Method and system for predicting water breakthrough time of high-dip-angle edge-bottom water reservoir with partition plate

Abstract

The invention provides a method and a system for predicting water breakthrough time of an edge-bottom water reservoir with a partition plate and a high dip angle. The method comprises the following steps: (1) acquiring actual production data of the reservoir; (2) determining a water phase seepage velocity and an oil well critical yield; and (3) predicting the water breakthrough time based on the water phase seepage velocity and the oil well critical yield. And (4) sensitivity analysis: considering the influence of different conditions on the reservoir water breakthrough time. The water breakthrough time prediction method and system provided by the invention can be used for optimizing the position and size design of the partition plate, and have certain guiding significance for actual edge-bottom water reservoir development.

Description

Technical Field

[0001] The present invention relates to the application field of oil and gas reservoir technology, and in particular to a method for predicting water breakthrough time of a high-inclination edge and bottom water oil reservoir with a baffle. Background Art

[0002] High-inclination edge-water reservoirs are complex oil and gas fields, and their water drive mechanisms significantly impact reservoir production performance. During the development of edge-water reservoirs, problems such as bottom water coning and edge water tongue are common. Once water breaks through in a production well, the water cut can rise dramatically, severely impacting production. Traditional methods for predicting water breakthrough time often overlook the influence of reservoir baffles, resulting in inaccurate predictions and negatively impacting the economic benefits of the oilfield.

[0003] Domestic and foreign scholars have achieved remarkable results in their research on bottom-water reservoirs, especially in the prediction methods for bottom-water coning and water breakthrough time. The "partition theory" proposed by Li Chuanliang et al. has been widely used in the development of bottom-water gas reservoirs without baffles and has achieved remarkable results. In addition, based on the oil-water two-phase seepage theory and the flow laws of fluids in porous media, researchers have established physical models and derived formulas for the water breakthrough time of horizontal wells in bottom-water reservoirs with baffles. These studies have greatly improved the accuracy of predictions. However, for reservoirs with high inclination angles and complex geological structures, existing prediction methods still face challenges and need to further consider multiple factors such as geological structure, fluid properties, and development strategies.

[0004] In practical applications, predicting the water breakthrough time in high-angle, edge-bottom-water reservoirs with baffles is crucial for guiding oilfield development and improving oil recovery. Mathematical methods and reservoir numerical simulations can better understand the mechanism of edge-bottom-water coning, enabling the development of effective water control and development strategies. For example, the use of artificial baffles can significantly delay the onset of bottom-water coning in horizontal wells. Factors such as baffle radius, water avoidance height, and well production can all influence water breakthrough time. Therefore, accurate prediction methods and rational development strategies are crucial for improving reservoir management efficiency and economic benefits. Therefore, proposing a water breakthrough time prediction method and system for high-angle, edge-bottom-water reservoirs that considers the influence of baffles is of great practical significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for predicting water breakthrough time in a high-inclination edge-bottom water reservoir with baffles, which can be used to optimize the position and size design of the baffles and has certain guiding significance for improving the development efficiency of actual edge-bottom water reservoirs.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In a first aspect, a method for predicting water breakthrough time in a high-angle bottom water reservoir with a baffle is provided, wherein the calculation method comprises the following steps:

[0008] S1: Based on reservoir logging data and production dynamics, obtain actual production data of high-angle bottom water reservoirs with baffles

[0009] S2: Determine the water phase seepage velocity and critical oil well production based on the edge and bottom water cone velocity and movement distance

[0010] S3: Prediction of water breakthrough time in high-angle bottom water reservoirs with baffles based on water phase seepage velocity and critical oil well production

[0011] S4: Conduct sensitivity analysis on the reservoir, considering the impact of water avoidance height, baffle length, oil well production, vertical permeability coefficient, etc. on the reservoir

[0012] Furthermore, the data collected in S1 include static data: reservoir water avoidance height, formation crude oil viscosity, water phase viscosity, porosity, formation vertical permeability coefficient, formation dip, bottom hole drainage radius, and wellbore radius.

