An embedded long-term temporary plugging method and its multi-cluster fracturing process

Abstract

This invention belongs to the technical field of oil and gas field fracturing and stimulation technology, and particularly relates to an embedded long-term temporary plugging method. It includes a soft rope woven from soluble yarn, tied into a knot, with loose strands at both ends of the knotted rope. The knot is covered by a rubber shell, which is a one-piece structure and spherically shaped. The rubber shell adheres to the outer surface of the knot and fills the external space of the knot. The loose strands at both ends of the knot protrude from the rubber shell and are symmetrically arranged on both sides of the rubber shell. In this invention, the rubber shell can perform the sealing function and biodegradable properties of the knot without breaking, thus solving the problems of existing plugging balls, such as excessive types leading to management difficulties, difficulty in distinguishing them when using a ball-throwing device, easy confusion of plugging balls, and difficulty in controlling the timing and precision of the flow carrier's rupture.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field fracturing technology, specifically referring to an embedded long-term temporary plugging and multi-cluster fracturing process. Background Technology

[0002] In petroleum engineering, fracturing refers to a method of creating fractures in oil or gas reservoirs using hydraulic force during the oil or gas extraction process; it is also known as hydraulic fracturing. Fracturing artificially creates fractures in the formation, improving the underground flow environment for oil, increasing oil well production, and playing an important role in improving bottomhole flow conditions, mitigating inter-layer flow, and improving reservoir dynamics.

[0003] Before fracturing, perforation devices are used to create boreholes on the inner wall of the downhole casing to connect the inside and outside of the casing, allowing fracturing fluid to enter the formation. In actual production, a well typically has multiple perforation sections, and each section contains multiple clusters of perforations. In this case, to achieve effective opening of all clusters and avoid the problem of some perforation clusters not being modified or not being modified sufficiently, temporary plugging devices are needed to temporarily seal some of the perforations in the well. Currently, the most commonly used technology uses rigid plugging balls made of resin. These plugging balls have problems such as poor sealing success rate and poor effectiveness in sealing irregularly shaped perforations.

[0004] To address the problems associated with traditional temporary plugging balls, patent application CN202111581336.8 discloses a plugging device suitable for downhole fracturing operations. This plugging device seals the borehole using a knotted rope, effectively solving the problem. However, as a new technology employing a novel concept, this plugging device still has the following shortcomings that require improvement:

[0005] 1. To facilitate the pumping of the bundle (i.e., the knot) downhole, the plugging device has a flow carrier on the outside of the bundle. During use, the ease of fracturing the flow carrier can be influenced by adjusting its shell thickness, reinforcing ribs, or grooves. This allows the flow carrier to rupture before fracturing operations begin, ensuring the bundle is released. This design has two drawbacks:

[0006] On the one hand, in single-well construction, there are often multiple target depths downhole, so it is necessary to drop various plugging balls with different flow carrier structures. However, the variety of plugging balls can lead to problems such as too many types, difficulty in management, difficulty in distinguishing them when using a ball dropping device, and easy confusion of plugging balls.

[0007] On the other hand, due to the influence of machining accuracy and complex downhole working conditions, the method of influencing the ease of fracture of the flow carrier by adjusting the shell wall thickness, reinforcing ribs or grooves has the problem that the timing of the fracture of the flow carrier is difficult to control and the control accuracy is poor.

[0008] 2. The above-mentioned plugging device relies solely on the knotted structure of the bundle for plugging. However, the shape of the knotted structure is unstable and it is prone to deformation under pressure, which can cause it to slide into the borehole and lead to plugging failure. Summary of the Invention

[0009] The purpose of this invention is to provide an embedded long-lasting temporary plugging device. By optimizing the existing knot-type temporary plugging device, it effectively improves the problems of the existing knot-type plugging device, such as too many types of plugging balls, difficulty in accurately controlling the timing of the breakage of the current carrier (i.e. the plugging ball shell), and the instability of the knot structure leading to plugging failure.

[0010] To achieve the above functions, the technical solution adopted by the present invention is as follows:

[0011] An embedded long-lasting temporary plug includes a soft rope woven from soluble yarn, the soft rope being tied into a knot, and the two ends of the knotted soft rope having loose strands.

