Method and system for determining seepage characteristics of thick oil chemical flooding emulsion

Abstract

The invention discloses a method and system for determining the seepage characteristics of thick oil chemical flooding emulsion, and the method comprises the steps: obtaining a capillary pressure curve of a reservoir in which target emulsion is located, so as to determine the porous medium pore distribution characteristics of the current reservoir; according to porous medium pore distribution characteristics, a round tube bundle model comprising a plurality of straight round tubes is constructed to simulate each pore in a reservoir, and the plurality of straight round tubes are divided into a first type of round tubes meeting oil-phase liquid flowing requirements, a second type of round tubes meeting water-phase liquid flowing requirements and a third type of round tubes meeting emulsion-phase liquid flowing requirements; wherein the hole diameter of the third-type circular tube is larger than that of the first-type circular tube and smaller than that of the second-type circular tube; and on the basis of the liquid flow characteristics of each type of circular pipes, the total flow and relative permeability of different-phase liquid in the current reservoir in the corresponding pores are obtained, and on the basis, the seepage characteristics of the target emulsion are obtained. According to the invention, accurate understanding and description of the multiphase seepage process of the emulsion system are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method and a system for determining the seepage characteristics of a heavy oil chemical flooding emulsion. Background Art

[0002] As conventional oil reservoirs continue to decrease in reserves, heavy oil chemical flooding technology has gradually attracted attention in recent years. In the process of heavy oil chemical flooding, due to the different concentrations of injected surfactants and additives, the oil-water system may form two dispersed systems with different physical properties, namely microemulsion system and emulsion system, under the action of surfactants. Among them, the particle size of microemulsion droplets is usually less than 0.1 micron, and the particle size of emulsion droplets is usually between 1.0 and 200.0 microns.

[0003] The relative permeability curve is a comprehensive reflection of the multiphase seepage characteristics in the rock pores. It is the most basic law followed by the multiphase in the seepage process. It has important guiding significance for optimizing oilfield development plans, improving oilfield recovery, and improving oilfield development effects. The heavy oil chemical flooding process involves the seepage process of the oil-water-emulsion three-phase coexistence system, and the characterization of relative permeability is relatively complex. At present, the research on the seepage law of microemulsion system in porous media is relatively mature, while the research on the seepage migration law of emulsion system is not perfect. In addition, the traditional chemical flooding relative permeability characterization method regards the emulsion as a component of the oil phase or the water phase, and directly uses the single-phase experimental results as the relative permeability of the oil-water two-phase of the emulsion. However, the relative permeability of the oil phase or the relative permeability of the water phase of the emulsion does not match the actual flow characteristics of the emulsion. Simply using the two-phase relative permeability as the relative permeability of the emulsion will inevitably lead to large calculation errors. Therefore, there is still a lack of means to obtain the three-phase relative permeability of heavy oil chemical flooding emulsion systems. It is necessary to develop a relative permeability calculation method for heavy oil chemical flooding that takes into account the flow characteristics of the emulsion to achieve an accurate understanding and description of the multiphase seepage process of the emulsion system. Summary of the invention

[0004] In order to solve the above problems, an embodiment of the present invention provides a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion, the method comprising: obtaining a capillary pressure curve of a reservoir where a target emulsion is located to determine the pore distribution characteristics of a porous medium in the current reservoir; according to the pore distribution characteristics of the porous medium, constructing a circular tube bundle model comprising a plurality of straight circular tubes to simulate each pore in the reservoir, and dividing the plurality of straight circular tubes into a first type of circular tubes that meet the flow requirements of oil phase liquid, a second type of circular tubes that meet the flow requirements of water phase liquid, and a third type of circular tubes that meet the flow requirements of emulsion phase liquid, wherein the pore size of the third type of circular tubes is larger than that of the first type of circular tubes and smaller than that of the second type of circular tubes; based on the liquid flow characteristics of each type of circular tube, obtaining the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores, based on which, obtaining the seepage characteristics of the target emulsion.

[0005] Preferably, the step of determining the pore distribution characteristics of the porous medium of the current reservoir includes: using the capillary pressure curve to analyze the correlation between the wetting phase saturation, capillary pressure and pore size of the current reservoir, and then using the correlation to calculate the distribution parameters that characterize the pore size distribution characteristics of the porous medium, wherein the distribution parameters are the volume fractions of different pores in the total pore volume.

[0006] Preferably, the correlation is expressed using the following expression:

[0007]

[0008] Where δ represents the pore diameter, S w represents water saturation, σ represents oil-water interfacial tension, θ represents the wetting angle, and p c Indicates capillary pressure.

[0009] Preferably, the distribution parameter is expressed using the following expression:

[0010]

[0011] Here, α represents the distribution parameter.

[0012] Preferably, the target emulsion is an unstable emulsion generated during the chemical flooding process, wherein, in the process of obtaining the total flow rate of the emulsion phase liquid in the corresponding pores in the current reservoir, it includes: first obtaining the droplet size and volume concentration of the emulsion dispersed phase based on an experimental method, and then using the droplet size and the volume concentration to calculate the total flow rate of the emulsion phase liquid in the current reservoir, so as to obtain the seepage characteristics of the target emulsion based on the total flow rate of the emulsion phase liquid, combined with the total flow rate of the oil phase liquid and the total flow rate of the water phase liquid, wherein the droplet median radius of the unstable emulsion is measured by an experimental method, and the ratio between the current droplet median radius and the distribution parameter is used as the droplet size of the dispersed phase of the unstable emulsion.

