Hydraulic ball centralizer and method for drilling and grinding cement plug in casing pipe

Abstract

The invention discloses a hydraulic ball centralizer and a drilling and grinding method for a cement plug in a casing pipe, specifically, a drilling and grinding tool is always centered in the rotating process through the hydraulic ball centralizer, and the situation that when the drilling and grinding tool deviates in a shaft, a window opening accident is easily caused on the casing pipe is avoided; meanwhile, a scrap returning channel is arranged on the hydraulic ball centralizer, and scrap blocking accumulated in the drilling process is eliminated, so that the drilling speed is increased, and the purpose of improving the drilling and grinding construction efficiency is achieved; in addition, by optimizing a construction pipe column structure, selecting and matching a drill collar and the like to increase a counter weight, the problems that drilling footage is slow due to the fact that drilling pressure cannot be applied when a cement plug is shallow, and a tool is blocked by chippings in the drilling and grinding process are solved; the drilling and grinding method is an optimized technological method, efficient and low-damage drilling and grinding of the cement plug of the long well section in the large cased well pipe of the gas storage are achieved, and therefore experience and a method for treating the well are provided for an oil field.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of oilfield downhole workover operation, in particular to a long-section cement plug drilling and grinding process method in a large casing wellbore. BACKGROUND

[0002] In recent years, in the treatment of gas storage wells, there are wells with technical casing or other non-5.5-inch conventional casing as production casing. Such wells usually have long cement plugs or even dropped objects in the well section, and need to be treated and re-sealed according to the gas storage standard, which requires efficient drilling and grinding of the cement plug in the well section without damaging the casing.

[0003] In Daqing Oilfield, the conventional production casing is 5.5-inch casing. When there is a cement plug in the wellbore that needs to be drilled out, the drilling and grinding tool + drilling tool method is usually used for construction. However, when the cement plug is shallow, it is difficult to add drilling pressure, resulting in slow footage, and the tool is blocked by debris during drilling and grinding. In addition, when the wellbore is offset, the drilling and grinding are prone to windowing. SUMMARY

[0004] Therefore, the present disclosure provides a hydraulic ball centralizer and a cement plug drilling and grinding method in a casing to solve the problems of low drilling and grinding efficiency and easy windowing of the cement plug in the casing.

[0005] To achieve the above-mentioned purposes, in a first aspect, the hydraulic ball centralizer comprises: a body and a piston sleeve connected with the drilling and grinding tool, and a reset spring arranged between the body and the piston sleeve; a centralizing ball arranged on the body and a spiral groove serving as a drilling and grinding debris flowback channel, and a groove arranged on the surface of the piston sleeve, wherein the side wall of the groove is a slope structure; In the initial state, based on the groove, the centralizing ball is retracted in the body; under the action of hydraulic pressure, the piston sleeve drives the centralizing ball to move outward through the slope structure to protrude from the surface of the body, and then the drilling and grinding tool is centered in the casing.

[0006] In the present disclosure and possible embodiments, a sealing element is arranged between the body and the piston sleeve, and the sealing element comprises an upper sealing rubber ring and a lower sealing rubber ring.

[0007] In the present disclosure and possible embodiments, an elastic retainer ring is arranged above the piston sleeve in the assembly of the piston sleeve and the body.

[0008] In the present disclosure and possible embodiments, a mounting groove is provided on the wall of the body, a ball seat is fixed in the mounting groove, and the centralizing ball is mounted through the ball seat.

[0009] In a second aspect, the cement plug drilling and grinding method in a casing comprises: The drill and mill tool is connected to the hydraulic ball centralizer of any one of the first aspect, and the drill and mill tool is used to drill and mill the cement plug in the casing.

[0010] The assembly of the piston sleeve and the body, and the drill collar connected to the service string composed of the drill and mill tool and the hydraulic ball centralizer.

[0011] The assembly of the piston sleeve and the body, and the casing mill barrel and / or the fishing cup connected to the service string.

[0012] The assembly of the piston sleeve and the body, and the service displacement is greater than or equal to 1.5 m 3 / min when the drill and mill tool is used to drill and mill the cement plug in the casing.

[0013] The assembly of the piston sleeve and the body, and the drill pressure is controlled to be 40-80 kN and the rotation speed is controlled to be 60-110 r / min when the drill and mill tool is used to drill and mill the cement plug in the casing.

[0014] The assembly of the piston sleeve and the body, and the drilling is performed, the casing is drilled once every 3-5 m, the casing is drilled twice after the single string is drilled, and the pump is stopped after the workover fluid is circulated at least once.