[0012] The knot is covered with a rubber shell on the outside;

[0013] The rubber outer shell is a one-piece structure;

[0014] The rubber outer shell is spherical in shape;

[0015] The rubber shell adheres to the outer surface of the knot and fills the external space of the knot;

[0016] The loose strands at both ends of the knot protrude outside the rubber shell and are symmetrically arranged on both sides of the rubber shell.

[0017] As a preferred embodiment, the rubber material of the rubber shell contains soluble yarns, called reinforcing yarns, with the ends of the reinforcing yarns protruding outside the rubber shell.

[0018] As a preferred embodiment, the reinforcing thread is a single yarn that is randomly and haphazardly coiled.

[0019] As a preferred embodiment, the rubber shell includes an inner and an outer rubber structure, wherein the outer rubber is a shell structure with equal wall thickness, and the inner rubber fills the space between the outer rubber and the knot.

[0020] As a preferred embodiment, the soft rope contains a counterweight material for adjusting the knot density, so that the overall density of the knot is not less than 2 g / cm³.

[0021] The density of the rubber shell is not greater than 1.1 g / cm³.

[0022] As a preferred embodiment, the counterweight material is an aluminum-magnesium alloy.

[0023] This invention also provides an embedded long-term temporary plugging multi-cluster fracturing process, comprising the following steps:

[0024] Step 1: After the first multi-cluster perforation, conventional fracturing is carried out. During fracturing, the perforation section with low formation pressure is fracturing and proppant is added first. When the design value of proppant addition for the first cluster is reached, the first cluster fracturing of the first section is completed.

[0025] Step 2: Use a hydraulic pump to deliver an embedded, long-lasting temporary plug to seal the first section of the perforation where the pressure is low.

[0026] Step 3: After the embedded long-term temporary plug completely seals the first section of the low-pressure perforation section, the pressure increases. The first section of the high-pressure perforation section is opened up by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the first section of high-pressure fractures in the formation that were not sealed by the embedded long-term temporary plug.

[0027] Step 4, for the second section of multi-cluster perforations;

[0028] Step 5: After the second multi-cluster perforation is completed, the embedded long-term temporary plug is pumped to seal the remaining perforation section of the first section. The pump pressure is increased and the perforation section of the first section is completely sealed. As the pressure continues to increase, the pore pressure of the relatively low formation pressure in the second perforation section opens the fracture. The pump pressure is reduced and the casing is filled with sand to fracturing the second section. When the sand filling design value is reached, the fracturing of the first cluster of the second section is completed.

[0029] Step 6: Hydraulic pump is used to insert embedded long-acting temporary plugs to seal the second low-pressure perforation section; after the embedded long-acting temporary plugs have completely sealed the second low-pressure perforation section, the pressure increases, and the second high-pressure perforation section is forced open by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the high-pressure fractures in the second section that were not sealed by the embedded long-acting temporary plugs. After the sand is added, the fracturing of the entire second perforation section is completed.

[0030] Step 7: Repeat steps 4-6 to complete the fracturing operation for the other sections;

[0031] Step 8: After fracturing, production begins directly. The embedded long-term temporary plug is broken and dissolved over a certain period of time under the action of the well fluid.

[0032] The beneficial effects of this invention are:

[0033] The embedded long-term temporary plugging multi-cluster fracturing process technology provided by this invention is simple to operate, compact in construction, and rationally designed, and has the following advantages:

[0034] 1. This invention replaces the flow carrier in the prior art with a rubber shell. The rubber shell not only has the same function as the flow carrier in the prior art—facilitating the pumping of the knot to the target area downhole—but also provides the sealing effect and biodegradability of the knot without breaking it. This solves the problems of existing technologies, such as the difficulty in managing multiple types of plugging balls, the difficulty in distinguishing them when using a ball-dropping device, the ease of confusion between plugging balls, and the difficulty in controlling the timing and accuracy of the flow carrier's breakage. Furthermore, in this invention, the flared strands at both ends of the knot are exposed outside the rubber shell, allowing the embedded long-lasting temporary plugging device to function as a guide for the temporary plugging material into the borehole without breaking the rubber shell.

[0035] 2. In this invention, the binding effect of the integrated rubber shell and the supporting effect of the rubber material ensure that the knot will not loosen and is not easily deformed, thereby fully exerting the supporting strength of the knot when sealing the blast hole and further improving the overall supporting strength of the temporary blockage.

