Intelligent release self-assembly bridging particle adjusting and plugging system with high oil displacement effect

Abstract

The invention discloses an intelligent release self-assembly bridging particle profile control system with a high oil displacement effect, and relates to the technical field of recovery efficiency improvement. The problem that a traditional particle profile control and displacement technology is poor in injectability is solved, it is ensured that a system can be smoothly injected into a stratum through optimized injection parameters and particle structures, and the problem that injection pressure is too high is avoided; controllable plugging of the deep part of the oil reservoir is achieved, the intelligent release self-assembly particles can move to the deep part of the oil reservoir in a porous medium, stable plugging is formed through the softening and bonding effect of a covering film, and the period of validity reaches 12 months or above; by starting a low-permeability layer and plugging a fluid channeling channel of a high-permeability layer, remaining oil is effectively used, and the maximum increase amplitude of the recovery rate reaches 47.91%; the method is wide in application range and has good adaptability to heterogeneous oil reservoirs with the permeability level difference being 20 or below, and injection parameters can be adjusted within an optimization range according to actual oil reservoir conditions.

Description

Technical Field

[0001] This invention relates to the field of enhanced oil recovery technology, specifically to an intelligent release self-assembly bridging particle plugging system with high oil displacement effect. Background Technology

[0002] In the process of oil extraction, plugging agents improve the micro and macro displacement efficiency by changing the flow path of oil displacement agents in heterogeneous reservoirs, thereby effectively utilizing the remaining oil that could not be affected and achieving the goal of improving crude oil recovery.

[0003] However, commonly used plugging agents generally have drawbacks such as high injection pressure, weak plugging strength, and short effective period, resulting in poor plugging effect. They either fail to achieve effective plugging or are prone to failure after plugging, making it difficult to meet the needs of deep plugging in heterogeneous reservoirs and limiting the further improvement of oil recovery.

[0004] Therefore, developing a plugging system with good injection performance, strong controllability of plugging, and long effective period has become an urgent technical problem to be solved in the field of improving oil recovery. Summary of the Invention

[0005] The purpose of this invention is to provide an intelligent release self-assembly bridging particle plugging system with high oil displacement effect, which aims to solve the technical problems of existing plugging agents having high injection pressure, weak plugging strength, short effective period, and inability to achieve controllable plugging in deep reservoirs.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a smart release self-assembly bridging particle plugging system with high oil displacement effect, comprising smart release self-assembly particles, wherein the smart release self-assembly particles are composed of a core and a coating.

[0007] The core is a rigid sealing material;

[0008] The coating includes a rigid protective coating and a softening adhesive coating.

[0009] (1) Intelligent release of self-assembled particles

[0010] The intelligent release self-assembly particle is based on the bridging and plugging theory and consists of two main parts: a core and a coating.

[0011] Core: Rigid sealing material is used to provide stable skeleton support for bridge sealing;

[0012] The coating consists of two layers: an outer rigid protective coating and an inner softening adhesive coating. When the temperature reaches the softening point, the softening adhesive coating gradually softens, causing the particle plugging monomers to adhere to each other, thus strengthening the bridging and sealing stability of the core framework. At the same time, the softened coating can adhere to formation debris particles, achieving effective sealing of high-permeability layers.

[0013] (2) Optimization of injection parameters for the blockage control system

[0014] Through parallel sand-filled pipe model experiments, different reservoir permeability levels were simulated, and the following key injection parameters were optimized under saturated oil conditions:

[0015] Injection volume: 0.3PV is preferred, at which the recovery rate of the heterogeneous physical model is increased by 36.95%, and it has good adaptability to heterogeneous oil reservoirs with a permeability difference of 5. Effective oil displacement can be achieved in the range of 0.2PV to 0.4PV, with 0.3PV being the optimal value.

