Ink-bottle Pores Research Articles

The first material made for air pollution control able to sequestrate fine and ultrafine air particulate matter

Air pollution accounts as a critical environmental issue in different populated cities. With the introduction of smart cities concept, suitable measures to reduce people exposition to pollutants must be part of the policies for a suitable urban development. Generally urban policy makers have proposed some restrictions (for example for traffic), that were resulted insufficient. Then probably, different approaches may be considered to face the air pollution problem.This paper proposes a new porous hybrid material (SUNSPACE) based on the use of industrial silicate minerals and alginate materials to promote PM sequestration in urban areas. It was designed to be applied as a coating on all available external cities surfaces. The synthesis conditions were slightly modified, with respect to the original material, to avoid thermal treatment, and make the material directly applicable. SUNSPACE was characterized by using different techniques: nitrogen physisorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results identify the presence of ink-bottle pores shape, suitable to sequestrate nano and micro PM.Moreover, PM reduction in the atmosphere generally occurs as a consequence of wet or dry deposition conditions, monodisperse Fe3O4 nanoparticles and indoor/outdoor exposure were used to investigate the ability of SUNSPACE in ultrafine PM sequestration.

Investigation of pore structure characteristics and adsorption characteristics of coals with different destruction types

The occurrence of coal and gas outbursts is closely linked to the presence of tectonic coal. To study the pore structure characteristics and adsorption characteristics of different destruction types of coal, nondestructive coal, destructive coal, strongly destructive coal, pulverized coal, and fully pulverized coal are selected based on the coal and gas outburst mine identification specifications. The experimental methods used are liquid nitrogen adsorption, mercury intrusion porosimetry and CH4 isothermal adsorption. The results show that the pore volume obtained by the Barrett–Joyner–Halenda method and the specific surface area increase with increasing destruction type. For all tested coal samples, the N2 adsorption/desorption hysteresis loop is not closed when the relative pressure is low, indicating the existence of ink-bottle pores, an elastic structure of the coal and nitrogen affinity in the coal. With increasing tectonic stress, it becomes more advantageous to produce micropores. The pore volume obtained by the mercury intrusion porosimetry experiment increases with increasing destruction types except for the case of fully pulverized coal. High-pressure mercury causes pore deformation and collapse. When the f value is <0.5, the compression effect of the pores is obvious. The smaller the value of f is, the wider is the pore range affected by the high-pressure mercury. The degree of destruction is positively correlated with the porosity, specific surface area, and Langmuir volume. However, the degree of destruction is negatively correlated with the f value and mercury extrusion efficiency.

Impact of laminae on pore structures of lacustrine shales in the southern Songliao Basin, NE China

Evaluating the influences of laminae on shale pore structures is vital to understand the enrichment mechanism of lacustrine shale gas. This study investigates lacustrine shales from the lower Cretaceous Shahezi Formation in the Changling Sag, southern Songliao Basin, NE China, using mineralogical and geochemical analyses, CO2 & N2 adsorption, and high-pressure mercury intrusion porosimetry (MIP), to compare pore structure characteristics between laminated and massive shales, and elucidate their main controlling factors. Our results show that, laminae in lacustrine shales from the Shahezi Formation include those clay-rich, organic-rich, and silty ones, and minor carbonate-rich ones. Micropores in both laminated and massive shales show tri-modal distributions with main peaks at 0.47–0.54 nm, 0.57–0.63 nm, and 0.80–0.85 nm, respectively; however, the laminated shales exhibit great variations in micropore volumes among different samples. Mesopores within the laminated shales are smaller than those in the massive shales, and their pore volumes (PV) are about 1/3 less than those of the massive shales. This is due to that the laminated shales are rich in slit-like pores whereas the massive shales have more plate-like and ink-bottle pores. Thermal maturity (Ro) and total organic carbon (TOC) contents are the essential factors controlling the development of micropores and mesopores in the laminated shales, however they show weak effects on macropore development in this formation; this may be related to that shales from the Shahezi Formation generally have low TOC contents and type III kerogen. Clay minerals and quartz both have weak relevance to pore development in this formation.