[0013] Preferably, the process of obtaining the total flow of different phase liquids in the current reservoir includes: calculating the total flow of oil phase liquid using the following expression:

[0014]

[0015] The total flow rate of the aqueous phase liquid is calculated using the following expression:

[0016]

[0017] The total flow rate of the emulsion phase liquid is calculated using the following expression:

[0018]

[0019] Among them, q1, q2 and q3 represent the total flow rate of oil phase liquid, the total flow rate of water phase liquid and the total flow rate of emulsion phase liquid respectively, τ represents the tortuosity, μ o Indicates the viscosity of the oil phase, μ w represents the viscosity of the water phase, φ represents the porosity, δ1 represents the maximum pore size of the first type of circular tube, δ2 represents the minimum pore size of the second type of circular tube, δ represents the pore diameter, α represents the distribution parameter, p represents the pore pressure, x represents the displacement component of the liquid in the horizontal direction, ξ represents the total flow rate of the emulsion phase liquid in a single pore, and C represents the volume concentration of the target emulsion dispersed phase.

[0020] Preferably, the total flow rate of the emulsion phase liquid is related to the droplet size, the volume concentration, and the pore size, wherein when the droplet size is smaller than the pore diameter and the volume concentration is smaller than the critical volume concentration for permeation, the total flow rate of the emulsion phase liquid is calculated using the following expression:

[0021]

[0022] When the droplet size is larger than the pore diameter, the total flow rate of the emulsion phase liquid is calculated using the following expression:

[0023]

[0024] When the droplet size is smaller than the pore diameter and the volume concentration is greater than the critical volume concentration for permeation, the total flow rate of the emulsion phase liquid is calculated using the following expression:

[0025]

[0026] Among them, r represents the pore radius, r0 represents the median radius of the dispersed phase droplet, m represents the ratio of the cross-sectional radius of the droplet after deformation to the pore radius, and κ represents a parameter related to the stacking state.

[0027] Preferably, the step of obtaining the relative permeabilities of different phases of liquid in the corresponding pores in the current reservoir includes: determining the equivalent absolute permeability of the target emulsion in the reservoir based on the circular tube bundle model, thereby obtaining the relative permeability of each phase of liquid in the corresponding pores in combination with Darcy's law of multiphase flow.

[0028] Preferably, the process of obtaining the relative permeability of each phase liquid in the corresponding pore includes: calculating the relative permeability of the oil phase liquid using the following expression:

[0029]

[0030] The relative permeability of the aqueous phase is calculated using the following expression:

[0031]

[0032] The relative permeability of the emulsion phase liquid is calculated using the following expression:

[0033]

[0034] Among them, K ro , K rw and K re They represent the relative permeability of oil phase liquid, water phase liquid and emulsion phase liquid respectively, δ1 represents the maximum pore size of the first type of circular tube, δ2 represents the minimum pore size of the second type of circular tube, δ represents the pore diameter, α represents the distribution parameter, ξ represents the total flow rate of the target emulsion, and C represents the volume concentration of the dispersed phase of the target emulsion.

[0035] On the other hand, the present invention also provides a system for determining the seepage characteristics of a heavy oil chemical flooding emulsion, the system comprising the following modules: a pore distribution characteristic acquisition module, which is used to obtain a capillary pressure curve of a reservoir where a target emulsion is located, so as to determine the pore distribution characteristics of a porous medium in the current reservoir; a model construction module, which is used to construct a circular tube bundle model comprising a plurality of straight circular tubes according to the pore distribution characteristics of the porous medium to simulate each pore in the reservoir, and divide the plurality of straight circular tubes into a first type of circular tubes that meet the flow requirements of oil phase liquid, a second type of circular tubes that meet the flow requirements of water phase liquid, and a third type of circular tubes that meet the flow requirements of emulsion phase liquid, wherein the pore size of the third type of circular tubes is larger than that of the first type of circular tubes and smaller than that of the second type of circular tubes; a seepage characteristic generation module, which is used to obtain the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores based on the liquid flow characteristics of each type of circular tube, and based on this, obtain the seepage characteristics of the target emulsion.

[0036] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0037] The present invention proposes a method and system for determining the seepage characteristics of a heavy oil chemical flooding emulsion. The method first obtains the pore size distribution of the emulsion flow area in the reservoir according to the capillary force curve; then, a circular tube bundle model containing straight circular tubes matching the size characteristics of each pore is constructed, and according to the liquid flow characteristics of straight circular tubes with different pore diameters, multiple straight circular tubes are divided into circular tube combinations that meet the flow requirements of different phase liquids; finally, the relative permeabilities of the oil phase, water phase and emulsion phase liquid in the emulsion are calculated based on the constructed circular tube bundle model, so as to determine the seepage characteristics of the emulsion. The present invention takes into account the flow characteristics of the emulsion, realizes the accurate understanding and description of the multiphase seepage process of the emulsion system, can accurately predict the effect of heavy oil chemical flooding development, lays the foundation for the numerical simulation of heavy oil chemical flooding, and provides technical support for the development and production practice of heavy oil reservoirs.