[0016] Particle concentration: 6% is preferred, as this can maximize the activation of low-permeability layers and increase the recovery rate by up to 40.54%. The particle concentration should be in the range of 3% to 9%. Too high a concentration will cause particles to accumulate at the sand pipe inlet, preventing them from migrating to deeper layers and reducing the oil displacement effect.

[0017] Injection timing: It is preferable to inject when the water content is below 85%, at which point the final recovery rate of the low-permeability layer reaches more than 70%; the earlier the injection timing, the more timely the blockage of the high-permeability layer flow channels can be blocked, the low-permeability layer can be activated in advance, and the overall recovery rate can be improved.

[0018] Applicable permeability gradient: Applicable to permeability gradients of 20 (20000 / 1000×10). -3 In formations with a permeability difference of less than μm², when the permeability difference exceeds 20, the low-permeability layer is difficult to start effectively, and the overall production rate decreases significantly.

[0019] Injection method: The injection method using polymer or guar gum suspension particles has a better oil displacement effect than starch suspension particles; when polymer suspension is injected, the overall recovery rate is increased by 40.52%, and the recovery rate of low-permeability layers is increased by 42.81%.

[0020] Slug combination: A combination of starch glue slugs and self-assembled granular slugs is injected, with the starch glue system injected first for better results. The starch glue system can pre-seal large channels and form a synergistic effect with the subsequent granular drive system to further improve the recovery rate. The combination of injecting starch glue first and then injecting the granular system improves the overall recovery rate by 47.91%.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. It solves the problem of poor injectability in traditional particle-based injection technology. The optimized injection parameters and particle structure ensure that the system can be successfully injected into the formation, avoiding the problem of excessive injection pressure.

[0023] 2. Achieve controllable plugging in deep reservoirs. Intelligent release of self-assembled particles can be transported to deep reservoirs in porous media, forming a stable plug through the softening and bonding effect of the coating, with an effective period of more than 12 months.

[0024] 3. Significantly improves crude oil recovery rate. By activating low-permeability layers and blocking the flow channels in high-permeability layers, the remaining oil is effectively utilized, with the recovery rate increasing by up to 47.91%.

[0025] 4. It has a wide range of applications and is well adapted to heterogeneous reservoirs with permeability differences of less than 20. Moreover, the injection parameters can be adjusted within the optimized range according to the actual reservoir conditions. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a parallel sand pipe model;

[0028] Figure 2 This is a flowchart of the oil displacement experiment.

[0029] Figure 3 A schematic diagram of the physical simulation curves to improve the recovery rate and injection volume;

[0030] Figure 4 A schematic diagram of the physical simulation curves to improve extraction rate and particle concentration;

[0031] Figure 5 A schematic diagram of physical simulation curves to improve recovery rate and water-bearing timing;

[0032] Figure 6 A schematic diagram of the physical simulation curve to improve the recovery rate and permeability gradient;

[0033] Figure 7 Statistical charts showing improved oil recovery rates under different injection methods;

[0034] Figure 8 Statistical charts showing improved oil recovery under different slug injection combinations. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] This invention, through indoor experimental research, determines the oil displacement effect of the intelligent release self-assembly bridging particle plugging system and defines the technical limits for specific applications.

[0037] This invention employs a parallel sand-filling model to simulate the actual permeability and gradient of an oil reservoir. Under saturated oil conditions, it evaluates the oil displacement effect of different particle concentrations, injection volumes, injection methods, injection timings, and chemical slug combinations, and optimizes injection parameters. Based on the experimental evaluation results, it analyzes the adaptability of the intelligent release self-assembly bridging particle deep plugging technology to reservoir permeability and gradient, and establishes basic criteria for reservoir screening.

[0038] Please see Figures 1-8 A smart release self-assembly bridging particle plugging system with high oil displacement effect includes smart release self-assembly particles, which are composed of a core and a coating.

