In-situ characterization method and system for gas adsorption behavior of shale reservoir micro-nanopore

Abstract

The present application relates to the technical field of testing or analyzing materials by means of determining chemical or physical properties of materials, in particular to an in-situ characterization method and system for shale reservoir micro-nanopore gas adsorption behavior, the method comprising using non-destructive shale samples, introducing gas in a high-pressure high-temperature reaction kettle simulating formation environment, synchronously collecting Raman spectrum and small-angle / ultra-small-angle X-ray scattering data, and realizing in-situ characterization through multi-scale data fusion analysis.The present application realizes in-situ, non-destructive, high-resolution and multi-component dynamic characterization of shale micro-nanopore gas adsorption behavior under real formation conditions, improves the accuracy of reservoir evaluation, and constructs a more accurate physical and chemical model.

Description

Technical Field

[0001] This invention relates to the field of materials technology, which involves testing or analyzing materials by measuring their chemical or physical properties, and particularly to in-situ characterization methods and systems for the adsorption behavior of gases in the micro- and nano-pores of shale reservoirs. Background Technology

[0002] Shale gas, as an important unconventional oil and gas resource, occupies an increasingly important position in the global energy structure. Its storage and extraction efficiency is closely related to the adsorption behavior of gas in the micro- and nano-sized pores of shale reservoirs. Accurately understanding and characterizing the adsorption / desorption processes of gas in these micro-pores is crucial for the accurate evaluation of shale gas resources, reserve prediction, and the formulation of efficient development strategies. However, shale reservoirs are highly heterogeneous and have complex pore structures. The gas occurrence state is affected by various factors such as formation temperature, pressure, and stress conditions, and the gas adsorption behavior in its micro- and nano-sized pores exhibits unique physicochemical characteristics.

[0003] Existing methods for characterizing gas adsorption behavior in shale reservoirs largely rely on drill core samples, employing laboratory techniques (such as low-temperature nitrogen adsorption and high-pressure methane adsorption) under non-in-situ conditions. These methods often require pretreatment of the samples, such as crushing and drying, which may damage or alter the original pore structure and surface chemical properties of the shale, thus introducing characterization errors and failing to accurately reflect the in-situ adsorption state of the underground reservoir. Summary of the Invention

[0004] The inventors discovered through research that traditional laboratory characterization methods are difficult to simulate complex formation stress, temperature, and high-pressure multi-component gas environments, and cannot monitor the microscopic behavior changes of gases in the adsorption-desorption cycle in real time and dynamically. These limitations lead to a large deviation between the adsorption data obtained by existing technologies and the actual formation conditions, which limits the in-depth understanding of the occurrence mechanism of shale gas reservoirs, affects the accuracy of reserve calculations, and the optimization of development plans.

[0005] The purpose of this invention is to provide an in-situ characterization method and system for the gas adsorption behavior in micro- and nano-pores of shale reservoirs, in order to solve the technical problem that existing technologies are unable to achieve in-situ characterization of gas adsorption behavior in micro- and nano-pores, and are unable to obtain information on the dynamic adsorption and desorption processes of gases in the micro-pore structure inside the reservoir under real formation pressure and temperature conditions, resulting in large errors in the assessment of reservoir gas storage capacity and permeability.

[0006] One aspect of the present invention provides an in-situ characterization method for the gas adsorption behavior in micro- and nano-pores of shale reservoirs, comprising:

[0007] Shale samples were obtained and non-destructive pretreatment was performed on the shale samples to obtain shale samples suitable for in-situ characterization.

[0008] Shale samples were placed in a high-pressure, high-temperature reactor, and the temperature and pressure inside the reactor were adjusted to reach the preset formation temperature and pressure.

[0009] The target gas is introduced into the high-pressure, high-temperature reactor through a gas supply and precision control unit. The target gas is a single-component gas or a multi-component mixture.

[0010] Raman spectroscopy data of the adsorbed gas on the surface of the shale sample was obtained by simultaneously scanning the Raman spectrum through the Raman spectroscopy characterization unit, and X-ray scattering data of the shale sample was obtained by simultaneously scanning the X-ray scattering of the shale sample through the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit.