[0038] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose 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

[0039] 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:

[0040] Figure 1It is a step diagram of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0041] Figure 2 It is a schematic diagram of a circular tube bundle model of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0042] Figure 3 It is a schematic diagram of dividing three types of circular tubes in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0043] Figure 4 It is a schematic diagram of the flow velocity distribution of a single-phase fluid in a single circular tube of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0044] Figure 5 It is a schematic diagram of the flow velocity distribution of the dispersed phase fluid in a single circular tube of the method for determining the seepage characteristics of the heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0045] Figure 6 It is a schematic diagram of the distribution of dispersed phase droplets with a particle size smaller than the pipe diameter and a low volume concentration in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0046] Figure 7 It is a schematic diagram of the deformation of dispersed phase droplets whose particle size is larger than the pipe diameter in the method for determining the seepage characteristics of heavy oil chemical flooding emulsion in an embodiment of the present application.

[0047] Figure 8 It is a schematic diagram of the accumulation of dispersed phase droplets with a particle size smaller than the pipe diameter and a high volume concentration in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0048] Fig. 9 It is a schematic diagram of a one-dimensional sand-filled tube water-in-oil emulsion flooding heavy oil experiment of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0049] Fig.10 It is a fitting curve of the pore size distribution of the sand-filled pipe pores in the method for determining the seepage characteristics of the heavy oil chemical flooding emulsion according to the embodiment of the present application.

[0050] Fig.11 It is a sand-filled tube emulsion-oil phase relative permeability curve of the method for determining the seepage characteristics of heavy oil chemical flooding emulsion in an embodiment of the present application.

[0051] Fig.12 The invention discloses a one-dimensional sand-filled tube experiment of an oil-in-water emulsion and a cumulative production of heavy oil in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion in an embodiment of the present application.

[0052] Fig.13 It is a module block diagram of a system for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. DETAILED DESCRIPTION

[0053] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0054] In addition, the steps shown in the flowcharts of the accompanying drawings can 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 can be performed in an order different from that shown here.

[0055] As conventional oil reservoirs continue to decrease in reserves, heavy oil chemical flooding technology has gradually attracted attention in recent years. In the process of heavy oil chemical flooding, due to the different concentrations of injected surfactants and additives, the oil-water system may form two dispersed systems with different physical properties, namely microemulsion system and emulsion system, under the action of surfactants. Among them, the particle size of microemulsion droplets is usually less than 0.1 micron, and the particle size of emulsion droplets is usually between 1.0 and 200.0 microns.

[0056] The relative permeability curve is a comprehensive reflection of the multiphase seepage characteristics in the rock pores. It is the most basic law followed by the multiphase in the seepage process. It has important guiding significance for optimizing oilfield development plans, improving oilfield recovery, and improving oilfield development effects. The heavy oil chemical flooding process involves the seepage process of the oil-water-emulsion three-phase coexistence system, and the characterization of relative permeability is relatively complex. At present, the research on the seepage law of microemulsion system in porous media is relatively mature, while the research on the seepage migration law of emulsion system is not perfect. In addition, the traditional chemical flooding relative permeability characterization method regards the emulsion as a component of the oil phase or the water phase, and directly uses the single-phase experimental results as the relative permeability of the oil-water two-phase of the emulsion. However, the relative permeability of the oil phase or the relative permeability of the water phase of the emulsion does not match the actual flow characteristics of the emulsion. Simply using the two-phase relative permeability as the relative permeability of the emulsion will inevitably lead to large calculation errors. Therefore, there is still a lack of means to obtain the three-phase relative permeability of heavy oil chemical flooding emulsion systems. It is necessary to develop a relative permeability calculation method for heavy oil chemical flooding that takes into account the flow characteristics of the emulsion to achieve an accurate understanding and description of the multiphase seepage process of the emulsion system.

[0057] Therefore, in order to solve the above problems, the present invention proposes a method and system for determining the seepage characteristics of heavy oil chemical flooding emulsions. The method first obtains the pore size distribution of the emulsion flow area in the reservoir according to the capillary force curve; then, a circular tube bundle model containing straight circular tubes matching the size characteristics of each pore is constructed, and according to the liquid flow characteristics of straight circular tubes with different pore diameters, multiple straight circular tubes are divided into circular tube combinations that meet the flow requirements of different phase liquids; finally, the relative permeabilities of the oil phase, water phase and emulsion phase liquid in the emulsion are calculated based on the constructed circular tube bundle model, so as to determine the seepage characteristics of the emulsion. The present invention takes into account the flow characteristics of the emulsion, realizes the accurate understanding and description of the multiphase seepage process of the emulsion system, can accurately predict the development effect of heavy oil chemical flooding, lays the foundation for the numerical simulation of heavy oil chemical flooding, and provides technical support for the development and production practice of heavy oil reservoirs.

[0058] Embodiment 1

[0059] The actual rock pore structure is extremely complex, consisting of countless pores of varying sizes, which are connected by one or more throats, and some pores are not connected to other pores at all. For the convenience of research, rock pores are often approximately regarded as consisting of many capillaries of varying radii, and pore throats (or capillaries) of a certain radius have a certain capillary pressure. The wetting phase fluid can partially enter the capillary pores by self-imbibition without the help of external forces, while for the non-wetting phase fluid, the capillary pressure is a resistance, and the capillary pressure must be overcome by external forces. Only when the external pressure is equal to or exceeds the capillary pressure of the throat (assuming that gravity is ignored) can the non-wetting phase enter the pores.

[0060] When the non-wetting phase enters the rock pores, it also pushes the wetting phase out of the pores, increasing the saturation of the non-wetting phase and reducing the saturation of the wetting phase. At this time, the external pressure is equivalent to the capillary pressure of the throat. As the external pressure increases, the non-wetting phase can enter the pores it connects through smaller throats, driving out the wetting phase, further increasing the saturation of the non-wetting phase and further reducing the saturation of the wetting phase. The above is the theoretical basis for obtaining the capillary pressure curve.