[0015] The present application has the beneficial effects: The cement plug drilling and milling method in the casing of the present disclosure uses the hydraulic ball centralizer to keep the drill and mill tool centered during rotation, avoiding the occurrence of windowing accidents on the casing when the drill and mill tool deviates in the wellbore; at the same time, the chip return channel is arranged on the hydraulic ball centralizer to remove the accumulated debris during drilling, thereby improving the drilling speed and achieving the purpose of improving the drilling and milling construction efficiency; in addition, by optimizing the structure of the service string and selecting the drill collar and other weight blocks, the problem of slow footage caused by the inability to add drill pressure when the cement plug is shallow and the tool jamming caused by debris during drilling and milling is solved; the drilling and milling method of the present application is an optimized process method, which realizes efficient and low-damage drilling and milling of the long cement plug in the casing of the large casing well of the gas storage, thereby providing experience and methods for the oil field to manage such wells. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which: Figure 1 is a structural schematic diagram of the hydraulic ball centralizer of the embodiment of the present disclosure; In the figure: 1-body, 2-elastic retainer, 3-upper sealing rubber ring, 4-centralizing ball, 5-ball seat, 6-piston sleeve, 7-return spring, 8-lower sealing rubber ring. DETAILED DESCRIPTION

[0017] The present disclosure is described in detail based on specific embodiments below, but it is worth noting that the present disclosure is not limited to these specific embodiments. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure without detailed description.

[0018] Meanwhile, unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and like terms are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

[0019] In order to solve the problem of the drilling and grinding process in the background art, the drilling and grinding method provided by the present application solves it through two aspects, specifically: first, by designing a ball centralizing device to keep the drilling and grinding tool centered during rotation, to avoid the occurrence of windowing accidents on the casing when the drilling and grinding tool deviates in the wellbore; at the same time, a chip return channel is provided on the ball centralizing device, which can return the chips in time during the drilling and grinding process, to remove the obstacles in the drilling and grinding tool drilling process, thereby improving the drilling speed and achieving the purpose of improving the drilling and grinding construction efficiency; the second aspect is to optimize the construction string structure and select and match drill collars to increase the weight, so as to solve the problem of slow footage caused by the inability to add drilling pressure when the cement plug is shallow, and the problem of continuous rotation of the tool during drilling and grinding; therefore, the drilling and grinding method of the present application is an optimized process method formed on the basis of the existing drilling and grinding process through the above two aspects of improvement, so as to better complete the efficient and low-damage drilling and grinding treatment of the cement plug in the long well section of the large casing well of the gas storage. EMBODIMENT

[0020] To implement the method of the present application, in the embodiments of the present disclosure, the ball centralizing device is a hydraulic ball centralizer, as shown in Figure 1 The hydraulic ball centralizer comprises a body 1 and a piston sleeve 6, and a return spring 7 is arranged between the body 1 and the piston sleeve 6; a mounting groove is opened on the outer wall of the body 1, a ball seat 5 is assembled through the mounting groove, and a centralizing ball 4 is assembled through the ball seat 5; at the same time, a recess is opened on the outer wall of the piston sleeve 6 corresponding to the centralizing ball 4, and the recess has a slope structure; in addition, a helical groove structure is arranged on the outer wall of the body 1, and the debris generated during the drilling process of the drilling and grinding tool can be returned through the helical groove structure, to prevent the drill pipe from being stuck, and also to assist in avoiding the slow footage during drilling and the continuous rotation of the tool during drilling and grinding.

[0021] The working process of this hydraulic ball centralizer is as follows: When the drilling string is lowered into the well, the inner side of the centralizing ball 4 is positioned within the groove of the piston sleeve 6, allowing the outer side of the centralizing ball 4 to be flush with the outer wall of the body 1, thus ensuring that the body 1 can be smoothly lowered into the well. When drilling operations are required, in order to ensure that the drilling tool remains centered throughout the operation, hydraulic pressure is applied to the piston sleeve 6 from the wellhead. The hydraulic pressure pushes the piston sleeve 6 downward while simultaneously compressing the return spring 7. As the piston sleeve 6 descends, the groove utilizes its inclined surface structure to... A lateral thrust is applied to the centering ball 4, which drives the centering ball 4 to move radially outward within the ball seat 5 and protrude from the body 1 to achieve the centering function. When the drilling process ends and the pump stops, the hydraulic pressure disappears, the spring force of the return spring 7 resets and pushes the piston sleeve 6 upward, the lateral thrust disappears, and the centering ball 4 resets and retracts into the body 1. Therefore, this ball bearing centering device achieves the centering function through the protrusion and retraction of the centering ball 4, and effectively avoids the phenomenon of friction damage to the casing that may occur during the raising and lowering of conventional centering devices.

