Fracturing production integrated pipe string system and implementation method

Abstract

The present invention relates to the technical field of low-permeability oil and gas reservoir development, and in particular to a fracturing and production integrated tubing system, including a fracturing tubing and a production tubing, wherein the fracturing tubing is divided into a vertical and inclined well section fracturing tubing section and a horizontal fracturing tubing section, wherein the vertical and inclined well fracturing tubing section comprises a first oil pipe and a first hanging working cylinder, a sealing working cylinder and a gas lift working cylinder connected in sequence through the first oil pipe; the production tubing comprises a second oil pipe and a first hanger, an insert seal and a perforated pipe connected in sequence through the second oil pipe, wherein an air inlet hole is provided on the pipe wall of the perforated pipe, wherein the production tubing can be inserted into the fracturing tubing, wherein the first hanger is opposite to the first hanging working cylinder, the insert seal is sealed with the sealing working cylinder, and the perforated pipe is combined with the gas lift working cylinder; and the present invention also relates to an implementation method of the above-mentioned fracturing and production integrated tubing system, wherein gas is extracted by means of the above-mentioned fracturing and production integrated tubing system, so that the production tubing has a gas lift function, and the production efficiency of the gas well can be further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of low-permeability oil and gas reservoir development, and in particular to a fracturing production integrated pipe string system and an implementation method thereof. Background Art

[0002] At present, low-permeability oil and gas reservoirs are mainly developed by fracturing. For offshore low-permeability oil and gas reservoirs, there is a common feature of high water saturation. After fracturing, water is often produced. In order to ensure the liquid carrying effect, small-sized production pipes (small inner diameter) are generally used for production. However, since the burial depth of offshore low-permeability oil and gas reservoirs is often relatively deep, the use of small-sized production pipes will lead to large friction resistance during fracturing construction, affecting the degree of reservoir transformation, increasing construction risks and difficulties, and affecting the development effect of oil and gas reservoirs. If a large-sized production pipe (large inner diameter) is used to ensure the fracturing effect, the liquid carrying capacity of the pipe is reduced (the gas output will not meet the requirements of continuous liquid carrying due to too low flow rate), the gradual accumulation of liquid in the wellbore will restrict the production efficiency of the gas well, liquid will accumulate near the bottom of the well, the production layer will be affected by water invasion, water lock, and expansion of water-sensitive clay minerals, and the gas phase permeability will be reduced, thereby greatly reducing the recovery rate of the gas reservoir, shortening the production time, or even stopping production. Since the operating costs of offshore oil and gas fields are relatively high, the conventional operating methods take a long time and are expensive to replace the tubing. Therefore, it is not advisable to use a large-sized production tubing for fracturing and then replace it with a small-sized production tubing after fracturing. This creates a contradiction between fracturing and production.

[0003] For this reason, the concept of velocity string was proposed. Velocity string is a small diameter string that plays a role in throttling and speeding up the downhole fluid. It is suspended in the wellbore (or inside the production tubing) by a surface hanger or a wellbore suspension device to serve as a completion production string. When the formation fluid enters the velocity tube driven by natural energy, the flow area is smaller than that of conventional production tubing. Based on the principle of variable diameter pipe fluid mechanics, the fluid velocity on the smaller flow cross section is increased, thereby improving the liquid carrying capacity.

[0004] However, the velocity string still has the following problems: when the gas well production capacity continues to decrease or the production process needs to be stopped and restarted for various reasons, the liquid carrying capacity of the velocity string will also be significantly reduced, and the gas well will accumulate liquid again. Summary of the invention

[0005] The object of the present invention is to provide a fracturing-production integrated tubing system, which can meet both fracturing requirements and production requirements, has a strong liquid carrying capacity and low operating cost.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A fracturing and production integrated tubing system comprises a fracturing tubing and a production tubing, wherein the fracturing tubing is divided into a vertical and inclined well section fracturing tubing section and a horizontal fracturing tubing section, wherein the vertical and inclined well section fracturing tubing section comprises a first oil pipe and a first suspension working cylinder, a sealing working cylinder and a gas lift working cylinder connected in sequence via the first oil pipe; the production tubing comprises a second oil pipe and a first hanger, an insert seal and a perforated pipe connected in sequence via the second oil pipe, wherein an air inlet hole is opened on the wall of the perforated pipe; when the production tubing is inserted into the fracturing tubing, the first hanger is combined with the first suspension working cylinder, the insert seal is sealed with the sealing working cylinder, and the perforated pipe is combined with the gas lift working cylinder.

