Balanced water drive tracking evaluation method for high water cut reservoir

Abstract

The present application relates to oil and gas field development technical field, propose a kind of high water cut reservoir balanced water drive tracking evaluation method, based on target reservoir numerical simulation model carries out the tracking evaluation of water drive balanced displacement degree, it include: extracting the water saturation data of each grid unit under different time steps in reservoir simulation;Balanced water drive tracking evaluation index system is built;The overall balanced displacement evaluation coefficient under different time steps in target reservoir is calculated;According to the balanced displacement evaluation coefficient and cumulative oil production data, the balanced water drive dynamic tracking evaluation of target reservoir is carried out;The present application can carry out accurate spatial displacement difference analysis, establish dynamic evaluation system, realize balanced water drive dynamic tracking evaluation, improve development effect, optimize development strategy.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and proposes a method for tracking and evaluating the equilibrium water drive in high water-cut reservoirs. Background Technology

[0002] High water-cut reservoirs refer to oilfields where the water volume accounts for a high proportion of the total reservoir volume, typically exceeding 70%. In such reservoirs, as extraction progresses, the proportion of water in the well-produced fluid gradually increases, while the proportion of oil relatively decreases, indicating a high degree of water displacement of the crude oil.

[0003] As traditional oil and gas resources gradually deplete, the development of high water-cut reservoirs becomes particularly important. Under prolonged water injection development, the unevenness of waterflooding effects within the reservoir increases, leading to severe water flooding in some areas while recovery rates are low in others. Tracking and evaluating the balanced waterflooding effect in high water-cut reservoirs is crucial for optimizing water injection strategies and improving reservoir development efficiency.

[0004] Chinese invention patent No. 202010577696X discloses a method for optimizing differential well spacing in balanced displacement of oil reservoirs in high water-cut stages, including: Step 1, determining the total flow rate of oil and water at the seepage interface; Step 2, determining the relationship between seepage resistance per unit length and movable oil saturation; Step 3, determining the relationship between movable oil saturation and injection-production well spacing; Step 4, determining the seepage resistance and production rate between injection and production wells; Step 5, optimizing and determining a reasonable injection-production well spacing for balanced displacement.

[0005] The aforementioned patent is based on the established standard of planar equilibrium displacement, and is grounded in the oil-water two-phase flow seepage theory. It comprehensively considers the differences in reservoir properties and mobilization degree, and can determine the reasonable injection-production well spacing for equilibrium displacement by comprehensively considering the differences in reservoir properties and mobilization degree, such as the total oil-water flow rate at the seepage interface, the seepage resistance per unit length and the relationship between movable oil saturation, and the relationship between movable oil saturation and injection-production well spacing. However, under complex reservoir conditions, the heterogeneity of reservoir properties and mobilization degree may lead to insufficient applicability and accuracy of the model.

[0006] Chinese invention patent No. 2021103182389 discloses a method for achieving balanced crude oil displacement through optimized injection-production synergistic chemical flooding. This method includes the following steps: determining the median particle size and elastic modulus of viscoelastic particles based on the average permeability of the reservoir; optimizing the concentration ratio of the total chemical agent concentration under certain conditions; statistically analyzing the physical properties of each layer and combining the layers using entropy weight algorithm and centroid-based cluster analysis; calculating the optimal segmented plug volume ratio for single-well injection under the heterogeneous permeability characteristics of the layer system; establishing an objective function by combining the coefficient of variation of remaining oil saturation, the oil enhancement effect of chemical flooding, and cost, and optimizing it using a numerical simulator; and obtaining the chemical agent concentration and dosage of the segmented plugs in each injection well and the production rate of the production well based on the above results.

[0007] The aforementioned patent combines the layering system using an entropy weight algorithm and a centroid-based clustering analysis method. It establishes an objective function by considering the coefficient of variation of remaining oil saturation, the oil enhancement effect of chemical flooding, and cost. This determines the chemical agent concentration and dosage for each injection well's segment plugs, as well as the production rate of production wells, achieving balanced crude oil displacement development and improved oil recovery. However, the applicability of the methods involved in this technology to actual complex reservoirs, the accuracy of the calculation model, and the operability of parameter optimization require further verification.

