A method for analyzing carbon dioxide injection storage potential considering rock fluid forces

Abstract

The present invention discloses a method for analyzing the storage potential of carbon dioxide injection considering the force of rock fluid, including: extracting a pore network model based on a three-dimensional rock scanning image by a center axis method; considering the rock fluid force (van der Waals force, electrostatic force, structural force) and the capillary force of the gas-water interface, establishing a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes; according to the capillary force of each pore threshold on the pore network model, using intrusion percolation to calculate the pores invaded by carbon dioxide on the pore network under different displacement pressures; according to the single pore gas-water storage analysis method, calculating the carbon dioxide saturation in the intruded pores of the pore network, and analyzing the carbon dioxide storage potential under the maximum displacement pressure. The present invention overcomes the defects of the existing method that can only consider the capillary force of the gas-water interface, but cannot consider the influence of the rock fluid force on the storage potential of carbon dioxide injection in underground rocks, and can accurately predict the carbon dioxide storage potential under different rock pore structures.

Description

Technical Field

[0001] The present invention relates to the field of carbon sequestration, and more specifically, to a method for analyzing the potential of carbon dioxide injection sequestration by taking into account the force of rock fluids. Background Art

[0002] my country has announced that it will strive to reach its carbon dioxide emissions peak before 2030 and strive to achieve carbon neutrality before 2060. Injecting carbon dioxide into underground rock saline aquifers is an effective means to achieve carbon sequestration. Accurately assessing the carbon dioxide sequestration potential of underground rocks is the key to carrying out carbon sequestration projects. At present, the evaluation of the carbon dioxide sequestration potential of underground rocks is to calculate the carbon dioxide-formation water occurrence state and carbon dioxide sequestration potential after carbon dioxide injection by considering the capillary force of the carbon dioxide-formation water interface, ignoring the influence of rock fluid forces (van der Waals forces, electrostatic forces, and structural forces) on the carbon dioxide-formation water occurrence state and sequestration potential in underground rock pores. Because the rock fluid force causes formation water to be stored in the form of a water film on the pore wall, and it is particularly obvious in deep saline aquifer rocks with nanometer pore sizes, the existing methods overestimate the carbon dioxide sequestration potential of underground rock saline aquifers, and the prediction results have large errors. On the other hand, the existing methods directly divide the grid based on the digital scanning image of the rock to simulate carbon dioxide sequestration, which is computationally intensive and time-consuming, and the accuracy is controlled by the quality of the grid division. The pore network model method extracts the rock pore structure based on the pore space of the rock digital scanning image, establishes an interconnected pore network to characterize the rock pore structure characteristics, and has a faster calculation speed than the direct grid division solution method. Therefore, it is urgent to establish a set of rapid analysis methods for the storage potential of carbon dioxide injection based on the pore network model that takes into account the force of rock fluids. Summary of the invention

[0003] The present invention is provided to solve the above-mentioned problems existing in the prior art. The present invention is a method for analyzing the carbon dioxide storage potential by injection taking into account the force of rock fluids, which overcomes the defect that the existing method can only consider the capillary force of the gas-water interface and cannot consider the influence of the force of rock fluids on the carbon dioxide storage potential of underground rocks, and can accurately and quickly predict the carbon dioxide storage potential under different rock pore structures.

[0004] The present invention specifically adopts the following technical solutions:

[0005] According to a first aspect of the present invention, a method for analyzing the storage potential of carbon dioxide injection taking into account the force of rock fluid is provided, the method comprising: extracting a pore network model based on a three-dimensional rock scanning image by using a center axis method; establishing a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes by simultaneously taking into account the force of rock fluid and the capillary force of the gas-water interface; the rock fluid force comprises van der Waals force, electrostatic force, and structural force; according to the threshold capillary force of each pore on the pore network model, using invasion percolation to calculate the pores that carbon dioxide can invade on the pore network under different displacement pressures; according to the single pore gas-water storage analysis method, calculating the carbon dioxide saturation in the invaded pores of the pore network, and analyzing the carbon dioxide storage potential under the maximum displacement pressure.

[0006] Preferably, the pore network model includes a series of interconnected pores, and the pore shape is divided by the local void space shape factor G, which is calculated by the following formula (1):

[0007]

[0008] Where A p is the cross-sectional area of ​​the local void space, P e is the local void space perimeter;

[0009] Different pore shapes are divided by the value range of the shape factor G using the following formula (2):

[0010]

[0011] Irregular triangular pores are calculated as follows:

[0012] Given three interior angles, β 1 , β 2 and β 3 , and β 1 <β 2 <β 3 , calculate β according to formula (3) and formula (4) 2 The value interval [β 2,min ,β 2,max ]:

[0013]

[0014]

[0015] Randomly select β according to the value interval 2 The value of β is calculated by the following formula (5): 1 The value of:

[0016]

[0017] Based on the determined β 1 and β 2 The value of β is obtained by the following formula (6): 3 The value of:

[0018]

[0019] Preferably, the method of simultaneously considering the rock fluid force and the capillary force of the gas-water interface to establish a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes includes:

[0020] According to the wetting angle θ r The half angles β of the three corners of the triangular pore i The size relationship between them determines whether there is water phase corner in the corner;

[0021] When there is water phase in the corner, according to the wetting angle and geometric relationship, we can get:

[0022]

[0023]

[0024]

