Perforating method for promoting balanced injection of fracturing fluid of unconventional oil and gas horizontal well

Abstract

The invention discloses a perforation method for promoting balanced injection of fracturing fluid of an unconventional oil and gas horizontal well. The perforation method comprises the following steps: 1) determining the single-hole sand inlet amount at each phase in the circumferential direction of a shaft corresponding to a fracturing section of the horizontal well under the action of gravity; 2) determining the diameter and the number of eyelets required to be designed at each phase in the circumferential direction of each cluster of the fracturing section; (3) the average diameter and the arrangement number of perforations needed at the corresponding phases of the gravity high side and the gravity low side of the horizontal well are obtained; (4) the needed horizontal well self-orientation variable-aperture perforator is prepared; 5) designing a horizontal well self-orientation variable aperture perforator corresponding to each fracturing section in the working range of the horizontal well; (6) bridge plug setting and multi-cluster perforation tool string installation and operation are conducted; and (7) bridge plug setting, multi-cluster perforation and sand fracturing operations of all fracturing sections of the horizontal well are completed in sequence. The method belongs to the technical field of perforation well completion, and can ensure that the sand inlet amount of each phase perforation hole in the circumferential direction is consistent within the set time length.

Description

Technical Field

[0001] This invention belongs to the field of perforation completion technology and relates to a perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells. Background Technology

[0002] Horizontal well segmented multi-stage proppant fracturing technology is a key technology for achieving large-scale, efficient development of unconventional oil and gas resources with low porosity and permeability, such as shale and tight oil and gas. Typically, after setting segmented bridge plugs and completing multiple perforations at the target formation, fracturing fluid with predetermined proppant properties and proportions is pumped into the wellbore at a certain flow rate for this segment's proppant fracturing operation. However, when the perforation size, number of perforations, and formation fluid absorption capacity are basically consistent across all phases of the horizontal wellbore, the fracturing fluid flowing in the wellbore tends to flow towards the perforations near the lower gravity side due to its own gravity. This results in significant differences in the amount of proppant injected into the perforations across different phases of the wellbore after each fracturing stage. This prevents uniform fracturing and stimulation of the reservoir around the wellbore, hindering full three-dimensional utilization and ultimately affecting fracturing effectiveness and oil and gas production. Summary of the Invention

[0003] The purpose of this invention is to provide a perforation method that promotes balanced injection of fracturing fluid in unconventional oil and gas horizontal wells. This method solves the problems in the prior art where the amount of sand injected into the perforations of different phases around the wellbore varies greatly due to the influence of the fracturing fluid's own gravity, resulting in poor uniformity of reservoir stimulation around the wellbore and unsatisfactory fracturing effect and oil and gas production in horizontal wells.

[0004] The technical solution adopted in this invention is a perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells, implemented according to the following steps:

[0005] Step 1: Determine the single-hole sand infeed rate at each phase of the wellbore circumference corresponding to each cluster of a certain fracturing section in a certain horizontal well, taking gravity into account.

[0006] Step 2: Based on the single-hole sand inlet rate at each phase of the circumference of each cluster, with the aim of achieving a basically consistent total sand inlet rate at each perforation phase of any cluster of wellbore, determine the required perforation diameter and number at each phase of the circumference of each cluster in the fracturing section.

[0007] Step 3: Based on the diameter and number of perforations at each phase of each cluster in the fracturing section, obtain the average diameter and number of perforations required at the corresponding phases of the high gravity side and low gravity side of the horizontal well.

[0008] Step 4: Based on the results of Step 3, prepare the horizontal well self-directional variable diameter perforator required for each cluster of the fractured section of the horizontal well;

[0009] Step 5: Repeat steps 1-4 to design the horizontal well self-directional variable diameter perforator corresponding to each fracturing section within the working range of the horizontal well.

