Fracturing string and staged repeated fracturing method for horizontal wells

Abstract

The present invention provides a fracturing string and a method for repeated fracturing operations in a horizontal well. The fracturing string includes: an oil pipe, which is divided into a plurality of pipe sections. The oil pipe is used as a base pipe for threaded connection with various tools of the pipe section, and provides a fracturing fluid supply channel, and runs through the casing of the horizontal well; a hanger, which is arranged on the oil pipe so that the fracturing string is fixed in the casing as a whole, and the hanger and the casing are connected to each other through slips to establish and release fixed constraints; a packer, which is provided with a plurality of packers, and the plurality of packers are connected to the oil pipe through threads; a release tool, the oil pipe includes a plurality of pipe sections connected in sequence, and the pipe section provided with the hanger is connected to the adjacent pipe section through a release tool, and the release tool is located above the hanger. The present invention solves the problems in the prior art of limited displacement of fracturing construction, easy sand burial of the fracturing string, and difficulty in salvage.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field fracturing, and in particular to a fracturing string and a horizontal well staged repeated fracturing operation method. Background Art

[0002] The existing horizontal well casing completion staged re-fracturing string technologies are mainly the following three:

[0003] "Double seal and single card" drag fracturing technology: the oil pipe with "double packer + sliding sleeve" is put into the well, the packer is set to seal the target layer, fracturing is carried out through the oil pipe, and the pipe string is lifted to change layers to achieve segmented transformation. Since fracturing construction needs to be carried out from the oil pipe, the general construction displacement is small, and as the well depth increases, the friction resistance in the pipe increases. The actual construction displacement cannot meet the fracturing design requirements. Therefore, it is not suitable for deep well section horizontal well transformation. At the same time, after completing single-stage fracturing in some horizontal wells, the pressure diffusion is slow and the waiting time is long, resulting in low construction efficiency and long operation cycle. If the wellhead non-suppressing device is used for operation, there will be problems of complex operation process and high cost.

[0004] Full-wellbore chemical temporary plugging + hydraulic jet fracturing string technology: Use a new high-performance chemical temporary plugging agent to temporarily plug the entire wellbore, and then put in a hydraulic jet string for fixed-point fracturing transformation. This process has the problems of expensive chemical temporary plugging materials and inconsistent performance, and easy sand burial in multi-gun and multi-layer section construction.

[0005] Expandable tubing secondary completion + perforation and fracturing string technology: first put in an expandable tubing, then use special tools to expand the tubing to make it close to the original wellbore wall to create a new wellbore and restore the integrity of the wellbore. Later, perforation and fracturing are used for completion. Due to the high cost and high risk, it is difficult to implement.

[0006] It can be seen from this that the existing fracturing construction has the problems of limited displacement, easy sand burial of the fracturing pipe string, and difficulty in removal. Summary of the invention

[0007] The main purpose of the present invention is to provide a fracturing string and a horizontal well staged repeated fracturing operation method to solve the problems in the prior art of limited fracturing construction displacement, easy sand burial of the fracturing string and difficulty in removal.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a fracturing string is provided, comprising: an oil pipe, which is divided into a plurality of pipe sections, the oil pipe is used as a base pipe for threaded connection with various tools of the pipe section, and provides a fracturing fluid supply channel, and runs through the casing of the horizontal well; a hanger, the hanger is arranged on the oil pipe, so that the fracturing string is fixed in the casing as a whole, and the hanger and the casing are fixedly constrained by the slips to establish and release; a packer, there are a plurality of packers, and the plurality of packers are threadedly connected to the oil pipe; a release tool, the oil pipe comprises a plurality of pipe sections connected in sequence, and the pipe section provided with the hanger is connected to the adjacent pipe section by the release tool, and the release tool is located above the hanger.

[0009] Furthermore, the fracturing string also includes a hydraulic safety joint, and the pipe section provided with the hanger is connected to the adjacent pipe section through the hydraulic safety joint, and the hydraulic safety joint is located below the hanger.

[0010] Furthermore, the oil pipe includes a vertical pipe section and a horizontal pipe section connected in sequence, the hanger is located on the vertical pipe section, and the horizontal pipe section includes a plurality of sub-pipe sections connected in sequence, and each sub-pipe section is connected through an injector.

[0011] Furthermore, a packer is arranged between two adjacent ejectors.

[0012] Furthermore, at least one packer is arranged on the horizontal pipe section.