[0036] 3. The process described in this invention can be completed using conventional casing completion methods, without the need to run in additional tools. The completion construction is simple and does not require additional procedures. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the first embodiment of the embedded long-term temporary blocking described above.

[0038] Figure 2 This is a schematic diagram of the structure of the second embodiment of the embedded long-term temporary blocking described above.

[0039] Figure 3 This is a flowchart of the multi-cluster fracturing process using the embedded long-term temporary clogging method.

[0040] In the diagram, 1 is the wire harness; 2 is the soft rope; 3 is the knot; 4 is the rubber outer shell; 5 is the outer rubber layer; 6 is the inner rubber layer; and 7 is the reinforcing wire. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described 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.

[0042] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The invention will be further described in detail below with reference to the accompanying drawings.

[0043] Example 1:

[0044] like Figure 1 As shown, in this embodiment, an embedded long-lasting temporary plug includes a soft rope 2 woven from soluble yarn, the soft rope 2 being tied into a knot 3, and both ends of the soft rope 2 tied into the knot 3 having loose strands 1. The above are existing technologies cited in the background art, and will not be repeated here.

[0045] In practice, the soluble yarn material can be made of high molecular weight polyglycolic acid (PGA). High molecular weight PGA is obtained through ring-opening polymerization. When the average molecular weight of PGA reaches 20,000–145,000, the polymer can be drawn into fibers to form precursor fibers. These precursor fibers can give the polymer molecules a directional arrangement and also enhance the strength of the PGA. The aforementioned precursor fibers are loose bundles composed of several monofilaments, which are spun into yarn, and then the yarn is woven into high-strength soft ropes 2 that meet the strength requirements for sealing.

[0046] In actual production, because the borehole diameters of underground blast holes vary, it is necessary to match different sizes of knots 3. Specifically, different diameter yarns are used to facilitate subsequent weaving into knots 3 of varying diameters. The correspondence between knot 3 and yarn diameter can be as follows:

[0047]

[0048] like Figure 1 As shown, a key innovation of this invention is that the knot 3 is covered by a rubber shell 4, which is a one-piece structure and spherical in shape. The binding effect of the one-piece rubber shell 4 and the supporting effect of the rubber material ensure that the knot 3 will not loosen or deform easily, thus maximizing the supporting strength of the knot 3 when sealing the blast hole and further improving the overall supporting strength of the temporary blockage. In specific implementation, the rubber shell 4 preferably uses common rubber types with poor oil resistance and aging resistance to improve the decomposition rate.

[0049] When sealing the borehole, the rubber outer shell 4 tightly wraps around the outside of the knot 3 under pressure. Compared with the rigid flow carrier used in the prior art, the rubber outer shell 4 not only has the same function as the flow carrier in the prior art, which facilitates the pumping of the knot 3 to the target area downhole, but also provides the sealing function and biodegradable properties of the knot 3 without breaking. This solves the problems of the prior art, such as the difficulty in managing too many types of plugging balls, the difficulty in distinguishing them when using a ball-throwing device, the easy confusion of plugging balls, and the difficulty in controlling the timing and accuracy of the flow carrier's breakage.

[0050] like Figure 1As shown, the rubber shell 4 is attached to the outer surface of the knot 3 and fills the outer space of the knot 3. During processing, the adhesiveness of the rubber itself makes it firmly adhere to the knot 3. At the same time, the rubber filling the gaps in the knot 3 will prevent the relative movement of different sections of the soft rope 2, thereby further preventing the knot 3 from loosening.

[0051] like Figure 1 As shown, the unbraced strands 1 at both ends of the knot 3 protrude outside the rubber shell 4 and are symmetrically arranged on both sides of the rubber shell 4. The arrangement of the unbraced strands 1 allows the embedded long-lasting temporary plug of the present invention to function as a guide for the temporary plug to enter the borehole without breaking the rubber shell 4.

[0052] like Figure 3 As shown, the present invention also provides an embedded long-term temporary plugging multi-cluster fracturing process, comprising the following steps:

[0053] Step 1: After the first multi-cluster perforation, conventional fracturing is carried out. During fracturing, the perforation section with low formation pressure is fracturing and proppant is added first. When the design value of proppant addition for the first cluster is reached, the first cluster fracturing of the first section is completed.

[0054] Step 2: Use a hydraulic pump to deliver an embedded, long-lasting temporary plug to seal the first section of the perforation where the pressure is low.