[0025] In the formula, γ g,w represents the air-water interfacial tension, R g,w represents the radius of curvature of the air-water interface; P c_(g,w) represents the capillary force at the air-water interface; β i Indicates the corner half angle where the water phase exists (i = 1-n c ), n c Indicates the number of corners where water phase exists; A ci represents the area occupied by the water phase in corner i; b i It represents the extension length of the water phase corner on the pore wall at corner i;

[0026] When there is no water phase corner in the corner, the water phase exists in the corner in the form of wall water film;

[0027] For the water phase wall water film storage area, the area occupied by the wall water film is expressed as:

[0028]

[0029] Where h represents the thickness of the water film. The thickness of the water film is affected by the separation pressure Π, which is expressed as:

[0030] Π d (h) = Π vd (h)+Π el(h)+Π str (h) (11)

[0031] In the formula, Π vd (h),Π el (h),Π str (h) represents van der Waals force, electrostatic force, and structural force, respectively. All three forces are functions of the thickness of the water phase;

[0032] The van der Waals equation can be expressed as:

[0033]

[0034] In the formula, A 132 is the non-delayed Hasinuk constant, the subscript 132 indicates the interaction between the first phase and the second phase through the third phase; A 132 It is expressed as:

[0035]

[0036] Where A 11 , A 22 , A 33 Respectively represent the Hassinuk constants of the first phase, the second phase, and the third phase, which are solved using the Lifshitz formula:

[0037]

[0038] In the formula, k B is the Boltzmann constant, T is the temperature, ε i Indicates the dielectric constant of different phases; n i Represents the refractive index of different phases; ν e Indicates the frequency of electron absorption in the ultraviolet region, h p is Planck's constant;

[0039] The electrostatic force is controlled by the internal potential distribution of the water phase. According to the double layer theory, the electrostatic force is expressed as:

[0040]

[0041] Where Y e is the dimensionless electrostatic potential, n ∞ is the ion concentration, χ is the reciprocal of the Debye length, and the dimensionless electrostatic potential Ye and the Debye length χ are expressed as:

[0042]

[0043]

[0044]

[0045] In the formula, Ψe represents electrostatic potential; e is the electron charge, dimensionless; z is the ion valence; ε 0 represents the dielectric constant of vacuum; ε 3 represents the dielectric constant of water phase;

[0046] Structural force Π str (h) can be expressed as:

[0047] Π str (h) = K str exp(-h / λ str ) (19)

[0048] In the formula, K str ,λ str It is a parameter used to describe the magnitude and characteristic length of structural forces;

[0049] Displacement pressure P g,w The relationship between capillary force and separation pressure is expressed as:

[0050] P g,w =P c_(g,w) +Π d (h) (20)

[0051] The separation pressure at the wall is determined by the displacement pressure, and the water film thickness is calculated by the relationship between the separation pressure and the water film thickness. The threshold capillary force at which carbon dioxide begins to invade the irregular pores saturated with water is expressed as:

[0052]

[0053]

[0054]

[0055] When the displacement pressure P g,w When the capillary force is greater than the threshold value expressed in formula (21), carbon dioxide invades the irregular pores. After invasion, the carbon dioxide saturation in the irregular pores at different displacement pressures is calculated by formula (24):

[0056]

[0057] The numerator of the formula consists of two parts. The first part is the area occupied by the wall water film, and the second part is the area occupied by the water phase corner. The proportion and size of the two parts change with the displacement pressure. The expression of water phase saturation in square pores is the same as formula (24). The carbon dioxide saturation under different displacement pressures in circular pores is expressed as:

[0058]

[0059] Preferably, according to the wetting angle θr The half angles β of the three corners of the triangular pore i The size relationship between them determines whether there is water phase corner in the corner, including:

[0060] When θ r <π / 2-β i When , there is a water phase corner in this corner;

[0061] When θ r ≥π / 2-β i When , there is no water phase corner in this corner.

[0062] Preferably, the method of calculating the pores that carbon dioxide can invade on the pore network under different displacement pressures by using invasion and percolation according to the threshold capillary force of each pore on the pore network model comprises:

[0063] The threshold capillary force of each pore on the pore network is calculated and compared with the carbon dioxide displacement pressure to find the pores and throats whose threshold capillary force is less than the displacement pressure. According to the connectivity graph principle, pores connected to the pores at the carbon dioxide injection end and whose threshold capillary force is less than the displacement pressure are searched to obtain the pores that carbon dioxide can invade under different displacement pressures.

[0064] Preferably, the method of calculating the carbon dioxide saturation in the intrusion pores of the pore network according to the single pore gas-water storage analysis method and analyzing the carbon dioxide storage potential under the maximum displacement pressure includes:

[0065] The carbon dioxide saturation on the pore network model after carbon dioxide injection at a given displacement pressure is calculated by the following formula (26):

[0066]

[0067] Where V pi represents the pore volume of each intruded pore; n 1 Indicates the number of intruded pores; V pore represents the total pore volume of the pore network, S co2_loc (P g,w ) represents the carbon dioxide saturation in each invaded pore at different displacement pressures.

[0068] According to a second aspect of the present invention, there is provided a device for analyzing the storage potential of carbon dioxide injection taking into account the force of rock fluid, the device comprising: an extraction module configured to extract a pore network model based on a three-dimensional rock scanning image by using a center axis method; an establishment module configured to simultaneously consider the rock fluid force and the capillary force of the gas-water interface, and establish a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes; the rock fluid force includes van der Waals force, electrostatic force, and structural force; a pore calculation module configured to calculate the pores that carbon dioxide can invade on the pore network under different displacement pressures according to the threshold capillary force of each pore on the pore network model by using invasion percolation; and an analysis module configured to calculate the carbon dioxide saturation in the invaded pores of the pore network according to the single pore gas-water storage analysis method, and analyze the carbon dioxide storage potential under the maximum displacement pressure.

