Horizontal well end fracturing pipe column for carbon dioxide fracturing, multilayer fracturing pipe column and construction method

Abstract

The invention relates to the technical field of shaft fracturing, in particular to a carbon dioxide fracturing horizontal well end fracturing tubular column, a multi-layer fracturing tubular column and a construction method.The carbon dioxide fracturing horizontal well end fracturing tubular column comprises a fracturing oil pipe, a first sand prevention hydraulic anchor, a first K344 expanding packer and a short-time throttling end sand blower; a first sand prevention hydraulic anchor and a first K344 expanding packer are sequentially installed on the fracturing oil pipe from left to right, the short-time throttling end sand blaster is installed at the end of the fracturing oil pipe and comprises a shell, a throttling piece and a pressing cap, an installation groove with a rightward opening is formed in the inner side of the right portion of the shell, the throttling piece is located in the installation groove, and the pressing cap is connected with the shell. The throttling piece is in a U shape with a leftward opening, the outer portion of the throttling piece is thick, the middle portion of the throttling piece is thin, and the middle sheet portion of the throttling piece can be eroded. The short-time throttling end sand blaster is reasonable and compact in structure and convenient to use, and has the capability of simultaneously meeting the requirements of low-displacement carbon dioxide pump injection and high-displacement fracturing construction by arranging the short-time throttling end sand blaster with the throttling piece capable of being eroded.

Description

Technical Field

[0001] This invention relates to the field of wellbore fracturing technology, specifically a horizontal wellhead fracturing string, a multi-layer fracturing string, and a construction method for carbon dioxide fracturing. Background Technology

[0002] Segmented fracturing string technology is a relatively mature fracturing stimulation technique. It combines tubing with fracturing packers, sliding sleeve jetting devices, and chokes to achieve precise segmented fracturing operations of 1-5 layers or even more. The combined operation of packers, hydraulic anchors, and chokes isolates the target fracturing layer. In vertical wells, segmented fracturing string technology can use compression-type and expansion-type rubber sleeve packers as the core design string. In highly deviated and horizontal wells, expansion-type rubber sleeve packers are often used as the core design string. In older wells, especially older horizontal wells undergoing repeated fracturing stimulation, there may be deformation in certain sections of the wellbore or a reduction in well diameter at certain points. Standard-sized internal compression packers cannot be lowered to the intended position, or their inner diameter is too small, making fracturing operations inconvenient. Existing jetting devices are not suitable for simultaneously injecting small volumes of carbon dioxide and large volumes of fracturing fluid to achieve fracturing. Summary of the Invention

[0003] This invention provides a horizontal well end fracturing string, a multi-layer fracturing string, and a construction method for carbon dioxide fracturing, which overcomes the shortcomings of the prior art and can effectively solve the problems of time-consuming and labor-intensive construction, low construction efficiency, and safety hazards.

[0004] One of the technical solutions of the present invention is achieved through the following measures: a fine fracturing string for a horizontal well with carbon dioxide fracturing, including fracturing tubing, a first sand-control hydraulic anchor, a first K344 expansion packer, and a short-time throttling end sandblaster. The first sand-control hydraulic anchor and the first K344 expansion packer are installed sequentially from left to right on the fracturing tubing. The short-time throttling end sandblaster is installed at the end of the fracturing tubing. The short-time throttling end sandblaster includes a shell, a throttling plate, and a pressure cap. The right inner side of the shell is provided with an installation groove opening to the right. The throttling plate is located in the installation groove. The throttling plate is U-shaped with an opening to the left. The throttling plate is thick on the outside and thin in the middle. The thin part in the middle of the throttling plate can be eroded. The middle part of the throttling plate is provided with a first sandblasting port that runs through from left to right. The left side of the pressure cap is threaded to the inner side of the upper shell to tighten the outside of the throttling plate.