[0008] Optionally, a plug is further included, and a plug hanging working cylinder is provided at the tail end of the vertical fracturing pipe string section, and the plug can enter into the plug hanging working cylinder and seal with the plug hanging working cylinder.

[0009] Optionally, the vertical and inclined well section fracturing tubing section also includes a downhole safety valve and a second suspension working cylinder, the upper and lower ends of the downhole safety valve are respectively connected to the second suspension working cylinder and the first suspension working cylinder through a section of the first oil pipe, the production tubing also includes a second hanger, a section of the second oil pipe is connected below the second hanger, and the second hanger can be combined with the second suspension working cylinder.

[0010] Optionally, a plurality of air inlet holes are arranged circumferentially around the perforated tube.

[0011] Optionally, the sealing working cylinders and the gas lift working cylinders are alternately arranged in multiple groups up and down, the inserted seals correspond one-to-one to the sealing working cylinders, and the perforated tubes correspond one-to-one to the gas lift working cylinders.

[0012] Optionally, the gas lift working cylinder is a sliding sleeve type gas lift working cylinder, which includes an outer cylinder, an inner cylinder and a gas lift valve. The gas lift valve is arranged on the outer cylinder, and a gas lift hole corresponding to the outlet of the gas lift valve is opened on the outer cylinder. The inner cylinder is located in the outer cylinder and is sealed and slidably connected with the outer cylinder, and a through hole is opened on the inner cylinder.

[0013] Optionally, the first oil pipe is a 4-1 / 2″ oil pipe, and the second oil pipe is a 2-3 / 8″ oil pipe.

[0014] Another object of the present invention is to provide an implementation method of a fracturing production integrated tubing string system, which is used for the above-mentioned fracturing production integrated tubing string, and specifically comprises the following steps:

[0015] S1, the fracturing string is lowered into the well to the designed position to perform fracturing construction;

[0016] S2, fracturing fluid flowback;

[0017] S3, lowering the production string into the fracturing string, combining the first hanger with the first hanging mandrel, inserting the insert seal into the sealing mandrel and sealingly cooperating with the sealing mandrel, and the perforated pipe corresponding to the gas lift mandrel;

[0018] S4, inject gas into the casing annulus to carry out gas lift and drainage production.

[0019] Optionally, when the integrated fracturing and production tubing also includes a plug, the tail end of the fracturing tubing is also connected to a plug hanging working cylinder. Before step S3, the plug is dropped into the fracturing tubing so that the plug and the plug hanging working cylinder are sealed and matched. Then, after step S3, the production tubing is lowered into the fracturing tubing, the plug is removed, and a new production channel is established.

[0020] Optionally, in step S1, staged fracturing construction is adopted.

[0021] The beneficial effects of the present invention are as follows: the integrated fracturing and production tubing system and implementation method proposed in the present invention firstly adopts a large-diameter fracturing tubing to fracture the production layer, effectively reducing the fracturing construction pressure, and having a post-fracturing gas lift and drainage function; then a small-diameter production tubing is adopted to produce gas, and at the same time, a perforated pipe corresponding to the gas lift working cylinder on the fracturing tubing is provided on the production tubing, so that the production tubing has a gas lift function, further improving the production efficiency of the gas well, and at the same time, since there is no need to pull out the fracturing tubing and disassemble the oil tree when lowering the production tubing, the operation cost can be effectively saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the integrated fracturing and production string system proposed in an embodiment of the present invention;

[0023] Figure 2 is an assembly diagram of a fracturing string and a production string proposed in an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of the structure of a production string proposed in an embodiment of the present invention;

[0025] Figure 4 It is an assembly structure diagram of the insert seal and perforation pipe, the seal working cylinder and the sliding sleeve type gas lift working cylinder proposed in the embodiment of the present invention.

[0026] In the figure: 1. fracturing string; 11. first oil pipe; 12. first suspension working cylinder; 13. sealing working cylinder; 14. gas lift working cylinder; 15. second suspension working cylinder; 16. downhole safety valve; 17. plug suspension working cylinder; 2. production string; 21. second oil pipe; 22. first hanger; 23. insert seal; 24. perforated pipe; 25. second hanger. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0028] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0030] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplified operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0031] This embodiment proposes a fracturing production integrated string system, which is installed in a wellbore and used in the field of low permeability gas reservoir development, especially offshore oil and gas field operations. Since the cost of offshore oil and gas field operations is relatively high, the conventional operation method of replacing the string takes a long time and is expensive. Therefore, the construction process based on the velocity string in this embodiment adds a gas lift function on the basis of the velocity string, further improving the liquid carrying capacity.