[0008] Chinese invention patent No. 2013105714662 discloses a method for balanced displacement in low-permeability reservoirs. This method includes: Step 1, establishing a three-dimensional fine geological model based on well logging data, laboratory-measured reservoir rock mechanical parameters, and seepage mechanical parameters, and using reservoir numerical simulation and geostress prediction software to clarify the distribution patterns of reservoir permeability, remaining oil saturation, pressure, and geostress; Step 2, calculating the limiting well spacing of different vertical layers; Step 3, performing variable-density perforation and chemical injection of activators; and Step 4, calculating a reasonable injection-production well spacing and designing a reasonable fracturing fracture length.

[0009] The aforementioned patent uses well logging data to establish a three-dimensional geological model and perform numerical simulations to calculate the limiting well spacing of different vertical layers. It then performs variable-density perforation and chemical flooding to design reasonable fracturing fracture lengths, thereby improving the reservoir's equilibrium displacement. However, this method faces challenges in practical operation, including high modeling costs and stringent data accuracy requirements.

[0010] Chinese invention patent No. 2020101397771 discloses a design method for polymer injection equilibrium displacement in thick sandstone reservoirs, including: 1. Collection of basic data on thick sandstone reservoirs; 2. Quantitative calculation of the dimensionless equilibrium displacement factor N; 3. Sensitivity analysis of the dimensionless equilibrium displacement factor N parameter; 4. Determination of the relationship between the dimensionless equilibrium displacement factor N and the longitudinal sweep efficiency Ev; 5. Determination of the reasonable dimensionless displacement factor N for different rhythmic oil layers; 6. Plotting relevant graphs of the increase in the longitudinal sweep efficiency Ev of polymer injection per unit dimensionless displacement factor for different rhythmic oil layers; 7. Querying the reasonable injection-production well spacing for polymer injection in different rhythmic oil layers; 8. Querying the reasonable injection-production pressure difference for different rhythmic oil layers.

[0011] The aforementioned patent, through quantitative calculation of the dimensionless equilibrium displacement factor and parameter sensitivity analysis, determines the reasonable dimensionless displacement factor for oil layers with different rhythms and plots it on a chart, thus improving the study of vertical sweep efficiency. However, because this method relies on the quantitative calculation and sensitivity analysis of the dimensionless equilibrium displacement factor, the calculation results may be inaccurate due to the influence of multiple complex factors.

[0012] Chinese invention patent No. 2020109583792 discloses a quantitative evaluation method for the feasibility of flow field adjustment based on reservoir equilibrium displacement, including: detecting the remaining oil status, reservoir equilibrium displacement status, and the matching status of injection and production with equilibrium displacement in the oilfield development unit; and judging the feasibility of implementing flow field adjustment in the development unit based on the detection results and in combination with the flow field adjustment feasibility evaluation criteria.

[0013] The aforementioned patents assess the feasibility of implementing flow field adjustments in development units based on factors such as the remaining oil status of the oilfield development unit, the reservoir equilibrium displacement status, the current status of injection and production and the equilibrium displacement status, and the matching status of injection and production and equilibrium displacement. However, in the ultra-high water-cut stage of reservoir development, data acquisition and comprehensive analysis are quite difficult.

[0014] Patent No. 2021104938853 discloses a well location optimization method and system based on balanced displacement degree analysis. The method establishes a reservoir streamline simulation model, divides the reservoir into production potential and water injection potential based on the model grid parameters, sets initial values ​​for well placement parameters through set strategy parameters, forms multiple initial well placement schemes, and then calls the streamline simulator in parallel to calculate the fitness value of each initial well placement scheme, realizes the evaluation based on the displacement uniformity, selects the initial global optimal well placement scheme, uses an improved particle swarm optimization algorithm to iteratively calculate optimization parameters, and determines the final well placement scheme based on the set iterative calculation scheme.