[0005] The second technical solution of the present invention is achieved through the following measures: a multi-layer fracturing string, comprising a horizontal wellhead fracturing string for carbon dioxide fracturing, a connector, a safety release joint, and at least one intermediate fracturing string. The intermediate fracturing string includes a second sand-control hydraulic anchor, a second K344 expansion packer, and a short-time throttling sleeve sprayer. From left to right, the left side of the fracturing tubing is sequentially provided with the second sand-control hydraulic anchor and the second K344 expansion packer. A short-time throttling sleeve sprayer is installed on the fracturing tubing between the second K344 expansion packer and the first sand-control hydraulic anchor. The short-time throttling sleeve sprayer includes an upper shell, a lower shell, a throttling tube, and a sleeve valve core. The upper shell and the lower shell are mounted together by a lock screw. The lower housing has two elongated grooves that run through the inside and outside of the circumference. A throttling tube is provided between the upper and lower housings. The throttling tube is thicker on the left and thinner on the right. The thin part on the right side of the throttling tube can be eroded. The right side of the throttling tube can cover the elongated grooves. The middle of the throttling tube has a second sandblasting port that runs through the inside and outside of the circumference. The left end of the sliding sleeve valve core is located inside the upper housing, and the right end of the sliding sleeve valve core is located inside the lower housing and below the elongated grooves. The right side of the sliding sleeve valve core is connected to the lower housing by a shear pin. A receiver is installed on the fracturing tubing on the right side of the first K344 expansion packer. The receiver is a short section with stepped holes on the inside. The receiver can block the sliding sleeve valve core and form a seal. A safety release connector is provided on the fracturing tubing on the left side of the middle fracturing string located at the far left.

[0006] The following are further optimizations and / or improvements to the above-mentioned technical solution: Preferably, the outer diameter of the sliding sleeve valve core is smaller on the left and larger on the right.

[0007] Preferably, the short-time throttling sliding sleeve sandblaster also includes sealing rings, with a sealing ring provided between the upper housing and the sliding sleeve valve core, and a sealing ring provided between the lower housing and the sliding sleeve valve core.

[0008] Preferably, the sealing sleeves of the first K344 expansion packer and the second K344 expansion packer, the rubber seals of the anchor teeth of the first and second sand-proof hydraulic anchors, the safety release joint, and the sealing ring of the short-time throttling sleeve sandblaster are all made of modified rubber materials mainly composed of hydrogenated nitrile rubber.

[0009] Preferably, the first K344 expansion packer and the second K344 expansion packer have the same dimensions, namely K344-108 packer or K344-106 packer. The K344-108 packer has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the K344-106 packer has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both packers are heat resistant up to 150℃ and have an internal pressure resistance of 70MPa. The first and second sand-proof hydraulic anchors have the same dimensions, namely SLM-108 hydraulic anchor or SLM-106 hydraulic anchor. The SLM-108 hydraulic anchor has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the SLM-106 hydraulic anchor has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both hydraulic anchors are heat resistant up to 150℃ and have an internal pressure resistance of 70MPa.

[0010] The third technical solution of the present invention is achieved through the following measures: a construction method, which is carried out according to the following steps: First, lower the fracturing tubing into the wellbore to the predetermined position, ensuring that the setting position is appropriate and can seal the formation to be modified. Then, align the short-time throttling end sandblaster and the short-time throttling sliding sleeve sandblaster with the target formation to be modified. Construction begins at the end location: Carbon dioxide is pumped in, rapidly increasing the discharge rate to 1m. 3 At a speed of / min, the high-speed flowing liquid passes through the first blasting orifice of the short-time throttling end blaster, forming a throttling pressure of ≥1.3MPa, which assists in the expansion and setting of the first K344 expansion packer sleeve. Then, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling vane of the short-time throttling end sandblaster; After the pre-carbon dioxide injection was completed, large-scale fracturing operations began with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3 At a flow rate of 10 m³ / min, proppant with a sand concentration of 3% is added to the fracturing fluid to create a slug flow. The high-speed flowing sand-laden fluid then passes through the first nozzle of the short-time throttling end-jet jet, which has a diameter of φ22mm. After the throttling plate is eroded and worn away, the first nozzle of the short-time throttling end-jet jet is enlarged to φ50mm, further increasing the fracturing pump injection rate to 10 m³ / min. 3 / min-12m 3 / min, complete the fracturing operation at the end position; The second fracturing operation is carried out by dropping a steel ball of the corresponding size into the tubing. The steel ball falls into the sliding valve core of the short-time throttling sliding sleeve sandblaster and is pressurized. The shear pin is sheared off, and the sliding valve core moves to the right, exposing the second sandblasting port. Under the hydraulic push of the fluid, the sliding valve core passes through the first anti-sand hydraulic anchor and the first K344 expansion packer to reach the receiver, where it cooperates to form a seal and block the lower fracturing string. Start pumping carbon dioxide, quickly increasing the discharge rate to 1m³. 3 At a flow rate of / min, high-speed flowing liquid passes through the second blasting orifices on both sides of the short-time throttling sliding sleeve blaster. These second orifices have a diameter of φ18mm, creating a throttling pressure ≥1.2MPa. This pressure serves as the starting pressure for the first K344 expansion packer, assisting in the expansion and setting of the packer's rubber sleeve. Subsequently, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling tube of the short-time throttling sliding sleeve sandblaster; After the second stage of pre-carbon dioxide injection is completed, large-scale fracturing operations begin with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3 At a flow rate of / min, proppant with a sand concentration of 3% is added to the fracturing fluid in a slug flow. The high-speed flowing sand-bearing fluid then passes through the second spray nozzles on the throttling tubes on both sides of the short-time throttling sleeve sprayer. These second spray nozzles, with a diameter of φ18mm, erode and wear down the throttling tubes, eventually expanding into long slot-shaped holes of 30mm*120mm, further increasing the fracturing pump injection rate to 10m³ / min. 3 / min-12m 3 / min, complete the second stage of fracturing operation; The subsequent fracturing operations are carried out in the same manner as the second fracturing operation. After the operation is completed, once the pressure in the well has diffused and balanced, the first K344 expansion packer and the second K344 expansion packer will automatically release.

