Method and system for determining dosage of water shutoff agent for clastic rock oil reservoir

Abstract

The method comprises the steps that before the water plugging agent is injected, the formation pressure and the yield of an oil well in the elastic flooding stage and the water flooding stage of a target reservoir are collected respectively, so that the shielding pressure difference representing the plugging strength needed by a water flow dominant channel in the target reservoir is obtained; the dimensionless gel forming length represents the proportion of the actual gel forming length to the theoretical gel forming length of the to-be-injected water plugging agent in the target reservoir, and the gel forming breakthrough pressure gradient represents the gel plugging strength in the migration process; and an ellipsoid model of the target reservoir is constructed, and in combination with the correlation among the shielding pressure difference, the dimensionless gelling length, the gelling breakthrough pressure gradient and the theoretical gelling length, the dosage of the current water shutoff agent to be injected is obtained. The quantitative design of the dosage of the water plugging agent for the clastic rock oil reservoir is truly, objectively and accurately realized, and a basis is provided for optimization of a single-well water plugging process.

Description

Technical Field

[0001] The invention belongs to the technical field of oil reservoir water plugging development, and in particular relates to a method and a system for determining the dosage of a water plugging agent in a clastic rock oil reservoir. Background Art

[0002] Currently, high water cuts in oil wells caused by water channeling and bottom water coning have become the primary drivers of natural oil production decline in Tahe clastic reservoirs. Therefore, finding ways to exploit the remaining oil untouched by water injection has become a key issue facing current development efforts.

[0003] Compared to conventional clastic reservoirs, the Tahe clastic reservoir is characterized by a deep burial depth (4,600 m), strong bottom water content (water-oil volume ratio greater than 100:1), and excellent physical properties (porosity Φ = 22%, permeability K = 899 mD). This massive sandstone reservoir, deposited in a braided river delta, features medium-porosity, medium-to-high permeability, and strong bottom water. Waterflooding charts show that the recovery efficiency of this bottom-water sandstone reservoir has reached 37% in recent years, with an average natural decline of 17.5% and a comprehensive decline of -1.8%. This variability in recovery efficiency is primarily due to large-scale intervention measures to enhance well-controlled reserve production, primarily through water plugging and rhythmic section tapping. However, after multiple rounds of water plugging, the oil production rate decreases. Furthermore, the residual oil level gradually decreases after multiple rounds of water plugging, impacting production. In addition, the existing water plugging agent dosage is mainly calculated using the area method, which does not take into account the dynamic migration characteristics of the water plugging agent in the formation, resulting in inaccurate water plugging agent dosage design, short effective period of some water plugging, and overall low oil increase success rate.

[0004] The dosage of water-plugging agents for clastic rocks can be set using two methods: the area method and the numerical simulation method. The numerical simulation method, based on geological modeling, conducts numerical simulations and analyzes the effect of water-plugging agent dosage on oil recovery to determine the dosage. However, its disadvantages are that the numerical simulation time is long and it is impossible to create a model for each well. The area method, a method primarily used in oil fields, manually determines the water-plugging radius after analyzing reservoir static and dynamic data, and calculates the water-plugging agent dosage based on a formula. However, its disadvantages are that it is not very targeted, does not consider the water-plugging agent mechanism, and cannot be quantitatively designed for the plugging radius. Furthermore, most existing settings for clastic rock water-plugging agent dosage fail to consider the adsorption and shearing of water-plugging agents during dynamic migration in the formation, leaving room for further optimization of the resulting water-plugging agent dosage.

[0005] In summary, there is an urgent need for a quantitative design method for the dosage of water plugging agents based on the dual combination of reservoir geological characteristics and water plugging agent influencing factors to achieve efficient and accurate water plugging, so as to better guide on-site construction and production. Summary of the Invention

[0006] To address the above-mentioned problems, an embodiment of the present invention provides a method for determining the dosage of a water-shutoff agent in a clastic oil reservoir, comprising: before injecting the water-shutoff agent, collecting the formation pressure and oil well production of the target reservoir during the elastic flooding stage and the water flooding stage, respectively, to obtain a shielding pressure difference representing the required plugging strength of the dominant water flow channel in the target reservoir; obtaining a dimensionless gelation length representing the ratio of the actual gelation length of the water-shutoff agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient representing the plugging strength of the colloid during migration; constructing an ellipsoidal model of the target reservoir, and combining the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient, and the theoretical gelation length to obtain the current dosage of the water-shutoff agent to be injected.

