A toe-end multi-cluster fracturing tool and use method thereof

Abstract

The present invention provides a toe-end multi-cluster fracturing tool and a method of using the tool. The tool at least includes a sleeve body, an upper joint and a lower joint. The upper joint and the lower joint are arranged at both ends of the sleeve body. A plurality of guide grooves are arranged on the side wall of the sleeve body. A strip protrusion is formed between two adjacent guide grooves. A plurality of radial through holes are arranged on the strip protrusion area. A blind hole is arranged concentrically with the radial through hole from the outside to the inside. A soluble plug is placed at the root of the blind hole, and the soluble plug is sealed and connected to the sleeve body; a metal baffle is arranged at the outer end of the blind hole, and a baffle hole is arranged at the center of the metal baffle; the metal baffle is fixedly connected to the sleeve body, and a cavity is left between the soluble plug and the metal baffle. The port of the present invention adopts a soluble pressure-bearing part to seal and open automatically at a time, or adopts a wellhead pressurization method to open, and the tool has strong adaptability; the port is fully opened in the later stage, the displacement is large, and the same opening conditions at all places can be used for multi-cluster fracturing.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas well fracturing and acidizing, and in particular relates to a toe-end multi-cluster fracturing tool and a use method thereof. Background Art

[0002] After cementing is completed, the wellbore is a closed cavity. In order to provide a pumping circulation channel for the subsequent fracturing transformation, it is necessary to open a casing at the toe end of the completion string and its external cement ring to connect the wellbore and the formation. For wells with a reservoir depth of 3500m and a horizontal section length of less than 1500m, continuous tubing or cables are conventionally used to carry downhole crawlers and use hydraulic or fire perforating guns to perforate to achieve this goal. For wells with a depth of more than 3500m and a horizontal section length of more than 1500m, the above method is ineffective due to the flexible characteristics of the continuous tubing and the force applied to press down. The crawler has requirements for the cleanliness of the wellbore, resulting in the inability of the tool to reach the toe of the tubing and cannot be modified. This problem has become a bottleneck problem in the current development of long horizontal section cementing horizontal wells. In order to solve this technical problem, the industry has actively explored the combination of establishing a fluid flow channel at the toe of the tubing with casing operations to save the perforating operation of lowering tools. This not only avoids the current situation of no technical means to deliver, but also reduces the problems of long operation time, low operation efficiency, high construction costs and high risks caused by lifting and lowering tools. Among the various types of casing connection tool methods provided by the prior art, there are methods of opening the fracturing ports by shear nails and bursting discs. Due to the heterogeneity of the materials, the port at the lowest pressure point is always opened first. After opening, the wellbore cannot increase the displacement indefinitely, resulting in the inability to open the fracturing ports at other positions, and thus multi-cluster fracturing cannot be achieved. Summary of the invention

[0003] In order to overcome the problem that the existing casing toe-end fracturing tools cannot realize multi-cluster fracturing, the present invention provides a toe-end multi-cluster fracturing tool and a method of use. The present invention has a large inner diameter and high wellbore integrity in the later stage; the port is blocked by multiple groups of single soluble pressure-bearing parts (soluble plugs), an auxiliary pressure relief chamber structure (cavity), the port is timed to open automatically, or opened by wellhead pressurization, and the tool has strong adaptability; the port is fully opened in the later stage, the displacement is large, and the same opening conditions at all places can be used for multi-cluster fracturing.

[0004] The technical solution adopted by the present invention is:

[0005] A toe-end multi-cluster fracturing tool comprises a sleeve body, an upper joint and a lower joint, wherein the upper joint and the lower joint are arranged at both ends of the sleeve body, a plurality of guide grooves are arranged on the side wall of the sleeve body, a strip protrusion is formed between two adjacent guide grooves, a plurality of radial through holes are arranged on the strip protrusion area, a blind hole is arranged concentrically with the radial through holes from outside to inside, a soluble plug is placed at the root of the blind hole, and the soluble plug is sealed and connected to the sleeve body; a metal baffle is arranged at the outer end of the blind hole, and a baffle hole is arranged in the center of the metal baffle; the metal baffle is fixedly connected to the sleeve body, a cavity is left between the soluble plug and the metal baffle, and the cavity is filled with sealing grease.

[0006] The dissolvable plug is made of a dissolvable material that can dissolve in water or saline solution.

[0007] The side of the dissolvable plug located inside the tube body is covered with a protective coating.

[0008] The dissolvable plug and the sliding sleeve body are sealed by a side O-ring.