[0013] Furthermore, the number of the sub-pipe sections is greater than three, and the number of the injectors is multiple and includes at least one fracturing valve and at least one ball-dropping fracturing sleeve.

[0014] Furthermore, the number of the fracturing valve is one and the fracturing valve is located at one end of the horizontal pipe section away from the vertical pipe section relative to the ball-dropping fracturing sleeve.

[0015] Furthermore, there are multiple ball-dropping fracturing sleeves, and the multiple ball-dropping fracturing sleeves are connected to the oil pipe through threads.

[0016] Furthermore, the fracturing pipe string also includes a guide head, and the guide head is provided at one end of the horizontal pipe section away from the vertical pipe section.

[0017] Furthermore, different ejectors have different diameters, and the diameters increase in sequence in a direction approaching the vertical pipe section.

[0018] Furthermore, the rubber sleeve of the packer and / or the sealing ball put into the ball-dropping fracturing sleeve are made of soluble materials.

[0019] Further, the hanger is a slip-type casing hanger.

[0020] According to another aspect of the present invention, a method for staged repeated fracturing of a horizontal well is provided, wherein the above-mentioned fracturing string is used to perform fracturing operations on a horizontal well in an oil and gas field, and the fracturing operation method comprises: a forward circulation well washing operation; and after lowering the fracturing string into the casing, performing a fracturing operation.

[0021] Furthermore, the process of the fracturing operation includes a pre-fracturing step, which includes: pressurizing the entire fracturing string to seal the packer of the fracturing string; when the pressure in the fracturing string continues to increase, the hanger of the fracturing string is sealed and fixed on the inner wall of the casing; and the section of the oil pipe of the fracturing string located above the hanger is lifted out.

[0022] Furthermore, the pre-fracturing step also includes: when the hanger is connected to the adjacent pipe section through the release tool of the fracturing string, it is necessary to lift out the release tool together with the pipe section located above the hanger.

[0023] Furthermore, the process of the fracturing operation also includes a staged fracturing step located after the pre-fracturing step, and the staged fracturing step includes: dropping balls into the fracturing string step by step and pressurizing the fracturing string step by step, so that the sandblasting holes of each injector of the fracturing string are opened in sequence along the direction close to the vertical pipe section, and the liquid and / or gas ejected from the sandblasting holes flows into the formation through the original perforated layer section of the casing.

[0024] Furthermore, the horizontal well staged repeated fracturing operation method also includes a tubing salvage and recovery operation after the fracturing operation is completed, and the salvage and recovery operation includes: dissolving the rubber sleeve of the packer of the fracturing tubing and the sealing ball located in the injector of the fracturing tubing by adding a solvent to the fracturing tubing or by self-dissolving; salvaging the hanger of the fracturing tubing; and salvaging the oil pipe of the fracturing tubing from the casing.

[0025] Furthermore, when the fracturing string is lowered into the casing, a pre-installation step is also included, which includes: connecting the pipe sections of the oil pipes of each fracturing string in sequence, and installing an injector between two adjacent sub-pipe sections; installing a guide head on the end extending into the casing; and installing the packer and hanger of the fracturing string on the oil pipe.

[0026] Furthermore, the pre-installation step also includes installing a hydraulic safety joint below the hanger to connect the hanger to its adjacent pipe section.

[0027] Furthermore, the pre-installation step also includes installing a release tool above the hanger to connect the hanger to the adjacent pipe section.

[0028] According to the technical solution of the present invention, the fracturing string includes an oil pipe, a hanger and a packer. The oil pipe is divided into multiple pipe sections. The oil pipe is used as a base pipe for threaded connection with various tools of the pipe string and provides a fracturing fluid supply channel, and runs through the casing of the horizontal well. The hanger is arranged on the oil pipe to fix the fracturing string as a whole in the casing, and the hanger and the casing are fixedly constrained by the slips to establish and release the fixed constraints. There are multiple packers, and the multiple packers are connected to the oil pipe by threads. A release tool is provided, and the oil pipe includes multiple pipe sections connected in sequence, and the pipe section provided with the hanger is connected to the adjacent pipe section by the release tool, and the release tool is located above the hanger. The present invention designs two modes of overall salvage and graded salvage after the tubing fracturing operation is completed, which reduces the difficulty of removal and improves the safety of the tubing; in addition, the hanger is arranged on the oil pipe to fix the entire tubing and effectively avoid tubing creep during the fracturing process. Not only that, the hanger also has a sealing effect, which can play a certain sealing role on the inside and outside of the tubing, so as to isolate the annulus formed by the oil pipe and the casing from the external environment and prevent the fracturing construction effect from being affected; the packer has the functions of sealing, separation and sealing, and can divide the wellbore into a plurality of relatively independent sealed spaces arranged at intervals, thereby realizing graded fracturing of the fracturing device, wherein each sealed space is a first level, which can be set to multiple levels according to actual conditions; the pipe section of the hanger is connected to the adjacent pipe section by a hand-release tool, which is easy and fast to operate and has high reliability.

