Specific Surface Area Pore Research Articles

Novel Aerosol‐Based Approach toward Mesoporous Silica Nanoparticles

This study introduces a novel gas‐phase method for the synthesis of mesoporous silica nanoparticles (MSNs). The method is a two‐step templating approach by first forming silicon‐coated carbon structures in a hybrid microwave‐plasma/hot‐wall reactor followed by an annealing step to produce mesoporous silica with distinct nanostructure and porosity. Two different (sacrificial) carbonaceous templates have been prepared (plasma reactor) and coated (hot‐wall reactor), 2D few‐layer graphene (FLG) flakes and soot‐like fractal aggregates. Results show that the wall thickness of the porous silica structures can be adjusted by changing the concentration of the silicon precursor (monosilane). High monosilane concentrations, however, result in solid silica particles after annealing. Using soot‐like particle templates permitted to control of the shell thickness of the hollow porous particles, while the FLG template results in ultrathin silica sheets after heat treatment. The pore volume and specific surface area increase up to 263 m2 g−1 and 0.6 cm3 g−1, respectively, by the formation of hollow porous particles. An adsorption study on carbamazepine reveals up to ≈86% removal. The gas‐phase aerosol‐based template method presented here offers scalability and versatility, and it is capable of producing MSNs with a controlled structure and porosity by modifying the carbonaceous templates.

Evaluation of Cs-137 Binding by High-Moor Peat in the European North of Russia

The sorption properties of high-moor peat and products of its sequential disassembly were studied and the binding of Cs-137 by the test materials was evaluated. According to the results of low-temperature nitrogen adsorption, the specific surface area of pores in the test materials varied in a range from 1.48 to 5.96 m2/g, and the total pore volume varied from 0.002 to 0.009 cm3/g. The limiting adsorption of Cs-137 on the test high-moor peat ranged from 1 to 51 Bq/g, which significantly exceeded the background values ofCs-137 activity determined in the peat deposit and indicated a high sorption capacity of high-moor peatlands with respect to anthropogenic radionuclides. For peat derivatives obtained by the sequential disassembly method, the values of limiting sorption ranged from 2 to 61 Bq/g in the test range of pH. It was revealed thatthe pH of the medium and the nature of a sorbent are the key factors determining the efficiency of Cs-137 sorption. It was established that the values of the limiting sorption of Cs-137 for peat and products based on it increased with pH

A Coin-Shaped Polypropylene Bio-Carrier Fabricated Using a Filament-Based 3D Printer for Wastewater Treatment

The utilization of the moving bed biofilm reactor (MBBR) has been identified as a promising technology for reducing water pollutants. This study focuses on designing a novel bio-carrier using 3D printing technology for use in an MBBR for wastewater treatment. The bio-carrier is made of polypropylene filament with four variations in specific surface area. The study investigates the relationship between the specific surface area and the amount of adhering biofilm on the bio-carrier. Results show that type-4 bio-carrier with a specific surface area of 1438.16 m2/m3 and a pore diameter of 1.8 mm to 4.9 mm has the highest mass of biofilm attachment at 2.598 grams. This research provides insights for designing bio-carriers with suitable pore diameters and specific surface areas for improved MBBR performance in wastewater treatment.

Preparation of dispersed hollow carbon spheres assisted by silica/carbon shell isolation for supercapacitors

Nitrogen-doped mesoporous hollow carbon spheres are crucial in energy storage and the strategy of converting the inexpensive polymer polyacrylonitrile (PAN) into hollow carbon spheres needs to be improved. In this study, polystyrene/polyacrylonitrile (PSPAN) composite spheres were subjected to silica/carbon shell isolation to prepare nitrogen-doped hollow carbon spheres. In the carbonization process, the pyrolysis of PSPAN lead to the cavity due to the total decomposition behavior of PS. Due to the isolation of silica/carbon shells, the formation of a molten state during the pyrolysis process of PAN can be effectively prevented, thus avoiding the agglomeration of carbon spheres, and obtaining dispersed and regular hollow carbon spheres. The pore structure and specific surface area of the material were adjusted by hydrolyzing tetraethyl orthosilicate on the template surface and introducing dopamine for polymerization after different times. The hollow structure, nitrogen doping characteristics and abundant mesopores endow the NHCS with high performance in supercapacitor.