[0007] Preferably, the correlation among the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient and the theoretical gelation length is expressed by the following expression:

[0008] ΔP=L0×L 突破 ×L 理论

[0009] Among them, ΔP represents the shielding pressure difference, L0 represents the dimensionless gel length, L 突破 represents the gel breakthrough pressure gradient, L 理论 Indicates the theoretical gel length.

[0010] Preferably, the step of constructing the ellipsoid model of the target reservoir includes: specifying a horizontal radius of the ellipsoid radial section that is in a specific ratio to the vertical depth of the ellipsoid radial section for the ellipsoid model, and using the dimensionless gelation length as the vertical depth of the ellipsoid radial section, thereby forming the ellipsoid model, wherein the ellipsoid model is represented by the following expression:

[0011]

[0012] Where V represents the amount of water plugging agent, a represents the reservoir liquid absorption coefficient, b represents the vertical depth of the ellipsoid radial section, c represents the horizontal radius of the ellipsoid radial section, L represents the length of the water plugging section, and φ represents the effective porosity.

[0013] Preferably, the step of obtaining the shielding pressure difference representing the required blocking strength of the dominant water flow channel in the target reservoir includes: fitting a first energy indicator curve using the formation pressure and the production of the oil well during the elastic drive stage to predict the oil body energy in a state without energy replenishment after the elastic drive stage; and fitting a second energy indicator curve using the formation pressure and the production of the oil well during the water drive stage, and calculating the shielding pressure difference based on the second energy indicator curve in combination with the predicted oil body energy.

[0014] Preferably, the shielding pressure difference is calculated using the following expression:

[0015] ΔP=P W -P1

[0016] Where ΔP represents the shielding pressure difference, P W It represents the formation pressure during the water flooding stage, and P1 represents the predicted oil body energy.

[0017] Preferably, the step of obtaining a dimensionless gelation length representing the proportion of the actual gelation length of the water plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient representing the plugging strength of the colloid during migration, includes: based on an indoor sand filling pipe test, simulating the injection of the water plugging agent into the target reservoir using the water plugging agent to be injected to obtain the dimensionless gelation length; further simulating the migration process of the colloid in the target reservoir in combination with the maximum water flooding pressure when water flooding is continued after the water plugging agent to be injected is gelled, to obtain the gelation breakthrough pressure gradient.

[0018] Preferably, the dimensionless gel length is obtained using the following expression:

[0019]

[0020] Among them, L0 represents the dimensionless gel length, L 实际 Indicates the actual gel length, L 理论 represents the theoretical gelation length, K represents the reservoir permeability, C 聚 represents the colloid concentration, μ 静 It represents the colloid viscosity, and pv represents the colloid pv number.

[0021] Preferably, the gelation breakthrough pressure gradient is obtained using the following expression:

[0022] dP max / dL 突破 =-214.647-0.00029K-0.0136C 聚 +28.5×lnμ 静 +2.9128pv

[0023] Among them, P max Indicates the maximum water drive pressure, L 突破 Represents the gelation breakthrough pressure gradient.

[0024] Preferably, the method further comprises: configuring a plurality of water-plugging agents to be injected with different physical parameters for the target reservoir, and obtaining the dosage of each water-plugging agent respectively, and then adjusting the concentration and plugging radius of each water-plugging agent to be injected according to the dosage, so that the plugging capacity of the water-plugging agent after adjustment is consistent with that before adjustment, and then performing a cost analysis on each adjusted water-plugging agent to obtain the optimal water-plugging agent injection scheme applicable to the current target reservoir.

