Anisotropic large-size artificial core preparation device and method

Abstract

The invention discloses an anisotropic large-size artificial rock core preparation device and method. The device comprises a forming system used for providing a rock core forming environment, an axial pressure loading system used for simulating rock core stratum axial pressure, a confining pressure loading system used for simulating rock core stratum confining pressure, a pore pressure loading system used for simulating rock core stratum pore pressure and a heating system used for simulating rock core stratum temperature. The collecting and metering system is used for collecting discharged pore pressure fluid and respectively metering a gas phase and a liquid phase, the data acquisition system can acquire various information during preparation, and the control system is used for controlling the systems to work according to data fed back by the data acquisition system so as to simulate the diagenesis process of natural rock and recording and analyzing the data. According to the invention, a coupling environment of a real rock diagenesis process can be simulated, and anisotropy and reservoir heterogeneity can be simulated.

Description

Technical Field

[0001] This invention relates to the preparation of rock samples, and more specifically to an anisotropic large-size artificial rock core preparation device and method. Background Technology

[0002] In the development of deep geological resources and energy, experimental simulation studies of stratigraphic cores are necessary to obtain relevant experimental data. This data is crucial for revealing diagenetic mechanisms, fluid flow patterns in porous media, and subsequent analyses, thus creating a significant demand for stratigraphic cores. However, actual stratigraphic core sampling is complex, difficult, and costly. Natural cores obtained are insufficient to meet the needs of a large number of experiments. Therefore, it is essential to artificially prepare artificial cores that meet the relevant physicochemical properties of the target stratigraphic layer for related experimental research.

[0003] Currently, common methods for preparing artificial rock cores include quartz sand filling, epoxy resin pressing, and aluminum phosphate quartz sintering. Quartz sand filling produces artificial cores with low cementation, suitable only for shallow, loose strata. Epoxy resin pressing is simple and reproducible, but its structure differs from natural cores. Aluminum phosphate quartz sintering, however, destroys the original core components and content at high temperatures, resulting in core properties inconsistent with natural cores. Furthermore, while controlling the thermo-pressing process and using natural rock fragments in their composition and proportion can produce artificial cores with some similarity to natural cores in porosity, permeability, and other physical properties, they cannot simulate the coupled environment of deep rocks under the combined effects of geostress, pore pressure, and chemical behavior. They also cannot simulate the diagenetic evolution process under this coupled environment, resulting in significant differences in mechanical properties and chemical structure, making the prepared cores unsuitable for production and research needs.

[0004] Among various artificial core testing methods, in addition to meeting the required natural core formation conditions as much as possible, sample size is also one of the decisive factors. Currently, the small cylindrical samples (Ø25mm×50mm, Ø50mm×100mm) widely used in artificial cores not only make it difficult to truly represent or imitate the "structural characteristics" of the research object (such as a large rock mass), but also make it difficult to simulate anisotropy and reservoir heterogeneity. Summary of the Invention

[0005] The purpose of this invention is to provide an anisotropic large-size artificial core preparation device and an anisotropic large-size artificial core preparation method. In this device and method, this application can simulate the coupled environment under the combined action of axial pressure, confining pressure, pore pressure, temperature, chemical behavior and other factors experienced by real rock formation process, can simulate anisotropy and reservoir heterogeneity, and can prepare anisotropic large-size artificial cores.

[0006] The technical solution adopted in this invention is: An anisotropic large-size artificial rock core preparation device includes: The molding system provides a core molding environment and includes a triaxial loading device. The triaxial loading device includes a closed reaction chamber and a molding cylinder for holding multiple artificial cores. The reaction chamber has a bottom pad at the bottom, side pads around the inside, and a loading rod that extends into the sealed upper end. The upper end of the loading rod is a loading head. The loading rod and the bottom pad are respectively provided with an input channel and an output channel for pore pressure fluid. The bottom pad and the reaction chamber are respectively provided with an input channel and an output channel for confining pressure fluid. The molding cylinder is placed on the bottom pad. The upper and lower ends of the molding cylinder are provided with microporous filter blocks for filtration, and the inside is provided with a liner for separating multiple molding spaces. Each molding space is used to hold different artificial cores. The pore pressure fluid input channel corresponds one-to-one with each molding space. Axial compression loading system is used to apply pressure to all artificial rock cores in the forming cylinder through a loading head to simulate the axial compression of the rock core formation; The confining pressure loading system is used to pressurize and deliver confining pressure fluid into the reaction chamber through the confining pressure fluid input channel to simulate the confining pressure of the core formation; The pore pressure loading system is used to pressurize and deliver pore pressure fluid to the artificial rock core in each molding space through each pore pressure fluid input channel to simulate the pore pressure of the rock core formation. A heating system is used to heat the reaction chamber to simulate the temperature of the core formation; A collection and metering system is used to collect the pore pressure fluid discharged from the pore pressure fluid output channel and to separately meter the gas phase and the liquid phase; The data acquisition system can collect axial pressure, confining pressure, pore pressure, temperature, displacement of the loading head, acoustic emission signals of the artificial rock core, and input and output information of pore pressure fluid during preparation. The control system is used to control the operation of each system based on the data feedback from the data acquisition system to simulate the diagenesis process of natural rocks and record and analyze the data.

[0007] Preferably, the molding system further includes a base, a column, a reaction frame, and a guide rail. The reaction frame is located directly above the base, the column is connected between the base and the reaction frame, the guide rail extends from the outside of the base to the base, the triaxial loading device is movably fitted on the guide rail, and the triaxial loading device is in the working position when it moves to the base. The reaction frame is used to provide reaction force for the axial compression loading system.