Microscopic oil occurrence in high-maturity lacustrine shales: Qingshankou Formation, Gulong Sag, Songliao Basin

Occurrence and mobility of shale oil are prerequisites for evaluating shale oil reserves and prioritizing exploration targets, particularly for heterogeneous lacustrine shales. The Qingshankou Formation in the Gulong Sag, Songliao Basin is a classic lacustrine pure shale reservoir that contains abundant shale oil resources. The predicted geological reserves of the shale are 1.268 × 109 t. In this study, field emission scanning electron microscope (FE-SEM), the modular automated processing system (MAPS), pyrolysis-gas chromatography (Py-GC), low-pressure nitrogen gas adsorption (LPNA), Soxhlet extraction, pyrolysis, and 2-D nuclear magnetic resonance (NMR) were integrated to describe the shale oil components, microscopic occurrence, mobility, and the effective pore size distribution. Meanwhile, the related controlling factors are discussed.The shale oil in the Qingshankou Fm exists dominantly in the matrix pores of the clay minerals, with small amounts distributed in the intergranular pores of terrigenous clastic grains, intercrystalline pores of pyrite, intragranular pores of ostracod shells, and micro-fractures. Shale oil is distributed in the pore spaces of variable sizes in different lithofacies. The clay mineral-laminated shales are characterized by the broadest range of pore size and largest volume of pore spaces with shale oil distribution, while the ostracod-laminated shales have limited pore spaces retaining oil. Furthermore, the proposed integrated analysis evaluates the shale oil molecules existing in two states: movable, and adsorbed oil, respectively. The result illustrates that movable oil takes up 30.6%–79.4% of the total residual oil. TOC, mineral composition, and pore structures of the shale joint together to control the states and mobility of the shale oil. TOC values are positively correlated with the quantities of shale oil regardless of the state of oil. The mineral components significantly impact the state of shale oil. Noticeable differences in the states of oil were observed following the changing types of minerals, possibly due to their difference in adsorption capacity and wettability. Clay minerals attract more adsorbed oil than movable oil. Felsic minerals generally decrease the occurrence of total and adsorbed oil. Carbonate plays a positive role in hydrocarbon retention of all the shale oil states. As for the pore structure, the average pore size exerts a critical impact on the total, movable, and adsorbed oil content. The total pore volume and specific surface area of shales play a principal role in controlling the total yields and amounts of adsorbed oil. This research improves the understanding of the occurrence characteristics and enrichment mechanisms of shale oil in terrestrial pure shales and provides a reference for locating favorable shale oil exploration areas.

Characterization, factors, and fractal dimension of pore structure of fly ash-based geopolymers

Fly ash-based geopolymer is a new cementitious material with environmentally friendly characteristics. Generally, the mechanical properties of cementitious materials are influenced by their pore structure. The variation in the pore structural characteristics of the geopolymers with various influencing factors was investigated in this study. A smaller activator modulus and liquid-solid ratio lead to a finer pore structure, while higher activator concentrations also result in a finer pore structure. However, the densification of pore structure does not follow a monotonic relationship with the conserving temperature. Increasing the conserving temperature within a certain range decreases the most probable pore diameter and porosity. Nevertheless, excessive temperature increase has the opposite effect. Furthermore, the fractal dimension was introduced to characterize the pore structure comprehensively. The results show that a lower pore volume, a larger pore-specific surface area, and a smaller most probable pore diameter contribute to increasing pore surface fractal dimension. Further, compared to porosity, the microporous pore surface fractal dimension shows a better linear correlation with compressive strength.