[0013] Furthermore, the data collected in S1 include dynamic data: initial production of the oil well, production pressure difference, and the length of the interlayer equivalent to the partition.

[0014] Furthermore, the vertical permeability coefficient α of the formation collected in embodiment S1 is defined as the vertical permeability coefficient k v and horizontal permeability k h The ratio of , that is:

[0015]

[0016] Where k v is the vertical permeability of the formation; k h is the horizontal permeability of the formation.

[0017] Furthermore, in the selected implementation S2, the following assumptions are made: (1) the reservoir is of equal thickness and homogeneous, and the water piston displaces the oil phase to flow to the bottom of the well; (2) the density and viscosity of the oil phase and the water phase are constant during the seepage process; (3) both the oil and water phases obey Darcy seepage; (4) gravity is considered and the capillary force is ignored; (5) the wellbore radius is much smaller than the edge and bottom water propulsion path, and the flow of oil and water in the wellbore is ignored; (6) the original oil-water interface at the oil layer boundary is a horizontal plane, with the oil layer above and the water layer below; and (7) the temperature in the reservoir is constant.

[0018] Furthermore, the seepage velocity of water particles in S2 in the oil layer is:

[0019]

[0020] Where, v m is the seepage velocity of water particles in the oil layer; k h is the horizontal permeability; Δp is the pressure difference during the advancement of water particles in the oil layer; μw is the viscosity of the water phase; α is the vertical permeability coefficient of the formation; φ is the matrix porosity; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; L is the partition length; β is the formation dip.

[0021] Furthermore, the oil well production during stable production is:

[0022]

[0023] Among them, q0 is the output of the oil well during stable production; k h is the horizontal permeability of the formation; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; μ0 is the viscosity of the oil phase; r e is the bottom hole drainage radius; r b is the radial distance of formation water flow.

[0024] Furthermore, according to the seepage theory, the seepage velocity of water particles on the partition is:

[0025]

[0026] Among them, v L is the seepage velocity of water particles on the partition; q0 is the output of the oil well during stable production; A L It is the area where water particles propel on the partition.

[0027] Furthermore, the displacement A of the water particle during its advancement on the partition L The calculation formula is:

[0028] A L =2πr(HL sinβ)φ

[0029] Among them, A L is the area of ​​water particles advancing on the partition; H is the water avoidance height, that is, the height between the oil well and the oil-water interface; L is the length of the partition; β is the formation inclination; r is the radius of the path of water particles advancing on the partition.

[0030] Furthermore, the seepage velocity of water particles on the partition is

[0031]

[0032] Furthermore, in S3, the formula for the advancement time of edge and bottom water in the oil layer considering the influence of interlayers is:

[0033]

[0034] Where t1 is the time for the edge and bottom water to advance in the oil layer considering the influence of interlayer; H is the vertical distance from the bottom of the well to the partition; μ Ris the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; r b is the radial distance that formation water flows.

[0035] Among them, the water-oil viscosity ratio is:

[0036]

[0037] Where μ w is the viscosity of the water phase, μ0 is the viscosity of the oil phase

[0038] Furthermore, in S3, the formula for the advancement time of the edge and bottom water on the diaphragm considering the influence of the interlayer is:

[0039]

[0040] Where t2 is the time it takes for the edge and bottom water to advance on the baffle considering the influence of interlayers; H is the vertical distance from the bottom of the well to the baffle; L is the baffle length; β is the formation dip; φ is the matrix porosity; and q0 is the initial production rate of the well.

[0041] Furthermore, in S3, the water breakthrough time prediction formula for the baffled bottom water reservoir considering the influence of formation dip is:

[0042]

[0043] Where, t is the water breakthrough time of the bottom water reservoir with baffles considering the influence of interlayer; H is the vertical distance from the bottom of the well to the baffle; μ R is the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; r b is the radial distance that formation water flows.

