Method for analyzing diagenesis of clay minerals by combining physical simulation and numerical simulation

Abstract

The invention discloses a method for analyzing diagenesis of clay minerals by combining physical simulation and numerical simulation, which comprises the following steps: selecting clay single minerals, and preparing a formation water solution; respectively filling the clay single mineral and the stratum water solution into a plurality of reaction kettles, and carrying out diagenesis physical simulation; establishing a numerical simulation model with the same physical simulation experiment condition, and outputting mineral and ion data; according to mineral and ion data, fitting a physical simulation experiment result and a numerical simulation result, and determining a mineral corrosion rate; and establishing a geologic model by taking the mineral dissolution rate as a reference, and performing clay single mineral diagenesis simulation within a geological time scale. According to the method, numerical simulation parameters are constrained by physical simulation experiment results, and comparison and verification of numerical simulation and physical simulation results are realized by adjusting mineral corrosion kinetic parameters in real time, so that the numerical simulation experiment results are close to actual conditions.

Description

Technical Field

[0001] This invention relates to the field of quantitative research on diagenesis of organic-rich rocks, specifically to a method for analyzing the diagenesis of clay minerals by combining physical and numerical simulations. Background Technology

[0002] my country's continental organic-rich clay shale is currently a key target for exploration of medium-to-high maturity shale oil. Continental clay-rich shale, with an average clay mineral content exceeding 40%, is a crucial factor controlling shale oil reservoir space. The composition, content, and morphology of clay minerals in the rocks exhibit regular changes at different stages of diagenesis, which are significant for the reservoir properties, compressibility, and recoverability of shale. Currently, most studies on the diagenesis of different clay minerals focus on physical simulations in the laboratory. Whether it's conventional mechanical compaction experiments that can be subjected to temperature loading, or fluid-solid coupling experiments that can achieve temperature-fluid-pressure conditions, these studies can only realize shale reservoir properties and mineral dissolution and precipitation at the laboratory scale (days to years), and cannot reproduce the rock-mineral-pore evolution process at the geological scale (millions of years). Even with the later emergence of different types of diagenetic numerical simulation software, only quantitative simulations of diagenesis at the geological scale have been achieved; the simulation results cannot be verified, and it is impossible to determine whether the fluid-solid interaction process in the simulation is correct. Therefore, there is an urgent need for a method to accurately quantify the diagenesis and borehole formation of organic clay shale reservoirs at the geological scale. Summary of the Invention

[0003] The purpose of this invention is to provide a method for analyzing the diagenesis of clay minerals by combining physical and numerical simulations, in order to solve the technical problem that existing technologies cannot achieve accurate quantitative analysis of the diagenesis of organic-rich clay shale reservoirs at the geological scale.

[0004] To achieve the above objectives, one embodiment of the present invention provides a method for analyzing the diagenesis of clay minerals by combining physical and numerical simulations, comprising the following steps:

[0005] Select a single clay mineral and prepare a formation aqueous solution;

[0006] Clay minerals and formation aqueous solutions were separately loaded into multiple reaction vessels for diagenetic physics simulation.

[0007] Establish a numerical simulation model with the same conditions as the physical simulation experiment, and output mineral and ion data;

[0008] The mineral dissolution rate was determined by fitting the results of physical simulation experiments and numerical simulations with mineral and ion data.

[0009] Based on the mineral dissolution rate, a geological model was established to simulate the diagenesis of single clay minerals over a geological timescale.

[0010] In one preferred embodiment of the present invention, the mass ratio of clay mineral to formation aqueous solution is 1:10.

[0011] In one preferred embodiment of the present invention, the clay monominerals include montmorillonite, kaolinite, chlorite, and illite.

[0012] In one preferred embodiment of the present invention, the formation water solution is prepared according to the common formation water components of terrestrial clay-rich shale to form a formation water solution under the corresponding temperature and pressure.

[0013] One preferred embodiment of the present invention includes the following steps in diagenetic physical simulation:

[0014] The reactor was emptied.

[0015] After venting, adjust the temperature and pressure of the reactor.

[0016] Collect the components of the product liquid, perform quantitative testing of ionic components, and calculate the pH value of the product liquid.

