Water-drive reservoir fluid channeling channel quantitative characterization method

Abstract

The invention relates to a quantitative characterization method for a fluid channeling channel of a water-drive reservoir, and belongs to the technical field of oil exploitation. The method comprises the following steps: (1) determining a rank correlation coefficient of a water injection well and a producing well according to the water injection rate of the water injection well and the water yield of the producing well in a target area, and judging whether a channeling channel exists between the two wells or not; (2) the radius (d) of the channeling channel is calculated according to the following formula: # imgabs0 #, mu is the fluid viscosity, L is the distance between the water injection well and the oil production well, and a is the absolute value of the slope of the fitting relation between the water injection rate of the water injection well and the production pressure difference; and (3) calculating the volume of the channeling channel by using a Poiseuille law and the radius. According to the method, quantitative description of the fluid channeling direction and volume is achieved, and a basis is provided for the dosage of a profile control agent in the design of a water drive plugging scheme.

Description

Technical Field

[0001] The invention relates to a quantitative characterization method for crossflow channels in a water-driven oil reservoir, and belongs to the technical field of oil production. Background Art

[0002] Waterflooding is the most commonly used method for enhancing oil recovery in secondary oilfields. Currently, most oilfields in China have entered the development phase with extremely high water cuts (water cuts >90%). Experience with waterflooding in oilfields both domestically and internationally indicates that the formation of crossflow channels is inevitable after entering the medium-to-high water cut phase. During long-term waterflooding, geological factors such as reservoir heterogeneity and development factors such as rapid production rates increase the pore throat radius of the reservoir, leading to the formation of secondary high-permeability zones, or crossflow channels, within the reservoir. These channels, also known as dominant seepage channels, result in inefficient and ineffective circulation of large amounts of injected water, reducing the sweep efficiency and severely impacting the effectiveness of waterflooding. Therefore, timely profile control and plugging are crucial parameters in designing waterflooding plugging strategies.

[0003] The quantitative characterization of crossflow channels involves identifying the direction of crossflow channels and calculating the volume of crossflow channels. Currently, there are four main methods for identifying crossflow channels: (1) Qualitative analysis: using basic dynamic and static data of the reservoir, manually analyzing the direction and possibility of crossflow between oil and water wells; (2) Numerical simulation of seepage: similar to the streamline test analysis method developed in recent years, using reservoir static data modeling and dynamic development simulation inversion, drawing the flow field or potential field in the well area when the simulation degree is high, and obtaining the direction of the crossflow channel based on the density and direction of the streamlines; (3) Quantitative decision-making: through quantitative index analysis and joint calculation, the comprehensive weight (or correlation) of the crossflow channel type is obtained; (4) Field measurement and testing: the approximate direction of the crossflow channel is obtained by measuring the indicators between oil and water wells in the mine, such as well test analysis (interference well test, unstable well test, pulse well test), pressure system analysis, tracer injection, injection and production component comparison analysis. However, the above methods have problems such as complex solution process, being greatly affected by instruments and field construction factors, and are not convenient for field operation. Existing methods for calculating the volume of crossflow channels, such as the Rdos simulation method, the displacement multiple identification method, and the numerical simulation streamline method, all rely on numerical simulation technology, are difficult to implement, and are not suitable for on-site engineers to quickly calculate the volume of crossflow channels. Summary of the Invention

[0004] The purpose of the present invention is to provide a quantitative characterization method for crossflow channels in water-flooded oil reservoirs, which provides a method for the prior art that is simple in calculation and can achieve quantitative description of the direction and volume of crossflow channels.

[0005] In order to achieve the above-mentioned object, the technical solution of the method for quantitatively characterizing crossflow channels in water-flooded oil reservoirs of the present invention is:

[0006] A method for quantitatively characterizing crossflow channels in a water-flooding reservoir comprises the following steps:

[0007] (1) According to the water injection volume of the injection wells and the water production volume of the oil production wells in the target area, the rank correlation coefficient between the injection wells and the oil production wells is determined to determine whether there is a crossflow channel between the two wells;

[0008] (2) Calculate the radius (d) of the crossflow channel according to the following formula:

[0009] Wherein, μ is the fluid viscosity, L is the distance between the injection well and the production well, and a is the absolute value of the slope of the fitting relationship between the injection volume of the injection well and the production pressure difference;

[0010] (3) Calculate the volume of the crossflow channel using Poiseuille's law and the radius.

