Method and system for determining burial potential of carbon dioxide structure of saline water layer

Abstract

The invention provides a saline water layer carbon dioxide structure burying potential determination method and system. The determination method comprises the steps that S1, the effective capillary radius considering the slippage effect and the bound water film thickness is calculated; s2, calculating salt water layer parameters according to the effective capillary radius; and S3, calculating the carbon dioxide structure burying amount of the saline water layer according to the parameters of the saline water layer. By considering the breakthrough pressure and the comprehensive compression coefficient of the salt water layer cover layer and combining the density of carbon dioxide under different temperature and pressure conditions, the accurate calculation of the carbon dioxide structure burying amount of the salt water layer is realized under the condition that the cover layer leakage does not occur.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide storage, and particularly to a method and system for determining the structural storage potential of carbon dioxide in a saline aquifer. Background Art

[0002] Carbon dioxide storage is to store carbon dioxide underground through technical means to prevent it from being emitted into the atmosphere, and it is considered to be one of the important means to reduce the content of greenhouse gases and alleviate the greenhouse effect at present. The conventional carbon dioxide storage sites include deep saline aquifers, abandoned oil and gas fields, and deep coal seams. Deep saline aquifers have the characteristics of wide coverage area and large burial potential. In structural storage, carbon dioxide is injected into a deep saline reservoir, and the pores trap carbon dioxide, resulting in an increase in pore pressure. The carbon dioxide existing in the pores in a free state is transported to the top of the reservoir under the action of buoyancy, and the low-permeability caprock above the reservoir plays a role in blocking carbon dioxide. Therefore, in the process of carbon dioxide storage in a saline aquifer, there is an urgent need for a method for determining the structural storage potential of carbon dioxide in a saline aquifer to accurately calculate the structural storage volume of carbon dioxide in a saline aquifer under the condition of ensuring no leakage from the caprock.

[0003] There are problems in existing methods, such as the inability to accurately calculate the volume of the gas phase region, the failure to consider the breakthrough pressure of the caprock, and the failure to consider the influence of reservoir conditions. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a method and system for determining the structural storage potential of carbon dioxide in a saline aquifer that overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of the present invention, there is provided a method for determining the structural storage potential of carbon dioxide in a saline aquifer, and the determination method includes:

[0006] Step S1, calculating an effective capillary radius considering the slip effect and the thickness of the bound water film;

[0007] Step S2, calculating saline aquifer parameters according to the effective capillary radius;

[0008] Step S3, calculating the structural storage volume of carbon dioxide in the saline aquifer according to the saline aquifer parameters.

[0009] Optionally, the step S2 of calculating the saline aquifer parameters according to the effective capillary radius specifically includes:

[0010] Calculating the capillary breakthrough pressure according to the effective capillary radius;

[0011] Calculating the density of carbon dioxide;

[0012] Calculating the comprehensive compressibility.

[0013] Optionally, the formula for calculating the effective capillary radius considering the slip effect and the thickness of the bound water film in step S1 is as follows:

[0014]

[0015] In the formula, R e is the effective capillary radius, in m; R is the capillary radius, in m; ε is the ratio of the thickness of the bound water film to the pore radius, a constant; k is the caprock permeability, in m 2 ; φ a is the caprock porosity; λ is the slip length of carbon dioxide, in m.

[0016] Optionally, the expression form of the slip length λ of the carbon dioxide is shown in Equation (2):

[0017]

[0018] In the formula, μ 1 is the fluid viscosity without pore wall effect, in Pa·s; σ is the interfacial tension, in N·m -1 ; θ is the wetting angle of water on the tube wall; D s is the surface diffusion coefficient, in m 2 ·s -1 .

[0019] Optionally, the expression of the surface diffusion coefficient D s is shown in Equation (3):

[0020]

[0021] In the formula, D s0 is the reference value of the surface diffusion coefficient at T 0 = 293.15 K and P 0 = 1.013×10 5 Pa, which is 1.47×10 -5 m 2 ·s -1 ; T i is the formation temperature, in K; P i is the formation pressure, in MPa.

[0022] Optionally, the formula for calculating the capillary breakthrough pressure based on the effective capillary radius is as follows:

[0023]

[0024] In the formula, P is the capillary breakthrough pressure, in MPa.

