss corresponding to the positions of the middle section and the lower section of the lower shell; wherein,

[0027] The back surface of the middle short section milling cutter is provided with a first reset barb and a first curved edge;

[0028] The back surface of the middle long section milling cutter is provided with a second reset barb and a second curved edge;

[0029] The back surface of the lower section milling cutter is provided with a third reset barb and a third curved edge;

[0030] The outer edge contour formed by the connection of the first reset barb and the first curved edge, and the outer edge contour formed by the connection of the second reset barb and the second curved edge are both matched with the outer edge contour of the middle boss; and the outer edge contour formed by the connection of the third reset barb and the third curved edge is matched with the outer edge contour of the lower boss.

[0031] As one of the preferred solutions, the upper section of the upper core shaft is provided with a step, and the outside of the step is provided with a rack.

[0032] The upper stage cutter is hinged with the auxiliary stage milling port, and is provided with a gear engaging with the rack towards one side of the step.

[0033] As one of the preferred schemes, the cutting edges and milling edges are respectively arranged on the blade surfaces of the middle short stage cutter, the middle long stage cutter and the lower stage cutter, and the cutting edges are located on the outer side.

[0034] As one of the preferred schemes, the sliding sleeve component comprises a sliding sleeve, a shear pin and a ball, the upper end of the sliding sleeve is in abutment with the upper transmission piston and is movably embedded in a grommet, a ball seat is arranged in the sliding sleeve, and the outer periphery of the sliding sleeve is connected with the upper housing through a plurality of shear pins.

[0035] The ball seat is used for receiving the ball to block the flow channel of the lower housing, so as to shear the shear pin under the pressure of the drilling fluid, make the sliding sleeve slide downward, and drive the upper transmission piston to slide upward through the drilling fluid, and drive the upper core shaft to engage with the auxiliary stage milling part.

[0036] Compared with the prior art, the application has the following advantages:

[0037] The application provides a two-stage milling device for a downhole casing, which comprises an upper stage milling mechanism and a lower stage milling mechanism connected in an axial direction, wherein the lower stage milling mechanism comprises a lower housing, a driving assembly and a stage milling part located in the lower housing, a plurality of stage milling ports are arranged on the lower housing, and the driving assembly is in abutment with the stage milling part; the upper stage milling mechanism comprises an upper housing, an auxiliary driving assembly and an auxiliary stage milling part located in the upper housing, at least one auxiliary stage milling port is arranged on the upper housing, and the auxiliary driving assembly is in engagement with the auxiliary stage milling part; inner parts of the upper housing and the lower housing are respectively provided with flow channels, and the lower stage milling mechanism opens or disconnects the communication between the two flow channels through a sliding sleeve component; so that when the two flow channels are in communication, the drilling fluid transmits driving force to the driving assembly, the driving assembly drives the stage milling part to extend out of the stage milling port to mill the downhole casing; when the lower stage milling mechanism stops milling the downhole casing, the two flow channels are disconnected through the sliding sleeve component, the drilling fluid transmits driving force to the auxiliary driving assembly, the auxiliary driving assembly engages to drive the auxiliary stage milling part, and the auxiliary stage milling part rotates to extend out of the auxiliary stage milling port to enhance the milling of the downhole casing.

[0038] By adopting the technical scheme of the application, the two-stage segment milling mechanism can complete the segmented segment milling in one trip, and after the lower segment milling mechanism loses the segment milling capability, the upper segment milling mechanism continues to work, realizes continuous segment milling operation, and reduces the operation time and downtime. The upper and lower segment milling mechanisms are respectively driven by independent driving assemblies, can independently perform segment milling operation, reduces the number of trips in single trip segment milling operation, prolongs the segment milling length in one trip, saves the segment milling time, and reduces the operation cost. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical scheme of the application, the drawings needed to be used in the description of the application will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0040] Figure 1 is the overall structure schematic diagram of the two-stage segment milling device for the downhole casing according to an embodiment of the application;

[0041] Figure 2 is the internal cross-sectional view of Figure 1 ;

[0042] Figure 3 is the overall structure schematic diagram of the lower segment milling mechanism according to an embodiment of the application;

[0043] Figure 4 is the overall structure schematic diagram of the upper segment milling mechanism according to an embodiment of the application;

[0044] Figure 5 is the overall structure diagram of the middle short segment milling cutter according to an embodiment of the application;

[0045] Figure 6 is the overall structure diagram of the middle long segment milling cutter according to an embodiment of the application;

[0046] Figure 7 is the overall structure diagram of the lower segment milling cutter according to an embodiment of the application.