[0011] The present invention has a reasonable and compact structure and is easy to use. By setting a short-time throttling end sandblaster with erosion-capable throttling plates, it has the ability to simultaneously meet the requirements of low-displacement carbon dioxide pumping and high-displacement fracturing operations. Attached Figure Description

[0012] Appendix Figure 1 This is a schematic diagram of the front cross-sectional structure according to an embodiment of the present invention.

[0013] Appendix Figure 2 For the appendix Figure 1 Enlarged cross-sectional view of the short-time throttling end sandblaster.

[0014] Appendix Figure 3This is a top-view enlarged structural diagram of a short-time throttling sliding sleeve sandblasting device.

[0015] Appendix Figure 4 For the appendix Figure 1 Enlarged cross-sectional view of the short-time throttling sleeve sandblasting device.

[0016] Appendix Figure 5 For the appendix Figure 3 A cross-sectional enlarged schematic diagram of the throttling tube in the diagram.

[0017] The codes in the attached diagram are as follows: 1 is fracturing tubing, 2 is the first sand-control hydraulic anchor, 3 is the first K344 expansion packer, 4 is the short-time throttling end sandblaster, 5 is the casing, 6 is the throttling plate, 7 is the pressure cap, 8 is the connector, 9 is the safety release connector, 10 is the second sand-control hydraulic anchor, 11 is the second K344 expansion packer, 12 is the short-time throttling sliding sleeve sandblaster, 13 is the upper casing, 14 is the lower casing, 15 is the throttling pipe, 16 is the sliding sleeve valve core, 17 is the stop screw, 18 is the elongated groove, 19 is the second sandblasting nozzle, 20 is the shear pin, 21 is the sealing ring, and 22 is the first sandblasting nozzle. Detailed Implementation

[0018] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0019] In this invention, for ease of description, the description of the relative positions of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as front, back, top, bottom, left, right, etc. The positional relationships are determined based on the layout direction of the attached diagram in the instruction manual.

[0020] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1-5 As shown, the fine fracturing string for a horizontal well using carbon dioxide fracturing includes fracturing tubing 1, a first sand-control hydraulic anchor 2, a first K344 expansion packer 3, and a short-time throttling end sandblaster 4. The first sand-control hydraulic anchor 2 and the first K344 expansion packer 3 are installed sequentially from left to right on the fracturing tubing 1. The short-time throttling end sandblaster 4 is installed at the end of the fracturing tubing 1. The short-time throttling end sandblaster 4 includes a housing 5, a throttling plate 6, and a pressure cap 7. The right inner side of the housing 5 has an installation groove with an opening to the right. The throttling plate 6 is located in the installation groove. The throttling plate 6 is U-shaped with an opening to the left. The throttling plate 6 is thick on the outside and thin in the middle. The thin part in the middle of the throttling plate 6 can be eroded. The middle of the throttling plate 6 has a first sandblasting port 22 that runs through from left to right. The left side of the pressure cap 7 is threaded to the inner side of the upper housing 13 to tighten the outside of the throttling plate 6.