[0069] According to a third aspect of the present invention, there is provided an electronic device, comprising: a controller; and a memory for storing one or more programs, wherein when the one or more programs are executed by the controller, the controller implements the analysis method as described above.

[0070] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium, characterized in that computer-readable instructions are stored thereon, and when the computer-readable instructions are executed by a processor of a computer, the computer executes the analysis method as described above.

[0071] According to a fifth aspect of the present invention, a computer program product is provided, which includes computer instructions stored in a computer-readable storage medium, and is characterized in that a processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the analysis method as described above.

[0072] The beneficial effects of the present invention are:

[0073] (1) The carbon dioxide storage potential analysis method considering the rock fluid force proposed in the present invention overcomes the defect that the existing method can only consider the capillary force of the gas-water interface but cannot consider the influence of the rock fluid force on the carbon dioxide storage potential of underground rocks. It can accurately and quickly predict the carbon dioxide storage potential under different rock pore structures.

[0074] (2) The carbon dioxide injection storage potential analysis method considering the rock fluid force established in the present invention conducts carbon dioxide-formation water storage state and storage potential analysis through a pore network model. Since the pore network model performs analysis and calculation based on the analytical solution calculation results in each pore, compared with the traditional direct grid division numerical calculation method, the calculation speed is greatly improved while ensuring the calculation accuracy, which is convenient for engineering promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0076] Figure 1 A schematic flow chart of a method for analyzing carbon dioxide injection storage potential taking into account the force of rock fluids in an embodiment of the present invention;

[0077] Figure 2 This is a three-dimensional CT scan image of deep saline layer rock in an embodiment of the present invention, where black represents pore space and white represents skeleton;

[0078] Figure 3 The pore network model is obtained by extracting the centered axis method of the three-dimensional CT scanning image of the deep saline layer rock in the embodiment of the present invention;

[0079] Figure 4 Schematic diagram of the storage state of carbon dioxide-formation water in irregular pores in an embodiment of the present invention;

[0080] Figure 5 The results of the analysis of the carbon dioxide saturation in the 10 nm equilateral triangle pores as the displacement pressure changes in the embodiment of the present invention are compared with the results of the existing method that only considers the gas-water capillary force;

[0081] Figure 6 The distribution of carbon dioxide intrusion pores on the pore network model at different displacement pressure stages in the embodiment of the present invention. Dark colors indicate carbon dioxide intrusion into pores, and light colors indicate carbon dioxide not intruding into pores. The carbon dioxide saturation (a) S at different displacement pressure stages co2 =0(b)S co2 =0.1(c)S co2 =0.24(d)S co2 =0.34(e)S co2 =0.48(f)S co2 =0.59(g)S co2 =0.69(g)S co2 =0.83;

[0082] Figure 7 The results of the analysis of the change of carbon dioxide saturation with displacement pressure on the pore network model in the embodiment of the present invention are compared with the results of the existing method that only considers the gas-water capillary force;

[0083] Figure 8It is a structural diagram of a device for analyzing carbon dioxide injection storage potential taking into account the force of rock fluid in an embodiment of the present invention. DETAILED DESCRIPTION

[0084] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments, but are not intended to limit the present invention. For the various steps described herein, if there is no necessity for a causal relationship between each other, the order in which they are described as examples herein should not be regarded as a limitation, and those skilled in the art should know that they can be adjusted in order, as long as the logic between them is not destroyed, resulting in the inability to implement the entire process.

[0085] Please refer to Figure 2 As shown, this embodiment takes the three-dimensional CT scanning image of deep saline aquifer rocks in my country as an example. A method for analyzing the potential of carbon dioxide injection storage considering the force of rock fluid is provided. The core process of this method can be found in Figure 1 As shown, in the specific implementation, the following steps are included:

[0086] S1, extracting pore network model based on rock 3D scanning image using center axis method;

[0087] In this embodiment, please refer to Figure 3 As shown in the figure, the overall voxel size of the selected deep saline rock 3D CT scan image is: 400×400×4000, and the physical size is: 8.368×8.368×8.368μm 3 , with a resolution of 20.92nm. It should be noted that the center axis method is an existing technical method. For example, the process of extracting the pore network model using the center axis method can be referred to [Phys.Chem.Earth Part A, 24(7), 593–599]. Of course, the center axis method disclosed in other professional and technical documents can also be applied to this embodiment. The above references are only examples and not limitations. This embodiment does not limit the specific selection of the center axis method.