Remediation of pesticides contaminated water using biowastes-derived carbon rich biochar

The competition impact and feedstock type on the removal of water pesticides using biochar have not yet been sufficiently investigated. Therefore, here we investigated the potentiality of three different biochars (BCs) derived from rice husk (RHB), date pit (DPB), and sugarcane bagasse (SBB) biowastes for the simultaneous removal of ten pesticides from water in a competitive adsorption system. The BCs structural characterization and morphology were investigated by XRD, FTIR spectroscopy and SEM analysis. The potential adsorption mechanisms have been investigated using various isothermal and kinetic models. RHB showed the highest removal percentages (61% for atrazine/dimethoate and 97.6% for diuron/chlorfenvinphos) followed by DPB (56% for atrazine/dimethoate and 95.4% for diuron/chlorpyrifos) and then SBB (60.8% for atrazine/dimethoate and 90.8% for chlorpyrifos/malathion). The higher adsorption capacity of RHB and DPB than SBB can be due to their high total pore volume and specific surface area (SSA). Langmuir model described well the sorption data (R2 = 0.99). Adsorption equilibrium was achieved after 60 min for RHB, and 120 min for both DPB and SBB. The optimum adsorbent dose (g/L) was 10 for RHB and 4 for DPB and SBB. The removal efficiency of pesticides was enhanced by decreasing pH from 9 to 5 by RHB and to 3 by DPB and SBB. XRD and FTIR spectroscopy confirmed that BCs contain some active adsorption groups and metal oxides such as MgO, SiO, Al2O3, CaO, and TiO2 that can play an effective role in the pesticides sorption. BET-N2 adsorption analysis demonstrated that the BC pore size contributes significantly to pesticide adsorption. These findings indicate that RHB, DPB, and SBB have ability for adsorption of water pesticides even under acidic conditions. Therefore, the rice husk, date pit, and sugarcane bagasse biowastes could be pyrolyzed and reused as effective and low-cost sorbents for elimination of hazardous substances such as pesticides in the aqueous environments.

A MOF-derived Zn-TiO2 electrochromic supercapacitor

Electrochromic supercapacitors caused widespread concern due to their ability to exhibit color changes to monitor the charging and discharging states. However, the unsatisfactory energy storage and electrochemical durability seriously hinder their practical applications, especially for titanium dioxide (TiO2) electrochromic supercapacitors. To address the above issues, a strategy for designing the novel bi-functional Zn-TiO2 film derived from the metal-organic framework (MOF)-based material is proposed for the first time. The ZnO@zeolitic imidazolate framework-8 (ZIF-8) acts as the self-sacrificial template, beneficial from the diverse porous structure of ZIF-8 and the core-shell structured of ZnO@ZIF-8, the obtained Zn-TiO2 film inherits the large pore volume and specific surface area, facilitating ion/electron intercalation/deintercalation and transport, presenting good electrochemical performance, large specific capacitance, and good constant current charging and discharging stability. In addition, the persistent deintercalation of the embedded Zn2+ in the TiO2 lattice continuously generates new available sites for Li+ intercalation, and the highly porous structure of Zn-TiO2 provides sufficient space to cope with the volume expansion during the electrochemical cycling, leading to the superior durability of the film. Finally, an asymmetric electrochromic supercapacitor using the Zn-TiO2 electrode is constructed and investigated. This study promotes the exploration for designing and fabricating the high-performance electrochromic supercapacitors towards intelligent technology applications.

Mechanism of adsorption capacity enhancement of coal due to interaction with high-pressure scCO2-water system

Coal interaction with high-pressure scCO2-water may change methane adsorption capacity affecting CO2-ECBM efficiency. In the present work, we experimentally investigated mechanism of adsorption capacity enhancement of coal due to interaction with high-pressure scCO2-water system. Experimental pressure and temperature are 9 MPa and 40 °C, respectively, with reaction time 24 h, 72 h, 120 h, and 240 h. Organic structure, pore structure, methane adsorption capacity were measured to characterize scCO2 reaction with coal samples. It's found that high pressure leads to a more significant compaction of micro-pores comparing with meso-, macro or even larger pores or fracture. Pore compaction existed during the whole reaction time (240 h) during which specific surface areas of different coal samples expose to N2–H2O system decreased by 28∼38%. While SSAs (pores with size below 100 nm) of coal samples expose to scCO2-H2O system increased by 26∼70% from 24 h to 240 h after a decrease of 17∼38% at the initial 24 h, which is mainly due to pore expansion and emerged corrosion pores. However, pore filling caused by chemical reaction decreased pore volume and specific surface area. For pores larger than 100 nm, SSAs show an increasing trend expose to both scCO2-H2O system and N2–H2O system. SSAs of coal samples expose to scCO2-H2O system increased by 14∼51% from 0 h to 240 h. While they increased by 19∼36% after expose to N2–H2O system, which indicating that high pressure can also lead to meso- and macro-pore expansion and new hydro-fractures.