[0021] Depending on the required casing inner diameter, either the K344-108 packer with a maximum outer diameter of φ108mm and an inner diameter of φ52mm, or the K344-106 packer with a maximum outer diameter of φ106mm and an inner diameter of φ50mm can be selected. Both specially designed packers have large inner diameters to meet fracturing requirements. By incorporating erosion-resistant throttling plates 6, pre-pressurized carbon dioxide can be injected through the first blasting port 22 at low flow rates, creating throttling pressure that allows the first K344 expandable packer 3 to expand and set, after which a further pumping flow rate of 0.5m³ can be achieved. 3 / min-2m 3 The carbon dioxide flow rate of / min, along with the throttling pressure, will not damage the throttling plate 6 of the short-term throttling end sandblaster 4. During subsequent fracturing, the large volume of fracturing fluid passing through the throttling plate 6 will erode the thin section, enlarging the first sandblasting orifice 22, effectively reducing the throttling pressure of the pressure tool and lowering the ground construction pressure. This ensures a further increase in the fracturing fluid injection rate, typically reaching 10m³ / min. 3 / min-12m 3 After the pressure differential is balanced upon completion of the operation, the first K344 expandable packer 3 will automatically unseal, facilitating the operation of the tubing string in a horizontal well. This invention can inject carbon dioxide at a small displacement to expand and set the first K344 expandable packer 3, and can also pump fracturing fluid to increase the orifice diameter of the first sandblasting nozzle 22, achieving large-scale fracturing with a large displacement, realizing variable fluid and variable displacement operation from small to large displacement.

[0022] Example 2: As shown in the attached document Figure 1-5As shown, the multi-layer fracturing string includes a horizontal wellhead fracturing string for carbon dioxide fracturing, a connector 8, a safety release connector 9, and at least one intermediate fracturing string. The intermediate fracturing string includes a second sand-control hydraulic anchor 10, a second K344 expansion packer 11, and a short-time throttling sleeve sprayer 12. The left side of the fracturing tubing 1 is sequentially equipped with the second sand-control hydraulic anchor 10 and the second K344 expansion packer 11 from left to right. A short-time throttling sleeve sprayer 12 is installed on the fracturing tubing 1 between the second K344 expansion packer 11 and the first sand-control hydraulic anchor 2. The short-time throttling sleeve sprayer 12 includes an upper shell 13, a lower shell 14, a throttling tube 15, and a sleeve valve core 16. The upper shell 13 and the lower shell 14 are installed together by a retaining screw 17. Two inner sleeves are evenly distributed around the circumference of the middle of the lower shell 14. An elongated groove 18 extends outwards. A throttling pipe 15 is provided between the upper housing 13 and the lower housing 14. The throttling pipe 15 is thicker on the left and thinner on the right. The thin part on the right side of the throttling pipe 15 can be eroded. The right side of the throttling pipe 15 can cover the elongated groove 18. A second sandblasting port 19 that extends inwards and outwards is provided in the middle of the throttling pipe 15. The left end of the sliding sleeve valve core 16 is located inside the upper housing 13, and the right end of the sliding sleeve valve core 16 is located inside the lower housing 14 and below the elongated groove 18. The right side of the sliding sleeve valve core 16 is connected to the lower housing 14 by a shear pin 20. A receiver 8 is installed on the fracturing tubing 1 on the right side of the first K344 expansion packer 3. The receiver 8 is a short section with a stepped hole on the inner side. The receiver 8 can block the sliding sleeve valve core 16 and form a seal. A safety release connector 9 is provided on the fracturing tubing 1 on the left side of the middle fracturing string located at the far left.

[0023] Multiple intermediate fracturing strings can be installed to sequentially fracture the fracturing layers, meeting different process requirements. The inner diameter of the sliding valve core 16 is designed according to the number of layers. For example, in a three-layer fracturing operation, the inner diameter of the sliding valve core 16 can be in three increments: φ50mm, φ45mm, and φ40mm. The inner diameter of the rightmost sliding valve core 16 is the smallest, allowing for the deployment of small-diameter steel balls. After erosion at the second blasting nozzle, the blasting nozzle becomes an elongated groove 18, 30mm*120mm, with a flow area equivalent to that of a φ62mm circular orifice. The elongated groove 18 has greater strength than the lower shell of the φ62mm circular orifice, which is beneficial for fracturing operations.

[0024] The above-mentioned multi-layer fracturing string can be further optimized and / or improved according to actual needs: Example 3: As shown in the attached document Figure 3 , 4 As shown, the outer diameter of the sliding valve core 16 is smaller on the left and larger on the right. This structure ensures that it is not blocked by the burrs or metal shavings of the pin, and ensures that the second sandblasting port 19 can open normally.

[0025] Example 4: As shown in the appendix Figure 4As shown, the short-time throttling sliding sleeve sandblaster 12 also includes sealing rings 21. Sealing rings 21 are provided between the upper housing 13 and the sliding sleeve valve core 16, and between the lower housing 14 and the sliding sleeve valve core 16. By providing sealing rings 21 to seal both ends of the throttling tube 15, liquid impurities are prevented from entering between the sliding sleeve valve core 16 and the throttling tube 15, thus avoiding wear on the throttling tube 15.

