CN113569407A - Method and device for calculating capillary force and relative permeability curve - Google Patents

Abstract

Provided herein are methods and apparatus for calculating capillary force and relative permeability curves, wherein the method comprises: determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star; performing single-phase flow simulation calculation on the model, and determining the absolute permeability of the rock core; sequentially carrying out displacement simulation calculation of multiple displacement types on the model, and respectively determining the change relation between the capillary force and the water saturation of the rock core, the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation; and combining each change relation corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation. The efficiency in obtaining the capillary force and relative permeability curve of the core can be improved.

Description

Method and device for calculating capillary force and relative permeability curve

Technical Field

The invention relates to the field of reservoir exploration, in particular to a method and a device for calculating a capillary force and relative permeability curve.

Background

The capillary force curve refers to a curve of a change relation between capillary force and water saturation of the core, and the relative permeability curve refers to a curve of a change relation between relative permeability of an oil phase and water saturation of the core and a curve of a change relation between relative permeability of a water phase and water saturation of the core in an oil-water or water-oil displacement process.

Because the multiphase flow of oil, gas and water in the core of the reservoir of the oil and gas reservoir is an important problem in the field of oil and gas field development, the flow characteristics of multiphase fluid are represented by mainly depending on capillary force and relative permeability curves in a macroscopic view. In order to obtain the capillary force and relative permeability curve, in the prior art, after an accurate experiment of an indoor core is mainly performed, experimental data are analyzed, and then the capillary force and relative permeability curve of the core is obtained.

However, since the accurate indoor core experiment takes a long time, the time for the cores with different permeabilities is about several days or even months. This will greatly expend the efforts of researchers and lead to a reduction in research efficiency. Therefore, there is a need for a method for calculating capillary force and relative permeability curves, which can improve the efficiency of obtaining the capillary force and relative permeability curves of the core.

Disclosure of Invention

It is an object of embodiments herein to provide a method and apparatus for calculating capillary force and relative permeability curves to improve efficiency in obtaining core capillary force and relative permeability curves.

To achieve the above objects, in one aspect, the present embodiments provide a method for calculating a capillary force and relative permeability curve, including:

determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

Preferably, the performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core includes:

performing single-phase flow simulation calculation on the core pore network model, and determining the conductivity coefficient of each pore in the core pore network model and the conductivity coefficients among pores which are mutually communicated;

determining the pressure of each pore according to the conductivity coefficient among the interconnected pores;

and determining the absolute permeability of the core according to the pressure of each pore and the corresponding conductivity coefficient.

Preferably, the displacement simulation calculation of multiple displacement types is sequentially performed on the core pore network model, and the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to each displacement simulation calculation, are respectively determined, and the method comprises the following two steps:

the first step is as follows:

performing oil-flooding water simulation calculation on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the oil-flooding water simulation calculation;

the second step is as follows:

performing simulation calculation of water-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of water-wet core water flooding;

or performing simulation calculation of oil-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of the oil-wet core water flooding;

or performing simulation calculation of mixed wetting core water flooding on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulation calculation of the mixed wetting core water flooding.

Preferably, the performing oil-drive water simulation calculation on the core pore network model, and determining a change relationship between a capillary force and core water saturation, a change relationship between oil phase effective permeability and core water saturation, and a change relationship between water phase effective permeability and core water saturation, which correspond to the oil-drive water simulation calculation, includes:

determining a threshold pressure value of each throat, the water saturation of a first rock core in an initial state, a first capillary force in the initial state, a first capillary force in a termination state and a first displacement step length;

determining a first capillary force in an initial state as a current first capillary force;

circularly performing screening on all throats and pores, and determining the throat with the threshold pressure value smaller than or equal to the current first capillary force and all pores communicated with the throat; updating the water saturation of the first core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the first core corresponding to the current first capillary force; determining a first oil phase relative permeability and a first water phase relative permeability corresponding to the current first core water saturation according to the current first core water saturation and a first oil phase conductivity coefficient and a first water phase conductivity coefficient corresponding to each pore or throat; updating the current first capillary force, determining the sum of the current first capillary force and the first displacement step length as the updated current first capillary force, and determining the current first core water saturation corresponding to the current first capillary force one by one, and the first oil phase relative permeability and the first water phase relative permeability corresponding to the current first core water saturation;

and ending the cycle until the current first capillary force is greater than the first capillary force in the terminal state.

Preferably, the performing simulation calculation of water-wet core water flooding on the core pore network model, and determining a change relationship between capillary force and core water saturation, a change relationship between oil phase effective permeability and core water saturation, and a change relationship between water phase effective permeability and core water saturation, which correspond to the simulation calculation of water-wet core water flooding, includes:

determining a first blocking critical pressure value of each throat, a first collaborative filling critical pressure value of each pore, a second core water saturation in an initial state, a second capillary force in the initial state, a second capillary force in a termination state and a second displacement step length;

determining the second capillary force in the initial state as the current second capillary force;

circularly performing screening on all throats and pores, and determining a throat with a first blocking critical pressure value larger than the current second capillary force and pores with a first collaborative filling critical pressure value larger than the current second capillary force; updating the water saturation of the second core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the second core corresponding to the current second capillary force; determining a second oil phase relative permeability and a second water phase relative permeability corresponding to the current second core water saturation according to the current second core water saturation and a second oil phase conductivity coefficient and a second water phase conductivity coefficient corresponding to each pore or throat; updating the current second capillary force, determining the difference between the current second capillary force and the second displacement step length as the updated current second capillary force, and determining the current second core water saturation corresponding to the current second capillary force one by one, and the second oil phase relative permeability and the second water phase relative permeability corresponding to the current second core water saturation;

ending the cycle until the current second capillary force is less than the second capillary force at the termination state.

Preferably, the performing simulation calculation of oil-wet core water flooding on the core pore network model, and determining a change relationship between capillary force and core water saturation, a change relationship between oil phase effective permeability and core water saturation, and a change relationship between water phase effective permeability and core water saturation, which correspond to the simulation calculation of oil-wet core water flooding, includes:

determining a first piston type filling critical pressure value of each throat, the water saturation of a third core in an initial state, a third capillary force in the initial state, a third capillary force in a termination state and a third displacement step length;

determining the third capillary force in the initial state as the current third capillary force;

circularly performing screening on all throats and pores, and determining the throat of which the first piston type filling critical pressure value is less than or equal to the current third capillary force and all pores communicated with the throat; updating the water saturation of the third core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the third core corresponding to the current third capillary force; determining a third oil phase relative permeability and a third water phase relative permeability corresponding to the current third core water saturation according to the current third core water saturation and a third oil phase conductivity coefficient and a third water phase conductivity coefficient corresponding to each pore or throat; updating the current third capillary force, determining the difference between the current third capillary force and the third displacement step length as the updated current third capillary force, and determining the current third core water saturation corresponding to the current third capillary force one by one, and the third oil phase relative permeability and the third water phase relative permeability corresponding to the current third core water saturation;

ending the cycle until the current third capillary force is less than the third capillary force at the end state.