[0010] Step 6: Set the bridge plug and install and operate the multi-cluster perforation tool string in a certain fracturing section;

[0011] Step 7: Repeat step 6 to complete the bridge plug setting, multi-cluster perforation, and sand fracturing operations for all fracturing sections of the horizontal well in sequence.

[0012] The beneficial effects of this invention are that it considers the influence of gravity on the fracturing fluid (fracturing sand fluid) and adopts a custom-designed horizontal well self-directional variable diameter perforator to achieve a basically consistent total sand injection rate for each perforation cluster in each fracturing section across all phases of the wellbore circumference. Combining wellbore trajectory, wellbore inner diameter, formation pressure, and the designed sand fluid properties, sand fluid ratio, and pumping rate for each fracturing section, the average perforation diameter and number required for each perforation cluster in each fracturing section of the horizontal well at each phase of the wellbore circumference (0°, 60°, 120°, 180°, 240°, 300°) are simulated and analyzed. A custom design of the horizontal well self-directional variable diameter perforator required for each fracturing section is then implemented to complete multiple perforation clusters. This ensures that the total sand injection rate for each perforation cluster in each phase of the wellbore circumference remains consistent within a given time period, thereby promoting uniform reservoir stimulation around the wellbore and improving the fracturing effect and oil and gas production of unconventional oil and gas horizontal wells. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the horizontal well self-directional variable aperture perforator used in the method of the present invention;

[0014] Figure 2 This is a schematic diagram of the tool string composed of several clusters of horizontal well self-directional variable aperture perforators connected end to end according to the present invention.

[0015] Figure 3 This is a schematic diagram of the perforation phases of each perforation cluster in each fracturing section of a horizontal well corresponding to the circumferential direction of the wellbore during the implementation of the method of the present invention;

[0016] Figure 4 This is a schematic diagram illustrating the balanced injection of fracturing fluid after a cluster of perforations is completed by a self-directional variable-diameter perforator in a horizontal well during the implementation of the method of the present invention.

[0017] In the diagram, 1. Perforator; 1-1. Female connector; 1-2. Barrel; 1-3. Magazine rack; 1-3-1. Support frame; 1-3-2. Elastic contact support frame; 1-3-3. Counterweight; 1-4. Conventional deep-penetrating bullet; 1-5. Electronic firing module; 1-6. Male connector; 1-7. Electric detonator; 1-8. Detonating cord; 1-9. Large-hole deep-penetrating bullet; 1-10. Bearing.

[0018] 2. Setting tool; 3. Cable head; 4. Bridge plug; 5. Horizontal well casing; 5-1. Gravity low-side perforation hole; 5-2. Gravity high-side perforation hole; 6. Fracturing fluid. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] Reference Figure 1 The horizontal well self-directional variable aperture perforator (hereinafter referred to as perforator 1) used in the method of the present invention has the following structure: it includes a barrel 1-2 as the main body, and a female connector 1-1 and a male connector 1-6 are respectively threaded to both ends of the barrel 1-2. Each of the female connector 1-1 and the male connector 1-6 has a sealing ring on its contact surface with the barrel 1-2 to achieve sealing. A bearing 1-10 is respectively installed inside the axial hole of the female connector 1-1 and the male connector 1-6. A cartridge holder 1-3 is installed between -10 and the inner wall of the cartridge holder 1-3 is provided with multiple counterweights 1-3-3, multiple conventional deep-penetrating bullets 1-4 and multiple large-hole deep-penetrating bullets 1-9. Support brackets 1-3-1 and elastic contact support brackets 1-3-2 are fixed at both ends of the cartridge holder 1-3 respectively. Support brackets 1-3-1 and elastic contact support brackets 1-3-2 pass through bearings 1-10 inside the spindle holes of female connector 1-1 and male connector 1-6 respectively through their respective protruding shafts.