[0026] Example 5: As shown in the attached document Figure 1-4 As shown, the sealing sleeves of the first K344 expansion packer 3 and the second K344 expansion packer 11, the rubber seals of the anchor teeth of the first sand-proof hydraulic anchor 2 and the second sand-proof hydraulic anchor 10, the safety release connector 9, and the sealing ring 21 of the short-time throttling sleeve sandblaster 12 are all made of modified rubber material mainly composed of hydrogenated nitrile rubber. This material can maintain its performance without degradation for a certain period of time in a carbon dioxide environment.

[0027] Example 6: As attached Figure 1 As shown, the first K344 expansion packer 3 and the second K344 expansion packer 11 have the same dimensions, and are either K344-108 packers or K344-106 packers. The maximum outer diameter of the K344-108 packer is φ108mm and the inner diameter is φ52mm. The maximum outer diameter of the K344-106 packer is φ106mm and the inner diameter is φ50mm. Both packers are heat resistant up to 150℃ and have an internal pressure resistance of 70MPa. The first sand-proof hydraulic anchor 2 and the second sand-proof hydraulic anchor 10 have the same dimensions, and are either SLM-108 hydraulic anchors or SLM-106 hydraulic anchors. The maximum outer diameter of the SLM-108 hydraulic anchor is φ108mm and the inner diameter is φ52mm. The maximum outer diameter of the SLM-106 hydraulic anchor is φ106mm and the inner diameter is φ50mm. Both hydraulic anchors are heat resistant up to 150℃ and have an internal pressure resistance of 70MPa.

[0028] For construction within casing with an outer diameter of φ139.7mm and an inner diameter of φ124.26mm, a φ101.6mm micro-coupling tubing is used in conjunction with a K344-108 expandable packer and matching tools. For construction within casing with an outer diameter of φ139.7mm and an inner diameter ≤φ121.36mm, a combination of φ101.6mm micro-coupling tubing and φ88.9mm micro-coupling tubing is used in conjunction with a K344-106 expandable packer and matching tools. This tubing string technology has the ability to adapt small-diameter tools to large-diameter casings, and is particularly suitable for construction in old wells after slight deformation and diameter reduction.

[0029] Example 7: As attached Figure 1-5 As shown, the construction method shall be carried out according to the following steps: First, lower the fracturing tubing 1 into the wellbore to the predetermined position, ensuring that the setting position is appropriate and can seal the layer that needs to be modified. Then, align the short-time throttling end sandblaster 4 and the short-time throttling sliding sleeve sandblaster 12 with the target layer to be modified. Construction begins at the end location: Carbon dioxide is pumped in, rapidly increasing the discharge rate to 1m. 3 At a flow rate of / min, the high-speed flowing liquid passes through the first blasting port 22 of the short-time throttling end blaster 4, forming a throttling pressure of ≥1.3MPa. This pressure assists in the expansion and setting of the first K344 expansion packer 3 rubber sleeve. Then, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling plate 6 of the short-time throttling end sandblaster 4; After the pre-carbon dioxide injection was completed, large-scale fracturing operations began with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3 At a flow rate of 10 m³ / min, proppant with a sand concentration of 3% is added to the fracturing fluid to create a slug flow. The high-speed flowing sand-laden fluid then passes through the first nozzle 22 of the short-time throttling end-jet jetter 4. The first nozzle 22 has a diameter of φ22mm, which erodes and wears down the throttling plate 6. The first nozzle 22 of the short-time throttling end-jet jetter 4 then expands to φ50mm, further increasing the fracturing pump injection rate to 10 m³ / min. 3 / min-12m 3 / min, complete the fracturing operation at the end position; In the second fracturing operation, a steel ball of the corresponding size is dropped into the tubing. The steel ball falls into the sliding valve core 16 of the short-time throttling sliding sleeve sandblaster 12 and is pressurized. The shear pin 20 is sheared off, and the sliding valve core 16 moves to the right, exposing the second sandblasting port 19. Under the hydraulic push of the fluid, the sliding valve core 16 passes through the first anti-sand hydraulic anchor 2 and the first K344 expansion packer 3, and reaches the receiver 8, where it cooperates to form a seal and block the lower fracturing string. Start pumping carbon dioxide, quickly increasing the discharge rate to 1m³. 3 At a flow rate of / min, the high-speed flowing liquid passes through the second blasting orifices 19 on both sides of the short-time throttling sliding sleeve blaster 12. The second blasting orifices 19 have a diameter of φ18mm, forming a throttling pressure of ≥1.2MPa. This pressure serves as the starting pressure for the first K344 expansion packer 3, assisting in the expansion and setting of the packer sleeve. Subsequently, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling tube 15 of the short-time throttling sliding sleeve sandblaster 12; After the second stage of pre-carbon dioxide injection is completed, large-scale fracturing operations begin with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3At a flow rate of / min, a proppant slug flow with a sand concentration of 3% is added to the fracturing fluid. The high-speed flowing sand-bearing fluid then passes through the second spray nozzles 19 on the throttling pipes 15 on both sides of the short-time throttling sleeve sprayer 12. The second spray nozzles 19 have a diameter of φ18mm, which erode and wear down the throttling pipes 15, enlarging the second spray nozzles 19 into long slot-shaped holes of 30mm*120mm, further increasing the fracturing pump injection rate to 10m³ / min. 3 / min-12m 3 / min, complete the second stage of fracturing operation; The subsequent fracturing operations are carried out in the same manner as the second fracturing operation. After the operation is completed, once the pressure in the well has diffused and balanced, the first K344 expandable packer 3 and the second K344 expandable packer 11 will automatically release.