[0022] In this embodiment of the present disclosure, an upper sealing ring 3 and a lower sealing ring 8 are respectively disposed on the upper and lower parts between the body 1 and the piston sleeve 6; and an elastic retaining ring 2 is disposed in the inner cavity of the body 1 above the piston sleeve 6 to limit the piston sleeve 6.

[0023] Taking a long section of cement plug inside a large casing well in a gas storage facility in Daqing as an example, this paper specifically illustrates the process of drilling and grinding the cement plug using the method of this invention. The casing specification is φ244.5mm. The specific steps are as follows: 1. Preparation of construction data: Obtain data on the casing structure, dimensions, steel grade, and wall thickness, cement return height, well inclination, previous construction status, current well string, and formation lithology within the casing well to be constructed.

[0024] 2. Construction site preparation: Sufficient well-working fluid was stored at the construction site, and well control equipment that met the pressure rating was installed.

[0025] 3. Preparation of construction tools: (1) Tool selection: The drilling tools should be selected according to the size of the casing produced in the well. When selecting drilling tools, it is required that the tools have inner chamfers on the edges and that the outer side of the milling teeth is not covered with tungsten steel. The purpose is to protect the casing by keeping the tools smooth and to avoid accidents such as casing opening during drilling operations.

[0026] (2) Construction pipe column structure design: In this embodiment, the main idea of ​​the tubing column structure design is to ensure the tubing column is centered by milling and adding a stabilizer, and to add a drill collar to prevent the casing from opening due to tool head swing during milling. Because the difficulty of drilling and milling varies on site, it is necessary to design tubing column structure schemes for different site conditions. The specific tubing column structure design scheme is as follows: ① Drilling tools + φ216mm hydraulic ball bearing stabilizer + φ139.7mm short sleeve milling cylinder + φ216mm hydraulic ball bearing stabilizer + 139.7mm sleeve milling cylinder.

[0027] ② Drilling tools + φ220mm hydraulic ball bearing stabilizer + φ210mm fishing cup + φ139.7mm milling sleeve short section + 216mm hydraulic ball bearing stabilizer + φ139.7mm milling sleeve.

[0028] ③ Drilling tools + φ220mm hydraulic ball bearing stabilizer + φ210mm fishing cup + φ165mm drill collar + φ220mm hydraulic ball bearing stabilizer + φ165mm drill collar + φ220mm hydraulic ball bearing stabilizer + φ165mm drill collar × 2 + φ127mm drill rod.

[0029] In the above-mentioned tubular structure design scheme, the drilling tools, milling sleeve short section, milling sleeve, fishing cup, drill collar and drill rod can be tools commonly used in the art.

[0030] (3) Construction parameter design: In this embodiment of the disclosure, the designed construction discharge volume is ≥1.5m³. 3 / min, to ensure sufficient cooling of the drilling part during the drilling process, and at the same time return the drilling debris to the wellhead to avoid the drill bit getting stuck; according to the conventional technology in this field, the torque is generally constant during drilling. On-site, the torque parameters of the equipment can be used to judge in time whether there is a jamming phenomenon in the tubing. When the torque increases, the displacement should be increased and vigilance should be maintained. When drilling cement plugs, safety measures such as "one step forward and two steps back, one step forward and three steps back" should be implemented to prevent cement blocks from jamming the drill bit.

[0031] The design drilling pressure is 40-80 kN. If the drilling pressure is too low, the drilling efficiency will decrease, and if the drilling pressure is too high, the drill may get stuck during the drilling process. Therefore, it is necessary to select an appropriate drilling pressure. The design rotation speed is 60-110 r / min. An appropriate drilling speed can ensure that the cement plug is thoroughly drilled and ground. During construction, operators can adjust the above construction parameters appropriately based on the conventional techniques in the field and the size of the chips returned on site and the speed of the advance, in order to determine the optimal construction parameters. If the chips return is large, the drilling speed and drilling pressure should be reduced and the displacement should be increased; if the advance is slow, the drilling pressure and drilling speed should be increased.

[0032] (4) Drilling and grinding construction: ① In this embodiment of the present disclosure, in accordance with the conventional techniques in the art, a suitable drilling string is selected. When the drill string is lowered to a distance of approximately 5m from the cement plug, the workover fluid is first circulated in the forward direction. After the circulating fluid reaches the bottom of the well and circulates normally, the flow rate is increased. During normal drilling, the drilling pressure is maintained, and drilling is carried out evenly and steadily.

