A method for profile control of a water injection well

Abstract

The present application relates to the field of petroleum engineering, and provide a kind of water injection well profile control method, method includes: determining the optimal polymer gel matched with the formation of water injection well site;Determine the corresponding gel strength of optimal polymer gel of different concentrations, and based on the gel strength, the optimal polymer gel of different concentrations is divided into multiple intensity grades;Determine the multi-section profile control agent plug structure of different intensity grade combination;Calculate the injection amount of each section in the multi-section profile control agent plug structure;Based on the intensity grade of each section and the injection amount of each section, the optimal polymer gel of corresponding concentration is injected into each section to profile control water injection well.The present application does not need to carry out acid liquid optimization and acid liquid compatibility experiment with target formation matching step in advance, and injection equipment uses conventional equipment, and does not necessarily resist acid, reduces the workload and preparation period of early experiment, reduces construction requirements and input cost, and is beneficial to improve water injection profile control efficiency.

Description

Technical Field

[0001] This invention relates to the field of petroleum engineering, and more particularly to a method for profile control in water injection wells. Background Technology

[0002] Profile adjustment, also known as reservoir profile adjustment, is an important technical means for water injection development of oilfields. As water injection development progresses, due to objective reasons such as water quality and multiple rounds of profile adjustment, the water injection pressure of some injection wells gradually increases, accompanied by increasingly intensified inter-layer, intra-layer, and planar contradictions. Profile adjustment of injection wells is carried out to further improve the effect of water injection development.

[0003] Existing methods for profile control in water injection wells, such as the integrated acidizing and profile control method described in patent number CN20131021940.4, involve screening high-pressure water injection wells, first performing acidizing treatment to dissolve near-wellbore contamination and reduce injection pressure, and then performing profile control to seal deep high-permeability zones in the formation. This requires preliminary steps such as selecting the optimal acid and profile control agent to match the target formation, as well as conducting compatibility tests between the acid and the agent. Furthermore, the injection equipment used in the field must be acid-resistant. This method is only suitable for high-pressure water injection wells with near-wellbore contamination and is difficult to apply to profile control of water injection wells with narrow pressure windows. Additionally, the entire process involves a large amount of experimental work, a long preparation period, and relatively high construction requirements and costs, reducing the efficiency of water injection well profile control.

[0004] Therefore, existing technologies urgently need to be improved. Summary of the Invention

[0005] To address the problem that existing integrated acidizing and profile control methods are difficult to apply to profile control of injection wells with narrow pressure windows, and that the entire process involves a large amount of experimental work, a long preparation period, and relatively high construction requirements and costs, thus reducing the efficiency of profile control in injection wells, this invention proposes a method for profile control of injection wells that solves at least one of the above problems.

[0006] To achieve the above objectives, one aspect of the present invention provides a method for profile control of a water injection well, comprising: Determine the optimal polymer gel that matches the formation where the injection well is located; Determine the gelation strength corresponding to the optimal polymer gel at different concentrations, and based on the gelation strength, classify the optimal polymer gel at different concentrations into multiple strength levels; Determine the multi-segment profile control agent slug structure with different strength grade combinations; Calculate the injection volume of each segment in a multi-segment profile control agent slug structure; Based on the strength level and injection volume of each segment, the optimal concentration of polymer gel is injected into each segment to adjust the profile of the injection well.

[0007] In some embodiments, the step of determining the optimal polymer gel that matches the formation where the injection well is located includes: Multiple candidate polymer gels were identified; Based on the gelation properties of multiple candidate polymer gels at the same concentration under the same oil reservoir temperature in the water injection well, the optimal polymer gel matching the formation where the water injection well is located is determined.

[0008] In some embodiments, the step of determining the optimal polymer gel matching the formation of the water injection well based on the gelation properties of multiple candidate polymer gels at the same concentration under the same reservoir temperature in the water injection well includes: Based on the gelation time, gelation strength, and stability parameters of multiple candidate polymer gels at the same concentration and the same oil layer temperature in the water injection well, the optimal polymer gel matching the formation of the water injection well is determined.

[0009] In some embodiments, the step of classifying optimal polymer gels of different concentrations into multiple strength levels based on gel strength includes: Based on the gelation strength corresponding to the optimal polymer gel at different concentrations within a preset concentration range, multiple gelation strength ranges are defined. Based on the defined range of gelation strength, multiple strength grades are determined, along with the optimal polymer gel concentration for each strength grade.