[0055] Step 3: After the embedded long-term temporary plug completely seals the first section of the low-pressure perforation section, the pressure increases. The first section of the high-pressure perforation section is opened up by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the first section of high-pressure fractures in the formation that were not sealed by the embedded long-term temporary plug.

[0056] Step 4, for the second section of multi-cluster perforations;

[0057] Step 5: After the second multi-cluster perforation is completed, the embedded long-term temporary plug is pumped to seal the remaining perforation section of the first section. The pump pressure is increased and the perforation section of the first section is completely sealed. As the pressure continues to increase, the pore pressure of the relatively low formation pressure in the second perforation section opens the fracture. The pump pressure is reduced and the casing is filled with sand to fracturing the second section. When the sand filling design value is reached, the fracturing of the first cluster of the second section is completed.

[0058] Step 6: Hydraulic pump is used to insert embedded long-acting temporary plugs to seal the second low-pressure perforation section; after the embedded long-acting temporary plugs have completely sealed the second low-pressure perforation section, the pressure increases, and the second high-pressure perforation section is forced open by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the high-pressure fractures in the second section that were not sealed by the embedded long-acting temporary plugs. After the sand is added, the fracturing of the entire second perforation section is completed.

[0059] Step 7: Repeat steps 4-6 to complete the fracturing operation for the other sections;

[0060] Step 8: After fracturing, production begins directly. The embedded long-term temporary plug is broken and dissolved over a certain period of time under the action of the well fluid.

[0061] The temporary plugging fracturing process provided by this invention is simple to operate, compact in construction, and rationally designed, and has the following advantages:

[0062] The process described in this invention enables effective opening of the entire perforation cluster, allowing for full modification of all perforation clusters. It can be completed using conventional casing completion methods, eliminating the need for additional tools and simplifying the completion process without adding extra steps. No other downhole tools, such as drill jigs, need to be pulled up or down before or after fracturing, eliminating any construction risks and saving operating costs. After fracturing, production can proceed directly without any further operations. The embedded long-lasting temporary plug is fully biodegradable, with the final degradation products being carbon dioxide and water, resulting in no pollution, zero damage to the formation, and making it an environmentally friendly material. No other downhole tools are left after fracturing, and the wellbore remains in its full borehole capacity, allowing for further downhole operations in the later stages of production.

[0063] Example 2:

[0064] The difference between this embodiment and Embodiment 1 lies in the structure of the rubber outer shell 4.

[0065] like Figure 2 As shown in the illustration, in a specific embodiment, the rubber material of the rubber shell 4 contains soluble yarns, referred to as reinforcing yarns 7, with the ends of the reinforcing yarns 7 protruding outside the rubber shell 4. After fracturing, the reinforcing yarns 7 gradually hydrolyze, forming numerous tiny channels inside the rubber, making the rubber shell 4 easier to disintegrate. In practice, the reinforcing yarns 7 preferably use yarns with a larger diameter, specifically yarns or bundles 1 with a diameter of not less than 1.5 mm after twisting, to ensure the hydrolysis rate of the reinforcing yarns 7.

[0066] like Figure 2 As shown in the figure, in a specific embodiment, the reinforcing thread 7 is a single yarn that is randomly and randomly coiled. The setting of a single yarn ensures that water can gradually hydrolyze the yarn along the direction of the yarn.

[0067] like Figure 2 As shown in the illustration, in a specific embodiment, the rubber outer shell 4 includes an inner rubber layer 6 and an outer rubber layer 5. The outer rubber layer 5 is a shell structure with a uniform wall thickness, and the inner rubber layer 6 fills the space between the outer rubber layer 5 and the knot 3. This double-layer rubber structure design significantly reduces the constraint of the outer rubber layer 5, which is bound by the edge of the borehole, on the inner rubber layer 6. This allows the inner rubber layer 6 to more easily adapt to changes in the shape of the knot 3 and its relative position to the borehole, thus maximizing the advantages of the knot 3 structure during sealing.