Preferably, the performing simulation calculation of mixed wetting core water flooding on the core pore network model, and determining a change relationship between capillary force and core water saturation, a change relationship between oil phase effective permeability and core water saturation, and a change relationship between water phase effective permeability and core water saturation, which correspond to the simulation calculation of mixed wetting core water flooding, includes:

determining a second blocking critical pressure value of each water-wet throat, a second cooperative filling critical pressure value of each water-wet pore, a second piston type filling critical pressure value of each oil-wet throat, the water saturation of a fourth core in an initial state, a fourth capillary force in the initial state, a fourth capillary force in a stopping state and a fourth displacement step length;

determining the fourth capillary force in the initial state as the current fourth capillary force;

circularly performing screening on all throats and pores; judging whether the current first capillary force is larger than a fourth capillary force in the suspension state; screening out a throat with a second snapping critical pressure value larger than the current fourth capillary force or a pore with a second collaborative filling critical pressure value larger than the current fourth capillary force if the current first capillary force is larger than the fourth capillary force in the suspension state; if the current first capillary force is smaller than or equal to the fourth capillary force in the suspension state, screening out a throat in which the second piston type filling critical pressure value is smaller than or equal to the current fourth capillary force and all pores communicated with the throat; updating the water saturation of the fourth core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the fourth core corresponding to the current fourth capillary force; determining fourth oil phase relative permeability and fourth water phase relative permeability corresponding to the current fourth core water saturation according to the current fourth core water saturation and a fourth oil phase conductivity coefficient and a fourth water phase conductivity coefficient respectively corresponding to each pore or throat; updating the current fourth capillary force, determining the difference between the current fourth capillary force and the fourth displacement step length as the updated current fourth capillary force, and determining the current fourth core water saturation corresponding to the current fourth capillary force, and the fourth oil phase relative permeability and the fourth water phase relative permeability corresponding to the current fourth core water saturation one by one;

ending the cycle until the current fourth capillary force is less than the fourth capillary force at the end state.

In another aspect, embodiments herein provide a device for calculating a capillary force and relative permeability curve, the device comprising:

a model determination module: determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

an absolute permeability determination module: performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

a displacement simulation calculation module: sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

a relationship determination module: and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

In yet another aspect, embodiments herein also provide a computer device comprising a memory, a processor, and a computer program stored on the memory, the computer program, when executed by the processor, performing the instructions of any one of the methods described above.

In yet another aspect, embodiments herein also provide a computer-readable storage medium having stored thereon a computer program, which when executed by a processor of a computer device, performs the instructions of any one of the methods described above.

According to the technical scheme provided by the embodiment, the method for obtaining the capillary force curve and the relative permeability curve has the advantages that the time consumption is short and the research efficiency is high on the basis of ensuring the experiment accuracy by establishing the core pore network model and performing various displacement simulation calculations on the model.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic flow chart illustrating a method for calculating a capillary force and relative permeability curve provided in embodiments herein;

FIG. 2 illustrates a cross-sectional simulated view of apertures and throats provided by embodiments herein;

fig. 3 illustrates a schematic flow diagram for determining absolute permeability of a core provided in embodiments herein;

fig. 4 shows a detailed flow diagram of the first and second steps provided by embodiments herein;

FIG. 5 illustrates a three-dimensional diagram of a simulated oil flooding process provided by embodiments herein;

FIG. 6 illustrates a three-dimensional diagram of a simulated water flooding process provided by embodiments herein;

FIG. 7 shows a schematic flow diagram for performing an oil flooding simulation as provided by embodiments herein;

FIG. 8 illustrates a comparison of an experimental process and a simulated process for oil flooding provided by embodiments herein;

FIG. 9 illustrates a schematic flow diagram for performing a water-wet core flooding simulation provided by embodiments herein;

FIG. 10 shows a comparison chart of a water-wet core flooding experimental process and a simulation process performed as provided by embodiments herein;

FIG. 11 illustrates a schematic flow diagram for performing an oil-wet core flooding simulation provided by embodiments herein;

FIG. 12 shows a comparison of a water flooding experimental procedure and a simulation procedure for oil-wet cores provided by embodiments herein;

FIG. 13 illustrates a schematic flow diagram for performing a mixed wetting core flooding simulation as provided by embodiments herein;

FIG. 14 shows a comparison chart of a hybrid wetting core flooding experimental process and a simulation process performed as provided by embodiments herein;

FIG. 15 is a block diagram illustrating a computing device for capillary force and relative permeability curves provided in embodiments herein;

fig. 16 shows a schematic structural diagram of a computer device provided in an embodiment herein.

Description of the symbols of the drawings:

100. a model determination module;

200. an absolute permeability determination module;

300. a displacement simulation calculation module;

400. a relationship determination module;

1602. a computer device;

1604. a processor;

1606. a memory;

1608. a drive mechanism;

1610. an input/output module;

1612. an input device;

1614. an output device;

1616. a presentation device;

1618. a graphical user interface;

1620. a network interface;

1622. a communication link;

1624. a communication bus.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments herein without making any creative effort, shall fall within the scope of protection.

The capillary force curve refers to a curve of a change relation between capillary force and water saturation of the core, and the relative permeability curve refers to a curve of a change relation between relative permeability of an oil phase and water saturation of the core and a curve of a change relation between relative permeability of a water phase and water saturation of the core in an oil-water or water-oil displacement process.

Because the multiphase flow of oil, gas and water in the core of the reservoir of the oil and gas reservoir is an important problem in the field of oil and gas field development, the flow characteristics of multiphase fluid are represented by mainly depending on capillary force and relative permeability curves in a macroscopic view. In order to obtain the capillary force and relative permeability curve, in the prior art, after an accurate experiment of an indoor core is mainly performed, experimental data are analyzed, and then the capillary force and relative permeability curve of the core is obtained.

However, since the accurate indoor core experiment takes a long time, the time for the cores with different permeabilities is about several days or even months. This will greatly expend the efforts of researchers and lead to a reduction in research efficiency. Therefore, there is a need for a method for calculating capillary force and relative permeability curves, which can improve the efficiency of obtaining the capillary force and relative permeability curves of the core.

To solve the above problems, embodiments herein provide a method for calculating a capillary force and relative permeability curve, fig. 1 is a schematic diagram of steps of a method for calculating a capillary force and relative permeability curve provided in embodiments herein, and the present specification provides the method operation steps as described in the embodiments or flowcharts, but may include more or less operation steps based on conventional or non-inventive labor. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. When an actual system or apparatus product executes, it can execute sequentially or in parallel according to the method shown in the embodiment or the figures.

Referring to fig. 1, a method for calculating a capillary force and relative permeability curve includes:

s101: determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

s102: performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

s103: sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

s104: and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

Compared with the method for performing the indoor accurate core experiment in the prior art, the method for obtaining the capillary force curve and the relative permeability curve has the advantages that time consumption is short on the basis of ensuring the experiment accuracy and research efficiency is high by establishing the core pore network model and performing various displacement simulation calculations on the model.

The capillary force versus permeability curve is a curve of the relationship between capillary force and the change in water saturation of the core. Capillary forces, which are directed in the direction of the concave surface of the liquid, are proportional to the surface tension of the liquid and inversely proportional to the capillary radius, and are often present in the formation capillary pores as a pressure differential across the curved interface of two immiscible liquids (e.g., oil and water).

The relative permeability curve refers to a curve of a change relation between the relative permeability of an oil phase and the water saturation of the core and a curve of a change relation between the relative permeability of a water phase and the water saturation of the core in an oil-water or water-oil displacement process. Relative permeability is the ratio of the effective permeability to the absolute permeability of each phase when multiphase fluids coexist.

Referring to fig. 2, for the core, a plurality of pores and throats communicating the pores with each other are arranged in the core, and in order to improve the accuracy of simulation calculation, the cross sections of the pores and the throats are simulated into a four-pointed star shape, so that a core pore network model is determined. For the core pore network model, most of the core pore network model is a regular hexahedron, one end face of the regular hexahedron can be set as an inlet end face, and the other end face opposite to the inlet end face is an outlet end face.

The number, center coordinates, volume, inscribed circle radius, cross-sectional area, length, and whether the pore in the core pore network model is an inlet pore or an outlet pore (wherein the pore on the inlet end face is an inlet pore and the pore on the outlet end face is an outlet pore) are further determined. And determining the number, volume, inscribed circle radius, cross-sectional area, length and pore number communicated with each throat. Furthermore, the connectivity between the pores and the throat is judged by using a graph theory, the pores which are not communicated in the core pore network model are removed, and the half angle of any four-corner star-shaped pore or throat is calculated:

wherein gamma is the half angle of the four-corner star-shaped pore or throat, the sectional area of the A pore or throat, and r is the radius of the inscribed circle of the pore or throat.