[0044] Furthermore, in S4, the present invention explores the effects of baffle length and yield, water avoidance height and yield, vertical permeability coefficient and yield on water breakthrough time. Figure 3 、 4 、5.

[0045] Figure 3 The following is a schematic diagram showing the effect of different production rates and baffle lengths on the water breakthrough time of high-angle bottom water reservoirs with baffles. Figure 3It can be seen that when the baffle length is less than 200m, the time to water breakthrough increases, while when it is greater than 200m, the time to water breakthrough decreases, and the curves of water breakthrough time and production rate are almost parallel. This is because when the baffle length is small, under the same production rate, as the baffle length increases, the seepage resistance of the edge and bottom water gradually increases, the shielding effect on the edge and bottom water becomes more significant, and the time to water breakthrough gradually increases. However, when the baffle length is large, the seepage velocity is more affected, resulting in an earlier water breakthrough time. Higher production rates lead to earlier water breakthrough in the oil well. This is because under the same baffle length, higher production rates and greater production pressure differentials lead to earlier breakthrough of the edge and bottom water to the bottom of the well. However, at high production rates, changes in baffle length have little effect on the time to water breakthrough in the oil well.

[0046] Figure 4 The following is a schematic diagram showing the effect of different production rates and water avoidance heights on the water breakthrough time of high-angle bottom water reservoirs with baffles. Figure 4 It can be seen that when the baffle length is 200m, the greater the water avoidance height, the later the water breakthrough time. This is because, under the same production conditions, as the water avoidance height increases, the seepage resistance of the edge and bottom water gradually increases, which helps reduce the bottom water coning and edge water advance speed, and the water breakthrough time of the oil well gradually increases, and the extension rate becomes increasingly larger. Higher production rates are associated with earlier water breakthrough in the oil well. This is because, under the same water avoidance height, higher production rates and greater production pressure differentials lead to earlier breakthrough of the edge and bottom water to the bottom of the well. However, at high production rates, changes in the water avoidance height have little effect on the water breakthrough time of the oil well.

[0047] Figure 5 The figure is a schematic diagram showing the effect of different vertical permeability coefficients on the water breakthrough time of a high-angle bottom water reservoir with baffles. Figure 5 As can be seen, as the vertical permeability coefficient increases, water breakthrough occurs earlier. This is because the vertical permeability coefficient of the formation refers to the fluid's ability to penetrate in the vertical direction, which directly affects the speed and range of pressure propagation during waterflooding. As the vertical permeability coefficient decreases, the fluid's flow resistance in the low-permeability layer increases, and the pressure propagation speed slows down, thus delaying water breakthrough.

[0048] The present invention divides the bottom water migration trajectory of high-angle edge-bottom water reservoirs under the influence of interlayers into a combination mode of "bottom water coning + edge water advancement" and divides it into two seepage fields. The different migration paths lead to different seepage velocities of bottom water coning and edge water advancement. Interlayers are equivalent to baffles, and the influence of pressure difference is not ignored during the water phase flow process. The advancement time formulas of edge-bottom water on the oil layer and baffles considering the influence of interlayers are derived respectively, and then a water breakthrough time prediction model for high-angle edge-bottom water reservoirs considering the influence of interlayers is obtained. Combined with the reservoir production data obtained on site, the water breakthrough time of high-angle edge-bottom water reservoirs with baffles is accurately predicted. This method establishes separate water breakthrough time prediction formulas based on the two seepage fields divided by the complex water inflow path of the reservoir, which can accurately reflect the actual seepage situation of the reservoir. This method is fast to calculate, and the water breakthrough time calculated by this method is highly accurate. It has certain guiding value for improving the recovery rate of high-angle edge-bottom water reservoirs with baffles.

