Casing centralizing short section and construction method

Abstract

The invention provides a casing centralizing nipple which comprises a casing and a centralizing mechanism, the centralizing mechanism comprises a first end ring, a second end ring and a centralizing strip, the first end ring and the second end ring are connected outside the casing in a sleeving mode and arranged in a spaced mode, and the centralizing strip is arranged between the first end ring and the second end ring. And the first end ring is fixed on the sleeve through a shear pin in an initial state, so that the centralizing strip is in a stretching state.

Description

Technical Field

[0001] The invention relates to the technical field of cementing tools, and in particular to a casing straightening pup joint and a construction method. Background Art

[0002] During the cementing stage of oil and gas well production, it is necessary to lower the casing string to stabilize the well wall. To ensure the casing is lowered smoothly, a centralizer is usually installed. The centralizer is a device installed on the casing to keep the casing centered. In the reaming section of small clearance wells, the upper layer with reduced diameter, and the "big belly" section generated when drilling into unstable formations (such as gravel and sand layers), there is a phenomenon of small upper well diameter and large lower well diameter. In order to ensure the centralizing effect of the reaming section, a large-sized centralizer needs to be lowered. In order to pass the reduced diameter section smoothly, a small-sized centralizer needs to be selected. Often, only a compromise method can be adopted, and the centralizing effect is very poor, and even the casing string encounters resistance and the centralizer breaks. Especially when the reaming section is long and the well diameter is much larger than the upper layer, conventional centralizers are difficult to work, which is very unfavorable for subsequent production, fracturing and transformation. Therefore, it is necessary to design a casing centralizing device that can smoothly pass the reduced diameter section and have a good centralizing effect in the "big belly" section and reaming section.

[0003] Therefore, it is desired in the art to provide a casing straightening nipple to solve the above technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide a casing straightening short joint, which can smoothly pass through the reduced diameter well section, and can play a good straightening effect in the "big belly" well section and the expanded hole well section, while not having a major impact on the overall cementing plan.

[0005] According to a first aspect of the present invention, there is provided a casing straightening sub, comprising a casing, and

[0006] A straightening mechanism, the straightening mechanism comprising a first end ring and a second end ring which are sleeved outside the casing and arranged at intervals, and a straightening bar arranged between the first end ring and the second end ring,

[0007] Wherein, the first end ring is fixed to the sleeve by shear nails in the initial state, so that the straightening bar is in a stretched state.

[0008] In one embodiment, the shear pins are dissolved by heating.

[0009] In one embodiment, the melting temperature of the shear nails is not lower than a predetermined temperature of 3°C.

[0010] In one embodiment, the shear pins are dissolved by reaction with a chemical solution.

[0011] In one embodiment, a retaining spring is provided at the joint between the first end ring and the sleeve, and a retaining spring seat is formed on the sleeve and extends radially inward and is used to form a retaining spring connection.

[0012] After the shear nails are dissolved, the clamping spring can move downward under the action of the straightening bar to form a clamping connection with the clamping spring seat, thereby allowing the straightening bar to be in a contracted state to abut against the well wall.

[0013] In one embodiment, the outer diameter of the straightening bar changes by 1.69 to 1.73 times.

[0014] In one embodiment, a plurality of the shear pins are arranged at intervals along the circumference of the first end ring, and the dissolution rate of each of the shear pins is the same.

[0015] In one embodiment, the second end ring is fixed to the sleeve by bolts, and at least four bolts are arranged along the circumference of the second end ring.

[0016] According to a second aspect of the present invention, a construction method is provided, which uses the casing straightening nipple as described above, comprising the following steps:

[0017] S1, setting the straightening bar to a stretched state, fixing the first end ring on the casing through the shear nails, lowering the straightening bar into the wellbore and passing over the reduced diameter well section to a predetermined position;

[0018] S2. The shear nails are dissolved, and the retaining spring moves downward under the action of the straightening strip to form a snap connection with the retaining spring seat so that the straightening strip is in a contracted state, thereby contacting the well wall.

[0019] In one embodiment, the dissolution time of the shear nails is 8 to 12 minutes.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] Firstly, the device is based on soluble shear nails, so it can smoothly pass through the reduced diameter section, and can also play a good straightening effect in the "big belly" section and the expanded hole section, while not having a big impact on the overall cementing plan.

[0022] In other words, during the lowering process, the device can limit the first end ring through the shear nails to make the straightening bar in a stretched state, so that it can smoothly pass through the reduced diameter well section, and after reaching the predetermined position, the shear nails can be melted by heat or dissolved by reaction with a chemical solution, and then the first end ring and the clamping spring are synchronously lowered under the elastic force of the straightening bar until the clamping spring and the clamping spring seat are clamped. At this time, the straightening bar has recovered from the stretched state to the contracted state, so that it can abut against the well wall to achieve a good straightening effect.