[0011] Raman spectroscopy data were processed to obtain information on the types, amounts, and changes in adsorbed gas molecules; small-angle X-ray scattering (SAXS) / ultra-small-angle X-ray scattering (UXRS) data were processed to obtain information on shale pore structure parameters and changes in adsorbed phase density.

[0012] Based on processed Raman spectroscopy data and processed small-angle X-ray scattering / ultra-small-angle X-ray scattering data, multi-scale data fusion and analysis algorithms were used to characterize the gas adsorption behavior of micro- and nano-scale pores in shale reservoirs in situ, and a physicochemical model of gas adsorption behavior in shale reservoirs was constructed.

[0013] In some embodiments, obtaining shale samples and performing non-destructive pretreatment on the shale samples includes at least:

[0014] The original shale core was cut into disc-shaped samples with a diameter of 10 to 20 millimeters and a thickness of 2 to 5 millimeters using a diamond wire cutter.

[0015] Ultrasonic cleaning and inert gas purging are used to remove surface dust from the samples, without the use of any chemical reagents.

[0016] In some embodiments, adjusting the temperature and pressure inside the high-pressure, high-temperature reactor to reach a preset formation temperature and pressure includes at least:

[0017] The temperature inside the high-pressure, high-temperature reactor is controlled within the range of 25 to 250 degrees Celsius.

[0018] The pressure inside the high-pressure, high-temperature reactor is controlled within the range of 0.1 MPa to 100 MPa.

[0019] In some embodiments, the introduction of the target gas into the high-pressure, high-temperature reactor via a gas supply and precision control unit includes at least:

[0020] The target gas is introduced into the high-pressure high-temperature reactor through multiple high-pressure gas cylinders, high-pressure pressure reducing valves, mass flow controllers, and high-pressure switching valves of the gas supply and precision control unit, wherein the accuracy of the mass flow controller is 0.5% of full scale.

[0021] In some embodiments, the simultaneous Raman spectral scanning of the adsorbed gas on the surface of the shale sample via the Raman spectroscopy characterization unit includes at least:

[0022] The Raman spectrometer was used in the Raman spectroscopy characterization unit to scan the adsorbed gas on the surface of the shale sample using a laser, a confocal microscope, a spectrometer, and a charge-coupled device detector. The laser had a wavelength of 532 nanometers and the spectrometer had a resolution of 0.5 wavenumbers.

[0023] In some embodiments, the simultaneous X-ray scattering scan of shale samples via a small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit includes at least:

[0024] The shale sample is X-ray scattering scanned using the microfocus X-ray source, collimation system, and two-dimensional X-ray detector of the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. The target material of the X-ray source is tungsten, and the pixel size of the X-ray detector is one hundred micrometers.

[0025] In some embodiments, the processing of Raman spectral data to obtain information on the types, amounts, and changes of adsorbed gas molecules includes at least:

[0026] The Raman spectral data are subjected to baseline correction, noise removal, peak identification, and peak area integration.

[0027] The processing of small-angle X-ray scattering / ultra-small-angle X-ray scattering data to obtain information on shale pore structure parameters and adsorbed phase density variations includes:

[0028] Background subtraction, radial averaging, and aperture distribution calculation based on Guinier's law were performed on the small-angle X-ray scattering / ultra-small-angle X-ray scattering data.

[0029] In some embodiments, the in-situ characterization of gas adsorption behavior in micro- and nano-scale pores of shale reservoirs using multi-scale data fusion and analysis algorithms includes at least the following:

[0030] The peak intensity parameters reflecting the amount of adsorbed gas in the Raman spectroscopy data were aligned and normalized with the scattering intensity curves reflecting the pore structure parameters and adsorbed phase density in the small-angle X-ray scattering / ultra-small-angle X-ray scattering data over time.

[0031] Monte Carlo simulation was used to simulate the gas adsorption process in the micro- and nano-pores of shale, and the experimental data were corrected and interpreted based on the simulation results.