[0049] Beneficial effects:

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The bottom water migration trajectory in high-angle edge-water reservoirs, influenced by interlayers, is split into two seepage fields, each characterized by a combination of "bottom water coning + edge water advancement." The different migration paths lead to different seepage velocities for bottom water coning and edge water advancement. By equating interlayers to baffles and not neglecting the influence of pressure differentials during water flow, formulas for the advancement time of edge-water in the oil layer and baffles, respectively, are derived, considering the influence of interlayers. This leads to a model for predicting water breakthrough time in high-angle edge-water reservoirs with baffles, which is then combined with field-acquired reservoir production data to accurately predict water breakthrough time in high-angle edge-water reservoirs with baffles. This method establishes separate water breakthrough time prediction formulas based on the two seepage fields divided by the reservoir's complex water inflow pathways. This method accurately reflects the actual reservoir seepage conditions, is fast, and the water breakthrough time calculated by this method is highly accurate. It has certain guiding value for improving the recovery factor of high-angle edge-water reservoirs with baffles. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a flow chart of a method and system for predicting water breakthrough time in a high-angle bottom water reservoir with a baffle constructed in an embodiment of the present invention;

[0053] Figure 2 A diagram of a high-angle bottom water reservoir model with baffles established in an embodiment of the present invention;

[0054] Figure 3 Schematic diagram of the effect of different production rates and baffle lengths on water breakthrough time in high-angle bottom water reservoirs with baffles;

[0055] Figure 4Schematic diagram of the effect of different production rates and water avoidance heights on the water breakthrough time of high-angle bottom water reservoirs with baffles;

[0056] Figure 5 Schematic diagram of the influence of vertical permeability coefficient of formation on water breakthrough time of high-angle bottom water reservoir with baffle. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0058] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0059] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0060] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0061] Example:

[0062] This embodiment provides a method for predicting water breakthrough time in a high-angle edge-bottom water reservoir with baffles, the steps of which are as follows:

[0063] In the established implementation method, the data collected in S1 includes static data: reservoir water avoidance height, formation crude oil viscosity, water phase viscosity, porosity, formation vertical permeability coefficient, formation dip, bottom hole drainage radius, and wellbore radius.

[0064] In the established embodiment, the data collected in S1 include dynamic data: initial production of the oil well, production pressure difference, and the length of the interlayer equivalent to the partition.

[0065] Furthermore, the data collected in S1 include static data: reservoir water avoidance height, formation crude oil viscosity, water phase viscosity, porosity, formation vertical permeability coefficient, formation dip, bottom hole drainage radius, and wellbore radius.

[0066] Furthermore, the data collected in S1 include dynamic data: initial production of the oil well, production pressure difference, and the length of the interlayer equivalent to the partition.

[0067] Furthermore, the vertical permeability coefficient α of the formation collected in embodiment S1 is defined as the vertical permeability coefficient k v and horizontal permeability k h The ratio of , that is:

[0068]

[0069] Where k v is the vertical permeability of the formation; k h is the horizontal permeability of the formation.

[0070] Furthermore, in the selected implementation S2, the following assumptions are made: (1) the reservoir is of equal thickness and homogeneous, and the water piston displaces the oil phase to flow to the bottom of the well; (2) the density and viscosity of the oil phase and the water phase are constant during the seepage process; (3) both the oil and water phases obey Darcy seepage; (4) gravity is considered and the capillary force is ignored; (5) the wellbore radius is much smaller than the edge and bottom water propulsion path, and the flow of oil and water in the wellbore is ignored; (6) the original oil-water interface at the oil layer boundary is a horizontal plane, with the oil layer above and the water layer below; and (7) the temperature in the reservoir is constant.

[0071] Furthermore, according to the seepage theory and Darcy's law, the seepage velocity of water particles in the oil layer is:

[0072]

[0073] Where, v m is the seepage velocity of water particles in the oil layer, m / s; k h is the horizontal permeability, 10 -3 μm 2 ; Δp is the pressure difference of water particles in the oil layer during advancement, MPa; μ w is the viscosity of the water phase, mPa·s; Δz is the displacement of the water particle during the advancement of the oil layer, m.

[0074] Furthermore, the horizontal permeability k h The calculation formula is:

[0075]

[0076] Among them, k v is the vertical permeability of the formation, 10 -3 μm 2 ;k h is the horizontal permeability of the formation, 10 -3 μm 2 ; α is the vertical permeability coefficient of the formation.