The shape factor of any pore or throat section can then be calculated:

where G is the shape factor of the cross section of the aperture or throat.

And the perimeter of any aperture or throat section:

where P is the perimeter of the cross section of the aperture or throat.

Referring to fig. 3, in this embodiment, the performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core includes:

s301: performing single-phase flow simulation calculation on the core pore network model, and determining the conductivity coefficient of each pore in the core pore network model and the conductivity coefficients among pores which are mutually communicated;

s302: determining the pressure of each pore according to the conductivity coefficient among the interconnected pores;

s303: and determining the absolute permeability of the core according to the pressure of each pore and the corresponding conductivity coefficient.

When the simulation calculation of the single-phase flow is carried out, the single-phase fluid is water or oil, and the simulation calculation of the core permeability is generally carried out by using water. The conductivity of any pore or throat is first calculated:

where T is the conductivity of the aperture or throat and L is the length of the aperture or throat.

And further determining the conductivity between any two pores (pore i and pore j):

wherein T is^’Is the conductivity between pore i and pore j, T_iIs the pore i conductivity, T_jIs the conductivity of the pore j, T_ijThe conductance of the throat connecting the pores i and j.

An adjacency matrix can then be established by using the connectivity between the pores and the throat through a graph theory method, wherein the coefficient of the adjacency matrix is the conductivity between any two pores. And converting the adjacency matrix into a sparse matrix, setting the pressure value of the inlet end face and the pressure value of the outlet end face as any value due to the fact that boundary conditions are needed for solving the sparse matrix, solving by using a solving algorithm of the large-scale sparse matrix, and obtaining the pressure of each pore after solving.

Namely, the flow rate of the outlet end face can be determined:

wherein q is the flow rate of the outlet end face, p_iPressure of a pore i communicating with the outlet end face, p_outIs the pressure at the outlet end face, N_CThe number of the pores communicated with the end face of the outlet.

The absolute permeability is then obtained by darcy's law:

wherein k is_absMu is the viscosity taken as 1, S is the area of the outlet end face, l is the distance from the inlet end face to the outlet end face, p is the absolute permeability_inIs the pressure at the inlet end face.

Referring to fig. 4, in this embodiment, sequentially performing displacement simulation calculations of multiple displacement types on the core pore network model, and respectively determining a change relationship between a capillary force and a core water saturation, a change relationship between an oil phase effective permeability and a core water saturation, and a change relationship between a water phase effective permeability and a core water saturation, which correspond to each displacement simulation calculation, includes the following two steps:

first step S401:

performing oil-flooding water simulation calculation on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the oil-flooding water simulation calculation;

second step S402:

performing simulation calculation of water-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of water-wet core water flooding;

or performing simulation calculation of oil-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of the oil-wet core water flooding;

or performing simulation calculation of mixed wetting core water flooding on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulation calculation of the mixed wetting core water flooding.

Referring to fig. 5 and 6, the deeper the color in fig. 5 and 6 indicates the higher the saturation of the core, and the lighter the color indicates the higher the water saturation of the core. Specifically, the process of performing oil-driving water as shown in fig. 5 is a reservoir formation process of an oil reservoir, a reservoir is filled with water at first, and pores and throats are filled with water in an initial state. Firstly, the core water saturation corresponding to different capillary forces, the core water saturation corresponding to different oil phase effective permeabilities and the core water saturation corresponding to different water phase effective permeabilities can be gradually recorded in the process of gradually displacing the water phase by the oil phase. Then, as shown in fig. 6, the subsequent simulation calculation of water-wet core water flooding, oil-wet core water flooding or mixed-wetting core water flooding is determined according to whether the core wettability is water-wet, oil-wet or mixed-wetting, and the core water saturation corresponding to different capillary forces, the core water saturation corresponding to different oil-phase effective permeabilities and the core water saturation corresponding to different water-phase effective permeabilities can be gradually recorded according to the process that the oil phase is gradually displaced by the water phase.

Referring to fig. 7, in this embodiment, the performing a simulation calculation of oil-flooding water on the core pore network model, and determining a change relationship between a capillary force and a core water saturation, a change relationship between an oil phase effective permeability and a core water saturation, and a change relationship between a water phase effective permeability and a core water saturation, which correspond to the simulation calculation of oil-flooding water, includes:

s701: determining a threshold pressure value of each throat, the water saturation of a first rock core in an initial state, a first capillary force in the initial state, a first capillary force in a termination state and a first displacement step length;

s702: determining a first capillary force in an initial state as a current first capillary force;

s703: circularly performing screening on all throats and pores, and determining the throat with the threshold pressure value smaller than or equal to the current first capillary force and all pores communicated with the throat; updating the water saturation of the first core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the first core corresponding to the current first capillary force; determining a first oil phase relative permeability and a first water phase relative permeability corresponding to the current first core water saturation according to the current first core water saturation and a first oil phase conductivity coefficient and a first water phase conductivity coefficient corresponding to each pore or throat; updating the current first capillary force, determining the sum of the current first capillary force and the first displacement step length as the updated current first capillary force, and determining the current first core water saturation corresponding to the current first capillary force one by one, and the first oil phase relative permeability and the first water phase relative permeability corresponding to the current first core water saturation;

s704: and ending the cycle until the current first capillary force is greater than the first capillary force in the terminal state.

Referring to fig. 8, where the experimental values are actual experimental data for comparison with simulated values, which are experimental data simulated according to the calculation method herein, it appears that the data trends of the simulated values and the experimental values are the same in comparison, and thus the accuracy of the capillary force and relative permeability curve obtained by the calculation method herein is high. Specifically, since the pores and the throat are filled with the water phase in the initial state, the water saturation S of the first core in the initial state _w1, representing that the water saturation in the pores and throat is 1 at this time. The oil phase enters the reservoir under the action of hydrocarbon generation pressure, and is overcomeCapillary forces displace the water phase, eventually forming the reservoir, at which point the rock is water wet. In the process, the capillary force is gradually increased, the throat plays a main restraint role, and if the capillary force is greater than the threshold pressure value of the throat in the increasing process, the oil phase enters the corresponding throat to displace the water phase. Threshold pressure value of any throat:

wherein

Is the threshold pressure value of the throat, σ is the interfacial tension, θ_rIs the contact angle during oil flooding, A_α1Is a wetting phase with no dimensional corner area.

The method for calculating the dimensionless corner area of the wetting phase is as follows:

the first capillary force in the initial state may be set to the minimum threshold pressure value among the threshold pressure values of all throats obtained through the above formula (8), and the first capillary force in the termination state may be set to the maximum threshold pressure value among the threshold pressure values of all throats obtained through the above formula (8). Further, the first displacement step size may be equal in each step, or may be different in each step, and the specific form of the first displacement step size is not limited herein. If each step is equal, the difference between the first capillary force in the termination state and the first capillary force in the initial state can be taken, the difference is divided equally, the number of the divisions can be set according to the actual situation, for example, the division can be equally divided into 10 times, 15 times and the like, and the difference is divided by the number of the divisions to obtain the first displacement step length.

Determining the first capillary force in the initial state as the current first capillary force, and performing loop operation on all throats and poresScreening, namely screening the throat with the threshold pressure value less than or equal to the current first capillary force and all pores communicated with the throat, and screening the water saturation of the screened throat and pores from the original S_wUpdate 1 is:

wherein S_wWater saturation of the throat or pore, p_cIs the current first capillary force.

Of course, the water saturation of the unselected throats or pores is S_wDetermining the current first core water saturation corresponding to the current first capillary force according to the water saturation after the screened throats and pores are updated and the water saturation of the unselected throats and pores, namely:

wherein S_{w total}The current first core water saturation, S, corresponding to the current first capillary force_w1For the water saturation, V, after the screened throat and pore have been updated₁For the volume of throat and pores screened, S_w2Water saturation of unscreened throats and pores, V₂The volume of the unselected throats and pores, and V the total volume of all throats and pores.