[0032] Multiple linear regression was used to establish the mapping relationship between adsorption capacity, pore structure parameters, adsorbed phase density and formation conditions and gas composition.

[0033] Another aspect of the present invention provides an in-situ characterization system for the gas adsorption behavior of micro- and nano-pores in shale reservoirs, comprising:

[0034] High-pressure, high-temperature reactors are used to place shale samples and provide an in-situ environment that simulates formation temperature and pressure.

[0035] A gas supply and precision control unit is connected to the high-pressure high-temperature reactor and is used to precisely introduce the target gas into the high-pressure high-temperature reactor.

[0036] The Raman spectroscopy characterization unit performs in-situ Raman spectroscopy detection on the shale sample through the sapphire optical window of the high-pressure high-temperature reactor to obtain the spectral characteristic information of the adsorbed gas molecules.

[0037] The small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit performs in-situ X-ray scattering detection on the shale sample through the sapphire optical window of the high-pressure high-temperature reactor to obtain information on the shale pore structure and adsorbed phase density changes.

[0038] The data acquisition and processing unit is connected to the Raman spectroscopy characterization unit and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit, and is used to receive and process the Raman spectroscopy data and the small-angle X-ray scattering / ultra-small-angle X-ray scattering data, and to perform data fusion and analysis.

[0039] The system control and human-machine interaction unit is connected to the high-pressure high-temperature reactor, the gas supply and precision control unit, the Raman spectroscopy characterization unit, and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. It is used to realize the coordinated work of each unit, the precise setting of experimental parameters, real-time monitoring, and safety protection.

[0040] In some embodiments, the high-pressure, high-temperature reactor includes:

[0041] It features a vessel body made of high-pressure resistant, high-strength alloy material and a sapphire optical window with high optical transmittance and high pressure resistance.

[0042] It has a built-in heating unit, a temperature sensor and a pressure sensor. The temperature sensor is a type K thermocouple, the pressure sensor is a piezoresistive sensor, the pressure sensor has a measurement range of 0 to 100 MPa and a measurement accuracy of 0.01%.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] This invention involves non-destructive preparation of shale samples and in-situ measurement in a high-pressure, high-temperature reactor. This avoids the alteration of the original pore structure and surface chemical properties of shale by traditional destructive pretreatments (such as crushing, washing, and drying), eliminates the experimental errors introduced by these processes, and makes the characterization results more realistically reflect the actual reservoir conditions.

[0045] This invention combines Raman spectroscopy with small-angle X-ray scattering (SAXS) / ultra-small-angle X-ray scattering (UXRS) for simultaneous data acquisition. Raman spectroscopy directly provides chemical fingerprint information and quantitative adsorption amount of adsorbed gas molecules, while SAXS / UXRS directly provides changes in pore structure parameters and adsorption phase density. This enables direct microscopic observation of the adsorption behavior of gases in micro- and nano-sized pores, overcoming the shortcomings of existing indirect measurement methods that rely on model fitting for inference, providing solid experimental evidence, and enhancing the reliability of the results.

[0046] This invention can precisely control the introduction of single-component or multi-component mixed gas, and identify and quantify the characteristic peaks of different component gases through Raman spectroscopy. At the same time, it uses small-angle X-ray scattering / ultra-small-angle X-ray scattering data to analyze the overall changes of the adsorption phase, thereby effectively studying the competitive adsorption behavior of multi-component mixed gas in shale micro-nano pores and accurately revealing the distribution law and interaction mechanism of different component gases under different pore sizes.

[0047] This invention features high temporal and spatial resolution. By acquiring time-series Raman spectroscopy and X-ray scattering data, it can monitor the adsorption kinetics of gas molecules in micro- and nano-pores in real time. Furthermore, by utilizing confocal microscopy and micro-focus X-ray sources, it can achieve precise detection of specific micro-regions (such as regions with different mineral compositions), thereby distinguishing the influence of different regions on adsorption behavior. This provides detailed dynamic and local information for a deeper understanding of the adsorption mechanism of shale gas. Attached Figure Description

[0048] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of the in-situ characterization method of the present invention;

