Method for staged refracturing of fractured well

Abstract

The invention belongs to the technical field of oil and gas development, and discloses a fractured well staged re-fracturing method which comprises the steps that a target shaft is re-perforated to form a new perforation, and the position of the new perforation is different from the position of an old perforation of the shaft; fracturing fluid is injected into the first fracturing section of the shaft, and new and old cracks are fractured; fluid containing a blocking agent is injected into the wellbore to block a perforation in the target wellbore, and a part of the blocking agent enters the perforation; the perforation plugging effect is checked through the fracturing monitoring data; the re-fracturing construction of the section is completed; and dragging the packer to the second fracturing section by the oil pipe, and repeating the steps until the repeated fracturing construction of the whole shaft section is completed. The plugging agent with the deformable part and the rigid spheroid is adopted, crack perforation can be effectively plugged in the construction process, the bidirectional fixing capacity of falling prevention and squeezing prevention is achieved, and meanwhile the plugging agent can cope with special-shaped perforation holes existing in a shaft.

Description

Technical Field

[0001] The present application belongs to the technical field of oil and gas development, and specifically relates to a method for repeated staged fracturing of a fracturing well. Background Art

[0002] At present, fracturing technology has become an important measure to increase the production of oil and gas wells. However, during the initial transformation of oil and gas wells, due to the limitations of fracturing equipment, processes, materials and other factors, the scale of fracturing is not enough and effective supporting cracks cannot be formed; or over time, the cracks gradually close under the action of ground stress, and the flow channels of formation fluids are blocked. Repeated fracturing technology is needed to improve the mining effect and increase production. During the initial fracturing, the wellbore is damaged by multiple loading and flushing of high-pressure fluids, and the strength and integrity of the casing may be damaged. The blastholes will present irregular perforations such as elliptical, bullet-shaped, and rectangular. Therefore, it is still difficult to ensure the integrity and strength of the wellbore after the initial fracturing through effective technology. The current targeted technologies mainly include casing-in-casing technology, mechanical isolation technology, and chemical temporary plugging technology.

[0003] The casing-in-casing re-fracturing technology is to re-insert a small-sized casing into the target wellbore and seal the entire perforation section by cementing, etc. However, the inner diameter of the wellbore is greatly reduced after the construction, which greatly limits the operating pressure and displacement of the re-fracturing, and the operation time is long and the cost is high.

[0004] The mechanical isolation method is to use a packer to separate the well section that needs to be modified, and then use tubing injection for secondary fracturing. At present, the most widely used process is the double-seal single-card drag fracturing process, which has problems such as fixed packer spacing and high positioning difficulty. Among them, the expansion tube wellbore reconstruction technology is to lower the expansion tube into the target wellbore, expand the expansion tube by hydraulic or mechanical methods, and the rubber or metal sealing material outside the tube achieves a reliable seal between the expansion tube and the casing under the action of extrusion to seal the old perforations. However, the expansion tube has high strength requirements, and there are problems such as the longer the target wellbore, the more difficult the implementation process, and the higher the cost.

[0005] The chemical temporary plugging and repeated fracturing technology (also known as Bullhead Refrac technology) is to first re-perforate the old fracturing well. The location of the new perforation is different from the original perforation location, and then inject a fluid containing a temporary plugging agent into the well for fracturing. During the fracturing process, the temporary plugging agent will randomly block a portion of the perforations with a large amount of fluid inflow. By injecting temporary plugging agents in batches to plug perforations at different locations during the fracturing process, the purpose of creating new cracks in batches is achieved. Although the cost of chemical temporary plugging and repeated fracturing technology is low, the temporary plugging effect is uncontrollable. It is impossible to predict which perforations each batch of fracturing fluid and temporary plugging agent will enter, nor is it possible to predict which perforations new cracks will start from.

[0006] The existing patent application CN108625841A discloses a repeated fracturing method combining horizontal well annulus sealing with ball-dropping sliding sleeves, in which an oil pipe with a smaller inner diameter is lowered into the wellbore of an old horizontal well completed by casing cementing, and a temporary plugging agent is injected into the annulus between the oil pipe and the casing. After the horizontal section oil and casing annulus is sealed, a new fracturing channel is formed, and temporary plugging materials are used to seal the sections and the ball-dropping sliding sleeve is used to perform segmented fracturing.