[0015] The aforementioned patent establishes a reservoir streamline model, divides production potential and water injection potential, and uses an improved particle swarm optimization algorithm to optimize well placement parameters and determine the final well placement scheme, thereby achieving balanced water drive and improving reservoir recovery. However, this method is not very applicable to actual reservoirs.

[0016] The invention patent with patent number 2020100085645 discloses a method for determining the production ratio of production wells in a balanced displacement process, including: step 1. determining the affected area of ​​different injection-production well distances; step 2. dividing the affected area of ​​a straight one-injection-two-production well group; step 3. determining the remaining recoverable reserves within the affected area of ​​each injection-production well group; and step 4. determining the production ratio of different production wells.

[0017] The aforementioned patent divides the affected area of ​​a linear one-injection-two-production well group based on the affected area of ​​different injection-production well distances, determining the remaining recoverable oil reserves and the production allocation ratio of different production wells. However, the simplification of the affected area division in this method may lead to insufficient adaptability to complex geological conditions, and the determination of the production allocation ratio may lack the ability to adjust in real time to dynamically changing reservoir conditions. Summary of the Invention

[0018] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs, thereby solving the following technical problems:

[0019] ① There is a lack of methods for tracking and evaluating the equilibrium waterflooding in high water-cut reservoirs;

[0020] ② Commonly used equilibrium displacement evaluation indicators are simple to describe the current state of equilibrium displacement in reservoirs, and cannot effectively characterize the dynamic equilibrium displacement degree of water drive at different time steps during reservoir development.

[0021] To achieve the above objectives, the present invention adopts the following technical solution:

[0022] A method for tracking and evaluating the equilibrium waterflooding in high water-cut reservoirs, based on a numerical simulation model of the target reservoir, includes:

[0023] Water saturation data of each grid cell at different time steps in reservoir simulation were extracted;

[0024] Construct an evaluation index system for reservoir equilibrium waterflooding;

[0025] Calculate the overall equilibrium displacement evaluation coefficient of the target reservoir at different time steps;

[0026] Based on the equilibrium displacement evaluation coefficient and cumulative oil production data, the equilibrium water-driven state tracking evaluation of the target reservoir is carried out.

[0027] Furthermore, the constructed reservoir equilibrium waterdrive tracking and evaluation index system includes:

[0028] The numerical simulation model divides the space into multiple grid cells, uses the grid cells as evaluation objects, and extracts the feature parameters and remaining oil data of the grid cells.

[0029] Based on the remaining oil data and the relationship between the ratio of oil to water relative permeability and water saturation in the water drive characteristic curve during the high water cut period, the fitting coefficient was calculated.

[0030] Based on the fitting coefficient and characteristic parameters, the evaluation coefficient of the balanced water drive tracking of each grid unit is calculated, and the evaluation index representing the balance of water distribution in each grid unit is obtained.

[0031] Furthermore, the characteristic parameters of the grid cells include the initial oil saturation, residual oil saturation, and bound water saturation of each grid cell; the remaining oil data includes the remaining oil saturation, oil phase viscosity, water phase viscosity, oil phase volume factor, water phase volume factor, and oil-water phase permeation curve.

[0032] Furthermore, the formulas for calculating the fitting coefficients d and c are as follows:

[0033]

[0034] In the formula: k ro The relative permeability of the oil phase; k rw S represents the relative permeability of the aqueous phase. w This represents the water saturation level.

[0035] Furthermore, under oil-water two-phase flow conditions, the cumulative water production and cumulative oil production satisfy the following formula:

[0036]

[0037] In the formula: d and c are constants related to reservoir and fluid properties; μ o Oil phase viscosity, mPa·s; μ w B is the viscosity of the aqueous phase, in mPa·s. o B is the formation oil volume factor; w S is the formation water volume factor; w S represents the average water saturation between injection and production wells. wc W represents the saturation of bound water between injection and production wells. p For cumulative water production, m 3 N p For cumulative oil production, m 3 .