[0047] Legend of the drawings:

[0048] In the diagram: 1. Lower stage housing; 1-1. Middle short cutter groove; 1-2. Middle long cutter groove; 1-3. Lower cutter groove; 1-4. Lower stage piston guide groove; 2. Lower stage spindle; 2-1. Middle boss; 2-2. Lower boss; 3. Lower stage drive piston; 3-1. Lower stage sealing ring; 3-2. Flow divider; 3-3. Nozzle; 3-4. Lower stage flow channel; 4. Middle short end mill; 4-1. First reset barb; 4-2. First curved edge; 4-3. First cutting edge; 4-4. First milling edge; 4-5. First positioning hole; 5. Middle short tool holder; 6. Middle long end mill; 6-1. Second reset barb; 6-2. Second curved edge; 6-3. Second... Cutting edge; 6-4, Second milling edge; 6-5, Second positioning hole; 7, Middle long tool holder; 8, Lower section milling cutter; 8-1, Third reset barb; 8-2, Third curved edge; 8-3, Third cutting edge; 8-4, Third milling edge; 8-5, Third positioning hole; 9, Lower tool holder; 10, Lower stage spring; 11, Upper connector; 12, Positioning shaft; 13, Upper stage housing; 13-1, Upper stage piston guide groove; 14, Upper stage transmission piston; 14-1, Upper stage sealing ring; 15, Upper stage mandrel; 16, Middle connector; 17, Upper stage spring; 18, Sliding sleeve; 18-1, Shear pin; 19, Upper section milling cutter; 20, Washer ring; 21, Ball. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] Reference Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the overall structure of the two-stage segment milling device for downhole casing shown in this invention. Figure 2 for Figure 1 An internal sectional view showing the housing and the various components located within it. (See attached image.) Figure 1 and Figure 2As shown, the embodiment of the present application provides a two-stage section milling device for downhole casing, comprising: an upper section milling mechanism and a lower section milling mechanism connected in axial direction; wherein the lower section milling mechanism comprises a lower casing 1, and a driving assembly and a section milling part located in the lower casing 1, a plurality of section milling openings are formed on the lower casing 1, and the driving assembly and the section milling part are in movable abutment; the upper section milling mechanism comprises an upper casing 13, and an auxiliary driving assembly and an auxiliary section milling part located in the upper casing 13, at least one auxiliary section milling opening is formed on the upper casing 13, and the auxiliary driving assembly and the auxiliary section milling part are in engagement; wherein inner parts of the upper casing 13 and the lower casing 1 are respectively provided with flow channels, and the lower section milling mechanism opens or disconnects the communication of the two flow channels through a sliding sleeve part; so as to be defined as:

[0051] When the two flow channels are in communication, the drilling fluid transmits driving force to the driving assembly, the driving assembly drives the section milling part to extend out of the section milling opening to mill the downhole casing;

[0052] When the lower section milling mechanism stops milling the downhole casing, the two flow channels are disconnected through the sliding sleeve part, the drilling fluid transmits driving force to the auxiliary driving assembly, the auxiliary driving assembly engages and drives the auxiliary section milling part to rotate and extend out of the auxiliary section milling opening to enhance the milling of the downhole casing.

[0053] Specifically, the axial direction of the present application can be understood as the direction from the upper section milling mechanism to the lower section milling mechanism or vice versa, or the axial direction can be understood as the height direction. From top to bottom, the direction of the upper section milling mechanism to the lower section milling mechanism, in this embodiment, the upper section milling mechanism is located above the lower section milling mechanism. The lower casing 1 is a housing for accommodating the driving assembly and the section milling part, and the upper casing 13 is also a housing for accommodating the auxiliary driving assembly and the auxiliary section milling part, both of which are open at both ends and have a hollow cavity inside.

[0054] Specifically, according to the functional division, the lower casing 1 can be divided into an upper cavity, a middle section milling part and a lower section milling part, the lower casing 1 has an upper end interface and a lower end interface, the upper end interface is connected with the upper joint 11, the upper end of the upper joint 11 is connected with the middle joint 16, and the middle joint 16 is connected with the lower end interface of the upper casing 13, thereby forming a two-stage section milling structure. The lower end interface is connected with the centralizer or the drill bit.

[0055] The section milling part and the auxiliary section milling part can be understood as the part that performs the section milling work, usually with a plurality of section milling cutters. The driving assembly and the auxiliary driving assembly are components responsible for providing the section milling power. A plurality of section milling openings are formed on the lower casing 1 at different positions, and the section milling part extends out through these section milling openings to perform section milling. In some embodiments, after completing the section milling work, the section milling part can be retracted into the section milling opening.

[0056] More specifically, the lower casing 1 has a through channel forming a lower flow passage 3-4 for the circulation of drilling fluid. The upper casing 13 has a through channel forming an upper flow passage. The sliding sleeve component can control the connection or disconnection of the upper and lower flow passages, so that the upper and lower stage milling mechanisms can be used for different downhole conditions, and the stage milling operation level can be switched as needed to adapt to different downhole operation requirements.

[0057] Specifically, when the lower stage milling mechanism needs to be used, the sliding sleeve component is in the initial state, the two flow passages are connected, the drilling fluid is transmitted to the lower flow passage 3-4 through the upper flow passage, and the drilling fluid pressure is provided to the driving assembly inside the cavity of the lower casing 1. The lower driving assembly works under the driving force of the drilling fluid, and drives the stage milling part to extend from the stage milling port to mill the downhole casing.

[0058] When the lower stage milling mechanism needs to be stopped and the upper stage milling mechanism needs to be used, the sliding sleeve component can control the two flow passages to be in a disconnected state, the drilling fluid will not be transmitted from the upper flow passage to the lower flow passage 3-4, and a pressure difference is formed inside the cavity of the upper casing 13. When a certain pressure difference is reached, the driving force of the drilling fluid is transmitted to the upper auxiliary driving assembly. The upper auxiliary driving assembly engages the auxiliary stage milling part to extend from the auxiliary stage milling port to perform auxiliary stage milling operation.

