Low-temperature Carbon Dioxide Research Articles

Comprehensive Characterization and Metamorphic Control Analysis of Full Apertures in Different Coal Ranks within Deep Coal Seams

The pore fracture structure of deep coal reservoirs is crucial for evaluating the potential of deep coalbed methane resources, conducting exploration and development, and controlling coal mine gas disasters. Mercury intrusion porosimetry, the liquid nitrogen method, and the low-temperature carbon dioxide adsorption method were used to study the full pore size structure and pore fractal characteristics of different coal grades in deep coal and comprehensively characterize the pore structure of kilometer-level coal mining. The sponge, Frenkel–Halsey–Hill (FHH), and density function models were applied to comprehensively analyze the pore complexity of coal, and the influence of metamorphic degree on pore size structure was evaluated. The distribution relationship of pore volume in different stages of coal samples was macropore→mesopore→micropore, and macropores had the best connectivity. Micropores and mesopores had the largest specific surface area, and the development of micropores and microcracks controlled the deep gas adsorption performance. The micropore volume and specific surface area both revealed a nonlinear decreasing trend with the increase in volatile matter, and coal metamorphism promoted the development of micropores. The pore volume and specific surface area of mesopores and macropores decreased first and then increased in a “U” shape with increasing volatile matter. In contrast, the fractal dimension D1 revealed an inverted U shape with increasing volatile matter, followed by a decrease. The D2 value decreased nonlinearly with increasing volatile matter, whereas the D3 value increased nonlinearly with increasing volatile matter. The degree of metamorphism increased, and the microporous structure became more regular.

Identification of genes used by Escherichia coli to mitigate climatic stress conditions

IntroductionIncreasing temperature and elevated atmospheric carbon dioxide levels could impact the survival of stress-adapted bacteria. Method and resultsIn this study, RNA sequencing was performed to quantify Escherichia coli BL21 (DE3) gene expression in culture media under environmental temperature (27 °C and 42 °C) and carbon dioxide (0.2 % and 6 % v/v) conditions. Differential gene expression analysis between low temperature and different carbon dioxide conditions revealed up-regulated genes such as ldtC and bioA, optimising cell wall integrity and nutrient uptake. While, the downregulation of genes such as malK suggested a metabolic adaptation. Low temperature and high carbon dioxide levels enhanced bacterial tolerance to environmental stress. Under optimal temperatures, Escherichia coli adapts through various metabolic pathways while engaging in different processes at low temperatures and carbon dioxide levels, with temperature having a greater impact on gene expression than carbon dioxide levels. This study shows that complex metabolic activities are activated when both temperatures and carbon dioxide levels are combinsed, affecting antimicrobial resistance, nutrient acquisition, and adaptation strategies. ConclusionEach condition exhibited mechanisms to enhance cellular resilience and adaptation to stress, focusing on cellular integrity, optimising energy utilisation, and activating stress response pathways. Impact statementThe findings stress the importance of continued research to understand the implications of climate change on microbial transcriptomes comprehensively.

Targeted Stimulation of Micropores by CS2 Extraction on Molecular of Coal.

The targeted stimulation of micropores based on the transformation of coal's molecular structure is proposed due to the chemical properties and difficult-to-transform properties of micropores. Carbon disulfide (CS2) extraction is used as a targeted stimulation to reveal the internal evolution mechanism of micropore transformation. The variations of microcrystalline structures and micropores of bituminous coal and anthracite extracted by CS2 were analyzed with X-ray diffraction (XRD), low-temperature carbon dioxide (CO2) adsorption, and molecular simulation. The results show that CS2 extraction, with the broken chain effect, swelling effect, and aromatic ring rearrangement effect, can promote micropore generation of bituminous coal by transforming the microcrystalline structure. Furthermore, CS2 extraction on bituminous coal can decrease the average micropore size and increase the micropore volume and area. The aromatic layer fragmentation effect of CS2 extraction on anthracite, compared to the micropore generation effect of the broken chain effect and swelling effect, can enlarge micropores more remarkably, as it induces an enhancement in the average micropore size and a decline in the micropore volume and area. The research is expected to provide a theoretical basis for establishing reservoir stimulation technology based on CS2 extraction.

Solid Electrolytes for Low-Temperature Carbon Dioxide Valorization: A Review.