[0025] On the other hand, the present invention also provides a system for determining the amount of water-plugging agent used in clastic oil reservoirs, the system comprising the following modules: a shielding pressure difference calculation module, which is used to collect the formation pressure and oil well production of the target reservoir in the elastic drive stage and the water drive stage respectively before injecting the water-plugging agent, so as to obtain the shielding pressure difference representing the required plugging strength of the dominant water flow channel in the target reservoir; a gelation parameter calculation module, which is used to obtain the dimensionless gelation length representing the proportion of the actual gelation length of the water-plugging agent to be injected in the target reservoir to the theoretical gelation length, and the gelation breakthrough pressure gradient representing the gelation plugging strength during the migration process; a water-plugging agent dosage generation module, which is used to construct an ellipsoid model of the target reservoir, and combine the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient and the theoretical gelation length to obtain the current amount of the water-plugging agent to be injected.

[0026] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0027] The present invention proposes a method and system for determining the dosage of a water-plugging agent in a clastic rock reservoir. The method first obtains a shielding pressure difference, which represents the required plugging strength of the dominant water flow channel in the target reservoir, based on the formation pressure in the elastic flooding stage and the water flooding stage before the water-plugging agent is injected into the target reservoir and the oil well production. Then, a dimensionless gelation length, which represents the ratio of the actual gelation length of the water-plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient, which represents the plugging strength of the colloid during migration, are obtained experimentally. Finally, an ellipsoidal model of the target reservoir is constructed, and the current dosage of the water-plugging agent to be injected is obtained by combining the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient, and the theoretical gelation length. The present invention combines reservoir geological characteristics with factors affecting water-plugging agents, solving the problems of strong reservoir heterogeneity and large variations in reservoir size in clastic oil reservoirs, which make it impossible to quantitatively design the dosage of water-plugging agents (excessive dosage of water-plugging agents blocks oil production channels, or too little dosage leaves the dominant water flow channels unblocked), resulting in low water-plugging efficiency, short effective duration, and high costs. The invention realizes a true, objective, and accurate quantitative design of the dosage of water-plugging agents in clastic oil reservoirs, providing a basis for optimizing single-well water-plugging processes.

[0028] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 This is a step diagram of a method for determining the dosage of a water plugging agent for a clastic oil reservoir according to an embodiment of the present application.

[0031] Figure 2 This is an example diagram of an energy indicator curve for the method for determining the dosage of water plugging agent in clastic oil reservoirs according to an embodiment of the present application.

[0032] Figure 3 This is a module block diagram of a system for determining the amount of water plugging agent used in clastic oil reservoirs according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings and examples, so that the present invention can fully understand how to apply technical means to solve technical problems and achieve technical effects, and thus implement the invention accordingly. It should be noted that, as long as no conflict exists, the various embodiments of the present invention and the various features of the embodiments can be combined with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0034] Additionally, the steps shown in the flowcharts of the accompanying drawings may be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in an order different from that shown.

[0035] The dosage of water-plugging agents for clastic rocks can be set using two methods: the area method and the numerical simulation method. The numerical simulation method, based on geological modeling, conducts numerical simulations and analyzes the effect of water-plugging agent dosage on oil recovery to determine the dosage. However, its disadvantages are that the numerical simulation time is long and it is impossible to create a model for each well. The area method, a method primarily used in oil fields, manually determines the water-plugging radius after analyzing reservoir static and dynamic data, and calculates the water-plugging agent dosage based on a formula. However, its disadvantages are that it is not very targeted, does not consider the water-plugging agent mechanism, and cannot be quantitatively designed for the plugging radius. Furthermore, most existing settings for clastic rock water-plugging agent dosage fail to consider the adsorption and shearing of water-plugging agents during dynamic migration in the formation, leaving room for further optimization of the resulting water-plugging agent dosage.