[0059] As a specific explanation of the embodiment, the sliding sleeve component includes a sliding sleeve 18, shear pins 18-1 and a ball 21. The sliding sleeve 18 has a ball seat, and the outer periphery of the sliding sleeve 18 is connected to the upper casing 13 by a plurality of shear pins 18-1. In the initial state, the sliding sleeve component is fixed to the upper casing 13 by the shear pins 18-1, and the ball 21 is not put into the ball seat of the sliding sleeve 18, at this time the drilling fluid flows from the upper casing 13 into the lower casing 1, and a pressure difference is formed in the lower casing 1. When the ball 21 is put into the ball seat, the two flow passages are disconnected, a pressure is formed in the upper casing 13, and the shear pins 18-1 are broken, and the sliding sleeve 18 slides down.

[0060] In this way, through the two-stage milling mechanism, the staged milling is completed in one trip, and after the lower stage milling mechanism loses the milling ability, the upper stage milling mechanism can continue to work, realizing continuous milling operation, without frequent tool replacement, reducing operation time and downtime. The upper and lower stage milling mechanisms are driven by independent driving assemblies and can be used for separate milling operations, reducing the number of trips during single trip milling operation, extending the length of one trip, saving milling time and reducing operation cost.

[0061] As a further explanation of the embodiment, please refer to Figure 3 and Figure 4 as shown, Figure 3The overall structure schematic diagram of the segment milling mechanism of the present application is shown. Figure 4 The overall structure schematic diagram of the upper segment milling mechanism of the present application is shown. As Figure 3 and Figure 4 The driving assembly includes an axially connected lower transmission piston 3 and a lower core shaft 2, and a lower flow channel 3-4 penetrates through the lower transmission piston 3 and the lower core shaft 2; the segment milling part includes a middle segment milling structure and a lower segment milling structure arranged axially and respectively located at a plurality of segment milling ports; wherein the lower core shaft 2 abuts against the middle segment milling structure and the lower segment milling structure; the auxiliary driving assembly includes an axially connected upper transmission piston 14 and an upper core shaft 15, and an upper flow channel penetrates through the upper transmission piston 14 and the upper core shaft 15; the auxiliary segment milling part includes at least one upper segment milling cutter 19 and is respectively located at at least one auxiliary segment milling port; wherein the upper core shaft 15 engages with each upper segment milling cutter 19.

[0062] In the embodiment, the lower segment milling mechanism includes a lower housing 1, a lower core shaft 2, a lower transmission piston 3, a middle segment milling structure and a lower segment milling structure. The side wall of the lower housing 1 is provided with a plurality of segment milling ports, and the middle segment milling structure and the lower segment milling structure are installed at the segment milling ports of the lower housing 1, and the middle segment milling structure is arranged above the lower segment milling structure. The upper end of the lower core shaft 2 is connected with the lower transmission piston 3, and the lower core shaft 2 and the lower transmission piston 3 are embedded in the internal cavity of the lower housing 1. The lower core shaft 2 abuts against the middle segment milling structure and the lower segment milling structure at the segment milling ports of the lower housing 1.

[0063] The upper segment milling mechanism includes an upper housing 13, an upper transmission piston 14, an upper core shaft 15, a sliding sleeve component and an upper segment milling cutter 19, the side wall of the upper housing 13 is provided with three auxiliary segment milling ports, and an equal number of upper segment milling cutters 19 are installed at the auxiliary segment milling ports of the upper housing 13, the upper end of the upper core shaft 15 is engaged with the upper segment milling cutter 19, the lower end is connected with the upper transmission piston 14, and the upper core shaft 15 and the upper transmission piston 14 are embedded in the internal cavity of the upper housing 13.

[0064] In some embodiments, the segment milling port can be a stepped through-hole structure. The auxiliary segment milling port can be a through-hole structure.

[0065] In some embodiments, the upper part of the lower housing 1 is provided with a lower piston guide groove 1-4, the lower transmission piston 3 is arranged in the lower piston guide groove 1-4, and the upper end of the lower piston guide groove 1-4 is connected to the upper joint 11; wherein the lower transmission piston 3 is provided with a flow distribution disc 3-2 and a nozzle 3-3, the lower end of the nozzle 3-3 is communicated with the corresponding flow channel; the lower part of the upper housing 13 is provided with an upper piston guide groove 13-1, the upper transmission piston 14 is arranged in the upper piston guide groove 13-1, and the lower end of the upper piston guide groove 13-1 is connected to the middle joint 16; wherein the upper joint 11 and the middle joint 16 are connected.

[0066] Specifically, the upper part of the lower housing 1 is provided with a lower piston guide groove 1-4, the upper end of the lower piston guide groove 1-4 is connected to the upper joint 11 through threading, the segment milling opening opened on the lower housing 1 is a stepped through-hole structure, the large-diameter end of the stepped through-hole is on the outer side of the lower housing 1, and the small-diameter end is on the inner side of the lower housing 1, and the connection between the large-diameter end and the small-diameter end of the segment milling opening forms a stepped surface.