[0010] In some embodiments, the step of classifying optimal polymer gels of different concentrations into multiple strength levels based on gel strength includes: Based on the gelation strength corresponding to the optimal polymer gel at different concentrations within a preset concentration range, the first gelation strength range and the second gelation strength range are divided. The first strength grade and the second strength grade are determined according to the first and second gel strength ranges, and the gel strength in the first gel strength range is less than the gel strength in the second gel strength range. Based on the first gel strength range and the second gel strength range, determine the optimal polymer gel of the first concentration and the optimal polymer gel of the second concentration corresponding to the first strength level and the second strength level.

[0011] In some embodiments, the step of determining the multi-segment profile control slug structure with different strength grade combinations includes: Determine the target intensity level combination; Based on the target strength level combination, determine the number of segments in the multi-segment profile control agent slug structure and the optimal polymer gel concentration corresponding to each segment.

[0012] In some embodiments, the step of determining the target intensity level combination includes: Based on the first and second strength levels, a multi-segment profile control agent slug structure with multiple strength levels is constructed. The target strength level combination is determined based on the rise in profile control pressure corresponding to each multi-segment profile control agent slug structure under the same injection volume conditions.

[0013] In some embodiments, the step of determining the target strength grade combination based on the profile control pressure rise corresponding to each multi-segment profile control agent slug structure under the same injection volume condition includes: Based on the principle that the pressure rise of the multi-segment profile control agent slug structure is the smallest under the same injection volume conditions, the combination of first strength grade - second strength grade - first strength grade is determined as the target strength grade combination.

[0014] In some embodiments, the step of determining the number of segments in the multi-segment profiling agent slug structure and the optimal polymer gel concentration corresponding to each segment based on the target strength level combination includes: Based on the combination of the first strength level, the second strength level, and the first strength level, the first to third segments in the multi-segment profiling agent slug structure obtained in the order of injection are determined, and the optimal polymer gel with the first to third segments at the first, second, and first concentrations is determined.

[0015] In some embodiments, the step of determining the number of segments in the multi-segment profile control slug structure and the optimal polymer gel concentration corresponding to each segment based on the target strength level combination further includes: The fourth segment of the multi-segment profile control slug structure, which is the last segment injected according to the injection sequence, is injected with water or a polymer solution.

[0016] In some embodiments, the step of calculating the injection volume of each segment in the multi-segment profile control agent slug structure includes: Calculate the total amount of profile control agent to be injected into the injection well; The injection volume of each segment is determined based on the calculated total amount of profile control agent injected and the number of segments. Specifically, the injection volumes of the first to third segments are determined to account for 1 / 6 to 1 / 4, 1 / 2 to 2 / 3, and 1 / 6 to 1 / 4 of the total amount of profile control agent injected, respectively. The injection volume of the fourth segment is the sum of the wellbore volume of the injection well and the pore volume of the formation.

[0017] In some embodiments, the step of calculating the total amount of profile control agent to be injected into the injection well includes: The total amount of profile control agent to be injected into the water injection well is calculated using a volumetric formula based on the radius of the corresponding profile control well, the thickness and porosity of the target layer, and the sweep efficiency of the profile control agent injected into the water injection well.

[0018] In some embodiments, the step of injecting an optimal concentration of polymer gel into each segment based on the strength level and injection volume of each segment to modulate the profile of the injection well includes: Based on the injection volume and strength level corresponding to the first to fourth segments of the multi-segment profiling agent slug structure, the optimal polymer gel corresponding to the first strength level-second strength level-first strength level is injected into the first to third segments respectively, and water or polymer solution is injected into the fourth segment.

[0019] This invention offers at least the following advantages: It proposes a method for profile control in water injection wells. The method involves determining the optimal polymer gel that matches the formation of the water injection well, then determining the gelation strength corresponding to different concentrations of the optimal polymer gel and classifying these strengths into multiple strength levels. A multi-segment profile control slug structure with different strength level combinations is then determined, and the injection volume of each segment in the multi-segment slug structure is calculated. Based on the strength level of each segment and its corresponding injection volume, the optimal polymer gel of the corresponding concentration is injected into each segment for profile control. This method, by determining the optimal polymer gel and different strength levels based on the gelation strength range corresponding to its different concentrations, designs a multi-segment profile control slug structure based on combinations of different strength levels and injects it into the water injection well for profile control. This eliminates the need for prior acid selection to match the target formation and compatibility tests between the acid and the profile control agent. Furthermore, conventional injection equipment is sufficient, and acid resistance is not required. This reduces the workload and preparation period for preliminary experiments, lowers construction requirements and investment costs, and improves the efficiency of water injection profile control. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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 embodiments can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart of a method for profile control of a water injection well provided in the first embodiment of the present invention; Figure 2 This is a flowchart of profile control for a narrow pressure window well, provided as a second embodiment of the present invention. Detailed Implementation

[0022] The following describes embodiments of the present invention. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms.

