Integral elastic centralizer and preparation method thereof

Abstract

The invention relates to the field of well cementation tools, in particular to an integral type elastic centralizer and a preparation method thereof, and aims to relieve the technical problem that related centralizers are poor in centralizing effect in reaming well sections, ultra-deep wells and extra-deep wells. The centralizer comprises two end rings, wherein the two end rings are coaxially distributed at an interval; the plurality of bow pieces are mechanically bent to be M-shaped and are distributed around the axis of the end ring at intervals; the two outer convex parts of the bow piece protrude towards the direction far away from the axis of the end ring, and the two ends of the bow piece are fixedly connected with the two end rings respectively; and the fixing ring is located among the plurality of bow pieces and is connected with the inner concave parts in the middles of the plurality of bow pieces through soluble screws. The outer diameter of the centralizer is smaller than that of a passing well section before the centralizer enters a mounting well section, so that friction resistance is greatly reduced, after the centralizer enters the mounting well section, the soluble screw is unlocked, the outer diameter of the centralizer recovers to the original size, the bow piece abuts against the well wall, centering and centralizing of a casing pipe are achieved, and the well cementation quality is improved.

Description

Technical Field

[0001] The invention relates to the field of cementing tools, and in particular to an integral elastic centralizer and a preparation method thereof. Background Art

[0002] At present, for well sections with a large borehole expansion rate, the cementing quality is often unqualified due to poor casing centering during cementing. The existing conventional rigid stabilizers and elastic stabilizers cannot effectively improve the casing centering in the expanded well due to the limited outer diameter of the stabilizer. Simply increasing the outer diameter of the stabilizer will cause the rigid stabilizer to be unable to be lowered, and the elastic stabilizer will have too much friction when lowered, affecting the safety of the casing. Although the in-pipe pressure differential stabilizer can solve the problem of casing centering in expanded wells, the integrity of the pipe string is poor, and damage to the sealing mechanism in the later stage will cause the pipe string to be scrapped. For ultra-deep and extra-deep wells, conventional elastic stabilizers are severely worn during the well entry process, which can easily lead to the destruction of the bow piece, thereby losing the straightening effect. Summary of the invention

[0003] The object of the present invention is to provide an integral elastic centralizer and a preparation method thereof, so as to alleviate the technical problem that the centralizer has poor centralizing effect in well expansion sections, ultra-deep wells and extra-deep wells.

[0004] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, the present invention provides an integral elastic centralizer, comprising: two end rings, the two end rings being coaxial and spaced apart; A plurality of bow pieces machined and bent into an M shape, wherein the plurality of bow pieces are spaced apart and distributed around the axis of the end ring; The two outer protrusions of the bow piece protrude in a direction away from the axis of the end ring, and the two ends of the bow piece are fixedly connected to the two end rings respectively; A fixing ring is located between the plurality of bow pieces and is connected to the inner recessed parts in the middle of the plurality of bow pieces by means of soluble screws.

[0005] Further, the soluble screw comprises a soluble screw rod; The thread section of the soluble screw is a hollow slotted elastic claw structure, the interior of which is filled with hot-melt filler.

[0006] Furthermore, the soluble screw also includes a soluble head; The soluble head is integrally formed with the soluble screw, and the side surface of the soluble head is connected to the side surface of the soluble screw via an inclined surface; The inclined surface extends from the side surface of the soluble head to the side surface of the soluble screw in a direction away from the soluble head and is used to fit with the surface of the bow piece.

[0007] Furthermore, a through hole is provided in the middle of the bow piece, and the diameter of the through hole is larger than the outer diameter of the soluble screw and smaller than the diameter of the soluble head.

[0008] Furthermore, along the radial direction of the end ring and from the inside to the outside, the soluble screw is lower than the outer protrusion.

[0009] Furthermore, the fixing ring is coaxially arranged with the end ring, and the inner diameter of the fixing ring is equal to the inner diameter of the end ring.

[0010] Furthermore, a plurality of bosses are formed on the outer wall of the fixing ring, and the plurality of bosses correspond to the plurality of bow pieces one by one; The boss is provided with a threaded through hole adapted to the soluble screw. In the radial direction of the fixing ring, the length of the boss is equal to the width of the bow piece.