Effect of benzoic acid and dopamine hydrochloride as a modulator in the water resistance of Universitetet i Oslo-67: Adsorption performance and mechanism

The severe hazards on ecological environment and human body caused by volatile organic compounds (VOCs) have attracted worldwide substantial attention. In this research, a series of novel modified Universitetet i Oslo-67 (UiO-67) with water resistance were prepared and characterized, which had modified by benzoic acid and dopamine hydrochloride (67-ben-DH). On this basis, the adsorption performance, adsorption kinetics, defect engineering and water resistance of adsorbent were investigated. The results indicated that the excellent pore structure and specific surface area of 67-ben-DH-6 (molar ratio of Zr4+ to DH was 1:6) were retained while the adsorption performance and water resistance of the adsorbent were improved. Due to more defects, excellent adsorption diffusion and strong π-π interactions of 67-ben-DH-6, it performed the maximum adsorption capacity of toluene (793 mg g−1). Furthermore, the outstanding water resistance was attributed to the fact that N element of DH reduced the affinity of the adsorbent with water. Finally, the density functional theory (DFT) calculations showed that the adsorbent 67-ben-DH-6 had the maximum adsorption energy for toluene (-99.4 kJ mol−1) and the minimum adsorption energy for water (-17.8 kJ mol−1). Thus, the potential mechanism of 67-ben-DH for efficient toluene adsorption and water resistance was verified from a microscopic perspective.

Experimental study on the effect of high-temperature nitrogen immersion on the nanoscale pore structure of different lithotypes of coal

This paper presents the heat treatment study on different lithotypes of coal using a custom designed high-temperature thermal nitrogen immersion experimental setup. The results revealed that the heat treatment significantly increased the surface roughness of coal particles and the structural complexity. The pores with diameters >200 nm of coal increased after heat treatment. Some of the new fissures still retain the pore morphology, exhibiting the pore connections. With increasing heat treatment temperature, the total pore volume (TPV) and specific surface area (SSA) of all four selected coal types tended to decrease. Thermal action also significantly increased the average and maximum pore diameters, and the most obvious effect was observed after heat treatment at 120 °C and 210 °C. After heat shock at 210 °C, the average diameters of bright and semibright coal samples were enlarged by 3.5 and 2.7 times, respectively. The semidull coal enlarged 1.6 times, and the dull coal enlarged 1.2 times. In addition, the fractal dimension, which represents the surface roughness of pores, continued decreasing as the heat treatment temperature increases. The pore structure fractal dimension first tends to increase, then decrease, and finally increase again. Therefore, the heat treatment enhanced connectivity and increased fracture, facilitating the transport of methane.

Pore structure characteristics and impact factors of laminated shale oil reservoir in Chang 73 sub-member of Ordos Basin, China