One of the most promising approaches to address the global challenge of climate change is electrochemical carbon capture and utilization. Solid electrolytes can play a crucial role in establishing a chemical-free pathway for the electrochemical capture of CO2. Furthermore, they can be applied in electrocatalytic CO2 reduction reactions (CO2RR) to increase carbon utilization, produce high-purity liquid chemicals, and advance hybrid electro-biosystems. This review article begins by covering the fundamentals and processes of electrochemical CO2 capture, emphasizing the advantages of utilizing solid electrolytes. Additionally, it highlights recent advancements in the use of the solid polymer electrolyte or solid electrolyte layer for the CO2RR with multiple functions. The review also explores avenues for future research to fully harness the potential of solid electrolytes, including the integration of CO2 capture and the CO2RR and performance assessment under realistic conditions. Finally, this review discusses future opportunities and challenges, aiming to contribute to the establishment of a green and sustainable society through electrochemical CO2 valorization.

Migration and cooling characteristics of low-temperature gaseous CO2 in high-temperature loose coal

To investigate the extinguishing effect of low-temperature gaseous CO2 on coal spontaneous combustion, a similar simulation experiment was designed and conducted to test its migration and cooling characteristics in high-temperature loose coal. During the injection of low-temperature gaseous CO2, the temperature along the central axis of the release port decreases rapidly. The size of the cooling range and the diffusion rate of the cooling area are inversely proportional to the distance from the center axis and directly proportional to the injection time. The injection time plays a dominant role in the cooling effect of the high temperature coal, followed by the injection position. Gaseous CO2 diffuses inside the loose coal body rapidly, filling the vicinity of the release port within 5s and the container within 30s. The average diffusion velocity of CO2 within the loose coal is 0.051 m/s. The results of this study provide a theoretical basis for the application of low-temperature carbon dioxide to combat coal fire disasters.

Pore heterogeneity analysis and control mechanisms in Cambrian shale of the Shuijingtuo Formation, Yichang area, China

This study focuses on understanding the fractal characteristics and controlling factors of micropore structures within organic-rich shale of the Cambrian Shuijingtuo Formation in the Yichang area of Hubei Province. Mineralogy, petrology, and organogeochemical characteristics were confirmed through comprehensive testing methods, including whole-rock X-ray diffraction and organic geochemical analyses. Additional experiments included low-temperature carbon dioxide adsorption, low-temperature nitrogen adsorption, and high-pressure mercury injection. Fractal dimensions of micropores, mesopores, and macropores were calculated using the V-S, FHH, and MENGER sponge models, respectively. Results indicate that the Cambrian Shuijingtuo Formation represents a typical deposit from an alkaline water body, resulting in high-calcareous shale. Fractal dimensions were as follows: micropores (D1) ranged from 2.1138 to 2.3475 (average 2.2342), mesopores (D2) ranged from 2.5327 to 2.7162 (average 2.6171), and macropores (D3) ranged from 2.7361 to 2.9316 (average 2.82905). Correlations were observed between total organic carbon (TOC) content and Ro with D1 and D2 (positive) and D3 (negative). Shale pore volume and specific surface area exhibited positive correlations with D1 and D2 but negative correlations with D3. High bio-deposited silica positively influenced micropore and mesopore development, while clay mineral compaction and dehydration transformations favored macropore development. Carbonate minerals primarily contributed to regular macropores, with complex correlations involving fractal dimensions D1, D2, and D3. The research results provide theoretical support for analyzing pore fractal characteristics of shallow old Marine shale reservoirs and the prediction and development plan of high-quality reservoirs of the Shuijingtuo Formation in the Yichang area.

Mechanical integrity of tubular elements based on strength and fracture criteria during transient CO2 injection

Geological carbon sequestration (GCS) is an essential technology for reducing carbon emissions. Wellbore integrity is crucial to ensure the safety of GCS. During low-temperature carbon dioxide (CO2) injection, the wellbore temperature decreases, causing the tubing and casing to contract, resulting in considerable axial tensile stresses, and making mechanical failure likely. This paper establishes a transient flow model for CO2 injection to predict the temperature and pressure distribution in the wellbore. Then, the strength safety factor of the tubing and casing is calculated using the material strength criteria. Fracture mechanics theory is employed to analyze the risk of crack propagation in defective tubing or casing during CO2 injection. The study indicates that the wellbore temperature near the wellhead is lower as CO2 is injected. Under typical injection conditions, the tubing and casing have high strength safety factors but small crack propagation factors. The stress intensity factor of cracks on the tubing and casing's outer surface is more significant than inner surface defects, posing a higher risk of crack propagation. When the tubing or casing exits a penetrating crack, its propagation safety factor is less than 1, necessitating the avoidance of through-wall cracks. The results guide maintaining wellbore integrity in carbon dioxide geological sequestration engineering.