[0011] In a second aspect, the present invention further provides a method for preparing an integral elastic centralizer, which is used to prepare the integral elastic centralizer described above, comprising the following steps: S1, tube cutting and stamping to produce one-piece end rings and bow pieces; S2, bending the bow piece inwardly from the middle of the bow piece into an M shape, and opening a through hole in the middle of the bow piece; S3, processing a fixing ring, and forming threaded through holes on the fixing ring corresponding to the limbs one by one; S4, using a pre-tightening tool to keep each of the limbs in an M shape; S5, embedding the fixing ring between the bow pieces, and using the pre-tightening tool to make the inner surface of the middle part of the bow piece fit with the outer wall of the fixing ring, and aligning the through hole and the threaded through hole; S6, inserting a soluble screw into the through hole and connecting it to the fixing ring through the threaded through hole, and then tightening the soluble screw until the inclined surface of the soluble head is in contact with the bent inclined surface of the bow piece; S7, after all the soluble screws are installed, hot-melt filler is filled into the soluble screw; S8, after the hot-melt filler is cooled and hardened, the pre-tightening tool is removed.

[0012] Furthermore, the pre-tightening tooling includes a mounting ring and a hollow threaded sleeve; In the step S4, the mounting ring is sleeved on the outside of each of the bow pieces, and the hollow screw sleeves corresponding to the bow pieces are connected along the radial direction of the mounting ring, and the inner holes of the hollow screw sleeves are aligned with the corresponding through holes, and then the hollow screw sleeves are tightened until the hollow screw sleeves abut against the outer surface of the middle part of the bow piece; In the step S5, the hollow screw sleeve is tightened until the inner surface of the middle part of the bow piece is in contact with the outer wall of the fixing ring; In the step S6, the soluble screw is installed from the inner hole of the hollow screw sleeve.

[0013] Furthermore, a groove is provided on the side wall of the hollow screw sleeve, and in steps S4, S5, S6 and S8, the hollow screw sleeve is screwed through the groove.

[0014] In summary of the above technical solutions, the technical effects that can be achieved by the integrated elastic centralizer provided by the present invention are: In the integrated elastic straightener, the two ends of the bow piece are respectively fixed to the two end rings, and the middle part is fixed to the fixing ring by a soluble screw, and the bow piece as a whole is M-shaped. After the soluble screw is dissolved, the bow piece will stretch outward under the action of its restoring force, and the outer diameter of the whole composed of multiple bow pieces will increase.

[0015] When in use, the integral elastic straightener is sleeved on the casing. During the process of entering the well with the casing, the bow piece is locked by the soluble screw and the fixing ring in an M shape and is in a compressed state. The local part, namely the outer convex part, rubs against the wellbore, thereby reducing the wear of the bow piece and the resistance of the pipe string being lowered. When the pipe string is lowered to a certain position, the soluble screw dissolves under the action of the liquid in the wellbore, releasing the lock on the bow piece. The bow piece stretches outward under the action of its elastic restoring force, returns to its initial state, fits and abuts against the wellbore wall, and realizes the straightening and centering of the casing.

[0016] It can be seen that compared with the prior art, the outer diameter of the integral elastic stabilizer is smaller than the passing section before entering the installation section, thereby greatly reducing frictional resistance. After entering the installation section, the soluble screw is unlocked to restore the outer diameter of the stabilizer to its original size, and the stabilizer abuts against the well wall to achieve centering of the casing; for reaming sections, ultra-deep wells, and extra-deep wells, the integral elastic stabilizer can improve the centering degree of the casing, thereby improving the cementing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A schematic diagram of the structure of an integral elastic centralizer provided in an embodiment of the present invention; Figure 2 A cross-sectional view of a soluble screw provided by an embodiment of the present invention; Figure 3 A bottom view of a soluble screw provided by an embodiment of the present invention; Figure 4 A schematic diagram of the connection between the soluble screw and the bow limb provided in an embodiment of the present invention; Figure 5 A cross-sectional view of a fixing ring provided in an embodiment of the present invention; Figure 6 A schematic diagram of the well entry of an integral elastic centralizer provided by an embodiment of the present invention; Figure 7 A schematic diagram of the centralizing of an integral elastic centralizer provided in an embodiment of the present invention; Figure 8 A schematic diagram of the preparation of an integral elastic centralizer provided in an embodiment of the present invention; Fig. 9 A cross-sectional view of a hollow threaded sleeve provided in an embodiment of the present invention.