[0021] Large-aperture deep-penetration projectile 1-9 features a large perforation diameter and deep perforation depth, with predetermined design spacing L set at 0°, 60°, and 300° phases on the cross-section of the projectile holder 1-3. up The perforation diameter of conventional deep-penetrating projectiles 1-4 is smaller than that of large-hole deep-penetrating projectiles 1-9, while the perforation depth is basically the same as that of large-hole deep-penetrating projectiles 1-9. These perforations are set at predetermined design intervals L on the 120°, 180°, and 240° phases of the cross-section of the launcher 1-3. down All perforated ammunition uses detonating cords 1-8 connected in series. The end of the detonating cord 1-8 is connected to the electric detonator 1-7. The electric detonator 1-7 is fixed at the slotted end of the ammunition rack 1-3. The two pins of the electric detonator 1-7 are respectively connected to the detonation wire of the electronic firing module 1-5. The signal input line and signal output line of the electronic firing module 1-5 are respectively connected to the support frame 1-3-1 and the elastic contact support frame 1-3-2 of the ammunition rack. The grounding wire of the electronic firing module 1-5 is directly connected to the body of the ammunition rack 1-3.

[0022] The magazine 1-3 is made of thin-walled metal tubing. The support frame 1-3-1 and the elastic contact support frame 1-3-2 are respectively supported in a bearing 1-10. The two bearings 1-10 together serve as the automatic orientation and rotation fulcrum of the magazine 1-3, ensuring that the magazine 1-3, carrying all the firing rounds installed inside, can rotate freely in the barrel 1-2. On the inner surface of the magazine 1-3 at a 180° phase of the cross-section, several counterweights 1-3-3 are set at predetermined intervals. The eccentric gravity of the counterweights 1-3-3 ensures that the firing direction of all the firing rounds on the magazine 1-3 always faces the design phase.

[0023] Electronic firing modules 1-5, conventional deep-penetrating projectiles 1-4, and large-hole deep-penetrating projectiles 1-9 all adopt existing technologies, and the corresponding models are determined according to the needs of the site.

[0024] The perforation method of the present invention for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells is implemented according to the following steps:

[0025] Step 1: Determine the single-hole sand infeed rate at each phase of the wellbore circumference for each cluster in a certain fracturing section of a horizontal well, considering the effect of gravity.

[0026] Based on the wellbore trajectory, wellbore inner diameter, and formation pressure coefficient of a certain fractured section of an unconventional horizontal oil and gas well, the sand-fluid properties, sand-fluid volume ratio, average pumping rate, and designed basic perforation diameter of the fracturing fluid designed for this fractured section are simulated and analyzed (using existing fluid dynamics simulation software, which is publicly available and will not be detailed further) to determine the single-hole sand injection rate Q under gravity at each phase of the wellbore circumference at 0°, 60°, 120°, 180°, 240°, and 300° for each cluster of fracturing fluids in this fractured section of the horizontal well. g1 Q g2 Q g3 Q g4 Q g5 Q g6 ,See Figure 3 As shown;

[0027] Step 2: Determine the required orifice diameter and number for each circumferential phase of each cluster in the fracturing section.

[0028] Based on the single-hole sand inflow Q at each phase of the circumferential 0°, 60°, 120°, 180°, 240°, and 300° of each cluster in this fracturing section... g1 Q g2 Q g3 Q g4 Q g5 Q g6Further simulation analysis (using existing fluid dynamics simulation software) revealed the required orifice diameters d1, d2, d3, d4, d5, d6 and quantities N1, N2, N3, N4, N5, N6 at each circumferential phase (0°, 60°, 120°, 180°, 240°, 300°) for each cluster in the fracturing section. This ensures that, under a given pumping duration and pumping rate, the total sand injection volume into the corresponding perforations at each circumferential phase (0°, 60°, 120°, 180°, 240°, 300°) of each cluster in the fracturing section remains essentially consistent. (See attached image.) Figure 3 As shown;

[0029] Step 3: Based on the diameter and number of perforations at each phase of each cluster in the fracturing section, obtain the required average diameter and number of perforations at the corresponding phases of the high gravity side and low gravity side of the horizontal well.