[0023] Secondly, the device has the effects of simple structure and reliable performance, so that it can more easily achieve the purpose of improving production efficiency at low cost, so as to further achieve the goal of enhancing production reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be described in detail below with reference to the accompanying drawings, in which:

[0025] Figure 1 The initial state of the casing straightening sub according to the present invention is schematically shown;

[0026] Figure 2 The working state of the casing righting sub according to the present invention is schematically shown.

[0027] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0028] In order to make the technical solutions and advantages of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0029] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0030] In the present invention, unless otherwise clearly stipulated and limited, terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal connection of two elements.

[0031] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] Figure 1 The initial state of the casing straightening sub 100 according to the present invention is schematically shown;

[0034] Figure 2The working state of the casing straightening sub 100 according to the present invention is schematically shown.

[0035] like Figures 1-2 As shown, according to the first aspect of the present invention, there is provided a casing straightening sub 100 which mainly includes a casing 10 and a straightening mechanism arranged on the casing 10. Preferably, the straightening mechanism includes a first end ring 11 and a second end ring 12 sleeved outside the casing 10, and a straightening bar 13 arranged between the first end ring 11 and the second end ring 12.

[0036] In one embodiment of the present invention, the first end ring 11 is arranged on the upper part of the straightening bar 13, and in the initial state, the first end ring 11 is fixed to the casing 10 by shear nails 15; at the same time, the second end ring 12 is arranged on the lower part of the straightening bar 13, and the second end ring 12 is firmly installed on the casing 10 by bolts 14, so that the straightening bar 13 can always be in a stretched state during the lowering process.

[0037] Due to the phenomenon that the upper well diameter is small and the lower well diameter is large in the well expansion section of the small gap well, the shrinkage in the upper layer, and the "big belly" well section generated when drilling into unstable formations (such as gravel and sand layers), the upper well diameter is small and the lower well diameter is large. Therefore, the present invention connects the first end ring 11 and the second end ring 12 so that the straightening bar 13 can always be in a stretched state during the lowering process (in this state, the straightening bar 13 has a smaller outer diameter), so that it can smoothly pass through the diameter well section, which is beneficial to the subsequent underground construction.

[0038] In one embodiment, Figures 1-2 As shown, a plurality of shear nails 15 are arranged along the circumference of the first end ring 11. Preferably, the plurality of shear nails 15 are arranged equidistantly, the size and material of each shear nail 15 are completely the same, and the shear nail 15 is made of a soluble material, so that all the shear nails 15 can have the same dissolution rate, so as to ensure that after the shear nails 15 are dissolved, the straightening bar 13 can smoothly recover from the stretched state to the contracted state, and then can more easily abut against the well wall.

[0039] In the present invention, the shear nail hole on the sleeve 10 adapted to the shear nail 15 is a blind hole.

[0040] Preferably, the outer diameter of the straightening bar 13 changes by 1.69 to 1.73 times. In other words, the outer diameter of the straightening bar 13 after the change is 1.69 to 1.73 times the outer diameter of the straightening bar 13 before the change. Since the straightening bar 13 is made of alloy material, and the first end ring 11, the second end ring 12 and the straightening bar 13 are an integrally formed structure, the straightening mechanism has good elasticity, so that it can be more easily switched between the stretched state and the contracted state, so as to make it easier to perform construction operations underground.

[0041] In one embodiment, Figures 1-2As shown, the second end ring 12 is firmly mounted on the sleeve 10 by bolts 14. Preferably, at least four bolts 14 are arranged along the circumference of the second end ring 12, and usually M6×10 bolts 14 are used to improve the firmness and stability between the second end ring 12 and the sleeve 10.

[0042] In the present invention, when the casing straightening short section 100 is lowered to a predetermined position, the shear nails 15 will gradually dissolve. However, when the shear nails 15 are completely dissolved, the first end ring 11 will move downward under the elastic force of the straightening bar 13, thereby allowing the straightening bar 13 to recover from a stretched state to a contracted state, so as to effectively improve the fit between the straightening bar 13 and the well wall.

[0043] In one embodiment, Figures 1-2 As shown, a circlip 21 is provided at the joint of the first end ring 11 and the sleeve 10, and a circlip seat 22 extending radially inward is formed on the sleeve 10. Preferably, the circlip seat 22 and the circlip 21 are in the same axial direction, so that when the circlip 21 moves downward with the first end ring 11, it can smoothly enter the circlip seat 22 and form a clamping connection with it, thereby achieving the purpose of limiting the movement path of the straightening bar 13.