[0067] Specifically, the lower transmission piston 3 is arranged in the lower piston guide groove 1-4, the side wall of the lower transmission piston 3 and the lower piston guide groove 1-4 is provided with a lower sealing ring 3-1, the top of the lower transmission piston 3 is provided with a flow distribution disc 3-2 and a nozzle 3-3, the lower transmission piston 3 is fixedly connected with the lower mandrel 2 by an integral molding method, and the lower end of the nozzle 3-3 is provided with the above-mentioned lower flow channel 3-4 penetrating the lower transmission piston 3 and the lower mandrel 2.

[0068] Specifically, the flow distribution disc 3-2 is arranged in the upper cavity of the lower housing 1, the flow distribution disc 3-2 is provided with four through holes communicated with the nozzles 3-3, and the nozzles 3-3 are arranged and installed in cooperation with the upper part of the lower transmission piston 3.

[0069] Specifically, the inner diameter of the lower piston guide groove 1-4 is greater than the outer diameter of the lower mandrel 2, and the outer wall of the lower transmission piston 3 is in transition fit with the inner wall of the lower piston guide groove 1-4, two sealing rings are installed on the outer contour of the lower transmission piston 3, the sealing rings are in close contact with the lower piston guide groove 1-4 in the lower housing 1, so as to prevent the drilling fluid from flowing into the middle segment milling structure and the lower segment milling structure in the lower housing 1.

[0070] More specifically, the upper housing 13 has an upper flow channel penetrating up and down, the lower part of the upper housing 13 is provided with an upper piston guide groove 13-1, the upper transmission piston 14 drives the upper mandrel 15 to slide up and down on the surface of the upper piston guide groove 13-1, the inner surface of the lower part of the upper housing 13 is processed with an internal thread surface, the middle joint 16 can be connected through threading, and the upper housing 13 is provided with four through holes uniformly distributed in the circumferential direction at the cooperation position with the gasket 20.

[0071] Specifically, the upper transmission piston 14 is arranged in the upper piston guide groove 13-1, the lower end of the upper piston guide groove 13-1 is connected to the middle joint 16 through screw connection, the auxiliary segment milling opening of the upper end of the upper housing 13 is a through hole structure, a threaded hole is arranged on the lower surface of the through hole, and the threaded hole is hinged with the positioning hole of the upper segment milling cutter 19; the upper sealing ring 14-1 is arranged on the side wall of the upper transmission piston 14 matched with the upper piston guide groove 13-1.

[0072] Specifically, the inner diameter of the upper piston guide groove 13-1 is greater than the outer diameter of the upper core shaft 15, the outer wall of the upper transmission piston 14 is in transition fit with the inner wall of the upper piston guide groove 13-1, and the outer contour of the upper transmission piston 14 is provided with two upper sealing rings 14-1, and the two upper sealing rings 14-1 are in close contact with the upper piston guide groove 13-1 of the upper housing 13.

[0073] In a preferred embodiment, the lower segment milling mechanism further comprises a lower reset assembly, and the upper segment milling mechanism further comprises an upper reset assembly; wherein the lower reset assembly comprises a lower spring 10 sleeved on the lower core shaft 2, the lower spring 10 is arranged in the lower piston guide groove 1-4, the top of the lower spring 10 abuts against the lower surface of the lower transmission piston 3, and the bottom of the lower spring 10 abuts against the stepped surface of the lower piston guide groove 1-4; the upper reset assembly comprises an upper spring 17 sleeved on the upper core shaft 15, the upper spring 17 is arranged in the upper piston guide groove 13-1, the bottom of the upper spring 17 abuts against the upper surface of the upper transmission piston 14, and the top of the upper spring 17 abuts against the stepped surface of the upper piston guide groove 13-1.

[0074] Specifically, the lower core shaft 2 is sleeved with the lower spring 10, the lower spring 10 is arranged in the lower piston guide groove 1-4, the top of the lower spring 10 abuts against the lower surface of the lower transmission piston 3, and the bottom of the lower spring 10 abuts against the stepped surface of the lower piston guide groove 1-4. The upper core shaft 15 is sleeved with the upper spring 17, the upper spring 17 is arranged in the upper piston guide groove 13-1, the bottom of the upper spring 17 abuts against the upper surface of the upper transmission piston 14, and the top of the upper spring 17 abuts against the stepped surface of the upper piston guide groove 13-1.

[0075] Therefore, when the lower segment milling mechanism completes the segment milling operation, the lower transmission piston 3 stops working. The lower spring 10 pushes the lower transmission piston 3 upward to reset under the elastic force until the top of the lower spring 10 abuts against the lower surface of the lower transmission piston 3 and the bottom abuts against the stepped surface of the lower piston guide groove 1-4, ensuring that the segment milling part returns to the initial position. When the upper segment milling mechanism completes the segment milling operation, the upper transmission piston 14 stops working. The upper spring 17 pushes the upper transmission piston 14 downward to reset under the elastic force until the bottom of the upper spring 17 abuts against the upper surface of the upper transmission piston 14 and the top abuts against the stepped surface of the upper piston guide groove 13-1, ensuring that the auxiliary segment milling part returns to the initial position. Thus, the reset assembly ensures that the segment milling device is quickly ready for the next segment milling operation, enabling continuous and efficient segment milling operation.