[0019] Icon: 1-end ring; 2-bow piece; 3-fixing ring; 31-boss; 32-threaded through hole; 4-soluble screw; 41-soluble screw rod; 42-hot melt filler; 43-soluble head; 431-inclined surface; 5-Mounting ring; 6-hollow screw sleeve; 61-cutting groove; 7-casing; 8-well wall. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0023] At present, for well sections with a large borehole expansion rate, the cementing quality is often unqualified due to poor casing centering during cementing. The existing conventional rigid stabilizers and elastic stabilizers cannot effectively improve the casing centering in the expanded well due to the limited outer diameter of the stabilizer. Simply increasing the outer diameter of the stabilizer will cause the rigid stabilizer to be unable to be lowered, and the elastic stabilizer will have too much friction when lowered, affecting the safety of the casing. Although the in-pipe pressure differential stabilizer can solve the problem of casing centering in expanded wells, the integrity of the pipe string is poor, and damage to the sealing mechanism in the later stage will cause the pipe string to be scrapped. For ultra-deep and extra-deep wells, conventional elastic stabilizers are severely worn during the well entry process, which can easily lead to the destruction of the bow piece, thereby losing the straightening effect.

[0024] In view of this, refer to Figure 1 The present invention provides an integral elastic straightener, comprising two end rings 1, which are coaxial and spaced apart; a plurality of limbs 2, which are machined to be M-shaped limbs 2, and spaced apart around the axis of the end ring 1; two outer convex parts of the limb 2 protrude in a direction away from the axis of the end ring 1, and the two ends of the limb 2 are fixedly connected to the two end rings 1 respectively; a fixing ring 3, which is located between the plurality of limbs 2 and is connected to the inner concave parts in the middle of the plurality of limbs 2 by soluble screws 4.

[0025] In the integrated elastic straightener, the two ends of the limb 2 are respectively fixed to the two end rings 1, and the inner concave part is fixed to the fixing ring 3 by the soluble screw 4, and the limb 2 is in an M shape as a whole. After the soluble screw 4 is dissolved, the limb 2 will stretch outward under the action of its restoring force, and the outer diameter of the whole composed of multiple limbs 2 will increase.

[0026] When in use, the integral elastic straightener is sleeved on the casing 7. During the process of entering the well with the casing 7, the bow piece 2 is locked by the soluble screw 4 and the fixing ring 3 in an M shape and is in a compressed state. Its local part, namely the convex part, rubs against the wellbore, thereby reducing the wear of the bow piece 2 and the resistance of the pipe string being lowered. When the pipe string is lowered to a certain position, the soluble screw 4 dissolves under the action of the liquid in the wellbore, releasing the lock on the bow piece 2. The bow piece 2 stretches outward under the action of its elastic restoring force, returns to its initial state, and abuts against the well wall 8, thereby realizing the straightening and centering of the casing 7.

[0027] It can be seen that compared with the prior art, the outer diameter of the integral elastic centralizer is smaller than the passing section before entering the installation section, thereby greatly reducing frictional resistance. After entering the installation section, the soluble screw 4 is unlocked, so that the outer diameter of the centralizer is restored to its original size, and the centralizer abuts against the well wall 8 to achieve centering of the casing 7; for reaming sections, ultra-deep wells, and extra-deep wells, the integral elastic centralizer can improve the centering degree of the casing 7, thereby improving the cementing quality.

[0028] It should be added that the bow limb 2 bent into an M-shaped structure forms two arc-shaped segments with the inner concave portion as the boundary, and the bow limb 2 can be regarded as a double-arc bow limb; compared with the single-arc bow limb directly concave, in the double-arc bow limb, the arc length of the arc-shaped segments is short, the distance between the two end fulcrums is short, and the span is small. Therefore, under the compression condition, the supporting reaction force (resetting force) of the double-arc bow limb will be greater than the supporting reaction force (resetting force) of the single-arc bow limb. With this design, the elastic restoring force of the bow limb 2 is significantly improved, so that the inner surface of the inner concave portion of the bow limb 2 is in contact with the fixing ring 3 when the bow limb 2 is squeezed by external force, and the centering degree of the sleeve 7 is in a relatively high range in the reset state.