Further, calculating a first oil phase conductivity coefficient corresponding to any pore or throat:

T_o＝T(1-S_w)² (12)

wherein T is_oThe first oil phase conductivity.

Still further, the first water phase conductivity of any pore or throat is calculated as:

wherein T is_wThe first aqueous phase conductivity.

Finally, the relative permeability of the first oil phase corresponding to the current first core water saturation may be determined:

wherein k is_roThe relative permeability k of the first oil phase corresponding to the current water saturation of the first core_oAnd the effective permeability of the first oil phase corresponding to the current water saturation of the first core is obtained.

A first water phase relative permeability corresponding to the current first core water saturation may be determined:

wherein k is_rwIs the relative permeability, k, of the first water phase corresponding to the current water saturation of the first core_wAnd the effective permeability of the first water phase corresponding to the current water saturation of the first core is obtained.

Wherein the effective permeability k of the first oil phase corresponding to the current water saturation of the first core_oThe calculation method of (a) and the first water phase effective permeability k corresponding to the current first core water saturation_wAll are the same, and the effective permeability k of the first oil phase corresponding to the current water saturation of the first core_oThe calculation method of (2) is as follows:

first, the conductivity T of the first oil phase corresponding to any pore or throat is known_oThe conductivity coefficient between any two pores is obtained by using the formula (5), T in the formula (5)_iIs the first oil phase conductivity of the pore i, T_jIs the first oil phase conductivity, T, of the pore j_ijThe first oil phase conductivity coefficient is the throat between the communicated pore i and the pore j.

Then, a contiguous matrix can be established by using the communication relationship between the pores and the throat through a graph theory method, wherein the coefficient of the contiguous matrix is the first oil phase conductivity coefficient between any two pores. And converting the adjacency matrix into a sparse matrix, setting the pressure value of the inlet end face and the pressure value of the outlet end face as any value due to the fact that boundary conditions are needed for solving the sparse matrix, solving by using a solution algorithm of the large-scale sparse matrix, and obtaining the pressure of each pore corresponding to the current water saturation of the first rock core after solving.

Then, the effective permeability k of the first oil phase corresponding to the current water saturation of the first core is determined by using the formulas (6) and (7)_o. Wherein equation (7) is modified accordingly:

wherein k is_oAnd the effective permeability of the first oil phase corresponding to the current water saturation of the first core is obtained.

Similarly, calculating the effective permeability k of the first water phase corresponding to the current water saturation of the first core_wMeanwhile, the formulas (5) - (7) are also modified adaptively, wherein the formula (7) is modified correspondingly as follows:

wherein k is_wAnd the effective permeability of the first water phase corresponding to the current water saturation of the first core is obtained.

In the same way, the sum of the current first capillary force and the first displacement step is determined as the updated current first capillary force. And for the current first capillary force after each updating, determining the current first core water saturation corresponding to the current first capillary force, and the first oil phase relative permeability and the first water phase relative permeability corresponding to the current first core water saturation. The cycle is ended until the current first capillary force is greater than the first capillary force in the terminal state.

In the process, the current water saturation of the first core is taken as an abscissa, the current first capillary force, the current first oil-phase relative permeability and the current first water-phase relative permeability are taken as ordinates, a plurality of points under each abscissa can be obtained respectively, and the plurality of points under each abscissa are connected to form a first capillary force curve, a first oil-phase relative permeability curve and a first water-phase relative permeability curve.

Referring to fig. 9, in this embodiment, the performing a simulation calculation of water-wet core water flooding on the core pore network model, and determining a change relationship between a capillary force and a core water saturation, a change relationship between an oil phase effective permeability and a core water saturation, and a change relationship between a water phase effective permeability and a core water saturation, which correspond to the simulation calculation of water-wet core water flooding, includes:

s901: determining a first blocking critical pressure value of each throat, a first collaborative filling critical pressure value of each pore, a second core water saturation in an initial state, a second capillary force in the initial state, a second capillary force in a termination state and a second displacement step length;

s902: determining the second capillary force in the initial state as the current second capillary force;

s903: circularly performing screening on all throats and pores, and determining a throat with a first blocking critical pressure value larger than the current second capillary force and pores with a first collaborative filling critical pressure value larger than the current second capillary force; updating the water saturation of the second core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the second core corresponding to the current second capillary force; determining a second oil phase relative permeability and a second water phase relative permeability corresponding to the current second core water saturation according to the current second core water saturation and a second oil phase conductivity coefficient and a second water phase conductivity coefficient corresponding to each pore or throat; updating the current second capillary force, determining the difference between the current second capillary force and the second displacement step length as the updated current second capillary force, and determining the current second core water saturation corresponding to the current second capillary force one by one, and the second oil phase relative permeability and the second water phase relative permeability corresponding to the current second core water saturation;

s904: ending the cycle until the current second capillary force is less than the second capillary force at the termination state.

Referring to fig. 10, where the experimental values are actual experimental data for comparison with simulated values, which are experimental data simulated according to the calculation method herein, it appears that the data trends of the simulated values and the experimental values are the same in comparison, and thus the accuracy of the capillary force and relative permeability curve obtained by the calculation method herein is high. Specifically, the simulation of the water-wet core water flooding process keeps the condition that the existing pores and throats are filled after the oil flooding water simulation is finished, and the wetting hysteresis effect is considered. The second core water saturation at the initial state is therefore the first core water saturation at the end of the oil-flooding.

The first blocking critical pressure value when any throat is blocked is as follows:

wherein

Is the first critical pressure value of the snap, sigma is the interfacial tension, theta_aIs the contact angle in the water flooding process.

The first cooperative filling critical pressure value of any pore is:

wherein

Filling the critical pressure value a for the first cooperation₁＝0，

x is a random number between 0 and 1, and n is the number of oil-containing throats connected with corresponding pores.

When the throat is blocked by the oil phase, the throat is filled with the water phase, and then whether the pore communicated with the throat is filled with the water phase is further judged.

The second capillary force in the initial state may be set to the maximum threshold pressure value among the threshold pressure values of all throats obtained by the above formula (8), and the second capillary force in the termination state may be set to 0. Further, the second displacement step size may be equal in each step, or may be different in each step, and the specific form of the second displacement step size is not limited herein. If each step is equal, the difference between the second capillary force in the termination state and the second capillary force in the initial state can be taken, the difference is divided equally, the number of the divisions can be set according to the actual situation, for example, the division can be equally divided into 10 times, 15 times and the like, and the difference is divided by the number of the divisions to obtain the second displacement step length.

And determining the second capillary force in the initial state as the current second capillary force, then circularly performing screening on all throats and pores, and screening out the throats of which the first blocking critical pressure value is greater than the current second capillary force and the pores of which the first collaborative filling critical pressure value is greater than the current second capillary force. Updating the water saturation of the screened throat and pore from the water saturation of the first core when the original oil-drive water is finished to S_w＝1。

And determining the current water saturation of the second core corresponding to the current second capillary force according to the updated water saturation of the screened throats and pores and the water saturation of the unselected throats and pores in the formula (11). S in formula (11)_{w total}And the current second core water saturation corresponding to the current second capillary force.

Further, the second aperture or throat corresponding to any aperture or throat is calculated by using the above formula (12)Conductivity of oil phase, T in equation (12)_oThe second oil phase conductivity.

Further, calculating a second water phase conductivity coefficient of any pore or throat by using a formula (13), wherein T is shown in the formula (13)_wThe second aqueous phase conductivity.

Finally, a second oil phase relative permeability corresponding to the current second core water saturation may be determined using equation (14). In formula (14), k_roThe relative permeability, k, of the second oil phase corresponding to the current water saturation of the second core_oAnd the effective permeability of the second oil phase corresponding to the current water saturation of the second core is obtained.

The second water phase relative permeability corresponding to the current second core water saturation may be determined using equation (15). K in formula (15)_rwThe relative permeability, k, of the second water phase corresponding to the current water saturation of the second core_wAnd the effective permeability of the second water phase corresponding to the current water saturation of the second core is obtained.