[0038] Furthermore, under the condition of injection-production balance, the relationship between cumulative water injection volume and water saturation, as well as the scale of movable oil geological reserves, are obtained, as follows:

[0039]

[0040] Furthermore, the formula for the equilibrium displacement evaluation index characterizing the water distribution of each grid unit is as follows:

[0041]

[0042] In the formula: S w S represents the water phase saturation. o Residual oil saturation S o =1-S w S oi S represents the initial oil saturation. or S represents residual oil saturation. wc The bound water saturation; μ o Oil phase viscosity; μ w B is the viscosity of the aqueous phase. o B is the oil phase volume coefficient; w is the volume coefficient of the aqueous phase; d and c are fitting coefficients; e represents an exponential function with the natural constant e as the base.

[0043] Furthermore, the calculation of the overall equilibrium displacement evaluation coefficient of the target reservoir at different time steps includes:

[0044] The number of grid cells n for the numerical simulation of the target reservoir is determined, and the sample set for evaluating the isostatic displacement degree of the target reservoir is X = {x1, x2, ..., x...} j If 1 ≤ j ≤ n, then the overall evaluation sample set of the isostatic displacement degree of the target reservoir under different time steps is X. i ={X1, X2, ..., X i}, where i is the numerical simulation time;

[0045] The overall equilibrium displacement evaluation coefficient was applied to evaluate the equilibrium displacement degree of the target reservoir in the sample set X. i ={X1, X2, ..., X i A comprehensive difference assessment was conducted, calculating the overall isostatic displacement degree at different time steps during the development of the target reservoir:

[0046]

[0047] In the formula, CV is the overall equilibrium displacement evaluation coefficient; X i As the displacement evaluation index for each grid cell, This is the average value of the displacement coefficients for all grid cells.

[0048] Furthermore, the equilibrium water-driven state tracking evaluation of the target reservoir also includes drawing a graph showing the relationship between the overall equilibrium displacement evaluation coefficient and the cumulative oil production of the target reservoir based on the calculated equilibrium displacement coefficient and cumulative oil production data.

[0049] Furthermore, the smaller the overall equilibrium displacement coefficient, the smaller the difference in the degree of equilibrium displacement of the target reservoir's water drive, the better the equilibrium displacement effect, and the better the reservoir development effect; conversely, the greater the difference in the degree of equilibrium displacement of the target reservoir's water drive, the worse the equilibrium displacement effect, and the worse the reservoir development effect.

[0050] The beneficial effects of this invention are as follows:

[0051] This invention enables dynamic tracking and evaluation of equilibrium waterflooding in high water-cut reservoirs. Its innovative effects in the field of equilibrium displacement evaluation are described in detail below:

[0052] (1) Precise spatial displacement difference analysis: In view of the common problem of spatial displacement difference in reservoirs with high water cut, this invention constructs a balanced water drive tracking evaluation index system based on grid water distribution, which can accurately analyze the displacement effect of each grid unit in the reservoir, thereby providing more detailed and accurate data support for reservoir development.

[0053] (2) Establishment of dynamic evaluation system: This invention dynamically characterizes the degree of equilibrium displacement at different time steps during the overall development of the reservoir, making the evaluation process more in line with the actual dynamic changes of the reservoir and improving the real-time performance and accuracy of the evaluation.

[0054] (3) Balanced water-driven state tracking: Through dynamic tracking and evaluation, this invention can monitor the development status of the reservoir in real time, detect imbalances in the displacement process in a timely manner, and provide a scientific basis for adjusting water injection strategies and optimizing development plans.

[0055] (4) Improve development effect: Through dynamic evaluation and adjustment, this invention helps to improve the overall oil displacement efficiency of the reservoir, reduce ineffective water injection, and reduce development costs, thereby improving the development effect of the reservoir.

[0056] (5) Optimize development strategy: The evaluation results of this invention can provide decision support for the development team, help to formulate more reasonable water injection schemes and development strategies, thereby improving the reservoir development effect. Attached Figure Description

[0057] Figure 1 A flowchart of a method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs;

[0058] Figure 2 The oil-water relative permeability curve is shown in the example.