[0039] The core is a rigid sealing material;

[0040] The coating includes a rigid protective coating and a softening adhesive coating;

[0041] The adhesive layer softens gradually when the temperature reaches the softening point range, and the particle plugging agent monomers adhere to each other under the action of the coating; making the bridging and sealing effect of the core skeleton more stable; in addition, the softened coating can also adhere to the debris particles, which can effectively block the high permeability layer.

[0042] The injection volume of the plugging system is 0.3 PV, the particle concentration is 6%, and the injection timing is before the water content reaches 85%. It is suitable for a permeability difference of 20, i.e., 20000 / 1000×10. -3 For formations with a diameter of less than μm², a polymer or guar gum suspension particle injection method is used. During injection, the starch gum system is injected first, followed by the intelligent release self-assembly particle system.

[0043] The injection volume of the intelligent release self-assembly bridging particle plugging system ranges from 0.2PV to 0.4PV.

[0044] The particle concentration range of the intelligent release self-assembly bridging particle blockage regulation system is 3% to 9%.

[0045] The water content range for the injection timing of the intelligent release self-assembly bridging particle plugging system is 75% to 85%.

[0046] The applicable range of permeability gradient for the intelligent release self-assembly bridging particle plugging system is 1~20, i.e., 1000 / 1000×10 -3 μm² to 20000 / 1000×10 -3 μm².

[0047] The intelligent release self-assembly bridging particle plugging system can perform slug combination;

[0048] The slug assembly is injected by combining a starch-based adhesive system with a smart-release self-assembling particle system.

[0049] The injection process of the slug combination includes injecting the starch glue system first and then the granular system, or injecting the starch glue slug and the granular slug alternately.

[0050] The optimal particulate plugging system has an injection volume of 0.3 PV, a particle concentration of 6%, and is injected when the water cut is below 85%. It is suitable for formations with a permeability gradient below 20. Injecting polymer or guar gum suspended particles yields better oil displacement than injecting starch suspended particles. However, using a combination of starch gum slugs and self-assembled particulate slugs can further improve the original recovery rate of the parallel sand pipe model, and injecting the starch gum system first is beneficial for improving the recovery rate.

[0051] Specifically as follows:

[0052] (1) Injection volume of particulate plugging agent system

[0053] The results above show that, under the experimental conditions, the optimal particulate plugging system with an injection volume of 0.3 PV can effectively improve the recovery rate of the heterogeneous physical model by 36.95%, indicating that the system has good applicability to heterogeneous oil reservoirs with a permeability difference of 5 when the injection volume is 0.3 PV.

[0054] (2) Particle concentration in the particulate blockage system

[0055] When the particle concentration of the selected particle plugging system is 6%, it can maximize the activation of low-permeability layers and improve the recovery rate of heterogeneous physical models by 40.54%. This indicates that the system has good applicability to heterogeneous oil layers with a permeability difference of 5 when the injection concentration is 6%.

[0056] At a particle concentration of 6%, the particulate plugging system exhibits good oil displacement performance. This is because the high particle concentration increases the number of bonded assemblies between particles, enabling the particulate plugging system to achieve stable bonding and bridging plugging capabilities. When the particle concentration is too high, the particles accumulate at the sand pipe inlet and cannot migrate effectively to the deeper parts of the sand pipe, thus significantly reducing the enhanced oil recovery effect.

[0057] (3) Timing of injection

[0058] The optimal injection timing for the selected granular plugging system is before the water cut reaches 85%. At this time, it can effectively activate the low-permeability layer and improve the overall production rate of the sand pipe. When the injection timing is before 85%, the final production rate of the low-permeability layer reaches over 70%; when the injection timing is after 85%, the final production rate of the low-permeability layer reaches between 60% and 70%. This indicates that the earlier the granular system is injected, the more beneficial it is for activating the low-permeability layer. This is because when the granular system is injected early, no large flow channels have been generated in the high-permeability layer. When the granular system is injected at this time, once flow channels are generated, they can be blocked. Therefore, the low-permeability layer can be activated earlier, improving its production rate and thus enhancing the overall production rate.