[0032] refer to Figure 1-4 As shown, the integrated fracturing and production string system proposed in this embodiment includes a fracturing string 1 and a production string 2. The fracturing string 1 is divided into a vertical and inclined well section fracturing string section and a horizontal fracturing string section, wherein the vertical and inclined well section fracturing string section includes a first oil pipe 11 and a first suspension mandrel 12, a sealing mandrel 13 and a gas lift mandrel 14 connected in sequence through the first oil pipe 11, and the horizontal fracturing string section is used to spray fracturing fluid into the production layer; the production string 2 includes a second oil pipe 21 and a first suspension mandrel 12, a sealing mandrel 13 and a gas lift mandrel 14 connected in sequence through the second oil pipe 21. The first hanger 22, the inserted seal 23 and the perforated tube 24, the tube wall of the perforated tube 24 is provided with an air inlet hole, the production tubing string 2 can be inserted into the fracturing tubing string 1, after the production tubing string 2 is inserted into the fracturing tubing string 1, the first hanger 22 and the first hanging working cylinder 12 are relative to fix the production tubing string 2, the inserted seal 23 is combined with the sealing working cylinder 13 to isolate the upper and lower pressures outside the inserted seal 23, the perforated tube 24 is opposite to the gas lift working cylinder 14, and the air inlet hole on the perforated tube 24 is opposite to the gas lift hole of the gas lift working cylinder 14.

[0033] The integrated fracturing and production tubing system in this embodiment combines the advantages of the velocity tubing and the gas lift operation, and utilizes the second oil pipe 21 with a smaller diameter than the first oil pipe 11 to preliminarily improve the liquid carrying capacity, and then utilizes the perforated pipe 24 connected to the second oil pipe 21 to correspond to the gas lift working cylinder 14 on the fracturing string 1, and by injecting gas into the annulus between the fracturing string 1 and the external casing, the gas lift working cylinder 14 is opened, and the gas enters the production tubing 2 through the gas inlet hole on the perforated pipe 24, so that the gas lift function of the production tubing 2 can be realized with the help of the gas lift working cylinder 14 on the fracturing string 1. At the same time, the gas lift working cylinder 14 on the fracturing string 1 can also realize its original gas lift function when backflowing after the fracturing operation, so as to carry out gas lift-assisted production, realize the integrated construction of fracturing, backflow and production, and improve the production efficiency of the gas well.

[0034] It is understandable that the diameters of the first oil pipe 11 and the second oil pipe 21 are relative. In actual construction, the first oil pipe 11 can be a 4-1 / 2" oil pipe, and the second oil pipe 21 can be a 2-3 / 8" oil pipe; or the first oil pipe 11 can be a 5" or 5-1 / 2" oil pipe, and the second oil pipe 21 can be a 2" or 1.9" oil pipe, as long as the second oil pipe 21 can be inserted into the first oil pipe 11.

[0035] The combination of the sealing mandrel 13 and the gas lift mandrel 14 on the vertical fracturing pipe string section can be set in multiples according to the depth of the gas well, that is, the sealing mandrel 13 and the gas lift mandrel 14 can be set alternately up and down but need to appear in groups. Correspondingly, the combination of the inserted seal 23 and the perforated pipe 24 on the production pipe string 2 can also be set in multiples and correspond one to one with the combination of the sealing mandrel 13 and the gas lift mandrel 14.

[0036] The perforated tube 24 is integrally formed with the second oil pipe 21 and can have the same diameter. The air inlet holes on the perforated tube 24 are circumferentially arranged around the perforated tube 24, which reduces the installation requirements for the angle of the perforated tube 24 itself when installing the production tubing string 2, and can make the air inlet holes correspond to the gas lift holes of the gas lift working cylinder 14 as much as possible, ensuring that the gas lift gas enters the production tubing string 2 through the shortest path.

[0037] Optionally, the gas lift mandrel 14 in this embodiment can be a sliding sleeve type gas lift mandrel. The sliding sleeve type gas lift mandrel includes an outer cylinder, an inner cylinder and a gas lift valve, wherein the gas lift valve is arranged on one side of the outer cylinder, a gas lift hole corresponding to the outlet of the gas lift valve is provided on the outer cylinder, the inner cylinder is located inside the outer cylinder and is sealed and slidably connected with the outer cylinder, and a through hole is provided on the inner cylinder. During the fracturing operation, the through hole is staggered with the gas lift hole, and the gas lift hole is closed, which can ensure that the gas lift valve in the gas lift mandrel 14 is not affected by the large-scale fracturing operation, and the high pressure generated by the fracturing does not contact the gas lift valve, thereby ensuring the safety of the gas lift valve; when the fracturing operation is completed and the gas lift operation is required, the inner cylinder is slid upward, the through hole corresponds to the gas lift hole, the gas lift hole is opened, the oil casing annulus is pressurized, and the gas enters the gas lift mandrel, that is, the fracturing string 1, through the gas lift valve. In specific implementation, the movement of the inner cylinder relative to the outer cylinder can be achieved by wire operation.