[0029] The fracturing string in the present invention mainly includes: "packer + ball fracturing sleeve" multiple fracturing units, hydraulic safety joints, and hangers, and each part is connected by a tubing. After the fracturing construction is completed, the packer is automatically unsealed, and the fracturing string can be salvaged as a whole or in stages to restore the full diameter of the wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 A schematic diagram showing the structure of a fracturing string according to an embodiment of the present invention is shown;

[0032] Figure 2 A schematic diagram of the structure of the wellbore of the present application is shown;

[0033] Figure 3 Shows Figure 1 The fracturing device in the figure is a schematic diagram of a six-stage structure;

[0034] Figure 4 Shows Figure 3 Schematic diagram of the structure of the fracturing device after sealing;

[0035] Figure 5 Shows Figure 4 Schematic diagram of the structure of the mid-release tool and the hanger being separated;

[0036] Figure 6 Shows Figure 5 A schematic diagram of the structure of the first stage fracturing of the fracturing device;

[0037] Figure 7 Shows Figure 5 A schematic diagram of the structure of the fracturing device for performing second-stage fracturing;

[0038] Figure 8 Shows Figure 5 A schematic diagram of the structure of the fracturing device in the embodiment of the present invention for performing the third to sixth stage fracturing;

[0039] Fig. 9 Shows Figure 5 Schematic diagram of the structure after the sealing ball and the packer are dissolved;

[0040] Fig.10 Shows Fig. 9 Schematic diagram of the structure when the hanger is removed;

[0041] Fig.11 Shows Fig.10 Schematic diagram of the structure of the oil pipe being removed;

[0042] Fig.12 Shows Fig.10 Schematic diagram of the structure of the oil pipeline being removed in sections; and

[0043] Fig.13 Shows Fig.10 Another structural schematic diagram of the oil pipeline being removed in sections.

[0044] The above drawings include the following reference numerals:

[0045] 10. Tubing; 20. Casing; 30. Hanger; 40. Packer; 50. Drop tool; 60. Hydraulic safety joint; 70. Ejector; 71. Fracturing valve; 72. Ball fracturing sleeve; 80. Guide head; 90. Sealing ball; 100. Salvage string. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0048] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0049] In order to solve the problems of limited displacement and difficulty in salvaging and recovering the fracturing string in the prior art, the present invention provides a fracturing string and a horizontal well staged repeated fracturing operation method. The horizontal well staged repeated fracturing operation method uses the following fracturing string.

[0050] like Figure 1 As shown, the fracturing string includes an oil pipe 10, a hanger 30 and a packer 40. The oil pipe 10 is divided into multiple pipe sections. The oil pipe 10 is used as a base pipe for threaded connection with various tools of the pipe string and provides a fracturing fluid supply channel, and runs through the casing 20 of the horizontal well; the hanger 30 is arranged on the oil pipe 10 so that the fracturing string is fixed in the casing 20 as a whole, and the hanger 30 and the casing 20 are fixedly constrained by the slips to establish and release; there are multiple packers 40, and multiple packers 40 are connected to the oil pipe 10 by threads; a release tool 50, the oil pipe 10 includes multiple pipe sections connected in sequence, and the pipe section provided with the hanger 30 is connected to the adjacent pipe section through the release tool 50, and the release tool 50 is located above the hanger 30. The present invention designs two modes of overall salvage and graded salvage after the completion of the tubing fracturing operation, which reduces the difficulty of removal and improves the safety of the tubing. In addition, the hanger 30 is arranged on the oil pipe 10 to fix the entire tubing and effectively avoid the creep of the tubing during the fracturing process. Not only that, the hanger 30 also has a sealing effect, which can play a certain sealing role on the inside and outside of the tubing, so as to seal the annulus formed by the oil pipe 10 and the casing 20 to prevent affecting the fracturing construction effect. The packer 40 has the functions of sealing, separation and sealing, and can divide the wellbore into a plurality of relatively independent sealed spaces arranged at intervals, thereby realizing graded fracturing of the fracturing tubing, wherein each sealing space is a first level, which can be set to multiple levels according to actual conditions. The pipe section of the hanger 30 is connected to the adjacent pipe section through the hand-release tool 50, which is convenient and fast to operate and has high reliability.