[0059] (4) Extremely poor permeability

[0060] When the permeability gradient is above 20, low-permeability layers cannot be effectively activated, resulting in low overall production. Therefore, under experimental conditions, the optimized particulate plugging agent system is suitable for formations with a permeability gradient below 20, but cannot effectively activate low-permeability layers in formations with a permeability gradient above 20.

[0061] (5) Injection method

[0062] Under experimental conditions, the injection method using polymer or guar gum suspension particles showed better oil displacement effect than the injection method using starch suspension particles.

[0063] Under experimental conditions, the injection method using a combination of starch glue slugs and self-assembled particle slugs can further improve the original recovery rate of the parallel sand tube model. Furthermore, the initial injection of the starch glue system is beneficial to improving the recovery rate. This is because the preferential injection of the starch glue system can block large channels to a certain extent and better synergize with the subsequently injected particle-driven system.

[0064] (6) Segment plug combination

[0065] The injection method employing a combination of starch-based slugs and self-assembled particle slugs can further improve the recovery rate of parallel sand tube models, with the initial injection of the starch-based system contributing to this improvement. This indicates that the preferential injection of the starch system can, to some extent, seal large channels and better synergize with the subsequently injected particle-based control system.

[0066] The following embodiments are then proposed:

[0067] Example 1: Optimal Injection Volume

[0068] Parallel sand pipe model was adopted (permeability 4000 / 20000×10). -3 μm 2With a permeability gradient of 5, water flooding was first performed until the water cut reached over 85%, followed by displacement with a 0.2% polymer solution and 6% suspended intelligent release self-assembled particles, and finally, subsequent water flooding was carried out. The oil displacement effect of the intelligent release self-assembled particle plugging system was investigated at different injection volumes (0.1PV, 0.2PV, 0.3PV, 0.4PV).

[0069] Results: During the injection of granular plugging agent, the overall recovery rate increased by 6.24% after injecting 0.10 PV of plugging agent, by 18.49% after injecting 0.2 PV, by 36.95% after injecting 0.3 PV, and by 40.77% after injecting 0.4 PV. With increasing plugging agent injection volume, the enhanced oil recovery performance of the granular plugging agent system showed an increasing trend, followed by a plateauing.

[0070] The results above show that, under the experimental conditions, the optimal particulate plugging system with an injection volume of 0.3 PV can effectively improve the recovery rate of the heterogeneous physical model by 36.95%, indicating that the system has good applicability to heterogeneous oil reservoirs with a permeability difference of 5 when the injection volume is 0.3 PV.

[0071] Example 2: Preferred Injection Concentration

[0072] Parallel sand pipe model was adopted (permeability 4000 / 20000×10). -3 μm 2 With a permeability gradient of 5, water flooding was first performed until the water cut reached over 85%, followed by displacement using self-assembled particles suspended in a 0.2% polymer solution (0%, 3%, 6%, 9%), and finally, subsequent water flooding was conducted. The oil displacement effect of the intelligent release self-assembled particle plugging system at different particle concentrations (0%, 3%, 6%, 9%) was investigated.

[0073] Results: Injecting a 0.2% concentration of pure polymer improved the overall recovery rate by 18.62%; injecting a 3% granular concentration plugging agent improved the overall recovery rate by 30.84%; injecting a 6% granular concentration plugging agent improved the overall recovery rate by 40.54%; and injecting a 9% granular concentration plugging agent improved the overall recovery rate by 14.03%. With increasing granular concentration, the enhanced oil recovery performance of the granular plugging agent system showed an increasing trend followed by a decreasing trend. At a granular concentration of 6%, low-permeability layers could be significantly activated, with recovery rates reaching 34.21%–52.35%.