[0025] Optionally, the formula for calculating the density of carbon dioxide is as follows:

[0026]

[0027] In the formula, is the density of carbon dioxide, g / cm 3 ; M is the molar molecular mass of carbon dioxide, 44 g / mol; is the pressure of carbon dioxide, MPa; R is the universal gas constant, 8.314 J·mol -1 ·K -1 ; is the temperature of carbon dioxide, K; Z is the compressibility factor of carbon dioxide.

[0028] Optionally, the formula for calculating the comprehensive compressibility factor is:

[0029] C = C f + φS w C w (6)

[0030] In the formula, C is the comprehensive compressibility factor, MPa -1 ; C f is the compressibility factor of the rock, MPa -1 ; C w is the compressibility factor of water, MPa -1 ; S w is the water saturation; φ is the porosity of the saline aquifer.

[0031] Optionally, the formula for calculating the structural storage amount of carbon dioxide in the saline aquifer in step S3 according to the saline aquifer parameters is:

[0032]

[0033] In the formula, Structure is the structural storage amount of carbon dioxide, kg; A is the area of the saline aquifer, m 2 ; h is the thickness of the saline aquifer, m; P a is the maximum allowable formation pressure, MPa; P 0 is the initial formation pressure, MPa; P is the capillary breakthrough pressure, MPa; S gt is the residual gas saturation.

[0034] On the other hand, the present invention also provides a system for determining the structural storage potential of carbon dioxide in a saline aquifer, applying the method for determining the structural storage potential of carbon dioxide in a saline aquifer according to any one of the above, and the determination system includes:

[0035] An effective capillary radius calculation module, configured to calculate an effective capillary radius considering the slip effect and the thickness of the bound water film;

[0036] A capillary breakthrough pressure calculation module for calculating the capillary breakthrough pressure according to the effective capillary radius;

[0037] A carbon dioxide density calculation module for calculating the density of carbon dioxide;

[0038] A comprehensive compressibility calculation module for calculating the comprehensive compressibility;

[0039] A carbon dioxide structural storage capacity calculation module for calculating the carbon dioxide structural storage capacity in the saline aquifer according to the capillary breakthrough pressure, the density of carbon dioxide, and the comprehensive compressibility.

[0040] A method and system for determining the carbon dioxide structural storage potential in a saline aquifer provided by the present invention. The determination method includes: Step S1, calculating the effective capillary radius considering the slip effect and the thickness of the bound water film; Step S2, calculating the saline aquifer parameters according to the effective capillary radius; Step S3, calculating the carbon dioxide structural storage capacity in the saline aquifer according to the saline aquifer parameters. By considering the breakthrough pressure and the comprehensive compressibility of the caprock in the saline aquifer, and combining the density of carbon dioxide under different temperature and pressure conditions, an accurate calculation of the carbon dioxide structural storage capacity in the saline aquifer can be achieved while ensuring no caprock leakage.

[0041] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are specifically exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is a flowchart of a method for determining the carbon dioxide structural storage potential in a saline aquifer provided by an embodiment of the present invention;

[0044] Figure 2 It is a graph showing the change of the capillary breakthrough pressure with the initial formation pressure provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0046] The terms "comprising" and "having" and any variations thereof in the description, claims, and drawings of the present invention are intended to cover non-exclusive inclusion. For example, a series of steps or units are included.

[0047] The technical solution of the present invention will be further described in detail below in conjunction with the drawings and embodiments.

[0048] As Figure 1 and Figure 2 shown, the present invention provides a method for determining the sequestration potential of a carbon dioxide structure in a saline aquifer, and the calculation steps are as follows:

[0049] S1. Calculate the effective capillary radius considering the slip effect and the thickness of the bound water film;

[0050] In step S1, the formula for the effective capillary radius considering the slip effect and the thickness of the bound water film is:

[0051]

[0052] In the formula, R e is the effective capillary radius, m; R is the capillary radius, m; ε is the ratio of the thickness of the bound water film to the pore radius, a constant; k is the permeability of the caprock, m 2 ; φ a is the porosity of the caprock; λ is the slip length of carbon dioxide, m, and the expression form of λ is as shown in formula (2):

[0053]

[0054] In the formula, μ 1 is the fluid viscosity without pore wall effect, Pa·s; σ is the interfacial tension, N·m -1 ; θ is the wetting angle of water on the pipe wall; D s is the surface diffusion coefficient, m 2 ·s -1 .