[0061] Figure 1 1 is a step diagram of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0062] like Figure 1As shown, in step S110, the capillary pressure curve of the reservoir where the target emulsion is located is obtained to determine the pore distribution characteristics of the porous media of the current reservoir. In practical applications, the capillary pressure is determined by the curvature of the non-wetting phase surface, and the interface curvature is related to the size of the pore throat, and is also related to the saturation of the non-wetting phase, and the capillary pressure increases as the saturation of the wetting phase decreases. In other words, the capillary pressure is a function of the wetting phase saturation, and the capillary pressure curve reflects the correlation between the capillary pressure and the wetting phase saturation. Therefore, in an embodiment of the present application, the capillary pressure curve of the reservoir where the target emulsion is located is first obtained, and then the relationship curve between the pore size and the wetting phase saturation is determined based on the correlation between the capillary pressure and the wetting phase saturation reflected by the capillary pressure curve, combined with the correlation between the pore size and the capillary pressure, so that the pore distribution characteristics of the porous media of the current reservoir can be obtained.

[0063] In the step of determining the pore distribution characteristics of the porous medium of the current reservoir, the capillary pressure curve is used to analyze the correlation between the wetting phase saturation, capillary pressure and pore size of the current reservoir, and then the correlation is used to calculate the distribution parameters characterizing the pore size distribution characteristics of the porous medium. Specifically, after obtaining the capillary pressure curve, this embodiment uses the correlation between the capillary pressure and the wetting phase saturation reflected by the obtained capillary pressure curve, and the correlation between the pore size and the capillary pressure obtained by analysis, and establishes the correlation between the pore size and the wetting phase saturation based on the capillary pressure parameters that exist in both types of correlations. By substituting the known wetting phase saturation into the correlation between the pore size and the wetting phase saturation, the distribution parameters characterizing the pore size distribution characteristics of the porous medium of the current reservoir are obtained. Among them, the distribution parameters are the volume fractions of different pores in the total pore volume. In the embodiment of the present application, the different pores are pores located at different positions in the current reservoir.

[0064] In the embodiment of the present application, the correlation between pore size and wetting phase saturation is expressed by the following expression:

[0065]

[0066] Where δ represents the pore diameter, S w represents water saturation, σ represents oil-water interfacial tension, θ represents the wetting angle, and p c Indicates capillary pressure.

[0067] Next, in the embodiment of the present application, the distribution parameter characterizing the pore size distribution characteristics of the porous medium is expressed by the following expression:

[0068]

[0069] Here, α represents the distribution parameter.

[0070] Further, in step S120, according to the pore distribution characteristics of the porous medium, a circular tube bundle model including multiple straight circular tubes is constructed to simulate each pore in the reservoir, and the multiple straight circular tubes are divided into a first type of circular tubes that meet the oil phase liquid flow requirements, a second type of circular tubes that meet the water phase liquid flow requirements, and a third type of circular tubes that meet the emulsion phase liquid flow requirements, wherein the pore diameter of the third type of circular tube is larger than that of the first type of circular tube and smaller than that of the second type of circular tube. Figure 2 Schematic diagram of a circular tube bundle model of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. After obtaining the pore distribution characteristics of the porous medium, that is, obtaining the size of each pore distributed in the current reservoir, a porous medium pore distribution characteristic is constructed as follows: Figure 2 The circular tube bundle model shown contains multiple straight circular tubes to simulate each pore in the reservoir. In practical applications, the oil phase, water phase and emulsion phase liquid in the emulsion have different flow channels (pores) in the reservoir. After the circular tube bundle model is constructed, the size of each straight circular tube constituting the circular tube bundle model is used as the pore size of the flow channel, and the flow channels of the oil phase, water phase and emulsion phase liquid are distinguished according to the size of the pore size. Figure 3 Schematic diagram of three types of circular tube divisions of the method for determining the seepage characteristics of heavy oil chemical flooding emulsion in the embodiment of the present application. Figure 3 In this embodiment, the first type of circular tube has the smallest aperture size, which is occupied by the oil phase. The water phase cannot enter during water flooding and chemical flooding, and only the oil phase flows; the second type of circular tube has the largest aperture size, which is occupied by the water phase during water flooding and chemical flooding, and only the water phase flows; and the third type of circular tube has an aperture size between the first type of circular tube and the second type of circular tube, which is occupied by the oil phase during water flooding, and forms an oil-in-water emulsion (i.e., emulsion phase) with the injection of surfactant during chemical flooding and flows.

[0071] After determining the phase type of the liquid flowing in each type of circular tube, in step S130, based on the liquid flow characteristics of each type of circular tube, the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores are obtained, and based on this, the seepage characteristics of the target emulsion are obtained. In an embodiment of the present application, the phase type of the liquid flowing in each type of circular tube is determined to model the phase type of the liquid flowing in the actual pores. Accordingly, based on the flow of different phases of liquid in the corresponding type of circular tube, the flow state of the corresponding phase liquid in the actual pore is analyzed, and then the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores are calculated, wherein the relative permeability of each phase of liquid is obtained according to the total flow rate of the corresponding phase liquid in the corresponding type of circular tube, and the set of relative permeabilities of each phase of liquid is the seepage characteristics of the target emulsion.

