A pressure control and profile control method for ultra-low permeability reservoirs

Abstract

The application discloses a kind of ultra-low permeability reservoir pressure control profile control methods, comprising: obtaining oil well data, according to oil well data, calculate total liquid volume of profile control plug and each plug liquid volume;According to total liquid volume of profile control plug and each plug liquid volume, configure oil reservoir protection plug in pre-plug, main body plugging agent in main body plug and deblocking plug in post-plug;The prepared pre-plug, main body plug and post-plug are sequentially injected into formation, and after shut-in reaction, subsequent conventional injection and production operation is carried out.The present application can effectively protect the near-wellbore reservoir of ultra-low permeability reservoir by reasonable plug combination design, and provides an accurate calculation method for the main profile control plug, improving the pertinence and applicability of water plugging and profile control in ultra-low permeability reservoir.

Description

Technical Field

[0001] This invention belongs to the field of water shut-off and profile control in oilfields, and relates to a method for pressure control and profile control in ultra-low permeability reservoirs. Background Technology

[0002] In ultra-low permeability oilfields, the water cut of oil wells gradually increases with prolonged water injection. Water shut-off and displacement regulation in injection wells are among the main technical methods for controlling high water cut in oil wells. The dosage of displacement regulators in high-permeability oilfields is generally between 3000 and 5000 m³. 3 Between these values, the dosage of modifier in ultra-low permeability reservoirs is around 2000 m³. 3 Around 100°C, due to the high water injection pressure in ultra-low permeability reservoirs, water injection difficulties and the lack of targeted application of plugging agents are easily caused after the adjustment and flooding process.

[0003] The existing water shut-off and profile control technologies mainly include: (1) Chinese patent application CN201210026548.4, "Point-to-point placement of gel water shut-off and profile control agent and its application method", is a method of point-to-point placement of gel water shut-off and profile control agent. Different locations between oil and water wells are used as target points. The time for the fluid to reach these target points is calculated by the tracer travel time. Based on this time, gel formulations with different delayed cross-linking times are designed and injected sequentially. Different slugs have different gel strengths and cross-linking gelation times to achieve point-to-point placement. (2) Chinese patent application CN201811578358.7, "A selective foam gel water shut-off and profile control method for ultra-low permeability oilfields", is a profile control method that injects a selective foam gel water shut-off and profile control agent for ultra-low permeability oilfields, a composite modified resin cross-linked strong gel water shut-off and profile control agent, and a weak gel profile control agent. (3) Chinese patent application CN201210466088.7, entitled "A method for deep profile control in ultra-low permeability reservoirs", adopts a high-concentration weak gel plus a medium-concentration weak gel plus a particulate gel system, which is a profile control method that combines deep profile control and shallow profile control. The injection pressure should be designed according to the previous water injection pressure, and the injection speed is generally 2~5m. 3 / h. (4) Chinese patent application CN201610832339.7, “Deep-deployment method for profile control of plugging agent”, in which a low-filtration-loss pre-plugging fluid is injected into the formation at the water well end to form an artificial fracture for end-blocking. The artificial fracture is filled with a liquid-solid mixture, and plugging agent is injected into the water well. After solidification, the plugging agent system is solidified or gelled to achieve the purpose of deep plugging. (5) Chinese patent application CN201210015473.X, “A method for profile control of fractured reservoir”, in which a method for profile control is defined by a combination of polymer aqueous solution slug, slow-swelling salt-resistant high-strength water-absorbing resin particles, gel profile control agent suspension particles, and petroleum sulfonate surfactant.