[0017] In one preferred embodiment of the present invention, the temperature and pressure inside the reactor need to be monitored in real time during the diagenetic physics simulation process.

[0018] One preferred embodiment of the present invention is a reaction vessel temperature adjustment method as follows: the temperature is increased to 75%-85% of the experimental set temperature value at a rate of 10℃ / min-20℃ / min, and after holding at the temperature for 1.5h-2.5h, the temperature is increased to the set temperature at a rate of 3℃ / min-7℃ / min.

[0019] In one preferred embodiment of the present invention, the insoluble substances in the product solution need to be dissolved before quantitative testing of ionic components.

[0020] One preferred embodiment of the present invention involves determining the mineral dissolution rate by the following steps: adjusting the dissolution rate of clay minerals to fit the mineral and ion data from physical simulation experiments with the mineral and ion data from numerical simulations, thereby determining the true dissolution rate of a single clay mineral.

[0021] One preferred embodiment of the present invention is that the establishment of the numerical simulation model includes: using TOUGHREACT software to establish a high-pressure reactor reaction model with the same physical simulation experimental conditions, obtaining a numerical model, and performing numerical simulation.

[0022] In summary, the beneficial effects of the present invention are as follows:

[0023] 1. This invention uses clay minerals as the experimental object, sets up indoor physical experiments under different temperature and pressure conditions, and monitors the changes in produced fluid ions in real time. Simultaneously, a numerical simulation model with conditions identical to the indoor physical experiments is established to conduct numerical simulation studies at the same time scale. The results of the physical simulation experiments constrain the numerical simulation parameters. By adjusting the mineral dissolution kinetic parameters in real time, the numerical simulation results are compared and verified with the physical simulation results, making the numerical simulation results closer to actual conditions. Finally, using the mineral dissolution kinetic parameters corrected by the physical experiment results as a benchmark, a quantitative study of the diagenesis of organic-rich clay rocks at the geological scale is achieved.

[0024] 2. This invention is the first to use indoor physical simulation results as a benchmark to correct key parameters in numerical simulations, including the mineral dissolution rate constant. Based on this, a corresponding geological model is established, and corresponding formation temperatures and pressures are set. Through numerical simulation software, the geochemical dynamics of single clay minerals in weakly acidic fluids at the geological scale is studied. The invention systematically clarifies the chemical diagenetic characteristics of montmorillonite-illite-kaolinite-chlorite, a common mineral in organic-rich clay rocks. This provides a foundation for the quantitative evolution of minerals in organic-rich shale with different clay mineral compositions at different geological periods. Furthermore, it accurately characterizes key production parameters such as physical properties and brittleness of organic-rich rocks at different diagenetic stages, contributing to the large-scale and efficient exploration of unconventional oil and gas. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating a method for analyzing the diagenesis of clay minerals that combines physical and numerical simulations according to the present invention.

[0026] Figure 2 This is a schematic diagram of the physical simulation device in one embodiment of the present invention;

[0027] Figure 3a This is a quantitative evolution characteristic diagram of calcium montmorillonite at the geological scale in the embodiments of the present invention;

[0028] Figure 3b This is a quantitative evolution characteristic diagram of kaolinite at the geological scale in the embodiments of the present invention;

[0029] Figure 3c This is a quantitative evolution characteristic diagram of illite at the geological scale in the embodiments of the present invention;

[0030] Figure 3d This is a quantitative evolution characteristic diagram of chlorite at the geological scale in an embodiment of the present invention.

[0031] Among them, 1-CO2 storage tank, 2-back pressure valve, 3-reaction vessel. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0033] This invention provides a method for analyzing the diagenesis of clay minerals by combining physical and numerical simulations, such as... Figure 1 As shown, it includes the following steps:

[0034] Step 1: Select clay minerals and prepare formation water solutions; specifically, select four common clay minerals that make up terrestrial clay-rich shale: montmorillonite, kaolinite, chlorite and illite, and prepare formation water solutions at the corresponding temperature (T) and pressure (P) according to the common formation water components of terrestrial clay-rich shale.