[0036] Therefore, to solve the above problems, embodiments of the present invention provide a method and system for determining the dosage of a water-plugging agent in a clastic oil reservoir. The method first obtains a shielding pressure difference, which represents the required plugging strength of the dominant water flow channel in the target reservoir, based on the formation pressure and oil well production during the elastic flooding stage and the water flooding stage before the water-plugging agent is injected into the target reservoir. Then, an experimental method is used to obtain a dimensionless gel length, which represents the ratio of the actual gel length of the water-plugging agent to be injected in the target reservoir to the theoretical gel length, and a gel breakthrough pressure gradient, which represents the gel plugging strength of the colloid during migration. Finally, an ellipsoidal model of the target reservoir is constructed, and the current dosage of the water-plugging agent to be injected is obtained by combining the correlation between the shielding pressure difference, the dimensionless gel length, the gel breakthrough pressure gradient, and the theoretical gel length. The present invention combines reservoir geological characteristics with factors affecting water-plugging agents, solving the problems of strong reservoir heterogeneity and large variations in reservoir size in clastic oil reservoirs, which make it impossible to quantitatively design the dosage of water-plugging agents (excessive dosage of water-plugging agents blocks oil production channels, or too little dosage leaves the dominant water flow channels unblocked), resulting in low water-plugging efficiency, short effective duration, and high costs. The invention realizes a true, objective, and accurate quantitative design of the dosage of water-plugging agents in clastic oil reservoirs, providing a basis for optimizing single-well water-plugging processes.

[0037] Example 1

[0038] Figure 1 This is a step diagram of the method for determining the amount of water plugging agent for clastic oil reservoirs according to the embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0039] like Figure 1 As shown, in step S110, before injecting the water shutoff agent, the formation pressure and oil well production of the target reservoir during the elastic flooding and water flooding stages are collected to obtain a shielding pressure differential that represents the required blocking strength of the dominant water flow channel within the target reservoir. Specifically, before injecting the water shutoff agent, this embodiment collects data on the early natural energy extraction of the oil wells in the target reservoir and extracts the collected data to complete the collection of the formation pressure and oil well production during the elastic flooding stage of the target reservoir. Furthermore, data on the oil wells and the later natural energy extraction of the water flooding stage within the target reservoir are collected and extracted to complete the collection of the formation pressure and oil well production during the water flooding stage of the target reservoir. Subsequently, based on the collected formation pressure and oil well production of the target reservoir during the elastic flooding and water flooding stages, the changes in the oil body energy of the target reservoir during the elastic flooding and water flooding stages are determined. Based on this, a shielding pressure differential is introduced that reflects the required strength of the oil well reservoir to block the dominant water flow channel, that is, represents the required blocking strength of the dominant water flow channel within the target reservoir.

[0040] Next, in the step of obtaining the shielding pressure difference that represents the required sealing strength of the dominant water flow channel in the target reservoir, first, the formation pressure during the elastic flooding stage and the oil well production are used to fit a first energy indicator curve to predict the oil body energy in the state without energy replenishment after the end of the elastic flooding stage. Then, the formation pressure during the water flooding stage and the oil well production are used to fit a second energy indicator curve. Based on this, combined with the predicted oil body energy, the shielding pressure difference is calculated.

[0041] Specifically, in the process of obtaining the shielding pressure difference, this embodiment uses the formation pressure in the elastic flooding stage as the vertical coordinate and the oil well production as the horizontal coordinate, and integrates the formation pressure in the elastic flooding stage and the oil well production into the same coordinate system to fit the first energy indication curve, where P i Represents the initial flow pressure of self-flowing. Similarly, with the formation pressure in the water drive stage as the vertical coordinate and the production of the oil well as the horizontal coordinate, the formation pressure in the water drive stage and the production of the oil well are integrated into the same coordinate system to fit the second energy indication curve. Then, based on the first energy indication curve, it is possible to determine the trend of the production of the oil well with the formation pressure under the condition that the elastic drive stage is over and the water drive stage has not yet started, that is, to predict the energy of the oil body in the state of no energy replenishment after the end of the elastic drive stage. Finally, based on the second energy indication curve, with the production of the oil well as the common point, the first energy indication curve and the second energy indication curve are integrated into the following figure. Figure 2 In the same coordinate system shown ( Figure 2 This is an example diagram of the energy indication curve of the method for determining the amount of water-blocking agent used in clastic oil reservoirs according to an embodiment of the present application), thereby obtaining the energy change of the oil body in the target reservoir before the water-blocking agent is injected according to the integration result, and then obtaining the shielding pressure difference.

[0042] In the embodiment of the present application, the shielding pressure difference is calculated using the following expression:

[0043] ΔP=P W -P1 (1)

[0044] Where ΔP represents the shielding pressure difference, P W It represents the formation pressure during the water flooding stage, and P1 represents the predicted oil body energy.