This research paper focuses on the laminated shale oil reservoir in the third sub-member of the seventh member of Yanchang Formation (Chang 73 sub-member) in the Ordos Basin. The study aims to comprehensively analyze the lithofacies type, micro qualitative and quantitative pore structure parameters, and the main controlling factors of the pore structure in laminated shale. The analysis involves various techniques, including a comprehensive analysis of TOC, rock-eval, X-ray diffraction, polarized light and fluorescence microscope observation, field emission scanning electron microscope observation, and low-pressure N2 adsorption analysis. Based on the sedimentation characteristics, geochemistry, and mineral composition differences, the Chang 73 laminated shale can be classified into three lithofacies types: tuffaceous-organic matter binary laminated shale, clayey-organic matter binary laminated shale, and felsic-clayey binary laminated shale. The pore network consists primarily of organic hydrocarbon generation pressurization fractures, clay mineral felsic intergranular composite pores, and felsic plasmid intergranular pore fracture systems. Mesopores are the most developed pore type. The pore volume and specific surface area increase in the order of “tuffaceous-organic matter”, “clayey-organic matter”, and “felsic-clay”, while the heterogeneity of the pore network gradually weakens, and the roughness of the pore surface enhances. The overall development of organic matter pores is limited, with organic matter-pyrite-clay mineral composite pores being the main components of micropores. The primary intergranular pore system, associated with rigid quartz particles, dominates the mesopores and macropores, and acts as the main framework of the entire pore network. The development of feldspar dissolution pores is limited and contributes minimally to the pore network.

Effects of substitution of Mg for Zn IN the composition of layered double aluminum hydroxides on their physico-chemical properties

Samples of Mg–Zn–Al layered double hydroxide (LDH) have been synthesized by solid-phase interaction of Mg, Zn, and Al crystalline hydrates with (NH4)2CO3, and then studied by chemical, X-ray phase analysis, as well as by Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. The paper presents results of studies of structural and surface properties (specific surface area and volume of pores, distribution of pores by their diameter). It was found that an increase in the degree of substitution of Mg by Zn leads to an increase in the specific surface area and the specific volume of samples. At the same time, the distribution of mesopores has a polymodal character with a predominance of pores having dpor = 3–4 and 25–50 nm. It was found that the substitution of Mg for Zn in the composition of layered double hydroxides leads not only to an increase in the specific capacity of the monomolecular layer of LDH, but also to a stronger interaction of adsorbate (nitrogen) with their surface.

Preparation of Microcrystalline Cellulose/N-(2-aminoethyl)-3- Aminopropyl Methyl Dimethoxysilane Composite Aerogel and Adsorption Properties for Formaldehyde.

Air pollution is related to the development of the national economy and people's livelihoods. Formaldehyde, as one of the main pollutants in the air, affects people's physical and mental health. In order to remove formaldehyde and better protect the health of residents, it is necessary to develop efficient adsorption materials. In this study, APMDS-modified cellulose composite aerogel microcrystalline was investigated. The adsorption of formaldehyde by the MCC/APMDS (Microcrystalline Cellulose/N-(2-aminoethyl)-3- Aminopropyl Methyl Dimethoxysilane) composite aerogel mainly relied upon the reaction of the protonated -NH3+ group in APMDS with formaldehyde to form a Schiff base to achieve the effect of deformaldehyde. Meanwhile, the modification of the aerogel reduced the pore volume and specific surface area, and the average pore size increased to 14.56 nm, which enhanced the adsorption capacity of formaldehyde, and the adsorption amount reached 9.52 mg/g. This study provides valuable information for the preparation of adsorbent materials with high formaldehyde adsorption capacity for air purification.

One-pot citric acid/nitrates combustion design of 2D nanosheet mesoporous BiαClβOδ nanostructure: Efficient sunlight photocatalytic elimination of tetracycline-HCl

The development of high-efficiency and stable nano-photocatalysts for environmental pollution control is a rapidly evolving research domain. The fabrication of Z-scheme heterojunctions with exceptional redox abilities has emerged as a promising and effective approach. In this study, the Z-scheme heterojunction sheet-like photocatalyst was created using a one-pot citric acid/nitrates combustion method, consisting of BiαClβOδ. To optimize the photocatalyst's physicochemical properties, the synthesis process was conducted at different fuel to oxidizer ratios (Φ = 0.25, 0.5, 0.75, 1), which is a critical factor in the combustion reaction. Compared to the pristine BiOCl with a photocatalytic efficiency of 65%, heterojunction nanosheets with a Φ ratio of 0.5 exhibited superior performance in completely removing aqueous tetracycline-HCl under simulated solar light irradiation. This boosting performance is mainly due to the improved light harvesting (Eg = 2.52 eV), charge separation and transfer resulting from the Z-scheme structure, as well as the increased pore volume (0.565 cm3/g) and specific surface area (127.9 m2/g) and well-grown sheet-like morphology resulting from the high temperature, heat, and released gases during combustion. These characteristics were confirmed using various analytical techniques, including DRS, XRD, BET-BJH, FESEM, EDX, and TEM. Finally, the stability of the photocatalysts was tested, and a potential photocatalytic reaction mechanism based on a Z-scheme heterojunction was proposed.