[0050] Figure 2 This is a schematic diagram of the in-situ characterization system framework of the present invention;

[0051] Figure 3 This is a schematic diagram of the core principle framework of the present invention. Detailed Implementation

[0052] The following will be based on embodiments of the present invention. Figures 1-3 The technical solutions in the embodiments of the present invention will be clearly and completely described together. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0053] Example 1

[0054] Application Overview

[0055] With the increasing importance of shale oil and gas resource development and utilization, accurately assessing the gas adsorption behavior of micro- and nano-scale pores in shale reservoirs is crucial for predicting reservoir gas content, guiding horizontal well fracturing design, and optimizing production strategies. Traditional characterization methods, such as low-temperature nitrogen adsorption, carbon dioxide adsorption, or high-pressure mercury intrusion porosimetry, often require pretreatment of shale samples under ex-situ conditions. This can alter the pore structure of the samples, failing to accurately reflect the in-situ adsorption characteristics of the formation. Furthermore, these methods typically struggle to monitor the entire process of gas molecule diffusion, adsorption, and desorption in micro- and nano-scale pores in real-world reservoir environments under high pressure and high temperature. They also lack the ability to perform precise coupling and correlation analysis between macroscopic adsorption amounts and microscopic pore structure. Existing technologies have significant limitations in simulating complex formation conditions, capturing the dynamics of adsorption behavior, and achieving multi-scale data fusion and analysis. This results in an insufficient understanding of the gas adsorption mechanism in the micro- and nano-scale pores of shale reservoirs, thus limiting the accurate assessment and efficient utilization of shale gas reservoir development potential.

[0056] This invention proposes an in-situ characterization method for gas adsorption behavior in micro- and nano-scale pores of shale reservoirs. By dynamically monitoring the adsorption process of gas in shale micro- and nano-pores under high temperature and high pressure conditions simulating real formation environments, and combining multi-scale pore structure characteristics, a fine characterization of the adsorption mechanism can be achieved.

[0057] The in-situ characterization method for gas adsorption behavior in micro- and nano-scale pores of shale reservoirs of the present invention includes the following steps:

[0058] The goal of obtaining and preprocessing shale samples is to acquire representative shale reservoir samples and perform necessary cleaning and stabilization treatments to ensure the accuracy and reliability of subsequent experimental results.

[0059] Obtaining shale samples specifically involves drilling to retrieve core samples from the target shale reservoir. During drilling, strict control of drilling speed and coolant usage is crucial to minimize disturbance to the core structure. The retrieved core samples should be immediately numbered, sealed, and packaged using a protective gas such as nitrogen to prevent contact with oxygen and moisture in the air, thus preventing gas escape and redox reactions of mineral components. Subsequently, the sealed core samples are transported to the laboratory under constant temperature conditions, such as 4 degrees Celsius, using specialized cryogenic transport equipment. In the laboratory, based on subsequent characterization requirements, the original core is cut into regularly shaped experimental samples, such as cylindrical samples with a diameter of 2.5 cm and a length of 5 cm, or prepared into thin sections for microscopic observation.

[0060] The pretreatment process includes the following steps: First, the cut experimental samples are ultrasonically cleaned to remove drilling mud residue, rock fragments, or contaminants that may have adhered during transportation. The choice of cleaning agent must consider the mineral composition of the shale sample; for example, deionized water or anhydrous ethanol should be used to avoid introducing new impurities or altering the sample's pore structure. After cleaning, the samples are dried, for example, in a vacuum oven at 105°C for 48 hours until the sample mass is constant, ensuring complete removal of internal moisture. The dried samples are then immediately transferred to a vacuum degassing device, for example, at a vacuum environment of 150°C and a pressure below one Pascal, for continuous degassing for 24 hours to thoroughly remove adsorbed air, residual moisture, or other volatile substances from the sample pores, providing a pure initial state for subsequent gas adsorption experiments. Throughout the sample pretreatment process, basic physical parameters such as sample mass, volume, and density are accurately measured and recorded, and the samples are checked regularly to ensure their integrity and representativeness. Any deviation in pretreatment parameters that may alter the sample structure, such as excessively high drying temperatures leading to dehydration and structural damage of clay minerals, must be adjusted immediately.