[0045] Furthermore, in step S120, a dimensionless gelation length, representing the ratio of the actual gelation length of the water-blocking agent to be injected within the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient, representing the plugging strength of the colloid during migration, are obtained. In practical applications, after the water-blocking agent enters the reservoir and forms a polymer gel, the polymer gel undergoes shear and adsorption losses during its long-distance migration within the reservoir, resulting in excessively low viscosity and failure to gel. This, in turn, causes the actual migration length to be less than the theoretical migration length, and accordingly, the actual gelation length is also less than the theoretical gelation length. Therefore, this embodiment obtains a dimensionless gelation length, representing the ratio of the actual gelation length of the water-blocking agent to be injected within the target reservoir to the theoretical gelation length. The dimensionless gelation length, which reflects the correlation between the actual gelation length and the theoretical gelation length, is then used to determine the dosage of the water-blocking agent to be injected, effectively achieving precise design of the water-blocking agent dosage. Furthermore, current conventional pressure gradient tests are generally short core tests, and the measured pressure gradients cannot characterize the plugging strength of the gel after long-distance migration. Therefore, this embodiment introduces the gelation breakthrough pressure gradient representing the gelation plugging strength during the migration process as a characteristic parameter of gelation during the migration process of the gelation to evaluate the gelation strength under dynamic conditions of the reservoir.

[0046] In the step of obtaining the dimensionless gelation length, which represents the ratio of the actual gelation length of the water plugging agent to be injected in the target reservoir to the theoretical gelation length, and the gelation breakthrough pressure gradient, which represents the colloid plugging strength during migration, based on indoor sand filling pipe tests, the water plugging agent injection into the target reservoir is simulated using the water plugging agent to be injected to obtain the dimensionless gelation length. Furthermore, combined with the maximum water flooding pressure when water flooding is continued after the water plugging agent to be injected is gelled, the migration process of the colloid in the target reservoir is simulated to obtain the gelation breakthrough pressure gradient.

[0047] Specifically, to accurately obtain the actual gelation length and actual gelation breakthrough pressure gradient under dynamic conditions after the water plugging agent is injected into the reservoir, this embodiment uses the gel thickness corresponding to 1 / 2 of the maximum gelation breakthrough pressure gradient when water flooding is continued after the water plugging agent is injected as the effective gelation thickness. An indoor sand-filled tube test is performed, and by configuring different experimental parameters to simulate actual injection conditions (such as water plugging agent concentration, water plugging agent dosage, reservoir permeability, reservoir formation pressure, and reservoir porosity), the purpose of simulating water plugging agent injection into the target reservoir using the water plugging agent to be injected is achieved. Data regression is then performed based on the simulation results to obtain the correlation between the dimensionless gelation length and the corresponding actual injection conditions, thereby obtaining the dimensionless gelation length of this embodiment. Similarly, the maximum water flooding pressure when water flooding is continued after the water plugging agent is injected and gelled is added to the experimental parameters, thereby simulating the actual colloid migration conditions including the maximum water flooding pressure. Data regression is performed based on the simulation results to obtain the correlation between the maximum water flooding pressure when water flooding is continued after the water plugging agent is injected and gelled, the gelling breakthrough pressure gradient, and the corresponding actual injection conditions, so as to obtain the gelling breakthrough pressure gradient of this embodiment.

[0048] In one specific embodiment of the present application, the maximum water flooding pressure during water flooding after the water plugging agent has been injected and gelled is the maximum pressure at the injection end during water flooding. The gelling breakthrough pressure gradient is the average pressure gradient corresponding to the actual gelling length during water flooding breakthrough. Furthermore, the colloid migration distance is characterized by the colloid pv number (1 pv = 10 m).

[0049] In the embodiment of the present application, the dimensionless gel length is obtained using the following expression:

[0050]

[0051] Among them, L0 represents the dimensionless gel length, L 实际 Indicates the actual gel length, L 理论 represents the theoretical gelation length, K represents the reservoir permeability, C 聚 represents the colloid concentration, μ 静 It represents the colloid viscosity, and pv represents the colloid pv number.