[0009] An inner retaining spring groove and an outer retaining spring groove are provided at the connection between the metal baffle and the sliding sleeve body, and an inner retaining spring and an outer retaining spring are provided in the inner retaining spring groove and the outer retaining spring groove respectively.

[0010] The metal baffle is fixedly connected to the sliding sleeve body through an inner retaining spring and an outer retaining spring.

[0011] A method for using a toe-end multi-cluster fracturing tool, comprising the following specific steps:

[0012] Step 1: several tools are lowered into the first stage fracturing position along with the casing of the oil and gas well. The casing at the bottom of the tool is also connected with a pressure short-circuit. A preset amount of cement is injected into the well through the casing. A cementing plug is put into the oil and gas well, and a displacement fluid is followed. The cement flows from the pipe through the pressure short-circuit to the annulus and returns. When the displacement fluid in the pipe pushes the plug to the pressure short-circuit, the cementing is solidified, the cementing is completed, the cementing pressure test is completed, and a three-valve small wellhead is installed. The dissolvable plug dissolves until the pressure bearing capacity is lower than the later fracturing wellhead pressure limit or the seal fails;

[0013] Step 2: Replace the fracturing wellhead, test squeeze and pressurize the wellhead, the soluble plug loses its seal, the well fluid passes through the soluble plug position and further pushes the metal baffle, the cementing ring is pressure-ruptured, and the high-pressure liquid in the wellbore flows through the through holes and blind holes on the sleeve body of the tool, and the inside of the pipe is connected with the formation;

[0014] Step three: the high-pressure liquid in the wellbore further dissolves the remaining structure of the soluble plug, making the liquid flow channel formed by the through hole and the blind hole completely conductive, maximizing the tool flow channel, and ensuring that all ports at each cluster position are open in the same manner.

[0015] The displacement fluid is clean water or KCL solution, and the density of the KCL solution is not greater than 1.1%.

[0016] The beneficial effects of the present invention are:

[0017] The present invention provides a toe-end multi-cluster fracturing tool with a large inner diameter and high wellbore integrity in the later stage. The port adopts a soluble pressure-bearing part, that is, a soluble plug to be sealed and opened automatically at a scheduled time. When the soluble pressure-bearing part is not opened on time or is not opened completely, the wellhead pressurization method can be used to open it, and the tool has strong adaptability. The port is fully opened in the later stage, the displacement is large, and the same opening conditions at all places can be used for multi-cluster fracturing.

[0018] The following is a further description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the axial half-section structure of a toe-end multi-cluster fracturing tool of the present invention.

[0020] Figure 2 It is a right side view of a toe-end multi-cluster fracturing tool of the present invention.

[0021] Figure 3 yes Figure 1 A local enlarged view of point A in the figure.

[0022] In the figure, the reference numerals are: 1, sleeve body; 2, soluble plug; 3, metal baffle; 4, cavity; 5, sealing grease; 6, protective coating; 7, O-ring; 8, inner retaining spring; 9, outer retaining spring; 10, inner retaining spring groove; 11, upper joint; 12, lower joint; 13, guide groove; 14, strip protrusion; 15, through hole; 16, blind hole; 17, outer retaining spring groove. DETAILED DESCRIPTION

[0023] Example 1

[0024] In order to overcome the problem that the existing multi-cluster fracturing cannot be achieved, the present invention provides Figure 1-3 A toe-end multi-cluster fracturing tool and a method of use are shown. The invention has a large internal diameter and high wellbore integrity in the later stage; the port is blocked by multiple groups of single soluble pressure-bearing parts (soluble plugs), an auxiliary pressure relief chamber structure (cavity), the port is automatically opened at a timed interval, or opened by wellhead pressurization, and the tool has strong adaptability; the port is fully opened in the later stage, the displacement is large, and the same opening conditions at all locations can be used for multi-cluster fracturing.

[0025] A toe-end multi-cluster fracturing tool comprises a sleeve body 1, an upper joint 11 and a lower joint 12, wherein the upper joint 11 and the lower joint 12 are arranged at both ends of the sleeve body 1, a plurality of guide grooves 13 are arranged on the side wall of the sleeve body 1, a strip protrusion 14 is formed between two adjacent guide grooves 13, a plurality of radial through holes 15 are arranged in the strip protrusion 14 area, a blind hole 16 is arranged concentrically with the radial through holes 15 from outside to inside, a soluble plug 2 is placed at the root of the blind hole 16, and the soluble plug 2 is sealed and connected to the sleeve body 1; a metal baffle 3 is provided at the outer end of the blind hole 16, and a baffle hole is provided in the center of the metal baffle 3; the metal baffle 3 is fixedly connected to the sleeve body 1, a cavity 4 is left between the soluble plug 2 and the metal baffle 3, and the cavity 4 is filled with sealing grease 5.