[0035] Step 2: The clay minerals and formation aqueous solutions are separately placed into multiple reaction vessels 3 for diagenetic physical simulation. Specifically, equal masses of the four clay minerals from Step 1 are weighed, wrapped in high-permeability filters, and placed in four independent high-temperature and high-pressure reaction vessels. To ensure the solution remains in excess throughout the reaction, the prepared formation aqueous solution is placed in the four independent high-temperature and high-pressure reaction vessels at a mass ratio of 1:10 for the clay minerals. Diagenetic physical simulation is then performed using a physical simulation device. The physical simulation device is as follows: Figure 2 As shown, it includes four reaction vessels 3, each reaction vessel 3 is equipped with a back pressure valve 2, and each reaction vessel 3 is connected to a CO2 storage tank 1, the purpose of which is to use CO2 for venting.

[0036] The diagenetic physical simulation specifically includes the following steps:

[0037] Step ①: Evacuate reactor 3; specifically, before heating and pressurizing, use high-purity CO2 gas (99.999%) to circulate and inject and release the gas into the four high-temperature and high-pressure reactors 3 times to ensure that there is no air residue in the reactors;

[0038] Step 2: After purging, adjust the temperature and pressure of reactor 3; specifically, after the gas injection is completed, first rapidly increase the temperature to 80% of the experimental set temperature value at 15℃ / min, keep the temperature constant for 2 hours, then increase the temperature to the set temperature at 5℃ / min. After the temperature inside the reactor stabilizes, increase or release CO2 gas through the pressure valve to adjust the internal pressure of the high-pressure reactor to the set value.

[0039] Step 3: Collect the product liquid components, perform quantitative testing of ionic components and calculate the pH value of the product liquid; Specifically, after the experiment, collect the product liquid components, use an appropriate amount of dilute hydrochloric acid to dissolve the insoluble matter in the product liquid, perform quantitative testing of ionic components, and, in combination with the solution components and experimental temperature and pressure conditions, reconstruct and calculate the pH value of the product liquid.

[0040] During the diagenetic physics simulation, pressure sensors are used in conjunction with computers to monitor the temperature and pressure data inside the reactor 3, ensuring that it remains within the set experimental temperature and pressure range.

[0041] Step 3: Establish a numerical simulation model with the same conditions as the physical simulation experiment and output mineral and ion data; specifically, use TOUGHREACT software to establish a high-pressure reactor reaction model with the same experimental conditions as the physical experiment, perform numerical simulation, and output the corresponding mineral and ion data.

[0042] Step 4: Determine the mineral dissolution rate by fitting the physical simulation results and numerical simulation results with mineral and ion data; determining the mineral dissolution rate includes the following steps: adjusting the dissolution rate of clay minerals so that the mineral and ion data from the physical simulation results are fitted with the mineral and ion data from the numerical simulation, thereby determining the true dissolution rate of a single clay mineral.

[0043] Step 5: Based on the mineral dissolution rate, establish a geological model and simulate the diagenesis of clay single minerals within a geological timescale; specifically, based on the mineral dissolution rate corrected by physical experimental results in Step 4, set the corresponding stratum temperature and pressure, and simulate the diagenesis of clay single minerals within a geological timescale.

[0044] Example

[0045] This embodiment takes surface diagenesis under surface conditions as an example. It provides a method combining physical and numerical simulations to analyze clay mineral diagenesis, specifically a quantitative evaluation method for single-mineral diagenesis in organic-rich clay shale at the geological scale, to address the evolutionary characteristics of key parameters such as reservoir properties and rock brittleness in organic-rich shale at different thermal evolution stages. The specific implementation includes the following steps:

[0046] Step 1: Select four common clay minerals, montmorillonite, illite, kaolinite and chlorite, and use XRD to test their mineral purity. The purity should be greater than 90%.

[0047] Step 2: Prepare the formation aqueous solution under surface conditions. The solution and clay mineral are loaded into four high-pressure reactors at a mass ratio of 10:1. High-purity CO2 (>99.999%) gas is repeatedly injected and removed to purge the air from the reactors.

[0048] Step 3: Heat to the set value, and at the same time adjust the system pressure to the experimental set value through the back pressure valve. Start the experiment, and the computer records the temperature and pressure changes of the reaction system in real time.