[0030] Based on the perforation diameters d1, d2, d3, d4, d5, d6 and the quantities N1, N2, N3, N4, N5, N6 at each phase (0°, 60°, 120°, 180°, 240°, 300°) of each cluster in the fracturing section, the average perforation diameter required at phases 0°, 60°, and 300° corresponding to the gravity high edge of the horizontal well is given. Arrangement quantity And the average diameter of the perforation holes required at phases of 120°, 180°, and 240° corresponding to the lower gravity side of the horizontal well. Arrangement quantity This ensures that, under a given pumping duration and pumping rate, the total amount of sand injected into the perforations at phases 0°, 60°, and 300° corresponding to the high gravity side of each cluster in the fracturing section is essentially the same as the total amount of sand injected at phases 120°, 180°, and 240° corresponding to the low gravity side. (See...) Figure 3 , Figure 4 As shown;

[0031] Step 4: Based on the results of Step 3, prepare the horizontal well self-directional variable diameter perforators required for each cluster of the fracturing section.

[0032] Based on the results of step 3, select the appropriate perforation diameter d. up Number of installations N up Large-aperture deep-penetrating projectiles 1-9 have corresponding perforation diameters d. down Number of installations N down Conventional deep-penetrating perforating projectiles 1-4 were used, and the required horizontal well self-directional variable aperture perforator (perforator 1) structure was customized and fabricated.

[0033] Step 5: Repeat steps 1-4 to design the horizontal well self-directional variable diameter perforator (perforator 1) for each fracturing section within the working range of the horizontal well.

[0034] Step 6: Install and operate the bridge plug setting and multi-cluster perforation tool string in a specific fracturing section.

[0035] Connect the first and last ends of several clusters of horizontal well self-directional variable diameter perforators required for adjacent fracturing sections to assemble a set of horizontal well self-directional variable diameter (multi-cluster) perforator strings. Connect cable heads 3, setting tools 2, and bridge plugs 4 to the first and last ends of the entire perforator string, respectively. This forms the bridge plug setting and multi-cluster perforation tool string required for a specific fracturing section, referred to as the tool string. See [link to documentation]. Figure 2 As shown;

[0036] First, set the bridge plug for this section, then perform multi-perforation operations: Deliver the tool string to the horizontal well casing 5 at the target formation. Gravity low-side perforation 5-1 is located at the 180° circumferential phase; gravity high-side perforation 5-2 is located at the 0° circumferential phase. Next, according to the designed sand properties, sand ratio, and pumping rate for this fracturing section, implement sand fracturing operations to promote balanced injection of fracturing fluid 6 into each circumferential perforation cluster in this fracturing section. (See...) Figure 4 As shown;

[0037] Step 7: Repeat the operation in Step 6 to complete the bridge plug setting, multi-cluster perforation, and sand fracturing operations for all fracturing sections of the horizontal well in sequence.

[0038] Example 1

[0039] According to the unconventional horizontal oil and gas well fracturing fluid equalization injection perforation method of the present invention, the aforementioned horizontal well self-directional variable aperture perforator structure is adopted, and the method is implemented according to the following steps:

[0040] Step 1: Based on the wellbore trajectory of a fractured section in a 5-1 / 2" shale gas horizontal well in a certain area (vertical depth 3878m, fractured section length 65m, average well inclination angle 90°), wellbore inner diameter 114.3mm, formation pressure coefficient 2.05, determine the sand-fluid properties of the fracturing fluid designed for this fractured section (the fluid mainly consists of slickwater and sand, primarily 100-mesh silt and 40 / 70-mesh ceramsite, with an average fluid viscosity of 6 mm). 2 / s, average bulk density of mixed sand 1.6g / cm³ 3 The sand-liquid volume ratio was 7% and the average pumping discharge rate was 15m³. 3 / min, and the designed basic perforation diameter of 10mm, the simulation analysis determined the single-hole sand infeed rate Q of each cluster in this horizontal well's fracturing section at various phases along the wellbore circumference (0°, 60°, 120°, 180°, 240°, 300°) under the influence of gravity. g1 Q g2 Q g3 Q g4 Q g5 Q g6,See Figure 3 As shown;