[0029] The following combination Figures 1 to 7 The structure and shape of the integral elastic centralizer provided in this embodiment are described in detail: In this embodiment, reference Figure 1 The centralizing part of the integral elastic centralizer, namely the end ring 1 and the bow piece 2, is of integral design, without welding or riveting between the two, and is formed by integrally cutting and stamping the pipe. Figure 1 and Figure 4 As shown, more preferably, the bow piece 2 has an M-shaped structure that is symmetrical on both sides, and the depth of the inner concave in the middle is greater than the height of the soluble screw 4. In this way, the soluble screw 4 will not rub against the well wall 8 during the entering the well; in addition, a through hole is provided at the center position of the bending part of the bow piece 2, and the diameter of the through hole is greater than the outer diameter of the soluble screw 41 and smaller than the diameter of the soluble head 43, so that the soluble screw 41 can pass through the through hole, but the soluble head 43 cannot pass through.

[0030] Preferably, combined with Figure 1 and Figure 5 As shown, the fixing ring 3 is coaxially arranged with the end ring 1, and its inner diameter is equal to the inner diameter of the end ring 1; a plurality of bosses 31 are formed on the outer wall of the fixing ring 3, and the plurality of bosses 31 correspond to the plurality of limbs 2 one by one, and the bosses 31 are provided with threaded through holes 32 that are threadably matched with the soluble screws 4, and in the radial direction of the fixing ring 3, the length of the bosses 31 is equal to the width of the limb 2. Such a design ensures effective connection with the limb 2 while also ensuring the coaxiality of each limb 2, so that the centering degree of the sleeve 7 can be improved when the sleeve 7 is straightened.

[0031] Regarding the soluble screw 4, specifically: In one embodiment of the present application, the soluble screw 4 is made entirely of a soluble material, and optionally, the soluble material is a magnesium-aluminum alloy. Figure 2 and Figure 3The soluble screw 4 includes a soluble screw 41; the threaded section of the soluble screw 41 is a hollow slotted elastic claw structure, and the interior thereof is filled with hot-melt filler 42. In other embodiments, the soluble screw 4 is made entirely of a soluble material, and optionally, the soluble material is a magnesium-aluminum alloy; the soluble screw 4 includes a soluble screw 41; the threaded section of the soluble screw 41 is a hollow slotted elastic claw structure, and the interior thereof is filled with hot-melt filler 42.

[0032] With the above design, there are three ways to unlock the bow piece 2, namely, unlocking by dissolving the soluble screw 4 by the wellbore liquid, unlocking by melting the hot melt material controlled by the well temperature, and a combination of the two. Figure 6 and Figure 7 When the pipe string is lowered to a certain position, the hot-melt filler 42 in the soluble screw 4 melts at the high temperature in the well, and the elastic claw structure loses its support. At this time, under the elastic restoring force of the bow piece 2, the soluble screw 4 is pulled, and its elastic claw structure shrinks and deforms, releasing the threaded connection with the fixing ring 3. Then the bow piece 2 continues to stretch outward, recovering to the initial state during stamping, and fitting with the well wall 8. For this unlocking method combining the two, if the hot-melt filler 42 does not melt due to other factors, the elastic claw structure of the soluble screw 4 will also dissolve before cementing construction, releasing the bow piece 2.

[0033] In this embodiment, reference Figure 2 The soluble screw 4 further includes a soluble head 43; the soluble head 43 is integrally formed with the soluble screw 41. Preferably, the side of the soluble head 43 is connected to the side of the soluble screw 41 through an inclined surface 431, and the inclined surface 431 extends downward from the side of the soluble head 43 to the side of the soluble screw 41, and its taper is the same as the bending angle of the bow 2. In this way, when the bow 2 is tightened, the inclined surface 431 is in contact with the bent inclined surface of the bow 2, as shown in FIG. Figure 4 As shown, the contact area between the soluble screw 4 and the bow piece 2 is increased, so that the bow piece 2 is effectively pressed.