[0074] The results above show that, under the experimental conditions, the optimal particle plugging agent system with a particle concentration of 6% can maximize the activation of low-permeability layers and improve the recovery rate of heterogeneous physical models by 40.54%. This indicates that the system has good applicability to heterogeneous oil layers with a permeability difference of 5 when the injection concentration is 6%.

[0075] Example 3: Optimal Timing of Water Injection

[0076] Parallel sand pipe model was adopted (permeability 20000 / 4000×10). -3 μm 2 With a permeability gradient of 5, water flooding was first performed to the specified water cut, followed by displacement using a 0.2% polymer solution + 6% suspended self-assembled particles, with an injection volume of 0.3 PV. Subsequent water flooding was then conducted. The oil displacement effect of the intelligent release self-assembled particle plugging system was investigated at different water cuts (75%, 80%, 85%, 90%, 95%).

[0077] Results: During the injection of particulate plugging agent, when the injection time was 75% water cut, the final recovery rate of the low-permeability layer reached 57.26%, and the overall recovery rate reached 71.36%; when the injection time was 80% water cut, the final recovery rate of the low-permeability layer reached 55.71%, and the overall recovery rate reached 73.97%; when the injection time was 85% water cut, the final recovery rate of the low-permeability layer reached 50.66%, and the overall recovery rate reached 77.22%; when the injection time was 90% water cut, the final recovery rate of the low-permeability layer reached 38.19%, and the overall recovery rate reached 65.49%; when the injection time was 95% water cut, the final recovery rate of the low-permeability layer reached 36.45%, and the overall recovery rate reached 62.90%. When the injection time was below 90%, the final recovery rate of the low-permeability layer reached over 60%; when the injection time was below 85%, the final recovery rate of the low-permeability layer reached between 50% and 60%.

[0078] Based on the above results, it can be seen that, under the experimental conditions, the optimal injection time for the granular plugging agent system is before the water cut reaches 85%. At this time, it can effectively activate the low-permeability layer and improve the overall production rate of the sand pipe.

[0079] Example 4: Optimal Permeability Gradient Selection

[0080] A parallel sand pipe model was adopted (where the permeability of the high-permeability layer is 20000×10). -3 μm 2 The design permeability gradients were 1, 5, 10, 15, 20, and 30%. Water flooding was first performed until the water cut reached over 85%. Then, a 0.2% polymer solution plus 6% suspended self-assembled particles was injected as displacement at a rate of 0.3 PV. Finally, subsequent water flooding was conducted. The permeability adaptability of the self-assembled particle system for oil displacement was investigated.

[0081] Results: The larger the permeability gradient, the worse the utilization of low-permeability layers during the waterflooding stage. When the permeability gradient is around 10, the recovery rate of low-permeability layers is 45.26%; when the permeability gradient is around 15, the recovery rate is 31.51%; when the permeability gradient is around 20, the recovery rate is only 11.52%; and when the permeability gradient reaches 30 or more, the low-permeability layers are almost impossible to activate. Therefore, when the permeability gradient is above 20, low-permeability layers cannot be effectively activated, resulting in a low overall permeability level.

[0082] Based on the above results, it can be seen that, under the experimental conditions, the optimized particulate plugging agent system is suitable for formations with permeability gradients below 20.

[0083] Example 5: Preferred Injection Method

[0084] Parallel sand pipe model was adopted (the designed permeability of the high-permeability layer was 20000×10⁻⁶). -3 μm 2 The permeability of the low-permeability layer is 4000×10 -3 μm 2 First, water flooding was performed until the water cut reached over 85%. Then, 6% self-assembled particles were suspended in different particle suspension systems for displacement, with an injection volume of 0.3 PV. Finally, subsequent water flooding was carried out. The effect of particle injection method on the oil displacement effect of the self-assembled particle system was investigated.

