Horizontal well reversed-sequence refracturing method and application

Abstract

The invention discloses a horizontal well reversed-sequence refracturing method and application, and belongs to the technical field of compact conglomerate oil reservoir transformation of petroleum engineering. According to the method, the communication condition of the old joint and the stratum is judged through trial extrusion, and sand plugging treatment is conducted on the old joint of the communicated stratum; the well is washed until the fracturing operation requirement is met, hydraulic sand blasting perforation operation is conducted, and oil sleeve annulus sand fracturing is conducted to form a new fracturing crack; and the oil sleeve annulus is cleaned, the relation between the sand discharging amount and the liquid amount is calculated, and a basis is provided for follow-up construction till fracturing operation of all workshop sections is completed. According to the method, the plugging effect is judged through peak-type lifting of construction curve pressure after trial extrusion, plugging is conducted in combination with an artificial sand plugging technology of fine sand and liquid amount control and multiple times of plugging, the plugging rate of the old seam of the horizontal well is increased, a new seam is manufactured through a hydraulic sand blasting perforation reversed-sequence staged fracturing technology, real-time and accurate transformation is achieved, an untransformed section of a remaining oil enrichment area is activated, and the plugging efficiency of the old seam of the horizontal well is improved. And the mining period is prolonged, and the single well EUR is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reservoir reconstruction of dense conglomerate reservoirs in petroleum engineering, and particularly relates to a horizontal well reverse sequence repeated fracturing method and application. BACKGROUND

[0002] Low-permeability oilfields refer to oilfields with low reservoir rock permeability, which leads to difficult fluid (such as oil and natural gas) flow therein and low natural productivity. In low-permeability oilfields, the complex pore structure, small porosity, small throat and poor connectivity of the reservoir rock greatly limit the fluid flow therein. With the continuous progress of geological exploration technology and the continuous deepening of oil and gas resource development strategies, the proportion of low-permeability reservoirs in the total proven reserves is increasing, and they also occupy an increasingly important position in the reserves that have been put into production.

[0003] In the development practice of low-permeability oilfields, due to the poor reservoir properties, the natural productivity of oil wells is generally low, which is difficult to directly meet the needs of industrial exploitation, and the oil flow with industrial exploitation value is formed after fracturing reconstruction. Secondly, the percolation law of low-permeability oilfields deviates from Darcy's law significantly, showing obvious nonlinear characteristics, that is, there is a starting pressure gradient. In addition, the natural energy of low-permeability oilfields is generally weak, resulting in a large production pressure difference in the production process and rapid production decline, and the primary recovery rate is relatively low. In the face of the complexity and challenge of low-permeability oilfield development, it is necessary to improve the natural productivity of oil wells in the development process according to the development characteristics of low-permeability oilfields, so as to have industrial exploitation value, and it is necessary to reconstruct through hydraulic fracturing and other stimulation measures.

[0004] At present, the dense conglomerate reservoirs in low-permeability oilfields are generally developed by horizontal well volume fracturing. For horizontal wells with large difference in mobilization between primary fracturing clusters and late failure of fracture conductivity, it is necessary to use a packer to effectively isolate the reconstructed section, so as to realize efficient mobilization of the unreconstructed section in the remaining oil enrichment area, so as to improve the single well ultimate recoverable reserves (EUR). However, the existing horizontal well reconstruction wellbore has high cost, and the temporary plugging repeated fracturing technology has the problem of poor reconstruction effectiveness. In order to solve these problems, an innovative method is needed to activate the unreconstructed section in the remaining oil enrichment area, so as to significantly improve the single well EUR. SUMMARY

[0005] To solve the above technical problems, the application provides a horizontal well reverse sequence repeated fracturing method and application. The application uses artificial sand plugging technology to plug the old fractures, provides a competitive advantage for new fracture reconstruction, and creates new fractures at the preset shooting position between the old fractures and the bottom seal through hydraulic sandblasting perforation fracturing, to realize real-time accurate reconstruction.

[0006] To achieve the above purpose, the application provides the following technical solutions: A method for reverse-sequence repeated fracturing of horizontal wells includes the following steps: S1: After the coiled tubing passes through the first old seam at the heel end, the packer is set; S2: Determine the communication between the old fracture and the formation by trial extrusion, and perform sand plugging treatment on the old fracture that has been connected to the formation until the old fracture is sealed; S3: Perform well washing until the fracturing operation requirements are met, then perform hydraulic jetting perforation, implement sand fracturing of the oil casing annulus to form new fracturing fractures, clean the oil casing annulus after fracturing is completed, and unseal the packer. S4: Repeat steps S1 to S3 sequentially for all old seams from the heel to the toe of the horizontal well.