[0023] Furthermore, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements may include not only those elements but also elements not expressly listed or inherent to such process, method, article, or apparatus.

[0024] One or more embodiments of this application will now be described with reference to the accompanying drawings.

[0025] Based on the above objectives, this invention proposes a method for profile control of water injection wells. Figure 1 The flowchart shown is a method for profile control of a water injection well according to an embodiment of the present invention. Figure 1 As shown, a method for profile control of a water injection well includes: Step 101: Determine the optimal polymer gel that matches the formation where the injection well is located; Step 102: Determine the gelation strength corresponding to the optimal polymer gel at different concentrations, and based on the gelation strength, classify the optimal polymer gel at different concentrations into multiple strength levels; Step 103: Determine the multi-segment profile control agent slug structure with different strength grade combinations; Step 104: Calculate the injection volume of each segment in the multi-segment profile control agent slug structure; Step 105: Based on the strength level and injection volume of each segment, inject the optimal polymer gel of corresponding concentration into each segment to adjust the profile of the injection well.

[0026] The above-mentioned method for profile control in water injection wells determines the optimal polymer gel and different strength grades based on the gel strength range corresponding to its different concentrations. It designs a multi-segment profile control agent slug structure based on combinations of different strength grades and injects it into the water injection well for profile control. This eliminates the need for preliminary steps such as acid selection to match the target formation and compatibility tests between the acid and the profile control agent. Furthermore, conventional equipment can be used for injection, and acid resistance is not required. This reduces the amount of preliminary experimental work and preparation period, lowers construction requirements and investment costs, and helps improve the efficiency of water injection profile control.

[0027] According to several embodiments of the present invention, the step of determining the optimal polymer gel matching the formation where the injection well is located includes: determining a plurality of candidate polymer gels; and determining the optimal polymer gel matching the formation where the injection well is located based on the gelation properties of the plurality of candidate polymer gels at the same concentration under the same oil reservoir temperature. Determining the optimal polymer gel matching the formation where the injection well is located based on a unified standard allows for better adaptation to formation conditions, enabling targeted sealing of high-permeability layers or water-dominant channels.

[0028] According to several embodiments of the present invention, the step of determining the optimal polymer gel matching the formation of the water injection well based on the gelation properties of multiple candidate polymer gels at the same concentration under the same oil layer temperature in the water injection well includes: determining the optimal polymer gel matching the formation of the water injection well based on the gelation time, gelation strength, and stability parameters of multiple candidate polymer gels at the same concentration under the same oil layer temperature in the water injection well. The optimal polymer gel is determined based on three aspects: gelation time, gelation strength, and stability, ensuring that the selected optimal polymer gel maintains a relatively good level in terms of gelation time, gelation strength, and gelation stability, thereby further improving the profile control effect. Specifically, candidate polymer gels are pre-determined; for example, a polymer gel with a concentration of 0.4% is considered. The candidate polymer gels are required to meet the following requirements: a gelation time of 12–120 h, a gelation strength greater than or equal to 20,000 mPa·s, and a gel retention rate greater than or equal to 60% within 30 days.

[0029] According to several embodiments of the present invention, the step of dividing optimal polymer gels of different concentrations into multiple strength levels based on gelation strength includes: dividing multiple gelation strength ranges according to the gelation strength corresponding to optimal polymer gels of different concentrations within a preset concentration range; determining multiple strength levels corresponding to the divided multiple gelation strength ranges, and the optimal polymer gel concentration corresponding to each strength level. Dividing the optimal polymer gels of different concentrations within a preset concentration range into multiple gelation strength ranges determines the corresponding multiple strength levels and the concentrations of the optimal polymer gels corresponding to them. Based on the correspondence between the concentration of the optimal polymer gel and the corresponding strength level, different multi-segment profiling plug structures can be subsequently constructed based on different strength levels.