[0052] In the examples of the present application, the following expression is used to obtain the gelation breakthrough pressure gradient:

[0053] dP max / dL 突破 =-214.647-0.00029K-0.0136C 聚 +28.5×lnμ 静 +2.9128pv (3)

[0054] Among them, P max Indicates the maximum water drive pressure, L 突破 Represents the gelation breakthrough pressure gradient.

[0055] Furthermore, in step S130, an ellipsoidal model of the target reservoir is constructed, and the amount of the water-blocking agent to be injected is obtained by combining the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient, and the theoretical gelation length. Specifically, this embodiment uses the ellipsoidal model to calculate the amount of the water-blocking agent to be injected based on the reservoir physical parameters, the well section length, and the performance characteristics of the plugging agent. However, due to the effect of gravity, in actual applications, the vertical depth of the ellipsoidal radial section of the ellipsoidal model will be smaller than the horizontal radius of the ellipsoidal radial section. Therefore, in order to ensure the plugging strength, this embodiment uses the dimensionless gelation strength as the vertical depth of the ellipsoidal radial section. Therefore, this embodiment establishes a connection between the ellipsoidal model and the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient, and the theoretical gelation length based on the dimensionless gelation strength, thereby obtaining the amount of the water-blocking agent to be injected based on the established connection.

[0056] Next, in the step of constructing an ellipsoidal model of the target reservoir, a horizontal radius of the ellipsoidal radial section that is in a specific ratio to the vertical depth of the ellipsoidal radial section is assigned to the ellipsoidal model, and the dimensionless gel length is used as the vertical depth of the ellipsoidal radial section, thereby forming the ellipsoidal model. The horizontal radius of the ellipsoidal radial section of the ellipsoidal model is a ratio of the vertical depth of the ellipsoidal radial section to the ellipsoidal radial section obtained from indoor experiments. Therefore, in this embodiment, the dimensionless gel length is used as the vertical depth of the ellipsoidal radial section, and the horizontal radius of the ellipsoidal radial section that is in a specific ratio to the vertical depth of the ellipsoidal radial section is assigned to the ellipsoidal model according to the ratio obtained from the aforementioned experiments, thereby forming the ellipsoidal model.

[0057] In the embodiment of the present application, the ellipsoid model is represented by the following expression:

[0058]

[0059] Where V represents the amount of water plugging agent, a represents the reservoir liquid absorption coefficient, b represents the vertical depth of the ellipsoid radial section, c represents the horizontal radius of the ellipsoid radial section, L represents the length of the water plugging section, and φ represents the effective porosity.

[0060] In the embodiment of the present application, the correlation between the shielding pressure difference, the dimensionless gel length, the gel breakthrough pressure gradient and the theoretical gel length is expressed by the following expression:

[0061] ΔP=L0×L 突破 ×L 理论 (5)

[0062] Furthermore, the present invention also configures a plurality of water-blocking agents to be injected with different physical parameters for the target reservoir, and obtains the dosage of each water-blocking agent respectively, and then adjusts the concentration and plugging radius of each water-blocking agent to be injected according to the dosage, so that the plugging ability of the water-blocking agent after adjustment is consistent with that before adjustment, and then performs a cost analysis on each adjusted water-blocking agent to obtain the optimal water-blocking agent injection scheme applicable to the current target reservoir. Specifically, this embodiment configures a plurality of water-blocking agents to be injected with different physical parameters for the same target reservoir, and obtains the dosage of each water-blocking agent using the aforementioned steps. Then, with the plugging ability of the water-blocking agent after adjustment being consistent with that before adjustment as the adjustment target, the concentration and plugging radius of each water-blocking agent to be injected are adjusted. Accordingly, the dosage of each water-blocking agent is recovered after adjustment, and based on the cost consumed by the recovered dosage of each water-blocking agent, the most economical water-blocking agent dosage and corresponding concentration and plugging radius are used as the optimal water-blocking agent injection scheme applicable to the current target reservoir.