[0004] The above-mentioned patents and methods mainly achieve profile control by combining profile control agents and according to a certain predicted position. In view of the poor profile control performance of ultra-low permeability reservoirs, no corresponding practical calculation methods are mentioned in the design of slugs: (1) the profile control process does not set up a near-wellbore zone protection slug; (2) there is no suitable calculation method for the main slug fluid volume; (3) the slugs placed after water shut-off profile control are not designed with corresponding treatment slugs, the near-wellbore zone is seriously contaminated by profile control agents, the water injection pressure rises too much, and water injection is difficult. Summary of the Invention

[0005] The purpose of this invention is to provide a pressure-controlled profile control method for ultra-low permeability reservoirs, thereby solving the problem that existing technologies are not very effective in controlling profiles for ultra-low permeability reservoirs.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for pressure control and profile modification in ultra-low permeability reservoirs includes: Acquire oil well data and calculate the total fluid volume of the profile control plugs and the fluid volume of each plug based on the oil well data; Based on the total fluid volume of the profile control slugs and the fluid volume of each slug, configure the oil layer protection slug in the front slug, the main plugging agent in the main slug, and the unblocking slug in the rear slug; The pre-configured pre-slug, main slug, and post-slug are sequentially injected into the formation. After the well is shut in and reacted, subsequent conventional injection and production operations are carried out.

[0007] Furthermore, the oil well data includes water cut of water-flooded oil wells, cumulative oil production, crude oil density of the block, water drive efficiency of the block, and initial water saturation of the profile control area.

[0008] Furthermore, the method for calculating the total fluid volume of the profile-adjusting plug is as follows: V 总液量 =V 前置 +V 主体 +V 解堵 Among them, V 总液量 V represents the total fluid volume of the profiled plug. 前置 V represents the fluid volume of the pre-slug stage. 主体 Indicates the main body plugging agent liquid volume, V 解堵 This indicates the fluid volume of the rear-stage plug.

[0009] Furthermore, the method for calculating the volume of the main plugging agent is as follows: V 主体 =

[0010] Where m represents the predicted cumulative oil production of the oil well corresponding to the profile control and water injection well. This indicates the crude oil density in ultra-low permeability reservoirs. This indicates the final water-drive oil recovery efficiency of the block. Indicates the water saturation of the original strata. It is represented as the PV coefficient of the main block.

[0011] Furthermore, the volume of the pre-plug fluid is 30-50m³. 3 The fluid volume of the post-slug is 30~40m³. 3 .

[0012] Furthermore, the oil layer protection slug in the pre-slug is a guar gum solution with a mass fraction of 3%.

[0013] Furthermore, the main plugging agent within the main plug is a PEG gel particle + gel solution system, a chromium glue combined plugging agent + gel particle system, or a composite plugging agent system.

[0014] Furthermore, the unblocking plug in the rear plug is a 0.3% ammonium persulfate solution.

[0015] Furthermore, it also includes the step of injecting the post-slug into the formation and then injecting active water to completely displace the post-slug into the formation.

[0016] Furthermore, the amount of activated water injected is twice the volume of the oil pipe.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for pressure control and profile modification in ultra-low permeability reservoirs. By using a pre-installed layer protection slug in a slug combination design, the water-drive swept volume edge of the oil layer and near-wellbore zone is protected, helping to maintain the long-term production capacity and stability of the reservoir. The amount of main plugging agent used in the water injection well for profile modification in ultra-low permeability reservoirs is calculated based on well production conditions, improving the targeting and efficiency of the main plugging agent application and ensuring maximum profile modification effect. Then, by using a post-installed unplugging slug, the problem of water-drive swept volume edge contamination in the oil layer and near-wellbore zone is resolved, protecting the oil layer and the near-wellbore zone of the water injection well. This controls the water injection pressure of the water injection well after profile modification, avoiding the problem of insufficient water injection in ultra-low permeability oilfields after profile modification, helping to restore the permeability of the oil layer, maintain the normal operation of the water injection well and the continuous development of the reservoir, and increase the production of the oil well. This invention, through a reasonable slug combination design, can effectively protect the near-wellbore reservoir of ultra-low permeability reservoirs, and proposes a precise calculation method for the main profile control slugs, improving the pertinence and applicability of water shut-off and water displacement in ultra-low permeability reservoirs, promoting the efficient development and long-term stable production of ultra-low permeability reservoirs, and has broad application prospects in the development of ultra-low permeability reservoirs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the ultra-low permeability reservoir pressure control and profile control method of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0024] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0025] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0026] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings: See Figure 1 This invention provides a method for pressure control and profile modification in ultra-low permeability reservoirs, specifically including the following steps: Step 1: Obtain oil well data and calculate the total fluid volume of the profile control plug and the fluid volume of each plug section based on the oil well data.