Experimental study on the effects of ultrasonic excitation on pore structure of water-bearing coal

Coal seam water injection is one of the main coal mine dust control measures. To study the effects of ultrasonic excitation on the pore structure of water-bearing coal in depth, ultrasonic excitation experiments were conducted with varied variables including ultrasonic excitation time, ultrasonic power, and fluid pressure on coal. The effects of sodium dodecyl sulfate (SDS) treatment and ultrasonic excitation were also compared. The coal samples treated under different conditions are characterized by low-temperature nitrogen adsorption and scanning electron microscopy (SEM) respectively for the quantitative analysis of pore volume and specific surface area and qualitative analysis of surface pore and fracture structure. The results show that ultrasonic excitation can significantly increase the pore volume and specific surface area of coal and damages the inner wall surfaces of the pore to different extents, making the pore inner surfaces rougher. However, the effect of ultrasonic excitation becomes weaker after the pore volume increases to a certain extent, resulting in more uniform pore size and volume distributions. Ultrasonic excitation time affects the pores with smaller size more significantly, and there is a time threshold effect. The volume and specific surface area of large pores and fractures show limited responses (or increases) to as the excitation time increased. The energy is mainly used for the fracturing and expanding the pores with smaller size. The effect of ultrasonic excitation on pore expansion is more obvious under the fluid pressures lower than 4 MPa. High fluid pressures weaken the fracturing and expanding effect of ultrasonic excitation on the pore structure of water-bearing coal. The ultrasonic power threshold effect is also observed. Once exceeding a certain value, further increasing the ultrasonic power does not dramatically affect the pore structure of water-containing coal. Ultrasonic excitation can enlarge the primary pores and fracture and generate secondary pores and fracture in coal. In contrast, the 0.85% SDS treatment is only able to clean the primary small pores, and no new pore structures are formed.

Matrix Compressibility and Its Controlling Factors of the Marine Shale Gas Reservoir: A Case Study of the Ning228 Well in the Southwest Sichuan Basin, China

Exploring the compressibility of the deeply buried marine shale matrix and its controlling factors can help achieve efficient petroleum production. Taking ten sets of deeply buried marine shale core samples from Ning228 wells in the Yanjin area as an example, the matrix compressibility and pore characteristics of deeply buried marine shale reservoirs were investigated by applying mercury intrusion porosimetry (MIP) and nitrogen adsorption/desorption isotherms at a low temperature of 77 K. Mathematical models (based on MIP and nitrogen adsorption/desorption isotherms) were established to analyze the effects of TOC, mineral components, and pore structure on matrix compressibility. The relationship between the compressibility coefficient and the brittleness index was also established. The results show that the compressibility of the shale matrix is significant when the mercury injection pressure ranges from 8.66 to 37 MPa. For deeply buried marine shale, the matrix compressibility is in the range of 0.23 × 10−4–22.03 × 10−4 MPa−1. The influence of TOC and minerals on matrix compressibility is mainly reflected in the control effect of pore structure. High TOC content decreases the overall shale elastic modulus, and high clay mineral content enhances shale stress sensitivity, resulting in a significant matrix compressibility effect. For the effect of pore structure on compressibility, the pore content in shale has a positive effect on matrix compressibility. In addition, the pore-specific surface area is critical to the effective variation of shale matrix compressibility, indicating that the complexity of the shale pore structure is a key factor affecting matrix compressibility.