[0077] Furthermore, the aqueous phase viscosity μ w The calculation formula is:

[0078] μ w =φμ(3)

[0079] Where μ w is the water phase viscosity, mPa·s; φ is the matrix porosity; μ is the formation viscosity, mPa·s.

[0080] Furthermore, the displacement △z of the water particle in the oil layer is:

[0081]

[0082] Where H is the vertical distance from the bottom of the well to the partition, m; L is the partition length, m; β is the formation dip, °.

[0083] Combining equations (1)(2)(3)(4), we can get the seepage velocity of water particles in the oil layer as:

[0084]

[0085] Where, v m is the seepage velocity of water particles in the oil layer; k h is the horizontal permeability; Δp is the pressure difference during the advancement of water particles in the oil layer; μ w is the viscosity of the water phase; α is the vertical permeability coefficient of the formation; φ is the matrix porosity; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; L is the partition length; β is the formation dip.

[0086] Furthermore, the oil well production during stable production is:

[0087]

[0088] Among them, q0 is the output of the oil well during stable production; k h is the horizontal permeability of the formation; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; μ0 is the viscosity of the oil phase; r e is the bottom hole drainage radius; r b is the radial distance of formation water flow.

[0089] Among them, the radial distance r of formation water flow b :

[0090] r b =L cosβ (7)

[0091] Furthermore, according to the seepage theory, the seepage velocity of water particles on the partition is:

[0092]

[0093] Among them, v L is the seepage velocity of water particles on the partition; q0 is the output of the oil well during stable production; A L It is the area where water particles propel on the partition.

[0094] Furthermore, the displacement A of the water particle during its advancement on the partition L The calculation formula is:

[0095] A L =2πr(HL sinβ)φ (9)

[0096] Among them, A L is the area of ​​water particles advancing on the partition; H is the water avoidance height, that is, the height between the oil well and the oil-water interface; L is the length of the partition; β is the formation inclination; r is the radius of the path of water particles advancing on the partition.

[0097] The combined equations (8) and (9) show that the seepage velocity of the water particle on the partition is

[0098]

[0099] S3: Based on the edge and bottom water coning velocity and critical production, obtain the formula for the advancement time of edge and bottom water in the oil layer considering the influence of interlayers.

[0100] First, a reservoir model with edge and bottom water considering the influence of interlayers is constructed, such as Figure 2 As shown in the figure. The formation has a certain dip angle, denoted as β. The interlayer is equivalent to a baffle of length L, with the baffle's ends denoted as points b and c. The baffle is located above the reservoir, the bottom water is below the reservoir, and the oil well is above the reservoir. The height from the bottom of the well to the oil-water interface is H, and the vertical distance from the bottom of the well to the baffle is h. Considering the oil-water interface as a straight line, water point a cones to point b after time t1, propagates along the baffle to point c after time t2, and then flows through the wellbore into the oil well at point d. However, due to the small wellbore radius, the propagation path of the water point is negligible. The above is the water breakthrough time for a baffled bottom water reservoir.

[0101] Combining equations (5), (6), and (7), the formula for calculating the breakthrough time t1 of the edge and bottom water in the oil layer considering the influence of the interlayer is:

[0102]

[0103] Where t1 is the time for the edge and bottom water to advance in the oil layer considering the influence of interlayer; H is the vertical distance from the bottom of the well to the partition; μ R is the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; rb is the radial distance that formation water flows.

[0104] Among them, the water-oil viscosity ratio is:

[0105]

[0106] Where μ w is the viscosity of the water phase, μ0 is the viscosity of the oil phase

[0107] S3: Based on the cone penetration speed and movement distance of the edge and bottom water, the formula for the advancement time of the edge and bottom water on the partition considering the influence of the interlayer is obtained.

[0108] Integrating formula (10), we get

[0109]

[0110] The integral result is:

[0111]

[0112] Among them, the wellbore radius rw is too small and can be ignored.