[0007] The limitations of the above-mentioned prior art are: (1) the entire annular control needs to be blocked, which makes the inner diameter of the wellbore smaller, limiting the displacement and operating pressure of the fracturing; (2) the cost of multi-stage sealing materials is high; (3) the positioning between the ball-dropping sliding sleeve packers is difficult; and (4) a gel breaker needs to be injected into the annulus to resume production.

[0008] In addition, fracturing with ball-drop sleeves has the following disadvantages: (1) The manufacturing and use costs of the sleeves and supporting tools are high; (2) The sleeve system takes up a certain amount of space in the wellbore, which may limit the operating space of the tools, especially in small-diameter wellbores, affecting the flexibility of subsequent operations; (3) As the size of the ball gradually increases, the number of segments of the ball-drop sleeve is usually limited, generally around 15-30. When the number of fracturing segments is too large, the increase in the size of the ball will cause the liquid column pressure to be too high or affect the ball transfer; (4) In long horizontal sections or wells with large well deviations, the ball transfer may be affected by friction or wellbore complexity, resulting in ball delivery failure or inability to accurately reach the target sleeve.

[0009] Existing patent application CN105275442A discloses a volume fracturing process for repeated transformation of old wells. According to the reservoir temperature, pressure, water production rate and mineralization, the type of fracturing fluid is screened and the dynamic and static performance evaluation is performed to determine the final required fracturing fiber and particle temporary plugging agent; the old cracks are temporarily plugged and diverted to form new cracks to expand the transformation area. Patent CN107587867A discloses a repeated fracturing process for improving the complexity of shale fracture network. For candidate well sections, the stress balance equation of discrete fractures is established to obtain the fracture diversion pressure, and then the strength and dosage of the temporary plugging agent are determined according to the fracture height, particle settling rate, etc., and finally the construction displacement of the repeated fracturing fracture diversion extension is calculated.

[0010] The limitations of the above two technologies are: (1) the temporary plugging effect of old fractures using temporary plugging agents lacks post-fracture evaluation, and the effectiveness of fracture diversion cannot be ensured. (2) The oil and gas resources between old fractures near the wellbore section are not effectively utilized.

[0011] Existing patent applications CN105275442A and CN107587867A are essentially batch chemical temporary plugging repeated fracturing technologies, which cannot predict which perforations the fracturing fluid and temporary plugging agent will enter, nor can they predict which perforations new cracks will initiate.

[0012] Therefore, in order to improve the recovery rate of fractured oil and gas wells, there is an urgent need for a staged repeated fracturing method for old fractured wells with low construction cost and controllable construction effect. Summary of the invention

[0013] The present application proposes a method for staged re-fracturing of a fracturing well, so as to solve the problem that the chemical temporary plugging re-fracturing technology in the prior art cannot achieve staged fracturing without the aid of a downhole fixed isolation device.

[0014] In order to solve the above technical problems, the technical solution adopted in this application is:

[0015] A method for staged repeated fracturing of a fracturing well, the method comprising:

[0016] Re-perforating the target wellbore to form new perforations; wherein the target wellbore has old perforations, and the positions of the new perforations are different from the positions of the old perforations;

[0017] Divide the target wellbore into at least two fracturing sections, and perform repeated fracturing operations on each fracturing section in turn; wherein the repeated fracturing operations include:

[0018] Injecting fracturing fluid into the fracturing section of the target wellbore to fracture new and old fractures;

[0019] Injecting a fluid containing a plugging agent into the fracturing section of the target wellbore to plug the perforations of the fracturing section; the perforations include new perforations and old perforations;

[0020] The perforation plugging effect is determined based on the fracturing monitoring data, and the perforation plugging effect includes plugging success and plugging failure; when the perforation plugging effect is plugging success, the repeated fracturing construction of the current fracturing section is completed, and the repeated fracturing construction of the next fracturing section is carried out; when the perforation plugging effect is plugging failure, the fluid containing the plugging agent continues to be injected into the fracturing section of the target wellbore until the perforation plugging effect is plugging success.

[0021] Preferably, after completing the repeated fracturing construction of the current fracturing section, the packer is dragged to the next fracturing section by using the oil pipe to perform repeated fracturing construction.