[0076] In some other embodiments, the plurality of segment milling ports are respectively the middle short cutter groove 1-1, the middle long cutter groove 1-2, and the lower cutter groove 1-3. The plurality of middle short cutter grooves 1-1 and the middle long cutter grooves 1-2 are evenly distributed in the middle section of the lower housing 1. The length of the middle short cutter groove 1-1 is less than that of the middle long cutter groove 1-2. The vertical lower end of the middle short cutter groove 1-1 and the middle long cutter groove 1-2 are located in the same horizontal plane. The plurality of lower cutter grooves 1-3 are evenly distributed in the lower section of the lower housing 1. Thus, the stability of the extension and retraction of the middle segment milling mechanism and the lower segment milling mechanism is ensured.

[0077] Further, please refer to Figures 5-7 shown, Figure 5 is a whole structure diagram of the middle short segment cutter 4; Figure 6 is a whole structure diagram of the middle long segment cutter 6; Figure 7 is a whole structure diagram of the lower segment cutter 8. The middle segment milling structure is composed of the middle short segment milling structure and the middle long segment milling structure. The middle short segment milling structure is composed of the middle short segment cutter 4 and the middle short cutter holder 5. The middle short cutter holder 5 is connected to the stepped surface of the middle short cutter groove 1-1 through a bolt, and the middle short end cutter is hinged to the middle short cutter holder 5 through a positioning shaft 12. The middle long segment milling structure is composed of the middle long segment cutter 6 and the middle long cutter holder 7. The middle long segment cutter 6 is connected to the stepped surface of the middle long cutter groove 1-2 through a bolt, and the middle long segment cutter 6 is hinged to the middle long cutter holder 7 through a positioning shaft 12. The length of the middle short segment cutter 4 is less than that of the middle long segment cutter 6.

[0078] More specifically, the lower segment milling structure is composed of the lower segment cutter 8 and the lower cutter holder 9. The lower cutter holder 9 is connected to the stepped surface of the lower cutter groove 1-3 through a bolt, and the lower segment cutter 8 is hinged to the lower cutter holder 9 through a positioning shaft 12.

[0079] Specifically, the middle short tool holder 5, the middle long tool holder 7 and the lower tool holder 9 all adopt an integral structure which is integrally machined and formed. The integral structure can reduce roughness and has higher strength and rigidity.

[0080] It can be understood that, since the middle short tool holder 5 and the middle long tool holder 7 of the middle section milling mechanism have different heights, the lengths of the section milling cutters matched therewith are also different, and the heights of the positioning shafts 12 installed on the middle short tool holder 5 and the middle long tool holder 7 are also different. Therefore, the rotation radii of the middle short section milling cutter 4 and the middle long section milling cutter 6 matched with the positioning shafts 12 on the middle short tool holder 5 and the middle long tool holder 7 are also different. Preferably, the rotation radius of the middle short section milling cutter 4 is smaller than the rotation radius of the middle long section milling cutter 6. In this way, the integral tool holder and the section milling cutter are simple to disassemble and assemble, and can meet the section milling requirements of different construction conditions.

[0081] In a further technical solution, the back of the middle short section milling cutter 4 is provided with a first reset hook and a first curved edge 4-2. The handle of the middle short section milling cutter 4 is provided with a first positioning hole 4-5 which is matched with the positioning shaft 12. Specifically, the back of the middle long section milling cutter 6 is provided with a second reset hook 6-1 and a second curved edge 6-2, and the handle of the middle long section milling cutter 6 is provided with a second positioning hole 6-5 which is matched with the positioning shaft 12. Specifically, the back of the lower section milling cutter 8 is provided with a third reset hook 8-1 and a third curved edge 8-2, and the handle of the lower section milling cutter 8 is provided with a third positioning hole 8-5 which is matched with the positioning shaft 12.

[0082] In the present embodiment, the lower core shaft 2 is provided with a middle boss 2-1 and a lower boss 2-2 which are annular and are machined on the outer profiles of the middle section and the lower section matched with the lower shell 1. The first reset hook and the first curved edge 4-2, the second reset hook 6-1 and the second curved edge 6-2, and the third reset hook 8-1 and the third curved edge 8-2 are embedded in the middle boss 2-1 and the lower boss 2-2 respectively.

[0083] Therefore, the middle boss 2-1 and the lower boss 2-2 of the lower core shaft 2 slide downward and abut against the first curved edge 4-2, the second curved edge 6-2 and the third curved edge 8-2 respectively, so that the middle short section milling cutter 4, the middle long section milling cutter 6 and the lower section milling cutter 8 rotate outward of the lower shell 1 around the positioning shaft 12.

[0084] The middle boss 2-1 and the lower boss 2-2 of the lower core shaft 2 slide upward to abut against the first reset hook 6-1 and the third reset hook 8-1 respectively, so that the middle short section mill 4, the middle long section mill 6 and the lower section mill 8 rotate the positioning shaft 12 to the inside of the lower casing 1. In this way, all the section mills in the lower section milling mechanism are connected with the corresponding integrated tool holder, and the hook design ensures the initial state of the section mill to be stable when the section mill is lowered into the well and the smooth recovery of the section mill after the completion of the construction.