[0011] The beneficial effect of the above technical solution is that the method for quantitatively characterizing crossflow channels in water-driven oil reservoirs of the present invention is a pioneering invention. At present, after most domestic oil reservoirs enter the ultra-high water cut period, there are problems such as the development of crossflow channels and low water injection utilization rate. The present invention first uses the Spearman rank correlation coefficient method to determine the direction of the crossflow channel based on the dynamic data of the injection and production wells, and then fits the injection-production pressure difference and the injection volume based on the capillary bundle model to obtain the correlation coefficient, thereby calculating the radius and volume of the crossflow channel. The present invention uses production dynamic data to quantitatively calculate the crossflow channel of the oil reservoir, which can avoid parameters that are difficult to obtain and improve the accuracy of the calculation results. Moreover, the quantitative characterization method of the present invention accurately determines the direction of the crossflow channel and calculates the volume of the crossflow channel, which provides a basis for the selection of wells and plugging agents for later profile adjustment and water plugging in the oil field. At the same time, compared with the existing technology, the quantitative characterization method of the present invention is simple and practical, can be promoted and used in the production line, and provide technical support for the continuous potential of old oil fields.

[0012] As a further improvement, in step (1), the rank correlation coefficient (r) is calculated according to the following formula:

[0013] Among them, x is the water injection volume of the injection well, and y is the water production volume of the oil well.

[0014] As a further improvement, when the rank correlation coefficient is less than 0.2, there is no crossflow channel between the two wells; and when the rank correlation coefficient is greater than 0.2, it indicates that there is a crossflow channel between the two wells.

[0015] As a further improvement, the volume (V) of the crossflow channel is calculated in step (3) according to the following formula: V = πd 2 L, where d is the radius of the crossflow channel and L is the distance between the injection well and the oil production well. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of an algorithm for implementing the direction and volume of water flooding channel in the method for quantitatively characterizing water flooding reservoir channel in the present invention;

[0017] Figure 2 is the injection-production corresponding curve of the actual injection-production well group in Example 1 of the present invention;

[0018] Figure 3 1 is a curve showing the relationship between the injection pressure difference and the water injection rate of the actual injection well group in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] At present, after most domestic oil reservoirs enter the ultra-high water cut period, there are problems such as the development of crossflow channels and low water injection utilization rate. The present invention first uses the Spearman rank correlation coefficient method to determine the direction of the crossflow channel based on the dynamic data of the injection and production wells, and then fits the injection and production pressure difference and the injection volume based on the capillary bundle model to obtain the correlation coefficient, thereby calculating the radius and volume of the crossflow channel. The present invention uses production dynamic data to quantitatively calculate the crossflow channel of the oil reservoir, which can avoid parameters that are difficult to obtain and improve the accuracy of the calculation results. Moreover, the quantitative characterization method of the present invention accurately determines the direction of the crossflow channel and calculates the volume of the crossflow channel, providing a basis for the selection of wells and plugging agents for late-stage profile adjustment and water plugging in the oil field. At the same time, compared with the prior art, the quantitative characterization method of the present invention is simple and practical, can be promoted and used in the production line, and provides technical support for the continuous potential of old oil fields.

[0020] The process of implementing the water flooding channel direction and volume algorithm in the water flooding oil reservoir channel quantitative characterization method of the present invention is as follows: Figure 1 As shown, the specific steps include:

[0021] (1) Based on the actual injection and production parameters of the target reservoir, a curve is drawn showing the relationship between the water injection rate of the water injection wells and the water production rate of the oil production wells within the injection and production well group, and the rank correlation coefficient between the water injection wells and the oil production wells is calculated to determine whether there is a crossflow channel between the two wells;

[0022] (2) Calculate the radius (d) of the crossflow channel according to the following formula: Where μ is the fluid viscosity, L is the distance between the injection well and the production well, and a is the absolute value of the slope of the fitting relationship between the injection volume of the injection well and the production pressure difference.

[0023] (3) Calculate the volume of the crossflow channel using Poiseuille's law and the radius.

[0024] The above crossflow channel radius calculation method is derived from the tube bundle conductivity model, that is, the radius of the ideal tube bundle is d, and according to the Hagen-Poiseuille equation, its volume flow rate (Q) equation is Q = πd 4 Δp / 8μL, sorted as make The formula for calculating the crossflow channel radius is obtained. Here, μ is the fluid viscosity, L is the distance between the injection well and the production well, and Δp is the volume flow rate and the pressure difference across the pipe.

[0025] As a further improvement, in step (1), the rank correlation coefficient (r) is calculated according to the following formula: Among them, x is the water injection volume of the injection well, and y is the water production volume of the oil well.

[0026] As a further improvement, when the rank correlation coefficient is less than 0.2, there is no crossflow channel between the two wells; and when the rank correlation coefficient is greater than 0.2, it indicates that there is a crossflow channel between the two wells.

[0027] Visualized flat-plate waterflooding experiments confirm that when water channeling occurs in unidirectional wells, the correlation coefficient is greater than 0.2. However, the rank correlation coefficients for bidirectional and multi-directional wells are smaller than those for unidirectional wells and less than 0.2. Therefore, the present invention uses a correlation coefficient of 0.2 as the criterion for determining whether water channeling has occurred. A value greater than 0.2 indicates water channeling has occurred, while a value less than 0.2 indicates that a channeling channel has not yet developed.