[0022] Preferably, when the injected fracturing fluid is insufficient to create new fractures, the method comprises:

[0023] When the new perforations and the old perforations are concentrated, shorten the length of the current fracturing stage, separate the old perforations and the new perforations with packers, use them as primary fracturing stages respectively, and then perform repeated fracturing operations;

[0024] When the new perforations and the old perforations are staggered, the fracturing stage is maintained, the fracturing fluid pressure is controlled to open only the old cracks, a plugging agent is injected to plug the old perforations, and finally the fracturing fluid is re-injected into the new perforations to create new cracks.

[0025] Preferably, the plugging agent includes a deformable part and a rigid spherical part. Under the action of the fluid, the deformable part enters the perforation, and the rigid spherical part remains in the target wellbore, having a bidirectional fixing capability.

[0026] Preferably, the density of the plugging agent is less than or equal to the density of the fluid.

[0027] Preferably, the fracturing monitoring data is bottom hole pressure, which is calculated by monitoring wellhead pressure and using a wellbore flow model.

[0028] Preferably, determining the perforation plugging effect based on the fracturing monitoring data includes:

[0029] If the bottom hole pressure reaches or exceeds the formation rock fracture pressure, the perforation plugging effect is determined to be successful;

[0030] If the bottom hole pressure does not reach or exceed the formation rock fracture pressure, it is determined that the perforation plugging effect is a plugging failure.

[0031] Preferably, the blocking agent is degradable.

[0032] Preferably, the plugging agent comprises at least one deformable plugging agent.

[0033] Preferably, a plugging agent is added during the repeated fracturing construction process, and before the construction is completed, the plugging agent is added again to perform a plugging pressure test to obtain fracturing monitoring data.

[0034] The benefits of this application are:

[0035] According to a method for repeated fracturing of a fracturing well in stages provided by the present application, on the one hand, a plugging agent having a deformable portion and a rigid spherical body is used, which can effectively seal crack perforations during construction, and has a bidirectional fixing ability of preventing falling off and squeezing in, and is not easy to fall off even when the pressure in the perforation is greater than the pressure in the wellbore, and can also cope with the irregular perforations in the wellbore; on the other hand, the wellbore is repeatedly fractured in stages by dragging the packer through the oil pipe, first sealing a part of the existing crack perforations, and then selecting a part of the crack perforations to pump fracturing fluid, so as to achieve precise control of the starting position of new cracks, and at the same time, reduce the requirements for ground construction equipment (such as lower displacement and lower pressure level), thereby reducing construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without paying creative labor.

[0037] Figure 1 A process for a method for repeated staged fracturing of a fracturing well provided in an embodiment of the present application Figure 1 .

[0038] Figure 2 A schematic diagram of the start of plugging of the first fracturing stage of the target wellbore provided in an embodiment of the present application.

[0039] Figure 3 A schematic diagram of a pressure test of the first fracturing stage after plugging of a target wellbore provided in an embodiment of the present application.

[0040] Figure 4 A schematic diagram of a pressure test of the first fracturing stage after plugging of a target wellbore provided in an embodiment of the present application.

[0041] Figure 5 A schematic diagram of starting construction of a second fracturing stage in a target wellbore provided in an embodiment of the present application.

[0042] Figure 6 A schematic diagram of staged fracturing construction of new and old perforated wellbore sections provided in an embodiment of the present application.

[0043] Figure 7 A schematic diagram of the construction process of first sealing old cracks by perforating and then fracturing to create new cracks provided in an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] In order to solve the problems existing in the current repeated fracturing technology, such as insufficient sealing of plugging materials, incomplete utilization of core layers, and high difficulty in locating new cracks during re-fracturing. The embodiment of the present application provides a method for staged repeated fracturing of a fracturing well, the method comprising: re-perforating a target wellbore to form new perforations; wherein the target wellbore has old perforations, and the positions of the new perforations are different from the positions of the old perforations; dividing the target wellbore into at least two fracturing sections, and repeating the fracturing construction on each fracturing section in turn; wherein the repeated fracturing construction comprises: injecting fracturing fluid into the fracturing section of the target wellbore to fracture new and old cracks; injecting a fluid containing a plugging agent into the fracturing section of the target wellbore to seal the perforation of a fracturing section, and a part of the plugging agent enters the perforation; the perforation includes new perforations and old perforations; the perforation plugging effect is determined based on the fracturing monitoring data, and the perforation plugging effect includes plugging success and plugging failure; when the perforation plugging effect is plugging success, the repeated fracturing construction of the current fracturing section is completed, and the repeated fracturing construction of the next fracturing section is performed; when the perforation plugging effect is plugging failure, the fluid containing the plugging agent is continuously injected into the fracturing section of the target wellbore until the perforation plugging effect is plugging success.