Microbial resistance stability of rice straw biochar with vermiculite modification: A novel insight into persistent free radicals and pore structure

Biochar is considered a promising material for carbon sequestration owing to its high stability. However, the effects of biochar properties, especially pore structure and persistent free radical (PFR) content, on its microbial resistance stability (MRS) remain unclear. Incubation experiments were conducted to investigate the anaerobic and aerobic MRS of rice straw biochar produced at 300–700 °C, with and without vermiculite modification, and to evaluate the relationship between key biochar properties and MRS. The results showed that PFR signal intensity in biochar was much higher under anaerobic conditions than that under aerobic conditions, increasing with production temperatures of 300–600 °C, but sharply decreasing at 700 °C. Anaerobic MRS of biochar produced at 700 °C was lower than that of biochar produced at 300–600 °C, as indicated by higher CH4 emission. Redundancy analysis revealed a negative correlation between PFR concentration and cumulative CH4 emission with a correlation coefficient of –0.467, and a positive correlation between cumulative CH4 emission and pore volume and specific surface area with correlation coefficients of 0.405 and 0.281, respectively. Biochar dissolved organic carbon content and pH were the two most important factors affecting aerobic MRS as reflected by their high correlation coefficients (0.933 and –0.848) with cumulative CO2 emission. Vermiculite modification enhanced MRS and accordingly lowered the global warming potential of biochar produced at low temperature (300–500 °C) by 4.59–20.2 % and 15.3–42.9 % under anaerobic and aerobic conditions, respectively. However, it had a contrasting effect on biochar produced at 700 °C. Biochar would be more effective at mitigating global warming in paddy fields than in dry lands.

Characterizing pore size distribution of high maturity shales and main controlling factors analysis: A case study of Permian Gufeng Formation in the Lower Yangtze region, China

Shale gas resource is heterogeneously distributed in Permian Gufeng Formation in the Xuancheng area, Anhui Province. This research aims to investigate the pore size distribution of the Permian Gufeng shales via 16 core samples analyses, combined with x‐ray diffraction, low‐pressure nitrogen gas adsorption (N2‐GA), CO2 gas adsorption (CO2‐GA) and scanning electron microscopy (SEM). N2‐GA shows that the nanopores (diameter < 10 nm) are dominated and developed in the samples. The Brunauer–Emmett–Teller (BET) specific surface area (SSA) of the samples ranges from 6.7051 to 29.4384 m2/g, with a mean of 16.0931 m2/g. CO2‐GA results illustrate that micropore is well developed, especially the pores with a diameter of 0.5–0.6 and 0.8 nm. The total organic carbon (TOC) content of the Gufeng shale ranges from 0.42% to 12.82% with an average content of 6.44%, which has both positive correlation with pore SSA and pore volume, while carbonate mineral content has a positive correlation with pore SSA and the volume of macropore and mesopore. Clay mineral content is a negative correlation with pore SSA and micropore volume. Therefore, the high‐maturity Permian Gufeng shale could be more preferential high‐quality gas shale reservoir for further exploration and development in the Xuancheng area, which has more than 4% TOC content, relatively higher carbonate mineral content and relatively lower clay mineral content.

Three‐dimensional simulation of the acidizing process under different influencing factors in fractured carbonate reservoirs

AbstractMatrix acidizing is widely used to enhance oil/gas production in the exploitation of carbonate reservoirs. In this work, a three‐dimensional (3D) hydro‐chemical‐thermal (H‐C‐T)‐coupled model was presented to improve the understanding of the acidizing process. The influence of different influencing factors was analyzed, especially the coupling effect of natural fractures and in situ stress. With the increase in acid injection concentration, the minimum pore volume of acid required for breakthrough (PVBT) decreases. The optimal injection rate and the minimum PVBT increase with increasing initial reservoir temperature. With the increasing initial reservoir permeability, the minimum PVBT increases. With the increasing initial reservoir pore diameter and specific surface area, the minimum PVBT and the optimal acid injection rate increase. When the fracture direction is perpendicular to the direction of the maximum principal stress, the fracture apertures decrease with the increase of the maximum principal stress, which leads to an increase in PVBT and wider paths of wormholes. Lastly, the present H‐C‐T‐coupled model was applied in the context of Tahe reservoir exploitation, which shows that optimizing the acid injection rate is able to enhance the connection between wellbores and natural caves.