Interstellar formation of glyceric acid [HOCH2CH(OH)COOH]-The simplest sugar acid.

Glyceric acid [HOCH2CH(OH)COOH]-the simplest sugar acid-represents a key molecule in biochemical processes vital for metabolism in living organisms such as glycolysis. Although critically linked to the origins of life and identified in carbonaceous meteorites with abundances comparable to amino acids, the underlying mechanisms of its formation have remained elusive. Here, we report the very first abiotic synthesis of racemic glyceric acid via the barrierless radical-radical reaction of the hydroxycarbonyl radical (HOĊO) with 1,2-dihydroxyethyl (HOĊHCH2OH) radical in low-temperature carbon dioxide (CO2) and ethylene glycol (HOCH2CH2OH) ices. Using isomer-selective vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry, glyceric acid was identified in the gas phase based on the adiabatic ionization energies and isotopic substitution studies. This work reveals the key reaction pathways for glyceric acid synthesis through nonequilibrium reactions from ubiquitous precursor molecules, advancing our fundamental knowledge of the formation pathways of key biorelevant organics-sugar acids-in deep space.

Micropore Structure of Deep Shales from the Wufeng–Longmaxi Formations, Southern Sichuan Basin, China: Insight into the Vertical Heterogeneity and Controlling Factors

The microscopic pore throat structure of shale reservoir rocks directly affects the reservoir seepage capacity. The occurrence and flow channels of shale gas are mainly micron–nanometer pore throats. Therefore, to clarify the microstructural characteristics and influencing factors of the deep organic-rich shales, a study is conducted on the marine shale from the Upper Silurian to Lower Ordovician Wufeng–Longmaxi Formation in the southern Sichuan Basin. Petrographic lithofacies division is carried out in combination with petro-mineralogical characteristics, and a high-resolution scanning electron microscope, low-temperature nitrogen and low-temperature carbon dioxide adsorption, and micron-computed tomography are used to characterize the mineral composition and pore structure qualitatively and quantitatively, upon which the influencing factors of the microstructure are further analyzed. The results show that with the increase in burial depth, the total organic carbon content and siliceous mineral content decrease in the Wufeng formation to Long-11 subsection deep shale, while clay mineral content increases, which corresponds to the change in sedimentary environment from anoxic to oxidizing environment. Unexpectedly, the total pore volume of deep shale does not decrease with the increase in burial depth but increases first and then decreases. Using total organic carbon (TOC), siliceous mineral content showed a good correlation with total pore volume and specific surface area, with correlation coefficients greater than 0.7, confirming the predominant role of these two factors in controlling the pore structure of deep shales. This is mainly because the Longmaxi shale is already in the late diagenetic stage, and organic matter pores are generated in large quantities. Clay minerals have a negative correlation with the total pore volume of shale, and the correlation coefficient is 0.7591. It could be that clay minerals are much more flexible and are easily deformed to block the pores under compaction. In addition, the longitudinal heterogeneity of the deep shale reservoir structure in southern Sichuan is also controlled by the thermal effect of the Emei mantle plume on hydrocarbon generation of organic matter and the development of natural microfractures promoted by multistage tectonic movement. Overall, the complex microstructure in the deep shales of the Longmaxi Formation in the southern Sichuan Basin is jointly controlled by multiple effects, and the results of this research provide strong support for the benefit development of deep shale gas in southern Sichuan Basin.