[0046] The following embodiment of the present application will take the target wellbore including the first fracturing stage and the second fracturing stage as an example to elaborate on the implementation process of the method for staged repeated fracturing of the fracturing well. It should be noted that the first fracturing stage and the second fracturing stage here do not mean that the method proposed in the present application is only applicable to staged repeated fracturing of a fracturing well with two fracturing stages. This embodiment is only an example and does not constitute a limitation to the present application.

[0047] Embodiment 1:

[0048] Figure 1 This is a flow chart of a method for repeated staged fracturing of a fracturing well according to an embodiment of the present application. Figure 1 As shown, the embodiment of the present application provides a method for staged repeated fracturing of a fracturing well. In this implementation, a horizontal well is taken as an example. It is worth noting that the method is also applicable to vertical wells and inclined wells. The specific steps include S101 to S106.

[0049] S101: re-perforating the target wellbore to form new perforations.

[0050] In step S101, a perforating gun (not shown) is pumped down from the wellhead via a cable into a well. Figure 2 As shown, the first designed new perforation 204 is located, and then the perforating gun is dragged to the next designed perforation in sequence until the perforations designed for the entire wellbore section are completed and the perforating gun is taken out. At the same time, the position of the new perforation 204 is different from the position of the old perforation 200.

[0051] In some embodiments, before perforating the target wellbore 206, candidate wells are identified, reservoir quality, completion and production parameters are selected, and the number and location of perforations are designed. In some embodiments, before repeated fracturing, a physical model can be established to study the influence of different factors on the repeated fracturing effect, so as to select the target well, perforation parameters and fracturing operation parameters.

[0052] S102: Inject fracturing fluid into the first fracturing stage of the target wellbore to fracture new and old cracks.

[0053] In step S102, Figure 2 As shown, a tubing 208 with a packer 212 is run into the target wellbore 206 to the position of the designed first fracturing stage, and a fracturing fluid 210 is injected into the first fracturing stage to fracture the old fractures 202 and Figure 3 The new fractures 214 shown are multiple in number. The permeate or product from the production layer enters the wellbore through the new fractures 214 and the new perforations 204 and can be produced on the surface.

[0054] In some embodiments, the packer 212 may be made of a soluble material.

[0055] In some embodiments, tubing 208 may be any conduit capable of moving fluid.

[0056] In some embodiments, the fracturing fluid 210 generally uses water-based or oil-based fluids. Water-based fracturing fluids have been shown to be harmless except in undersaturated formations. In unsaturated reservoirs, there may be a situation where the recovery rate is low after early screening and treatment. In this case, repeated fracturing treatment using oil-based fluids can increase production.

[0057] In step S102, preferably, 3 to 5 original fracturing stages may be combined into a new fracturing stage, and the total number of perforations in the combined new fracturing stage is less than 200.

[0058] S103: injecting a fluid containing a plugging agent into the target wellbore to plug the perforations in the target wellbore, and a portion of the plugging agent enters the perforations.

[0059] In step S103, Figure 3 As shown, fluid 216 containing plugging agent is pumped into the first fracturing stage through the oil pipe 208 to plug the old perforations 200 and the new perforations 204, so as to prevent the perforations in the first fracturing stage from affecting the fracturing construction of the second fracturing stage. Figure 4 The plugging agent 218 shown enters the perforations 200 of the old fracture 202 and the perforations 204 of the new fracture 214 in the low-pressure area under the carrying effect of the high-pressure injection fluid, wherein the deformable portion of the plugging agent 218 is squeezed into the perforations under the effect of the pressure difference between the target wellbore 206 and the new fracture 214 and the old fracture 202.