[0113] Furthermore, in S3, the formula for the advancement time of the edge and bottom water on the diaphragm considering the influence of the interlayer is:

[0114]

[0115] Where t2 is the time it takes for the edge and bottom water to advance on the baffle considering the influence of interlayers; H is the vertical distance from the bottom of the well to the baffle; L is the baffle length; β is the formation dip; φ is the matrix porosity; and q0 is the initial production rate of the well.

[0116] S3: Add the formula for the advancement time of edge and bottom water in the oil layer and the formula for the advancement time on the baffle to obtain the water breakthrough time prediction formula for high-angle baffled edge and bottom water reservoirs considering the influence of interlayers:

[0117]

[0118] Where, t is the water breakthrough time of the bottom water reservoir with baffles considering the influence of interlayer; H is the vertical distance from the bottom of the well to the baffle; μ R is the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; r b is the radial distance that formation water flows.

[0119] Furthermore, in S4, the present invention explores the effects of baffle length and yield, water avoidance height and yield, vertical permeability coefficient and yield on water breakthrough time. Figure 3 、 4 、5.

[0120] Figure 3 The following is a schematic diagram showing the effect of different production rates and baffle lengths on the water breakthrough time of high-angle bottom water reservoirs with baffles. Figure 3 It can be seen that when the baffle length is less than 200m, the time to water breakthrough increases, while when it is greater than 200m, the time to water breakthrough decreases, and the curves of water breakthrough time and production rate are almost parallel. This is because when the baffle length is small, under the same production rate, as the baffle length increases, the seepage resistance of the edge and bottom water gradually increases, the shielding effect on the edge and bottom water becomes more significant, and the time to water breakthrough gradually increases. However, when the baffle length is large, the seepage velocity is more affected, resulting in an earlier water breakthrough time. Higher production rates lead to earlier water breakthrough in the oil well. This is because under the same baffle length, higher production rates and greater production pressure differentials lead to earlier breakthrough of the edge and bottom water to the bottom of the well. However, at high production rates, changes in baffle length have little effect on the time to water breakthrough in the oil well.

[0121] Figure 4 The following is a schematic diagram showing the effect of different production rates and water avoidance heights on the water breakthrough time of high-angle bottom water reservoirs with baffles. Figure 4 It can be seen that when the baffle length is 200m, the greater the water avoidance height, the later the water breakthrough time. This is because, under the same production conditions, as the water avoidance height increases, the seepage resistance of the edge and bottom water gradually increases, which helps reduce the bottom water coning and edge water advance speed, and the water breakthrough time of the oil well gradually increases, and the extension rate becomes increasingly larger. Higher production rates are associated with earlier water breakthrough in the oil well. This is because, under the same water avoidance height, higher production rates and greater production pressure differentials lead to earlier breakthrough of the edge and bottom water to the bottom of the well. However, at high production rates, changes in the water avoidance height have little effect on the water breakthrough time of the oil well.

[0122] Figure 5 The figure is a schematic diagram showing the effect of different vertical permeability coefficients on the water breakthrough time of a high-angle bottom water reservoir with baffles. Figure 5 As can be seen, as the vertical permeability coefficient increases, water breakthrough occurs earlier. This is because the vertical permeability coefficient of the formation refers to the fluid's ability to penetrate in the vertical direction, which directly affects the speed and range of pressure propagation during waterflooding. As the vertical permeability coefficient decreases, the fluid's flow resistance in the low-permeability layer increases, and the pressure propagation speed slows down, thus delaying water breakthrough.

[0123] Example 1:

[0124] A high-inclination oil reservoir with baffles in China has an inclination of 1.2-15.7° for edge-bottom water, an oil phase viscosity of 0.58-0.94 mPa.s, an average porosity of 0.218, and an average permeability of 363 mD. The initial production of a main oil well in this reservoir is 1021 m 3, inclination 2°, bottom hole drainage radius 500m, oil-water viscosity ratio is 2, porosity 0.236, vertical permeability coefficient of formation 0.67, and the interlayer is equivalent to an impermeable partition with a length of 200m.