[0059] Figure 3 This is a graph showing the relationship between the equilibrium displacement coefficient and cumulative oil production at different time steps in the example. Detailed Implementation

[0060] 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.

[0061] Example 1:

[0062] like Figure 1 As shown, a method for tracking and evaluating the equilibrium waterflooding in high water-cut reservoirs is proposed. This method dynamically characterizes the degree of equilibrium displacement at different time steps during reservoir development, enabling the tracking and evaluation of the equilibrium displacement during waterflooding in high water-cut reservoir development. This guides oilfield production practices to improve oilfield development efficiency. To achieve the above objectives, the present invention adopts the following technical solution:

[0063] Step 1: Conduct numerical simulation studies of high water-cut reservoirs and extract water saturation data for each grid cell at different time steps: For the target reservoir numerical simulation model, conduct reservoir development numerical simulation studies and extract water saturation data S for each grid cell at different time steps in the reservoir simulation. w ;

[0064] Step 2: Extract the characteristic parameters and remaining oil data of each grid cell to construct an evaluation index system for the equilibrium waterdrive in high water-cut reservoirs. The specific steps are as follows:

[0065] Step 201: Using each grid cell in the numerical simulation model space as the evaluation object, extract the characteristic parameters and remaining oil data of the grid cell. The characteristic parameters of the grid cell include the initial oil saturation, residual oil saturation, and bound water saturation of each grid cell; the remaining oil data includes the remaining oil saturation, oil phase viscosity, water phase viscosity, oil phase volume factor, water phase volume factor, and oil-water phase permeability curve.

[0066] Step 202: Based on the oil-water relative permeability curve of the target reservoir extracted in Step 201, and combined with the relationship between the ratio of oil to water relative permeability and water saturation in the water drive characteristic curve during the high water cut period, coefficient fitting is performed using Origin software. The fitting formula is as follows:

[0067]

[0068] In the formula: k ro The relative permeability of the oil phase; k rw S represents the relative permeability of the aqueous phase. w denoted as water saturation; d and c are fitting coefficients.

[0069] Step 203: Based on the above steps, construct an evaluation index system for the equilibrium waterflooding of high water-cut reservoirs. Under oil-water two-phase flow conditions, the cumulative water production and cumulative oil production satisfy the relationships (2) and (3):

[0070]

[0071] In the formula: d and c are constants related to reservoir and fluid properties; μ o Oil phase viscosity, mPa·s; μ w B is the viscosity of the aqueous phase, in mPa·s. o B is the formation oil volume factor; w S is the formation water volume factor; w S represents the average water saturation between injection and production wells. wc W represents the saturation of bound water between injection and production wells. p For cumulative water production, m 3 N p For cumulative oil production, m 3 .

[0072] Under the condition of injection-production balance, the relationship between cumulative water injection and water saturation is obtained by formula (4), and the scale of movable oil geological reserves is shown in formula (5):

[0073]

[0074] Combining formulas (4) and (5), the equilibrium displacement evaluation index formula (6) characterizing the water distribution of each grid unit is obtained as follows:

[0075]

[0076] In the formula: S w S represents the water phase saturation. o Residual oil saturation S o =1-S w S oi S represents the initial oil saturation. or S represents residual oil saturation. wc The bound water saturation; μ o Oil phase viscosity; μ w B is the viscosity of the aqueous phase. o B is the oil phase volume coefficient; w is the volume coefficient of the aqueous phase; d and c are fitting coefficients; e represents an exponential function with the natural constant e as the base.

[0077] Combined with equation (6), the equilibrium water drive tracking evaluation coefficient of each grid unit is calculated, and the evaluation index λ representing the equilibrium degree of water distribution in each grid unit is constructed to reflect the difference in the equilibrium displacement degree of each grid unit in the water drive reservoir during the high water cut stage, and to guide the design of reservoir development scheme.