[0041] Step 2: Based on the analysis, determine the single-hole sand inflow rate Q at each phase of the fracturing section at 0°, 60°, 120°, 180°, 240°, and 300° circumferentially. g1 Q g2 Q g3 Q g4 Q g5 Q g6 Further simulation analysis determined the required orifice diameters d1, d2, d3, d4, d5, d6 and quantities N1, N2, N3, N4, N5, N6 at each circumferential phase (0°, 60°, 120°, 180°, 240°, 300°) of each cluster in the fracturing section. This ensured that, under a given pumping duration and pumping rate, the total sand injection volume into the corresponding perforated orifices at each circumferential phase (0°, 60°, 120°, 180°, 240°, 300°) of each cluster in the fracturing section remained essentially consistent. (See...) Figure 3 As shown;

[0042] Step 3: Based on the perforation diameters d1, d2, d3, d4, d5, d6 and the quantities N1, N2, N3, N4, N5, N6 at each phase of the circumferential 0°, 60°, 120°, 180°, 240°, and 300° of each cluster in the fracturing section obtained from the analysis, determine the average perforation diameter required at the corresponding phases 0°, 60°, and 300° of the gravity high edge of the horizontal well. Arrangement quantity And the average diameter of the perforation holes required at phases of 120°, 180°, and 240° corresponding to the lower gravity side of the horizontal well. Arrangement quantity This ensures that, under a given pumping duration and pumping rate, the amount of sand injected into the perforations at phases 0°, 60°, and 300° corresponding to the high gravity side of each cluster in the fracturing section is essentially the same as the amount injected at phases 120°, 180°, and 240° corresponding to the low gravity side. (See...) Figure 3 , Figure 4 As shown;

[0043] Step 4: Based on the results of Step 3, select the appropriate perforation diameter d. up Number of installations N up Large-aperture deep-penetrating projectiles 1-9 have corresponding perforation diameters d. down Number of installations N down The conventional deep-penetrating perforator 1-4, and the customized design of the horizontal well self-directional variable diameter perforator required for each cluster of the fracturing section;

[0044] Step 5: Repeat steps 1-4 to design the horizontal well self-directional variable diameter perforator required for all fracturing sections of the horizontal well.

[0045] Step 6: Perform bridge plug setting and installation of the multi-cluster perforation tool string.

[0046] Connect the first and last clusters of horizontal well self-directional variable-diameter perforators required for a certain fracturing section to form a multi-cluster perforator string. Connect cable heads 3, setting tools 2, and bridge plugs 4 to the first and last ends of the entire perforator string, respectively. This completes the bridge plug setting and multi-cluster perforation tool string required for that fracturing section. See [link to documentation]. Figure 2 As shown;

[0047] First, set the bridge plug for this section, then proceed with multi-perforation operations: Deliver the tool string to the horizontal well casing 5 at the target formation. Next, implement sand injection fracturing operations according to the designed sand properties, sand ratio, and pumping rate for this fracturing section. This will promote the balanced injection of fracturing fluid 6 into each circumferential perforation hole of this fracturing section. (See...) Figure 3 , Figure 4 As shown;

[0048] Step 7: Repeat the operation in Step 6 to complete the bridge plug setting, multi-cluster perforation, and sand fracturing operations for all fracturing sections of the horizontal well in sequence.