[0055] Among them, the surface diffusion coefficient D s can be calculated by formula (3):

[0056]

[0057] In the formula, Ds0 For T 0 = 293.15 K and P 0 = 1.013×10 5 Pa, the reference value of the surface diffusion coefficient is 1.47×10 -5 m 2 ·s -1 ; T i is the formation temperature, K; P i is the formation pressure, MPa.

[0058] S2. Calculate the capillary breakthrough pressure according to the capillary radius;

[0059] The formula for calculating the capillary breakthrough pressure in the step S2 is:

[0060]

[0061] In the formula, P is the capillary breakthrough pressure, MPa.

[0062] S3. Calculate the density of carbon dioxide;

[0063] The formula for calculating the density of carbon dioxide in the step S3 is:

[0064]

[0065] In the formula, is the density of carbon dioxide, g / cm 3 ; M is the molar molecular mass of carbon dioxide, 44 g / mol; is the pressure of carbon dioxide, MPa; R is the universal gas constant, 8.314 J·mol -1 ·K -1 ; is the temperature of carbon dioxide, K; Z is the compressibility factor of carbon dioxide.

[0066] S4. Calculate the comprehensive compressibility;

[0067] The formula for calculating the comprehensive compressibility C in the step S4 is:

[0068] C = C f + φS w C w (6)

[0069] In the formula, C f is the compressibility of the rock, MPa -1 ; C w is the compressibility of water, Mpa -1 ; S w is the water saturation; φ is the porosity of the saline aquifer.

[0070] S5. Calculate the buried amount of carbon dioxide in the saline aquifer according to the capillary breakthrough pressure, the density of carbon dioxide, and the comprehensive compressibility factor.

[0071] The formula for calculating the buried amount of carbon dioxide in the saline aquifer in step S5 is as follows:

[0072]

[0073] In the formula, M 二氧化碳 The structure is the buried amount of carbon dioxide in the structure, kg; A is the area of the saline aquifer, m 2 ; h is the thickness of the saline aquifer, m; P a is the maximum allowable formation pressure, MPa; P 0 is the initial formation pressure, MPa; P is the capillary breakthrough pressure, MPa; S gt is the residual gas saturation; is the density of carbon dioxide, kg / m 3 ; C is the comprehensive compressibility factor, MPa -1 .

[0074] This embodiment is illustrated by taking a certain saline aquifer as an example:

[0075] S1. Calculate the effective capillary radius considering the slip effect and the thickness of the bound water film. According to the relevant parameters in Table 1, the slip length λ is calculated to be 9.55×10 -6 m, and the effective capillary radius can be obtained by the following formula:

[0076]

[0077] Table 1

[0078]

[0079]

[0080] S2. Calculate the capillary breakthrough pressure P based on the effective capillary radius obtained in step S1:

[0081]

[0082] S3. Calculate the density of carbon dioxide. According to the relevant parameters in Table 2, the density of carbon dioxide can be obtained by the following formula:

[0083]

[0084] Table 2

[0085]

[0086] S4. Calculate the comprehensive compressibility coefficient. According to the relevant parameters in Table 3, calculate the comprehensive compressibility coefficient C through the following formula: C = C f + φS w C w = 0.00165.

[0087] Table 3

[0088]

[0089]

[0090] S5. Calculate the structural storage volume of carbon dioxide based on the capillary breakthrough pressure, the density of carbon dioxide, and the comprehensive compressibility coefficient. Substitute the capillary breakthrough pressure p calculated in step S2, the density of carbon dioxide ρ calculated in step S3, and the comprehensive compressibility coefficient calculated in step S4 into step S5 to calculate the structural storage volume of carbon dioxide:

[0091]

[0092] Table 4

[0093] Area A of the brine layer <![CDATA[12km 2 > Thickness h of the brine layer 200m <![CDATA[Irreducible gas saturation S gt > 0.2

[0094] Beneficial effects: The structural storage of carbon dioxide in the saline aquifer is an unsafe storage method. Due to factors such as the density difference between carbon dioxide and brine and reservoir heterogeneity, carbon dioxide will diffuse to the lower part of the caprock under the action of buoyancy, and this migration increases the risk of carbon dioxide storage leakage. The present invention proposes a method for determining the potential of carbon dioxide structural storage in the saline aquifer. By considering the breakthrough pressure and comprehensive compressibility coefficient of the caprock in the saline aquifer and combining the density of carbon dioxide under different temperature and pressure conditions, it realizes the accurate calculation of the structural storage volume of carbon dioxide in the saline aquifer while ensuring no caprock leakage.

