A method for plugging a fracture in a high water cut reservoir of an oil well

Abstract

The present application belongs to the technical field of exploitation, and particularly relates to a plugging method for oil well high water cut reservoir fracturing cracks. The method comprises the following steps: arranging solid phase plugging particles which can be combined with liquid in the oil field well high water cut fracturing pipeline, the solid phase plugging particles are combined with the water seepage in the high water cut reservoir fracturing cracks to form water control plugging agent; the water control plugging agent is melted in the high water cut reservoir to be bonded, a bonded glue is formed, and the bonded glue is attached to the inside of the high water cut reservoir to plug the high water cut reservoir. The method can realize the violent water flooding caused by the overlap of the new cracks formed in the fracturing process and the high water cut reservoir, avoid the direct contradiction between the water plugging construction and the fracturing construction, and avoid the situation that the oil production in the deep part of the oil reservoir cannot meet the oil production reduction due to the water flooding in the oil well exploitation process.

Description

Technical Field

[0001] This invention belongs to the field of mining technology, specifically relating to a method for sealing fractures in high water-cut oil well reservoirs. Background Technology

[0002] Currently, the oilfield has partially entered the development stage with medium to high water cut. However, due to formation heterogeneity and the further aggravation of heterogeneity caused by water injection development, high-permeability channels have formed in the oil reservoir, resulting in long-term inefficient or ineffective water circulation in injection and production wells. This has led to significant economic and environmental pressures and seriously affected the effectiveness of waterflooding development. To address the inefficient and ineffective water circulation, oilfields both domestically and internationally have widely adopted water shut-off and profile control technologies to improve the situation. However, as water injection development progresses, conventional well water shut-off technologies are limited to blocking crossflow channels in the near-wellbore area. Furthermore, artificial high-conductivity fractures created in the near-wellbore area for fracturing and production enhancement have damaged the shut-off area, accelerated the water flooding process, and reduced the amount of oil produced by fracturing, making it impossible to meet the long-term water control needs of deep reservoirs. Summary of the Invention

[0003] The purpose of this invention is to provide a method for sealing fractures in high water-cut oil well reservoirs, in order to solve the problems in the prior art;

[0004] To achieve the above technical solution, the present invention provides the following technical solution:

[0005] A method for sealing fractures in high water-cut oil wells is characterized by comprising placing solid-phase plugging particles that are compatible with the liquid in the oil well within the high water-cut fracturing pipeline of the oil well. During the fracturing process, the solid-phase plugging particles enter the high water-cut reservoir and form a water-controlling plugging agent. The water-controlling plugging agent adheres within the high water-cut reservoir, forming an adhesive that attaches to the fractures within the high water-cut reservoir, thereby sealing the fracturing fractures in the high water-cut reservoir.

[0006] Furthermore, the preparation method of the water-controlling plugging agent includes,

[0007] Add a synergist to the liquid phase of the carrier liquid and stir until homogeneous to form an oil phase mixture;

[0008] The prepared phase-inversion solid particles are uniformly dispersed into the oil phase mixture to form an oil-solid mixture;

[0009] A crosslinking agent is added to the oil-solid mixture and stirred until homogeneous to form a water-controlling and plugging agent.

[0010] Furthermore, the phase-inversion solid particles are ethylene-vinyl acetate copolymers.

[0011] Furthermore, the density of the phase transition solid particles is 0.9 cm / m. 3 -0.98cm / m3 .

[0012] Furthermore, the crosslinking agent is vinyltrimethoxysilane, vinyltriethoxysilane, or γ-aminopropyltriethoxysilane.

[0013] Furthermore, the carrier fluid is diesel oil, white oil, or an oil-water emulsion of diesel oil or white oil mixed with water.

[0014] Furthermore, the synergist is polyoxyethylene octylphenol ether-10.