[0030] For well data related to pressure control and profile modification in ultra-low permeability reservoirs, the data includes water cut of water-flooded wells, cumulative oil production, block crude oil density, block water drive efficiency, and initial water saturation of the profile modification area. The predicted cumulative oil production of the water injection wells corresponding to the profile modification in this invention can be obtained using hyperbolic decline or other methods. For wells with a water cut greater than 98% corresponding to the profile modification, the current cumulative oil production can be used instead of the predicted cumulative production.

[0031] The total fluid volume of the profile control slugs is calculated based on the oil well data. Oil layer protection slugs are designed in the front slugs, and unblocking slugs are designed in the rear slugs to release the water absorption capacity of the near-wellbore zone. This achieves profile control of the injection well while improving subsequent water injection capacity and water drive sweep capacity.

[0032] The method for calculating the total fluid volume of the profiled plug is as follows: V 总液量 =V 前置 +V 主体 +V 解堵 Among them, V总液量 V represents the total fluid volume of the profiled plug. 前置 V represents the fluid volume of the pre-slug stage. 前置 The typical volumetric usage is 30~50m³. 3 V 主体 Indicates the main body plugging agent liquid volume, V 解堵 V represents the fluid volume of the rear slug. 解堵 The typical volumetric usage is 30~40m³. 3 .

[0033] The calculation method for the volume of the main plugging agent is as follows: V 主体 =

[0034] Where m represents the predicted cumulative oil production of the oil well corresponding to the profile control and water injection well, in tons (t); This indicates the density of crude oil in ultra-low permeability reservoirs, in t / m³. 3 ; This indicates the final water-drive oil recovery efficiency of the block; Indicates the water saturation of the original strata; It is represented as the PV coefficient of the main sluice gate, which is generally taken as 0.3.

[0035] Step 2: Based on the total fluid volume of the profile control slugs and the fluid volume of each slug, configure the oil layer protection slug in the front slug, the main plugging agent in the main slug, and the unblocking slug in the rear slug.

[0036] (1) Composition and function of the pre-stage slug The oil layer protection slug in the pre-slug of the present invention is composed of a 3% mass fraction low-concentration guar gum solution. In ultra-low permeability reservoirs with strong heterogeneity, the 3% mass fraction low-concentration guar gum solution serves as a pre-slug to protect the oil layer and the water drive sweep volume edge of the near-wellbore zone after injection, preventing the main plugging agent from entering the oil layer or the edge of the near-wellbore zone and causing contamination of the oil layer or the edge of the near-wellbore zone.

[0037] (2) Composition and function of the main block The main plugging agent in the main slug of this invention is a plugging agent system such as "PEG gel particles + gel solution", "chromium colloid plugging agent + gel particles", or "composite plugging agent". In the "PEG gel particles + gel solution" plugging agent system, PEG (polyethylene glycol) has good water solubility and good compatibility with many organic components. PEG gel particles improve the dispersibility and stability of the plugging agent, which helps to improve the physical and mechanical properties of the plugging agent. The gel solution can form a high-strength gel with good fluidity and selectivity, and can preferentially enter the water-flooded channel to form a stable water-blocking layer, which is used to seal the water flow channel in the formation, effectively preventing further water intrusion, thereby enhancing the water-blocking effect. In the "chromium colloid plugging agent + gel particles" plugging agent system, the chromium colloid plugging agent has good temperature and salt resistance, can maintain a stable water-blocking effect in high-temperature and high-salt formation environments, and can also react chemically with minerals in the formation to form a more robust sealing layer. Gel particles can fill pores and fractures in the formation, increasing the sealing strength and coverage of the plugging agent. They can also interact with chromium-based crosslinked plugging agents to form a denser sealing layer, improving water shut-off effectiveness. In the "composite plugging agent" system, different plugging agents can complement and synergistically interact to form a more complete water shut-off system. It can be customized and formulated according to different formation conditions and water shut-off requirements, significantly improving water shut-off efficiency and effectiveness, reducing backflow problems and formation damage during the water shut-off process, and further enhancing water shut-off effectiveness and economic benefits.