[0088] The extracted pore network model consists of a series of interconnected pores. The physical size of the pore network model is: 8.368×8.368×8.368μm 3 , the number of pores is 24933. The pore shape is divided by the local void space shape factor G, which is calculated by the following formula:

[0089]

[0090] Where A p is the cross-sectional area of ​​the local void space, Pe is the local void space perimeter. Different pore shapes are divided by the value range of the shape factor G using the following formula:

[0091]

[0092] After the division, the number of irregular triangular pores, square pores, and circular pores in the pore network model are 12393, 8714, and 3826, respectively. For irregular triangular pores, the three internal angles are calculated as follows: Given the three internal angles are β 1 , β 2 and β 3 , and β 1 <β 2 <β 3 , first calculate β 2 The value interval [β 2,min ,β 2,max ]:

[0093]

[0094]

[0095] ② Randomly select β according to the value interval 2 Then, β is calculated by the following formula: 1 :

[0096]

[0097] ③Finally, we get β 3 Values:

[0098]

[0099] S2. Considering the rock fluid forces (van der Waals force, electrostatic force, structural force) and the capillary force of the gas-water interface, a method for analyzing the occurrence of carbon dioxide-formation water under different displacement pressures in pores of different shapes is established;

[0100] Taking irregular triangular pores as an example, please refer to Figure 4 As shown, Figure 4 Indicates the state of gas and water after carbon dioxide intrusion. Carbon dioxide occupies the center of the pore, and the water phase occupies the pore corners and pore wall. The state of water phase corners depends on the wetting angle θ r The half angles β of the three corners of the triangular pore i The size relationship between them is that when θ r <π / 2-β i When θ r ≥π / 2-β iWhen the wetting angle θ is θ, there is no water phase in the corner, and the water phase is stored in the corner in the form of a wall water film. r Given as 20°. For the water phase that satisfies the corner distribution, according to the wetting angle and geometric relationship, we can get:

[0101]

[0102]

[0103]

[0104] In the formula, γ g,w Indicates the air-water interfacial tension, which is given as 0.0575N / m according to laboratory measurement results; R g,w represents the radius of curvature of the air-water interface; P c_(g,w) represents the capillary force at the air-water interface; β i Indicates the corner half angle where the water phase exists (i = 1-n c ),n c Indicates the number of corners where water phase exists; A ci represents the area occupied by the water phase in corner i; b i It represents the extension length of the water phase corner at corner i on the pore wall.

[0105] For the water phase wall water film storage area, the area occupied by the wall water film can be expressed as:

[0106]

[0107] Where h represents the thickness of the water film; the thickness of the water film is affected by the separation pressure Π. The separation pressure consists of three parts and can be expressed as:

[0108] Π d (h) = Π vd (h)+Π el (h)+Π str (h) (11)

[0109] In the formula, Π vd (h),Π el (h),Π str (h) represents van der Waals force, electrostatic force, and structural force respectively. All three forces are functions of the thickness of the water phase. Van der Waals force can be expressed as:

[0110]

[0111] In the formula, A 132 is the non-delayed Hasinuk constant, the subscript represents the interaction between the first phase (solid wall) and the second phase (carbon dioxide) through the third phase (water film), J; A132 It can be expressed as:

[0112]

[0113] Where A 11 , A 22 , A 33 Represent the Hassinook constants of the first phase, second phase, and third phase respectively. The Hassinook constant of the solid wall A 11 Given as 6×10 -20 J. The Hasinuk constants for water film and carbon dioxide are solved using the Lifshitz formula:

[0114]

[0115] In the formula, k B is the Boltzmann constant, T is the temperature, ε i Indicates the dielectric constants of different phases, the dielectric constant of carbon dioxide is given as 1.13, the dielectric constant of water phase is given as 56.07, and the temperature T is given as 373K; n i Represents the refractive index of different phases, the refractive index of carbon dioxide is given as 1.07, and the refractive index of water phase is given as 1.32; ν e Indicates the ultraviolet region electron absorption frequency 3×10 15 s -1 ,h p is Planck's constant 6.62607004×10 -34 , J / s. The electrostatic force is mainly controlled by the internal potential distribution of the water phase. According to the double layer theory, the electrostatic force can be expressed as:

[0116]

[0117] Where Y e is the dimensionless electrostatic potential, n ∞ is the ion concentration, given as 10 mol / m 3 , χ is the reciprocal of the Debye length (double layer attenuation length). Dimensionless electrostatic potential Y e and Debye length χ can be expressed as:

[0118]

[0119]

[0120]

[0121] In the formula, Ψ e represents electrostatic potential; e is the electron charge, dimensionless; z is the ion valence, given as 1; ε 0 represents the dielectric constant of vacuum, 8.854×10 -12F / m; ε 3 The dielectric constant of the water phase is 56.07.

[0122] Structural force Π str (h) can be expressed as:

[0123] Π str (h) = K str exp(-h / λ str ) (19)

[0124] In the formula, K str ,λ str K is a parameter used to describe the magnitude and characteristic length of the structural force. str ,λ str The values ​​are given as 3×10 7 and 8×10 -10 According to formula (10), the change of separation pressure with water phase thickness in formula (11) can be calculated.

[0125] Displacement pressure P g,w The relationship between capillary force and separation pressure can be expressed as:

[0126] P g,w =P c_(g,w) +Π d (h) (20)

[0127] Since the pressure difference of the gas-water interface at each interface point is equal, the value of the separation pressure at the wall (capillary force is 0) is equal to the value of the capillary force at the water phase corner (separation pressure is 0). Therefore, the separation pressure at the wall can be determined by the displacement pressure (Equation (20)), and then the water film thickness can be calculated by the relationship between the separation pressure and the water film thickness in Equation (11). The threshold capillary force at which carbon dioxide begins to invade the irregular pores saturated with the water phase can be expressed as:

[0128]

[0129]

[0130]

[0131] When the displacement pressure P g,w When the capillary force is greater than the threshold value expressed in formula (21), carbon dioxide invades the irregular pores. The carbon dioxide saturation in the irregular pores at different displacement pressures after invasion can be calculated by formula (24):