[0038] refer to Figure 1 and Figure 2 As shown, in this embodiment, the horizontal fracturing string section can be used to fractur e the production layer by staged fracturing. The process of staged fracturing belongs to a technology well known to those skilled in the art and will not be further described here. Specifically, it can be used in ways including but not limited to bare casing cementing, cementing sliding sleeve, open hole packer plus sliding sleeve, casing cementing perforation combined with packer plus sliding sleeve, etc. It should be noted that the size of the horizontal fracturing string section should match that of the vertical and inclined well section fracturing string section to perform ball dropping operations and realize staged fracturing.

[0039] The integrated fracturing and production tubing system in this embodiment also includes a plug, which can isolate the wellbore and realize the operation of lifting and lowering the production tubing 2 without well pressure, effectively avoiding reservoir damage. Correspondingly, the tail end of the vertical and inclined well section fracturing tubing is provided with a plug hanging working cylinder 17, and the plug can enter the plug hanging working cylinder 17 to seal the vertical and inclined well section fracturing tubing, and establish a new production channel by opening the plug after lowering the production tubing 2. The plug of the plug can be removed by chemical or mechanical methods. For example, the plug of the plug is made of soluble material, which can be a soluble alloy body. Then, chemical agents can be used to dissolve it and open the plug, or it can be designed as a shearing structure, and the shear pins are sheared by pressurizing the wellhead to make the plug fall off.

[0040] The vertical and inclined well section fracturing string section also includes a downhole safety valve 16, which can be closed in an emergency under abnormal circumstances to prevent blowouts and ensure the safety of oil and gas field facilities. The upper and lower ends of the downhole safety valve 16 are connected to the second suspension working cylinder 15 and the first suspension working cylinder 12 through the first oil pipe 11. Correspondingly, the production string 2 also includes a second hanger 25, and a section of the second oil pipe 21 is connected below the second hanger 25. The second hanger 25 can be combined with the second suspension working cylinder 15, and the lower end of the second oil pipe 21 connected to the second hanger 25 cannot be deeper than the downhole safety valve 16, that is, the entire production string 2 is divided into two sections that are not connected to each other by the downhole safety valve 16 to ensure the wellbore integrity barrier function of the downhole safety valve 16.

[0041] This embodiment also provides an implementation method of the above-mentioned integrated fracturing and production tubing system, which specifically includes the following steps:

[0042] S1: The fracturing string 1 is lowered into the well to the designed position for fracturing construction. For oil and gas layers with different characteristics, a horizontal fracturing construction pipe section adapted thereto can be used. Usually, segmented fracturing is adopted, and the method of ball-dropping and pressure-holding is used step by step until the fracturing construction of all the layers that need to be transformed is completed.

[0043] S2: Fracturing fluid flowback: If the natural blowdown cannot achieve the purpose of rapid flowback during the flowback process, gas can be injected into the casing annulus to open the gas lift working cylinder 14 and perform gas lift-assisted flow production.

[0044] S3: The plug is put into the plug hanging working cylinder 17 through wire operation or continuous oil pipe operation. After confirming that a reliable seal is formed, the production pipe string 2 is lowered into the vertical and inclined well section fracturing pipe string 1, wherein the first hanger 22 is combined with the first hanging working cylinder 12, the inserted seal 23 is inserted into the sealing working cylinder 13 and sealed with the sealing working cylinder 13, the perforated pipe 24 corresponds to the gas lift working cylinder 14, the second hanger 25 is combined with the second hanging working cylinder 15, and the lower end of the second oil pipe 21 connected to the second hanger 25 is not deeper than the downhole safety valve 16. At this time, ensure that the gas lift working cylinder 14 is in an open state.

[0045] S4: After the production string 2 is lowered into the preset position of the fracturing string 1, the plug is opened, and the production string 2 is connected with the horizontal fracturing string 1 below to form a new production channel. The plug opening method can be selected according to the structure of the plug, including but not limited to chemical dissolution or cutting the shear pin.