[0038] (3) Composition and function of the rear slug The unblocking slug in the post-slug of this invention is composed of a 0.3% ammonium persulfate solution. The unblocking slug has low viscosity and good penetration, enabling it to enter the oil layer and the edge of the near-wellbore water drive sweep volume effectively. It chemically unblocks the protective fluid of the pre-slug, protects the oil layer, releases water injection space in the near-wellbore zone, controls the water injection pressure of the injection well after profile modification, and avoids the problem of water not being able to be injected into ultra-low permeability oilfields after profile modification.

[0039] Step 3: Sequentially inject the configured pre-slug, main slug, and post-slug into the formation. After the well is shut in and reacts, proceed with subsequent conventional injection and production operations.

[0040] The pre-slug, main slug, and post-slug are sequentially injected into the formation using a profile control pump. The displacement fluid volume is then calculated based on twice the tubing volume, and active water displacement fluid is injected to completely displace the unblocking fluid into the formation. After injection, the well is shut in for 48 hours to allow for feedback. The profile control operation is then complete, and subsequent conventional injection and production operations can proceed.

[0041] The technical solution of the present invention will be further described in detail below through specific embodiments: Example 1: Taking a water injection well in a certain area of ​​an oilfield as an example, the water injection well has a tubing length of 1500m, corresponding to a water-flooded oil well with 100% water cut, and a cumulative oil production of 1005t. The crude oil density in this block is 0.85t / m³. 3 The development plan shows that the water flooding efficiency of the block is 55.3%, and the initial water saturation of the profile control area is 45.3%.

[0042] The volume of the main plugging agent is calculated using the method for calculating the volume of the main plugging agent: V 主体 = = =1173 (m) 3 ) The designed volume of the main plugging agent after rounding is 1200m³. 3 .

[0043] The total fluid volume of the profile control slug is calculated using the method for calculating the total fluid volume of the profile control slug. Therefore, the water shut-off and water displacement design for this well is as follows: the pre-slug fluid volume is 50m³. 3 The mass fraction is 3% guar gum solution + 1200m of main plugging agent. 3 PEG gel particles + gel solution plugging agent system + unblocking slug fluid 40ml 3 The mass fraction of ammonium persulfate solution is 0.3%. The displacement fluid volume is then calculated based on the tubing volume, and 9.1 m³ (twice the tubing volume) is injected. 3 Active water displacement solution.

[0044] The specific method for sequentially injecting the configured front slug, main slug, and rear slug into the formation is as follows: Step 1: Use the profile control pump to pump 50m of pre-plug fluid. 3 A 3% guar gum solution was injected into the formation from a water injection well. Step 2: Apply 1200m of the main plugging agent using a profile control pump. 3 The PEG gel particle + gel solution plugging agent system was injected into the formation; Step 3: Use a profile control pump to inject 40m³ of unblocking fluid into the sluice blockage. 3 A 0.3% ammonium persulfate solution was injected into the formation. Step 4: Use the profile control pump to pump the 9.1m... 3 The active water displacement fluid is injected into the formation to completely displace the unblocking fluid into the formation; Step 5: After shutting in the well for 48 hours, the profile control operation is completed.

[0045] Example 2: Taking a water injection well in a certain area of ​​an oilfield as an example, the water injection well has an oil pipe length of 1800m, corresponding to a water-flooded oil well with a water cut of 98%, and a cumulative oil production of 2100t. The crude oil density in this block is 0.85t / m³. 3The development plan shows that the water-drive oil efficiency of the block is 45.2%, and the initial water saturation of the profile control area is 35.2%.