[0008] Preferably, the reaction chamber has an opening at the upper end and is open at the lower end. An upper seat and a lower seat are respectively provided on the upper and lower sides of the reaction chamber. The upper seat is placed on the reaction chamber as a ballast. The loading rod passes through the upper seat and then seals through the opening. The lower end of the reaction chamber is sealed and placed on the lower seat and connected to the lower seat through a retainer. The lower seat closes the lower end of the reaction chamber. The bottom pad is placed on the lower seat and positioned by a pin. After the lower seat and the bottom pad are positioned, their channels are connected to each other.

[0009] Preferably, the gasket divides the internal space of the molding cylinder into four rectangular molding spaces, each molding space having dimensions of 250mm×250mm×250mm or 500mm×500mm×500mm.

[0010] Preferably, the axial pressure loading system includes a hydraulic jack for applying pressure to the loading head and an axial pressure controller for controlling the hydraulic jack.

[0011] Preferably, the confining pressure loading system includes a confining pressure fluid container for storing confining pressure fluid and a confining pressure tracking pump for pressurizing and delivering the confining pressure fluid in the confining pressure fluid container to the confining pressure fluid input channel.

[0012] Preferably, the pore pressure loading system includes a gas injection module, a liquid injection module, and a mixing pressure vessel; the gas injection module includes a gas container, a first constant-speed constant-pressure pump, and a gas intermediate pressure vessel connected in sequence, with an inlet pressure regulating valve and a safety valve provided on the pipeline between the gas container and the first constant-speed constant-pressure pump; the liquid injection module includes a liquid container, a second constant-speed constant-pressure pump, and a liquid intermediate pressure vessel connected in sequence; the gas intermediate pressure vessel and the liquid intermediate pressure vessel are respectively connected to the mixing pressure vessel, and the mixing pressure vessel is respectively connected to each pore pressure fluid input channel.

[0013] Preferably, the heating system includes an electric heating probe disposed in the side pad block, an electric heating sleeve sleeved outside the reaction chamber, a preheater electrically connected to the electric heating probe and the electric heating sleeve respectively, and a heating controller electrically connected to the preheater. The external wiring of the electric heating probe passes through the external wiring channel on the bottom pad block and exits the reaction chamber.

[0014] Preferably, the collection and metering system includes a condenser connected to the pore pressure fluid output channel, a gas-liquid separator connected to the condenser, a dryer connected to the gas outlet of the gas-liquid separator, a gas meter connected to the dryer, and a liquid meter connected to the liquid outlet of the gas-liquid separator.

[0015] Preferably, the data acquisition system includes a displacement sensor for monitoring the displacement of the loading head, an axial pressure sensor for monitoring the output pressure of the loading head, a confining pressure sensor for monitoring the output confining pressure of the confining pressure loading system, an acoustic emission probe installed inside the loading rod for monitoring the acoustic emission signal of the artificial rock core, and a pressure sensor, a temperature sensor, and a pH sensor installed at the pore pressure fluid input channel and the pore pressure fluid output channel. The acoustic emission probe and each sensor are electrically connected to the control system through the data acquisition instrument.

[0016] Preferably, all components that come into contact with the pore pressure fluid during its journey from the storage container to the pore pressure fluid inlet channel and from the pore pressure fluid outlet channel to the collection and metering system are made of corrosion-resistant materials.

[0017] A method for preparing large-size anisotropic artificial rock cores: Before preparation: Select a certain number of target cores, obtain the formation temperature, stress state, mineral composition, grain size distribution, porosity and permeability range of the target cores under real formation conditions, collect drilling cuttings or natural mineral particles with similar mineral composition to the target cores, crush and screen them according to the mineral composition and grain size distribution of the target cores to prepare the skeleton particles for artificial cores, and dry and dehydrate them; using the skeleton particles, first prepare multiple mixtures according to the anisotropy of the formation, with different mineral composition ratios and grain size distributions in each mixture, mix each mixture first, add artificial binder and mix, then screen, and then compact in layers to obtain multiple preliminary artificial cores, and then place each artificial core into the molding cylinder and form molding spaces separated by a liner, and set microporous filter blocks for filtration at the upper and lower ends of the molding cylinder, so that the molding cylinder is in a closed reaction chamber; During preparation: pressure is applied to all artificial cores in the molding cylinder to simulate the axial pressure of the core formation; confining pressure fluid is pressurized and transported into the reaction chamber to simulate the confining pressure of the core formation; pore pressure fluid is pressurized and transported into each artificial core in the molding space to simulate the pore pressure of the core formation; and the reaction chamber is heated to simulate the temperature of the core formation. During molding, the flow rate of the pore pressure fluid is kept within a certain range, and the axial pressure, confining pressure, and temperature are gradually increased to the target values. The loading rate of the confining pressure and axial pressure is adjusted according to the monitored acoustic emission signal of the artificial core and the calculated permeability value of the artificial core. The discharged pore pressure fluid is collected, and the gas phase and liquid phase are measured separately to analyze the chemical behavior reaction of the artificial core. At the end of molding, the stress-strain curve of the artificial core is obtained by monitoring the axial pressure and the displacement of the axial pressure loading, so that the error between the final artificial core and the target core in permeability, acoustic emission signal, and stress-strain is controlled within 10%.

[0018] Preferably, when the pore pressure fluid is a single gas or liquid, the formula for calculating the permeability of the artificial core is:

[0019] in, The permeability of an artificial rock core when the pore pressure fluid is a single gas or liquid. The flow rate of the fluid through the pore pressure of the artificial rock core. The viscosity of the pore pressure fluid is... The length of the artificial rock core. The cross-sectional area of ​​the artificial rock core. This represents the pressure difference before and after the pore pressure fluid passes through the artificial core.