[0078] Step 3: Calculate the overall equilibrium displacement evaluation coefficient for high water-cut reservoirs at different time steps: Taking each grid cell from the numerical simulation as the evaluation object, and based on the constructed evaluation index system for equilibrium water-drive tracking in high water-cut reservoirs, the degree of equilibrium displacement is calculated at different time steps based on the overall equilibrium displacement evaluation coefficient. The specific steps are as follows:

[0079] Step 301: Determine the number of grid cells n in the numerical simulation of the target reservoir. Taking each grid cell as the evaluation object, based on the construction of the evaluation index system for equilibrium waterflooding in high water-cut reservoirs, and based on Step 1 and Step 2, determine the evaluation sample set for the equilibrium displacement degree of the target reservoir as X = {x1, x2, ..., x...} j If 1 ≤ j ≤ n, then the overall evaluation sample set of the isostatic displacement degree of the target reservoir under different time steps is X. i ={X1, X2, ..., X i (i is the numerical simulation time).

[0080] Step 302: Apply the overall equilibrium displacement evaluation coefficient to evaluate the overall equilibrium displacement degree of the target reservoir on the sample set X. i ={X1, X2, ..., X i} To conduct an overall difference evaluation, the degree of overall equilibrium displacement at different time steps during the development of the target reservoir is calculated using formula (7):

[0081]

[0082] In the formula, CV is the overall equilibrium displacement evaluation coefficient; X i X is the displacement evaluation index for each grid cell, and X is the average value of the equilibrium displacement coefficients of all grid cells.

[0083] Step 4: Plot the relationship between the overall equilibrium displacement evaluation coefficient and cumulative oil production of the target reservoir, and conduct an equilibrium water-driven dynamic tracking evaluation of high water-cut reservoirs: Based on the calculated equilibrium displacement coefficient and cumulative oil production data, plot the following chart: Figure 3 As shown in the figure, based on the calculation method and chart of the overall equilibrium displacement coefficient, the smaller the overall equilibrium displacement coefficient, the smaller the difference in the degree of equilibrium displacement of the target reservoir's water-driven water, the better the equilibrium displacement effect, and the better the reservoir development effect; conversely, the greater the difference in the degree of equilibrium displacement of the target reservoir's water-driven water, the worse the equilibrium displacement effect, and the worse the reservoir development effect. Therefore, equilibrium water-driven dynamic tracking and evaluation of high water-cut reservoirs can be carried out.

[0084] Example 2:

[0085] The following steps were taken to conduct a follow-up evaluation of the equilibrium waterflooding of high water-cut reservoirs in the typical XBQ block:

[0086] Step 1: Conduct numerical simulation studies of high water-cut reservoirs and extract the water saturation S of each grid cell at different time steps. w The reservoir has a grid size of 179×122×143. A numerical simulation study was conducted on this actual reservoir block, taking into account the existing production regime, to extract the water saturation data S of each grid cell at different time steps. w .

[0087] Step 2: Extract characteristic parameters and remaining oil data for each grid cell to construct an evaluation index system for equilibrium waterflooding in high water-cut reservoirs. The specific implementation steps are as follows:

[0088] Obtain the residual oil saturation S of each saturation zone of the reservoir in this embodiment. or Bound water saturation S wc The initial oil saturation data S of each grid cell was extracted using the tNavigator software. oi Using formula S o =1-S w Combined with the water saturation data S of each grid cell extracted in step 1 w Calculate the residual oil saturation at different time steps; water phase viscosity μ. w =0.6 mPa·s. Considering the pressure of each grid cell at different time steps in the reservoir, the oil phase viscosity μ of each grid cell at different time steps is obtained by differential calculation. o Oil phase volume coefficient B o Water phase volume coefficient B w =1; Oil-water interpenetration curve as shown Figure 2 As shown.