[0060] In some embodiments, before pumping plugging agent into the first fracturing stage of the target wellbore 206 to plug the fracture perforation, it is necessary to replenish the formation energy with pre-fluid to replenish the formation pressure in the low-pressure area to prevent the fracture from extending entirely in the low-pressure area.

[0061] In some embodiments, the plugging agent 218 may include at least one deformable plugging agent. For example, the plugging agent 218 is composed of a deformable part and a rigid part. Through "plug-in plugging", the deformable part of the plugging agent is squeezed into the perforation, and the rigid part remains in the wellbore. It has bidirectional fixing capability and can cope with possible irregular perforations.

[0062] In some embodiments, the deformed portion may be filled with any one of a plurality of solid particles, liquids, and gases, or a mixture of any two or more thereof.

[0063] Preferably, the rigid part is made of a high molecular polymer such as polypropylene, polyethylene, carbonate, metal or other rigid material to prevent the plugging agent from being completely immersed in the perforation.

[0064] In some examples, the amount of plugging agent is generally equal to the number of perforations in the stimulated layer, and the plugging layer formed by the plugging agent can withstand a pressure exceeding 25 MPa.

[0065] S104: Check the perforation plugging effect through the pressure monitoring data. If the perforation plugging effect meets the preset standard, execute step S105, if not, return to execute step S104.

[0066] In step S104, Figure 4 As shown, after the plugging construction of the first fracturing stage is completed, the pressure test fluid 220 is injected through the oil pipe 208 to perform a pressure test on the first fracturing stage.

[0067] The pressure test fluid for pressure testing is usually of similar composition to the fracturing fluid.

[0068] It is worth noting that the dynamic relationship between wellhead pressure and bottom hole pressure can be established in combination with the wellbore flow model to evaluate the plugging effect of the anti-plugging agent.

[0069] In some embodiments, it is judged based on the fracturing construction pressure curve data that after the plugging agent is injected, the bottom hole pressure rises rapidly, the number of plugged perforations increases continuously, and the construction pressure rises step by step accordingly. The plugging effect is evaluated by pressure monitoring. If the bottom hole pressure can be increased to above the formation rock fracture pressure, the plugging is successful. If the bottom hole pressure cannot be increased to the formation rock fracture pressure, the plugging agent continues to be injected into the wellbore until the bottom hole pressure can be increased to above the formation rock fracture pressure.

[0070] Formation breakdown pressure is a key parameter in drilling and fracturing design. The formation breakdown pressure at different depths can be obtained by a variety of methods, such as field measurement (overflow test, formation integrity test, small fracturing test, step-by-step pressurization test, etc.), empirical formulas, rock mechanics model equations, logging data, numerical modeling, etc.

[0071] In addition, in some embodiments, during repeated fracturing construction, technical means such as proppant tracers, microseismic monitoring, production logging, distributed temperature / acoustic sensor systems, and ground construction pressure analysis can be used for construction monitoring. With the help of these means, not only can real-time control and adjustment of the construction be performed, but the direction of repeated fracturing cracks and the transformation effect can also be evaluated.

[0072] S105: Complete the repeated fracturing construction in this section.

[0073] S106: The oil pipe drags the packer to the second fracturing stage, and the above steps are repeated until the repeated fracturing construction of all fracturing stages is completed.

[0074] In some embodiments, Figure 5 As shown, after the construction of the first fracturing stage 222 is completed, the oil pipe 208 and the packer 212 are dragged to the preset position of the second fracturing stage 224, and the steps S101 to S105 are repeated.

[0075] In this embodiment, the bottom seal of the oil pipe 208 is used to drag the packer 212 for repeated fracturing construction. Compared with the traditional double-seal single-card method, it can better locate the layer section that needs to be transformed, and the casing in the fracturing section has a large displacement and the perforation is not affected by the casing.

[0076] In addition, in some embodiments, if the plugging of a certain repeated fracturing section cannot be completed after multiple injections of plugging agents (pressure testing shows that the plugging effect is not good), the use of a bridge plug for separation may be considered.

[0077] Embodiment 2:

[0078] In actual operation, when hydraulic fracturing is carried out on the first fracturing stage, there are old cracks and new perforations at the same time. If the fracturing fluid can only support its priority entry into the low-pressure areas of the old cracks, the wellbore pressure at the new perforations will be lower than the formation fracture pressure, resulting in insufficient pressure to create new cracks.