[0020] Preferably, when the pore pressure fluid is a mixture of gas and liquid: Absolute permeability of artificial rock cores for:

[0021] in, The number of capillaries; The representative length of the artificial rock core, The length of the artificial rock core; For the maximum pore radius, For minimum pore radius, Where is the pore radius; Let be the probability density function of the pore size distribution in the artificial rock core; It is the total pore area on the cross-sectional area of ​​the compacted artificial rock core; T Temperature of the artificial rock core; in, , , , The calculation formula is:

[0022]

[0023]

[0024]

[0025] in, It refers to the porosity of the artificial rock core; Gas permeability in artificial rock cores and liquid phase permeability They are respectively:

[0026]

[0027] in, For the gas saturation of artificial rock cores, The water saturation of the artificial rock core; For the trapezoidal pore ratio, The ratio of straight pores, The proportion of straight pores was determined by nuclear magnetic resonance. T 2. Calculations are performed when the cutoff value is less than 0.6ms; Indicates the average pore radius; , , The calculation formula is:

[0028]

[0029]

[0030] in, For movable water saturation, To bind water saturation; , The calculation formula is:

[0031]

[0032] in, For artificial rock core nuclear magnetic resonance T 2. The throat radius corresponding to a cutoff value of 0.6ms; This is the length of the capillary bend. The critical pore radius under centrifugal force corresponding to the initial water saturation in the artificial rock core. The critical pore radius under centrifugal force corresponding to the bound water saturation in the artificial rock core; The thickness of the stagnant water adhering to the capillary; , , , The calculation formula is:

[0033]

[0034]

[0035]

[0036] in, The average tortuosity; It is the contact angle between the gas and liquid phases; The pressure difference before and after passing through the artificial core; The calculation formula is: .

[0037] Preferably, during the molding process, the temperature and acoustic emission signal of the artificial rock core, as well as the temperature, pressure, and pH value of the pore pressure fluid before and after passing through the artificial rock core are monitored. Combined with the chemical behavior reaction analysis of the artificial rock core, the changes in the microstructure and composition of the artificial rock core at different times are obtained.

[0038] Preferably, after the artificial rock core is prepared, the injection of pore pressure fluid is turned off, so that the axial pressure, confining pressure and temperature decrease in a gradient until the temperature returns to room temperature and the pressure returns to atmospheric pressure. Then, the confining pressure fluid and pore pressure fluid in the reaction chamber are collected and recovered separately.

[0039] The beneficial effects of this invention are: In this device and method, in addition to simulating the coupled environment of axial pressure, confining pressure, pore pressure, temperature, and chemical behavior experienced during the diagenesis of real rocks, the molding cylinder is divided into multiple molding spaces by a liner. Mixtures can be configured in the molding spaces according to the anisotropy of the formation. The mineral composition ratio and grain size distribution of each mixture are different. Pore pressure fluid can be introduced into the artificial core in each molding space. Therefore, it can also simulate anisotropy and reservoir heterogeneity. Thus, it is applicable to a variety of rock types. It can not only prepare anisotropic large-size artificial cores, but also simulate the mineral and oil and gas evolution processes of uranium-bearing sandstone, shale, carbonate rocks, and source rocks under different temperatures and pressures, providing sample analysis. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the anisotropic large-size artificial rock core preparation device in this invention.

[0042] Figure 2 This is a schematic diagram of the molding system in this invention, with the triaxial loading device in the pick-and-place position.

[0043] Figure 3 This is a schematic diagram of the structure of the triaxial loading device in this invention.

[0044] Figure 4 This is a cross-sectional view of the triaxial loading device in this invention.

[0045] In the picture: 1-Artificial rock core; 21-Triaxial loading device; 22-Base; 23-Column; 24-Reaction frame; 25-Guide rail; 2101-Loading head; 2102-Loading rod; 2103-Upper seat; 2104-Reaction chamber; 2105-Clad seat; 2106-Lower seat; 2107-Forming cylinder; 2108-Microporous filter block; 2109-Pad; 2110-Lifting ring; 2111-Bottom pad; 2112-Pin; 2113-Side pad; a-Porous pressure fluid input channel; b-Porous pressure fluid output channel; c-Containing pressure fluid input channel; d-Containing pressure fluid output channel; e-External wiring channel; 31-Hydraulic jack; 32-Axis pressure controller; 41-Confining pressure fluid container; 42-Confining pressure tracking pump; 51-Gas container; 52-Inlet pressure regulating valve; 53-Safety valve; 54-First constant speed and constant pressure pump; 55-Gas intermediate pressure vessel; 56-Liquid container; 57-Second constant speed and constant pressure pump; 58-Liquid intermediate pressure vessel; 59-Mixing pressure vessel; 61-Preheater; 62-Heating controller; 63-Electric heating probe; 64-Electric heating jacket; 71-Condenser; 72-Gas-Liquid Separator; 73-Dryer; 74-Gas Meter; 75-Liquid Meter; 81-Displacement sensor; 82-Axial pressure sensor; 83-Containing pressure sensor; 84-Pressure sensor; 85-Temperature sensor; 86-pH sensor; 87-Data acquisition instrument; 88-Acoustic emission probe; 9-Control system. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0048] In this invention, it should also be noted that the terms "upper," "lower," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first XXX" and "second XXX" are used only for descriptive and distinguishing purposes, and should not be construed as indicating or implying relative importance.

[0049] Example 1 This embodiment discloses an anisotropic large-size artificial rock core preparation device, such as... Figures 1 to 4 As shown, it includes a molding system, an axial pressure loading system, a confining pressure loading system, a pore pressure loading system, a heating system, a collection and metering system, a data acquisition system, and a control system 9.