[0063] Example 2

[0064] Based on the method for determining the dosage of a water-plugging agent for clastic oil reservoirs described in the first embodiment, an embodiment of the present invention further provides a system for determining the dosage of a water-plugging agent for clastic oil reservoirs. Figure 3 This is a module block diagram of a system for determining the amount of water plugging agent used in clastic oil reservoirs according to an embodiment of the present application.

[0065] like Figure 3 As shown, the system for determining the amount of water plugging agent used in clastic oil reservoirs in the embodiment of the present invention includes: a shielding pressure difference calculation module 31, a gelling parameter calculation module 32 and a water plugging agent amount generation module 33. Specifically, the shielding pressure difference calculation module 31 is implemented according to the method described in step S110 above, and is configured to collect the formation pressure and oil well production of the target reservoir in the elastic flooding stage and the water flooding stage respectively before injecting the water shutoff agent, so as to obtain the shielding pressure difference representing the required plugging strength of the dominant water flow channel in the target reservoir; the gelation parameter calculation module 32 is implemented according to the method described in step S120 above, and is configured to obtain the dimensionless gelation length representing the proportion of the actual gelation length of the water shutoff agent to be injected in the target reservoir to the theoretical gelation length, and the gelation breakthrough pressure gradient representing the gelation plugging strength during the migration process; the water shutoff agent dosage generation module 33 is implemented according to the method described in step S130 above, and is configured to construct an ellipsoid model of the target reservoir, and combine the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient and the theoretical gelation length to obtain the current dosage of the water shutoff agent to be injected.

[0066] The present invention proposes a method and system for determining the dosage of a water-plugging agent in a clastic rock reservoir. The method first obtains a shielding pressure difference, which represents the required plugging strength of the dominant water flow channel in the target reservoir, based on the formation pressure in the elastic flooding stage and the water flooding stage before the water-plugging agent is injected into the target reservoir and the oil well production. Then, a dimensionless gelation length, which represents the ratio of the actual gelation length of the water-plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient, which represents the plugging strength of the colloid during migration, are obtained experimentally. Finally, an ellipsoidal model of the target reservoir is constructed, and the current dosage of the water-plugging agent to be injected is obtained by combining the correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient, and the theoretical gelation length. The present invention combines reservoir geological characteristics with factors affecting water-plugging agents, solving the problems of strong reservoir heterogeneity and large variations in reservoir size in clastic oil reservoirs, which make it impossible to quantitatively design the dosage of water-plugging agents (excessive dosage of water-plugging agents blocks oil production channels, or too little dosage leaves the dominant water flow channels unblocked), resulting in low water-plugging efficiency, short effective duration, and high costs. The invention realizes a true, objective, and accurate quantitative design of the dosage of water-plugging agents in clastic oil reservoirs, providing a basis for optimizing single-well water-plugging processes.

[0067] 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 anyone skilled in the art within the technical scope disclosed in the present invention should be included within 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.

[0068] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

[0069] Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using a general-purpose computing device. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. Alternatively, they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0070] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art may make any modifications and variations in the form and details of the embodiments without departing from the spirit and scope of the present invention. However, the scope of patent protection of the present invention shall remain subject to the scope defined by the appended claims.

Claims

1. A method for determining the dosage of a water plugging agent in a clastic oil reservoir, characterized in that: include: Before injecting the water plugging agent, the formation pressure and oil well production of the target reservoir during the elastic flooding stage and the water flooding stage are collected to obtain the shielding pressure difference representing the required plugging strength of the dominant water flow channel in the target reservoir; Obtaining a dimensionless gelation length representing the ratio of the actual gelation length of the water plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient representing the gelation plugging strength during migration; An ellipsoid model of the target reservoir is constructed, and the amount of the water plugging agent to be injected is obtained by combining the shielding pressure difference, the dimensionless gelation length, the correlation between the gelation breakthrough pressure gradient and the theoretical gelation length.

2. The method according to claim 1, characterized in that The correlation between the shielding pressure difference, the dimensionless gelation length, the gelation breakthrough pressure gradient and the theoretical gelation length is expressed by the following expression: ΔP=L0×L 突破 ×L 理论 Among them, ΔP represents the shielding pressure difference, L0 represents the dimensionless gel length, L 突破 represents the gelation breakthrough pressure gradient, L 理论 Indicates the theoretical gel length.