[0007] Before proceeding with S1, the horizontal well needs to be treated to meet the requirements of subsequent operations, specifically: The production tubing of the horizontal well is pulled out, and the well to be fractured is circulated to the bottom of the artificial well. After the well is circulated and qualified, clean water is injected through the casing at a large volume to flush the well in reverse circulation until the well meets the requirements for subsequent operations.

[0008] After the coiled tubing in S1 passes through the first pre-slit at the heel end, the packer is set, specifically as follows: The coiled tubing tools are fixedly connected together to form a fracturing string, which is then lowered into the horizontal well. After passing through the first old fracture at the heel end, the coupling locator is used to position it at the formation pre-injection position, and the packer is set.

[0009] In S2, the connection between the old fracture and the formation is determined by trial extrusion, specifically as follows: Trial extrusion was conducted to determine the current communication status between the old fracture and the stratum by analyzing the trend of the construction curve, and the corresponding relationship between the discharge volume and pressure was determined.

[0010] In S2, old fractures in the connected strata are plugged with sand until the old fractures are sealed. Specifically: After the reagent is applied, if it is determined that the old fracture has connected to the formation, a sand plug is made to seal all fractures between the heel of the horizontal well and the packer. Then, by test extrusion, the effectiveness of sand plugging is judged. Based on the corresponding relationship between the required discharge volume and pressure, when the injection discharge volume is less than 0.5 cubic meters, the pump pressure rises to the upper limit of the pressure limit, which is judged as effective plugging; if it is not effective plugging, sand plugging treatment continues until it is judged as effective plugging.

[0011] In S3, well washing is carried out until the requirements for fracturing operations are met, specifically: Switch to the forward flushing process, inject fracturing fluid into the coiled tubing to perform forward flushing, observe the surface fluid and sand production, and when no sand returns, perform a flush of one annular volume.

[0012] Hydraulic sandblasting and perforation operations were carried out in S3, specifically as follows: The annulus of the casing and casing is either open or throttled open to establish circulation. Displacement fluid is injected into the continuous tubing. Through throttling via the nozzle, the high-pressure displacement fluid in the tubing is transformed into a high-speed jet that penetrates the casing and cement annulus, creating a channel between the reservoir and the wellbore, thus completing the perforation operation.

[0013] In S3, new hydraulic fractures are formed by annular fracturing with sand addition. Specifically: Fracturing is performed by injecting pre-flush fluid, proppant-carrying fluid, and displacement fluid into the annulus of the oil casing to open up the formation and form new fractures.

[0014] After fracturing is completed in S3, the annulus of the oil casing is cleaned, specifically as follows: After fracturing is completed, the coiled tubing pump is stopped, fracturing fluid is injected through the tubing, and the remaining sand is carried out through the annulus of the casing. The relationship between the amount of sand discharged and the amount of fluid is calculated to provide a basis for the fracturing of subsequent horizontal wells.

[0015] This invention also provides the application of the above-mentioned horizontal well reverse repeated fracturing method in tight conglomerate reservoirs.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method and application for reverse-sequence repeated fracturing of horizontal wells. This invention helps guide the repeated fracturing of old wells in the field, thereby improving the efficient utilization of untreated sections in remaining oil-rich areas and opening up new paths for the secondary development and even long-term stable and high-yield production of oilfields. This method employs a reverse-sequence repeated fracturing approach with coiled tubing and bottom seal. The sealing effect of treated fractures is judged by the "peak-like" pressure rise of the construction curve after trial extrusion. Combined with the artificial sand-plugging technique of "precise control of sand and fluid volume + multiple plugging," the sealing rate of old fractures in horizontal wells is improved. During field construction, the amount of sand and fluid added can be adjusted at any time to plug the old fractures, precisely controlling the sand and fluid volume, thus reducing costs from the source. New fractures are created using a reverse-sequence segmented fracturing process with coiled tubing and bottom seal dragged by hydraulic jet perforation. Hydraulic jet perforation operations can achieve precise perforation positioning, enabling real-time and accurate fracturing and providing a competitive advantage for new fracture fracturing. This method activates the unreformed sections of the remaining oil-rich zone, extends the production cycle, significantly improves the EUR of a single well, and provides a strong guarantee for the efficient development and sustainable development of the oilfield.