[0026] like Figure 1 and Figure 2 As shown, the guide groove 13 provided on the side wall of the sleeve body 1 in the present invention can increase the annular flow area. Under the certain principle of satisfying the cementing annular space gap, the outer diameter of the tool that can be lowered can be larger than that of the tool without the guide groove structure, and the inner diameter of the tool can be larger at the same time, so that the integrity of the wellbore is good and the later operation is convenient. The strip protrusion 14 has a straightening effect and provides a mechanism installation position at the same time. The larger installation position can maintain a larger internal diameter. The sealing grease 5 is used to prevent the annular cement from entering and reserve a pressure relief space for the soluble plug 2 to rupture. The metal baffle 3 and the sleeve body 1 are not sealed. The annular pressure enters the cavity 4 through the baffle hole in the center of the metal baffle 3 and the gap between the metal baffle 3 and the sleeve body 1, resulting in a certain pressure on the outside of the soluble plug 2. After the cementing is completed, the pressure difference between the inside and outside of the soluble plug 2 is small. The required pressure is low, the local wall thickness is small, and the internal diameter of the tool is large.

[0027] The tool of the present invention is lowered into a predetermined position in an oil and gas well along with the wellbore casing, and a bump-pressure short-circuit is also connected at the bottom. A preset amount of cement is injected into the well through the casing; a cementing plug is put into the oil and gas well, and a displacement fluid (usually clean water or KCL, with a density of no more than 1.1%) is followed, and the cement flows from the pipe through the bump-pressure short-circuit to the annulus and returns. When the displacement fluid in the pipe pushes the plug to the bump-pressure short-circuit, the cementing is solidified, the cementing is completed, and a three-valve small wellhead is installed. The displacement fluid fills a toe-end multi-cluster fracturing tool, dissolving the soluble plug until its pressure-bearing capacity is lower than the pressure limit of the fracturing wellhead or the seal fails. The fracturing wellhead is replaced, and the wellhead is squeezed and pressurized. The soluble plug loses its seal, the metal baffle 3 is pushed open, the cement ring ruptures, and the high-pressure displacement fluid is connected to the formation from the through hole 15 and the blind hole 16 on the sleeve body of the toe-end multi-cluster fracturing tool. The displacement fluid further fills a toe-end multi-cluster fracturing tool, dissolving the remaining structure of the soluble plug, making the liquid flow channel formed by the through hole 15 and the blind hole 16 completely conductive, maximizing the tool flow channel, and making all ports at each cluster position open in the same manner, and even achieving the required displacement for fracturing, eliminating the pumping process and directly fracturing, thereby simplifying the process.

[0028] Embodiment 2:

[0029] Based on Example 1, in this embodiment, preferably, the soluble plug 2 is made of a soluble material that can be dissolved in water or a saline solution.

[0030] The soluble material in the present invention may be a metal soluble material. The metal soluble material is composed of a soluble metal material composition, which mainly includes one or more active metals in a large proportion, and a small amount of one or more alloying products, and the active metal elements contained therein mainly include: aluminum (Al), gallium (Ga), indium (In), zinc (Zn) and bismuth (Bi). Gallium (Ga), indium (In), zinc (Zn), bismuth (Bi), tin (Sn) and aluminum (Al) compositions can control activity and degradability under specific conditions. The soluble material synthesized by them can be completely dissolved. The metal soluble material and its preparation process provided by the present invention are both prior art and will not be further described in the present invention.

[0031] Preferably, the inner side of the pipe body of the soluble plug 2 is covered with a protective coating 6. The protective coating 6 can delay the reaction of the soluble plug 2 with water or salt solution, prevent the soluble plug 2 from dissolving, thereby weakening the pressure bearing capacity of the soluble plug 2 and opening it in advance, ensuring that the cementing process is more reliable and safe.

[0032] Preferably, the soluble plug 2 and the sleeve body 1 are sealed by a side O-ring 7 .

[0033] Preferably, an inner retaining spring groove 10 and an outer retaining spring groove 17 are provided at the connection between the metal baffle plate 3 and the sleeve body 1 , and an inner retaining spring 8 and an outer retaining spring 9 are respectively provided in the inner retaining spring groove 10 and the outer retaining spring groove 17 .