[0046] The volume of the main plugging agent is calculated using the method for calculating the volume of the main plugging agent: V 主体 = = =2350 (m) 3 ) The main plugging agent volume is designed to be 2350m³. 3 .

[0047] The total fluid volume of the profile control slug is calculated using the method for calculating the total fluid volume of the profile control slug. Therefore, the water shut-off and water displacement design for this well is as follows: the pre-slug fluid volume is 50m³. 3 The mass fraction is 3% guar gum solution + 2350m of main plugging agent. 3 PEG gel particles + gel solution plugging agent system + unblocking slug fluid 40ml 3 The mass fraction of the solution is 0.3% ammonium persulfate. The displacement fluid volume is then calculated based on twice the tubing volume, and the injected active water displacement fluid volume is 10.8 m³. 3 .

[0048] The specific method for sequentially injecting the configured front slug, main slug, and rear slug into the formation is as follows: Step 1: Use the profile control pump to pump 50m of pre-plug fluid. 3 A 3% guar gum solution was injected into the formation from a water injection well. Step 2: Apply 2350m of the main plugging agent using a profile control pump. 3 The PEG gel particle + gel solution plugging agent system was injected into the formation; Step 3: Use a profile control pump to inject 40m³ of unblocking fluid into the sluice blockage. 3 A 0.3% ammonium persulfate solution was injected into the formation. Step 4: Use the profile control pump to pump the 10.8m... 3 The active water is injected into the formation to completely displace the unblocking fluid into the formation; Step 5: After shutting in the well for 48 hours, the profile control operation is completed.

[0049] Example 3: Taking a water injection well in a certain area of ​​an oilfield as an example, the well's tubing is 2150m long, corresponding to a water cut of 98.8% in a water-flooded well, with a cumulative oil production of 3520t. The crude oil density in this block is 0.84t / m³. 3 The development plan shows that the water flooding efficiency of the block is 43.3%, and the initial water saturation of the profile control area is 34.1%.

[0050] The volume of the main plugging agent is calculated using the method for calculating the volume of the main plugging agent: V 主体= = =4353 (m) 3 ) The designed volume of the main plugging agent after rounding is 4400 m³. 3 .

[0051] The total fluid volume of the profile control slug is calculated using the method for calculating the total fluid volume of the profile control slug. Therefore, the water shut-off and water displacement design for this well is as follows: the pre-slug fluid volume is 50m³. 3 The mass fraction is 3% guar gum solution + 4400m of main plugging agent. 3 Chromium-based plugging agent + gel particle plugging agent system + unblocking slug fluid 40ml 3 The mass fraction of ammonium persulfate solution is 0.3%. The displacement fluid volume is then calculated based on twice the tubing volume, and the injected active water displacement fluid volume is 13m³. 3 .

[0052] The specific method for sequentially injecting the configured front slug, main slug, and rear slug into the formation is as follows: Step 1: Use the profile control pump to pump 50m of pre-plug fluid. 3 A 3% guar gum solution was injected into the formation from a water injection well. Step 2: Apply 4400m of the main plugging agent using a profile control pump. 3 A chromium-based plugging agent + gel particle plugging agent system was injected into the formation; Step 3: Use a profile control pump to inject 40m³ of unblocking fluid into the sluice blockage. 3 A 0.3% ammonium persulfate solution was injected into the formation. Step 4: Use the profile control pump to pump 13m 3 The active water is injected into the formation to completely displace the unblocking fluid into the formation; Step 5: After shutting in the well for 48 hours, the profile control operation is completed.

[0053] Example 4: Taking a water injection well in a certain area of ​​an oilfield as an example, the water injection well has a tubing length of 1900m, corresponding to a water-flooded oil well with 100% water cut, and a cumulative oil production of 1834t. The crude oil density in this block is 0.82t / m³. 3 The development plan shows that the water flooding efficiency of the block is 61.3%, and the initial water saturation of the profile control area is 43.3%.

