Method for predicting diffusion coefficient of natural gas in tight sandstone under geological condition
By collecting and processing dense sandstone samples, combining temperature and pressure regulation, a kinetic model is established to predict the natural gas diffusion coefficient in dense sandstone, the problem of differences in calculating natural gas diffusion in dense sandstone in the existing technology is solved, and the calculation accuracy is improved And provide a new method for evaluating diffusion loss.
Patent Information
- Application Number
- CN202411703285.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-26
- Publication Date
- 2025-02-07
AI Technical Summary
The existing technology lacks an effective method to predict the diffusion coefficient of natural gas in dense sandstones under geological conditions, resulting in a large difference in calculating the diffusion of natural gas in dense sandstones.
By collecting dense sandstone samples, using core clamping equipment for clamping and water immersion, the control module regulates the temperature and pressure environment, conducts multiple natural gas injection experiments, establishes a dynamic model of natural gas diffusion coefficient and temperature and pressure, and predicts that different rocks are Diffusion coefficient under different temperature and pressure conditions.
The accurate prediction of the natural gas diffusion coefficient in tight sandstone is achieved, the accuracy of the calculation of natural gas diffusion is improved, and a new way is provided for quantitative evaluation of the degree of natural gas diffusion loss in gas reservoirs.
Smart Images
Figure CN119394854A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of natural gas exploration, and in particular relates to a method for predicting the diffusion coefficient of natural gas in dense sandstone under geological conditions. Background Art
[0002] At present, tight sandstone gas has become a key area of unconventional natural gas exploration in the world. Currently, tight sandstone gas has been discovered or speculated to be developed in more than 70 basins in the world, with a resource volume of about 209.6×10 12 m 3 According to the latest estimates, China’s recoverable tight sandstone gas resources are approximately (9-13)×10 12 m 3 In 2011, the tight sandstone gas production was about 256×10 8 m 3 , accounting for about 25% of the country's total natural gas production.
[0003] Since the reservoir has the characteristics of low porosity, low permeability and strong heterogeneity, natural gas diffusion plays an important role in the formation of tight sandstone gas. Diffusion refers to a physical process in which hydrocarbon gas molecules freely migrate from high concentration areas through various media to low concentration areas to reach equilibrium under the action of concentration gradient. Diffusion is one of the important mechanisms of oil and gas migration. It plays a vital role in the migration, accumulation, accumulation, preservation and destruction of oil and gas, especially natural gas (due to its small molecules, light weight and strong mobility, it has strong diffusivity underground). The natural gas diffusion coefficient can be obtained through theoretical estimation and experimental measurement, but due to the complexity of underground rock porous media, determining the diffusion coefficient of natural gas in rocks is the fundamental way to study the diffusion of underground natural gas. However, there is still no effective method to predict the diffusion coefficient of natural gas in tight sandstone under geological conditions, which leads to great differences in the calculated diffusion amount of natural gas in tight sandstone.
[0004] Through the above analysis, the problems and defects of the existing technology are: there is currently a lack of effective methods to predict the diffusion coefficient of natural gas in tight sandstone under geological conditions, and there are great differences in the diffusion amount of natural gas in tight sandstone calculated by the existing technology. Summary of the invention
[0005] In view of the problems existing in the prior art, the present invention provides a method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions.
[0006] The present invention is implemented as follows: a method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions, the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions comprises the following steps: Step 1: Collect a dense sandstone sample, clamp the dense sandstone sample with a core clamping device, evacuate the sample, and soak it in saturated water until no bubbles overflow; Step 2: Controlling the natural gas injection module through the control module to inject natural gas into the dense sandstone sample to displace water in the dense sandstone sample; Step 3: Control the temperature regulating module and the pressure regulating module through the control module to change the temperature environment and pressure environment of the dense sandstone sample, and repeat step 1 and step 2 under different temperature and pressure combinations; the changing of the temperature environment and pressure environment of the dense sandstone sample includes: Determine the temperature and pressure range required for the experiment based on the location of the dense sandstone sample collected; The determined temperature range is corrected by the temperature improvement factor: T 上修 =T 上限 +S; T 下修 =T 下限 -S; Among them, T 上修 Indicates the upper limit correction value of the determined temperature range; T 上限 It indicates the upper limit of the originally determined temperature range; S indicates the temperature improvement coefficient; T 下修 Indicates the lower limit correction value of the determined temperature range; T 下限 Indicates the lower limit of the originally determined temperature range; The pressure is set to multiple sets of values under fixed temperature conditions, and natural gas is injected into the dense sandstone sample; the temperature is set to multiple sets of values under fixed pressure, and natural gas is injected into the dense sandstone sample; Step 4: Establish a temperature kinetic model and a pressure exponential model for the natural gas diffusion coefficient, temperature, and pressure, respectively, and determine the ratio of the diffusion activation energy to the gas constant and the diffusion pressure factor; Step 5: Establish a multi-factor model of diffusion coefficient. Use the multi-factor model to predict the diffusion coefficients of different rocks in the region under different temperature and pressure conditions, including: Based on the diffusion coefficient multi-factor model combined with Fick's first law, the estimation formula of natural gas diffusion loss in gas reservoirs is obtained to calculate the natural gas diffusion loss; The natural gas diffusion loss amount is divided by the natural gas diffusion area to obtain the natural gas diffusion loss intensity; The natural gas diffusion loss rate is obtained by dividing the natural gas diffusion loss intensity by the diffusion intensity per unit area; Wherein, the diffusion coefficient multi-factor model is: D = ln(ΔC 0 / ΔC i ) / [E(ti -t 0 )]; Where, E = A(1 / V) / L, t 0 is the initial time, t i is the moment I, ΔC i is the concentration difference of natural gas in the experimental box at time i, ΔC 0 is the concentration difference of natural gas in the experimental box at the initial moment, A is the cross-sectional area of the rock sample, L is the length of the rock sample, and V is the volume of the experimental box.