[0030] According to several embodiments of the present invention, the step of dividing optimal polymer gels of different concentrations into multiple strength levels based on gelation strength includes: dividing a first gelation strength range and a second gelation strength range according to the gelation strength corresponding to the optimal polymer gels of different concentrations within a preset concentration range; determining a first strength level and a second strength level according to the divided first and second gelation strength ranges, wherein the gelation strength within the first gelation strength range is less than the gelation strength within the second gelation strength range; and determining the optimal polymer gel of a first concentration and the optimal polymer gel of a second concentration corresponding to the first and second strength levels according to the first and second gelation strength ranges. Determining the optimal polymer gel of a first and second concentration corresponding to the first and second strength levels based on the polymer gelation strength ranges corresponding to the first and second strength levels allows for the acquisition of multiple multi-segment profile control slugs with different strength level combinations, which is beneficial for subsequently selecting the multi-segment profile control slug with the smallest pressure rise during profile control as the final multi-segment profile control slug for profile control.

[0031] According to several embodiments of the present invention, the step of determining a multi-segment profile control agent slug structure with different strength level combinations includes: determining a target strength level combination; and determining the number of segments in the multi-segment profile control agent slug structure and the optimal polymer gel concentration corresponding to each segment based on the target strength level combination. The multi-segment profile control agent slug structure obtained based on the target strength level combination exhibits the smallest pressure rise during profile control. By controlling the concentration and injection volume of polymer gel in each segment of the multi-segment profile control agent slug, the sealing pressure can be controlled to be relatively low while effectively sealing deep high-permeability zones in the reservoir, making it suitable for profile control wells with narrow pressure windows.

[0032] According to several embodiments of the present invention, the step of determining a target strength level combination includes: constructing a multi-segment profile control agent slug structure with multiple strength level combinations based on a first strength level and a second strength level; and determining the target strength level combination based on the profile control pressure rise corresponding to each multi-segment profile control agent slug structure under the same injection volume condition. Accurately determining the target strength level combination can avoid unnecessary over-injection. Without optimization based on pressure rise, excessive profile control agent may be injected, increasing costs. By scientifically determining the combination, the amount of profile control agent used can be reduced while ensuring the profile control effect, thus lowering costs.

[0033] According to several embodiments of the present invention, the step of determining the target strength level combination based on the pressure rise of each multi-segment profile control agent slug structure under the same injection volume condition includes: determining a first strength level-second strength level-first strength level combination as the target strength level combination based on the minimum pressure rise amplitude of the multi-segment profile control agent slug structure under the same injection volume condition. Profile control of injection wells is performed based on the multi-segment profile control agent slugs corresponding to the first strength level-second strength level-first strength level combination. This first strength level-second strength level-first strength level combination allows the profile control agent to play different roles at different stages, and this combination method has the best profile control effect for wells with narrow pressure windows.

[0034] According to several embodiments of the present invention, the step of determining the number of segments in a multi-segment profile control agent slug structure and the optimal polymer gel concentration corresponding to each segment based on a target strength level combination includes: determining the first to third segments in the multi-segment profile control agent slug structure obtained in the injection sequence based on the first strength level-second strength level-first strength level combination, and determining the optimal polymer gel concentration corresponding to the first to third segments at the first-second-first concentration-first concentration. By controlling the concentration and injection volume of the polymer gel in each segment of the multi-segment profile control agent slug corresponding to the first-second-first strength level, the sealing pressure can be avoided while effectively sealing deep high-permeability zones in the reservoir.

[0035] According to several embodiments of the present invention, the step of determining the number of segments in a multi-segment profile control agent slug structure and the optimal polymer gel concentration corresponding to each segment based on a target strength level combination further includes: determining the fourth segment of the multi-segment profile control agent slug structure to be injected last according to the injection sequence, wherein water or a polymer solution is injected into the fourth segment. Injecting water or a polymer solution can improve the distribution of the profile control agent in the reservoir. During profile control, the profile control agent may exhibit uneven distribution; injecting water or a polymer solution can promote further diffusion and uniform distribution of the profile control agent, improving the stability and reliability of the profile control effect.

[0036] According to several embodiments of the present invention, the step of calculating the injection volume of each segment in a multi-segment profile control agent slug structure includes: calculating the total amount of profile control agent to be injected into the injection well; determining the injection volume of each segment based on the calculated total amount of profile control agent and the number of segments, wherein the injection volumes of the first to third segments are determined to account for 1 / 6 to 1 / 4, 1 / 2 to 2 / 3, and 1 / 6 to 1 / 4 of the total amount of profile control agent injected, respectively, and the injection volume of the fourth segment is the sum of the wellbore volume and the formation pore volume. The first segment is injected into the formation first, serving as the leading slug of the multi-segment profile control agent slug, which helps to ensure the sealing effect of the second end. The second segment is used to seal the high-permeability zone in the deep part of the formation, the third segment is used to seal the high-permeability zone near the well, and the fourth segment serves as a replacement slug to further ensure the effective sealing of the multi-segment profile control agent slug.