Wherein the effective permeability k of the second oil phase corresponding to the current water saturation of the second core_oThe effective permeability k of the second water phase corresponding to the current water saturation of the second core is calculated_wAll are the same, and the effective permeability k of the second oil phase corresponding to the current water saturation of the second core_oThe calculation method of (2) is as follows:

first, the conductivity T of the second oil phase corresponding to any pore or throat is known_oThe conductivity coefficient between any two pores is obtained by using the formula (5), T in the formula (5)_iIs the second oil phase conductivity of the pore i, T_jIs the second oil phase conductivity, T, of the pore j_ijAnd the second oil phase conductivity coefficient is the conductivity coefficient of the throat channel communicated between the pore i and the pore j.

Then, a contiguous matrix can be established by using the communication relationship between the pores and the throat through a graph theory method, wherein the coefficient of the contiguous matrix is the second oil phase conductivity coefficient between any two pores. And converting the adjacency matrix into a sparse matrix, setting the pressure value of the inlet end face and the pressure value of the outlet end face as any value due to the fact that boundary conditions are needed for solving the sparse matrix, solving by using a solution algorithm of the large-scale sparse matrix, and obtaining the pressure of each pore corresponding to the current water saturation of the second core after solving.

Then, the effective permeability k of the second oil phase corresponding to the current water saturation of the second core is determined by using the formulas (6) and (7)_o. Wherein the formula (7) is modified correspondingly to the formula (16), and k in the formula (16)_oAnd the effective permeability of the second oil phase corresponding to the current water saturation of the second core is obtained.

Similarly, calculating the effective permeability k of the second water phase corresponding to the current water saturation of the second core_wMeanwhile, the formulas (5) - (7) are also modified adaptively, wherein the formula (7) is modified correspondingly to the formula (17), and k in the formula (17)_wAnd the effective permeability of the second water phase corresponding to the current water saturation of the second core is obtained.

In the same way, the difference between the current second capillary force and the second displacement step is determined as the updated current second capillary force. And for the current second capillary force after each updating, determining the current second core water saturation corresponding to the current second capillary force, and the second oil phase relative permeability and the second water phase relative permeability corresponding to the current second core water saturation. And ending the cycle until the current second capillary force is less than the second capillary force in the terminal state.

In the process, a current second core water saturation is taken as an abscissa, a current second capillary force, a current second oil phase relative permeability and a current second water phase relative permeability are taken as ordinates, a plurality of points under each abscissa can be obtained respectively, and the plurality of points under each abscissa are connected to form a second capillary force curve, a second oil phase relative permeability curve and a second water phase relative permeability curve.

Referring to fig. 11, in this embodiment, the performing a simulation calculation of oil-wet core water flooding on the core pore network model, and determining a change relationship between a capillary force and a core water saturation, a change relationship between an oil phase effective permeability and a core water saturation, and a change relationship between a water phase effective permeability and a core water saturation, which correspond to the simulation calculation of the oil-wet core water flooding, includes:

s1101: determining a first piston type filling critical pressure value of each throat, the water saturation of a third core in an initial state, a third capillary force in the initial state, a third capillary force in a termination state and a third displacement step length;

s1102: determining the third capillary force in the initial state as the current third capillary force;

s1103: circularly performing screening on all throats and pores, and determining the throat of which the first piston type filling critical pressure value is less than or equal to the current third capillary force and all pores communicated with the throat; updating the water saturation of the third core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the third core corresponding to the current third capillary force; determining a third oil phase relative permeability and a third water phase relative permeability corresponding to the current third core water saturation according to the current third core water saturation and a third oil phase conductivity coefficient and a third water phase conductivity coefficient corresponding to each pore or throat; updating the current third capillary force, determining the difference between the current third capillary force and the third displacement step length as the updated current third capillary force, and determining the current third core water saturation corresponding to the current third capillary force one by one, and the third oil phase relative permeability and the third water phase relative permeability corresponding to the current third core water saturation;

s1104: ending the cycle until the current third capillary force is less than the third capillary force at the end state.

Referring to fig. 12, where the experimental values are actual experimental data for comparison with simulated values, which are experimental data simulated according to the calculation method herein, it appears that the data trends of the simulated values and the experimental values are the same in comparison, and thus the accuracy of the capillary force and relative permeability curve obtained by the calculation method herein is high. Specifically, for the simulation of the oil-wet core water flooding process, the water saturation of the third core in the initial state is the water saturation of the first core at the end of oil flooding.

When in use

When the temperature of the water is higher than the set temperature,

the first piston type filling critical pressure value of any throat is as follows:

wherein

Filling a critical pressure value for the first piston, sigma is an interfacial tension, theta_aIs the contact angle in the water flooding process.

Wherein A is_α2Is a wetting phase with no dimensional corner area.

When in use

When the water phase is completely filled, the corresponding first piston type filling critical pressure value is as follows:

let the third capillary force in the initial state be 0, and the third capillary force in the end state be the minimum value of the first piston-type filling critical pressure values of any one of the throats in the above-mentioned formula (20) and formula (22).

Further, the third displacement step size may be equal in each step, or may be different in each step, and the specific form of the third displacement step size is not limited herein. If each step is equal, the difference between the third capillary force in the termination state and the third capillary force in the initial state can be taken, the difference is divided equally, the number of the divisions can be set according to the actual situation, for example, the division can be equally divided into 10 times, 15 times and the like, and the third displacement step length is obtained by dividing the difference by the number of the divisions.

And determining the third capillary force in the initial state as the current third capillary force, and then circularly performing screening on all throats and pores, and screening the throats of which the first piston type filling critical pressure value is less than or equal to the current third capillary force and all pores communicated with the throats. Updating the water saturation of the screened throat and pore from the water saturation of the first core when the original oil-drive water is finished to S_w＝1。

And (4) according to the formula (11), determining the current water saturation of the third core corresponding to the current third capillary force according to the updated water saturation of the screened throats and pores and the water saturation of the unselected throats and pores. S in formula (11)_{w total}And the current third core water saturation corresponding to the current third capillary force.

Further, the third oil phase conductivity coefficient corresponding to any pore or throat is calculated by using the formula (12), wherein T is shown in the formula (12)_oThe conductivity of the third oil phase.

Further, the third water phase conductivity coefficient of any pore or throat is calculated by using a formula (13), wherein T is shown in the formula (13)_wThe conductivity of the third aqueous phase.

Finally, a third oil phase relative permeability corresponding to the current third core water saturation may be determined using equation (14). In formula (14), k_roThe relative permeability k of the third oil phase corresponding to the current water saturation of the third core_oAnd the effective permeability of the third oil phase corresponding to the current water saturation of the third core is obtained.

The third water phase relative permeability corresponding to the current third core water saturation may be determined using equation (15). K in formula (15)_rwThe relative permeability, k, of the third water phase corresponding to the current water saturation of the third core_wIs as followsAnd the effective permeability of a third water phase corresponding to the water saturation of the first third core.

Wherein the effective permeability k of the third oil phase corresponding to the current water saturation of the third core_oThe effective permeability k of the third water phase corresponding to the current water saturation of the third core is calculated_wAll are the same, and the effective permeability k of the third oil phase corresponding to the current water saturation of the third rock core_oThe calculation method of (2) is as follows:

first, the conductivity T of the third oil phase corresponding to any pore or throat is known_oThe conductivity coefficient between any two pores is obtained by using the formula (5), T in the formula (5)_iThird oil phase conductivity of pore i, T_jThird oil phase conductivity coefficient, T, of pore j_ijAnd the conductivity coefficient of the third oil phase is the conductivity coefficient of the throat channel communicated between the pore i and the pore j.