[0007] Further, collecting the dense sandstone sample in step 1 includes: The dense sandstone samples were collected based on the principle that the porosity, permeability, pore throat median radius and clay mineral content of the dense sandstone samples are distributed from low to high.
[0008] Furthermore, after collecting the dense sandstone sample in step 1, the step further includes saturating the collected dense sandstone sample with formation water; saturating the collected dense sandstone sample with formation water includes: The collected dense sandstone samples were saturated with formation water according to the regional formation water salinity values.
[0009] Furthermore, the core clamping device in step one is located in a closed experimental box, and a vacuum module is connected to the outside of the experimental box.
[0010] Furthermore, the gas injection equilibrium pressure of the natural gas injection module in step 2 into the tight sandstone sample is 3 MPa; and the constant boost flow rate during gas injection is 5 mL / min.
[0011] Further, the injecting of natural gas into the tight sandstone sample in step three includes: After placing the dense sandstone sample in the sample chamber, vacuum treatment is performed to make the pressure in the inert gas chamber and the sample chamber 0; Injecting nitrogen into the inert gas chamber until the pressure in the inert gas chamber is stable; opening the valve connecting the inert gas chamber and the sample chamber to balance the pressure in the inert gas chamber and the sample chamber; Inject natural gas into the inert gas chamber and the sample chamber until the temperature or pressure in the sample chamber reaches the set value.
[0012] Furthermore, the pressure index model in step 4 is: ; in, ESI is the pressure index, W k and C k are the indicator weights and indicator values of the pressure evaluation system, nis the number of pressure indicators.
[0013] Another object of the present invention is to provide a computer program product stored on a computer-readable medium, including a computer-readable program, which, when executed on an electronic device, provides a user input interface to apply the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions.
[0014] Another object of the present invention is to provide a computer-readable storage medium storing instructions, which, when executed on a computer, enable the computer to apply the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions.
[0015] Another object of the present invention is to provide an information data processing terminal, which is used to implement the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions.
[0016] Combined with all the above technical solutions, the advantages and positive effects of the present invention are as follows: the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions provided by the present invention controls the temperature adjustment module and the pressure adjustment module to change the temperature environment and pressure environment of the rock sample through the control module, and performs multiple natural gas injection experiments under different temperature and pressure combinations, thereby realizing the prediction of the natural gas diffusion coefficient of different rocks in a region in different historical periods, providing necessary parameters for calculating the natural gas diffusion amount in historical periods, and improving the calculation accuracy of the natural gas diffusion amount. At the same time, the present invention uses the natural gas diffusion loss rate to quantitatively evaluate the degree of natural gas diffusion loss in gas reservoirs, providing a new way to quantitatively evaluate the degree of natural gas diffusion loss in gas reservoirs, and providing a new method for evaluating the quality of gas reservoir preservation conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0018] Figure 1 It is a flow chart of a method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions provided by an embodiment of the present invention.
[0019] Figure 2 It is a flow chart of a method for collecting dense sandstone samples provided by an embodiment of the present invention.
[0020] Figure 3 It is a flow chart of a method for changing the temperature environment and pressure environment of a rock sample provided by an embodiment of the present invention.
[0021] Figure 4 It is a flow chart of a method for predicting the diffusion coefficients of different rocks in a region under different temperature and pressure conditions provided by an embodiment of the present invention.
[0022] Figure 5 It is a flow chart of a method for injecting natural gas into a rock sample provided by an embodiment of the present invention. DETAILED DESCRIPTION
[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0024] In view of the problems existing in the prior art, the present invention provides a method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions. The present invention is described in detail below in conjunction with the accompanying drawings.