[0050] About the molding system: In this apparatus, the forming system provides the environment for core forming. For example... Figures 1 to 4 As shown: The molding system includes a triaxial loading device 21, which includes a reaction chamber 2104 and a molding cylinder 2107. The reaction chamber 2104 is a closed structure. A bottom pad 2111 is provided at the bottom of the reaction chamber 2104, side pads 2113 are provided around the inside, and a loading rod 2102 extends into the sealed upper end. The upper end of the loading rod 2102 is a loading head 2101. A pore pressure fluid input channel a and a pore pressure fluid output channel b are respectively provided on the loading rod 2102 and the bottom pad 2101. The bottom pad 2111 and the reaction chamber 2104 are respectively provided with a confining pressure fluid input channel c and a confining pressure fluid output channel d; the forming cylinder 2107 is used to hold multiple artificial rock cores 1. The forming cylinder 2107 is placed on the bottom pad 2111. The upper and lower ends of the forming cylinder 2107 are provided with microporous filter blocks 2108 for filtration, and the inside is provided with a liner 2109 for separating and forming multiple forming spaces. Each forming space is used to hold different artificial rock cores 1. The pore pressure fluid input channel a corresponds to each forming space.

[0051] In this embodiment, preferably: Figure 1 and Figure 2 As shown, the molding system also includes a base 22, a column 23, a reaction frame 24, and a guide rail 25. The reaction frame 24 is located directly above the base 22. The column 23 connects the base 22 and the reaction frame 24. The guide rail 25 extends from the outside of the base 22 to the base 22. The triaxial loading device 21 is movably fitted onto the guide rail 25. When the triaxial loading device 21 moves onto the base 22, it is in the working position. The reaction frame 24 is used to provide reaction force for the axial compression loading system. In this configuration, the triaxial loading device 21 can be moved to switch between the working position and the pick-up / placement position. In the pick-up / placement position, the triaxial loading device 21 is outside the base 22, and the hoisting equipment can pick up and place the artificial rock core 1 and other components from the reaction chamber 2104 from above.

[0052] In this embodiment, preferably: Figure 3 As shown, the reaction chamber 2104 has an opening at the upper end and is open at the lower end. An upper seat 2103 and a lower seat 2106 are respectively located on the upper and lower sides of the reaction chamber 2104. The upper seat 2106 serves as a ballast on the reaction chamber 2104. The loading rod 2102 passes through the upper seat 2103 and then seals through the opening. The lower end of the reaction chamber 2104 is sealed and placed on the lower seat 2106, connected to it via a retainer 2105. The lower seat 2106 seals the lower end of the reaction chamber 2104. A bottom pad 2111 is placed on the lower seat 2106 and positioned by a pin 2112. After positioning, the channels of the lower seat 2106 and the bottom pad 2111 are aligned. This design makes the reaction chamber 2104 more stable and reliable during operation and facilitates assembly.

[0053] In this embodiment, preferably: Figure 3 and Figure 4 As shown, the gasket 2109 divides the internal space of the molding cylinder 2107 into four rectangular molding spaces, each with dimensions of 250mm×250mm×250mm or 500mm×500mm×500mm.

[0054] In this embodiment, preferably: Figure 3 and Figure 4 As shown, the forming cylinder 2107 is equipped with a lifting ring 2110 for easy operation.

[0055] In this embodiment, preferably, the side pad 2113 has a coefficient of thermal expansion greater than 10. -7 ℃ -1 The reaction chamber 2104, bottom pad 2111, forming cylinder 2107, liner 2109 and loading rod 2102 are all made of materials with a thermal expansion coefficient less than 0.001 times that of the side pad. The liner 2109 is made of PTEF material.

[0056] Regarding axial compression loading systems: In this device, the axial pressure loading system is used to apply pressure to all artificial rock cores 1 within the forming cylinder 2107 via the loading head 2101 to simulate the axial pressure of the rock core formation. In this embodiment, preferably, as shown... Figure 1 As shown, the axial pressure loading system includes a hydraulic jack 31 for applying pressure to the loading head 2101 and an axial pressure controller 32 for controlling the hydraulic jack 31.

[0057] Regarding the confining pressure loading system: In this device, the confining pressure loading system is used to pressurize and deliver confining pressure fluid into the reaction chamber 2104 through the confining pressure fluid input channel c to simulate the confining pressure of the core formation. In this embodiment, preferably, as shown... Figure 1 As shown, the confining pressure loading system includes a confining pressure fluid container 41 for storing confining pressure fluid and a confining pressure tracking pump for pressurizing and delivering the confining pressure fluid in the confining pressure fluid container 41 to the confining pressure fluid input channel c. 42 Regarding pore pressure loading systems: In this device, the pore pressure loading system is used to pressurize and deliver pore pressure fluid to the artificial rock core 1 in each molding space through each pore pressure fluid input channel a to simulate the pore pressure of the rock core formation. In this embodiment, preferably, as shown... Figure 1As shown, the pore pressure loading system includes a gas injection module, a liquid injection module, and a mixing pressure vessel 59. The gas injection module includes a gas container 51, a first constant-speed constant-pressure pump 54, and a gas intermediate pressure vessel 55 connected in sequence. An inlet pressure regulating valve 52 and a safety valve 53 are provided on the pipeline between the gas container 51 and the first constant-speed constant-pressure pump 54. The liquid injection module includes a liquid container 56, a second constant-speed constant-pressure pump 57, and a liquid intermediate pressure vessel 58 connected in sequence. The gas intermediate pressure vessel 55 and the liquid intermediate pressure vessel 58 are respectively connected to the mixing pressure vessel 59, and the mixing pressure vessel 59 is respectively connected to each pore pressure fluid input channel a.