[0132]

[0133] The numerator of the formula consists of two parts. The first part is the area occupied by the wall water film, and the second part is the area occupied by the water phase corner. The proportion and size of the two parts change with the displacement pressure. The expression of water phase saturation in square pores is the same as formula (24). The carbon dioxide saturation under different displacement pressures in circular pores can be expressed as:

[0134]

[0135] Taking a 10nm equilateral triangle pore as an example, the carbon dioxide saturation in the pore changes with displacement pressure, and the results are compared with the existing method that only considers gas-water capillary forces. Figure 5 As shown, from Figure 5 It can be seen that the existing method ignores the force of rock fluid and will seriously overestimate the amount of carbon dioxide stored in the pores, with an error of more than 5%.

[0136] S3. Based on the capillary force threshold of each pore on the pore network model, the pores that carbon dioxide can invade on the pore network under different displacement pressures are calculated by using invasion percolation;

[0137] In this embodiment, the threshold capillary force of each pore on the pore network model is first calculated (Formula (21)), and the displacement pressure range is set to 0.71MPa to 7.76MPa according to the minimum threshold capillary force and the maximum threshold capillary force on the pore network model. By continuously increasing the displacement pressure at the carbon dioxide injection end, the pores and throats on the pore network model whose threshold capillary force is less than the displacement pressure are found, and the pores connected to the pores at the carbon dioxide injection end and whose threshold capillary force is less than the displacement pressure are searched according to the connectivity diagram principle. These pores are pores that carbon dioxide can invade at each displacement pressure. For the pores where carbon dioxide invades the pore network model at different displacement pressure stages, please refer to Figure 6 shown.

[0138] S4. Based on the single pore gas-water storage analysis method, calculate the carbon dioxide saturation in the pores intruded into the pore network and calculate the carbon dioxide storage potential under the maximum displacement pressure.

[0139] In this embodiment, based on the pores that carbon dioxide can invade on the pore network under different displacement pressures (0.71 MPa to 7.76 MPa) calculated in S3, combined with the single pore carbon dioxide-formation water storage analysis method in S2, the following formula is used to calculate the carbon dioxide saturation on the pore network model after carbon dioxide is injected under different displacement pressures.

[0140]

[0141] Where V pi represents the pore volume of each intruded pore; n 1 Indicates the number of intruded pores; V poreRepresents the total pore volume of the pore network. CO2 saturation S in each intruded pore at different displacement pressures co2_loc (P g,w ) is calculated by equations (24) and (25). At the same time, the results are compared with those of the existing method that only considers the gas-water capillary force. Figure 7 The calculated carbon dioxide saturation changes with displacement pressure on the pore network model. It can be seen that as the displacement pressure increases, the carbon dioxide saturation gradually increases. The carbon dioxide saturation is 0.83 at the maximum displacement pressure of 7.76MPa, which means that 83% of the pore space in the scanned rock sample can be used to store carbon dioxide, and the storage potential is good. At the same time, the existing method that only considers the gas-water capillary force predicts that the carbon dioxide saturation is 0.88 at the maximum displacement pressure of 7.76MPa, which is 5 percentage points overestimated and has a large error.

[0142] The present invention also provides a device for analyzing the potential of carbon dioxide injection storage by considering the force of rock fluids. Figure 8 , which is a structural diagram of the device, the device 800 includes:

[0143] Extraction module 801 is configured to extract a pore network model based on a three-dimensional rock scanning image using a center axis method;

[0144] Establishing module 802, configured to simultaneously consider rock fluid force and gas-water interface capillary force, and establish a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes; the rock fluid force includes van der Waals force, electrostatic force, and structural force;

[0145] The pore calculation module 803 is configured to calculate the pores that carbon dioxide can invade on the pore network under different displacement pressures by using invasion and percolation according to the threshold capillary force of each pore on the pore network model;

[0146] The analysis module 804 is configured to calculate the carbon dioxide saturation in the intruded pores of the pore network according to the single pore gas-water storage analysis method, and analyze the carbon dioxide storage potential under the maximum displacement pressure.

[0147] In some embodiments, the pore network model includes a series of interconnected pores, and the extraction module 801 is further configured as follows: the pore shape is divided by the local void space shape factor G, and the shape factor is calculated by the following formula (1):

[0148]

[0149] Where A p is the cross-sectional area of ​​the local void space, P e is the local void space perimeter;

[0150] Different pore shapes are divided by the value range of the shape factor G using the following formula (2):

[0151]

[0152] Irregular triangular pores are calculated as follows:

[0153] Given three interior angles, β 1 , β 2 and β 3 , and β 1 <β 2 <β 3 , calculate β according to formula (3) and formula (4) 2 The value interval [β 2,min ,β 2,max ]:

[0154]

[0155]

[0156] Randomly select β according to the value interval 2 The value of β is calculated by the following formula (5): 1 The value of:

[0157]

[0158] Based on the determined β 1 and β 2 The value of β is obtained by the following formula (6): 3 The value of:

[0159]

[0160] In some embodiments, the establishing module 802 is further configured to:

[0161] According to the wetting angle θ r The half angles β of the three corners of the triangular pore i The size relationship between them determines whether there is water phase corner in the corner;

[0162] When there is water phase in the corner, according to the wetting angle and geometric relationship, we can get:

[0163]

[0164]