[0017] Furthermore, applying this method to tight conglomerate reservoirs can generate new fractures, connect reservoirs, increase reservoir stimulation volume, tap the potential of remaining oil and gas reservoirs in oilfields, improve single-well productivity, and further increase extraction efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below: Figure 1 This is a flowchart of the horizontal well reverse-sequence repeated fracturing method of the present invention; Figure 2 This is a schematic diagram of the horizontal well reverse-sequence repeated fracturing method of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" relationship.

[0023] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0024] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0025] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0026] Currently, there is an urgent need for research and breakthroughs in cyclic fracturing technology. It is necessary to explore and improve fracturing strategies from the perspectives of effectiveness and cost. Based on this, this invention proposes for the first time a coiled tubing bottom-sealed reverse-sequence segmented fracturing process. It utilizes artificially created sand plugging technology to seal old fractures. The sealing effect is judged by the "peak-like" pressure rise on the construction curve after trial extrusion. Combined with the technical means of "precise control of sand and fluid volume + multiple sealing," the sealing rate of old fractures in horizontal wells is improved, ensuring the stability and durability of the sealing effect. This provides a guarantee for subsequent fracturing of new fractures and achieving real-time and precise transformation. This invention helps guide the repeated fracturing of old wells in the field, thereby improving the efficient utilization of untreated sections in remaining oil-rich areas.

[0027] like Figure 2 As shown, in this invention, the end of the horizontal well closer to the vertical section is designated as the heel end (end A), and the end of the horizontal well farther from the diameter section is designated as the toe end (end B).

[0028] like Figure 1 and Figure 2 As shown, the present invention provides a method for reverse-sequence repeated fracturing of horizontal wells, comprising the following steps: S1: The horizontal well is treated to meet the requirements of subsequent operations; S2: After the coiled tubing passes through the first old seam at the heel end, the packer is set; S3: Determine the communication between the old fracture and the formation by trial extrusion, and perform sand plugging treatment on the old fracture that has been connected to the formation until the old fracture is sealed; S4: Perform well washing until the fracturing operation requirements are met, then perform hydraulic jetting perforation operation, and implement annular fracturing with sand to form new fracturing fractures; S5: After fracturing is completed, clean the annulus of the oil casing and calculate the relationship between the amount of sand discharged and the amount of fluid to provide a basis for fracturing of subsequent horizontal wells. After cleaning, unseal the packer. S6: Repeat steps S2 to S5 sequentially for all old fractures from the heel to the toe of the horizontal well until all fracturing operations are completed.

[0029] This invention, based on old well drilling, logging, and fracturing data, as well as post-fracturing production conditions, utilizes artificially created sand plugging technology to seal existing fractures. It employs a coiled tubing-with-bottom-seal-driven hydraulic jetting perforation reverse-sequence segmented fracturing process to provide a competitive advantage for fractures requiring fracturing, thus forming a horizontal well reverse-sequence repeated fracturing method. This method uses artificially created sand plugging technology to seal old fractures, providing a competitive advantage for the stimulation of new fractures. New fractures are created at pre-perforation positions set between the old fracture and the bottom seal through hydraulic jetting perforation fracturing, achieving real-time and precise fracturing.

[0030] The method of the present invention will be further explained below: Step S1 involves processing the horizontal well to meet the requirements of subsequent operations, specifically as follows: The production tubing of the horizontal well is pulled out, and the well to be fractured is circulated to the bottom of the artificial well. After the well is circulated and qualified, clean water is injected through the casing at a large volume to flush the well in reverse circulation until the well meets the requirements for subsequent operations.

[0031] It should be noted that well cleaning and well flushing are two important preliminary preparations. Well cleaning checks whether the wellbore is unobstructed and intact, removes debris from the well, inspects the condition of the casing, and ensures that the casing can withstand the high-pressure operation during fracturing. Reverse circulation well flushing achieves efficient cleaning, generates less back pressure on the formation, reduces formation damage, improves formation permeability and conductivity, and enhances fracturing effectiveness.

[0032] In step S2, after the coiled tubing passes through the first old seam at the heel end, the packer is set, specifically as follows: The coiled tubing tools are fixedly connected together to form a fracturing string and lowered into the well. After passing the first old fracture position at the heel end (near point A), the coupling locator is used to position it at the formation pre-injection position, and the packer is set.

[0033] In step S3, the communication between the old fracture and the formation is determined by trial extrusion, specifically as follows: Trial extrusion was conducted to determine the current communication status between the old fracture and the stratum by analyzing the trend of the construction curve, and to determine the correspondence between the injection volume and the pump pressure, providing a basis for subsequent trial extrusion operations.