[0072] In practical applications, the emulsion in the heavy oil chemical flooding process is an unstable emulsion generated during the chemical flooding displacement process. That is to say, the target emulsion of this embodiment is an unstable emulsion generated during the chemical flooding displacement process. In the process of obtaining the total flow rate of the emulsion phase liquid in the corresponding pores in the current reservoir, the droplet size and volume concentration of the emulsion dispersed phase are first obtained based on the experimental method, and then the total flow rate of the emulsion phase liquid in the current reservoir is calculated using the droplet size and volume concentration, so as to obtain the seepage characteristics of the target emulsion based on the total flow rate of the emulsion phase liquid, combined with the total flow rate of the oil phase liquid and the total flow rate of the water phase liquid. In the actual emulsion system, the dispersed phase of the emulsion phase liquid is oil and the dispersion medium is water, so this embodiment uses the dispersed phase of the emulsion phase liquid in the target emulsion as the target emulsion dispersed phase. The droplet size and volume concentration of the emulsion dispersed phase are measured by experimental method. After obtaining the droplet size and volume concentration of the dispersed phase of the emulsion, the droplet size and volume concentration are used to calculate the liquid flow rate in each straight circular tube in the third type of circular tube, and then the total flow rate of the emulsion phase liquid in the current reservoir is obtained by accumulating the liquid flow rate of each straight circular tube. Finally, the total flow rate of the emulsion phase liquid, the total flow rate of the oil phase liquid and the total flow rate of the water phase liquid in the current reservoir are used to calculate the seepage characteristics of the emulsion phase liquid, the oil phase liquid and the water phase liquid in the target emulsion, respectively, so as to obtain the seepage characteristics of the target emulsion.

[0073] Next, the present invention measures the median radius of the droplets of the unstable emulsion by an experimental method, and uses the ratio between the current median radius of the droplets and the distribution parameter as the droplet size of the dispersed phase of the unstable emulsion. Specifically, the present invention measures the droplet size and the dispersed phase volume concentration of the emulsion by an experimental method, determines the median radius of the droplets of the current emulsion, and uses the ratio between the current median radius of the droplets and the pore radius as the characterization parameter of the droplet size of the dispersed phase of the emulsion. In the embodiments of the present application, the experimental method used is a focused beam reflection measurement method or other image processing experimental methods. For a relatively stable emulsion prepared in advance by methods such as ultrasonic dispersion, that is, when the target emulsion is a stable emulsion, it is believed that the median radius of its dispersed phase droplets is a fixed value; or, for an emulsion generated during chemical flooding, that is, when the target emulsion is an unstable emulsion, it is believed that the dispersed phase droplet size is proportional to the pore size of the porous medium, and the proportionality coefficient is related to the surfactant concentration and the flow rate. Therefore, it is necessary to first use the adopted experimental method to measure the dispersed phase droplet particle size of the target emulsion to obtain the droplet median radius in order to obtain the droplet particle size of the dispersed phase of the unstable emulsion.

[0074] In the embodiments of the present application, the proportionality coefficient between the median radius of the emulsion dispersed phase droplet and the pore radius is expressed by the following expression:

[0075]

[0076] Where r represents the pore radius, r0 represents the median radius of the dispersed phase droplet, and a represents the proportionality coefficient.

[0077] Based on the above analysis, it can be seen that the flow state of the emulsion phase fluid is related to the droplet size, volume concentration, and pore size, so the total flow rate of the emulsion phase liquid is related to the droplet size, volume concentration, and pore size. Figure 6 This is a schematic diagram of the distribution of dispersed phase droplets with a particle size smaller than the pipe diameter and a low volume concentration in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. Figure 6 , L A represents the droplet diameter, L B Represents the droplet spacing, when the droplet size is smaller than the pore diameter and the volume concentration is less than the critical volume concentration for penetration (i.e.: ), the total flow rate of the emulsion phase liquid is calculated using the following expression, where C0 represents the critical volume concentration:

[0078]

[0079] Where ξ represents the total flow rate of the emulsion phase liquid in a single pore, and C represents the volume concentration of the target emulsion dispersed phase.

[0080] In the embodiment of the present application, for an unstable emulsion, the total flow rate of the emulsion phase liquid in a single pore can be written as the proportional coefficient of the median radius of the dispersed phase droplet to the pore radius, so the total flow rate of the emulsion phase liquid is directly calculated using the following expression:

[0081]

[0082] Figure 7 Schematic diagram of the deformation of dispersed phase droplets with a particle size larger than the pipe diameter in the method for determining the seepage characteristics of heavy oil chemical flooding emulsion according to the embodiment of the present application. Figure 7 , when the droplet size is larger than the pore diameter (i.e.: r0>r, ), the total flow rate of the emulsion phase liquid is calculated using the following expression, where N c Indicates the number of capillaries:

[0083]

[0084] Where m represents the ratio of the cross-sectional radius of the droplet after deformation to the pore radius.

[0085] Figure 8 This is a schematic diagram of the accumulation of dispersed phase droplets with a particle size smaller than the pipe diameter and a high volume concentration in the method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. Figure 8 , L Arepresents the droplet diameter, L B represents the droplet spacing, b represents the distance between the outer surface of the droplet and the inner surface of the straight circular tube on the same side. When the droplet size is smaller than the pore diameter and the volume concentration is greater than the critical volume concentration for penetration (i.e.: ), the total flow rate of the emulsion phase liquid is calculated using the following expression:

[0086]

[0087] Here, κ represents a parameter related to the stacking state.

[0088] In a specific embodiment of the present application, the value range of κ is between 2 and 4.