[0165]

[0166] In the formula, γ g,w represents the air-water interfacial tension, Rg,w represents the radius of curvature of the air-water interface; P c_(g,w) represents the capillary force at the air-water interface; β i Indicates the corner half angle where the water phase exists (i = 1-n c ), n c Indicates the number of corners where water phase exists; A ci represents the area occupied by the water phase in corner i; b i It represents the extension length of the water phase corner on the pore wall at corner i;

[0167] When there is no water phase corner in the corner, the water phase exists in the corner in the form of wall water film;

[0168] For the water phase wall water film storage area, the area occupied by the wall water film is expressed as:

[0169]

[0170] Where h represents the thickness of the water film. The thickness of the water film is affected by the separation pressure Π, which is expressed as:

[0171] Π d (h) = Π vd (h)+Π el (h)+Π str (h) (11)

[0172] In the formula, Π vd (h),Π el (h),Π str (h) represents van der Waals force, electrostatic force, and structural force, respectively. All three forces are functions of the thickness of the water phase;

[0173] The van der Waals equation can be expressed as:

[0174]

[0175] In the formula, A 132 is the non-delayed Hasinuk constant, the subscript 132 indicates the interaction between the first phase and the second phase through the third phase; A 132 It is expressed as:

[0176]

[0177] Where A 11 , A 22 , A 33 Respectively represent the Hassinuk constants of the first phase, the second phase, and the third phase, which are solved using the Lifshitz formula:

[0178]

[0179] In the formula, k B is the Boltzmann constant, T is the temperature, ε i Represents the dielectric constant of different phases; n i Represents the refractive index of different phases; ν e Indicates the frequency of electron absorption in the ultraviolet region, h p is Planck's constant;

[0180] The electrostatic force is controlled by the internal potential distribution of the water phase. According to the double layer theory, the electrostatic force is expressed as:

[0181]

[0182] Where Y e is the dimensionless electrostatic potential, n ∞ is the ion concentration, χ is the reciprocal of the Debye length, and the dimensionless electrostatic potential Ye and the Debye length χ are expressed as:

[0183]

[0184]

[0185]

[0186] In the formula, Ψ e represents electrostatic potential; e is the electron charge, dimensionless; z is the ion valence; ε 0 represents the dielectric constant of vacuum; ε 3 represents the dielectric constant of water phase;

[0187] Structural force Π str (h) can be expressed as:

[0188] Π str (h) = K str exp(-h / λ str ) (19)

[0189] In the formula, K str ,λ str It is a parameter used to describe the magnitude and characteristic length of structural forces;

[0190] Displacement pressure P g,w The relationship between capillary force and separation pressure is expressed as:

[0191] P g,w =P c_(g,w) +Π d (h) (20)

[0192] The separation pressure at the wall is determined by the displacement pressure, and the water film thickness is calculated by the relationship between the separation pressure and the water film thickness. The threshold capillary force at which carbon dioxide begins to invade the irregular pores saturated with water is expressed as:

[0193]

[0194]

[0195]

[0196] When the displacement pressure P g,w When the capillary force is greater than the threshold value expressed in formula (21), carbon dioxide invades the irregular pores. After invasion, the carbon dioxide saturation in the irregular pores at different displacement pressures is calculated by formula (24):

[0197]

[0198] The numerator of the formula consists of two parts. The first part is the area occupied by the wall water film, and the second part is the area occupied by the water phase corner. The proportion and size of the two parts change with the displacement pressure. The expression of water phase saturation in square pores is the same as formula (24). The carbon dioxide saturation under different displacement pressures in circular pores is expressed as:

[0199]

[0200] The establishing module 802 is further configured to:

[0201] When θ r <π / 2-β i When , there is a water phase corner in this corner;

[0202] When θ r ≥π / 2-β i When , there is no water phase corner in this corner.

[0203] The pore calculation module 803 is further configured to: calculate the threshold capillary force of each pore on the pore network, compare it with the carbon dioxide displacement pressure, find the pores and throats whose threshold capillary force is less than the displacement pressure, search for pores connected to the pores at the carbon dioxide injection end and whose threshold capillary force is less than the displacement pressure according to the connectivity graph principle, and obtain the pores that carbon dioxide can invade under different displacement pressures.

[0204] The analysis module 804 is further configured to calculate the carbon dioxide saturation on the pore network model after carbon dioxide injection at a given displacement pressure by using the following formula (26):

[0205]

[0206] Where V pi represents the pore volume of each intruded pore; n 1 Indicates the number of intruded pores; V porerepresents the total pore volume of the pore network, S co2_loc (P g,w ) represents the carbon dioxide saturation in each invaded pore at different displacement pressures.

[0207] The modules involved in the embodiments of the present invention may be implemented by software or hardware, and the modules described may also be arranged in a processor. The names of these modules do not, in some cases, limit the modules themselves.

[0208] It should be noted that the device for analyzing the storage potential of carbon dioxide injection considering the force of rock fluid provided in the above embodiment and the method for analyzing the storage potential of carbon dioxide injection considering the force of rock fluid provided in the aforementioned embodiment belong to the same concept, and the specific manner in which each module performs the operation has been described in detail in the method embodiment and will not be repeated here.

[0209] The embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, the analysis method described in each embodiment of the present invention is implemented. The computer-readable storage medium may be included in the electronic device described in the above embodiment, or may exist independently without being assembled into the electronic device.