Then, a contiguous matrix can be established by using the communication relationship between the pores and the throat through a graph theory method, wherein the coefficient of the contiguous matrix is the third oil phase conductivity coefficient between any two pores. And converting the adjacency matrix into a sparse matrix, setting the pressure value of the inlet end face and the pressure value of the outlet end face as any value due to the fact that boundary conditions are needed for solving the sparse matrix, solving by using a solution algorithm of the large-scale sparse matrix, and obtaining the pressure of each pore corresponding to the current water saturation of the third rock core after solving.

Then, the effective permeability k of the third oil phase corresponding to the current water saturation of the third core is determined by using the formulas (6) and (7)_o. Wherein the formula (7) is modified correspondingly to the formula (16), and k in the formula (16)_oAnd the effective permeability of the third oil phase corresponding to the current water saturation of the third core is obtained.

Similarly, calculating the effective permeability k of the third water phase corresponding to the current water saturation of the third core_wMeanwhile, the formulas (5) - (7) are also modified adaptively, wherein the formula (7) is modified correspondingly to the formula (17), and k in the formula (17)_wAnd the effective permeability of the third water phase corresponding to the current water saturation of the third core is obtained.

In the same way, the difference between the current third capillary force and the third displacement step is determined as the updated current third capillary force. And for the current third capillary force after each updating, determining the current third core water saturation corresponding to the current third capillary force, and the third oil phase relative permeability and the third water phase relative permeability corresponding to the current third core water saturation. The cycle is ended until the current third capillary force is less than the third capillary force in the terminal state.

In the process, the current water saturation of the third core is taken as an abscissa, the current third capillary force, the current third oil phase relative permeability and the current third water phase relative permeability are taken as ordinates, a plurality of points under each abscissa can be obtained respectively, and the plurality of points under each abscissa are connected to form a third capillary force curve, a third oil phase relative permeability curve and a third water phase relative permeability curve.

Referring to fig. 13, in this embodiment, the performing simulation calculation of mixed wetting core water flooding on the core pore network model, and determining a change relationship between a capillary force and a core water saturation, a change relationship between an oil phase effective permeability and a core water saturation, and a change relationship between a water phase effective permeability and a core water saturation, which correspond to the simulation calculation of mixed wetting core water flooding, includes:

s1301: determining a second blocking critical pressure value of each water-wet throat, a second cooperative filling critical pressure value of each water-wet pore, a second piston type filling critical pressure value of each oil-wet throat, the water saturation of a fourth core in an initial state, a fourth capillary force in the initial state, a fourth capillary force in a stopping state and a fourth displacement step length;

s1302: determining the fourth capillary force in the initial state as the current fourth capillary force;

s1303: circularly performing screening on all throats and pores; judging whether the current first capillary force is larger than a fourth capillary force in the suspension state; screening out a throat with a second snapping critical pressure value larger than the current fourth capillary force or a pore with a second collaborative filling critical pressure value larger than the current fourth capillary force if the current first capillary force is larger than the fourth capillary force in the suspension state; if the current first capillary force is smaller than or equal to the fourth capillary force in the suspension state, screening out a throat in which the second piston type filling critical pressure value is smaller than or equal to the current fourth capillary force and all pores communicated with the throat; updating the water saturation of the fourth core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the fourth core corresponding to the current fourth capillary force; determining fourth oil phase relative permeability and fourth water phase relative permeability corresponding to the current fourth core water saturation according to the current fourth core water saturation and a fourth oil phase conductivity coefficient and a fourth water phase conductivity coefficient respectively corresponding to each pore or throat; updating the current fourth capillary force, determining the difference between the current fourth capillary force and the fourth displacement step length as the updated current fourth capillary force, and determining the current fourth core water saturation corresponding to the current fourth capillary force, and the fourth oil phase relative permeability and the fourth water phase relative permeability corresponding to the current fourth core water saturation one by one;

s1304: ending the cycle until the current fourth capillary force is less than the fourth capillary force at the end state.

Specifically, because the rock core is a mixed and wetted rock core, the pores in the rock core with a set percentage can be set as oil-wet pores according to requirements, the throat communicated with the pores is also an oil-wet throat, the rest of the pores are water-wet pores, and the throat communicated with the pores is a water-wet throat, wherein the set percentage can be 50%, 60% and the like. The oil-wet holes and the oil-wet throats may be subjected to simulation calculation according to the above steps S501 to S504, and the water-wet holes and the water-wet throats may be subjected to simulation calculation according to the above steps S401 to S404.

Referring to fig. 14, where the experimental values are actual experimental data for comparison with simulated values, which are experimental data simulated according to the calculation method herein, it appears that the data trends of the simulated values and the experimental values are the same in comparison, and thus the accuracy of the capillary force and relative permeability curve obtained by the calculation method herein is high. Specifically, the simulation of the water-wet core water flooding process keeps the condition that the existing pores and throats are filled after the oil flooding water simulation is finished, and the wetting hysteresis effect is considered.

Determining a second blocking critical pressure value when any water wet throat is blocked according to the formula (18), wherein the second blocking critical pressure value is obtained in the formula (18)

Is the second critical pressure value of the snap.

Determining a second synergistic fill critical pressure value for any of the water-wet pores by the above equation (19), wherein equation (19) is

The critical pressure value is filled for the second cooperative filling.

Contact angle in water flooding process

When the temperature of the water is higher than the set temperature,

determining a second piston packing critical pressure value for any oil wet throat by equation (20) wherein

Filling the second piston with a critical pressure value

Contact angle in water flooding process

And (3) during the process, no oil film exists after the pore or throat is subjected to piston filling, the water phase is completely filled, and the second piston filling critical pressure value of any oil-wet throat is determined by a formula (22).

And the water saturation of the fourth core in the initial state is the water saturation of the first core at the end of oil flooding. The fourth capillary force in the initial state may be set to the maximum threshold pressure value among the threshold pressure values of all throats obtained by the above formula (8), the fourth capillary force in the suspension state may be set to 0, and the fourth capillary force in the termination state may be set to the minimum value among the second piston filling critical pressure values of any oil-wet throat.

The fourth displacement step size may be equal in each step or different in each step, and the specific form of the fourth displacement step size is not limited herein. If each step is equal, the difference between the fourth capillary force in the termination state and the fourth capillary force in the initial state can be taken, the difference is divided equally, the number of the divisions can be set according to the actual situation, for example, the division can be equally divided into 10 times, 15 times and the like, and the difference is divided by the number of the divisions to obtain the fourth driving step length.

The fourth capillary force in the initial state is determined as the current fourth capillary force. Because the core is a mixed wetting core, the current first capillary force is gradually decreased from the fourth capillary force in the initial state according to the fourth displacement step length, and the water-wet pores and the water-wet throat are displaced firstly in the whole process: and screening out the throat in which the second blocking critical pressure value is greater than the current fourth capillary force, or screening out the pores in which the second collaborative filling critical pressure value is greater than the current fourth capillary force. And when the current fourth capillary force is reduced to the fourth capillary force in the suspension state, representing that the displacement of the water-wet pores and the water-wet throats is finished, starting to displace the oil-wet pores and the oil-wet throats: and screening the throat in which the second piston type filling critical pressure value is less than or equal to the current fourth capillary force and all pores communicated with the throat.

Along with the displacement, in the displacement process of each step, the water saturation of the screened throat and pores is updated to S from the first core water saturation when the original oil-drive water is finished_w＝1。

And (4) according to the formula (11), determining the current fourth core water saturation corresponding to the current fourth capillary force according to the water saturation after the screened throats and pores are updated and the water saturation of the unselected throats and pores. S in formula (11)_{w total}Is the current fourth capillary force pairCurrent fourth core water saturation.

Further, the fourth oil phase conductivity coefficient corresponding to any pore or throat is calculated by using the formula (12), wherein T is shown in the formula (12)_oThe fourth oil phase conductivity.

Further, the fourth water phase conductivity coefficient of any pore or throat is calculated by using the formula (13), wherein T is shown in the formula (13)_wThe fourth aqueous phase conductivity.