[0085] In a preferred embodiment, the blade surface of the middle short section mill 4 is provided with a first cutting edge 4-3 and a first milling edge 4-4. The blade surface of the middle long section mill 6 is provided with a second cutting edge 6-3 and a second milling edge 6-4. The blade surface of the lower section mill 8 is provided with a third cutting edge 8-3 and a third milling edge 8-4. In this embodiment, the first cutting edge 4-3, the second cutting edge 6-3 and the third cutting edge 8-3 are located on the outer side and can be used to quickly cut off the casing, and the first milling edge 4-4, the second milling edge 6-4 and the third milling edge 8-4 are located on the inner side and can normally mill the casing downward after the cutting edge is preliminarily processed. Therefore, the embodiment of the present application can operate by using the boss on the lower core shaft 2 to push the section mill outward, and the two section milling structures can simultaneously operate with 12 section mills, and two types of tungsten carbide teeth are designed for the cutting and milling states of the casing, thereby enhancing the cutting ability of the teeth.

[0086] In another preferred embodiment, the milling edge adopts an inner concave tooth, which is beneficial to cutting the long iron wire formed and preventing the iron filings from being wound.

[0087] In some embodiments, the working radius of the blade surface of the section mill in the middle section milling structure and the lower section milling structure can be different, and the two layers of section mills can simultaneously participate in the section milling operation.

[0088] In a further technical solution, a step is machined on the outer circumferential surface of the upper end of the upper core shaft 15, and the step surface is provided with a rack which is engaged with a gear of the upper section mill 19. In some embodiments, the gear on the upper section mill 19 is an incomplete gear which is directed to the side where the rack is located. When the lower section milling mechanism loses the section milling ability, the upper section milling mechanism is used to work, and the upper section mill 19 is rotated and extended by the engagement of the rack on the upper core shaft 15 with the incomplete gear on the upper section mill 19, so that the casing and the cement sheath can be simultaneously milled, thereby improving the cutting efficiency and the section milling efficiency.

[0089] Specifically, when the lower section milling tool loses the section milling ability, the drilling tool is lifted, the ball 21 is put into the well to a specific position to open the upper section milling device, and the upper section milling device participates in the section milling operation after being completely opened. The specific implementation of the embodiment is as follows:

[0090] The sliding sleeve component comprises a sliding sleeve 18, a shear pin 18-1 and a ball 21, the upper end of the sliding sleeve 18 is in abutment with the upper transmission piston 14 and movably embedded in the grommet 20, a ball seat is formed in the sliding sleeve 18, the outer periphery of the sliding sleeve 18 is connected with the upper shell 13 through a plurality of shear pins 18-1, wherein the ball seat is used for receiving the ball 21 to block the flow channel of the lower shell 1, the shear pins 18-1 are sheared under the pressure of the drilling fluid to make the sliding sleeve 18 slide downward, the drilling fluid pushes the upper transmission piston 14 to drive the upper mandrel 15 to slide upward and mesh with the auxiliary section milling part.

[0091] Specifically, the upper end of the upper transmission piston 14 is connected with the upper end of the sliding sleeve 18, the outer surface of the upper end of the sliding sleeve 18 is in abutment with the stepped hole of the inner surface of the upper transmission piston 14, the lower end outer surface is matched with the inner surface of the grommet 20, and the shear pin 18-1 can slide up and down along the inner surface after being sheared, so as to slide from the initial position to the terminal position. Four shear pins 18-1 are machined on the outer surface of the sliding sleeve 18 and matched with four through holes formed in the lower end of the upper shell 13. A ball seat is machined on the inner surface of the sliding sleeve 18, and the ball 21 can fall into the ball seat after being put in. The ball 21 blocks the lower flow channel 3-4 in the ball seat, so that the drilling fluid forms pressure in the lower cavity of the upper shell 13.

[0092] In summary, the specific operation principle of an embodiment of the present application is as follows:

[0093] When the pump is pressurized, the drilling fluid flows from the inlet to the shunt disc 3-2 in the upper cavity of the lower shell 1, and the shunt disc 3-2 divides the flow of the drilling fluid and acts on the upper side of the lower transmission piston 3. When a certain pressure is reached, the drilling fluid drives the lower transmission piston 3 to drive the lower mandrel 2 to slide downward in the cavity of the lower shell 1. At this time, the lower spring 10 sleeved on the lower mandrel 2 is compressed under the extrusion of the lower surface of the lower transmission piston 3.

[0094] In the process of sliding of the lower mandrel 2, the middle boss 2-1 embedded between the first reset barb 4-1 and the first curved edge 4-2 and between the second reset barb 6-1 and the second curved edge 6-2 starts to push the middle short section milling cutter 4 and the middle long section milling cutter 6 out of the outer side of the middle short cutter groove 1-1 and the middle long cutter groove 1-2 along the curved edge contour, and the lower boss 2-2 embedded between the third reset barb 8-1 and the third curved edge 8-2 starts to push the lower section milling cutter 8 out of the outer side of the lower cutter groove 1-3 along the curved edge contour. When the middle boss 2-1 and the lower boss 2-2 are tangent to the curved edge vertices of the first curved edge 4-2, the second curved edge 6-2 and the third curved edge 8-2, the lower section milling cutter 8 gradually penetrates into the casing wall until it is opened to the maximum working radius, and the middle short section milling cutter 4 and the middle long section milling cutter 6 gradually expand to the maximum limited position after cutting the casing, at this time the lower section milling cutter has completed the cutter extension.