[0089] For the reservoir in this embodiment, the relative permeability curve data of the reservoir were fitted using the fitting formula (1). The fitting coefficients for saturation partition 1 of the reservoir in this embodiment were d = 8.49803 and c = -12.23696; the fitting coefficients for saturation partition 2 were d = 5.6219 and c = -15.23696; and the fitting coefficients for saturation partition 3 were d = 3.49803 and c = -10.23696. According to formula (6), combined with the target reservoir of this embodiment, the evaluation index λ of the grid balance of each unit under different time steps of the reservoir simulation of this embodiment was calculated, which was used for subsequent evaluation of the water drive balance of high water-cut reservoirs.

[0090] Step 3: Calculate the overall equilibrium displacement evaluation coefficient for high water-cut reservoirs at different time steps: Taking each grid cell from the numerical simulation as the evaluation object, and based on the established evaluation index system for equilibrium water-drive tracking in high water-cut reservoirs, the degree of equilibrium displacement is calculated at different time steps based on the equilibrium displacement coefficient. The specific steps are as follows:

[0091] Under the existing reservoir conditions in this embodiment, the grid size of the XBQ reservoir block is 179×122×143. Taking each grid cell as the evaluation object, the evaluation sample set of the reservoir equilibrium displacement degree and the overall evaluation sample set of equilibrium displacement under different time steps of reservoir simulation are calculated according to steps 1 and 2. The overall equilibrium displacement evaluation coefficient under different time steps during reservoir development is calculated.

[0092] Step 4: Plot the relationship between the overall equilibrium displacement evaluation coefficient and cumulative oil production of the target reservoir, and conduct equilibrium water-driven dynamic tracking evaluation of the high water-cut reservoir: Based on the actual production time of the reservoir in this example, a numerical simulation study is conducted. The overall equilibrium displacement evaluation coefficient of the high water-cut reservoir at different time steps is calculated from Step 3, and the relationship between the overall equilibrium displacement evaluation coefficient and cumulative oil production is plotted as follows: Figure 3 A tracking evaluation of the equilibrium water-driven state in high water-cut reservoirs was conducted. Based on the actual production situation of the oilfield, the results of the established tracking evaluation method are consistent with the actual historical production stages of the reservoir, as shown in the charts. The overall development process of the reservoir can be subdivided into four stages: Stage 1: Natural energy development; Stage 2: Water injection development; Stage 3: Well network improvement; Stage 4: Production wells to injection. Before production, the reservoir was in a relatively equilibrium state. In the first stage, there were few production wells and no water injection wells, indicating depletion-type production. The overall equilibrium displacement coefficient of the reservoir gradually increased, indicating a gradual increase in the degree of equilibrium displacement. In the water injection development stage, the newly added water injection wells began to replenish formation energy, and the equilibrium displacement coefficient showed an overall fluctuating downward trend, indicating a significant improvement in the degree of equilibrium displacement in this stage. During the well network improvement phase, as the injection-production well network gradually improves, the number of production wells begins to exceed the number of injection wells. This leads to insufficient replenishment of underground energy, resulting in an increased equilibrium displacement coefficient, indicating a deterioration in the reservoir's equilibrium displacement. During the production well to injection phase, with some production wells being converted to injection, the degree of water drive control and utilization significantly improves, and the reservoir's equilibrium displacement coefficient gradually decreases, indicating an overall improvement in the reservoir's equilibrium water drive. In summary, the results of this evaluation method are consistent with the actual production situation in the oilfield, further validating the feasibility of the method.

[0093] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for tracking and evaluating the equilibrium waterflooding in high water-cut reservoirs, characterized by tracking and evaluating the degree of equilibrium waterflooding displacement based on a numerical simulation model of the target reservoir. include: Water saturation data of each grid cell at different time steps in reservoir simulation were extracted; Construct an evaluation index system for reservoir equilibrium waterflooding; Calculate the overall equilibrium displacement evaluation coefficient of the target reservoir at different time steps; Based on the equilibrium displacement evaluation coefficient and cumulative oil production data, the equilibrium water-driven state tracking evaluation of the target reservoir is carried out.

2. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 1, characterized in that, The constructed reservoir equilibrium waterflooding tracking and evaluation index system includes: The numerical simulation model divides the space into multiple grid cells, uses the grid cells as evaluation objects, and extracts the feature parameters and remaining oil data of the grid cells. Based on the remaining oil data and the relationship between the ratio of oil to water relative permeability and water saturation in the water drive characteristic curve during the high water cut period, the fitting coefficient was calculated. Based on the fitting coefficient and characteristic parameters, the evaluation coefficient of the balanced water drive tracking of each grid unit is calculated, and the evaluation index representing the balance of water distribution in each grid unit is obtained.

3. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 2, characterized in that, The characteristic parameters of the grid cells include the initial oil saturation, residual oil saturation, and bound water saturation of each grid cell; the remaining oil data includes the remaining oil saturation, oil phase viscosity, water phase viscosity, oil phase volume factor, water phase volume factor, and oil-water phase permeability curve.

4. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 3, characterized in that, The formulas for calculating the fitting coefficients d and c are as follows: In the formula: k ro The relative permeability of the oil phase; k rw S represents the relative permeability of the aqueous phase. w This represents the water saturation level.

5. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 4, characterized in that, This also includes the cumulative water production and cumulative oil production satisfying the following formula under oil-water two-phase flow conditions: In the formula: d and c are constants related to reservoir and fluid properties; μ o Oil phase viscosity, mPa·s; μ w B is the viscosity of the aqueous phase, in mPa·s. o B is the formation oil volume factor; w S is the formation water volume factor; w S represents the average water saturation between injection and production wells. wc W represents the saturation of bound water between injection and production wells. p For cumulative water production, m 3 ; N p For cumulative oil production, m 3 .

6. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 5, characterized in that, This also includes, under injection-production balance conditions, obtaining the relationship between cumulative water injection volume and water saturation, and the scale of movable oil geological reserves, as shown in the following formula:

7. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 6, characterized in that, The formula for the equilibrium displacement evaluation index characterizing the water distribution of each grid unit is as follows: In the formula: S w S represents the water phase saturation. o Residual oil saturation S o =1-S w S oi S represents the initial oil saturation. or S represents residual oil saturation. wc The bound water saturation; μ o Oil phase viscosity; μ w B is the viscosity of the aqueous phase. o B is the oil phase volume coefficient; w is the volume coefficient of the aqueous phase; d and c are fitting coefficients; e represents an exponential function with the natural constant e as the base.

8. A method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to any one of claims 1-7, characterized in that, The overall equilibrium displacement evaluation coefficients for the target reservoir at different time steps include: The number of grid cells n for the numerical simulation of the target reservoir is determined, and the sample set for evaluating the isostatic displacement degree of the target reservoir is X = {x1, x2, ..., x...} j If 1 ≤ j ≤ n, then the overall evaluation sample set of the isostatic displacement degree of the target reservoir under different time steps is X. i ={X1, X2, ..., X i }, where i is the numerical simulation time; The overall equilibrium displacement evaluation coefficient was applied to evaluate the equilibrium displacement degree of the target reservoir in the sample set X. i ={X1, X2, ..., X i A comprehensive difference assessment was conducted, calculating the overall isostatic displacement degree at different time steps during the development of the target reservoir: In the formula, CV is the overall equilibrium displacement evaluation coefficient; X i As the displacement evaluation index for each grid cell, This is the average value of the displacement coefficients for all grid cells.

9. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 8, characterized in that, The equilibrium water-driven state tracking evaluation of the target reservoir also includes drawing a graph showing the relationship between the overall equilibrium displacement evaluation coefficient and the cumulative oil production of the target reservoir based on the calculated equilibrium displacement coefficient and cumulative oil production data.

10. The method for tracking and evaluating the equilibrium waterflooding of high water-cut reservoirs according to claim 9, characterized in that, The smaller the overall equilibrium displacement coefficient, the smaller the difference in the degree of equilibrium displacement in the target reservoir's water drive, the better the equilibrium displacement effect, and the better the reservoir development effect; conversely, the greater the difference in the degree of equilibrium displacement in the target reservoir's water drive, the worse the equilibrium displacement effect and the worse the reservoir development effect.

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