3. The method according to claim 1 or 2, characterized in that The step of constructing the ellipsoid model of the target reservoir includes: The ellipsoid model is formed by specifying a horizontal radius of the ellipsoid radial section that is in a specific ratio to the vertical depth of the ellipsoid radial section, and using the dimensionless gel length as the vertical depth of the ellipsoid radial section. The ellipsoid model is represented by the following expression: Where V represents the amount of water plugging agent, a represents the reservoir liquid absorption coefficient, b represents the vertical depth of the ellipsoid radial section, c represents the horizontal radius of the ellipsoid radial section, L represents the length of the water plugging section, and φ represents the effective porosity.

4. The method according to any one of claims 1 to 3, characterized in that The step of obtaining the shielding pressure difference indicating the required blocking strength of the dominant water flow channel in the target reservoir includes: The first energy indicator curve is fitted using the formation pressure and oil well production during the elastic flooding phase to predict the oil body energy in the absence of energy replenishment after the elastic flooding phase. The second energy indication curve is fitted using the formation pressure and the production of the oil well during the water flooding stage. Based on this, the shielding pressure difference is calculated in combination with the predicted oil body energy.

5. The method according to claim 4, characterized in that The shielding pressure difference is calculated using the following expression: ΔP=P W -P1 Where ΔP represents the shielding pressure difference, P W It represents the formation pressure during the water flooding stage, and P1 represents the predicted oil body energy.

6. The method according to any one of claims 1 to 5, characterized in that The step of obtaining a dimensionless gelation length representing the ratio of the actual gelation length of the water plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient representing the gelation plugging strength during migration, includes: Based on indoor sand filling pipe tests, the water plugging agent injection into the target reservoir is simulated using the water plugging agent to be injected to obtain the dimensionless gelation length. The migration process of the colloid in the target reservoir is simulated in combination with the maximum water flooding pressure when the water plugging agent to be injected is continued after gelation to obtain the gelation breakthrough pressure gradient.

7. The method according to claim 6, characterized in that The dimensionless gel length is obtained using the following expression: Among them, L0 represents the dimensionless gel length, L 实际 Indicates the actual gel length, L 理论 represents the theoretical gelation length, K represents the reservoir permeability, C 聚 represents the colloid concentration, μ 静 It represents the colloid viscosity, and pv represents the colloid pv number.

8. The method according to claim 7, characterized in that The gelation breakthrough pressure gradient is obtained using the following expression: dP max / dL 突破 =-214.647-0.00029K-0.0136C 聚 +28.5×lnμ 静 +2.9128pv Among them, P max Indicates the maximum water drive pressure, L 突破 Represents the gelation breakthrough pressure gradient.

9. The method according to any one of claims 1 to 8, characterized in that The method further comprises: A plurality of water-plugging agents to be injected with different physical properties are configured for the target reservoir, and the dosage of each water-plugging agent is obtained respectively. Then, the concentration and plugging radius of each water-plugging agent to be injected are adjusted according to the dosage, so that the plugging capacity of the water-plugging agent after adjustment is consistent with that before adjustment. Then, a cost analysis is performed for each adjusted water-plugging agent to obtain the optimal water-plugging agent injection scheme suitable for the current target reservoir.

10. A system for determining the amount of water plugging agent used in clastic oil reservoirs, characterized in that: The system includes the following modules: A shielding pressure difference calculation module is used to collect the formation pressure and oil well production of the target reservoir during the elastic flooding stage and the water flooding stage before injecting the water plugging agent, so as to obtain the shielding pressure difference representing the required plugging strength of the dominant water flow channel in the target reservoir; A gelation parameter calculation module is used to obtain a dimensionless gelation length representing the ratio of the actual gelation length of the water plugging agent to be injected in the target reservoir to the theoretical gelation length, and a gelation breakthrough pressure gradient representing the gelation plugging strength during migration; The water plugging agent dosage generation module is used to construct an ellipsoid model of the target reservoir and obtain the current dosage of the water plugging agent to be injected by combining the shielding pressure difference, the dimensionless gelation length, the correlation between the gelation breakthrough pressure gradient and the theoretical gelation length.

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