[0034] It should be noted that when the pump pressure decreases or remains constant while the injection rate increases; or when the injection rate remains constant but the pump pressure increases for a period of time and then rapidly decreases, it indicates that the old fracture has connected with the formation. When the pump pressure increases with the increase in injection rate, it indicates that there is no connection with the formation.

[0035] Step S3 involves sand plugging of the old fractures in the already connected strata, specifically as follows: The amount of sand and fluid added is precisely controlled using coiled tubing to plug old fractures in already connected formations. If it is determined that the strata have been connected, a "small-scale + small displacement + under-displacement" construction mode is adopted to create sand plugs; All cracks between the heel of the horizontal well and the packer need to be sealed. Then, by test extrusion, the effectiveness of sand plugging is judged. Combining the corresponding relationship between the required discharge volume and pressure, when the injection discharge volume is less than 0.5 cubic meters, the pump pressure rises to the upper limit of the pressure limit, which is initially judged as effective plugging (adjusted according to the on-site construction situation); if it is not effective plugging, sand plugging treatment needs to be performed multiple times until it is judged to be effective plugging.

[0036] It should be noted that during the sand plugging process on existing fractures in already connected formations, a trial extrusion method is first used to understand the distribution of the fractures, the trend of pressure changes, and the formation's absorption capacity, providing operational guidance for subsequent artificial sand plugging. Based on the trial extrusion results, artificial sand plugging is then carried out. During the process, the existing fractures are monitored in real time. A "small-scale + small-volume + under-displacement" construction mode is used to precisely control the amount of sand and fluid added, allowing for adjustments to the amounts at any time. This effectively seals the modified fractures in the already connected formations, avoiding waste of fracturing fluid. The effectiveness of the sand plugging is then assessed through further trial extrusion until the sealing is confirmed to be effective, providing strong support for subsequent fracturing of new fractures.

[0037] In step S4, well washing is performed until the requirements for fracturing operations are met, specifically as follows: Switch to the forward flushing process, inject fracturing fluid into the coiled tubing to perform forward flushing, observe the surface fluid and sand production, and when no sand returns, perform a flush of one annular volume.

[0038] It should be noted that during the positive circulation well washing process, the surface fluid and sand production must be closely monitored to ensure that impurities in the well are effectively removed. When no sand returns, another flush of the annulus volume should be performed to further consolidate the well washing effect and ensure that the environment inside the well meets the requirements for fracturing operations.

[0039] Step S4 involves water jet blasting perforation, specifically as follows: The annulus of the casing and casing is either open or throttled open to establish circulation. Displacement fluid is injected into the continuous tubing. Through throttling via the nozzle, the high-pressure displacement fluid in the tubing is transformed into a high-speed jet that penetrates the casing and cement annulus, creating a channel between the reservoir and the wellbore, thus completing the perforation operation.

[0040] It should be noted that hydraulic jetting perforation can achieve precise perforation positioning, which can improve the efficiency of fracturing fluid injection and the range of fracture propagation. It can also improve formation permeability through jetting, laying the foundation for subsequent fracturing operations.

[0041] In step S4, annular fracturing with sand is performed to form new fracturing fractures, specifically as follows: Fracturing is performed by injecting pre-flush fluid, proppant-carrying fluid, and displacement fluid into the annulus of the oil casing to open up the formation and form new fractures.

[0042] It should be noted that in fracturing operations, precise control of the injection volume of pre-flush fluid, proppant-carrying fluid, and displacement fluid is crucial; precise control not only helps to form fractures of sufficient width and length, but also ensures that new fractures are evenly distributed and effectively expanded, significantly improving the effect of reservoir stimulation.

[0043] In step S5, after fracturing, the annulus of the oil casing is cleaned, and the relationship between the amount of sand discharged and the amount of fluid is calculated to provide a basis for subsequent horizontal well fracturing. Specifically: After fracturing is completed, the coiled tubing pump is stopped, fracturing fluid is injected through the tubing, and the remaining sand is carried out through the annulus of the casing. The relationship between the amount of sand discharged and the amount of fluid is calculated to provide a basis for the fracturing of subsequent horizontal wells.

[0044] It should be noted that backwashing the annulus ensures effective removal of impurities from the well, guaranteeing the effectiveness of subsequent well operations. Observing and calculating the relationship between the amount of sand discharged and the amount of fluid provides a basis for subsequent horizontal well fracturing, ensuring the efficiency of subsequent fracturing and reducing costs.