[0095] When the segment milling work is performed for a certain period of time, and it is judged that the lower segment milling mechanism loses the segment milling ability according to the cuttings, the ball 21 is put into the well. The drilling fluid passes through the upper transmission piston 14 inside the upper shell 13 from the inner cavity of the upper shell 13 to the upper part of the sliding sleeve 18, the diameter of the ball 21 is larger than the inner diameter of the ball seat inside the sliding sleeve 18, under the action of mud pressure, the shear pin 18-1 is broken, and the sliding sleeve 18 slides downward to the groove of the middle joint 16. The lower cavity of the upper shell 13 forms a pressure, when a certain pressure is reached, the drilling fluid pushes the upper transmission piston 14 to drive the upper mandrel 15 to slide upward in the cavity of the upper shell 13, and drives the upper segment milling cutter 19 through the gear and rack engagement, and the upper segment milling cutter 19 rotates outward. At this time, the upper spring 17 sleeved on the upper core is compressed downward under the extrusion of the upper surface of the upper transmission piston 14, until the upper mandrel 15 reaches the limited position inside the upper shell 13, at this time, the upper segment milling cutter has completed the cutter extension.

[0096] Then the drilling tool is pulled up to apply the weight on bit to perform the casing segment milling construction, the outer diameter of the upper segment milling mechanism when opened is larger than the working outer diameter of the lower segment milling mechanism, and the casing and more cement rings can be milled. After the construction is completed, the segment milling device is lowered by a certain distance, and the mud pump is stopped first. After the pressure drop disappears, the lower transmission piston 3 drives the lower mandrel 2 to reset under the action of the lower spring 10, the upper ends of the middle boss 2-1 and the lower boss 2-2 on the lower mandrel 2 abut against the first reset barb 4-1, the second reset barb 6-1 and the third reset barb 8-1, drive each segment milling cutter in the lower segment milling mechanism to rotate reversely around the positioning hole, and gradually restore the contraction state until the segment milling port is retracted. The upper transmission piston 14 drives the upper mandrel 15 to reset under the action of the upper spring 17, rotates through the gear and rack engagement, and the upper segment milling cutter 19 rotates inward to the retracted auxiliary segment milling port.

[0097] Finally, the rotary table is closed, and the drilling operation is performed.

[0098] It should be noted that each of the embodiments in the specification adopts a progressive manner for description, and each embodiment focuses on the difference from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0099] It also needs to be explained that, in this article, the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, relationship terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations, nor can it be understood as indicating or implying relative importance. Moreover, the term "includes" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed or inherent to such a process, method, article or terminal device.

[0100] The above describes in detail a two-stage segment milling device for downhole casing provided by the present application, and the principles and implementation modes of the present application are described by applying specific examples. The above example description is only used to help understand the present application, and the content of the description should not be understood as a limitation on the present application. Meanwhile, for those skilled in the art, according to the present application, there will be different forms of changes in specific implementation modes and application ranges, and here it is not necessary and also impossible to exhaust all the implementation modes, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A two-stage section milling device for a downhole casing, characterized by, The application relates to a downhole casing mill, which comprises an upper-stage milling mechanism and a lower-stage milling mechanism connected axially, wherein the lower-stage milling mechanism comprises a lower-stage housing, a driving assembly and a milling section in the lower-stage housing, a plurality of milling openings are formed in the lower-stage housing, and the driving assembly is in movable abutment with the milling section; the upper-stage milling mechanism comprises an upper-stage housing, an auxiliary driving assembly and an auxiliary milling section in the upper-stage housing, at least one auxiliary milling opening is formed in the upper-stage housing, and the auxiliary driving assembly is in engagement with the auxiliary milling section; the inner parts of the upper-stage housing and the lower-stage housing are respectively provided with flow channels, the lower-stage milling mechanism opens or disconnects the communication of the two flow channels through a sliding sleeve component; so that: when the two flow channels are in communication, drilling fluid transmits driving force to the driving assembly, the driving assembly drives the milling section to extend out of the milling opening to mill downhole casing; when the lower-stage milling mechanism stops milling the downhole casing, the two flow channels are disconnected through the sliding sleeve component, drilling fluid transmits driving force to the auxiliary driving assembly, the auxiliary driving assembly engages and drives the auxiliary milling section to rotate and extend out of the auxiliary milling opening to enhance the milling of the downhole casing. The driving assembly comprises a lower-stage transmission piston and a lower-stage mandrel connected axially, the flow channels pass through the lower-stage transmission piston and the lower-stage mandrel; the milling section comprises a middle milling structure and a lower milling structure arranged axially and respectively located at the milling openings; the lower-stage mandrel is in abutment with the middle milling structure and the lower milling structure; the auxiliary driving assembly comprises an upper-stage transmission piston and an upper-stage mandrel connected axially, the flow channels pass through the upper-stage transmission piston and the upper-stage mandrel; the auxiliary milling section comprises at least one upper-stage milling cutter and is respectively located at the auxiliary milling opening; the upper-stage mandrel is in engagement with each upper-stage milling cutter. The upper part of the lower-stage housing is provided with a lower-stage piston guide groove, the lower-stage transmission piston is arranged in the lower-stage piston guide groove, and the upper end of the lower-stage piston guide groove is connected with an upper joint; the lower-stage transmission piston is provided with a flow distribution disc and a nozzle, and the lower end of the nozzle is in communication with the corresponding flow channel; the lower part of the upper-stage housing is provided with an upper-stage piston guide groove, the upper-stage transmission piston is arranged in the upper-stage piston guide groove, and the lower end of the upper-stage piston guide groove is connected with a middle joint; the upper joint and the middle joint are connected. The lower-stage milling mechanism further comprises a lower-stage reset assembly, and the upper-stage milling mechanism further comprises an upper-stage reset assembly; the lower-stage reset assembly comprises a lower-stage spring sleeved on the lower-stage mandrel, the lower-stage spring is arranged in the lower-stage piston guide groove, the top of the lower-stage spring is in abutment with the lower surface of the lower-stage transmission piston, and the bottom of the lower-stage spring is in abutment with the stepped surface of the lower-stage piston guide groove; the upper-stage reset assembly comprises an upper-stage spring sleeved on the upper-stage mandrel, the upper-stage spring is arranged in the upper-stage piston guide groove, the top of the upper-stage spring is in abutment with the lower surface of the upper-stage transmission piston, and the bottom of the upper-stage spring is in abutment with the stepped surface of the upper-stage piston guide groove. ​ ​ 2. A two-stage section mill apparatus for use with a downhole casing as defined in claim 1, wherein, ​ ​ 3. A two-stage section mill apparatus for use with a downhole casing as defined in claim 2, wherein, ​ ​ ​ 4. A two-stage section mill apparatus for use with a downhole casing as defined in claim 3, wherein, ​ ​ The lower reset assembly comprises an upper spring sleeved on the upper core shaft, the upper spring is installed in the upper piston guide groove, the bottom of the upper spring abuts against the upper surface of the upper transmission piston, and the top abuts against the stepped surface of the upper piston guide groove.