[0046] S5: Gas lift and drainage production: Inject gas into the annulus of the oil casing. The gas can enter the annulus between the production tubing string 2 and the fracturing tubing string 1 through the gas lift working cylinder 14 and enter the production tubing string 2 through the gas inlet holes on the perforated pipe 24, thereby realizing the gas lift function.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. The integrated tubing system for fracturing production is characterized by: include: A fracturing string (1), the fracturing string (1) being divided into a vertical and inclined well section fracturing string section and a horizontal fracturing string section, the vertical and inclined well section fracturing string section comprising a first oil pipe (11) and a first suspension mandrel (12), a sealing mandrel (13) and a gas lift mandrel (14) connected in sequence via the first oil pipe (11); A production tubing string (2), the production tubing string (2) comprising a second oil pipe (21) and a first hanger (22), an insert seal (23) and a perforated pipe (24) connected in sequence via the second oil pipe (21), wherein an air inlet hole is opened on the wall of the perforated pipe (24); The production tubing string (2) can be inserted into the fracturing tubing string (1), the first hanger (22) is opposite to the first hanging working cylinder (12), the insertion seal (23) is sealed with the sealing working cylinder (13), and the perforated tube (24) is opposite to the gas lift working cylinder (14).

2. The integrated fracturing and production tubing system according to claim 1, characterized in that: It also comprises a plug, and a plug hanging working cylinder (17) is arranged at the tail end of the vertical fracturing pipe string section, and the plug can enter into the plug hanging working cylinder (17) and cooperate with the plug hanging working cylinder (17) in a sealing manner.

3. The integrated fracturing and production tubing system according to claim 1, characterized in that: The vertical and inclined well section fracturing pipe string section also includes a downhole safety valve (16) and a second suspension working cylinder (15). The upper and lower ends of the downhole safety valve (16) are respectively connected to the second suspension working cylinder (15) and the first suspension working cylinder (12) through a section of the first oil pipe (11). The production pipe string (2) also includes a second hanger (25). A section of the second oil pipe (21) is connected below the second hanger (25). The second hanger (25) can be combined with the second suspension working cylinder (15).

4. The integrated fracturing and production tubing system according to claim 1, characterized in that: A plurality of air inlet holes are arranged circumferentially around the perforated tube (24).

5. The integrated fracturing and production tubing system according to claim 1, characterized in that: The sealing working cylinder (13) and the gas lift working cylinder (14) are arranged in multiple groups alternately up and down, the inserted seal (23) corresponds to the sealing working cylinder (13) one by one, and the perforated tube (24) corresponds to the gas lift working cylinder (14) one by one.

6. The integrated fracturing and production tubing system according to claim 1, characterized in that: The gas lift working cylinder (14) is a sliding sleeve type gas lift working cylinder, which comprises an outer cylinder, an inner cylinder and a gas lift valve. The gas lift valve is arranged on the outer cylinder. The outer cylinder is provided with a gas lift hole corresponding to the outlet of the gas lift valve. The inner cylinder is located in the outer cylinder and is sealingly and slidably connected with the outer cylinder. The inner cylinder is provided with a through hole.

7. The integrated fracturing and production tubing system according to claim 1, characterized in that: The first oil pipe (11) is a 4-1 / 2" oil pipe, and the second oil pipe (21) is a 2-3 / 8" oil pipe.

8. The implementation method of the integrated fracturing and production tubing system is characterized by: The method for implementing the integrated fracturing and production tubing system according to any one of claims 1 to 7 specifically comprises the following steps: S1, the fracturing string (1) is lowered into the well to the designed position to perform fracturing operation; S2, fracturing fluid flowback; S3, lowering the production tubing string (2) into the fracturing tubing string (1), combining the first hanger (22) with the first hanger mandrel (12), inserting the insert seal (23) into the sealing mandrel (13) and sealingly cooperating with the sealing mandrel (13), and the perforated pipe (24) corresponding to the gas lift mandrel (14); S4, inject gas into the casing annulus to carry out gas lift and drainage production.

9. The implementation method of the integrated fracturing and production tubing string system according to claim 8, characterized in that: The integrated fracturing and production tubing string also includes a plug, and the fracturing tubing string (1) is also connected to a plug hanging working cylinder (17). Before step S3, the plug is put into the fracturing tubing string (1) so that the plug and the plug hanging working cylinder (17) are sealed and matched. Then, after step S3, the production tubing string (2) is lowered into the fracturing tubing string (1), the plug is removed, and a new production channel is established.

10. The implementation method of the integrated fracturing and production tubing string system according to claim 8, characterized in that: In step S1, staged fracturing is performed.

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