[0030] Example 8: As attached Figure 1-5 As shown, taking the Niudongping xx well in the Tuha Oilfield as an example, the casing is slightly deformed. A double-layer pressure-splitting fracturing string is designed. The string structure from top to bottom is: φ101.6mm micro-coupling tubing + φ88.9mm micro-coupling tubing + φ105mm safety release connector + SLM-106 sand-control hydraulic anchor + K344-106 expansion packer + φ105mm short-time throttling sliding sleeve sandblaster + φ88.9mm micro-coupling tubing + SLM-106 sand-control hydraulic anchor + K344-106 expansion packer + φ105mm connector + φ100mm short-time throttling end sandblaster.

[0031] Lower the fracturing string to the design position, verify the data, and ensure that the packer is properly positioned to seal the fracturing layer that needs to be modified; align the short-time throttling sliding sleeve sandblaster and the short-time throttling end sandblaster with the layer.

[0032] Begin the first phase of construction: First, quickly increase the displacement to 1m 3 At a flow rate of / min, the high-speed flowing liquid passes through the φ22mm orifice throttling plate of the short-time throttling end blaster, forming a throttling pressure of ≥1.3MPa, which assists in the expansion and setting of the K344 fracturing packer cartridge. Then, carbon dioxide is pumped in according to the design, with an injection rate of 0.9-1.2m³. 3 / min.

[0033] After the pre-carbon dioxide injection is completed, fracturing operations begin, increasing the injection rate to 6-8m³. 3 The flow rate was increased to 10⁻¹² m³ / min, and a proppant slug flow with a 3% sand concentration was added to the fracturing fluid. The φ22mm orifice throttling plate of the short-time throttling end sandblaster was then ground away with the high-speed flowing sand-laden fluid until it was completely worn away, thus enlarging the sandblasting orifice. The flow rate was further increased to 10⁻¹² m³ / min. 3 Fracturing is completed in / min.

[0034] After fracturing the first layer, a steel ball of the corresponding size is inserted into the tubing to open the sliding sleeve valve core of the second-stage short-time throttling sandblaster, exposing the sandblasting orifice. Under the hydraulic pressure of the fluid, the sliding sleeve valve core passes through the packer and the hydraulic anchor center pipe to reach the receiver, where it cooperates to form a seal, blocking the lower fracturing string.

[0035] Begin the second phase of construction: First, quickly increase the displacement to 1m 3 At a flow rate of / min, the high-speed flowing liquid passes through the φ18mm orifice throttling plates on both sides of the short-time throttling sleeve sandblaster, forming a throttling pressure of ≥1.2MPa, which assists in the expansion and setting of the K344 fracturing packer's rubber sleeve. Then, carbon dioxide is pumped in according to the design, with an injection rate of 0.9-1.2m³. 3 / min.

[0036] After the pre-carbon dioxide injection is completed, fracturing operations begin, increasing the injection rate to 6-8m³. 3 The flow rate was increased to 10-12 m³ / min, and a proppant slug flow with a 3% sand concentration was added to the fracturing fluid. The φ22mm orifice of the short-time throttling end sandblaster was then ground away with the high-speed flowing sand-laden fluid until the entire 30mm*120mm long slot-shaped sandblasting nozzle of the sliding sleeve sandblaster was fully exposed. The flow rate was then further increased to 10-12 m³ / min. 3 Fracturing operation completed in / min.