[0034] When the integral elastic centralizer provided by the present invention is used, it is combined with Figure 6 and Figure 7As shown, the centralizer is sleeved outside the casing 7. During the process of casing 7 entering the well, the bow piece 2 is in a compressed state under the locking of the soluble screw 4 and the fixing ring 3, and its part rubs against the wellbore, thereby reducing the wear of the bow piece 2 and the resistance of the pipe string to be lowered; when the pipe string is lowered to a certain position, the hot melt filler 42 in the soluble screw 4 melts at the high temperature in the well, and the bow piece 2 stretches outward under the elastic restoring force, and further pulls the soluble screw 4, so that its elastic claw structure shrinks and deforms, so that the soluble screw 4 is separated from the threaded through hole 32 of the fixing ring 3, and then the bow piece 2 is completely restored to the initial state when stamped and formed, and fits and abuts against the well wall 8 to realize the centering of the casing 7. Here, if the hot melt filler 42 does not melt due to other factors, the soluble screw 4 will also dissolve before the cementing construction, releasing the bow piece 2.

[0035] The integrated elastic straightener reduces wear by compressing the bow piece 2 so that the bow piece 2 does not completely rub against the well wall 8 during the well entry process. The straightening function of the casing 7 is achieved by the elastic force of the bow piece 2 after it is unlocked and the supporting force of the fixing ring 3 and the bending point of the bow piece 2.

[0036] The present invention also provides a method for preparing an integral elastic centralizer, wherein a pre-tightening tool is used in the implementation of the method, Figure 8 and Fig. 9 The pre-tightening tool comprises a mounting ring 5 and a hollow screw sleeve 6, wherein the mounting ring 5 is an annular structure with a plurality of threaded holes evenly distributed around the circumference, and its inner diameter is larger than the maximum free outer diameter of the limb 2; the hollow screw sleeve 6 is a hollow bolt structure with a slot 61 at the end, and is connected with the mounting ring 5 through a threaded hole, and its inner diameter is larger than the maximum outer diameter of the soluble screw 4. The preparation method of the integral elastic centralizer comprises the following steps: S1, cutting and stamping the tube to produce an integrally formed end ring 1 and bow piece 2; S2, using a special tool to bend each bow piece 2 into an M shape, and opening a through hole in the middle of the bow piece 2; S3, processing the fixing ring 3, and opening a threaded through hole 32 on the fixing ring 3 corresponding to the bow piece 2; S4, sleeve the mounting ring 5 on the outside of the bow piece 2, and install the hollow screw sleeve 6, the inner hole of the hollow screw sleeve 6 is aligned with the through hole of the bow piece 2, refer to Figure 8; S5, use common tools such as a flat-blade screwdriver to insert it into the cutting groove 61, tighten the hollow screw sleeve 6, and press it against the bending part of the bow piece 2; S6, embed the fixing ring 3 between the bow pieces 2, and continue to tighten the hollow screw sleeve 6, so that the inner surface of the middle part of the bow piece 2 fits with the outer surface of the boss 31, and aligns the through hole and the threaded through hole 32; S7, install the soluble screw 4 from the inner hole of the hollow screw sleeve 6, connect the fixing ring 3 and the bow piece 2 together and fix them, tighten the soluble screw 4 until the inclined surface 431 of the soluble head 43 fits with the bent inclined surface of the bow piece 2, and the height of the soluble head 43 is lower than the height of the bow piece 2; S8, after the soluble screws 4 are all installed, fill the hot-melt filler 42 into the soluble screw 41; S9, after the hot-melt filler 42 cools and hardens, loosen the hollow screw sleeve 6 and remove the mounting ring 5; S10, the assembly of the integral elastic straightener is completed.

[0037] In the above, the pipe is cut by machining equipment and then punched into an elastic centralizer with a size equivalent to the borehole size of the installation section, and then the outer diameter of the centralizer is compressed to be smaller than the inner diameter of the upper casing 7 by special tooling, and fixed to an annular mechanism (i.e., fixed ring 3) by an unlocking member (i.e., soluble screw 4). Before the centralizer enters the installation section, its outer diameter is smaller than the inner diameter of the passing section, thereby greatly reducing friction. After entering the installation section, the unlocking member is unlocked, so that the outer diameter of the centralizer is restored to the original size, and the casing 7 is centered.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integral elastic centralizer, characterized in that: include: Two end rings (1), the two end rings (1) are coaxial and spaced apart; a plurality of bow pieces (2) machined and bent into an M shape, the plurality of bow pieces (2) are spaced apart around the axis of the end ring (1); two outer convex parts of the bow piece (2) protrude in a direction away from the axis of the end ring (1), and the two ends of the bow piece (2) are respectively fixedly connected to the two end rings (1); a fixing ring (3), the fixing ring (3) is located between the plurality of bow pieces (2), and is connected to the inner concave parts in the middle of the plurality of bow pieces (2) themselves through soluble screws (4).