[0045] The horizontal well reverse-sequence repeated fracturing method proposed in this invention is applied to tight conglomerate oil reservoirs. This method uses artificial sand plugging technology—"precise control of sand and fluid volume + multiple plugging"—to plug old fractures, and then fracturing new fractures in the untreated section to activate the remaining oil-rich untreated section. This significantly increases the final recoverable reserves of a single well, reduces development costs, extends the production cycle, and greatly improves the recovery rate and economic benefits of oil and gas resources, providing a strong guarantee for the sustainable development of oil and gas fields.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A method for reverse-sequence repeated fracturing of horizontal wells, characterized in that, Includes the following steps: S1: After the coiled tubing passes through the first old seam at the heel end, the packer is set; S2: Determine the communication between the old fracture and the formation by trial extrusion, and perform sand plugging treatment on the old fracture that has been connected to the formation until the old fracture is sealed; S3: Perform well washing until the fracturing operation requirements are met, then perform hydraulic jetting perforation, implement sand fracturing of the oil casing annulus to form new fracturing fractures, clean the oil casing annulus after fracturing is completed, and unseal the packer. S4: Repeat steps S1 to S3 sequentially for all old seams from the heel to the toe of the horizontal well.

2. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, Before proceeding with S1, the horizontal well needs to be treated to meet the requirements of subsequent operations, specifically: The production tubing of the horizontal well is pulled out, and the well to be fractured is circulated to the bottom of the artificial well. After the well is circulated and qualified, clean water is injected through the casing at a large volume to flush the well in reverse circulation until the well meets the requirements for subsequent operations.

3. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, After the coiled tubing in S1 passes through the first pre-slit at the heel end, the packer is set, specifically as follows: The coiled tubing tools are fixedly connected together to form a fracturing string, which is then lowered into the horizontal well. After passing through the first old fracture at the heel end, the coupling locator is used to position it at the formation pre-injection position, and the packer is set.

4. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, In S2, the connection between the old fracture and the formation is determined by trial extrusion, specifically as follows: Trial extrusion was conducted to determine the current communication status between the old fracture and the stratum by analyzing the trend of the construction curve, and the corresponding relationship between the discharge volume and pressure was determined.

5. The method for reverse repeated fracturing of a horizontal well according to claim 4, characterized in that, In S2, old fractures in the connected strata are plugged with sand until the old fractures are sealed. Specifically: After the reagent is applied, if it is determined that the old fracture has connected to the formation, a sand plug is made to seal all fractures between the heel of the horizontal well and the packer. Then, by test extrusion, the effectiveness of sand plugging is judged. Based on the corresponding relationship between the required discharge volume and pressure, when the injection discharge volume is less than 0.5 cubic meters, the pump pressure rises to the upper limit of the pressure limit, which is judged as effective plugging; if it is not effective plugging, sand plugging treatment continues until it is judged as effective plugging.

6. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, In S3, well washing is carried out until the requirements for fracturing operations are met, specifically: Switch to the forward flushing process, inject fracturing fluid into the coiled tubing to perform forward flushing, observe the surface fluid and sand production, and when no sand returns, perform a flush of one annular volume.

7. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, Hydraulic sandblasting and perforation operations were carried out in S3, specifically as follows: The annulus of the casing and casing is either open or throttled open to establish circulation. Displacement fluid is injected into the continuous tubing. Through throttling via the nozzle, the high-pressure displacement fluid in the tubing is transformed into a high-speed jet that penetrates the casing and cement annulus, creating a channel between the reservoir and the wellbore, thus completing the perforation operation.

8. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, In S3, new hydraulic fractures are formed by annular fracturing with sand addition. Specifically: Fracturing is performed by injecting pre-flush fluid, proppant-carrying fluid, and displacement fluid into the annulus of the oil casing to open up the formation and form new fractures.

9. The method for reverse-sequence repeated fracturing of a horizontal well according to claim 1, characterized in that, After fracturing is completed in S3, the annulus of the oil casing is cleaned, specifically as follows: After fracturing is completed, the coiled tubing pump is stopped, fracturing fluid is injected through the tubing, and the remaining sand is carried out through the annulus of the casing. The relationship between the amount of sand discharged and the amount of fluid is calculated to provide a basis for the fracturing of subsequent horizontal wells.

10. The horizontal well reverse-sequence repeated fracturing method according to any one of claims 1-9 is applied in tight conglomerate oil reservoirs.

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