Finally, a fourth oil phase relative permeability corresponding to the current fourth core water saturation may be determined using equation (14). In formula (14), k_roA fourth oil phase relative permeability, k, corresponding to the current fourth core water saturation_oAnd the effective permeability of the fourth oil phase corresponding to the current water saturation of the fourth core is obtained.

A fourth water phase relative permeability corresponding to the current fourth core water saturation may be determined using equation (15). K in formula (15)_rwThe fourth water phase relative permeability, k, corresponding to the current fourth core water saturation_wAnd the effective permeability of the fourth water phase corresponding to the current water saturation of the fourth core is obtained.

Wherein the effective permeability k of the fourth oil phase corresponding to the current water saturation of the fourth core_oThe effective permeability k of the fourth water phase corresponding to the current water saturation of the fourth core is calculated_wAll are the same, and the effective permeability k of the fourth oil phase corresponding to the current water saturation of the fourth rock core_oThe calculation method of (2) is as follows:

firstly, the fourth oil phase conductivity T corresponding to any pore or throat is known_oThe conductivity coefficient between any two pores is obtained by using the formula (5), T in the formula (5)_iFourth oil phase conductivity, T, of pore i_jIs the fourth oil phase conductivity, T, of pore j_ijAnd the fourth oil phase conductivity coefficient is the conductivity coefficient of the throat channel communicated between the pore i and the pore j.

Then, a adjacency matrix can be established by using the communication relationship between the pores and the throat through a graph theory method, wherein the coefficient of the adjacency matrix is the fourth oil phase conductivity coefficient between any two pores. And converting the adjacency matrix into a sparse matrix, setting the pressure value of the inlet end face and the pressure value of the outlet end face as any value due to the fact that boundary conditions are needed for solving the sparse matrix, solving by using a solution algorithm of the large-scale sparse matrix, and obtaining the pressure of each pore corresponding to the current fourth rock core water saturation after solving.

Then, the effective permeability k of the fourth oil phase corresponding to the current water saturation of the fourth core is determined by using the formulas (6) and (7)_o. Wherein the formula (7) is modified correspondingly to the formula (16), and k in the formula (16)_oAnd the effective permeability of the fourth oil phase corresponding to the current water saturation of the fourth core is obtained.

Similarly, calculating the effective permeability k of the fourth water phase corresponding to the current water saturation of the fourth core_wMeanwhile, the formulas (5) - (7) are also modified adaptively, wherein the formula (7) is modified correspondingly to the formula (17), and k in the formula (17)_wAnd the effective permeability of the fourth water phase corresponding to the current water saturation of the fourth core is obtained.

In the same way, the difference between the current fourth capillary force and the fourth displacement step is determined as the updated current fourth capillary force. And for the current fourth capillary force after each updating, determining the current fourth core water saturation corresponding to the current fourth capillary force, and the fourth oil phase relative permeability and the fourth water phase relative permeability corresponding to the current fourth core water saturation. And ending the cycle until the current fourth capillary force is less than the fourth capillary force at the termination state.

In the process, the current fourth core water saturation is taken as an abscissa, the current fourth capillary force, the fourth oil phase relative permeability and the fourth water phase relative permeability are taken as ordinates, a plurality of points under each abscissa can be obtained respectively, and the plurality of points under each abscissa are connected to form a fourth capillary force curve, a fourth oil phase relative permeability curve and a fourth water phase relative permeability curve.

Based on the above-mentioned method for calculating the capillary force and relative permeability curve, the embodiments herein also provide a device for calculating the capillary force and relative permeability curve. The apparatus may include systems (including distributed systems), software (applications), modules, components, servers, clients, etc. that employ the methods described herein in embodiments, in conjunction with any necessary apparatus to implement the hardware. Based on the same innovative concepts, embodiments herein provide an apparatus as described in the following embodiments. Since the implementation scheme of the apparatus for solving the problem is similar to that of the method, the specific apparatus implementation in the embodiment of the present disclosure may refer to the implementation of the foregoing method, and repeated details are not repeated. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated.

Specifically, fig. 15 is a schematic block diagram of an embodiment of a computing device for a capillary force and relative permeability curve provided in an embodiment of the present disclosure, and referring to fig. 15, the computing device for a capillary force and relative permeability curve provided in an embodiment of the present disclosure includes: the model determination module 100, the absolute permeability determination module 200, the displacement simulation calculation module 300, and the relationship determination module 400.

The model determination module 100: determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

absolute permeability determination module 200: performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

the displacement simulation calculation module 300: sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

the relationship determination module 400: and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

Referring to fig. 16, based on the above-described method for calculating a capillary force and relative permeability curve, a computer device 1602 is also provided in an embodiment of the present disclosure, wherein the above-described method is executed on the computer device 1602. The computer device 1602 may include one or more processors 1604, such as one or more Central Processing Units (CPUs) or Graphics Processors (GPUs), each of which may implement one or more hardware threads. The computer device 1602 may also include any memory 1606 for storing any kind of information such as code, settings, data, etc., and in one embodiment, a computer program that runs on the memory 1606 and on the processor 1604, and when executed by the processor 1604, may perform the instructions according to the above-described methods. For example, and without limitation, memory 1606 may include any one or more of the following in combination: any type of RAM, any type of ROM, flash memory devices, hard disks, optical disks, etc. More generally, any memory may use any technology to store information. Further, any memory may provide volatile or non-volatile retention of information. Further, any memory may represent fixed or removable components of the computer device 1602. In one case, when the processor 1604 executes the associated instructions, which are stored in any memory or combination of memories, the computer device 1602 can perform any of the operations of the associated instructions. The computer device 1602 also includes one or more drive mechanisms 1608, such as a hard disk drive mechanism, an optical disk drive mechanism, or the like, for interacting with any memory.

Computer device 1602 can also include an input/output module 1610(I/O) for receiving various inputs (via an input device 1612) and for providing various outputs (via an output device 1614). One particular output mechanism may include a presentation device 1616 and an associated graphical user interface 1618 (GUI). In other embodiments, input/output module 1610(I/O), input device 1612, and output device 1614 may not be included, but merely as a computing device in a network. Computer device 1602 can also include one or more network interfaces 1620 for exchanging data with other devices via one or more communication links 1622. One or more communication buses 1624 couple the above-described components together.

Communication link 1622 may be implemented in any manner, such as over a local area network, a wide area network (e.g., the Internet), a point-to-point connection, etc., or any combination thereof. Communications link 1622 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc., as dictated by any protocol or combination of protocols.

Corresponding to the methods in fig. 1, 3, 4, 7, 9, 11, and 13, the embodiments herein also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the above-described method.

Embodiments herein also provide computer readable instructions, wherein when executed by a processor, a program thereof causes the processor to perform the method as shown in fig. 1, 3, 4, 7, 9, 11, 13.

It should be understood that, in various embodiments herein, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments herein.

It should also be understood that, in the embodiments herein, the term "and/or" is only one kind of association relation describing an associated object, meaning that three kinds of relations may exist. For example, a and/or B, may represent: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

Those of ordinary skill in the art will appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be embodied in electronic hardware, computer software, or combinations of both, and that the components and steps of the examples have been described in a functional general in the foregoing description for the purpose of illustrating clearly the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided herein, it should be understood that the disclosed system, apparatus, and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may also be an electric, mechanical or other form of connection.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments herein.

In addition, functional units in the embodiments herein may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present invention may be implemented in a form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The principles and embodiments of this document are explained herein using specific examples, which are presented only to aid in understanding the methods and their core concepts; meanwhile, for the general technical personnel in the field, according to the idea of this document, there may be changes in the concrete implementation and the application scope, in summary, this description should not be understood as the limitation of this document.

Claims (10)

1. A method for calculating a capillary force and relative permeability curve, comprising:

determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

2. The method for calculating the capillary force and relative permeability curve according to claim 1, wherein the step of performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core comprises the following steps:

performing single-phase flow simulation calculation on the core pore network model, and determining the conductivity coefficient of each pore in the core pore network model and the conductivity coefficients among pores which are mutually communicated;

determining the pressure of each pore according to the conductivity coefficient among the interconnected pores;

and determining the absolute permeability of the core according to the pressure of each pore and the corresponding conductivity coefficient.