[0028] As a further improvement, the volume (V) of the crossflow channel is calculated in step (3) according to the following formula: V = πd 2 L, where d is the radius of the crossflow channel and L is the distance between the injection well and the oil production well.

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be noted that, unless otherwise specified, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. The equipment and raw materials used are all commercially available or commonly used in the art. The methods in the following embodiments are all conventional methods in the art unless otherwise specified.

[0030] In the following examples, unless otherwise specified, the operations described are routine operations in the art.

[0031] In the following examples, unless otherwise specified, all raw materials used are conventional commercial products in the art.

[0032] A specific embodiment of a method for quantitatively characterizing crossflow channels in a water-flooding oil reservoir according to the present invention:

[0033] Example 1

[0034] Taking the water injection well 5-12 and oil production well H7-126 of a certain oil field as an example, the quantitative characterization method of crossflow channels in the water drive reservoir of this embodiment is described. The specific implementation operations are as follows:

[0035] 1. According to the actual injection and production parameters of water injection well 5-12 and oil production well H7-126, draw the water injection well 5-12 and oil production well H7-126 in VI7 2 Small layer injection and production corresponding curve, as shown in the following example: Figure 2 As shown. According to the formula The rank correlation coefficient (r) between the two wells is calculated to be 0.2021. Where x is the injection volume of the injection well and y is the water production of the production well.

[0036] Since the rank correlation coefficient of the two wells is 0.2021, which is greater than 0.2, it indicates that there is a high possibility of a crossflow channel between the two wells.

[0037] 2. The injection-production pressure difference and daily water injection rate of water injection well 5-12 and oil production well H7-126 are shown in Table 1. The data of injection-production pressure difference and daily water injection rate of water injection well 5-12 and oil production well H7-126 are fitted to obtain the injection-production relationship curve, as shown in Table 1. Figure 3 As shown in the figure, there is a linear relationship between the injection-production pressure difference and the daily water injection rate, with a slope of -31.66. The absolute value of this slope is used to calculate the diameter of the crossflow channel between the two wells.

[0038] Table 1 Water injection well 5-12 and oil production well H7-126 in VI7 2 Calculation parameters of small layer crossflow channel

[0039] date Injection-production pressure difference (MPa) <![CDATA[Daily water injection volume (m 3 / d)]]> 2021 / 6 / 1 13.71 556 2021 / 7 / 1 14.66 598.5 2021 / 8 / 1 13.69 594.5 2021 / 9 / 1 14.4 612 2021 / 10 / 1 14.91 642.5 2021 / 11 / 1 16.06 600 2021 / 12 / 1 15.09 389.5 2022 / 1 / 1 15.4 414.5 2022 / 2 / 1 14.77 386.5 2022 / 3 / 1 18.45 239.45

[0040] 3. According to Calculate the radius of the crossflow channel (d), where μ is the fluid viscosity, L is the distance between the injection well and the oil production well, and a is the absolute value of the slope of the fitting relationship between the injection volume of the injection well and the production pressure difference. Then, according to the formula V = πd 2 L is used to calculate the volume (V) of the crossflow channel, where d is the radius of the crossflow channel and L is the distance between the injection well and the oil production well.

[0041] The distance L between Well 5-12 and Well H7-126 is 427 m, the fluid viscosity μ is 0.2 mPa.s, and the value of a is 31.66. According to the radius calculation formula, the radius of the crossflow channel is 9.1 m, and according to the volume calculation formula, the volume of the crossflow channel is 111309 m 3 .

[0042] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for quantitatively characterizing crossflow channels in water-flooded oil reservoirs, characterized by: The following steps are involved: (1) According to the water injection volume of the injection wells and the water production volume of the oil production wells in the target area, the rank correlation coefficient between the injection wells and the oil production wells is determined to determine whether there is a crossflow channel between the two wells; (2) Calculate the radius (d) of the crossflow channel according to the following formula: Wherein, μ is the fluid viscosity, L is the distance between the injection well and the production well, and a is the absolute value of the slope of the fitting relationship between the injection volume of the injection well and the production pressure difference; (3) Calculate the volume of the crossflow channel using Poiseuille's law and the radius.

2. The method for quantitatively characterizing crossflow channels in a water-flooding reservoir according to claim 1, wherein: In step (1), the rank correlation coefficient (r) is calculated according to the following formula: Among them, x is the water injection volume of the injection well, and y is the water production volume of the oil well.

3. The method for quantitatively characterizing crossflow channels in a water-flooding reservoir according to claim 2, wherein: When the rank correlation coefficient is less than 0.2, there is no crossflow channel between the two wells; when the rank correlation coefficient is greater than 0.2, it indicates that there is a crossflow channel between the two wells.

4. The method for quantitatively characterizing crossflow channels in a water-flooding reservoir according to claim 1, wherein: In step (3), the volume (V) of the crossflow channel is calculated according to the following formula: V = πd 2 L, where d is the radius of the crossflow channel and L is the distance between the injection well and the oil production well.

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