[0037] According to several embodiments of the present invention, the step of calculating the total amount of profile control agent injected into the injection well includes: calculating the total amount of profile control agent injected into the injection well using a volumetric method formula constructed based on the radius of the corresponding profile control layer, the thickness and porosity of the target layer, and the sweep efficiency of the profile control agent injected into the injection well. Calculating the total amount of profile control agent injected into the injection well using the volumetric method formula is simple, and the specific parameter values ​​of each physical quantity are easily obtained, which is beneficial for subsequent accurate calculation of the injection volume corresponding to each segment, enabling effective plugging.

[0038] According to several embodiments of the present invention, the step of injecting an optimal concentration of polymer gel corresponding to each segment into each segment for profile control of a water injection well, based on the strength grade and injection volume of each segment, includes: injecting optimal polymer gel corresponding to the first strength grade-second strength grade-first strength grade into the first to third segments respectively, based on the injection volume and strength grade of the first to fourth segments of the multi-segment profile control agent slug structure, and injecting water or polymer solution into the fourth segment. By accurately determining the injection volume corresponding to each segment, the high-permeability zone in the middle and deep parts of the formation and the high-permeability zone near the wellbore are effectively sealed, while avoiding excessive near-wellhead sealing pressure, making it suitable for profile control wells with narrow pressure windows. The water or polymer solution injected into the fourth segment acts as a replacement slug for the multi-segment profile control agent slug. The profile control effect can be judged by monitoring changes in wellhead pressure, and the profile control agent can also be more evenly distributed in the formation.

[0039] Statistical analysis of historical water injection well profile control shows that the pressure rise during profile control operations is generally above 2 MPa. Therefore, for those skilled in the art, a narrow pressure window profile control well generally refers to a profile control well (the water injection well undergoing profile control) where the difference between the main water injection line pressure and the normal water injection pressure is less than or equal to 2 MPa. Narrow pressure window profile control wells require both sealing high-permeability zones between wells and controlling the pressure rise during construction. Ensuring the profile control effect while maintaining normal water injection later presents significant design and construction challenges. Therefore, the difficulty in profile control for narrow pressure window wells lies in effectively sealing the deep high-permeability zones in the reservoir while maintaining a low sealing pressure. Sealing the near-wellbore area has a significant impact on the overall pressure, so it is crucial to minimize the near-wellbore sealing pressure. However, existing integrated acidizing and profile control methods for high-pressure water injection wells caused by near-wellbore contamination result in high near-wellbore sealing pressures, making it difficult to meet the dual requirements of effectively sealing the deep high-permeability zones in the reservoir while controlling the pressure rise during construction. To further understand the method for profile adjustment of injection wells according to the present invention, the following detailed explanation is based on the method proposed in this invention, using a narrow pressure window well as an example. Please refer to the following for details. Figure 2 .

[0040] To address the pressure difference requirement within a narrow pressure window, profile control wells with narrow pressure windows are selected. The trunk pressure and normal injection pressure of the profile control wells to be treated are statistically analyzed, and the difference between the trunk pressure and the normal injection pressure is calculated. Profile control wells with a difference of no more than 2 MPa are selected as the narrow pressure window profile control wells selected in this implementation.

[0041] Polymer gel systems exhibit low initial viscosity, and the gelation strength of the same polymer gel system varies significantly at different concentrations. Compared to acidizing methods, polymer gel-based profile control methods offer better adaptability, meeting the requirements of effectively sealing deep, high-permeability zones in wells with narrow pressure windows while maintaining relatively low sealing pressure. In practical applications, different polymer gels are commonly used for different target formations, and their corresponding gelation properties also vary.

[0042] First, the optimal polymer gel matching the formation of the injection well is determined. Commonly used polymer gels for this injection well formation are collected first. Several candidate polymer gels are then selected from these commonly used gels. The concentration of the polymer gels is generally 0.2%–0.5%. Based on the gelation time of a 0.4% polymer gel at the same reservoir temperature in this injection well (12–120 h), gel strength ≥20000 mPa·s, and 30-day gel strength retention rate ≥60%, several candidate polymer gels are selected. Then, these selected candidate polymer gels are combined at the same concentration, for example, 0.3%, and the optimal polymer gel matching the formation of this injection well is determined based on the optimal gelation time, gel strength, and stability parameters at the same reservoir temperature.