[0025] like Figure 1 As shown, the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions provided by the embodiment of the present invention comprises the following steps: S101, collecting a dense sandstone sample, clamping the dense sandstone sample with a core clamping device, and immersing the sample in saturated water after vacuuming until no bubbles overflow; S102, controlling the natural gas injection module through the control module to inject natural gas into the tight sandstone sample to displace water in the tight sandstone sample; S103, controlling the temperature regulating module and the pressure regulating module through the control module to change the temperature environment and the pressure environment of the dense sandstone sample, and repeating steps S101 and S102 under different temperature and pressure combinations; S104, respectively establishing a temperature kinetic model and a pressure exponential model of natural gas diffusion coefficient, temperature, and pressure, and determining a ratio of diffusion activation energy to a gas constant and a diffusion pressure factor; S105, establishing a multi-factor model of diffusion coefficient, and using the multi-factor model of diffusion coefficient to predict the diffusion coefficients of different rocks in the region under different temperature and pressure conditions.
[0026] like Figure 2 As shown, the collection of dense sandstone samples provided in the embodiment of the present invention includes: S201, collecting dense sandstone samples according to the principle that the porosity, permeability, pore throat median radius and clay mineral content of dense sandstone samples are distributed from low to high; S202, after collecting the dense sandstone sample, saturate the collected dense sandstone sample with formation water according to the regional formation water mineralization value; S203, clamp the dense sandstone sample using a core clamping device, evacuate the sample, and then soak it in saturated water until no bubbles overflow.
[0027] The core clamping device provided in the embodiment of the present invention is located in a closed experimental box, and a vacuum module is connected to the outside of the experimental box.
[0028] The gas injection equilibrium pressure of the natural gas injection module provided in the embodiment of the present invention into the rock sample is 3 MPa; the constant boost flow rate during gas injection is 5 mL / min.
[0029] The multi-factor model of diffusion coefficient in the embodiment of the present invention is: D = ln(ΔC 0 / ΔC i ) / [E(t i -t 0 )]; Where, E = A(1 / V) / L, t 0 is the initial time, t i is the moment I, ΔC i is the concentration difference of natural gas in the experimental box at time i, ΔC 0 is the concentration difference of natural gas in the experimental box at the initial moment, A is the cross-sectional area of the rock sample, L is the length of the rock sample, and V is the volume of the experimental box.
[0030] like Figure 3 As shown, the method for changing the temperature environment and pressure environment of a rock sample provided by an embodiment of the present invention includes: S301, determining the temperature and pressure range required for the experiment according to the regional location of the collected dense sandstone sample; S302, correcting the determined temperature range by using a temperature improvement coefficient; setting multiple sets of values for the pressure under a fixed temperature condition, and injecting natural gas into the tight sandstone sample; S303, setting multiple sets of values for the temperature under a fixed pressure, and injecting natural gas into the tight sandstone sample.
[0031] The method of correcting a determined temperature range by using a temperature improvement coefficient provided in an embodiment of the present invention includes: T 上修 =T 上限 +S; T 下修 =T 下限 -S; Among them, T 上修 Indicates the upper limit correction value of the determined temperature range; T 上限 It indicates the upper limit of the originally determined temperature range; S indicates the temperature improvement coefficient; T 下修 Indicates the lower limit correction value of the determined temperature range; T下限 Indicates the lower limit of the originally determined temperature range.
[0032] like Figure 4 As shown, the diffusion coefficients of different rocks in the region predicted under different temperature and pressure conditions provided by the embodiment of the present invention include: S401, according to the diffusion coefficient multi-factor model combined with Fick's first law, the natural gas diffusion loss estimation formula of the gas reservoir is obtained to calculate the natural gas diffusion loss; S402, dividing the natural gas diffusion loss amount by the natural gas diffusion area to obtain the natural gas diffusion loss intensity; S403, the natural gas diffusion loss rate is obtained by dividing the natural gas diffusion loss intensity by the diffusion intensity per unit area.
[0033] like Figure 5 As shown, the injecting of natural gas into a rock sample provided by an embodiment of the present invention includes: S501, after placing the rock sample in the sample chamber, perform vacuum treatment to make the pressure in the inert gas chamber and the sample chamber zero; S502, injecting nitrogen into the inert gas chamber until the pressure in the inert gas chamber is stable; opening a valve connecting the inert gas chamber and the sample chamber to balance the pressure in the inert gas chamber and the sample chamber; S503, injecting natural gas into the inert gas chamber and the sample chamber until the temperature or pressure in the sample chamber reaches a set value.
[0034] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.