Segmentation of multi-coal seam pore structure in single well profile and its sedimentary control: a case study of Well Y1 in Panguan syncline, western Guizhou, China

The pore structure of coal reservoirs is crucial for the occurrence and production of coalbed methane (CBM). Taking as an example the upper Permian coal-bearing strata profile of Well Y1 in Panguan syncline of western Guizhou, mercury intrusion porosimetry (MIP) and low-temperature N2 adsorption/desorption (LT-N2GA) experiments were carried out on samples from six main coal seams. Hysteresis coefficients of MIP and LT-N2GA were proposed. Fractal dimension of pore structure of each coal seam was calculated. The segmentation of pore structure of multi-coal seams was found. We found the total pore volume (TPV) and specific surface area (SSA) of coal were increased and then decreased as the increase of coal seam buried depth, which is characterized by two-segment distribution. The upper segment included the 7#, 10#, and 12# coal seams, whereas the lower segment contained the 18#, 19#, and 24# coal seams. The TPV, SSA, and MIP hysteresis coefficients and fractal dimension of seepage pore of the upper segment coal seams are larger than those of lower segment coal seams on the whole, while the LT-N2GA hysteresis coefficient, fractal dimension of adsorption pore, and fractal dimension of high-pressure stage of the upper segment are smaller than those of the lower segment. The coal seams in upper segment have more open pores, while the coal seams in the lower segment have more fine neck bottle pores or ink bottle pores. Taken together, these data demonstrated that the coal seams in the upper segment have higher adsorption and seepage capacity, and are more favorable for CBM development. The fundamental reason for the two-segment variation of TPV and SSA of six main coal seams is the symmetry of sedimentary facies in coal-bearing strata; moreover, the ash yield controls the TPV and SSA of coal seams, and the ratio of vitrinite to inertinite (V/I) controls the development of pores.

Shrinkage properties of concretes using blast furnace slag and frost-resistant accelerator

This study investigated the shrinkage properties of concretes using blast furnace slag cement and frost-resistant accelerator as a construction technology in environmental-load-reducing cold weather concretes. The investigation results showed that as the frost-resistant accelerator was added to both Ordinary Portland Cement (OPC) and Blast Furnace Slag Cement (BB), the effect on the properties of fresh concrete was reduced and the compressive strength was increased from an early age. In addition, the free shrinkage strain and cracking potential at the same age tended to increase and the study result verified that the crack generation was also fast in the restrained condition. Meanwhile, the study results verified that the length of both of OPC and BB tended to increase upon adding the frost-resistant accelerator. Pore volume <30 nm diameter, in particular, 20–30 nm pore volume, and ink-bottle pore volume decreased such that the shrinkage volume increased, and the change in pore volume in this range was regarded as having a large effect on the shrinkage properties.

Effect of water content on the structural properties of porous methyl-modified silicate films

Effect of water content in the film-forming solutions on the structure and properties of porous methyl-modified silicate films prepared by acid co-hydrolysis of TEOS and MTEOS with the use of nonionic Brij® 30 surfactant is studied. It is shown by FTIR analysis that hydrolysis of silicon alkoxides is incomplete when 1–2 moles of H2O/alkoxides are used, that leads to a branched and low crosslinked polymer structure characterized by high shrinkage and specific ink-bottle pores. In addition, these films are characterized by lower porosity and higher dielectric constant values in comparison to ones obtained from the sols with 4–8 moles of H2O/alkoxides due to change of interaction between silicate species and surfactant micelles. Effect of water deficiency is the most pronounced if hydrolysis takes place in initially diluted solution compared to the solution prepared by dilution of prior concentrated and aged sol.

Ink-bottle Effect and Pore Size Distribution of Cementitious Materials Identified by Pressurization⁻Depressurization Cycling Mercury Intrusion Porosimetry.

Capturing the long-term performance of concrete must be underpinned by a detailed understanding of the pore structure. Mercury intrusion porosimetry (MIP) is a widely used technique for pore structure characterization. However, it has been proven inappropriate to measure the pore size distribution of cementitious materials due to the ink-bottle effect. MIP with cyclic pressurization–depressurization can overcome the ink-bottle effect and enables a distinction between large (ink-bottle) pores and small (throat) pores. In this paper, pressurization–depressurization cycling mercury intrusion porosimetry (PDC-MIP) is adopted to characterize the pore structure in a range of cementitious pastes cured from 28 to 370 days. The results indicate that PDC-MIP provides a more accurate estimation of the pore size distribution in cementitious pastes than the standard MIP. Bimodal pore size distributions can be obtained by performing PDC-MIP measurements on cementitious pastes, regardless of the age. Water–binder ratio, fly ash and limestone powder have considerable influences on the formation of capillary pores ranging from 0.01 to 0.5 µm.