[0051] It should be noted that the hanger 30 used here includes three parts, namely a connecting structure, a fixing structure, and a sealing structure. The connecting structure is used to connect to the oil pipe 10, and the fixing structure can be anchored to the casing 20 through a cava so as to fix the entire tubing string. The sealing structure is arranged below the fixing structure to seal the annulus between the tubing string and the casing 20. The hanger 30 can be separated from the casing 20 after use, and the cava of the hanger 30 can be separated and retracted from the inner wall of the casing 20 by lifting.

[0052] like Figure 1 As shown, the fracturing string further includes a hydraulic safety joint 60, and the pipe section provided with the hanger 30 is connected to the adjacent pipe section through the hydraulic safety joint 60, and the hydraulic safety joint 60 is located below the hanger 30. In this way, the pipe section of the hanger 30 is connected to the adjacent pipe section through the hydraulic safety joint 60, which is convenient and fast to operate with high reliability.

[0053] like Figure 1 As shown, the oil pipe 10 includes a vertical pipe section and a horizontal pipe section connected in sequence, the hanger 30 is located on the vertical pipe section, and the horizontal pipe section includes a plurality of sub-pipe sections connected in sequence, and each sub-pipe section is connected through an injector 70. The hanger 30 is located on the vertical pipe section and can play a good fixing and sealing role.

[0054] like Figure 1 As shown, a packer 40 is arranged between two adjacent injectors 70. The packer 40 has the function of sealing the annulus between the fracturing string and the casing 20, and can divide the horizontal pipe section into a plurality of sealed spaces arranged at intervals, thereby realizing the staged fracturing of the fracturing device, wherein each sealed space is a level, and can be set to multiple levels according to actual conditions, which is conducive to improving work efficiency.

[0055] like Figure 1 As shown, at least one packer 40 is disposed on the horizontal pipe section.

[0056] like Figure 1 As shown, the number of sub-pipe sections is greater than three, and there are multiple injectors 70 including at least one fracturing valve 71 and at least one ball-dropping fracturing sleeve 72. The number of sub-pipe sections varies according to the number of fracturing stages, and each stage of fracturing includes an injector 70, wherein the injector 70 used in the first stage is a fracturing valve 71, and the other stages use a ball-dropping fracturing sleeve 72.

[0057] like Figure 1 As shown, there is one fracturing valve 71 and it is located at one end of the horizontal pipe section away from the vertical pipe section relative to the ball fracturing sleeve 72. The fracturing valve 71 serves as the first-stage injector 70, and the liquid enters the outer space of the first-stage pipe string through the fracturing valve 71, thereby performing fracturing construction.

[0058] like Figure 1 As shown, there are multiple ball fracturing sleeves 72, and multiple ball fracturing sleeves 72 are connected to the oil pipe 10 through threads. The ball fracturing sleeves 72 are used to provide a fluid supply channel for formation fracturing and communicate with the formation. The number of ball fracturing sleeves 72 is determined according to the number of stages of fracturing transformation required.

[0059] like Figure 1 As shown, the fracturing string further includes a guide head 80, and the end of the horizontal pipe section away from the vertical pipe section is provided with the guide head 80. The guide head 80 has a guiding function, and can guide the oil pipe 10 to move forward in the wellbore, which is conducive to the lowering of the oil pipe 10.

[0060] like Figure 1 As shown, different injectors 70 have different diameters, and the diameters increase in sequence along the direction close to the vertical pipe section. In order to achieve a better fracturing effect, the fracturing device needs to perform fracturing in stages, by dropping sealing balls 90 of different diameters from the wellhead, and the sealing balls 90 stop at the positions of the corresponding injectors 70 according to the diameters, so as to perform staged fracturing.