[0049] Step 4: Establish a numerical model with the same physical experimental conditions and perform numerical simulation calculations on the same time scale;

[0050] Step 5: Correct the numerical simulation results with the ion result curve of the physical experiment product, and make the two results as consistent as possible by continuously adjusting the mineral dissolution kinetic parameters;

[0051] Step 6: Based on the corrected single-mineral dissolution kinetic parameters from Step 5, establish numerical simulations under corresponding conditions, conduct numerical simulation studies at the geological scale, and obtain the single clay mineral evolution curves over geological history, such as... Figures 3a-3d As shown in the figure, Δφ is the volume fraction of mineral abundance relative to time 0, where a is calcium montmorillonite, b is kaolinite, c is illite, and d is chlorite.

[0052] Step 7: Using the evolution curves of the four single clay minerals in Step 6 on a geological time scale as a guideline, and based on the actual clay mineral composition of organic clay-rich rocks, establish a geological model that conforms to the actual situation, set corresponding experimental parameters, and conduct a study on the diagenesis of organic clay-rich rocks on a geological scale.

[0053] In summary, the method of analyzing the diagenesis of clay minerals by combining physical and numerical simulations in this invention uses the results of indoor physical simulations as a guideline to correct key parameters in the numerical simulation, such as the mineral dissolution rate constant. Based on this, a corresponding geological model is established, and corresponding formation temperature and pressure are set. Through numerical simulation software, the geochemical dynamics behavior of single clay minerals in weakly acidic fluids at the geological scale is studied.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for analyzing diagenesis of clay minerals by combining physical and numerical simulations, characterized by, The method comprises the following steps: selecting clay single minerals and configuring formation water solution; loading the clay single minerals and the formation water solution into multiple reaction kettles respectively to perform diagenetic physical simulation; establishing a numerical simulation model with the same experimental conditions as the physical simulation and outputting mineral and ion data; fitting the physical simulation results and the numerical simulation results according to the mineral and ion data to determine mineral dissolution rate; establishing a geological model based on the mineral dissolution rate to simulate diagenesis of the clay single minerals in a geological time scale.

2. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 1, characterized in that: The mass ratio of the clay single minerals to the formation water solution is 1:

10.

3. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 1 or 2, characterized in that: The clay single minerals include montmorillonite, kaolinite, chlorite and illite.

4. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 1 or 2, characterized in that: The formation water solution is configured according to the formation water components of the common continental clay-rich shale to form a formation water solution under corresponding temperature and pressure.

5. The method for analyzing diagenesis of clay minerals by physical and numerical simulation according to claim 1, wherein, The diagenetic physical simulation comprises the following steps: emptying the reaction kettles; adjusting the temperature and pressure of the reaction kettles after emptying; collecting the produced liquid components to perform ion component quantitative test and pH value calculation.

6. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 5, characterized in that: The temperature and pressure in the reaction kettles need to be monitored in real time during the diagenetic physical simulation.

7. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 5, characterized in that: The temperature adjustment method of the reaction kettles is as follows: heating at 10-20 ℃ / min to 75-85% of the set temperature value, keeping constant for 1.5-2.5 h, and then heating at 3-7 ℃ / min to the set temperature.

8. The method for analyzing the diagenesis of clay minerals by physical and numerical simulation according to claim 5, characterized in that: The insoluble substances in the produced liquid need to be dissolved before the ion component quantitative test.

9. The method for analyzing diagenesis of clay minerals by physical and numerical simulation according to claim 1, wherein, The determination of the mineral dissolution rate comprises the following steps: adjusting the dissolution rate of the clay minerals to make the mineral and ion data of the physical simulation results fit the mineral and ion data of the numerical simulation, so as to determine the real dissolution rate of the clay single minerals.

10. The method for analyzing diagenesis of clay minerals by physical and numerical simulation according to claim 1, wherein, The establishment of the numerical simulation model comprises the following steps: using TOUGHREACT software to establish a high-pressure kettle reaction model with the same experimental conditions as the physical simulation, obtaining a numerical model, and performing numerical simulation.

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