[0095] The above specific embodiments further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining the structural storage potential of carbon dioxide in a brine layer, characterized in that, the determination method includes: Step S1: Calculate the effective capillary radius considering the slip effect and the thickness of the bound water film; Step S2: Calculate the brine layer parameters according to the effective capillary radius; Step S3: Calculate the structural storage amount of carbon dioxide in the brine layer according to the brine layer parameters.

2. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 1, characterized in that, the specific steps of Step S2, calculating the brine layer parameters according to the effective capillary radius, include: Calculating the capillary breakthrough pressure according to the effective capillary radius; Calculating the density of carbon dioxide; Calculating the comprehensive compressibility.

3. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 1, characterized in that, the formula for Step S1, calculating the effective capillary radius considering the slip effect and the thickness of the bound water film, is: where R e is the effective capillary radius, m; R is the capillary radius, m; ε is the ratio of the thickness of the bound water film to the pore radius, a constant; k is the caprock permeability, m 2 ; φ a is the caprock porosity; λ is the slip length of carbon dioxide, m.

4. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 3, characterized in that, the expression form of the slip length λ of the carbon dioxide is shown in formula (2): where μ 1 is the fluid viscosity without the wall effect of pores, Pa·s; σ is the interfacial tension, N·m -1 ; θ is the wetting angle of water on the tube wall; D s is the surface diffusion coefficient, m 2 ·s -1 .

5. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 4, characterized in that, The surface diffusion coefficient D s is expressed as shown in Equation (3): where D s0 is for T 0 = 293.15 K and P 0 = 1.013 × 10 5 Pa, the reference value of the surface diffusion coefficient is 1.47 × 10 - 5 m 2 ·s -1 ; T i is the formation temperature, K; P i is the formation pressure, MPa.

6. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 2, characterized in that, the formula for calculating the capillary breakthrough pressure according to the effective capillary radius is: In the formula, P is the capillary breakthrough pressure, MPa.

7. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 2, characterized in that, the formula for calculating the density of carbon dioxide is: In the formula, is the density of carbon dioxide, g / cm 3 ; M is the molar molecular mass of carbon dioxide, 44 g / mol; is the pressure of carbon dioxide, MPa; R is the universal gas constant, 8.314 J·mol -1 ·K -1 ; is the temperature of carbon dioxide, K; Z is the compressibility factor of carbon dioxide.

8. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 2, characterized in that, the formula for calculating the comprehensive compressibility is: C=C f +φS w C w (6) where C is the comprehensive compressibility coefficient, MPa -1 ; C f is the compressibility coefficient of the rock, MPa -1 ; C w is the compressibility coefficient of water, MPa -1 ; S w is the water saturation; φ is the porosity of the saline aquifer.

9. The method for determining the structural storage potential of carbon dioxide in a brine layer according to claim 1, characterized in that, the calculation formula for Step S3, calculating the structural storage amount of carbon dioxide in the brine layer according to the brine layer parameters, is: In the formula, is configured as the carbon dioxide structural burial amount, kg; A is the area of the saline aquifer, m 2 ; h is the thickness of the saline aquifer, m; P a is the maximum allowable formation pressure, MPa; P 0 is the initial formation pressure, MPa; P is the capillary breakthrough pressure, MPa; S gt is the residual gas saturation.

10. A system for determining the structural storage potential of carbon dioxide in a brine layer, applying the method for determining the structural storage potential of carbon dioxide in a brine layer according to any one of claims 1-9, characterized in that, the determination system includes: An effective capillary radius calculation module, used to calculate the effective capillary radius considering the slip effect and the thickness of the bound water film; A capillary breakthrough pressure calculation module, used to calculate the capillary breakthrough pressure according to the effective capillary radius; A density calculation module of carbon dioxide, used to calculate the density of carbon dioxide; A comprehensive compressibility calculation module, used to calculate the comprehensive compressibility; A carbon dioxide structural storage amount calculation module, used to calculate the structural storage amount of carbon dioxide in the brine layer according to the capillary breakthrough pressure, the density of carbon dioxide and the comprehensive compressibility.

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