[0061] Optionally, the rubber sleeve of the packer 40 and / or the sealing ball 90 inserted into the ball-dropping fracturing sleeve 72 are made of soluble materials. In this way, after the fracturing operation is completed and the oil and gas well is in production, the above soluble materials can dissolve by themselves, the packer 40 is unsealed, and the ball-dropping fracturing sleeve 72 returns to its original diameter.

[0062] Preferably, the soluble material is an aluminum-magnesium alloy.

[0063] Preferably, the hanger 30 is a slip type casing 20 hanger 30. The slip type casing 20 hanger 30 can meet the use requirements, can play a good fixing role on the entire pipe string, and avoid creeping of the pipe string during fracturing construction.

[0064] like Figures 2 to 8 As shown, the mine fracturing operation method includes: forward circulation well washing operation; after the fracturing string is lowered into the casing 20, the fracturing operation is performed. Through the well washing operation, the inside of the wellbore is cleaned to facilitate the smooth setting of the fracturing string.

[0065] like Figures 4 to 8As shown, the process of fracturing operation includes a pre-fracturing step, which includes: pressurizing the entire fracturing string so that the packer 40 of the fracturing string is seated; when the pressure in the fracturing string continues to increase, the hanger 30 of the fracturing string is seated and fixed on the inner wall of the casing 20; and the section of the oil pipe 10 of the fracturing string located above the hanger 30 is lifted out. By setting the seal of the packer 40, the casing 20 can be divided into multiple independent spaces, each space represents a level, and fracturing operations are performed in stages, which can improve the efficiency of the fracturing operation and facilitate operation. In addition, the hanger 30 is sealed to prevent pollutants outside the casing 20 from entering the inside of the casing 20 and affecting the fracturing operation. Moreover, the hanger 30 is provided with a cava, which is stuck on the inner wall of the casing 20 to fix the oil pipe 10. By lifting the oil pipe 10 of the fracturing string above the hanger 30, the internal liquid supply space of the casing 20 is increased, the friction resistance of the fracturing fluid along the way during fracturing construction is reduced, the wellhead construction pump pressure is reduced, and the construction displacement is increased.

[0066] like Figure 5 As shown, the pre-fracturing step also includes: when the hanger 30 is connected to the adjacent pipe section through the release tool 50 of the fracturing string, the release tool 50 needs to be pulled out together with the pipe section located above the hanger 30. After the release tool 50 and the pipe section located above the hanger 30 are pulled out, the fracturing string in the casing 20 can be directly fracturing at the hanger 30, and the internal working space of the casing 20 is also increased, providing sufficient fluid supply channels for large-displacement fracturing operations, thereby improving the working efficiency.

[0067] When the hand-dropping tool 50 and the pipe section above the hanger 30 are removed together, a salvage string 100 is required to salvage the hand-dropping tool 50 and the pipe section above the hanger 30 from the casing 20 by using the salvage string 100 .

[0068] like Figures 4 to 8 As shown, the process of fracturing operation also includes a staged fracturing step located after the pre-fracturing step, and the staged fracturing step includes: throwing balls and pressurizing the fracturing string step by step, so that the sandblasting holes of each injector 70 of the fracturing string are opened in sequence along the direction close to the vertical pipe section, and the liquid and / or gas ejected from the sandblasting holes flow into the formation through the perforated layer section of the casing 20. By throwing balls and pressurizing the fracturing string step by step, the staged operation of the fracturing string is realized, the liquid and / or gas enters the casing 20 through the injector 70, and then flows into the formation through the perforated layer section of the casing 20 under the action of the pressure, and the liquid in the formation flows into the casing 20 through the injection holes, and the fracturing operation of each stage is carried out step by step without affecting each other, which is conducive to improving the efficiency of the fracturing operation and facilitating operation.

[0069] like Figures 9 to 13As shown, the horizontal well staged repeated fracturing operation method also includes a tubing salvage and recovery operation after the fracturing operation is completed, and the salvage and recovery operation includes: dissolving the rubber tube of the packer 40 of the fracturing tubing and the sealing ball 90 located in the injector 70 of the fracturing tubing by adding a solvent to the fracturing tubing or by self-dissolving; salvaging the hanger 30 of the fracturing tubing; and salvaging the oil pipe 10 of the fracturing tubing from the casing 20. When performing the recovery operation, the sealing ball 90 and the packer 40 need to be dissolved first, so that the pressure in the casing 20 and the fracturing string tends to be balanced, and then the fracturing string in the casing 20 is salvaged through the salvage string 100. When the salvage starts, the slips of the hanger 30 can be retracted by lifting to separate them from the inner wall of the casing 20. At the same time, the sealing of the hanger 30 is completed, and then the lifting force is continuously increased to salvage the fracturing string. If the lifting force has reached the upper limit during the lifting process and the fracturing string has not been salvaged, it can be salvaged step by step. At this time, continue to lift. At the resistance position, the upper and lower bodies of the corresponding ball-dropping fracturing sleeve 72 are disengaged, and the upper body of the ball-dropping fracturing sleeve 72 and the upper string are salvaged first, and then the lower body and the lower string are salvaged.