[0049] Example 2

[0050] Following the steps described in Example 1 of this invention, a perforation design to promote balanced fracturing fluid injection was implemented for a 5-1 / 2" shale gas horizontal well in a certain location. This horizontal well has a vertical depth of 3878m, an average fracturing section length of 65m, a designed number of fracturing sections of 20, an average well inclination angle of 90°, a wellbore inner diameter of 114.3mm, and a formation pressure coefficient of 2.05. The fluid used in this horizontal well mainly consists of slickwater and sand, primarily 100-mesh silt and 40 / 70-mesh ceramsite, with an average fluid viscosity of 6mm. 2 / s, average bulk density of mixed sand 1.6g / cm³ 3 The sand-liquid volume ratio is 7%, and the designed average pumping discharge rate is 15m³. 3The design perforation diameter is 10 mm. Based on the above well engineering parameters, the method of this invention was used to determine that the average perforation diameter required for each cluster of gravity high side at phases 0°, 60°, and 300° in sections 10-20 of the well is 11.2 mm, with a quantity of 6 holes. For horizontal wells, the average perforation diameter required for each cluster of gravity low side at phases 120°, 180°, and 240° is 9.6 mm, with a quantity of 4 holes. Sections 1-9 of the well use the original perforation design method, i.e., the average perforation diameter required for each cluster of circumferential phases 0°, 60°, 120°, 180°, 240°, and 300° is 11.7 mm, with a total quantity of 10 holes. Simulation calculations using professional fracturing stimulation volume software confirmed that after using the perforation method of this invention in sections 10-20 of the well, the fracturing fluid injection into each cluster of circumferential perforations was basically balanced, and the single-section stimulation volume increased by more than 20% compared with the original method, thus promoting the fracturing stimulation and three-dimensional utilization effect of the reservoir in the well.

[0051] Example 3

[0052] Following the steps described in Example 1 of this invention, a perforation design to promote balanced injection of fracturing fluid was implemented for a 5" shale gas horizontal well in a certain location. This horizontal well has a vertical depth of 3980m, an average fracturing section length of 65m, a designed number of fracturing sections of 20, an average well inclination angle of 90°, a wellbore inner diameter of 107mm, and a formation pressure coefficient of 2.05. The fluid used in this horizontal well mainly consists of slickwater and sand, primarily 100-mesh silt and 40 / 70-mesh ceramsite, with an average fluid viscosity of 6.11 mm. 2 / s, average bulk density of mixed sand 1.62g / cm³ 3 The sand-liquid volume ratio is 7%, and the designed average pumping discharge rate is 15m³. 3 The design perforation diameter is 10 mm. Based on the above well engineering parameters, the method of this invention was used to determine that the average perforation diameter required for each cluster of gravity high side at phases 0°, 60°, and 300° in sections 10-20 of the well is 11.2 mm, with a quantity of 6 holes. For horizontal wells, the average perforation diameter required for each cluster of gravity low side at phases 120°, 180°, and 240° is 9.6 mm, with a quantity of 4 holes. Sections 1-9 of the well use the original perforation design method, i.e., the average perforation diameter required for each cluster of circumferential phases 0°, 60°, 120°, 180°, 240°, and 300° is 11.7 mm, with a total quantity of 10 holes. Simulation calculations using professional fracturing stimulation volume software confirmed that after using the perforation method of this invention in sections 10-20 of the well, the fracturing fluid injection into each cluster of circumferential perforations was basically balanced, and the single-section stimulation volume increased by more than 20% compared with the original method, thus promoting the fracturing stimulation and three-dimensional utilization effect of the reservoir in the well.

Claims

1. A perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells, characterized in that, Follow these steps to implement the procedure: Step 1: Determine the single-hole sand injection rate at each phase of the wellbore corresponding to a certain cluster in a certain fracturing section of a horizontal well, considering the effect of gravity. Step 2: Based on the single-hole sand injection rate at each phase of the wellbore for each cluster, determine the required perforation diameter and number at each phase of the wellbore for each cluster in the fracturing section. Step 3: Based on the perforation diameter and number at each phase of the fracturing section, obtain the average perforation diameter and the required number of perforations at the phases corresponding to the high and low gravity sides of the horizontal well. Step 4: Based on the results of Step 3, prepare the horizontal well self-directional variable-diameter perforator required for each cluster in the fracturing section of the horizontal well. Step 5: Repeat Steps 1-4 to design the horizontal well self-directional variable-diameter perforator corresponding to each fracturing section within the working range of the horizontal well. Step 6: Perform bridge plug setting and multi-cluster perforation tool string installation and operation for a certain fracturing section. Step 7: Repeat Step 6 to sequentially complete bridge plug setting, multi-cluster perforation, and sand fracturing operations for all fracturing sections of the horizontal well.