[0210] In particular, according to an embodiment of the present invention, the various steps and processes described in the above-mentioned method for analyzing the carbon dioxide injection storage potential considering the rock fluid force can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a computer program for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication part, and / or installed from a removable medium. When the computer program is executed by the central processing unit (CPU), various functions defined in the system of the present invention are executed.

[0211] It should be noted that the computer-readable medium shown in the embodiment of the present invention may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, device or device. In the present invention, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, in which a computer-readable computer program is carried. This propagated data signal may take a variety of forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate or transmit a program for use by or in conjunction with an instruction execution system, apparatus or device. A computer program contained on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0212] The embodiment of the present invention also provides a computer system, including a central processing unit (CPU), which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM) or the program loaded from the storage part to the random access memory (RAM), such as executing the carbon dioxide injection storage potential analysis method considering the rock fluid force in the above embodiment. Various programs and data required for system operation are also stored in the RAM. The CPU, ROM and RAM are connected to each other through a bus. The input / output (I / O) interface is also connected to the bus.

[0213] The following components are connected to the I / O interface: an input part including a keyboard, a mouse, etc.; an output part including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker; a storage part including a hard disk, etc.; and a communication part including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication part performs communication processing via a network such as the Internet. A drive is also connected to the I / O interface as needed. Removable media, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., are installed on the drive as needed so that the computer program read therefrom is installed into the storage part as needed.

[0214] In addition, although exemplary embodiments have been described herein, the scope includes any and all embodiments based on the present invention with equivalent elements, modifications, omissions, combinations (e.g., various embodiments intersecting schemes), adaptations or changes. The elements in the claims will be interpreted broadly based on the language adopted in the claims, and are not limited to the examples described in this specification or during the implementation of this application, and the examples will be interpreted as non-exclusive. Therefore, this specification and examples are intended to be considered as examples only, and the true scope and spirit are indicated by the following claims and the full scope of their equivalents.

[0215] The above description is intended to be illustrative rather than restrictive. For example, the above examples (or one or more of them) can be used in combination with each other. For example, those of ordinary skill in the art can use other embodiments when reading the above description. In addition, in the above-mentioned specific embodiments, various features can be grouped together to simplify the present invention. This should not be interpreted as a feature of an invention that is not claimed for protection being necessary for any claim. On the contrary, the subject matter of the present invention may be less than all the features of the embodiments of a specific invention. Thus, the following claims are incorporated into the specific embodiments as examples or embodiments, wherein each claim is independently used as a separate embodiment, and it is considered that these embodiments can be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the full scope of the equivalent forms of the attached claims and these claims.

Claims

1. A method for analyzing the storage potential of carbon dioxide injection considering the forces of rock fluids, It is characterized in that The method comprises: The pore network model is extracted based on the rock 3D scanning image using the center axis method; Considering the rock fluid force and the capillary force of the gas-water interface at the same time, a method for analyzing the occurrence of carbon dioxide-formation water under different displacement pressures in pores of different shapes is established; the rock fluid force includes van der Waals force, electrostatic force, and structural force; According to the capillary force threshold of each pore in the pore network model, the pores that CO2 can invade under different displacement pressures are calculated by using invasion percolation. Based on the single pore gas-water storage analysis method, the carbon dioxide saturation in the intruded pores of the pore network is calculated, and the carbon dioxide storage potential under the maximum displacement pressure is analyzed; The pore network model includes a series of interconnected pores, and the pore shape is divided by the local pore space shape factor G, which is calculated by the following formula (1): Where A p is the local pore space cross-sectional area, P e is the local pore space perimeter; Different pore shapes are divided by the value range of the shape factor G using the following formula (2): Irregular triangular pores are calculated as follows: Given three interior angles, β 1 , β 2 and β 3 , and β 1 <β 2 <β 3 , calculate β according to formula (3) and formula (4) 2 The value interval [β 2,min ,β 2,max ]: Randomly select β according to the value interval 2 The value of β is calculated by the following formula (5): 1 The value of: Based on the determined β 1 and β 2 The value of β is obtained by the following formula (6): 3 The value of:

2. A method for analyzing carbon dioxide injection storage potential taking into account the force of rock fluids according to claim 1, It is characterized in that The method of simultaneously considering the rock fluid force and the capillary force of the gas-water interface and establishing a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes includes: According to the wetting angle θ r The half angles β of the three corners of the triangular pore i The size relationship between them determines whether there is water phase corner in the corner; When there is water phase in the corner, according to the wetting angle and geometric relationship, we can get: In the formula, γ g,w represents the air-water interfacial tension, R g,w represents the radius of curvature of the air-water interface; P c_(g,w) represents the capillary force at the air-water interface; β i Indicates the corner half angle where the water phase exists (i = 1-n c ), n c Indicates the number of corners where water phase exists; A ci represents the area occupied by the water phase in corner i; b i It represents the extension length of the water phase corner on the pore wall at corner i; When there is no water phase corner in the corner, the water phase exists in the corner in the form of wall water film; For the water phase wall water film storage area, the area occupied by the wall water film is expressed as: Where h represents the thickness of the water film. The thickness of the water film is affected by the separation pressure Π, which is expressed as: P d (h)=P vd (h)+P el (h)+P str (h) (11) In the formula, Π vd (h),Π el (h),Π str (h) represents van der Waals force, electrostatic force, and structural force, respectively. All three forces are functions of the thickness of the water phase; The van der Waals force can be expressed as: In the formula, A 132 is the non-delayed Hasinuk constant, the subscript 132 indicates the interaction between the first phase and the second phase through the third phase; A 132 It is expressed as: Where A 11 , A 22 , A 33 Respectively represent the Hassinuk constants of the first phase, the second phase, and the third phase, which are solved using the Lifshitz formula: In the formula, k B is the Boltzmann constant, T is the temperature, ε i represents the dielectric constant of different phases; n i Represents the refractive index of different phases; ν e Indicates the frequency of electron absorption in the ultraviolet region, h p is Planck's constant; The electrostatic force is controlled by the internal potential distribution of the water phase. According to the double layer theory, the electrostatic force is expressed as: Where Y e is the dimensionless electrostatic potential, n ∞ is the ion concentration, χ is the reciprocal of the Debye length, and the dimensionless electrostatic potential Ye and the Debye length χ are expressed as: In the formula, Ψ e represents electrostatic potential; e is the electron charge, dimensionless; z is the ion valence; ε 0 represents the dielectric constant of vacuum; ε 3 represents the dielectric constant of water phase; Structural force Π str (h) can be expressed as: ∏ str (h)=K str exp(-h / λ str ) (19) In the formula, K str ,λ str It is a parameter used to describe the magnitude and characteristic length of structural forces; Displacement pressure P g,w The relationship between capillary force and separation pressure is expressed as: P g,w =P c_(g,w) +Π d (h) (20) The separation pressure at the wall is determined by the displacement pressure, and the water film thickness is calculated by the relationship between the separation pressure and the water film thickness. The threshold capillary force at which carbon dioxide begins to invade the irregular pores saturated with water is expressed as: When the displacement pressure P g,w When the capillary force is greater than the threshold value expressed in formula (21), carbon dioxide invades the irregular pores. After invasion, the carbon dioxide saturation in the irregular pores at different displacement pressures is calculated by formula (24): The numerator of the formula consists of two parts. The first part is the area occupied by the wall water film, and the second part is the area occupied by the water phase corner. The proportion and size of the two parts change with the displacement pressure. The expression of water phase saturation in square pores is the same as formula (24)(24). The carbon dioxide saturation under different displacement pressures in circular pores is expressed as: 。 3. A method for analyzing carbon dioxide injection storage potential taking into account the force of rock fluids according to claim 2, It is characterized in that According to the wetting angle θ r The half angles β of the three corners of the triangular pore i The size relationship between them determines whether there is water phase corner in the corner, including: When θ r <π / 2-β i When , there is a water phase corner in this corner; When θ r ≥π / 2-β i When , there is no water phase corner in this corner.

4. A method for analyzing carbon dioxide injection storage potential taking into account rock fluid forces according to claim 3, It is characterized in that The pores that can be invaded by carbon dioxide on the pore network under different displacement pressures are calculated by using the invasion percolation method according to the threshold capillary force of each pore on the pore network model, including: The threshold capillary force of each pore on the pore network is calculated and compared with the carbon dioxide displacement pressure to find the pores and throats whose threshold capillary force is less than the displacement pressure. According to the connectivity graph principle, pores connected to the pores at the carbon dioxide injection end and whose threshold capillary force is less than the displacement pressure are searched to obtain the pores that carbon dioxide can invade under different displacement pressures.

5. A method for analyzing carbon dioxide injection storage potential taking into account rock fluid forces according to claim 4, It is characterized in that The method of analyzing the occurrence of gas and water in a single pore is used to calculate the carbon dioxide saturation in the intrusion pores of the pore network and analyze the carbon dioxide storage potential under the maximum displacement pressure, including: The carbon dioxide saturation on the pore network model after carbon dioxide injection at a given displacement pressure is calculated by the following formula (26): Where V pi represents the pore volume of each intruded pore; n 1 Indicates the number of intruded pores; V pore represents the total pore volume of the pore network, S co2_loc (P g,w ) represents the carbon dioxide saturation in each invaded pore at different displacement pressures.

6. A device for analyzing carbon dioxide injection storage potential taking into account the force of rock fluids, used to implement the method as claimed in any one of claims 1 to 5, It is characterized in that The device comprises: An extraction module is configured to extract a pore network model based on a three-dimensional rock scanning image using a center axis method; Establishing a module configured to simultaneously consider rock fluid forces and gas-water interface capillary forces, and establishing a carbon dioxide-formation water storage analysis method under different displacement pressures in pores of different shapes; the rock fluid forces include van der Waals forces, electrostatic forces, and structural forces; A pore calculation module is configured to calculate the pores that carbon dioxide can invade on the pore network under different displacement pressures using invasion and percolation according to the threshold capillary force of each pore on the pore network model; The analysis module is configured to calculate the carbon dioxide saturation in the intruded pores of the pore network according to the single pore gas and water storage analysis method, and analyze the carbon dioxide storage potential under the maximum displacement pressure.

7. An electronic device, include: Controller; A memory for storing one or more programs, characterized in that when the one or more programs are executed by the controller, the controller implements the analysis method described in any one of claims 1 to 5.

8. A computer-readable storage medium, It is characterized in that Computer-readable instructions are stored thereon, and when the computer-readable instructions are executed by a processor of a computer, the computer is caused to execute the analysis method according to any one of claims 1 to 5.

9. A computer program product comprising computer instructions stored in a computer readable storage medium, It is characterized in that The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the analysis method according to any one of claims 1 to 5.

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