[0058] The pore pressure fluid can be gas, liquid, or a gas-liquid mixture. When only the gas injection module and the mixing pressure vessel 59 are engaged, only gas is injected. When only the liquid injection module and the mixing pressure vessel 59 are engaged, only liquid is injected. When the gas injection module, the liquid injection module, and the mixing pressure vessel 59 are engaged simultaneously, a gas-liquid mixture is injected. The gas intermediate pressure vessel 55 and the liquid intermediate pressure vessel 58 are used for pre-pressurization. The mixing pressure vessel 59 can mix gas and liquid or accept a single gas and liquid. The first constant speed and constant pressure pump 54 and the second constant speed and constant pressure pump 57 are used to apply constant speed and constant pressure to the pore pressure fluid.

[0059] Regarding the heating system: In this device, a heating system is used to heat the reaction chamber 2104 to simulate the temperature of the core formation. In this embodiment, preferably, as shown... Figure 1 , Figure 3 and Figure 4 As shown, the heating system includes an electric heating probe 63 housed within the side pad 2113, an electric heating sleeve 64 fitted over the reaction chamber 2104, a preheater 61 electrically connected to both the electric heating probe 63 and the electric heating sleeve 64, and a heating controller 62 electrically connected to the preheater 61. The external wiring of the electric heating probe 63 extends out of the reaction chamber 2104 through the external wiring channel e on the bottom pad 2111. The electric heating probe 63 can directly heat the inside of the reaction chamber 2104, while the electric heating sleeve 64 heats the outer shell of the reaction chamber 2104, preventing heat loss from the reaction chamber 2104 and serving as insulation and preheating functions.

[0060] Regarding the data collection and measurement system: In this device, a collection and metering system is used to collect the pore pressure fluid discharged from the pore pressure fluid output channel b and to separately meter the gas phase and the liquid phase. In this embodiment, preferably, as shown... Figure 1 As shown, the collection and metering system includes a condenser 71 connected to the pore pressure fluid output channel b, a gas-liquid separator 72 connected to the condenser 71, a dryer 73 connected to the gas outlet of the gas-liquid separator 72, a gas meter 74 connected to the dryer 73, and a liquid meter 75 connected to the liquid outlet of the gas-liquid separator 72.

[0061] About the data acquisition system: In this device, the data acquisition system can collect axial pressure, confining pressure, pore pressure, temperature, displacement of the loading head, acoustic emission signals from the artificial core, and input and output information of the pore pressure fluid during preparation. In this embodiment, preferably, as shown... Figure 1 and Figure 3 As shown, the data acquisition system includes a displacement sensor 81 for monitoring the displacement of the loading head 2101, an axial pressure sensor 82 for monitoring the output pressure of the loading head 2101, a confining pressure sensor 83 for monitoring the output confining pressure of the confining pressure loading system, an acoustic emission probe 88 installed in the loading rod 2102 for monitoring the acoustic emission signal of the artificial core 1, and a pressure sensor 84, a temperature sensor 85, and a pH sensor 86 installed at the pore pressure fluid input channel a and the pore pressure fluid output channel b. The acoustic emission probe 88 and each sensor are electrically connected to the control system 9 through the data acquisition instrument 57.

[0062] Regarding control and acquisition system 9: In this device, the control system 9 is used to control the operation of each system based on the data feedback from the data acquisition system to simulate the diagenesis process of natural rocks and record and analyze the data.

[0063] To accommodate corrosive pore pressure fluids, in this embodiment, all components that come into contact with the pore pressure fluid during its journey from the storage container to the pore pressure fluid input channel a and from the pore pressure fluid output channel b to the collection and metering system are made of corrosion-resistant materials, such as Hastelloy, HC276, 316L stainless steel, etc.

[0064] Example 2 This application discloses a method for preparing anisotropic large-size artificial rock cores. Taking a 500mm×500mm×500mm artificial sandstone core as an example, the method comprises the following steps: Step 1: A certain number of target cores were selected from a sedimentary basin in western Inner Mongolia, my country. Based on the depth of the samples taken, the formation temperature of the target cores was determined to be 100℃. The pressure exerted by the overlying rocks on the target cores was calculated. A point in the formation will experience a force caused by the compaction of the overlying rocks. The pressure of the overlying strata at a point in the fine-grained rock formation is equal to the sum of the total weight of the overlying strata at that point, expressed by the following formula:

[0065] in, The pressure of the overlying strata is MPa; ρ is the burial depth, in meters (m); g is the acceleration due to gravity, 9.8 m / s². 2 ; The average density of the formation is 2.16~2.65 g / cm³. 3 ; The target core is buried at a depth of 1500m. According to the above formula, the pressure of the overlying strata is 1500×2.55×9.8=38MPa.

[0066] Step Two: The mineral composition of the target core was analyzed by X-ray diffraction (XRD), and the particle size distribution of the target core was analyzed by a fully automated sieve particle size analyzer. The mineral composition and particle size distribution of the target core are shown in Table 1.

[0067] Table 1. Mineral composition and grain size distribution of the target core.

[0068] Step 3: Permeability and porosity analysis were performed on the target core to determine the range of porosity and permeability.

[0069] Step Four: Collect drilling cuttings or natural mineral particles with a mineral composition similar to the target core, and crush and screen them according to the mineral composition and particle size distribution of the target core to prepare the skeleton particles for artificial cores.

[0070] Step 5: The skeleton particles were dried and dehydrated at a constant temperature of 50℃ for 18~24h.

[0071] Step Six: Using framework particles, multiple mixtures are prepared according to the anisotropy of the formation, with different mineral composition ratios and grain size distributions in each mixture; for each mixture, the corresponding proportions of each mineral are determined according to the grain size distribution of the target core. x i Using an electronic balance, weigh out specific masses of rock cuttings of various sizes. The required masses of rock cuttings are as follows: m j = m × x i .