[0037] Niu Dongping's xx well has two layers of pressure distribution. Before fracturing each section, 200t of carbon dioxide is pumped in, with an injection displacement of 1m³. 3 / min; 87m of proppant was added in the first stage of fracturing operation. 3 The injection displacement is 11.3m³. 3 / min; 106m of proppant was added in the second stage. 3 The injection displacement is 11.8m³. 3 / min.

[0038] The aforementioned fine fracturing string and construction method for horizontal wells that meet the requirements for carbon dioxide injection enables the use of a K344 fracturing packer as the core design fracturing string in wells with slight casing changes, to complete small-volume carbon dioxide injection followed by large-volume fracturing operations.

[0039] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A horizontal wellhead fracturing string for carbon dioxide fracturing, characterized in that... The system includes a fracturing tubing, a first sand-control hydraulic anchor, a first K344 expansion packer, and a short-time throttling end sandblaster. The first sand-control hydraulic anchor and the first K344 expansion packer are installed on the fracturing tubing from left to right. The short-time throttling end sandblaster is installed at the end of the fracturing tubing. The short-time throttling end sandblaster includes a housing, a throttling plate, and a pressure cap. The right inner side of the housing has a mounting groove with an opening to the right. The throttling plate is located in the mounting groove and is U-shaped with an opening to the left. The throttling plate is thick on the outside and thin in the middle. The thin part in the middle of the throttling plate can be eroded. The middle of the throttling plate has a first sandblasting port that runs through it from left to right. The left side of the pressure cap is threaded to the inner side of the upper housing to tighten the outside of the throttling plate.

2. A multi-layer fracturing string for horizontal wells using the carbon dioxide fracturing string described in claim 1, characterized in that... The system includes a horizontal wellhead fracturing string for carbon dioxide fracturing, a connector, a safety release joint, and at least one intermediate fracturing string. The intermediate fracturing string includes a second sand-control hydraulic anchor, a second K344 expansion packer, and a short-time throttling sleeve sprayer. From left to right, the left side of the fracturing tubing is equipped with the second sand-control hydraulic anchor and the second K344 expansion packer. A short-time throttling sleeve sprayer is installed on the fracturing tubing between the second K344 expansion packer and the first sand-control hydraulic anchor. The short-time throttling sleeve sprayer includes an upper shell, a lower shell, a throttling tube, and a sleeve valve core. The upper and lower shells are connected by a retaining screw. Two inner and outer sleeves are evenly distributed around the circumference of the lower shell. The elongated groove runs through the upper and lower housings. A throttling tube is installed between the upper and lower housings. The throttling tube is thicker on the left and thinner on the right. The thinner part on the right can be eroded. The right side of the throttling tube can cover the elongated groove. A second sandblasting port that runs through the inside and outside is provided in the middle of the throttling tube. The left end of the sliding sleeve valve core is located inside the upper housing, and the right end of the sliding sleeve valve core is located inside the lower housing and below the elongated groove. The right side of the sliding sleeve valve core is connected to the lower housing by a shear pin. A receiver is installed on the fracturing tubing on the right side of the first K344 expansion packer. The receiver is a short section with stepped holes on the inside. The receiver can block the sliding sleeve valve core and form a seal. A safety release connector is provided on the fracturing tubing on the left side of the middle fracturing string located at the far left.

3. The multi-layer fracturing string according to claim 2, characterized in that... The outer diameter of the sliding sleeve valve core is smaller on the left and larger on the right.

4. The multi-layer fracturing string according to claim 2 or 3, characterized in that... The short-time throttling sliding sleeve sandblaster also includes sealing rings. A sealing ring is provided between the upper housing and the sliding sleeve valve core, and a sealing ring is provided between the lower housing and the sliding sleeve valve core.

5. The multi-layer fracturing tubing string according to claim 4, characterized in that... The sealing sleeves of the first K344 expansion packer and the second K344 expansion packer, the rubber seals of the anchor teeth of the first and second sand-proof hydraulic anchors, the safety release joint, and the sealing rings of the short-time throttling sleeve sandblaster are all made of modified rubber materials, mainly hydrogenated nitrile rubber.