[0043] The optimal gel strength corresponding to different concentrations of polymer gel was determined, and based on the gel strength, the optimal polymer gels at different concentrations were divided into multiple strength grades. Specifically, based on the gel strength corresponding to different concentrations of the optimal polymer gel with a concentration range of 0.2~0.5%, a first strength grade and a second strength grade were defined, where: First strength grade (low strength grade): 5000 mPa·s ≤ gel strength < 10000 mPa·s; Second strength grade (medium strength grade): 10000 mPa·s ≤ gel strength ≤ 25000 mPa·s; High strength grade: gel strength > 25000 mPa·s. Based on the optimal polymer gel selected in the previous step, the optimal polymer gel of the first concentration corresponding to the first strength grade and the optimal polymer gel of the second concentration corresponding to the second strength grade were determined. For example, if the optimal polymer gel is polymer gel A, and polymer gel A has a gel strength of 8000 mPa·s at a concentration of 0.3%, 20000 mPa·s at a concentration of 0.4%, and 30000 mPa·s at a concentration of 0.5%, then the low strength grade corresponds to polymer gel A at a concentration of 0.3%, and the medium strength grade corresponds to polymer gel A at a concentration of 0.4%. As another example, if the optimal polymer gel is polymer gel B, and polymer gel B has a gel strength of 6000 mPa·s at a concentration of 0.2%, 14000 mPa·s at a concentration of 0.3%, 26000 mPa·s at a concentration of 0.4%, and 35000 mPa·s at a concentration of 0.5%, then the low strength grade corresponds to polymer gel B at a concentration of 0.2%, and the medium strength grade corresponds to polymer gel B at a concentration of 0.3%. Understandably, if the same polymer gel at different concentrations corresponds to the same strength grade, then the polymer gel at the lower concentration should be selected to match the strength grade in order to save resources and reduce costs.

[0044] Next, the multi-segment profile control agent slug structures with different strength level combinations were determined. Based on the defined first and second strength levels, multiple strength level combinations of multi-segment profile control agent slug structures were constructed. The pressure rise corresponding to the same injection volume was examined. Based on the fact that the multi-segment profile control agent slug structure had the smallest pressure rise under the same injection volume, the first strength level-second strength level-first strength level (low-medium-low strength level) combination was determined. Following the injection sequence of the profile control agent slugs, the first segment injected into the formation was designated as the first segment, followed by the second, third, and fourth segments. The multi-segment profile control agent slugs were set to correspond to the low-medium-low strength levels. Based on the optimal polymer gel concentration corresponding to the low strength level (first concentration) and the optimal polymer gel concentration corresponding to the medium strength level (second concentration), the optimal polymer gel concentration of the first concentration was injected into the first segment, the optimal polymer gel concentration of the second concentration was injected into the second segment, the optimal polymer gel concentration of the first concentration was injected into the third segment, and finally water or a polymer solution was injected into the fourth segment.

[0045] The injection volume of each segment in the multi-segment profile control agent slug structure is calculated. Based on the calculated total injection volume of profile control agent and the number of segments in the multi-segment profile control agent slug, the injection volume of each segment is determined. Then, based on the strength level of each segment, the optimal polymer gel of the first or second concentration is injected into each segment for profile control. Specifically, a volumetric method formula is constructed based on the radius of the injection well corresponding to the profile control, the thickness and porosity of the target layer, and the sweep efficiency of the profile control agent injection in the injection well. The total amount of profile control agent injected into the injection well is calculated using the volumetric method formula, as follows: V=πR 2 HΦγ (Formula 1) Where V is the total amount of profile control agent injected (m 3 R is the profile control radius (m), H is the thickness of the target layer (m), Φ is the porosity of the target layer (%), and γ is the sweep efficiency of the profile control agent injection (taken as 0.25~1.0).

[0046] Based on the number of segments in the multi-segment profile control agent slug, the calculated total amount of profile control agent, and the strength level corresponding to each segment, the optimal polymer gel of the first concentration is injected into the first segment, with an injection volume of 1 / 6 to 1 / 4 of the total profile control agent injection volume; the optimal polymer gel of the second concentration is injected into the second segment, with an injection volume of 1 / 2 to 2 / 3 of the total profile control agent injection volume; the optimal polymer gel of the first concentration is injected into the third segment, with an injection volume of 1 / 6 to 1 / 4 of the total profile control agent injection volume; water or polymer solution is injected into the fourth segment, with the injection volume being the sum of the wellbore volume of the injection well and the pore volume of the formation, wherein the formation pore volume is generally 2 to 5 m³, and profile control is performed based on the above-mentioned multi-segment profile control agent slug.