[0072] Step Seven: For each mixture, first use a mixer to stir evenly for 60 minutes; then add the artificial binder and mix evenly. The artificial binder can be YY4250A / B from the A / B series epoxy adhesive, keeping the content of the artificial binder at about 5% of the mineral weight; after the binder has fully adhered to the surface of the skeleton particles, screen it to ensure it passes through a 1000-mesh sieve; then compact each mixture in layers to obtain multiple preliminary artificial cores; then place each artificial core into a molding cylinder, which is separated by a liner to form a molding space, and set microporous filter blocks for filtration at the top and bottom of the molding cylinder to keep the molding cylinder in a closed reaction chamber.

[0073] Step 8: Pressure is applied to all artificial rock cores in the forming cylinder to simulate the axial pressure of the rock core formation; confining fluid is pressurized and transported into the reaction chamber to simulate the confining pressure of the rock core formation; pore pressure fluid is pressurized and transported into the artificial rock cores in each forming space to simulate the pore pressure of the rock core formation; and the reaction chamber is heated to simulate the temperature of the rock core formation. This simulates the coupled environment under the combined action of axial pressure, confining pressure, pore pressure, temperature, and chemical behavior experienced by real rocks during the rock formation process.

[0074] During the molding process, the flow rate of the pore pressure fluid is kept within a certain range, and the axial pressure, confining pressure, and temperature are gradually increased to the target values. The loading rate of the confining pressure and axial pressure is adjusted according to the monitored acoustic emission signal of the artificial core and the calculated permeability value of the artificial core. The discharged pore pressure fluid is collected and the gas phase and liquid phase are measured separately to analyze the chemical behavior reaction of the artificial core. At the end of the molding period, the stress-strain curve of the artificial core is obtained by monitoring the axial pressure and the displacement of the axial pressure loading, so that the error between the final artificial core and the target core in permeability, acoustic emission signal, and stress-strain is controlled within 10%.

[0075] In this embodiment, the target temperature is 100℃ and the target axial pressure is 38MPa. During the loading process, the axial pressure is always not less than the confining pressure. The axial pressure and confining pressure are maintained for 10 minutes for every 5MPa increase, and the temperature is maintained for 30 minutes for every 10℃ increase. In this embodiment, the pore pressure fluid is a mixture of CO2 gas and aqueous solution. After mixing for 40 minutes, the mixture is injected at a rate of 0.1~0.5mL / min.

[0076] During the molding process, the temperature and acoustic emission signals of the artificial rock core, as well as the temperature, pressure, and pH value of the pore pressure fluid before and after passing through the artificial rock core, are monitored. Combined with the chemical behavior reaction analysis of the artificial rock core, the changes in the microstructure and composition of the artificial rock core at different times are obtained.

[0077] In this embodiment, several time points were selected at 4h, 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, 40h, 44h, 48h, 52h, 56h, 60h, and 64h to obtain the changes in the microstructure and composition of the artificial rock core at the above time points.

[0078] Step Nine: After the artificial core is prepared, the injection of pore pressure fluid is turned off, so that the axial pressure, confining pressure and temperature decrease in a gradient until the temperature returns to room temperature and the pressure returns to atmospheric pressure. Then the confining pressure fluid and pore pressure fluid in the reaction chamber are collected and recovered separately.

[0079] The sequence numbers of the steps in the above embodiments do not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. Depending on the implementation needs, the steps described in this application can be broken down into more steps, or two or more steps or parts of the operations of steps can be combined into new steps to achieve the purpose of this invention.

[0080] In this embodiment, the pore pressure fluid is a mixture of gas and liquid. In this case, the permeability of the artificial core can be calculated using the following method.

[0081] Absolute permeability of artificial rock cores for:

[0082] in, The number of capillaries; The representative length of the artificial rock core, The length of the artificial rock core; For the maximum pore radius, For minimum pore radius, Where is the pore radius; Let be the probability density function of the pore size distribution in the artificial rock core; It is the total pore area on the cross-sectional area of ​​the compacted artificial rock core; T Temperature of the artificial rock core; in, , , , The calculation formula is:

[0083]

[0084]

[0085]

[0086] in, It refers to the porosity of the artificial rock core; Gas permeability in artificial rock cores and liquid phase permeability They are respectively:

[0087]

[0088] in, For the gas saturation of artificial rock cores, The water saturation of the artificial rock core; For the trapezoidal pore ratio, The ratio of straight pores, The proportion of straight pores was determined by nuclear magnetic resonance. T 2. Calculations are performed when the cutoff value is less than 0.6ms; Indicates the average pore radius; , , The calculation formula is:

[0089]

[0090]

[0091] in, For movable water saturation, To bind water saturation; , The calculation formula is:

[0092]

[0093] in, For artificial rock core nuclear magnetic resonance T 2. The throat radius corresponding to a cutoff value of 0.6ms; This is the length of the capillary bend. The critical pore radius under centrifugal force corresponding to the initial water saturation in the artificial rock core. The critical pore radius under centrifugal force corresponding to the bound water saturation in the artificial rock core; The thickness of the stagnant water adhering to the capillary; , , , The calculation formula is:

[0094]

[0095]

[0096]

[0097] in, The average tortuosity; It is the contact angle between the gas and liquid phases; The pressure difference before and after passing through the artificial core; The calculation formula is: .

[0098] In addition, when the pore pressure fluid is a single gas or liquid, the permeability of the artificial core can be calculated using the following methods.

[0099] The formula for calculating the permeability of artificial rock cores is:

[0100] in, The permeability of an artificial rock core when the pore pressure fluid is a single gas or liquid. The flow rate of the fluid through the pore pressure of the artificial rock core. The viscosity of the pore pressure fluid is... The length of the artificial rock core. The cross-sectional area of ​​the artificial rock core. This represents the pressure difference before and after the pore pressure fluid passes through the artificial core.