3. The method for calculating the capillary force and relative permeability curve according to claim 2, wherein the displacement simulation calculation of a plurality of displacement types is sequentially performed on the core pore network model, and the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to each displacement simulation calculation, are respectively determined, and the method comprises the following two steps:

the first step is as follows:

performing oil-flooding water simulation calculation on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the oil-flooding water simulation calculation;

the second step is as follows:

performing simulation calculation of water-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of water-wet core water flooding;

or performing simulation calculation of oil-wet core water flooding on the core pore network model, and determining the change relationship between capillary force and core water saturation, the change relationship between oil phase effective permeability and core water saturation, and the change relationship between water phase effective permeability and core water saturation corresponding to the simulation calculation of the oil-wet core water flooding;

or performing simulation calculation of mixed wetting core water flooding on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulation calculation of the mixed wetting core water flooding.

4. The method for calculating the capillary force and relative permeability curve according to claim 3, wherein the performing oil-flooding simulation calculation on the core pore network model, and determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the oil-flooding simulation calculation, comprises:

determining a threshold pressure value of each throat, the water saturation of a first rock core in an initial state, a first capillary force in the initial state, a first capillary force in a termination state and a first displacement step length;

determining a first capillary force in an initial state as a current first capillary force;

circularly performing screening on all throats and pores, and determining the throat with the threshold pressure value smaller than or equal to the current first capillary force and all pores communicated with the throat; updating the water saturation of the first core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the first core corresponding to the current first capillary force; determining a first oil phase relative permeability and a first water phase relative permeability corresponding to the current first core water saturation according to the current first core water saturation and a first oil phase conductivity coefficient and a first water phase conductivity coefficient corresponding to each pore or throat; updating the current first capillary force, determining the sum of the current first capillary force and the first displacement step length as the updated current first capillary force, and determining the current first core water saturation corresponding to the current first capillary force one by one, and the first oil phase relative permeability and the first water phase relative permeability corresponding to the current first core water saturation;

and ending the cycle until the current first capillary force is greater than the first capillary force in the terminal state.

5. The method for calculating the capillary force and relative permeability curve according to claim 3, wherein the step of performing the simulated calculation of the water-wet core flooding on the core pore network model to determine the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulated calculation of the water-wet core flooding, comprises the steps of:

determining a first blocking critical pressure value of each throat, a first collaborative filling critical pressure value of each pore, a second core water saturation in an initial state, a second capillary force in the initial state, a second capillary force in a termination state and a second displacement step length;

determining the second capillary force in the initial state as the current second capillary force;

circularly performing screening on all throats and pores, and determining a throat with a first blocking critical pressure value larger than the current second capillary force and pores with a first collaborative filling critical pressure value larger than the current second capillary force; updating the water saturation of the second core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the second core corresponding to the current second capillary force; determining a second oil phase relative permeability and a second water phase relative permeability corresponding to the current second core water saturation according to the current second core water saturation and a second oil phase conductivity coefficient and a second water phase conductivity coefficient corresponding to each pore or throat; updating the current second capillary force, determining the difference between the current second capillary force and the second displacement step length as the updated current second capillary force, and determining the current second core water saturation corresponding to the current second capillary force one by one, and the second oil phase relative permeability and the second water phase relative permeability corresponding to the current second core water saturation;

ending the cycle until the current second capillary force is less than the second capillary force at the termination state.

6. The method for calculating the capillary force and relative permeability curve according to claim 3, wherein the step of performing simulated calculation of oil-wet core flooding on the core pore network model to determine the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulated calculation of the oil-wet core flooding, comprises the steps of:

determining a first piston type filling critical pressure value of each throat, the water saturation of a third core in an initial state, a third capillary force in the initial state, a third capillary force in a termination state and a third displacement step length;

determining the third capillary force in the initial state as the current third capillary force;

circularly performing screening on all throats and pores, and determining the throat of which the first piston type filling critical pressure value is less than or equal to the current third capillary force and all pores communicated with the throat; updating the water saturation of the third core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the third core corresponding to the current third capillary force; determining a third oil phase relative permeability and a third water phase relative permeability corresponding to the current third core water saturation according to the current third core water saturation and a third oil phase conductivity coefficient and a third water phase conductivity coefficient corresponding to each pore or throat; updating the current third capillary force, determining the difference between the current third capillary force and the third displacement step length as the updated current third capillary force, and determining the current third core water saturation corresponding to the current third capillary force one by one, and the third oil phase relative permeability and the third water phase relative permeability corresponding to the current third core water saturation;

ending the cycle until the current third capillary force is less than the third capillary force at the end state.

7. The method for calculating the capillary force and relative permeability curve according to claim 3, wherein the simulation calculation of the mixed wetting core water flooding is performed on the core pore network model, and the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation, and the change relationship between the water phase effective permeability and the core water saturation, which correspond to the simulation calculation of the mixed wetting core water flooding, are determined, and the method comprises the following steps:

determining a second blocking critical pressure value of each water-wet throat, a second cooperative filling critical pressure value of each water-wet pore, a second piston type filling critical pressure value of each oil-wet throat, the water saturation of a fourth core in an initial state, a fourth capillary force in the initial state, a fourth capillary force in a stopping state and a fourth displacement step length;

determining the fourth capillary force in the initial state as the current fourth capillary force;

circularly performing screening on all throats and pores; judging whether the current first capillary force is larger than a fourth capillary force in the suspension state; screening out a throat with a second snapping critical pressure value larger than the current fourth capillary force or a pore with a second collaborative filling critical pressure value larger than the current fourth capillary force if the current first capillary force is larger than the fourth capillary force in the suspension state; if the current first capillary force is smaller than or equal to the fourth capillary force in the suspension state, screening out a throat in which the second piston type filling critical pressure value is smaller than or equal to the current fourth capillary force and all pores communicated with the throat; updating the water saturation of the fourth core in the initial state by using the screened water saturation of the throat and the pore, and determining the current water saturation of the fourth core corresponding to the current fourth capillary force; determining fourth oil phase relative permeability and fourth water phase relative permeability corresponding to the current fourth core water saturation according to the current fourth core water saturation and a fourth oil phase conductivity coefficient and a fourth water phase conductivity coefficient respectively corresponding to each pore or throat; updating the current fourth capillary force, determining the difference between the current fourth capillary force and the fourth displacement step length as the updated current fourth capillary force, and determining the current fourth core water saturation corresponding to the current fourth capillary force, and the fourth oil phase relative permeability and the fourth water phase relative permeability corresponding to the current fourth core water saturation one by one;

ending the cycle until the current fourth capillary force is less than the fourth capillary force at the end state.

8. A device for calculating a capillary force and relative permeability curve, the device comprising:

a model determination module: determining a rock core pore network model with the cross sections of pores and throats being in a shape of a quadrangle star;

an absolute permeability determination module: performing single-phase flow simulation calculation on the core pore network model to determine the absolute permeability of the core;

a displacement simulation calculation module: sequentially carrying out displacement simulation calculation of multiple displacement types on the core pore network model, and respectively determining the change relationship between the capillary force and the core water saturation, the change relationship between the oil phase effective permeability and the core water saturation and the change relationship between the water phase effective permeability and the core water saturation corresponding to each displacement simulation calculation;

a relationship determination module: and combining the change relation between the effective permeability of the oil phase and the water saturation of the rock core and the change relation between the effective permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation with the absolute permeability of the rock core respectively, and determining the change relation between the relative permeability of the oil phase and the water saturation of the rock core and the change relation between the relative permeability of the water phase and the water saturation of the rock core corresponding to each displacement simulation calculation.

9. A computer device comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, performs the instructions of the method of any one of claims 1-7.

10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor of a computer device, is adapted to carry out the instructions of the method according to any one of claims 1-7.

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