[0089] Figure 4 Schematic diagram of the flow velocity distribution of a single-phase fluid in a single circular tube in a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. Figure 4 , u represents the flow velocity of the dispersed phase fluid. Based on the constructed circular tube bundle model, the Poiseuille law is used to describe the flow process of the oil phase liquid or water phase liquid in a single pore:

[0090]

[0091] Where q represents the total flow rate of single-phase liquid in a single pore, μ represents the liquid viscosity, L represents the pore length, and Δp represents the pressure difference on both sides of the pore.

[0092] In the embodiment of the present application, for the case where the fluid in the pore is an oil phase or a water phase, the total flow rate of the fluid in the corresponding pore is directly described based on the total flow rate of the single-phase liquid in the aforementioned single pore. Figure 5 Schematic diagram of the flow velocity distribution of dispersed phase fluid in a single circular tube of the method for determining the seepage characteristics of heavy oil chemical flooding emulsion in the embodiment of the present application. Figure 5 , u represents the flow velocity of the dispersed phase fluid. For the case where the fluid in the pore is an emulsion phase, the total flow rate of the fluid in the corresponding pore is described by the flow ratio representing the ratio between the flow rate of the single-phase flow of the external phase fluid without dispersed phase droplets in the emulsion phase liquid and the emulsion flow rate containing dispersed phase droplets in the emulsion phase liquid:

[0093]

[0094] Among them, represents the total flow rate of emulsion phase liquid in a single pore, q1 represents the flow rate of single-phase flow of external phase fluid without dispersed phase droplets in the emulsion phase liquid, and q2 represents the emulsion flow rate containing dispersed phase droplets in the emulsion phase liquid.

[0095] Furthermore, in the process of obtaining the total flow rate of different phases of liquid in the current reservoir, it includes:

[0096] The total oil phase liquid flow rate is calculated using the following expression:

[0097]

[0098] The total flow rate of the aqueous phase liquid is calculated using the following expression:

[0099]

[0100] The total emulsion phase liquid flow rate is calculated using the following expression:

[0101]

[0102] Among them, q1, q2 and q3 represent the total flow rate of oil phase liquid, the total flow rate of water phase liquid and the total flow rate of emulsion phase liquid respectively, τ represents the tortuosity, μ o Indicates the viscosity of the oil phase, μ w represents the viscosity of the water phase, φ represents the porosity, δ1 represents the maximum pore size of the first type of circular tube, δ2 represents the minimum pore size of the second type of circular tube, δ represents the pore diameter, α represents the distribution parameter, p represents the pore pressure, and x represents the displacement component of the liquid in the horizontal direction, which represents the volume concentration of the dispersed phase of the target emulsion.

[0103] For the case where the fluid in the pore is an emulsion phase, the flow state of the emulsion in the pore is different when the dispersed phase droplet particle size and volume concentration of the target emulsion are different. Therefore, the present invention specifically describes the total flow rate of the fluid in the pore in the following manner according to the differences in the dispersed phase droplet particle size and volume concentration, thereby effectively improving the accuracy of the determination results of the seepage characteristics of the target emulsion based on the targeted analysis of emulsion phase liquids with different flow states.

[0104] Further, in the step of obtaining the relative permeability of different phases of liquid in the current reservoir in the corresponding pores, the equivalent absolute permeability of the target emulsion in the reservoir is determined based on the circular tube bundle model, so as to obtain the relative permeability of each phase of liquid in the corresponding pores in combination with the multiphase flow Darcy's law. Specifically, this embodiment calculates the equivalent absolute permeability of the target emulsion in the reservoir based on the constructed circular tube bundle model, and substitutes the calculation result into the multiphase flow Darcy's law to obtain the relative permeability of different phases of liquid in the corresponding pores. Among them, the multiphase flow Darcy's law is expressed by the following expression:

[0105]

[0106] Where Q represents the seepage volume in the cylinder, represents the pressure potential, K r represents relative permeability, K represents equivalent absolute permeability, and A represents the cross-sectional area of ​​the cylinder.

[0107] In the embodiment of the present application, the equivalent absolute permeability is calculated using the following expression:

[0108]

[0109] Furthermore, in the process of obtaining the relative permeability of each phase liquid in the corresponding pore, firstly, the relative permeability of the oil phase liquid is calculated using the following expression:

[0110]

[0111] Then, the relative permeability of the aqueous phase is calculated using the following expression:

[0112]

[0113] Finally, the relative permeability of the emulsion phase liquid is calculated using the following expression:

[0114]

[0115] Among them, K ro , K rw and K re They represent the oil phase liquid relative permeability, water phase liquid relative permeability and emulsion phase liquid relative permeability respectively.

[0116] Embodiment 2

[0117] Fig. 9 1 is a schematic diagram of a one-dimensional sand-filled tube water-in-oil emulsion flooding heavy oil experiment of a method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application. In a specific embodiment of the present application, the method for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to the first embodiment is used to determine the seepage characteristics of a heavy oil chemical flooding emulsion. Fig. 9 The sand-filled pipe water-in-oil emulsion driving heavy oil experiment shown in the figure is simulated and calculated. The two ends of the one-dimensional sand-filled pipe in this embodiment are respectively one injection and one production. Specifically, first, the sand-filled pipe is injected with saturated heavy oil by an injection method with a fixed flow rate of Q, and then the pre-prepared water-in-oil emulsion is continuously injected. Among them, the experimental parameters such as porosity, core length and displacement speed of the one-dimensional sand-filled pipe are shown in Table 1, and the physical properties of the water-in-oil emulsion and heavy oil are shown in Table 2.