6. The multi-layer fracturing string according to claim 2, 3, or 5, characterized in that... The first and second K344 expansion packers are identical in size, being either K344-108 or K344-106 packers. The K344-108 packer has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the K344-106 packer has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both packers are heat-resistant up to 150℃ and have an internal pressure resistance of 70MPa. The first and second sand-control hydraulic anchors are identical in size, being either SLM-108 or SLM-106 hydraulic anchors. The SLM-108 hydraulic anchor has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the SLM-106 hydraulic anchor has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both hydraulic anchors are heat-resistant up to 150℃ and have an internal pressure resistance of 70MPa.

7. The multi-layer fracturing string according to claim 4, characterized in that... The first and second K344 expansion packers are identical in size, being either K344-108 or K344-106 packers. The K344-108 packer has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the K344-106 packer has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both packers are heat-resistant up to 150℃ and have an internal pressure resistance of 70MPa. The first and second sand-control hydraulic anchors are identical in size, being either SLM-108 or SLM-106 hydraulic anchors. The SLM-108 hydraulic anchor has a maximum outer diameter of φ108mm and an inner diameter of φ52mm, while the SLM-106 hydraulic anchor has a maximum outer diameter of φ106mm and an inner diameter of φ50mm. Both hydraulic anchors are heat-resistant up to 150℃ and have an internal pressure resistance of 70MPa.

8. A construction method using a multi-layer fracturing tubing string as described in any one of claims 2 to 7, characterized in that... Follow these steps: First, lower the fracturing tubing into the wellbore to the predetermined position, ensuring that the setting position is appropriate and can seal the formation to be modified. Then, align the short-time throttling end sandblaster and the short-time throttling sliding sleeve sandblaster with the target formation to be modified. Construction begins at the end location: Carbon dioxide is pumped in, rapidly increasing the discharge rate to 1m. 3 At a speed of / min, the high-speed flowing liquid passes through the first blasting orifice of the short-time throttling end blaster, forming a throttling pressure of ≥1.3MPa, which assists in the expansion and setting of the first K344 expansion packer sleeve. Then, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling vane of the short-time throttling end sandblaster; After the pre-carbon dioxide injection was completed, large-scale fracturing operations began with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3 At a flow rate of 10 m³ / min, proppant with a sand concentration of 3% is added to the fracturing fluid to create a slug flow. The high-speed flowing sand-laden fluid then passes through the first nozzle of the short-time throttling end-jet jet, which has a diameter of φ22mm. After the throttling plate is eroded and worn away, the first nozzle of the short-time throttling end-jet jet is enlarged to φ50mm, further increasing the fracturing pump injection rate to 10 m³ / min. 3 / min-12m 3 / min, complete the fracturing operation at the end position; The second fracturing operation is carried out by dropping a steel ball of the corresponding size into the tubing. The steel ball falls into the sliding valve core of the short-time throttling sliding sleeve sandblaster and is pressurized. The shear pin is sheared off, and the sliding valve core moves to the right, exposing the second sandblasting port. Under the hydraulic push of the fluid, the sliding valve core passes through the first anti-sand hydraulic anchor and the first K344 expansion packer to reach the receiver, where it cooperates to form a seal and block the lower fracturing string. Start pumping carbon dioxide, quickly increasing the discharge rate to 1m³. 3 At a flow rate of / min, high-speed flowing liquid passes through the second blasting orifices on both sides of the short-time throttling sliding sleeve blaster. These second orifices have a diameter of φ18mm, creating a throttling pressure ≥1.2MPa. This pressure serves as the starting pressure for the first K344 expansion packer, assisting in the expansion and setting of the packer's rubber sleeve. Subsequently, carbon dioxide is pumped in according to the design, with an injection displacement of 0.5m³. 3 / min-2m 3 / min, this flow rate and throttling pressure will not damage the throttling tube of the short-time throttling sliding sleeve sandblaster; After the second stage of pre-carbon dioxide injection is completed, large-scale fracturing operations begin with the injection of fracturing fluid at a displacement of 6m³. 3 / min-8m 3 At a flow rate of / min, proppant with a sand concentration of 3% is added to the fracturing fluid in a slug flow. The high-speed flowing sand-bearing fluid then passes through the second spray nozzles on the throttling tubes on both sides of the short-time throttling sleeve sprayer. These second spray nozzles, with a diameter of φ18mm, erode and wear down the throttling tubes, eventually expanding into long slot-shaped holes of 30mm*120mm, further increasing the fracturing pump injection rate to 10m³ / min. 3 / min-12m 3 / min, complete the second stage of fracturing operation; The subsequent fracturing operations are carried out in the same manner as the second fracturing operation. After the operation is completed, once the pressure in the well has diffused and balanced, the first K344 expansion packer and the second K344 expansion packer will automatically release.

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