5. A two-stage section mill apparatus for use with a downhole casing as defined in claim 2, wherein, The segment milling port is a stepped through-hole structure, the large-diameter end of the through-hole structure is close to the outer side of the lower housing, the small-diameter end is located at the inner side of the lower housing, and the connection between the large-diameter end and the small-diameter end forms a stepped surface. The plurality of segment milling ports are respectively middle short cutter grooves, middle long cutter grooves and lower cutter grooves; the plurality of middle short cutter grooves and the middle long cutter grooves are cross-distributed in the middle section of the lower housing and accommodate the middle section milling structure; and the plurality of lower cutter grooves are uniformly distributed in the lower section of the lower housing and accommodate the lower section milling structure.

6. A two-stage section mill apparatus for use with a downhole casing as defined in claim 5, wherein, The middle section milling structure comprises a middle short section milling structure and a middle long section milling structure. The middle short section milling structure is composed of a middle short section milling cutter and a middle short cutter holder, the middle short cutter holder is connected with the stepped surface of the middle short cutter groove, and the middle short section milling cutter is hinged with the middle short cutter holder. The middle long section milling structure is composed of a middle long section milling cutter and a middle long cutter holder, the middle long section milling cutter is connected with the stepped surface of the middle long cutter groove, and the middle long section milling cutter is hinged with the middle long cutter holder. The lower section milling structure is composed of a lower section milling cutter and a lower cutter holder, the lower cutter holder is connected with the stepped surface of the lower cutter groove, and the lower section milling cutter is hinged with the lower cutter holder.

7. A two-stage section-milling device for a downhole casing according to claim 6, characterized in that The lower core shaft is provided with a middle boss and a lower boss at positions corresponding to the middle section and the lower section of the lower housing; the middle short section milling cutter, the middle long section milling cutter and the lower section milling cutter are respectively provided with a cutting edge and a milling edge on the blade surface, and the cutting edge is located at the outer side. The back surface of the middle short section milling cutter is provided with a first reset barb and a first curved edge; The back surface of the middle long section milling cutter is provided with a second reset barb and a second curved edge; The back surface of the lower section milling cutter is provided with a third reset barb and a third curved edge; The outer edge contour formed by the connection of the first reset barb and the first curved edge, the outer edge contour formed by the connection of the second reset barb and the second curved edge are matched with the outer edge contour of the middle boss; and the outer edge contour formed by the connection of the third reset barb and the third curved edge is matched with the outer edge contour of the lower boss.

8. A two-stage section mill apparatus for use with a downhole casing as defined in claim 2, wherein, The upper section of the upper core shaft is provided with a step, and the outer side of the step is provided with a rack; The upper section milling cutter is hinged with the auxiliary segment milling port, and the side facing the step is provided with a gear meshing with the rack.

9. A two-stage section mill apparatus for use with a downhole casing as defined in claim 6, wherein, The blade surface of the middle short section milling cutter, the middle long section milling cutter and the lower section milling cutter is respectively provided with a cutting edge and a milling edge, and the cutting edge is located at the outer side.

10. A two-stage section mill apparatus for use with a downhole casing as defined in claim 2, wherein, The sliding sleeve component comprises a sliding sleeve, a shear pin and a ball, the upper end of the sliding sleeve abuts against the upper transmission piston and is movably embedded in a grommet; a ball seat is formed in the sliding sleeve, and the outer periphery of the sliding sleeve is connected with the upper housing through a plurality of shear pins; The ball seat is used for receiving the ball to block the flow channel of the lower casing to shear the shear pin under the pressure of the drilling fluid to make the sliding sleeve slide down, the upper transmission piston is pushed by the drilling fluid to drive the upper core shaft to slide up to engage with the auxiliary section milling part.

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