[0061] Characterization of the micro- and nano-scale pore structure of shale samples, specifically including:

[0062] High-resolution scanning electron microscopy was used to observe the microscopic morphology of the sample surface, obtaining two-dimensional images of the pores to identify their types and shapes, such as lamellar pores, intergranular pores, and cracks, and to estimate their size range. Simultaneously, focused ion beam technology was used to prepare cross-sections, and three-dimensional reconstruction of the internal pore structure was performed using three-dimensional scanning electron microscopy or X-ray micro-CT to obtain detailed information on the pore network, connectivity, and pore throat distribution, such as the pore topology and tortuosity.

[0063] Gas adsorption methods, such as low-temperature nitrogen adsorption and carbon dioxide adsorption, as well as mercury intrusion porosimetry, were used to precisely measure the pore size distribution and specific surface area of ​​the samples. For micropores (pore size less than two nanometers), carbon dioxide adsorption data were used to calculate pore size distribution using theoretical models such as density functional theory (DFT). For mesopores (pore size between two and fifty nanometers), low-temperature nitrogen adsorption data were used to calculate pore size distribution using theoretical models such as the BJH model or nonlocal density functional theory (DFT). For macropores (pore size greater than fifty nanometers), mercury intrusion porosimetry was used to obtain pore volume, pore distribution, and pore connectivity data. In the gas adsorption experiments, relative pressure and temperature needed to be strictly controlled to ensure adsorption equilibrium, and the specific surface area of ​​the samples was calculated using the multi-point BET method.

[0064] Multi-scale integration and correction are performed on pore structure data obtained through different methods. For example, digital image processing techniques are used to extract parameters such as pore area and perimeter from scanning electron microscope images, and combined with CT scan data to construct a three-dimensional pore network model, quantifying the connectivity and geometric complexity of the pores. Pore size distribution data obtained by gas adsorption method is superimposed and fitted with mercury intrusion porosimetry data to obtain a continuous pore size distribution spectrum covering the micrometer to nanometer scale. During the data integration process, the applicability and measurement deviation of different methods need to be strictly calibrated. For example, mercury intrusion porosimetry may cause pore compression deformation under high pressure, requiring elastic correction.

[0065] Based on the aforementioned characterization data, a quantitative set of parameters for the micro- and nano-scale pore structure of shale samples is generated, including but not limited to total pore volume, specific surface area, average pore size, pore connectivity factor, and the volume percentage of different pore size ranges, such as micropores, mesopores, and macropores. These parameters will serve as important inputs for subsequent gas adsorption mechanism analysis. In this step, the data structure may include multidimensional arrays or structures, storing pore size distribution curves, specific surface area values, pore connectivity matrices, and three-dimensional pore model data. All data are accompanied by precise timestamps and sample identifiers to ensure data traceability.

[0066] Establish an in-situ gas adsorption experimental environment simulating shale reservoir conditions, specifically including:

[0067] A high-pressure adsorption reactor was constructed. This reactor is made of high-temperature and high-pressure resistant materials such as stainless steel alloy, and its interior can withstand temperatures up to 200 degrees Celsius and pressures up to 100 MPa. The reactor's interior is designed with a sample chamber for holding pre-treated shale samples, ensuring sample stability during the experiment. The reactor is equipped with a precision heating belt and a cooling circulation system. A PID controller enables precise temperature control within the reactor, with temperature fluctuations controlled within ±0.1 degree Celsius, simulating geological environments ranging from room temperature to high temperatures.

[0068] It is equipped with a high-precision pressure control system and a gas supply and mixing system. The pressure control system includes high-pressure gas cylinders, high-precision pressure sensors such as piezoresistive sensors with a range of 0 to 100 MPa and an accuracy of 0.05, high-pressure precision metering pumps, and automatic back pressure valves, which can accurately load, maintain, and unload the gas pressure in the adsorption vessel, and the pressure fluctuation range can be controlled within ±0.01 MPa.