[0047] For example, if the profile control radius is 30m, the target layer thickness is 10m, the target layer porosity is 31%, and the sweep efficiency of the profile control agent is 0.5, then based on Formula 1, the total amount of profile control agent injected is 4380m³. 3 .

[0048] Based on the aforementioned condition that the optimal polymer gel is polymer gel A, 0.3% of polymer gel A is injected into the first segment of the multi-segment profile control slug, with an injection volume of 730–1095 mg / L. 3 ; Inject 0.4% of polymer A gel into the second segment, with an injection volume of 1460–2190 mg. 3 ; Inject 0.3% of polymer A gel into the third segment, with an injection volume of 730–1095 mg. 3 Water is injected into the fourth section, with the injection volume being the sum of the wellbore volume of the injection well and the formation pore volume of 2-5m. Profile control is then performed based on the aforementioned multi-segment profile control agent slugs.

[0049] Based on the aforementioned determination that polymer gel B is the optimal polymer gel, 0.2% of polymer gel A is injected into the first segment of the multi-segment profile control slug, with an injection volume of 730–1095 mg / L. 3 ; Inject 0.3% of polymer A gel into the second segment, with an injection volume of 1460–2190 mg. 3 ; Inject 0.2% of polymer A gel into the third segment, with an injection volume of 730–1095 mg. 3 Water is injected into the fourth section, with the injection volume being the sum of the wellbore volume of the injection well and the formation pore volume of 2-5m. Profile control is then performed based on the aforementioned multi-segment profile control agent slugs.

[0050] As can be seen from the above specific embodiments, the polymer gel system has a low initial viscosity, and the gelation strength of the same polymer gel system varies greatly at different concentrations. The polymer gel system profile control method has better adaptability than the acidizing profile control method, and can meet the requirements of effectively sealing the deep high-permeability zone in the reservoir while controlling the sealing pressure to avoid excessively high pressure, as required by the present invention. This invention provides a water injection well profile control method suitable for narrow pressure window profile control wells, which can meet the dual requirements of effectively sealing the deep high-permeability zone in the reservoir while controlling the increase in construction pressure to avoid excessive pressure. Furthermore, the entire implementation process eliminates the need for preliminary steps such as acid selection matching the target formation and compatibility testing between the acid and the profile control agent, greatly reducing the experimental workload and preparation period. No additional requirements are placed on the injection equipment; ordinary equipment can be used, reducing construction requirements and investment costs. This is beneficial for improving the efficiency of water injection well profile control, enhancing construction safety, and reducing construction costs.

[0051] Finally, it should be noted that those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented. These are exemplary embodiments disclosed in this invention; however, it should be observed that various changes and modifications can be made without departing from the scope of the embodiments as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0052] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0053] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0054] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0055] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for profile control in a water injection well, characterized in that, Includes the following steps: Determine the optimal polymer gel that matches the formation where the injection well is located; Determine the gelation strength corresponding to the optimal polymer gel at different concentrations, and based on the gelation strength, classify the optimal polymer gel at different concentrations into multiple strength levels; Determine the multi-segment profile control agent slug structure with different strength grade combinations; Calculate the injection volume of each segment in a multi-segment profile control agent slug structure; Based on the strength level and injection volume of each segment, the optimal concentration of polymer gel is injected into each segment to adjust the profile of the injection well.

2. The method for profile control of injection wells according to claim 1, characterized in that, The step of determining the optimal polymer gel that matches the formation where the injection well is located includes: Multiple candidate polymer gels were identified; Based on the gelation properties of multiple candidate polymer gels at the same concentration under the same oil reservoir temperature in the water injection well, the optimal polymer gel matching the formation where the water injection well is located is determined.

3. The method for profile adjustment of injection wells according to claim 2, characterized in that, The step of determining the optimal polymer gel that matches the formation of the water injection well based on the gelation properties of multiple candidate polymer gels at the same concentration under the same oil reservoir temperature includes: Based on the gelation time, gelation strength, and stability parameters of multiple candidate polymer gels at the same concentration and the same oil layer temperature in the water injection well, the optimal polymer gel matching the formation of the water injection well is determined.