[0118] Table 1

[0119]

[0120] Table 2

[0121]

[0122]

[0123] Next, according to the method for determining the seepage characteristics of the heavy oil chemical flooding emulsion described in Example 1, the pore size distribution of the porous medium of the sand-filled tube is determined and fitted to obtain the following: Fig.10 The pore size distribution results shown are ( Fig.10 is a fitting curve of the pore size distribution of the sand-filled tube pores in the method for determining the seepage characteristics of the heavy oil chemical flooding emulsion in the embodiment of the present application). In a specific embodiment of the present application, the droplet size of the dispersed phase of the emulsion is determined to be 1.8 times the median pore size of the sand-filled tube pores, and the calculation is as follows Fig.11 The relative permeability curves of oil-in-water emulsion and heavy oil are shown in ( Fig.11 is a sand-filled tube emulsion-oil phase relative permeability curve of the method for determining the seepage characteristics of heavy oil chemical flooding emulsion in an embodiment of the present application). Next, based on Fig.11 The relative permeability curve shown in the figure is used to simulate the one-dimensional sand-filled pipe water-in-oil emulsion flooding heavy oil experiment, and the following is obtained: Fig.12 Cumulative recovery of heavy oil and emulsion shown ( Fig.12 It is a one-dimensional sand filling tube experiment of the method for determining the seepage characteristics of the heavy oil chemical flooding emulsion according to the embodiment of the present application (water-in-oil emulsion and heavy oil cumulative production). At this time, the simulation results are consistent with the experimental data, which shows that the present invention realizes the accurate acquisition of the seepage characteristics of the heavy oil chemical flooding emulsion.

[0124] Embodiment 3

[0125] Based on the method for determining the seepage characteristics of a heavy oil chemical flooding emulsion described in the first embodiment, an embodiment of the present invention further provides a system for determining the seepage characteristics of a heavy oil chemical flooding emulsion (hereinafter referred to as “seepage characteristics determination system”). Fig.13 It is a module block diagram of a system for determining the seepage characteristics of a heavy oil chemical flooding emulsion according to an embodiment of the present application.

[0126] like Fig.13As shown, the seepage characteristic determination system in the embodiment of the present invention includes: a pore distribution characteristic acquisition module 131, a model construction module 132 and a seepage characteristic generation module 133. The pore distribution characteristic acquisition module 131 is implemented according to the method described in the above step S110, and is configured to obtain the capillary pressure curve of the reservoir where the target emulsion is located to determine the pore distribution characteristics of the porous medium of the current reservoir; the model construction module 132 is implemented according to the method described in the above step S120, and is configured to construct a circular tube bundle model including multiple straight circular tubes to simulate each pore in the reservoir according to the pore distribution characteristics of the porous medium determined by the pore distribution characteristic acquisition module 131, and divide the multiple straight circular tubes into a first type of circular tube that meets the oil phase liquid flow requirements, a second type of circular tube that meets the water phase liquid flow requirements, and a third type of circular tube that meets the emulsion phase liquid flow requirements, wherein the pore size of the third type of circular tube is larger than that of the first type of circular tube and smaller than that of the second type of circular tube; the seepage characteristic generation module 133 is implemented according to the method described in the above step S130, and is configured to obtain the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores based on the liquid flow characteristics of each type of circular tube constructed by the model construction module 132, based on which, the seepage characteristics of the target emulsion are obtained.

[0127] The present invention discloses a method and system for determining the seepage characteristics of a heavy oil chemical flooding emulsion. The method first obtains the pore size distribution of the emulsion flow area in the reservoir according to the capillary force curve; then, a circular tube bundle model containing straight circular tubes matching the size characteristics of each pore is constructed, and according to the liquid flow characteristics of straight circular tubes with different pore diameters, multiple straight circular tubes are divided into circular tube combinations that meet the flow requirements of different phase liquids; finally, the relative permeabilities of the oil phase, water phase and emulsion phase liquid in the emulsion are calculated based on the constructed circular tube bundle model, so as to determine the seepage characteristics of the emulsion. The present invention takes into account the flow characteristics of the emulsion, realizes the accurate understanding and description of the multiphase seepage process of the emulsion system, can accurately predict the development effect of heavy oil chemical flooding, lays a foundation for the numerical simulation of heavy oil chemical flooding, and provides technical support for the development and production practice of heavy oil reservoirs.

[0128] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0129] 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.

[0130] It should be understood by those skilled in the art that the modules or steps of the present invention described above can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0131] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for determining the seepage characteristics of a heavy oil chemical flooding emulsion, characterized in that: The method comprises: Obtain the capillary pressure curve of the reservoir where the target emulsion is located to determine the pore distribution characteristics of the porous media in the current reservoir; According to the pore distribution characteristics of the porous medium, a circular tube bundle model including a plurality of straight circular tubes is constructed to simulate each pore in the reservoir, and the plurality of straight circular tubes are divided into a first type of circular tubes meeting the flow requirements of oil phase liquid, a second type of circular tubes meeting the flow requirements of water phase liquid, and a third type of circular tubes meeting the flow requirements of emulsion phase liquid, wherein the pore diameter of the third type of circular tubes is larger than that of the first type of circular tubes and smaller than that of the second type of circular tubes; Based on the liquid flow characteristics of each type of circular tube, the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores are obtained, based on which the seepage characteristics of the target emulsion are obtained.