[0125] According to the water breakthrough time prediction method for high-inclination bottom water reservoirs with baffles provided by an embodiment of the present invention, the water breakthrough time of the main well is calculated to be 94.95 days. The actual water breakthrough time of the well is 94 days, with an error of only 1.01%, indicating that this method has a certain accuracy in predicting water breakthrough time and has practical guiding significance.

[0126] In specific implementation, the S3 predicted water breakthrough time section mainly includes:

[0127] According to the analysis of the seepage direction, the displacement of the water particle in the oil layer advancement process is calculated according to formula (4).

[0128] According to the seepage theory and Darcy's law, the calculation formula for the seepage velocity of water particles in the oil layer is determined according to formula (5).

[0129] The output calculation formula when the water quality point is in stable production is determined according to formula (6).

[0130] According to the seepage direction and seepage path, the displacement of the water particle on the partition is determined according to formula (7).

[0131] The calculation formula for the seepage velocity of water particles on the partition is determined according to formula (8).

[0132] According to the formula of water particle propulsion displacement and water particle seepage velocity in the oil layer, the formula of water particle propulsion time in the oil layer is determined according to formula (11).

[0133] According to the calculation formula of the seepage velocity of water particles on the partition, the calculation formula of the time when water particles appear on the partition is determined according to formula (15).

[0134] According to the time of edge and bottom water advancing on the oil layer and the baffle, the water breakthrough time of the high-inclination baffle edge and bottom water reservoir is predicted according to formula (16).

[0135] The present invention divides the bottom water migration trajectory of high-angle edge-bottom water reservoirs under the influence of interlayers into a combination mode of "bottom water coning + edge water advancement" and divides it into two seepage fields. The different migration paths lead to different seepage velocities of bottom water coning and edge water advancement. Interlayers are equivalent to baffles, and the influence of pressure difference is not ignored during the water phase flow process. The advancement time formulas of edge-bottom water on the oil layer and baffles considering the influence of interlayers are derived respectively, and then a water breakthrough time prediction model for high-angle edge-bottom water reservoirs considering the influence of interlayers is obtained. Combined with the reservoir production data obtained on site, the water breakthrough time of high-angle edge-bottom water reservoirs with baffles is accurately predicted. This method establishes separate water breakthrough time prediction formulas based on the two seepage fields divided by the complex water inflow path of the reservoir, which can accurately reflect the actual seepage situation of the reservoir. This method is fast to calculate, and the water breakthrough time calculated by this method is highly accurate. It has certain guiding value for improving the recovery rate of high-angle edge-bottom water reservoirs with baffles.

[0136] The above description does not limit the present invention in any form. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method and system for predicting water breakthrough time in a high-angle bottom water reservoir with baffles, characterized in that: The method comprises: S1: Based on reservoir logging data and production dynamics, obtain actual production data of high-angle bottom water reservoirs with baffles S2: Determine the water phase seepage velocity and critical oil well production based on the edge and bottom water cone advance velocity and movement distance S3: Prediction of water breakthrough time in high-angle bottom water reservoirs with baffles based on water phase seepage velocity and critical oil well production S4: Conduct sensitivity analysis on the reservoir, considering the impact of water avoidance height, baffle length, oil well production, vertical permeability coefficient, etc. on the reservoir.

2. A method and system for predicting water breakthrough time in a high-angle bottom water reservoir with baffles as claimed in claim 1, characterized in that: The data collected in step S1 include static data: reservoir water avoidance height, formation crude oil viscosity, water phase viscosity, porosity, formation vertical permeability coefficient, formation inclination, bottom hole drainage radius, wellbore radius; the data collected in S1 include dynamic data: initial production of oil well, production pressure difference, and the length of the interlayer equivalent to the partition; the formation vertical permeability coefficient α collected in S1 is defined as the formation vertical permeability k v With horizontal permeability k h The ratio of, that is: In the formula, k v is the vertical permeability of the formation; k h is the horizontal permeability of the formation.