[0069] The gas supply system achieves precise proportions of experimental gases, such as methane, ethane, carbon dioxide, and nitrogen, through a multi-channel gas mixing device. The purity of each component must reach at least 99.999%. The gas mixing ratio is controlled by a mass flow controller to ensure that the gas composition matches the target reservoir gas composition, with an error not exceeding 0.5%.

[0070] Example 2

[0071] Based on the same inventive concept as the in-situ characterization method for gas adsorption behavior in shale reservoir micro-nano pores in Example 1 above, this invention also provides an in-situ characterization system for gas adsorption behavior in shale reservoir micro-nano pores, comprising:

[0072] High-pressure high-temperature reactor is used to place shale samples and provide an in-situ environment that simulates formation temperature and pressure. The high-pressure high-temperature reactor has a vessel body made of high-pressure resistant and high-strength alloy material and a sapphire optical window with high optical transmittance and high pressure resistance.

[0073] The gas supply and precision control unit is connected to the high-pressure high-temperature reactor and is used to accurately introduce single-component gas or multi-component mixed gas into the high-pressure high-temperature reactor. The gas supply and precision control unit includes multiple high-pressure gas cylinders, a high-pressure pressure reducing valve, a mass flow controller, and a high-pressure switching valve.

[0074] The Raman spectroscopy characterization unit performs in-situ Raman spectroscopy detection on shale samples through the sapphire optical window of the high-pressure, high-temperature reactor to obtain spectral characteristic information of adsorbed gas molecules. The Raman spectroscopy characterization unit includes a laser, a confocal microscope, a spectrometer, and a charge-coupled device detector.

[0075] The small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit performs in-situ X-ray scattering detection on shale samples through the sapphire optical window of a high-pressure, high-temperature reactor to obtain information on shale pore structure and adsorption phase density changes. The small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit includes a microfocus X-ray source, a collimation system, and a two-dimensional X-ray detector.

[0076] The data acquisition and processing unit is connected to the Raman spectroscopy characterization unit and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit, and is used to receive and process Raman spectral data and the small-angle X-ray scattering / ultra-small-angle X-ray scattering data. The data acquisition and processing unit includes a spectral data processing module, a scattering data processing module and a time series analysis module.

[0077] The system control and human-machine interaction unit is connected to the high-pressure high-temperature reactor, the gas supply and precision control unit, the Raman spectroscopy characterization unit, and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. It is used to realize the collaborative work of each unit, the precise setting of experimental parameters, real-time monitoring, and safety protection. The system control and human-machine interaction unit includes a main control computer and a programmable logic controller.

[0078] Furthermore, the high-pressure high-temperature reactor also includes a built-in heating unit, a temperature sensor, and a pressure sensor. The temperature sensor is a type K thermocouple, and the pressure sensor is a piezoresistive sensor. The pressure sensor has a measurement range of 0 to 100 MPa and a measurement accuracy of 0.01%.

[0079] As one embodiment of the present invention, the vessel body of the high-pressure high-temperature reactor is made of Hastelloy or Inco nickel alloy, and its design pressure bearing capacity is not less than 150 MPa and its design temperature bearing capacity is not less than 300 degrees Celsius.

[0080] As one embodiment of the present invention, the mass flow controller has a range of 0 to 100 standard milliliters per minute, an accuracy of 0.5% of full scale, and a response time of less than one second.

[0081] As one embodiment of the present invention, the laser is a wavelength-tunable semiconductor laser with an output power of 50 milliwatts to 500 milliwatts, the confocal microscope has a magnification of 100x to 200x, and the grating line density of the spectrometer is 1,800 lines per millimeter or 2,400 lines per millimeter.

[0082] As one embodiment of the present invention, the focal spot size of the microfocus X-ray source is less than fifty micrometers, the collimation system includes multiple microapertures, and the dynamic range of the two-dimensional X-ray detector reaches more than one to ten thousand.

[0083] As one embodiment of the present invention, the data acquisition and processing unit further includes a visualization module and a model building module. The spectral data processing module is used to perform baseline correction, smoothing, deconvolution, and peak area or peak height integration of Raman spectral data. The scattering data processing module is used to perform background subtraction, radial averaging, and aperture distribution calculation of small-angle X-ray scattering / ultra-small-angle X-ray scattering data.