[0054] The volume of the main plugging agent is calculated using the method for calculating the volume of the main plugging agent: V 主体 = = =1930 (m) 3 ) The designed volume of the main plugging agent after rounding is 1900m³. 3 .

[0055] The total fluid volume of the profile control slug is calculated using the method for calculating the total fluid volume of the profile control slug. Therefore, the water shut-off and water displacement design for this well is as follows: the pre-slug fluid volume is 50m³. 3 The mass fraction is 3% guar gum solution + 1900m of main plugging agent. 3 The composite plugging agent system + 40ml of unblocking slug fluid 3 The mass fraction of the solution is 0.3% ammonium persulfate. The displacement fluid volume is then calculated based on twice the tubing volume, and the injected active water displacement fluid volume is 11.5 m³. 3 .

[0056] The specific method for sequentially injecting the configured front slug, main slug, and rear slug into the formation is as follows: Step 1: Use the profile control pump to pump 50m of pre-plug fluid. 3 A 3% guar gum solution was injected into the formation from a water injection well. Step 2: Apply 1900m of the main plugging agent using a profile control pump. 3 A composite plugging agent system was injected into the formation; Step 3: Use a profile control pump to inject 40m³ of unblocking fluid into the sluice blockage. 3 A 0.3% ammonium persulfate solution was injected into the formation. Step 4: Use the profile control pump to pump 11.5m 3 The active water is injected into the formation to completely displace the unblocking fluid into the formation; Step 5: After shutting in the well for 48 hours, the profile control operation is completed.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for pressure control and profile modification in ultra-low permeability reservoirs, characterized in that, include: Acquire oil well data and calculate the total fluid volume of the profile control plugs and the fluid volume of each plug based on the oil well data; Based on the total fluid volume of the profile control slugs and the fluid volume of each slug, configure the oil layer protection slug in the front slug, the main plugging agent in the main slug, and the unblocking slug in the rear slug; The pre-configured pre-slug, main slug, and post-slug are sequentially injected into the formation. After the well is shut in and reacted, subsequent conventional injection and production operations are carried out.

2. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 1, characterized in that, The oil well data includes water cut of water-flooded wells, cumulative oil production, crude oil density of the block, water drive efficiency of the block, and initial water saturation of the profile control area.

3. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 1, characterized in that, The method for calculating the total fluid volume of the profile-adjusting plug is as follows: V 总液量 =V 前置 +V 主体 +V 解堵 Among them, V 总液量 V represents the total fluid volume of the profiled plug. 前置 V represents the fluid volume of the pre-slug stage. 主体 Indicates the main body plugging agent liquid volume, V 解堵 This indicates the fluid volume of the rear-stage plug.

4. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 3, characterized in that, The method for calculating the volume of the main plugging agent is as follows: V 主体 = Where m represents the predicted cumulative oil production of the oil well corresponding to the profile control and water injection well. This indicates the crude oil density in ultra-low permeability reservoirs. This indicates the final water-drive oil recovery efficiency of the block. Indicates the water saturation of the original strata. It is represented as the PV coefficient of the main block.

5. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 3, characterized in that, The pre-block fluid volume is 30~50m. 3 The fluid volume of the post-slug is 30~40m³. 3 .

6. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 1, characterized in that, The oil layer protection slug in the pre-slug is a guar gum solution with a mass fraction of 3%.

7. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 1, characterized in that, The main plugging agent in the main block is a PEG gel particle + gel solution system, a chromium-based plugging agent + gel particle system, or a composite plugging agent system.

8. The method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 1, characterized in that, The unblocking slug in the post-positioned slug is a 0.3% ammonium persulfate solution.

9. A method for controlling pressure and profile control in ultra-low permeability reservoirs according to claim 1, characterized in that, It also includes the step of injecting the post-slug into the formation and then injecting active water to completely displace the post-slug into the formation.

10. A method for pressure control and profile modification in ultra-low permeability reservoirs according to claim 9, characterized in that, The amount of active water injected is twice the volume of the oil pipe.

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