[0079] In order to solve the above problems that may exist in the prior art, different from Example 1, when the old perforations and the new perforations are distributed more concentratedly, in this embodiment, the fracturing section is shortened, and the old crack wellbore section and the new perforation section are respectively used as separate fracturing construction sections to accurately control the formation of new cracks.

[0080] For example, in one embodiment disclosed in the present invention, Figure 6 As shown, after the re-perforation construction of the entire wellbore is completed according to the design plan, the oil pipe 320 and the packer 350 are lowered into the target wellbore to the first fracturing section 300 at the designed position, wherein the first fracturing section 300 only includes the wellbore section where the old cracks 370 are located, and then the fracturing fluid 330 is injected into the oil pipe 320 to further fractur the old cracks 370 (it is worth noting that if the old cracks 370 have no usable oil and gas value, this operation can be omitted). After the fracturing is completed, the plugging agent is injected into the oil pipe 320 to plug the old perforations 360 of the first fracturing section 300. After passing the plugging pressure test, the oil pipe 320 and the packer 350 are dragged to the second fracturing section 310 at the designed position, wherein the second fracturing section 310 only includes the wellbore section where the new perforations 340 are located, and the operations in the first fracturing section 300 are repeated. The entire repeated fracturing construction process includes the cyclic operation of the old crack wellbore section and the new perforation wellbore section until the last designed fracturing section is completed.

[0081] In this embodiment, the fracturing fluid can adjust the pumping pressure of the fracturing fluid according to the fracturing pressure required by the old fractured wellbore section and the new perforated wellbore section to accurately control the formation of new and old fractures.

[0082] In some embodiments, when the old fractures have no usable oil and gas value, the plugging agent may be made of a non-degradable material.

[0083] In some embodiments, the plugging agent used to plug the new perforations 340 is generally made of degradable materials, which can be naturally degraded after repeated fracturing to restore the gas production contribution of the plugged fractures.

[0084] Embodiment 3:

[0085] In actual operation, in order to solve the problem of difficulty in creating new cracks when old cracks and new perforations exist in one fracturing section at the same time, different from Examples 1 and 2, when the old cracks and new perforations are distributed in a staggered manner in the wellbore, in this embodiment, the fracturing section is maintained, and the method of first sealing the old cracks by perforating and then fracturing to create new cracks is adopted to ensure the formation of new cracks.

[0086] For example, in one embodiment disclosed in the present application, Figure 7As shown, a tubing 420 and a packer 450 are lowered into the target wellbore to the first fracturing section 400 at the designed position, wherein old fractures 470 and new perforations 440 exist at the same time and are distributed in a staggered manner. Before injecting the fracturing fluid 430 to create new fractures 480, the fracturing fluid 430 is first injected into the first fracturing section 400, and the pressure of the fracturing fluid 430 is controlled to enter only the old perforations 460 to fractur the old fractures 470, and the pressure does not reach the breaking pressure of the rock at the new perforations 440. Force (it is worth noting that if the old fracture 470 has no usable oil and gas value, this operation can be omitted), and then inject fluid containing plugging agent 490 into the first fracturing stage 400. Since the new perforation 440 does not continuously receive fluid, the plugging agent 490 can only enter the old perforation 460 for plugging. After completing the plugging of all the old perforations 460 of the first fracturing stage 400 and passing the plugging pressure test, the fracturing fluid 430 is injected for fracturing to form new fractures 480. Subsequently, the plugging agent 490 is injected to plug the new perforations 440 and pass the plugging pressure test, completing the repeated fracturing construction of the first fracturing stage 400, and finally dragging the oil pipe 420 and the packer 450 to the next designed fracturing stage until the repeated fracturing construction of the entire wellbore is completed.

[0087] Embodiment 4:

[0088] In actual operation, due to the coexistence of old cracks and new perforations in the fracturing section, or due to the heterogeneity of the formation, the fracture and fracturing of the formation rocks at different perforations are different, which will cause the initiation and expansion of cracks at different positions to be asynchronous. In this embodiment, plugging agent is added during the fracturing process of the fracturing section (it can be added in batches multiple times), and the construction process is the same as the traditional temporary plugging fracturing in the section. The only difference is that before the fracturing construction is completed, the plugging agent needs to be added again and the plugging pressure test is performed.