2. The integrated elastic centralizer according to claim 1, characterized in that: The soluble screw (4) comprises a soluble screw rod (41); The threaded section of the soluble screw (41) is a hollow slotted elastic claw structure, the interior of which is filled with hot-melt filler (42).

3. The integrated elastic centralizer according to claim 2, characterized in that: The soluble screw (4) further comprises a soluble head (43); The soluble head (43) is integrally formed with the soluble screw (41), and the side surface of the soluble head (43) is connected to the side surface of the soluble screw (41) via an inclined surface (431); The inclined surface (431) extends from the side surface of the soluble head (43) to the side surface of the soluble screw (41) in a direction away from the soluble head (43), and is used to fit with the surface of the bow piece (2).

4. The integrated elastic centralizer according to claim 3, characterized in that: A through hole is provided in the middle of the bow piece (2), and the diameter of the through hole is larger than the outer diameter of the soluble screw (41) and smaller than the diameter of the soluble head (43).

5. The integrated elastic centralizer according to claim 1, characterized in that: Along the radial direction of the end ring (1) and from the inside to the outside, the soluble screw is lower than the outer protrusion.

6. The integrated elastic centralizer according to claim 1, characterized in that: The fixing ring (3) is coaxially arranged with the end ring (1), and its inner diameter is equal to the inner diameter of the end ring (1).

7. The integrated elastic centralizer according to claim 6, characterized in that: A plurality of bosses (31) are formed on the outer wall of the fixing ring (3), and the plurality of bosses (31) correspond one-to-one to the plurality of bow pieces (2); The boss (31) is provided with a threaded through hole (32) that is threadably matched with the soluble screw (4). In the radial direction of the fixing ring (3), the length of the boss (31) is equal to the width of the bow piece (2).

8. A method for preparing an integral elastic centralizer, characterized in that: Used for preparing the integral elastic centralizer as claimed in any one of claims 1 to 7, The following steps are involved: S1, cutting and stamping the tube to produce an integrally formed end ring (1) and a bow piece (2); S2, bending the bow piece (2) inwardly from the middle of the bow piece (2) into an M shape, and opening a through hole in the middle of the bow piece (2); S3, processing a fixing ring (3), and forming threaded through holes (32) on the fixing ring (3) corresponding to the limbs (2) one by one; S4, using a pre-tightening tool to keep each of the limbs (2) in an M shape; S5, embedding the fixing ring (3) between the bow pieces (2), and using the pre-tightening fixture to make the inner surface of the middle part of the bow piece (2) fit with the outer wall of the fixing ring (3), while aligning the through hole and the threaded through hole (32); S6, inserting a soluble screw (4) into the through hole and connecting the screw to the fixing ring (3) through the threaded through hole (32), and then tightening the soluble screw (4) until the inclined surface (431) of the soluble head (43) is in contact with the bent inclined surface (431) of the bow piece (2); S7, after all the soluble screws (4) are installed, hot-melt filler (42) is filled into the soluble screw rod (41); S8, after the hot-melt filler (42) cools and hardens, the pre-tightening tool is removed.

9. The method for preparing an integral elastic centralizer according to claim 8, characterized in that: The pre-tightening tool comprises a mounting ring (5) and a hollow threaded sleeve (6); In the step S4, the mounting ring (5) is sleeved on the outside of each of the bow pieces (2), and the hollow screw sleeves (6) corresponding to the bow pieces (2) are connected along the radial direction of the mounting ring (5) by screw thread, and the inner hole of the hollow screw sleeve (6) is aligned with the corresponding through hole, and then the hollow screw sleeve (6) is tightened until the hollow screw sleeve (6) abuts against the outer surface of the middle part of the bow piece (2); In the step S5, the hollow screw sleeve (6) is tightened until the inner surface of the middle portion of the bow piece (2) is in contact with the outer wall of the fixing ring (3); In the step S6, the soluble screw (4) is installed from the inner hole of the hollow screw sleeve (6).

10. The method for preparing an integral elastic centralizer according to claim 9, characterized in that: A cutting groove (61) is provided on the side wall of the hollow screw sleeve (6), and in steps S4, S5, S6 and S8, the hollow screw sleeve (6) is screwed through the cutting groove (61).

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