[0044] In the present invention, after the shear nail 15 is completely dissolved, the retaining spring 21 can move downward under the elastic force of the straightening bar 13 to form a stable clamping relationship with the retaining spring seat 22. At the same time, during the downward process, the straightening bar 13 will be allowed to recover from the stretched state to the contracted state to abut against the well wall.

[0045] Preferably, the retaining spring seat 22 has a stop function, so when the retaining spring 21 is engaged with the retaining spring seat 22 , the first end ring 11 cannot retreat.

[0046] In the present invention, the straightening bar 13 has the smallest outer diameter when it is in a stretched state, i.e., when the first end ring 11 is fixed to the casing 10 by the shear nails 15; and has the largest outer diameter when it is in a contracted state, i.e., when the clamping spring 21 is in a clamping connection with the clamping spring seat 22. Preferably, the device can adjust the size and rebound stroke of the straightening bar 13 according to different well conditions.

[0047] In one embodiment, Figures 1-2 As shown, the casing straightening sub 100 further includes an upper joint 16 disposed on the upper portion of the casing 10 for connecting with a downhole tool. Preferably, the upper end female buckle of the upper joint 16 can be processed into different connection buckle types according to the type of casing on site.

[0048] In the present invention, the shear nail 15 is made of composite material.

[0049] In the present invention, two dissolving methods of the shear nail 15 are introduced, one of which is heating and melting, and the other is reaction dissolution, which are described below accordingly:

[0050] Example 1

[0051] In this embodiment, the shearing nails 15 are heated and melted. Since the temperature in the well is usually relatively stable, the shearing nails 15 can achieve the effect of melting when the casing straightening sub 100 is lowered to the predetermined position, so that the first end ring 11 can be more easily released from the control of the shearing nails 15 to allow the straightening bar 13 to recover from the stretched state to the contracted state, so that the straightening bar 13 can complete the reset work and smoothly abut against the well wall after passing through the reduced diameter well section.

[0052] It has been tested that the shear nails 15 can be completely melted at a predetermined temperature, thereby ensuring that the straightening bar 13 can smoothly complete the posture conversion at a predetermined position underground, which is conducive to the smooth development of underground work.

[0053] Preferably, the melting temperature of the shear nail 15 is not lower than the predetermined temperature by 3° C. In other words, if the predetermined temperature is 15° C., the melting temperature of the shear nail 15 shall not be lower than 12° C. Preferably, the predetermined temperature needs to be set accordingly according to the downhole requirements, and the shear nail 15 has a melting time of 10 minutes at the predetermined temperature.

[0054] Preferably, the melting time of the shear nail 15 is affected by the actual temperature, that is, for every 3°C change (increase / decrease) in temperature, the melting time of the shear nail 15 will increase or decrease by 2 minutes. It is worth noting that if the actual temperature is 3°C lower than the predetermined temperature, the melting time of the shear nail 15 will become 12 minutes; similarly, if the actual temperature is 3°C higher than the predetermined temperature, the melting time of the shear nail 15 will become 8 minutes.

[0055] In the present invention, the dissolution time of the shear nail 15 is generally within the range of 8 to 12 minutes. Therefore, in this way, it is easier to judge whether the shear nail 15 is fully dissolved and the specific time of the reset of the straightening mechanism.

[0056] Example 2

[0057] In this embodiment, the shearing nails 15 adopt a reaction dissolution method, that is, the shearing nails 15 react and dissolve with a special chemical solution. Since the chemical solution only reacts with the shearing nails 15, the shearing nails 15 can achieve the effect of reaction dissolution when the casing straightening sub 100 is lowered to the predetermined position, so that the first end ring 11 can be more easily separated from the control of the shearing nails 15 to allow the straightening bar 13 to recover from the stretched state to the contracted state, so that the straightening bar 13 can complete the reset work and smoothly abut against the well wall after passing through the reduced diameter well section.

[0058] According to the test, the shear nails 15 need to be completely dissolved within 10 minutes, so as to ensure that the straightening bars 13 can smoothly complete the posture conversion at the predetermined position underground, so as to facilitate the smooth development of underground work.

[0059] In this way, the failure of the shear nails 15 during the lowering process can be effectively avoided, thereby preventing the straightening bar 13 from being reset prematurely, and further ensuring that the casing straightening short section 100 is deployed only after it has successfully passed through the reduced diameter well section (i.e., the straightening bar 13 is restored from the stretched state to the contracted state).

[0060] According to a second aspect of the present invention, a construction method is provided, which uses the casing straightening nipple as described above, comprising the following steps:

[0061] First, the straightening bar 13 is placed in a tension state, and the first end ring 11 is fixed to the sleeve 10 by shear nails 15 to limit the state of the straightening bar 13.