[0089] For example, in one embodiment disclosed in the present application, Figure 7 As shown, the oil pipe 420 and the packer 450 are lowered into the target wellbore to the first fracturing section 400 at the designed position, and the fracturing fluid 430 is first injected into the first fracturing section 400 for fracturing construction, and then the fluid containing the plugging agent 490 is injected into the first fracturing section 400 to plug the existing cracks (the injection amount of the plugging agent is controlled so that it can plug a part of the perforations that are receiving the fracturing fluid but will not plug all the perforations in the first fracturing section 400). The fracturing fluid without the plugging agent is continuously injected into the first fracturing section 400, and the fracturing fluid enters the remaining perforations that are not plugged. Finally, the fracturing fluid containing the plugging agent is injected into the first fracturing section 400 and the plugging pressure test is passed to complete the repeated fracturing construction of the first fracturing section 400, and finally the oil pipe 420 and the packer 450 are dragged to the next designed fracturing section until the repeated fracturing construction of the entire wellbore is completed.

[0090] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for repeated staged fracturing of a fracturing well, characterized in that: The method comprises: Re-perforating the target wellbore to form new perforations; wherein the target wellbore has old perforations, and the positions of the new perforations are different from the positions of the old perforations; Divide the target wellbore into at least two fracturing sections, and perform repeated fracturing operations on each fracturing section in turn; wherein the repeated fracturing operations include: Injecting fracturing fluid into the fracturing section of the target wellbore to fracture new and old fractures; Injecting a fluid containing a plugging agent into the fracturing section of the target wellbore to plug the perforations of the fracturing section; the perforations include new perforations and old perforations; The perforation plugging effect is determined based on the fracturing monitoring data, and the perforation plugging effect includes plugging success and plugging failure; when the perforation plugging effect is plugging success, the repeated fracturing construction of the current fracturing section is completed, and the repeated fracturing construction of the next fracturing section is carried out; when the perforation plugging effect is plugging failure, the fluid containing the plugging agent continues to be injected into the fracturing section of the target wellbore until the perforation plugging effect is plugging success.

2. The method according to claim 1, characterized in that After completing the repeated fracturing construction of the current fracturing section, the packer is dragged to the next fracturing section by the oil pipe for repeated fracturing construction.

3. The method according to claim 1, characterized in that When the injected fracturing fluid is insufficient to create new fractures, the method comprises: When the new perforations and the old perforations are concentrated, shorten the length of the current fracturing stage, separate the old perforations and the new perforations with packers, use them as primary fracturing stages respectively, and then perform repeated fracturing operations; When the new perforations and the old perforations are staggered, the fracturing stage is maintained, the fracturing fluid pressure is controlled to open only the old cracks, a plugging agent is injected to plug the old perforations, and finally the fracturing fluid is re-injected into the new perforations to create new cracks.

4. The method according to claim 1, characterized in that: The plugging agent includes a deformable part and a rigid spherical part. Under the action of the fluid, the deformable part enters the perforation, and the rigid spherical part remains in the target wellbore, having a bidirectional fixing capability.

5. The method according to claim 1, characterized in that The density of the plugging agent is less than or equal to the density of the fluid.

6. The method according to claim 1, characterized in that The fracturing monitoring data is the bottom hole pressure, which is calculated by monitoring the wellhead pressure and using a wellbore flow model.

7. The method according to claim 6, characterized in that Determine the perforation plugging effect based on fracturing monitoring data, including: If the bottom hole pressure reaches or exceeds the formation rock fracture pressure, the perforation plugging effect is determined to be successful; If the bottom hole pressure does not reach or exceed the formation rock fracture pressure, it is determined that the perforation plugging effect is a plugging failure.

8. The method according to claim 1, characterized in that The plugging agent is degradable.

9. The method according to claim 1, characterized in that: The plugging agent comprises at least one deformable plugging agent.

10. The method according to claim 1, characterized in that During the repeated fracturing construction process, plugging agent is added, and before the construction is completed, plugging agent is added again to perform plugging pressure test to obtain fracturing monitoring data.

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