[0101] In this application, in addition to simulating the coupled environment of axial pressure, confining pressure, pore pressure, temperature, and chemical behavior experienced during the diagenesis of real rocks, the molding cylinder is divided into multiple molding spaces by a liner. Mixtures can be configured separately in the molding spaces according to the anisotropy of the formation. The mineral composition ratio and grain size distribution of each mixture are different. Pore pressure fluid can be introduced into the artificial core in each molding space. Therefore, it can also simulate anisotropy and reservoir heterogeneity. Thus, it is applicable to a variety of rock types. It can not only prepare anisotropic large-size artificial cores, but also simulate the mineral and oil and gas evolution processes of uranium-bearing sandstone, shale, carbonate rocks, and source rocks under different temperatures and pressures, and provide sample analysis.

[0102] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An anisotropic large-size artificial rock core preparation device, characterized in that, include: The molding system provides a core molding environment and includes a triaxial loading device. The triaxial loading device includes a closed reaction chamber and a molding cylinder for holding multiple artificial cores. The reaction chamber has a bottom pad at the bottom, side pads around the inside, and a loading rod that extends into the sealed upper end. The upper end of the loading rod is a loading head. The loading rod and the bottom pad are respectively provided with an input channel and an output channel for pore pressure fluid. The bottom pad and the reaction chamber are respectively provided with an input channel and an output channel for confining pressure fluid. The molding cylinder is placed on the bottom pad. The upper and lower ends of the molding cylinder are provided with microporous filter blocks for filtration, and the inside is provided with a liner for separating multiple molding spaces. Each molding space is used to hold different artificial cores. The pore pressure fluid input channel corresponds one-to-one with each molding space. Axial compression loading system is used to apply pressure to all artificial rock cores in the forming cylinder through a loading head to simulate the axial compression of the rock core formation; The confining pressure loading system is used to pressurize and deliver confining pressure fluid into the reaction chamber through the confining pressure fluid input channel to simulate the confining pressure of the core formation; The pore pressure loading system is used to pressurize and deliver pore pressure fluid to the artificial rock core in each molding space through each pore pressure fluid input channel to simulate the pore pressure of the rock core formation. A heating system is used to heat the reaction chamber to simulate the temperature of the core formation; A collection and metering system is used to collect the pore pressure fluid discharged from the pore pressure fluid output channel and to separately meter the gas phase and the liquid phase; The data acquisition system can collect axial pressure, confining pressure, pore pressure, temperature, displacement of the loading head, acoustic emission signals of the artificial rock core, and input and output information of pore pressure fluid during preparation. The control system is used to control the operation of each system based on the data feedback from the data acquisition system to simulate the diagenesis process of natural rocks and record and analyze the data.

2. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The molding system also includes a base, a column, a reaction frame, and a guide rail. The reaction frame is located directly above the base, the column is connected between the base and the reaction frame, the guide rail extends from the outside of the base to the base, and the triaxial loading device is movably fitted on the guide rail. When the triaxial loading device moves to the base, it is in the working position. The reaction frame is used to provide reaction force for the axial compression loading system.

3. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The reaction chamber has an opening at the top and is open at the bottom. The upper and lower sides of the reaction chamber are respectively equipped with an upper seat and a lower seat. The upper seat is placed on the reaction chamber as a ballast. The loading rod passes through the upper seat and then passes through the opening in a seal. The lower end of the reaction chamber is sealed and placed on the lower seat and connected to the lower seat through a retainer. The lower seat closes the lower end of the reaction chamber. The bottom pad is placed on the lower seat and is positioned by a pin. After the lower seat and the bottom pad are positioned, their channels are connected to each other.

4. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The gasket divides the internal space of the molding cylinder into four rectangular molding spaces, each with dimensions of 250mm×250mm×250mm or 500mm×500mm×500mm.

5. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The axial pressure loading system includes a hydraulic jack for applying pressure to the loading head and an axial pressure controller for controlling the hydraulic jack.

6. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The confining pressure loading system includes a confining pressure fluid container for storing confining pressure fluid and a confining pressure tracking pump for pressurizing and delivering the confining pressure fluid in the confining pressure fluid container to the confining pressure fluid input channel.

7. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The pore pressure loading system includes a gas injection module, a liquid injection module, and a mixing pressure vessel. The gas injection module includes a gas container, a first constant-speed constant-pressure pump, and a gas intermediate pressure vessel connected in sequence. An inlet pressure regulating valve and a safety valve are provided on the pipeline between the gas container and the first constant-speed constant-pressure pump. The liquid injection module includes a liquid container, a second constant-speed constant-pressure pump, and a liquid intermediate pressure vessel connected in sequence. The gas intermediate pressure vessel and the liquid intermediate pressure vessel are respectively connected to the mixing pressure vessel, and the mixing pressure vessel is respectively connected to each pore pressure fluid input channel.

8. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The heating system includes an electric heating probe located inside the side pad, an electric heating sleeve fitted outside the reaction chamber, a preheater electrically connected to the electric heating probe and the electric heating sleeve respectively, and a heating controller electrically connected to the preheater. The external wiring of the electric heating probe passes through the external wiring channel on the bottom pad and exits the reaction chamber.

9. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The collection and metering system includes a condenser connected to the pore pressure fluid output channel, a gas-liquid separator connected to the condenser, a dryer connected to the gas outlet of the gas-liquid separator, a gas meter connected to the dryer, and a liquid meter connected to the liquid outlet of the gas-liquid separator.

10. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: The data acquisition system includes a displacement sensor for monitoring the displacement of the loading head, an axial pressure sensor for monitoring the output pressure of the loading head, a confining pressure sensor for monitoring the output confining pressure of the confining pressure loading system, an acoustic emission probe installed inside the loading rod for monitoring the acoustic emission signal of the artificial rock core, and pressure sensors, temperature sensors, and pH sensors installed at the pore pressure fluid input channel and the pore pressure fluid output channel. The acoustic emission probe and each sensor are connected to the control system through a data acquisition instrument.

11. The anisotropic large-size artificial rock core preparation device as described in claim 1, characterized in that: All components that come into contact with the pore pressure fluid during its journey from the storage container to the pore pressure fluid inlet channel and from the pore pressure fluid outlet channel to the collection and metering system are made of corrosion-resistant materials.

12. A method for preparing anisotropic large-size artificial rock cores, characterized in that: Before preparation: Select a certain number of target cores, obtain the formation temperature, stress state, mineral composition, grain size distribution, porosity and permeability range of the target cores under real formation conditions, collect drilling cuttings or natural mineral particles with similar mineral composition to the target cores, crush and screen them according to the mineral composition and grain size distribution of the target cores to prepare the skeleton particles for artificial cores, and dry and dehydrate them; using the skeleton particles, first prepare multiple mixtures according to the anisotropy of the formation, with different mineral composition ratios and grain size distributions in each mixture, mix each mixture first, add artificial binder and mix, then screen, and then compact in layers to obtain multiple preliminary artificial cores, and then place each artificial core into the molding cylinder and form molding spaces separated by a liner, and set microporous filter blocks for filtration at the upper and lower ends of the molding cylinder, so that the molding cylinder is in a closed reaction chamber; During preparation: pressure is applied to all artificial cores in the molding cylinder to simulate the axial pressure of the core formation; confining pressure fluid is pressurized and transported into the reaction chamber to simulate the confining pressure of the core formation; pore pressure fluid is pressurized and transported into each artificial core in the molding space to simulate the pore pressure of the core formation; and the reaction chamber is heated to simulate the temperature of the core formation. During molding, the flow rate of the pore pressure fluid is kept within a certain range, and the axial pressure, confining pressure, and temperature are gradually increased to the target values. The loading rate of the confining pressure and axial pressure is adjusted according to the monitored acoustic emission signal of the artificial core and the calculated permeability value of the artificial core. The discharged pore pressure fluid is collected, and the gas phase and liquid phase are measured separately to analyze the chemical behavior reaction of the artificial core. At the end of molding, the stress-strain curve of the artificial core is obtained by monitoring the axial pressure and the displacement of the axial pressure loading, so that the error between the final artificial core and the target core in permeability, acoustic emission signal, and stress-strain is controlled within 10%.

13. The method for preparing anisotropic large-size artificial rock cores as described in claim 12, characterized in that, When the pore pressure fluid is a single gas or liquid: The formula for calculating the permeability of artificial rock cores is: in, The permeability of an artificial rock core when the pore pressure fluid is a single gas or liquid. The flow rate of the fluid through the pore pressure of the artificial rock core. The viscosity of the pore pressure fluid is... The length of the artificial rock core. The cross-sectional area of ​​the artificial rock core. This represents the pressure difference before and after the pore pressure fluid passes through the artificial core.

14. The method for preparing anisotropic large-size artificial rock cores as described in claim 12, characterized in that, When the pore pressure fluid is a mixture of gas and liquid: Absolute permeability of artificial rock cores for: in, The number of capillaries; The representative length of the artificial rock core, The length of the artificial rock core; For the maximum pore radius, For minimum pore radius, Where is the pore radius; Let be the probability density function of the pore size distribution in the artificial rock core; It is the total pore area on the cross-sectional area of ​​the compacted artificial rock core; T Temperature of the artificial rock core; in, , , , The calculation formula is: in, It refers to the porosity of the artificial rock core; Gas permeability in artificial rock cores and liquid phase permeability They are respectively: in, For the gas saturation of artificial rock cores, The water saturation of the artificial rock core; For the trapezoidal pore ratio, The ratio of straight pores, The proportion of straight pores was determined by nuclear magnetic resonance. T 2. Calculations are performed when the cutoff value is less than 0.6ms; Indicates the average pore radius; , , The calculation formula is: in, For movable water saturation, To bind water saturation; , The calculation formula is: in, For artificial rock core nuclear magnetic resonance T 2. The throat radius corresponding to a cutoff value of 0.6ms; This is the length of the capillary bend. The critical pore radius under centrifugal force corresponding to the initial water saturation in the artificial rock core. The critical pore radius under centrifugal force corresponding to the bound water saturation in the artificial rock core; The thickness of the stagnant water adhering to the capillary; , , , The calculation formula is: in, The average tortuosity; It is the contact angle between the gas and liquid phases; The pressure difference before and after passing through the artificial core; The calculation formula is: 。 15. The method for preparing anisotropic large-size artificial rock cores as described in claim 12, characterized in that: During the molding process, the temperature and acoustic emission signals of the artificial rock core, as well as the temperature, pressure, and pH value of the pore pressure fluid before and after passing through the artificial rock core, are monitored. Combined with the chemical behavior reaction analysis of the artificial rock core, the changes in the microstructure and composition of the artificial rock core at different times are obtained.

16. The method for preparing anisotropic large-size artificial rock cores as described in claim 12, characterized in that: After the artificial core is prepared, the injection of pore pressure fluid is turned off, so that the axial pressure, confining pressure and temperature decrease in a gradient until the temperature returns to room temperature and the pressure returns to atmospheric pressure. Then the confining pressure fluid and pore pressure fluid in the reaction chamber are collected and recovered separately.

Images