[0084] As one embodiment of the present invention, the main control computer of the system control and human-computer interaction unit runs experimental process management software, parameter setting software, safety monitoring software and data storage management software.

[0085] The specific example of the in-situ characterization method for gas adsorption behavior in shale reservoir micro-nano pores in the aforementioned Example 1 is also applicable to the in-situ characterization system for gas adsorption behavior in shale reservoir micro-nano pores in this embodiment. Through the detailed description of the in-situ characterization method for gas adsorption behavior in shale reservoir micro-nano pores above, those skilled in the art can clearly understand the in-situ characterization system for gas adsorption behavior in shale reservoir micro-nano pores in this embodiment. Therefore, for the sake of brevity, it will not be described in detail here.

[0086] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0087] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An in-situ characterization method for gas adsorption behavior in micro- and nano-pores of shale reservoirs, characterized in that, include: Shale samples were obtained and non-destructive pretreatment was performed on the shale samples to obtain shale samples suitable for in-situ characterization. Shale samples were placed in a high-pressure, high-temperature reactor, and the temperature and pressure inside the reactor were adjusted to reach the preset formation temperature and pressure. The target gas is introduced into the high-pressure, high-temperature reactor through a gas supply and precision control unit. The target gas is a single-component gas or a multi-component mixture. Raman spectroscopy data of the adsorbed gas on the surface of the shale sample was obtained by simultaneously scanning the Raman spectrum through the Raman spectroscopy characterization unit, and X-ray scattering data of the shale sample was obtained by simultaneously scanning the X-ray scattering of the shale sample through the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. The Raman spectroscopy data is processed to obtain information on the types, adsorption amounts, and changes of adsorbed gas molecules. Processing small-angle X-ray scattering / ultra-small-angle X-ray scattering data to obtain information on shale pore structure parameters and adsorbed phase density variations; Based on the processed Raman spectroscopy data and processed small-angle X-ray scattering / ultra-small-angle X-ray scattering data, the gas adsorption behavior of micro- and nano-scale pores in shale reservoirs was characterized in situ using multi-scale data fusion and analysis algorithms, and a physicochemical model of gas adsorption behavior in shale reservoirs was constructed. The method of using multi-scale data fusion and analysis algorithms to perform in-situ characterization of gas adsorption behavior in micro- and nano-scale pores of shale reservoirs includes at least the following: The peak intensity parameters reflecting the amount of adsorbed gas in the Raman spectroscopy data were aligned and normalized with the scattering intensity curves reflecting the pore structure parameters and adsorbed phase density in the small-angle X-ray scattering / ultra-small-angle X-ray scattering data over time. Monte Carlo simulation was used to simulate the gas adsorption process in the micro- and nano-pores of shale, and the experimental data were corrected and interpreted based on the simulation results. Multiple linear regression was used to establish the mapping relationship between adsorption capacity, pore structure parameters, adsorbed phase density and formation conditions and gas composition.

2. The method according to claim 1, characterized in that, The acquisition of shale samples and the non-destructive pretreatment of the shale samples include at least: The original shale core was cut into disc-shaped samples with a diameter of 10 to 20 millimeters and a thickness of 2 to 5 millimeters using a diamond wire cutter. Ultrasonic cleaning and inert gas purging are used to remove surface dust from the samples, without the use of any chemical reagents.

3. The method according to claim 1, characterized in that, The method of adjusting the temperature and pressure inside the high-pressure, high-temperature reactor to achieve the preset formation temperature and pressure includes at least the following: The temperature inside the high-pressure, high-temperature reactor is controlled within the range of 25 to 250 degrees Celsius. The pressure inside the high-pressure, high-temperature reactor is controlled within the range of 0.1 MPa to 100 MPa.