How Solutes Modify the Thermodynamics and Dynamics of Filling and Emptying in Extreme Ink-Bottle Pores

We investigate the filling and emptying of extreme ink-bottle porous media-micrometer-scale pores connected by nanometer-scale pores-when changing the pressure of the external vapor, in a case where the pore liquid contains solutes. These phenomena are relevant in diverse contexts, such as the weathering of building materials and artwork, aerosol formation in the atmosphere, and the hydration of soils and plants. Using model systems made of vein-shaped microcavities interconnected by a mesoporous matrix, we show experimentally that the presence of a nonvolatile solute shifts the condensation and evaporation transitions and in a way that is consistent with a modified Kelvin-Laplace equation that takes into account the osmotic pressure of the solution. Emptying occurs far below saturation, when the Kelvin stress, mediated by the large curvature of the liquid-vapor interfaces in the nanopores, is negative enough to induce spontaneous bubble nucleation in the microveins. Filling, on the other hand, occurs close to equilibrium (i.e., at saturation, psat for pure water and ps < psat for a solution), driven by the weak capillary pressure of the liquid-vapor interface in the microveins. Interestingly, solutes allow the system to reach situations where the vapor is supersaturated with respect to the solution ( ps < p < psat). We show that in that latter situation, a condensation layer covers the outer surface of the porous system, preventing the generation of Kelvin stresses but inducing osmotic stresses and flows that are vapor pressure-dependent. The timescales and dynamics reflect these different driving forces: emptying proceeds through discrete, stochastic nucleation events with very fast, unsteady bubble growth associated with a poroelastic relaxation process, while filling occurs collectively in all veins of the sample through a slower steady-state process driven by a combination of osmosis and capillarity. The dynamics can however be rendered symmetrical between filling and emptying if bubbles pre-exist during emptying, a case that we explore using cycling of the vapor pressure around equilibrium.

Shale-gas accumulation and pore structure characteristics in the lower Cambrian Niutitang shales, Cen-gong Block, South China

To evaluate pore networks of the lower Cambrian Niutitang Shale in the Cen-gong Block, multiple techniques, including geochemical analysis, low-pressure gas (CO2 and N2) adsorption, mercury intrusion capillary porosimetry (MICP) and field-emission scanning electron microscope (FE-SEM), were performed to investigate pore structure, including pore-size distribution (PSD), pore volume and surface area of black organic-rich shales from two wells to better understand the mechanism of shale-gas accumulation. Geochemical analysis shows that equivalent vitrinite reflectance ranges from 2.1 to 3.5% and are overmature. Surface areas and pore volumes of micropores calculated from CO2 adsorption, which vary from 8.23 to 37.39 m2/g and from 3.06 10−3 to 10.89 10−3 cm3/g, respectively, can provide large amounts of adsorptive sites for shale-gas accumulation. N2 adsorption shows reversed S-shaped isotherms, which are classified into type H2 and H3 hysteresis loops, indicative of ink-bottle pores and slit-or plate-like pores. N2 adsorption and MICP analysis indicates that the inorganic-associated pores in shales may play a significant role in the storage and production of hydrocarbons. High-resolution FE-SEM analysis suggests that OM pores (OMPs) are common in Niutitang samples with a dominant diameter less 50 nm, but a sample with the highest total organic carbon (TOC) of 10.01 wt% has few OMPs, whereas a sample with the TOC of 7.51 wt% has more OMPs. The percentage of OMP area vs total organic matter area (Øs) ranges from 1.70 to 7.92%. The pore structure characteristics of TX1 well, calculated by multiple techniques, are better than samples from TM1 well. In addition, pore types are dominated by interparticle, intraparticle and organic matter pores, and the minor amounts of OMPs in TM1 well indicates that most of the organic matter may have lost the potential to generate hydrocarbons owing to the release of formation pressure with some graphitisation and high-angle fractures larger in the TX1 well. TOC content, mineral composition and tectonically related thermal maturity may be the main controlling factors of the pore structure and the lower Cambrian Niutitang Shale demonstrates the greatest potential for shale-gas production in South China.