[0068] like Figure 2 As shown, in a specific embodiment, the soft rope 2 contains a counterweight material for adjusting the density of the knot 3, so that the overall density of the knot 3 is not less than 2 g / cm³; the density of the rubber outer shell 4 is not greater than 1.1 g / cm³. Figure 2 As shown, in a specific embodiment, the counterweight material is an aluminum-magnesium alloy. The reason for the special design of the density is:

[0069] In fracturing, the density of fracturing fluid is typically in the range of 1.2-1.5 g / cm³, while the density of polyglycolic acid is 1.5 g / cm³. Since gaps inevitably exist in the knot 3, its density is less than 1.5 g / cm³. Common rubber materials generally have a density of 0.9-1.5 g / cm³. In this case, to make the overall density of the temporary plug closer to the density of the fracturing fluid, the overall density of the temporary plug needs to be adjusted, thus requiring an increase in the overall density of the knot 3. Furthermore, by increasing the overall density of the knot 3, a lower-density rubber can be used to manufacture the rubber outer shell 4, making it easier for the rubber outer shell 4 to be returned to the well later.

[0070] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. An embedded long-lasting temporary plug, comprising a soft rope (2) woven from soluble yarn, the soft rope (2) being tied into a knot (3), and the two ends of the soft rope (2) tied into the knot (3) having loose strands (1), characterized in that: The outside of the knot (3) is covered with a rubber shell (4); The rubber outer shell (4) is spherical in shape; The rubber shell (4) is attached to the outer surface of the knot (3) and fills the outer space of the knot (3); The loose strands (1) at both ends of the knot (3) are exposed outside the rubber shell (4) and are symmetrically arranged on both sides of the rubber shell (4); The rubber material of the rubber shell (4) contains soluble yarns, called reinforcing yarns (7), and the ends of the reinforcing yarns (7) protrude outside the rubber shell (4). The rubber shell (4) includes two layers of rubber structure, including an inner layer of rubber (6) and an outer layer of rubber (5), wherein the outer layer of rubber (5) is a shell structure with equal wall thickness, and the inner layer of rubber (6) fills the space between the outer layer of rubber (5) and the knot (3).

2. The embedded long-term temporary blocking method according to claim 1, characterized in that: The reinforcing thread (7) is a yarn that is randomly and haphazardly coiled.

3. The embedded long-term temporary blocking method according to claim 1, characterized in that: The soft rope (2) contains a counterweight material for adjusting the density of the knot (3), so that the overall density of the knot (3) is not less than 2 g / cm³. The density of the rubber shell (4) is not greater than 1.1 g / cm³.

4. An embedded long-term temporary blocking method according to claim 3, characterized in that: The counterweight material is an aluminum-magnesium alloy.

5. A multi-cluster fracturing process employing an embedded long-term temporary plugging method as described in any one of claims 1-4, characterized in that... Includes the following steps: Step 1: After the first multi-cluster perforation, conventional fracturing is performed. During fracturing, the perforation section with low formation pressure is the first to initiate fracturing. Propane fracturing is then performed. When the design value for proppane addition for the first cluster is reached, the first cluster fracturing of the first section is completed. Step 2: Use a hydraulic pump to deliver an embedded, long-lasting temporary plug to seal the first section of the perforation where the pressure is low. Step 3: After the embedded long-term temporary plug completely seals the first section of the low-pressure perforation section, the pressure increases. The first section of the high-pressure perforation section is opened up by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the first section of high-pressure fractures in the formation that were not sealed by the embedded long-term temporary plug. Step 4, for the second section of multi-cluster perforations; Step 5: After the second multi-cluster perforation is completed, the embedded long-term temporary plug is pumped to seal the remaining perforation section of the first section. The increase in pump pressure indicates that the first perforation section is completely sealed. As the pressure continues to rise, the pore pressure of the relatively low formation pressure in the second perforation section opens the fracture. After the pump pressure decreases, the casing is sanded to fracturing the second section. When the sanding design value is reached, the fracturing of the first cluster of the second section is completed. Step 6: Hydraulic pump is used to insert embedded long-acting temporary plugs to seal the second low-pressure perforation section; after the embedded long-acting temporary plugs have completely sealed the second low-pressure perforation section, the pressure increases, and the second high-pressure perforation section is forced open by the hydraulic pressure. After the pump pressure drops, the casing is filled with sand to continue fracturing the high-pressure fractures in the second section that were not sealed by the embedded long-acting temporary plugs. After the sand is added, the fracturing of the entire second perforation section is completed. Step 7: Repeat steps 4-6 to complete the fracturing operation for the other sections; Step 8: After fracturing, production begins directly. The embedded long-term temporary plug will break down and dissolve after a certain period of time under the action of the well fluid.

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