[0070] It should be noted that when the sealing ball 90 and the packer 40 are not completely dissolved, they can be dissolved by injecting an acidic solution such as high-concentration salt water.

[0071] In this embodiment, a pre-installation step is also included when lowering the fracturing string into the casing 20. The pre-installation step includes: connecting the pipe sections of the oil pipe 10 of each fracturing string in sequence, and installing an injector 70 between two adjacent sub-pipe sections; installing a guide head 80 on one end extending into the casing 20; and installing the packer 40 and the hanger 30 of the fracturing string on the oil pipe 10.

[0072] The hydraulic safety joint 60 is used to release the lower pipe column first when the hanger 30 is difficult to lift and unseal. The hydraulic safety joint 60 can release the lower constraint of the hanger 30 to facilitate the unseal of the hanger 30 by throwing a ball and holding pressure.

[0073] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0074] 1. Since the oil pipe has multiple sections, it can be taken out in sections during the salvage process, which reduces the difficulty of taking out and improves efficiency;

[0075] 2. The hanger is set on the oil pipe to fix the pipe string and effectively avoid the creep of the pipe string during the fracturing process. In addition, the hanger also has a sealing effect, which can play a certain sealing role inside and outside the pipe string;

[0076] 3. During the fracturing process, the section of the oil pipe above the hanger is taken out to increase the internal space of the wellbore, forming a large-space fracturing fluid supply channel in the wellbore, which is beneficial to increase the fracturing construction displacement.

[0077] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0078] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0079] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fracturing string, characterized in that: include: The oil pipe (10) is divided into a plurality of pipe sections. The oil pipe (10) is used as a base pipe for threaded connection with various tools of the pipe string, provides a fracturing fluid supply channel, and runs through the casing (20) of the horizontal well; A hanger (30), the hanger (30) being arranged on the oil pipe (10) so that the fracturing string is fixed as a whole in the casing (20), and the hanger (30) and the casing (20) are connected by slips to establish and release fixed constraints; A packer (40), wherein the packer (40) is multiple and the multiple packers (40) are connected to the oil pipe (10) through threads; A releasing tool (50), the oil pipe (10) comprises a plurality of pipe sections connected in sequence, and the pipe section provided with the hanger (30) is connected to the adjacent pipe section via the releasing tool (50), and the releasing tool (50) is located above the hanger (30); The fracturing string further comprises a hydraulic safety joint (60), and the pipe section provided with the hanger (30) is connected to the adjacent pipe section via the hydraulic safety joint (60), and the hydraulic safety joint (60) is located below the hanger (30); The oil pipe (10) comprises a vertical pipe section and a horizontal pipe section connected in sequence, the hanger (30) is located on the vertical pipe section, the horizontal pipe section comprises a plurality of sub-pipe sections connected in sequence, and each of the sub-pipe sections is connected via an injector (70); The number of the sub-pipe sections is greater than three, and the number of the injectors (70) is multiple and includes at least one fracturing valve (71) and at least one ball-dropping fracturing sleeve (72); The rubber sleeve of the packer (40) and / or the sealing ball (90) inserted into the ball-throwing fracturing sleeve (72) are made of soluble materials; The method of using the fracturing string to perform fracturing operation on a horizontal well in an oil and gas field includes: Forward circulation well flushing operation; After lowering the fracturing string into the casing (20), a fracturing operation is performed; By lifting the oil pipe (10) of the fracturing string above the hanger (30), the internal liquid supply space of the casing (20) is increased, the friction resistance of the fracturing fluid along the way during the fracturing construction is reduced, the wellhead construction pump pressure is reduced, and the construction displacement is increased; It also includes the pipe string salvage and recovery operation after the fracturing operation is completed, and the salvage and recovery operation includes: The rubber sleeve of the packer (40) of the fracturing string and the sealing ball (90) located in the injector (70) of the fracturing string are dissolved by adding a dissolving agent into the fracturing string or by self-dissolving; Fishing the hanger (30) of the fracturing string; The oil pipe (10) of the fracturing pipe string is fished out from the casing (20).