4. The method according to claim 1, characterized in that, The process of introducing the target gas into the high-pressure, high-temperature reactor via a gas supply and precision control unit includes at least: The target gas is introduced into the high-pressure high-temperature reactor through multiple high-pressure gas cylinders, high-pressure pressure reducing valves, mass flow controllers, and high-pressure switching valves of the gas supply and precision control unit, wherein the accuracy of the mass flow controller is 0.5% of full scale.

5. The method according to claim 1, characterized in that, The simultaneous Raman spectral scanning of the adsorbed gas on the surface of the shale sample via the Raman spectroscopy characterization unit includes at least: The Raman spectrometer was used in the Raman spectroscopy characterization unit to scan the adsorbed gas on the surface of the shale sample using a laser, a confocal microscope, a spectrometer, and a charge-coupled device detector. The laser had a wavelength of 532 nanometers and the spectrometer had a resolution of 0.5 wavenumbers.

6. The method according to claim 1, characterized in that, The simultaneous X-ray scattering scan of shale samples via a small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit includes at least: The shale sample is X-ray scattering scanned using the microfocus X-ray source, collimation system, and two-dimensional X-ray detector of the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. The target material of the X-ray source is tungsten, and the pixel size of the X-ray detector is one hundred micrometers.

7. The method according to claim 1, characterized in that, The processing of Raman spectral data to obtain information on the types, amounts, and changes in adsorbed gas molecules includes at least: The Raman spectral data are subjected to baseline correction, noise removal, peak identification, and peak area integration. The processing of small-angle X-ray scattering / ultra-small-angle X-ray scattering data to obtain information on shale pore structure parameters and adsorbed phase density variations includes: Background subtraction, radial averaging, and aperture distribution calculation based on Guinier's law were performed on the small-angle X-ray scattering / ultra-small-angle X-ray scattering data.

8. An in-situ characterization system for gas adsorption behavior in micro- and nano-pores of shale reservoirs, characterized in that, include: High-pressure, high-temperature reactors are used to place shale samples and provide an in-situ environment that simulates formation temperature and pressure. A gas supply and precision control unit is connected to the high-pressure high-temperature reactor and is used to precisely introduce the target gas into the high-pressure high-temperature reactor. The Raman spectroscopy characterization unit performs in-situ Raman spectroscopy detection on the shale sample through the sapphire optical window of the high-pressure high-temperature reactor to obtain the spectral characteristic information of the adsorbed gas molecules. The small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit performs in-situ X-ray scattering detection on the shale sample through the sapphire optical window of the high-pressure high-temperature reactor to obtain information on the shale pore structure and adsorbed phase density changes. The data acquisition and processing unit, connected to the Raman spectroscopy characterization unit and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit, is used to receive and process Raman spectral data and the small-angle X-ray scattering / ultra-small-angle X-ray scattering data, and to perform data fusion and analysis. Specifically, the peak intensity parameters reflecting the amount of adsorbed gas in the Raman spectral data are aligned and normalized with the scattering intensity curves reflecting pore structure parameters and adsorbed phase density in the small-angle X-ray scattering / ultra-small-angle X-ray scattering data over time. Monte Carlo simulation is used to simulate the gas adsorption process within the micro- and nano-pores of shale, and the experimental data are corrected and interpreted based on the simulation results. Multiple linear regression is used to establish the mapping relationship between adsorption amount, pore structure parameters, adsorbed phase density, formation conditions, and gas composition. The system control and human-machine interaction unit is connected to the high-pressure high-temperature reactor, the gas supply and precision control unit, the Raman spectroscopy characterization unit, and the small-angle X-ray scattering / ultra-small-angle X-ray scattering characterization unit. It is used to realize the coordinated work of each unit, the precise setting of experimental parameters, real-time monitoring, and safety protection.

9. The system according to claim 8, characterized in that, The high-pressure, high-temperature reactor includes: It features a vessel body made of high-pressure resistant, high-strength alloy material and a sapphire optical window with high optical transmittance and high pressure resistance. It has a built-in heating unit, a temperature sensor and a pressure sensor. The temperature sensor is a type K thermocouple, the pressure sensor is a piezoresistive sensor, the pressure sensor has a measurement range of 0 to 100 MPa and a measurement accuracy of 0.01%.

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