[0015] Furthermore, the solid particles are determined based on the pore throat radius of the oil well during use. The pore throat radius is calculated as follows: R = (8K / φ)¹ / ⁴, where φ is the porosity and K is the permeability (μm). 2 ), where R is the throat radius (μm).

[0016] Furthermore, when the solid-phase plugging particles are installed in the high water-cut fracturing pipeline of an oilfield well, the content of the solid-phase plugging particles is determined according to the water content in the high water-cut reservoir. The calculation method for the water content in the reservoir is: C = K·h·△P1, where C is the addition concentration; K is the content ratio coefficient; △P1 is the unit breakthrough pressure; and h is the effective injection depth.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] This invention discloses a method for sealing and fracturing high water-cut reservoirs in oil wells. During oil well fracturing and extraction, solid-phase plugging particles are pumped in during the fracturing process. These particles form a water-controlling plugging agent within the high water-cut reservoir. The water-controlling plugging agent melts at the reservoir temperature and adheres to the interior of the high water-cut reservoir, forming an adhesive that adheres to the reservoir interior. This achieves sealing of the high water-cut reservoir and prevents artificial fractures from extending within the high water-cut reservoir during the fracturing process. This avoids the formation of sudden water flooding and prevents situations where water flooding during oil well extraction results in the inability to meet long-term water control requirements at deep reservoirs and a reduction in extracted oil volume. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] In the attached diagram:

[0021] Figure 1 This is a schematic flowchart of the water-control plugging agent preparation method in a method for sealing fractures in high water-cut oil well reservoirs according to the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0023] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0024] This invention discloses a method for sealing fractures in high water-cut oil wells. The method includes first pumping a liquid system containing solid-phase plugging particles during high water-cut fracturing operations. These solid-phase plugging particles melt within the high water-cut reservoir to form a water-controlling plugging agent. After melting, the water-controlling plugging agent binds within the high water-cut reservoir, forming a bonding adhesive that seals the reservoir, effectively inhibiting the propagation of fractures formed during fracturing within the high water-cut reservoir. To improve the later-stage development effect of waterflooding in water-cut reservoirs, this method injects a phase-change solid phase capable of forming a water-controlling plugging agent and bonding adhesive within the reservoir at reservoir temperatures. This seals high-permeability channels within the reservoir, improving the fracturing and production enhancement effect, increasing the oil production from fracturing, and meeting the long-term water control requirements of deep reservoirs. It also avoids the sudden water flooding caused by the overlap of new fractures with the high water-cut reservoir during fracturing, while simultaneously avoiding direct conflicts between water shut-off and fracturing operations, and preventing situations where water flooding during oil well production leads to reduced oil production in deeper reservoirs.

[0025] Specifically, the water-controlling plugging agent comprises phase-inversion solid particles, a crosslinking agent, and a carrier fluid. One fracturing method of the present invention for fracturing fractures in high water-cut oil well reservoirs involves the following steps when the water-controlling plugging agent is injected into the fracturing fracture:

[0026] (1) For reservoirs with permeability ≤50mD, add a carrier fluid containing 1%-5% phase change solid particles and 0.5%-1% crosslinking agent during fracturing, injecting it at 0-30% of the total water injection volume. Preferably, the carrier fluid containing 3%-5% solid particles and 0.2%-0.5% crosslinking agent accounts for 10%-15% of the total injection volume.

[0027] (2) For reservoirs with permeability > 50mD, add a liquid solution containing 5%-50% phase change solid particles and 2%-5% crosslinking agent during fracturing, injecting it at 40%-100% of the total water injection volume. Preferably, the solid particles contain 10%-15% and the crosslinking agent contains 3%-4%, accounting for 45%-50% of the total injection volume.

[0028] Specifically, the preparation method of the water-controlling plugging agent, such as Figure 1 As shown, including,

[0029] Add a synergist to the liquid phase of the carrier liquid and stir until homogeneous to form an oil phase mixture;

[0030] The prepared phase-inversion solid particles are uniformly dispersed into the oil phase mixture to form an oil-solid mixture;

[0031] A crosslinking agent is added to the oil-solid mixture and stirred evenly to form a water-controlling and plugging agent.