[0035] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When the use is implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.) mode) to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state hard disk SolidState Disk (SSD)), etc.
[0036] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.
Claims
1. A method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions, characterized in that: The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions comprises the following steps: Step 1: Collect a dense sandstone sample, clamp the dense sandstone sample with a core clamping device, evacuate the sample, and soak it in saturated water until no bubbles overflow; Step 2: Controlling the natural gas injection module through the control module to inject natural gas into the dense sandstone sample to displace water in the dense sandstone sample; Step 3: Control the temperature regulating module and the pressure regulating module through the control module to change the temperature environment and pressure environment of the dense sandstone sample, and repeat step 1 and step 2 under different temperature and pressure combinations; the changing of the temperature environment and pressure environment of the dense sandstone sample includes: Determine the temperature and pressure range required for the experiment based on the location of the dense sandstone sample collected; The determined temperature range is corrected by the temperature improvement factor: T 上修 =T 上限 +S; T 下修 =T 下限 -S; Among them, T 上修 Indicates the upper limit correction value of the determined temperature range; T 上限 It indicates the upper limit of the originally determined temperature range; S indicates the temperature improvement coefficient; T 下修 Indicates the lower limit correction value of the determined temperature range; T 下限 Indicates the lower limit of the originally determined temperature range; The pressure is set to multiple sets of values under fixed temperature conditions, and natural gas is injected into the dense sandstone sample; the temperature is set to multiple sets of values under fixed pressure, and natural gas is injected into the dense sandstone sample; Step 4: Establish a temperature kinetic model and a pressure exponential model for the natural gas diffusion coefficient, temperature, and pressure, respectively, and determine the ratio of the diffusion activation energy to the gas constant and the diffusion pressure factor; Step 5: Establish a multi-factor model of diffusion coefficient. Use the multi-factor model to predict the diffusion coefficients of different rocks in the region under different temperature and pressure conditions, including: Based on the diffusion coefficient multi-factor model combined with Fick's first law, the estimation formula of natural gas diffusion loss in gas reservoirs is obtained to calculate the natural gas diffusion loss; The natural gas diffusion loss amount is divided by the natural gas diffusion area to obtain the natural gas diffusion loss intensity; The natural gas diffusion loss rate is obtained by dividing the natural gas diffusion loss intensity by the diffusion intensity per unit area; Wherein, the diffusion coefficient multi-factor model is: D=ln(ΔC0 / ΔC i ) / [E(t i -t0)]; Where E = A(1 / V) / L, t0 is the initial time, t i is the moment I, ΔC i is the concentration difference of natural gas in the experimental box at time i, ΔC0 is the concentration difference of natural gas in the experimental box at the initial moment, A is the cross-sectional area of the rock sample, L is the length of the rock sample, and V is the volume of the experimental box.
2. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: The step 1 of collecting dense sandstone samples comprises: The dense sandstone samples were collected based on the principle that the porosity, permeability, pore throat median radius and clay mineral content of the dense sandstone samples are distributed from low to high.
3. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: After the dense sandstone sample is collected in step 1, the step further includes saturating the collected dense sandstone sample with formation water; the step of saturating the collected dense sandstone sample with formation water includes: The collected dense sandstone samples were saturated with formation water according to the regional formation water salinity values.
4. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: The core clamping device in step 1 is located in a closed experimental box, and a vacuum module is connected to the outside of the experimental box.
5. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: The gas injection equilibrium pressure of the natural gas injection module into the tight sandstone sample in step 2 is 3 MPa; the constant boost flow rate during gas injection is 5 mL / min.
6. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: The step 3 of injecting natural gas into the tight sandstone sample comprises: After placing the dense sandstone sample in the sample chamber, vacuum treatment is performed to make the pressure in the inert gas chamber and the sample chamber 0; Injecting nitrogen into the inert gas chamber until the pressure in the inert gas chamber is stable; opening the valve connecting the inert gas chamber and the sample chamber to balance the pressure in the inert gas chamber and the sample chamber; Inject natural gas into the inert gas chamber and the sample chamber until the temperature or pressure in the sample chamber reaches the set value.
7. The method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions according to claim 1, characterized in that: The pressure index model in step 4 is: ； in, ESI is the pressure index, W k and C k are the indicator weights and indicator values of the pressure evaluation system, n is the number of pressure indicators.
8. A computer program product stored on a computer-readable medium, comprising a computer-readable program, which, when executed on an electronic device, provides a user input interface for applying the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions as described in any one of claims 1 to 7.
9. A computer-readable storage medium storing instructions, which, when executed on a computer, causes the computer to apply the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions as claimed in any one of claims 1 to 7.
10. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the method for predicting the diffusion coefficient of natural gas in tight sandstone under geological conditions as described in any one of claims 1 to 7.