[0034] Preferably, the metal baffle 3 is fixedly connected to the sleeve body 1 via an inner retaining spring 8 and an outer retaining spring 9 .

[0035] like Figure 1 and Figure 3 As shown, in the specific implementation process of the present invention, the sliding sleeve body 1 of a toe segment multi-cluster fracturing tool provided by the present invention is sequentially connected to the wellbore casing through the upper joint 11 and the lower joint 12, and is lowered along the wellbore casing to a predetermined position in a well with a well depth of more than 3500m and a horizontal section length of more than 1500m. After positively squeezing cement for a period of time, a cementing plug is put in, and a displacement fluid (usually clean water or KCL, with a density of no more than 1.1%) is followed. The cement flows from the pipe through the impact pressure short-circuit to the annulus and returns. When the displacement fluid in the pipe pushes the plug to the impact pressure short-circuit, the cementing is thickened, the cementing is completed, the cementing pressure test is completed, and the three-valve small wellhead is installed.

[0036] When the displacement fluid fills a toe-end multi-cluster fracturing tool, the soluble plug is dissolved until its pressure bearing capacity is lower than the later fracturing wellhead pressure limit or the seal fails, and the remaining structure of the soluble plug 2 continues to be dissolved, the fracturing wellhead is changed, and the wellhead is squeezed and pressurized. After the wellhead pressure value is greater than the fracture pressure value of the soluble plug 2 (after the wellbore pressure reaches 40MPa), the metal baffle 3 is pushed open, the cement ring is broken, and the high-pressure displacement fluid is connected to the formation from the through hole 15 and the blind hole 16 on the sleeve body 1 of a toe-end sliding sleeve that can be used for multi-cluster perforating.

[0037] When the displacement fluid further fills a toe-section multi-cluster fracturing tool, the remaining structure of the soluble plug 2 continues to be dissolved, so that the liquid flow channel formed by the through hole 15 and the blind hole 16 is fully conductive, the tool flow channel is maximized, and all ports at each cluster position are opened in the same condition, and even the displacement required for fracturing can be achieved, eliminating the pumping process and directly fracturing, thereby simplifying the process.

[0038] Embodiment 3:

[0039] Based on Example 1 or 2, this embodiment provides a method for using a toe-end multi-cluster fracturing tool, and the specific steps are:

[0040] Step 1: several tools are lowered into the first stage fracturing position along with the casing of the oil and gas well. The casing at the bottom of the tool is also connected with a bump pressure short-circuit. A preset amount of cement is injected into the well through the casing. A cementing plug is put into the oil and gas well, and a displacement fluid is chased. The cement flows from the pipe through the bump pressure short-circuit to the annulus and returns. When the displacement fluid in the pipe pushes the plug to the bump pressure short-circuit, the cementing is solidified, the cementing is completed, the cementing pressure test is completed, and a three-valve small wellhead is installed. The dissolvable plug 2 dissolves until the pressure bearing capacity is lower than the later fracturing wellhead pressure limit or the seal fails;

[0041] Step 2: Replace the fracturing wellhead, test squeeze and pressurize the wellhead, the soluble plug 2 loses its seal, the well fluid passes through the soluble plug 2 and further pushes the metal baffle 3, the cement ring is pressure-ruptured, and the high-pressure liquid in the wellbore flows through the through hole 15 and the blind hole 16 on the sleeve body 1 of the tool, and the inside of the pipe is connected with the formation;

[0042] Step three, the high-pressure liquid in the wellbore further dissolves the remaining structure of the soluble plug 2, so that the liquid flow channel formed by the through hole 15 and the blind hole 16 is completely conductive, so that the tool flow channel is maximized, and all ports at each cluster position are opened in the same condition.

[0043] The displacement fluid is clean water or KCL solution, and the density of the KCL solution is not greater than 1.1%.

[0044] The sealing of the soluble plug 2 and the sleeve body 1 and the fixed connection of the metal baffle 3 and the sleeve body 1 in the present invention are only a preferred example used to illustrate the present invention. Those skilled in the art can understand that the sealing and connection can also be replaced by a variety of sealing and connection methods known in the prior art, such as copper pad end face sealing and welding. The through and blind holes have corresponding features.