[0032] Specifically, the carrier liquid contains polyoxyethylene octylphenol ether, polyoxyethylene sorbitan fatty acid ester, or oxyethylene hydrogenated castor oil. Preferably, the carrier liquid contains polyoxyethylene octylphenol ether-10. Preferably, the carrier liquid is added to the above liquid at a ratio of 1% to 10% of the carrier liquid mass.

[0033] Preferably, the phase-inversion solid particles are ethylene-vinyl acetate copolymer.

[0034] Preferably, the density of the phase transition solid particles is 0.9 cm / m³. 3 -0.98cm / m 3 .

[0035] Specifically, the phase-transformation solid particles are characterized by the ability to select the particle softening temperature point according to the reservoir temperature, and the time for the solid phase to complete the transformation into the liquid phase is 20-60 minutes, preferably 30-50 minutes.

[0036] Preferably, the crosslinking agent is vinyltrimethoxysilane, vinyltriethoxysilane, or γ-aminopropyltriethoxysilane.

[0037] Preferably, the carrier fluid is diesel oil, white oil, or an oil-water emulsion of diesel oil or white oil mixed with water; more preferably, the carrier fluid is No. 32, No. 46, or No. 68 white oil with a viscosity of 20 mg / L. 2 / s-80m 2 / s.

[0038] Preferably, the synergist is polyoxyethylene octylphenol ether-10.

[0039] Specifically, the solid particles used are determined based on the pore throat radius of the oil well. The pore throat radius is calculated as follows: R = (8K / φ)¹ / ⁴, where φ is the porosity and K is the permeability (μm). 2 ), where R is the throat radius (μm).

[0040] Specifically, when solid plugging particles are installed in the high water-cut fracturing pipeline of an oilfield well, the content of solid plugging particles is determined according to the water content in the high water-cut reservoir. The calculation method for the water content in the reservoir is: C = K·h·△P1, where C is the addition concentration; K is the content ratio coefficient; △P1 is the unit breakthrough pressure; and h is the effective injection depth.

[0041] Specifically, the design calculation method for the total pumping rate of water carrying phase-transformation solid particles into fracturing fractures is as follows: V = (R1 - R2)·H·k·φ, where: V - plugging agent dosage, unit: m³. 3 R1 - Aqueous phase-transformation solid particle waterflooding front, unit: m; R2 - Non-phase-transformation solid particle waterflooding front, unit: m; H - Effective reservoir thickness, unit: m; k - High-permeability channel ratio coefficient; φ - Reservoir porosity.

[0042] Specifically, taking a high water-cut reservoir fracturing fracture in an oil well with an oil reservoir thickness of 20m, permeability of 21.3mD, porosity of 18.7%, oil saturation of 32.4%, current water cut of 86.1%, and water intrusion channels accounting for 4.67% as an example, the implementation method of the present invention will be explained.

[0043] When sealing fracturing fractures, ethylene-vinyl acetate copolymer is initially used as the phase transition solid particles. Based on the reservoir pore throat radius and solid particle matching model, nano-sized polyacrylamide solid particles with a diameter of 3-5 μm are preferred. γ-aminopropyltriethoxy is used as the crosslinking agent, with a preferred mass ratio of 1.5%-2%; the liquid phase is white oil with a viscosity of 45 m... 2 / s, add 5% polyoxyethylene octylphenol ether-10; based on the pressure difference ΔP = 2.24 MPa before and after adding nano-polymer particles to the water in the indoor sand-filled pipe test, the injection range is designed to be 50m, and the unit volume concentration of C is determined to be 520 kg / m³. 3 Based on field logging, the oil layer thickness was determined to be H = 35m, the high-permeability channel ratio coefficient k = 3.5%, the porosity φ = 19.5%, the injection depth R = 100m, and the total injection volume of plugging agent V = 12m³. 3 According to the site requirements, a carrier fluid containing 5% phase change solid particles and 1% crosslinking agent was added at 20% of the total addition amount per unit time. This was added during the pre-fracturing fluid injection stage of the fracturing operation. After the pump was stopped for 30 minutes, the subsequent fracturing operation continued. After the operation was completed, the water content was found to have decreased by 15.1%, and the daily oil production increased by 2.1t.