2. The method according to claim 1, characterized in that The step of determining the pore distribution characteristics of the porous medium of the current reservoir includes: The capillary pressure curve is used to analyze the correlation between the wetting phase saturation, capillary pressure and pore size of the current reservoir, and then the correlation is used to calculate the distribution parameters that characterize the pore size distribution characteristics of the porous medium, wherein the distribution parameters are the volume fractions of different pores in the total pore volume.

3. The method according to claim 2, characterized in that The correlation is expressed by the following expression: Where δ represents the pore diameter, S w represents water saturation, σ represents oil-water interfacial tension, θ represents the wetting angle, and p c Indicates capillary pressure.

4. The method according to claim 3, characterized in that The distribution parameters are expressed using the following expression: Here, α represents the distribution parameter.

5. The method according to any one of claims 2 to 4, characterized in that: The target emulsion is an unstable emulsion generated in the chemical flooding process, wherein the process of obtaining the total flow rate of the emulsion phase liquid in the corresponding pores in the current reservoir includes: First, the droplet size and volume concentration of the emulsion dispersed phase are obtained based on the experimental method, and then the total flow rate of the emulsion phase liquid in the current reservoir is calculated using the droplet size and the volume concentration, so as to obtain the seepage characteristics of the target emulsion according to the total flow rate of the emulsion phase liquid, combined with the total flow rate of the oil phase liquid and the total flow rate of the water phase liquid, wherein, The droplet median radius of the unstable emulsion is measured by an experimental method, and the ratio between the current droplet median radius and the distribution parameter is used as the droplet particle size of the dispersed phase of the unstable emulsion.

6. The method according to claim 5, characterized in that The process of obtaining the total flow rate of different phases of liquid in the current reservoir includes: The total oil phase liquid flow rate is calculated using the following expression: The total flow rate of the aqueous phase liquid is calculated using the following expression: The total flow rate of the emulsion phase liquid is calculated using the following expression: Among them, q1, q2 and q3 represent the total flow rate of oil phase liquid, the total flow rate of water phase liquid and the total flow rate of emulsion phase liquid respectively, τ represents the tortuosity, μ o Indicates the oil phase viscosity, μ w represents the viscosity of the water phase, φ represents the porosity, δ1 represents the maximum pore size of the first type of circular tube, δ2 represents the minimum pore size of the second type of circular tube, δ represents the pore diameter, α represents the distribution parameter, p represents the pore pressure, x represents the displacement component of the liquid in the horizontal direction, ξ represents the total flow rate of the emulsion phase liquid in a single pore, and C represents the volume concentration of the target emulsion dispersed phase.

7. The method according to claim 6, characterized in that The total flow rate of the emulsion phase liquid is related to the droplet size, the volume concentration, and the pore size, wherein: When the droplet size is smaller than the pore diameter and the volume concentration is less than the critical volume concentration for permeation, the total flow rate of the emulsion phase liquid is calculated using the following expression: When the droplet size is larger than the pore diameter, the total flow rate of the emulsion phase liquid is calculated using the following expression: When the droplet size is smaller than the pore diameter and the volume concentration is greater than the critical volume concentration for permeation, the total flow rate of the emulsion phase liquid is calculated using the following expression: Among them, r represents the pore radius, r0 represents the median radius of the dispersed phase droplet, m represents the ratio of the cross-sectional radius of the droplet after deformation to the pore radius, and κ represents a parameter related to the stacking state.

8. The method according to any one of claims 2 to 7, characterized in that: The step of obtaining the relative permeabilities of different phases of liquid in the current reservoir in the corresponding pores includes: Based on the circular tube bundle model, the equivalent absolute permeability of the target emulsion in the reservoir is determined, and then combined with Darcy's law of multiphase flow, the relative permeability of each phase of liquid in the corresponding pore is obtained.

9. The method according to claim 8, characterized in that The process of obtaining the relative permeability of each phase of liquid in the corresponding pore includes: The relative permeability of the oil phase liquid is calculated using the following expression: The relative permeability of the aqueous phase is calculated using the following expression: The relative permeability of the emulsion phase liquid is calculated using the following expression: Among them, K ro , K rw and K re They represent the relative permeability of oil phase liquid, water phase liquid and emulsion phase liquid respectively, δ1 represents the maximum pore size of the first type of circular tube, δ2 represents the minimum pore size of the second type of circular tube, δ represents the pore diameter, α represents the distribution parameter, ξ represents the total flow rate of the target emulsion, and C represents the volume concentration of the dispersed phase of the target emulsion.

10. A system for determining the flow characteristics of a heavy oil chemical flooding emulsion, characterized in that: The system includes the following modules: A pore distribution characteristic acquisition module is used to obtain the capillary pressure curve of the reservoir where the target emulsion is located to determine the pore distribution characteristics of the porous medium of the current reservoir; A model building module, which is used to build a circular tube bundle model including a plurality of straight circular tubes to simulate each pore in the reservoir according to the pore distribution characteristics of the porous medium, and divide the plurality of straight circular tubes into a first type of circular tubes meeting the flow requirements of oil phase liquid, a second type of circular tubes meeting the flow requirements of water phase liquid, and a third type of circular tubes meeting the flow requirements of emulsion phase liquid, wherein the pore size of the third type of circular tubes is larger than that of the first type of circular tubes and smaller than that of the second type of circular tubes; The seepage characteristic generation module is used to obtain the total flow rate and relative permeability of different phases of liquid in the current reservoir in the corresponding pores based on the liquid flow characteristics of each type of circular tube, and based on this, obtain the seepage characteristics of the target emulsion.

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