2. The perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells according to claim 1, characterized in that, In step 1, the specific process is as follows: Based on the wellbore trajectory, wellbore inner diameter, and formation pressure coefficient of a certain fractured section of an unconventional horizontal oil and gas well, the sand-fluid properties, sand-fluid volume ratio, average pumping rate, and designed basic perforation diameter of the fracturing fluid designed for this fractured section are simulated and analyzed to determine the single-hole sand injection rate Q under gravity at various phases (0°, 60°, 120°, 180°, 240°, and 300°) of the wellbore circumference in this fractured section of the horizontal well. g1 Q g2 Q g3 Q g4 Q g5 Q g6 .

3. The perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells according to claim 1, characterized in that, Step 2, the specific process is as follows: Based on the single-hole sand inflow Q at each phase of the circumferential 0°, 60°, 120°, 180°, 240°, and 300° of each cluster in this fracturing section... g1 Q g2 Q g3 Q g4 Q g5 Q g6 Further simulation analysis determined the required orifice diameters d1, d2, d3, d4, d5, d6 and quantities N1, N2, N3, N4, N5, N6 at each phase of the circumferential 0°, 60°, 120°, 180°, 240°, and 300° of each cluster in the fracturing section. This ensured that, under a given pumping duration and pumping rate, the total amount of sand injected into the corresponding perforation orifices at each phase of the circumferential 0°, 60°, 120°, 180°, 240°, and 300° of each cluster in the fracturing section remained consistent.

4. The perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells according to claim 1, characterized in that, Step 3, the specific process is as follows: Based on the perforation diameters d1, d2, d3, d4, d5, d6 and the quantities N1, N2, N3, N4, N5, N6 at each phase (0°, 60°, 120°, 180°, 240°, 300°) of each cluster in the fracturing section, the average perforation diameter required at phases 0°, 60°, and 300° corresponding to the gravity high edge of the horizontal well is given. Arrangement quantity And the average diameter of the perforation holes required at phases of 120°, 180°, and 240° corresponding to the lower gravity side of the horizontal well. Arrangement quantity This ensures that, under a given pumping time and pumping rate, the amount of sand injected into the perforation holes at phases 0°, 60°, and 300° corresponding to the high gravity side of each cluster in the fracturing section is consistent with the amount injected at phases 120°, 180°, and 240° corresponding to the low gravity side.

5. The perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells according to claim 1, characterized in that, Step 4, the specific process is as follows: Select one with the appropriate perforation diameter d up Number of installations N up Large-aperture deep-penetrating projectiles with corresponding perforation diameter d down Number of installations N down The conventional deep-penetrating perforator was developed, and the required horizontal well self-directional variable aperture perforator structure was prepared.

6. The perforation method for promoting balanced injection of fracturing fluid in unconventional oil and gas horizontal wells according to claim 1, characterized in that, Step 6 involves the following steps: Connect the first and last of several clusters of horizontal well self-directional variable diameter perforators required for adjacent fracturing sections to assemble a set of horizontal well self-directional variable diameter perforators string. Connect cable heads, setting tools, and bridge plugs to the first and last ends of the string of perforators respectively to form the bridge plug setting and multi-cluster perforation tool string required for this fracturing section, referred to as the tool string. The tool string is delivered to the horizontal well casing of the target formation. Then, sand fracturing operation is carried out according to the sand properties, sand ratio and pumping rate designed for this fracturing section, thereby promoting the balanced injection of fracturing fluid into each perforation hole in the circumferential direction of this fracturing section.

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