2. The fracturing string according to claim 1, characterized in that: The packer (40) is arranged between two adjacent ejectors (70).

3. The fracturing string according to claim 1, characterized in that: At least one packer (40) is arranged on the horizontal pipe section.

4. The fracturing string according to claim 1, characterized in that: The number of the fracturing valve (71) is one and is located at an end of the horizontal pipe section away from the vertical pipe section relative to the ball-dropping fracturing sleeve (72).

5. The fracturing string according to claim 4, characterized in that: There are a plurality of ball-throwing fracturing sleeves (72), and the plurality of ball-throwing fracturing sleeves (72) are connected to the oil pipe (10) via threads.

6. The fracturing string according to claim 1, characterized in that: The fracturing pipe string further comprises a guide head (80), and the guide head (80) is arranged at one end of the horizontal pipe section away from the vertical pipe section.

7. The fracturing string according to claim 1, characterized in that: The diameters of the different injectors (70) are different, and the diameters increase in sequence in a direction approaching the vertical pipe section.

8. The fracturing string according to claim 1, characterized in that: The hanger (30) is a slip-type casing hanger.

9. A horizontal well staged repeated fracturing method, characterized in that: A fracturing operation is performed on a horizontal well in an oil and gas field using a fracturing string as claimed in any one of claims 1 to 8, wherein the fracturing operation method comprises: Forward circulation well flushing operation; After the fracturing string is lowered into the casing (20), fracturing operations are performed.

10. The horizontal well staged repeated fracturing method according to claim 9, characterized in that: The process of performing the fracturing operation includes a pre-fracturing step, which includes: Performing an overall internal pressurization treatment on the fracturing string so that a packer (40) of the fracturing string is set; When the pressure inside the fracturing string continues to increase, the hanger (30) of the fracturing string is sealed and fixed on the inner wall of the casing (20); The section of the oil pipe (10) of the fracturing string located above the hanger (30) is pulled out.

11. The horizontal well staged repeated fracturing method according to claim 10, characterized in that: The pre-fracturing step also includes: when the hanger (30) is connected to the adjacent pipe section through the release tool (50) of the fracturing pipe string, the release tool (50) needs to be lifted out together with the pipe section located above the hanger (30).

12. The horizontal well staged repeated fracturing method according to claim 10, characterized in that: The process of performing the fracturing operation also includes a staged fracturing step after the pre-fracturing step, and the staged fracturing step includes: The fracturing string is injected with balls and pressurized step by step, so that the sandblasting holes of each injector (70) of the fracturing string are opened in sequence in a direction close to the vertical pipe section, and the liquid and / or gas ejected from the sandblasting holes flows into the formation through the original perforated layer section of the casing (20).

13. The horizontal well staged repeated fracturing method according to claim 9, characterized in that: The horizontal well staged repeated fracturing operation method further includes a tubing salvage and recovery operation after the fracturing operation is completed, and the salvage and recovery operation includes: The rubber sleeve of the packer (40) of the fracturing string and the sealing ball (90) located in the injector (70) of the fracturing string are dissolved by adding a dissolving agent into the fracturing string or by self-dissolving; Fishing the hanger (30) of the fracturing string; The oil pipe (10) of the fracturing pipe string is fished out from the casing (20).

14. The horizontal well staged repeated fracturing method according to claim 9, characterized in that: When the fracturing string is lowered into the casing (20), a pre-installation step is also included, and the pre-installation step includes: The pipe sections of the oil pipe (10) of each fracturing pipe string are connected in sequence, and an injector (70) is installed between two adjacent sub-pipe sections; A guide head (80) is installed on one end extending into the sleeve (20); The packer (40) and the hanger (30) of the fracturing string are installed on the oil pipe (10).

15. The horizontal well staged repeated fracturing method according to claim 14, characterized in that: The pre-installation step further comprises installing a hydraulic safety joint (60) below the hanger (30) to connect the hanger (30) to the adjacent pipe section.

16. The horizontal well staged repeated fracturing method according to claim 14, characterized in that: The pre-installation step further comprises installing a drop tool (50) above the hanger (30) to connect the hanger (30) to the adjacent pipe section.

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