3. A method and system for predicting water breakthrough time in a high-angle bottom water reservoir with baffles as claimed in claim 1, characterized in that: The following assumptions are made in step S2: (1) the reservoir is of equal thickness and homogeneous, and the water piston drives the oil phase to flow to the bottom of the well; (2) the density and viscosity of the oil phase and the water phase are constant during the seepage process; (3) both the oil and water phases obey Darcy seepage; (4) gravity is considered and the capillary force is ignored; (5) the wellbore radius is much smaller than the edge and bottom water propulsion path, and the flow of oil and water in the wellbore is ignored; (6) the original oil-water interface at the boundary of the oil layer is a horizontal plane, with the oil layer above and the water layer below; (7) the temperature in the reservoir is constant. The seepage velocity of water particles in S2 in the oil layer is: In the formula, v m is the seepage velocity of water particles in the oil layer; k h is the horizontal permeability; Δp is the pressure difference of water particles in the oil layer; μ w is the water phase viscosity; α is the vertical permeability coefficient of the formation; φ is the matrix porosity; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; L is the baffle length; β is the formation dip angle, The oil well production during stable production is: Among them, q0 is the output of the oil well during stable production; k h is the horizontal permeability of the formation; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; μ0 is the viscosity of the oil phase; r e is the bottom hole leakage radius; r b is the radial distance of formation water flow According to the seepage theory, the seepage velocity of water particles on the partition is: Among them, v L is the seepage velocity of water particles on the partition; q0 is the output of the oil well during stable production; A L is the area of ​​water particles advancing on the partition, The displacement A of the water particle during its advancement on the partition L The calculation formula is: A L =2πr(H-Lsinβ)φ Among them, A L is the area of ​​water particles advancing on the baffle; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; L is the length of the baffle; β is the formation inclination; r is the radius of the path of water particles advancing on the baffle, The seepage velocity of water particles on the partition is Among them, v L is the seepage velocity of water particles on the baffle; q0 is the output of the oil well during stable production; H is the water avoidance height, that is, the height of the oil well from the oil-water interface; L is the baffle length; β is the formation inclination.

4. A method and system for predicting water breakthrough time in a high-angle bottom water reservoir with baffles as claimed in claim 1, characterized in that: In step S3, the formula for the advancement time of the edge and bottom water in the oil layer considering the influence of the interlayer is: Where t1 is the advancing time of the edge and bottom water in the oil layer considering the influence of the interlayer; H is the vertical distance from the bottom of the well to the partition; μ R is the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip angle; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; r b is the radial distance that the formation water flows Among them, the water-oil viscosity ratio is: In the formula, μ w is the viscosity of the water phase, μ0 is the viscosity of the oil phase, In S3, the formula for the advancement time of the edge and bottom water on the partition considering the influence of the interlayer is: Where, t2 is the advancement time of the edge and bottom water on the baffle considering the influence of the interlayer; H is the vertical distance from the bottom of the well to the baffle; L is the length of the baffle; β is the formation dip; φ is the matrix porosity; q0 is the initial production of the oil well. In S3, the water breakthrough time prediction formula for the edge and bottom water reservoir with baffle considering the influence of the formation dip is: Where, t is the water breakthrough time of the bottom water reservoir with baffles considering the influence of interlayers; H is the vertical distance from the bottom of the well to the baffle; μ R is the water-oil viscosity ratio; φ is the matrix porosity; L is the baffle length; β is the formation dip angle; α is the vertical permeability coefficient of the formation; q0 is the initial production of the oil well; r e is the bottom hole drainage radius; r b is the radial distance that formation water flows.

5. A method and system for predicting water breakthrough time in a high-angle bottom water reservoir with baffles as claimed in claim 1, characterized in that: In step S4, the present invention discusses the effects of baffle length and production, water avoidance height and production, vertical permeability coefficient and production on water breakthrough time.

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