[0033] ② During the drilling process, reaming is performed once every 3-5 meters of drilling. After drilling a single section, the reaming is performed twice by lifting and lowering the drill bit. The pump is stopped after the workover fluid has circulated for at least one cycle.

[0034] ③The following are the precautions for construction operations: a) Control drilling pressure to prevent excessive milling; use drop milling as the primary method.

[0035] b) Determine parameters such as the drilling speed and penetration rate for cement grinding. If changes in these parameters result in casing cutting, promptly print out and document the downhole milling status to prevent casing cutting.

[0036] c) Do not mill in the same spot for an extended period of time. If milling does not yield any progress after a long period of time, the drilling string should be removed to check the wear of the drilling tools, and the downhole conditions should be recorded.

[0037] d) If the amount of returned iron filings increases sharply during the milling process, the construction pipe column should be removed to determine whether a casing opening accident has occurred.

[0038] e) A stopcock valve should be connected to the lower part of the square drill pipe.

[0039] In addition, to date, the drilling and milling techniques disclosed herein have also been successfully applied to the treatment of wells Shengshen 2 and Shengshen 2-1 within the Shengping gas storage area, including: Sheng Shen 2 Well: The drilling progress was slow in the early stage. By applying the low-damage drilling technology for long sections of large casing wells disclosed in this paper, the drilling speed reached 10m / d and the well was successfully and efficiently drilled to 1967m without causing any damage to the casing. The well was completed and successfully treated according to the expert group's opinion.

[0040] Sheng Shen 2-1 Well: The low-damage drilling and milling process for long sections inside the casing of the gas storage large casing well was applied. The well was drilled and milled to 502m without damaging the casing. The well was successfully completed and treated according to the expert group's opinion.

[0041] The application of the above two wells showed a 100% success rate, fully demonstrating that the casing cement plug drilling and grinding process disclosed herein can provide oilfields with experience and methods for managing this type of well.

[0042] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A hydraulic ball bearing stabilizer, characterized in that, include: A body (1) and a piston sleeve (6) connected to a drilling tool, wherein a return spring (7) is disposed between the body (1) and the piston sleeve (6). The main body (1) is provided with a centering ball (4) and a spiral groove as a channel for the return of drilling and grinding debris. The piston sleeve (6) is provided with a groove on its surface, and the sidewall of the groove is a sloping structure. In the initial state, based on the groove, the centering ball (4) is retracted inside the body (1); under hydraulic action, the piston sleeve (6) drives the centering ball (4) to move outward through the inclined structure to protrude from the surface of the body (1), thereby centering the drilling tool inside the sleeve.

2. The hydraulic ball bearing centralizer according to claim 1, characterized in that: A sealing element is provided between the body (1) and the piston sleeve (6), the sealing element including an upper sealing ring (3) and a lower sealing ring (8).

3. The hydraulic ball bearing centralizer according to claim 2, characterized in that: Within the assembly of the piston sleeve (6) and the body (1), an elastic retaining ring (2) is disposed above the piston sleeve (6).

4. The hydraulic ball bearing stabilizer according to any one of claims 1-3, characterized in that: The main body (1) has an installation groove on its wall, and a ball seat (5) is fixed in the installation groove. The straightening ball (4) is installed through the ball seat (5).

5. A method for drilling and grinding cement plugs inside casings, characterized in that, include: After connecting the drilling tool to the hydraulic ball bearing stabilizer as described in any one of claims 1-4, it is lowered into the casing, and the drilling tool is used to drill and grind the cement plug inside the casing.

6. The method for drilling and grinding cement plugs inside casing according to claim 5, characterized in that: A drill collar is also connected to the construction string consisting of the drilling tools and the hydraulic ball bearing stabilizer.

7. The method for drilling and grinding cement plugs inside casing according to claim 6, characterized in that: The construction tubing also includes a milling sleeve and / or a retrieval cup.

8. The method for drilling and grinding cement plugs inside casing according to any one of claims 5-7, characterized in that: When using the aforementioned drilling tool to drill the cement plug inside the casing, the drilling displacement should be ≥1.5m. 3 / min.

9. The method for drilling and grinding cement plugs inside casing according to claim 8, characterized in that: When drilling the cement plug inside the casing using the aforementioned drilling tool, the drilling pressure is controlled at 40–80 kN and the rotation speed is controlled at 60–110 r / min.

10. The method for drilling and grinding cement plugs inside casing according to claim 9, characterized in that: During the drilling process, a reaming hole is made every 3-5 meters of drilling. After drilling a single section, the reaming hole is raised and lowered twice. The pump is stopped after the workover fluid has circulated for at least one cycle.

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