4. The method for profile control of injection wells according to claim 1, characterized in that, The step of classifying optimal polymer gels of different concentrations into multiple strength levels based on gel strength includes: Based on the gelation strength corresponding to the optimal polymer gel at different concentrations within a preset concentration range, multiple gelation strength ranges are defined. Based on the defined range of gelation strength, multiple strength grades are determined, along with the optimal polymer gel concentration for each strength grade.

5. The method for profile control of an injection well according to claim 4, characterized in that, The step of classifying optimal polymer gels of different concentrations into multiple strength levels based on gel strength includes: Based on the gelation strength corresponding to the optimal polymer gel at different concentrations within a preset concentration range, the first gelation strength range and the second gelation strength range are divided. The first strength grade and the second strength grade are determined according to the first and second gel strength ranges, and the gel strength in the first gel strength range is less than the gel strength in the second gel strength range. Based on the first gel strength range and the second gel strength range, determine the optimal polymer gel of the first concentration and the optimal polymer gel of the second concentration corresponding to the first strength level and the second strength level.

6. The method for profile control of an injection well according to claim 5, characterized in that, The step of determining the multi-segment profile control agent slug structure with different strength grade combinations includes: Determine the target intensity level combination; Based on the target strength level combination, determine the number of segments in the multi-segment profile control agent slug structure and the optimal polymer gel concentration corresponding to each segment.

7. The method for profile control of an injection well according to claim 6, characterized in that, The step of determining the target intensity level combination includes: Based on the first and second strength levels, a multi-segment profile control agent slug structure with multiple strength levels is constructed. The target strength level combination is determined based on the rise in profile control pressure corresponding to each multi-segment profile control agent slug structure under the same injection volume conditions.

8. The method for profile control of an injection well according to claim 7, characterized in that, The step of determining the target strength grade combination based on the rise in profile control pressure corresponding to each multi-segment profile control agent slug structure under the same injection volume condition includes: Based on the principle that the pressure rise of the multi-segment profile control agent slug structure is the smallest under the same injection volume conditions, the combination of first strength grade - second strength grade - first strength grade is determined as the target strength grade combination.

9. The method for profile control of an injection well according to claim 8, characterized in that, The step of determining the number of segments in the multi-segment profiling agent slug structure and the optimal polymer gel concentration corresponding to each segment based on the target strength level combination includes: Based on the combination of the first strength level, the second strength level, and the first strength level, the first to third segments in the multi-segment profiling agent slug structure obtained in the order of injection are determined, and the optimal polymer gel with the first to third segments at the first, second, and first concentrations is determined.

10. The method for profile control of an injection well according to claim 9, characterized in that, The step of determining the number of segments in the multi-segment profiling agent slug structure and the optimal polymer gel concentration corresponding to each segment based on the target strength level combination further includes: The fourth segment of the multi-segment profile control slug structure, which is the last segment injected according to the injection sequence, is injected with water or a polymer solution.

11. The method for profile control of an injection well according to claim 10, characterized in that, The step of calculating the injection volume of each segment in the multi-segment profile control agent slug structure includes: Calculate the total amount of profile control agent to be injected into the injection well; The injection volume of each segment is determined based on the calculated total amount of profile control agent injected and the number of segments. Specifically, the injection volumes of the first to third segments are determined to account for 1 / 6 to 1 / 4, 1 / 2 to 2 / 3, and 1 / 6 to 1 / 4 of the total amount of profile control agent injected, respectively. The injection volume of the fourth segment is the sum of the wellbore volume of the injection well and the pore volume of the formation.

12. The method for profile control of an injection well according to claim 11, characterized in that, The step of calculating the total amount of profile control agent to be injected into the injection well includes: The total amount of profile control agent to be injected into the water injection well is calculated using a volumetric formula based on the radius of the corresponding profile control well, the thickness and porosity of the target layer, and the sweep efficiency of the profile control agent injected into the water injection well.

13. The method for profile control of an injection well according to claim 11, characterized in that, The step of injecting the optimal concentration of polymer gel into each segment based on the strength level and injection volume of each segment to modulate the profile of the injection well includes: Based on the injection volume and strength level corresponding to the first to fourth segments of the multi-segment profiling agent slug structure, the optimal polymer gel corresponding to the combination of the first strength level-second strength level-first strength level is injected into the first to third segments respectively, and water or polymer solution is injected into the fourth segment.

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