How the Choice of Electrolyte Affects the Carbon Efficiency in Electrochemical CO2 Reduction at Silver Gas Diffusion Electrodes

Reducing CO2 emissions by replacing fossil fuels with renewable energy sources is an important step in the context of climate change. Electrochemical CO2 reduction is a promising technology for supporting this shift, since it provides the possibility to store electrical energy in form of high value chemicals while consuming CO2. It is now generally accepted that the use of gas diffusion electrodes (GDEs) is beneficial due to the limited solubility of CO2 in water [1].To achieve a better understanding of the complex processes taking place in the electrode, the description by a mathematical model is desirable. We present a TFFA (thin-film flooded agglomerate) model for silver GDEs based on the approach presented by Franzen et al. [2] for the oxygen reduction reaction. The model describes the processes in the GDE, including reaction, diffusion, and migration. Therefore, the model provides an in-depth view on the local reaction environment in the electrode, which becomes highly alkaline at elevated current densities due to the formation of hydroxide ions by the electrochemical reactions [3]. This causes the rate of bicarbonate/carbonate formation to exceed the rate of electrochemical CO2 reduction, resulting in a limited carbon efficiency [4]. Using acidic electrolytes might significantly reduce this limitation by decreasing the local alkalinity. This has already been experimentally demonstrated for gold electrodes using electrolytes with pH values in the range of 2-4 [5]. In this study, we present experimental results for silver GDEs using acidic electrolytes. These results show that the carbon efficiency can be increased while maintaining a similar Faradaic efficiency as obtained for KHCO3 electrolytes at industrially relevant current densities. Our model calculations support these findings and give insights about the development of the local pH in dependence of the applied current density for different pH values of the bulk electrolyte.[1] T. Burdyny, W. A. Smith, CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions, Energy & Environmental Science 12 (5) (2019), 1442-1453.[2] D. Franzen, M. C. Paulisch, B. Ellendorff, I. Manke, T. Turek, Spatially resolved model of oxygen reduction reaction in silver-based porous gas-diffusion electrodes based on operando measurements, Electrochimica Acta 375 (2021), 137976.[3] M. Löffelholz, J. Osiewacz, A. Lüken, K. Perrey, A. Bulan, T. Turek, Modeling electrochemical CO2 reduction at silver gas diffusion electrodes using a TFFA approach. Chemical Engineering Journal 435(2) (2022), 134920.[4] J. A. Rabinowitz, M.W. Kanan, The future of low-temperature carbon dioxide electrolysis depends on solving one basic problem. Nature Communications 11 (2020), 5231.[5] M.C.O. Monteiro, M.F. Philips, K.J.P. Schouten et al., Efficiency and selectivity of CO2 reduction to CO on gold gas diffusion electrodes in acidic media. Nature Communication 12 (2021), 4943. Figure 1

Experimental study on the effect of magma intrusion and temperature on the pore structure of coal

The rich and intricate pore structure that coal possesses has a big impact on CBM engineering. We characterized the pore structure of coal samples at various distances from the magma intrusion point and at various temperatures using MIP, low-temperature nitrogen adsorption, and low-temperature carbon dioxide adsorption to study the thermal effect of temperature and magma intrusion on the pore structure of coal seams to better understand the properties of coal affected by temperature and thermal effect of magma. The results of the study prove that there are similar and different pore structures of coal samples at different distances from the magma intrusion point and at different temperatures. Heating and magma thermal effects have similar effects on coal samples in macroporous and micropore stages. The pore volume of coal samples increased with increased temperature or magma intrusion effect in the macroporous stage but decreased with increased temperature or magma intrusion effect in the microporous stage, with the magma thermal effect being more pronounced. While in the medium pore stage, the pore volume of coal samples increases and then decreases with the enhancement of magmatic intrusion influence, but the trend of decreasing development with the increase of temperature. This result makes a theoretical contribution to the selection of coal-bed methane utilization technology in the magmatic rock-influenced region.

CO2 electroreduction to multicarbon products from carbonate capture liquid

CO2 electroreduction to multicarbon products from carbonate capture liquid

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Numerical Investigation on the Influence of Operation Mode of the Air-Conditioning and Oxygen Supply System on Energy Consumption of Plateau Train

Problems of low temperature, low pressure, low oxygen, and high carbon dioxide (CO2) concentration in the air-conditioning (AC) trains of the Qinghai-Tibet railway can affect the health and comfort of passengers and cause altitude sickness. When the Qinghai-Tibet railway train runs in high-altitude areas, it is necessary to supply oxygen and introduce fresh air to meet the limited oxygen (O2) and CO2 partial pressures (PPs) in the carriage. In this study, a numerical analysis of the correlation between the CO2 PP and O2 PP in AC trains and the air supply parameters (ASPs), fresh air volume (FAV), and oxygen supply volume (OSV) along the Qinghai-Tibet line in summer was conducted. The results show that the influence of the FAV on the energy consumption of the air-conditioning system (ACS) in different running areas is inconsistent, whereas the influence of the oxygen supply system (OSS) on energy consumption is significant. During the oxygen supply period, the FAV had the opposite effect on energy consumption of ACS and OSS. The energy consumption of the OSS was approximately five times that of the ACS. By studying the correlation between the internal environment and ASP of trains running in different regions, the operation modes of ACS and OSS can be reasonably set, which can effectively reduce energy consumption by 20–50%.