[0045] The tool provided by the present invention has a smaller outer diameter and length than the casing centralizer, and its outer shape adopts the structure of the centralizing guide groove 13, with a large annular space gap, and the inner diameter can be no less than the same as the production casing. No special cementing accessories are required, and the casing running, circulation displacement and cementing operations are not affected. The wellbore integrity is high in the later stage; the port is blocked by multiple groups of single soluble pressure-bearing parts, and the pressure relief cavity structure is auxiliary. The port is automatically opened at a time, or opened by wellhead pressurization, and the tool has strong adaptability; the port is completely opened in the later stage, the flow channel and the pumping displacement are large, and the displacement required for fracturing can even be achieved, eliminating the pumping process and directly fracturing, thereby simplifying the process; the opening conditions of the ports at each cluster position are the same, and can be used for toe-end multi-cluster fracturing.

[0046] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The components and structures not described in detail in this embodiment are well-known components and common structures or common means in the industry, and are not described here one by one.

Claims

1. A method for using a toe-end multi-cluster fracturing tool, characterized in that: A toe-end multi-cluster fracturing tool is used, the tool comprising a sleeve body (1), an upper joint (11) and a lower joint (12), the upper joint (11) and the lower joint (12) being arranged at both ends of the sleeve body (1), a plurality of guide grooves (13) being arranged on the side wall of the sleeve body (1), a strip-shaped protrusion (14) being formed between two adjacent guide grooves (13), a plurality of radial through holes (15) being arranged on the strip-shaped protrusion (14), and the radial through holes (15) being connected to the strip-shaped protrusion (14) by the outside. A blind hole (16) is concentrically arranged inwardly, a soluble plug (2) is placed at the root of the blind hole (16), and the soluble plug (2) is sealed and connected to the sleeve body (1); a metal baffle (3) is arranged at the outer end of the blind hole (16), and a baffle hole is arranged at the center of the metal baffle (3); the metal baffle (3) is fixedly connected to the sleeve body (1), a cavity (4) is left between the soluble plug (2) and the metal baffle (3), and the cavity (4) is filled with sealing grease (5) ； The dissolvable plug (2) is made of a dissolvable material that can be dissolved in water or saline solution; a surface of the dissolvable plug (2) located inside the tube body is covered with a protective coating (6); The specific steps of using the toe multi-cluster fracturing tool are as follows: Step 1: lower several tools into the first stage fracturing position along with the casing of the oil and gas well. The casing at the bottom of the tool is also connected with a short-circuit. A preset amount of cement is injected into the well through the casing. A cementing plug is put into the oil and gas well, and a displacement fluid is followed. The cement flows from the pipe through the short-circuit to the annulus and returns. When the displacement fluid in the pipe pushes the plug to the short-circuit, the cementing is solidified, the cementing is completed, the cementing pressure test is completed, and a three-valve small wellhead is installed. The dissolvable plug (2) dissolves until the pressure bearing capacity is lower than the later fracturing wellhead pressure limit or the seal fails; Step 2: Replace the fracturing wellhead, test squeeze and pressurize the wellhead, the soluble plug (2) loses its seal, the well fluid passes through the soluble plug (2) and further pushes the metal baffle (3), the cement ring is pressure-ruptured, and the high-pressure liquid in the wellbore flows through the through hole (15) and the blind hole (16) on the sleeve body (1) of the tool, and the inside of the pipe is connected with the formation; In step three, the high-pressure liquid in the wellbore further dissolves the remaining structure of the soluble plug (2), so that the liquid flow channel formed by the through hole (15) and the blind hole (16) is completely conductive, the tool flow channel is maximized, and all ports at each cluster position are opened in the same manner.

2. The method for using a toe-end multi-cluster fracturing tool according to claim 1, characterized in that: The soluble plug (2) and the sliding sleeve body (1) are sealed by a side O-ring (7).

3. The method for using a toe-end multi-cluster fracturing tool according to claim 1, characterized in that: An inner retaining spring groove (10) and an outer retaining spring groove (17) are provided at the connection between the metal baffle plate (3) and the sleeve body (1), and an inner retaining spring (8) and an outer retaining spring (9) are provided in the inner retaining spring groove (10) and the outer retaining spring groove (17), respectively.

4. The method for using a toe-end multi-cluster fracturing tool according to claim 3, characterized in that: The metal baffle (3) is fixedly connected to the sleeve body (1) via an inner retaining spring (8) and an outer retaining spring (9).

5. The method for using a toe-end multi-cluster fracturing tool according to claim 1, characterized in that: The displacement fluid is clean water or KCL solution, and the density of the KCL solution is not greater than 1.1%.

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