[0085] Results: During the granular plugging stage, the overall recovery rate increased by 29.37% after injecting starch-based granular plugging agents, with a 37.22% increase in low-permeability layers and a 21.52% increase in high-permeability layers; the overall recovery rate increased by 35.96% after injecting guar gum-based granular plugging agents, with a 39.84% increase in low-permeability layers and a 32.08% increase in high-permeability layers; and the overall recovery rate increased by 40.52% after injecting polymer-based granular plugging agents, with a 42.81% increase in low-permeability layers and a 38.23% increase in high-permeability layers.

[0086] The results above show that, under the experimental conditions, the injection method using polymer or guar gum suspension particles is more effective at displacing oil than the injection method using starch suspension particles.

[0087] Example 6: Preferred Segment Combination

[0088] Parallel sand pipe model was adopted (the designed permeability of the high-permeability layer was 20000×10⁻⁶). -3 μm 2 The permeability of the low-permeability layer is 4000×10 -3 μm 2First, water flooding is performed until the water cut reaches over 85%. Then, chemical plugging agents are injected using different slug combinations, followed by subsequent water flooding. The oil displacement effect of different slug combination systems is investigated.

[0089] Results: During the injection of granular plugging agents, the overall recovery rate of D1, which first injected the self-assembled granular system, increased by 41.35%, with a 44.36% increase in recovery rate for low-permeability layers and a 38.31% increase for high-permeability layers. The overall recovery rate of D2, which alternated between injecting the starch-based adhesive system and the self-assembled granular system, increased by 47.37%, with a 51.17% increase in recovery rate for low-permeability layers and a 43.47% increase for high-permeability layers. The overall recovery rate of D3, which first injected the starch-based adhesive system, increased by 47.91%, with a 57.66% increase in recovery rate for low-permeability layers and a 38.03% increase for high-permeability layers.

[0090] In summary, the results show that, under the experimental conditions, the injection method using a combination of starch slug plugs and self-assembled granular slug plugs can further improve the original recovery rate of the parallel sand tube model, and injecting the starch slug system first is beneficial to improving the recovery rate.

[0091] This invention clarifies the application technology boundaries of the system, optimizes injection parameters, establishes reservoir screening standards, and realizes the efficient utilization of residual oil in heterogeneous reservoirs.

[0092] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A smart release self-assembly bridging particle plugging system with high oil displacement effect, characterized in that: This includes smart release self-assembly particles, which consist of a core and a coating. The core is a rigid sealing material; The coating includes a protective rigid coating and an adhesive softening coating; The adhesive layer softens gradually when the temperature reaches the softening point range, and the particle plugging monomers adhere to each other under the action of the coating; making the bridging and sealing effect of the core skeleton more stable; in addition, the softened coating can also adhere to the debris particles.

2. The intelligent release self-assembly bridging particle plugging system with high oil displacement effect according to claim 1, characterized in that: The injection volume of the intelligent release self-assembly bridging particle plugging system ranges from 0.2PV to 0.4PV.

3. The intelligent release self-assembly bridging particle plugging system with high oil displacement effect according to claim 1, characterized in that: The particle concentration range of the intelligent release self-assembly bridging particle regulating system is 3% to 9%.

4. The intelligent release self-assembly bridging particle plugging system with high oil displacement effect according to claim 1, characterized in that: The moisture content range for the injection timing of the intelligent release self-assembly bridging particle plugging system is 75% to 85%.

5. The intelligent release self-assembly bridging particle plugging system with high oil displacement effect according to claim 1, characterized in that: The applicable range of the permeability gradient of the intelligent release self-assembly bridging particle plugging system is 1~20, i.e., 1000 / 1000×10 -3 μm² to 20000 / 1000×10 -3 μm².

6. The intelligent release self-assembly bridging particle plugging system with high oil displacement effect according to claim 1, characterized in that: The intelligent release self-assembly bridging particle plugging system can perform segment plug combination; The slug assembly is injected by combining a starch glue system with a smart release self-assembly particle system. The injection process of the slug combination includes injecting the starch glue system first and then the granular system, or injecting the starch glue slug and the granular slug alternately.

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