Research on cutting parameters of low-temperature liquid CO2 assisted PCD tool turning bearing ring

The polycrystalline diamond (PCD) tool will produce severe wear when cutting the bearing ring which is a ferrous metal material. In order to reduce the wear of the PCD tool and achieve higher quality bearing ring machining, the cutting parameters of turning bearing ring with low-temperature liquid carbon dioxide (CO2) assisted PCD tool was studied. In this paper, experiments were carried out based on the completed cryogenic cooling system. The experimental results show that the reference cutting temperature increases with the increase of feed rate and cutting speed. The optimal parameters extend the tool life by 2.5 times and make the cutting temperature more stable. The change in cutting speed has a more noticeable impact on the reference cutting temperature than the feed rate. The surface roughness of the workpiece increases with the increase in feed rate and cutting speed. The optimal parameters of feed rate and cutting speed reduce the surface roughness of the workpiece by 81.5 % and 45.8 %, respectively. The primary wear forms of the PCD tool are graphitization, diffusion wear, adhesion wear and tool edge breaking. The tool wear increases with the increase of feed rate and cutting speed. The optimal parameters of feed rate and cutting speed reduce flank wear of the PCD tool by 42.7 % and 47.8 %, respectively. Moreover, the technological parameters of feed rate and cutting speed are presented for reference in actual machining.

Water vapor sorption properties on coals affected by hydrophilic inorganic minerals and pore fissures

It is essential to understand the law by which coal adsorbs water to prevent coal and rock disasters in the mining process. However, the hydration of coal containing inorganic minerals is seldom studied. In this study, X-ray diffraction (XRD), low-pressure nitrogen adsorption (LPNA), and low-temperature carbon dioxide adsorption (TCA) experiments were performed on coal samples to obtain inorganic mineral compositions and pore structure characteristics. Then, vacuum vapor sorption analyzer (VVS) experiments were carried out on coal samples. GAB and Freundlich models were used to classify the strong adsorption region, weak adsorption region, and critical humidity for monolayer adsorption. The relationship between the amount of adsorbed water and the coal's pore structure and surface chemical properties was discussed. Then, the reason for the difference in specific surface area between N2 and H2O adsorbents was elucidated. Finally, we discuss the significance of coal-water adsorption by pyrite and clay minerals in preventing coal and dynamic rock disasters.

Low-temperature supercritical activation enables high-performance detection of cell-free DNA by all-carbon-nanotube transistor

Biosensors based on carbon nanotube (CNT) thin-film transistors (TFTs) have drawn intense interests for their exhibiting great potential in ultrasensitive and label-free DNA detection. However, the inevitable defects in the dielectric and channel of CNT-based TFTs may induce noisy or unreliable output signals. Here, we propose a low-temperature supercritical carbon dioxide (SCCO2) fluid activation method to enhance the performance of transistor-based biosensors. An activation model of SCCO2 treatment is proposed to elaborate that the SCCO2 treatment can repair the dangling bonds of SiO2 dielectric facilely and passivate the hydroxyl groups effectively. Furthermore, a cell-free DNA detection platform is built up based on all-carbon-nanotube TFTs (AC-TFTs) modified by the CW-Peptide probe. By adopting the SCCO2 treatment, the response of AC-TFT biosensors to AKT2 gene related to triple-metastatic negative breast cancer can be enhanced by more than 114% with high uniformity, and a broad detection range of six orders of magnitude is yielded with a theoretical limit of detection of 42 fM. Additionally, the response has a linear correlation with the length of DNA targets. The nondestructive and eco-friendly SCCO2 activation method provides a promising and universal strategy for achieving highly accurate and sensitive transistor-based biosensors in future clinical applications.