[0062] Preferably, the second end ring 12 is now securely mounted on the sleeve 10 via bolts 14 .

[0063] Then, the fixed casing straightening sub 100 is lowered into the wellbore, and the casing straightening sub 100 first passes over the reduced diameter well section until it reaches the predetermined position.

[0064] Thereafter, the shear pins 15 are melted by heat or dissolved by reaction with a chemical solution.

[0065] Finally, after the shear nails 15 are completely melted or dissolved, the first end ring 11 will move downward under the elastic force of the straightening bar 13, and the clip spring 21 will also move downward synchronously under the action of the first end ring 11, until the clip spring 21 and the clip spring seat 22 are connected, thereby limiting the maximum movement path of the straightening bar 13. At this time, the straightening bar 13 has recovered from the stretched state to the contracted state, so that it has a good fit with the well wall.

[0066] Compared with the prior art, the advantages of the present invention are:

[0067] Firstly, the device is based on soluble shear nails, so it can smoothly pass through the reduced diameter section, and can also play a good straightening effect in the "big belly" section and the expanded hole section, while not having a big impact on the overall cementing plan.

[0068] In other words, during the lowering process, the device can limit the first end ring 11 through the shear nails 15 to make the straightening bar 13 in a stretched state, so that it can smoothly pass through the reduced diameter well section, and after reaching the predetermined position, the shear nails 15 can be melted by heat or dissolved by reaction with a chemical solution, and then the first end ring 11 and the clamping spring 21 are synchronously lowered under the elastic force of the straightening bar 13 until the clamping spring 21 is clamped with the clamping spring seat 22. At this time, the straightening bar 13 has been restored from the stretched state to the contracted state, so that it can abut against the well wall to achieve a good straightening effect.

[0069] Secondly, the device has the effects of simple structure and reliable performance, so that it can more easily achieve the purpose of improving production efficiency at low cost, so as to further achieve the goal of enhancing production reliability.

[0070] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art can easily make changes or modifications within the disclosure scope of the present invention, and such changes or modifications should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A casing straightening sub, comprising: a sleeve (10), and A straightening mechanism, the straightening mechanism comprising a first end ring (11) and a second end ring (12) which are sleeved outside the casing (10) and arranged at intervals, and a straightening bar (13) arranged between the first end ring (11) and the second end ring (12), Wherein, the first end ring (11) is fixed to the sleeve (10) by shear nails (15) in the initial state, so that the straightening bar (13) is in a stretched state.

2. The casing straightening sub according to claim 1, characterized in that: The shear nails (15) are dissolved by heating.

3. The casing straightening sub according to claim 2, characterized in that: The melting temperature of the shear pin (15) is not less than a predetermined temperature of 3°C.

4. The casing straightening sub according to claim 1, characterized in that: The shear nails (15) are dissolved by reacting with a chemical solution.

5. The casing straightening sub according to any one of claims 1 to 4, characterized in that: A retaining spring (21) is provided at the joint between the first end ring (11) and the sleeve (10), and a retaining spring seat (22) is formed on the sleeve (10) and extends radially inward and is used to form a retaining spring connection with the retaining spring (21). After the shear nail (15) is dissolved, the retaining spring (21) can move downward under the action of the straightening bar (13) to form a snap connection with the retaining spring seat (22), thereby allowing the straightening bar (13) to be in a contracted state to abut against the well wall.

6. The casing straightening sub according to claim 5, characterized in that: The change in the outer diameter of the straightening bar (13) is 1.69 to 1.73 times.

7. The casing centralizing sub according to claim 6, characterized in that: A plurality of shear pins (15) are arranged at intervals along the circumference of the first end ring (11), and the dissolution rate of each of the shear pins (15) is the same.

8. The casing straightening sub according to claim 7, characterized in that: The second end ring (12) is fixed to the sleeve (10) by means of bolts (14), and at least four bolts (14) are arranged along the circumference of the second end ring (12).

9. A construction method, using the casing straightening sub according to any one of claims 1 to 8, comprising the following steps: S1, setting the straightening bar (13) to a stretched state and fixing the first end ring (11) on the casing (10) through the shear nails (15), lowering into the wellbore and passing over the reduced diameter well section to a predetermined position; S2, the shear nail (15) is dissolved, and the retaining spring (21) moves downward under the action of the straightening bar (13) to form a snap connection with the retaining spring seat (22) so that the straightening bar (13) is in a contracted state, thereby contacting the well wall.

10. The construction method according to claim 9, characterized in that: The dissolution time of the shear nails (15) is 8 to 12 minutes.

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