[0044] Specifically, the water-controlling plugging agent of this invention is a water-blocking fracturing process method implemented for high water-cut reservoir oil wells where conventional fracturing methods cause water channeling, failing to achieve the purpose of fracturing and increasing production. It is applied to high water-cut reservoirs that have not undergone fracturing stimulation. The plugging agent is added during the pre-fracturing fluid injection stage to seal high-permeability channels within the reservoir, improving the fracturing and production stimulation effect. Furthermore, the plugging agent does not degrade and become ineffective in a short time after fracturing but remains in the high-permeability channels for a long time, achieving a long-term purpose of water control and oil production enhancement. Therefore, it differs from traditional fracturing temporary plugging agents and their processes. Temporary plugging fracturing or fracturing temporary plugging is used when existing fractures have already been created in a fracturing well. Temporary plugging materials are used to temporarily seal the opening of existing fractures. Subsequent fracturing opens new fractures. After the operation is completed, the temporary plugging agent degrades or dissolves and becomes ineffective, restoring the production capacity of the original old fractures and working together with the new fractures.

[0045] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0046] Finally, it should be noted that 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 should understand that modifications or equivalent substitutions can still be made 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 should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for sealing fractures in high water-cut oil well reservoirs, characterized in that, The method includes placing solid plugging particles that are compatible with the fluid in the oilfield well within a high water-cut fracturing pipeline. These solid plugging particles enter the high water-cut reservoir during fracturing operations, forming a water-controlling plugging agent. The water-controlling plugging agent adheres within the high water-cut reservoir, forming a bonding adhesive that attaches to the fractures within the high water-cut reservoir, sealing the fracturing fractures. The method for preparing the water-controlling plugging agent includes... Add a synergist to the liquid phase of the carrier liquid and stir until homogeneous to form an oil phase mixture; The prepared phase-inversion solid particles are uniformly dispersed into the oil phase mixture to form an oil-solid mixture; A crosslinking agent is added to the oil-solid mixture and stirred until homogeneous to form a water-controlling and plugging agent. The phase-inversion solid particles are ethylene-vinyl acetate copolymers; The solid particles are used based on the pore throat radius of the oil well. The pore throat radius is calculated as follows: R = (8K / φ)¹ / ⁴, where φ is the porosity and K is the permeability (μm). 2 ), R is the throat radius (μm); When the solid-phase plugging particles are installed in the high water-cut fracturing pipeline of an oilfield well, the content of the solid-phase plugging particles is determined according to the water content in the high water-cut reservoir. The water content in the reservoir is calculated as follows: C = K·h·△P1, where C is the addition concentration; K is the content ratio coefficient; △P1 is the unit breakthrough pressure; and h is the effective injection depth.

2. The method for sealing fractures in high water-cut oil well reservoirs according to claim 1, characterized in that, The density of the phase transition solid particles is 0.9 cm / m³. 3 -0.98cm / m 3 .

3. The method for sealing fractures in high water-cut oil well reservoirs according to claim 1, characterized in that, The crosslinking agent is vinyltrimethoxysilane, vinyltriethoxysilane, or γ-aminopropyltriethoxysilane.

4. The method for sealing fractures in high water-cut oil well reservoirs according to claim 1, characterized in that, The carrier fluid is diesel oil, white oil, or an oil-water emulsion of diesel oil or white oil mixed with water.

5. The method for sealing fractures in high water-cut oil well reservoirs according to claim 1, characterized in that, The synergist is polyoxyethylene octylphenol ether-10.

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