Mathematical modeling of oxygen levels in a controlled atmosphere store for preservation of apple fruits

Apple fruit preservation for long periods (up to eight months) needs low temperature, high humidity, low oxygen and high carbon di-oxide levels around the fruits. Controlled Atmosphere (CA) storage chambers can extend the shelf life of fruits by controlling the respiration rates of fruits. To achieve low respiration, low oxygen levels need to be created in the sealed chambers. A pressure swing adsorption nitrogen generator is used to generate 99% pure nitrogen, which is pumped into the sealed fruit chambers after achieving required temperature. Oxygen level of 20.8% is slowly lowered to 1 to 2% level. Storage chamber of 720 m3 is selected to conduct the kinetic study of lowering the oxygen level. Quantity of apples stores per batch is 150 metric tons. Time taken to lower the oxygen to required levels is 24 h. Rate of oxygen reduction is modeled mathematically and fitted to three mathematical equations, viz. exponential, second order polynomial and third order polynomial. Exponential model could explain the behavior with R2 value of 0.966. R2 value of 0.978 found for second order polynomial model. Best fit of predicted and experimental values found with polynomial model of third order with R2 value of 0.998. The modeled data will be useful for prediction of oxygen levels for both controlled atmosphere and modified atmosphere requirements for different fruits.

Precise positioning and inert processing of the high-temperature zone in a longwall gob during a mining-stopped period: an application case

ABSTRACT During a mining-stopped period, coal spontaneous combustion (CSC) may occur in a gob area, which not only causes huge economic losses but also poses a serious threat to the mine’s production safety. To address this situation, a working face in the Chinese Silaogou Coal Mine was considered as an example. With a combination of numerical simulation and field temperature measurements, the spatiotemporal distribution of the temperature in a longwall gob was determined, and the area of potential spontaneous combustion was identified. Furthermore, a dry-ice rapid sublimation unit used for underground fire prevention was developed. The device was successfully applied underground to exert the effect of low-temperature carbon dioxide gas to reduce the coal temperature. The results show that the temperature of the mined-out area near the air intake side of the working face is significantly higher than that of the return side, and the longer the stopping time is, the more obvious the temperature difference is. Within 12 hours of using the generator to inject carbon dioxide, the observed temperatures of the two hot spots dropped from 26.1°C and 26.6°C to 19.1°C and 19.8°C, respectively, and the temperatures hardly rebounded after stopping the gas injection, effectively suppressing the heat storage and oxidation of the coal.

Nanopore Size Distribution Heterogeneity of Organic-Rich Shale Reservoirs Using Multifractal Analysis and Its Influence on Porosity–Permeability Variation

The shale nanopore size (diameter [less than] 100 nm) distribution heterogeneity (SNDH) is one of the important factors affecting gas production. However, quantitative analysis of the SNDH and the applicability of single and multifractal models need to be further studied. Here, based on low-temperature liquid nitrogen and carbon dioxide tests of organic-rich shale in Qinshui Basin, multifractal dimension variation of micropores ([less than] 2 nm) and mesopores (2–100 nm) are studied, and the multifractal factors that affect the distribution of nanopores are determined. Additionally, the differences between single fractal and multifractal results are compared. Based on this, dynamic variation of porosity and permeability under the constraints of the nanopore structure is discussed from the perspective of multifractal variation. The results of this study are as follows: (1) The pore size distribution of micropores and meso–macropores in shale samples exhibit typical multifractal behavior. The overall distribution heterogeneity of meso–macropores is mainly affected by the distribution of pores in the low-value area of pore volume (LAPV), while the overall distribution heterogeneity of micropores is affected by the distribution of the high-value area of the pore volume. The multifractal parameters and influencing factors of micropores and meso–macropores are clearly different. (2) The single fractal dimension D2 calculated using the Frenkel–Halsey–Hill model has a negative correlation with the multifractal parameters, implying that the distribution heterogeneity of the LAPV gradually decreases with the increase of the D2 value, indicating that the physical meaning of the two models is obviously different. (3) The pore distribution heterogeneity affects permeability variation and diffusion process of shale reservoir. With the increase of the multifractal dimension of meso–macropores, the damaging effect of stress on permeability is stronger. The more heterogeneous the micropore size distribution, the smaller is the ″modification effect″ of stress on the diffusion coefficient.