Pore characteristics and influencing factors of different types of shales

Abstract Shales in China mainly fall into three categories, namely marine, transitional and lacustrine shales. Various shales have different pore characteristics. We studied the formation, occurrence, pore types and morphological characteristics of micropores, mesopores and macropores in different types of shales through the approaches of gas adsorption and mercury injection. Our study found that the marine shale samples have larger specific surface area and pore volume, providing a good hosting space for adsorption gas and free gas. Furthermore, marine samples are dominated by ink-bottle pores, which are conducive to adsorption of shale gas. Continental and transitional pore types are mainly open pores, characterized by good pores’ connectivity that is conducive to the migration of shale gas. The main factors controlling the pore characteristics of the three types of shales were analyzed by investigating specific surface area, pore volume, organic content, clay mineral content, maturity and burial depth. Our study demonstrated that specific surface area and pore volume development have a good correlation with organic matter in the three types of shales. Types of organic matter can affect the development of organic pores. The discrepancy in occurrence of organic matter leads to different correlations between the three types of shales and clay minerals. On the other hand, maturity impacts on pores of shales in two aspects: organic matter and clay mineral transformation. Meanwhile, compaction and dissolution of organic acid in hydrocarbon-generation process are proved to be especially important to pore structure transformation.

Effect of styrene-butadiene rubber latex on the rheological behavior and pore structure of cement paste

Styrene-butadiene rubber (SBR) latex is beneficial to the workability of cement-based materials, but the mechanism remains unclear. This study aims to investigate the effect of SBR latex on the rheological property and pore structure of cement paste. The results showed that the fluidity of the modified cement-based material was improved, and a significant linear relation was obtained between the air content and the fluidity of the cement paste. The yield stress and viscosity of the paste decreased with increasing SBR latex content, and the modified cement paste exhibited shear-thinning behavior. In addition, the SBR latex can deteriorate the pore structure of the hardened cement paste at 3 days due to the hydrophobic groups easily trapping the air into the paste. Compared with that of the ordinary Portland cement paste, the number of pores (size range of 0.1 μm–1 μm and 10 μm-200 μm) in the SBR-modified cement paste was clearly increased. However, the lowest porosity was achieved at 28 days, when 2% SBR was used due to the filling effect of the hydration products and polymer particles. The throat/pore ratio and fractal dimension increased with the SBR latex content, illustrating the increasing of ink-bottle pores with a rough surface.

Quantitative characterization of middle-high ranked coal reservoirs in the Hancheng Block, eastern margin, Ordos Basin, China: implications for permeability evolution with the coal macrolithotypes

ABSTRACTMacrolithotypes control the pore-fracture distribution heterogeneity in coal impacting the coalbed methane (CBM) production from the reservoir. However, few studies have focused on the characteristics of macrolithotypes. Here, the macrolithotype samples from the three continuous seams (No. 3, 5 and 11) in the Hancheng Block, Ordos Basin, China were quantitatively characterized by multiple length scales. The results indicate that the bright coal has the best development of micro-fracture than those of the other macrolithotypes, which with good openness and connectivity under the optical microscopy; N2 adsorption/desorption results reflect that the adsorption pores of the semi-dull and dull coal are more developed than the bright coal and semi-bright coal, and are dominated by plate-like and ink-bottle pores. The characteristics of the mercury intrusion/extrusion curves were determined by the mercury injection (MIP). From bright to dull coal the pore connectivity being worse, and the uniformity of pore and throats distribution becomes lower. The pore type that divided by NMR are recovered to be seepage type (the bright), comprehensive type (the semi-bright and semi-dull), and the type of adsorption (the dull). The behavioral differences would impact the porosity and permeability in coal. Thus, by the well logging evaluation approach, the relationship between coal macrolithotypes and select logging parameters were determined for coal macrolithotype identification, and with the petrel software included, the porosity-permeability models were built to investigate the permeability evolution with the coal macrolithotypes. Macrolithotypes are closely related to the permeability of coal reservoirs in this area. The greater contribution of permeability is typically from of the bright and semi-bright coal, and followed by semi-dull and dull coal, the better development of bright coal, the better permeability of the reservoir and vice versa.

Pore Parameters-Dependent Adsorption Behavior of Volatile Organic Compounds on Graphene-Based Material.

Mesoporous graphenes (MPGs) with interpenetrating porous networks are successfully obtained by the pyrolysis of composite gel consisting of graphite oxide (GO) and the amphiphilic triblock copolymer (Pluronic P123) under Ar atmosphere, wherein P123 is used as a soft-template. The as-prepared composite gel is obtained following self-assembly and freeze-drying. The obtained MPGs have high BET specific surface area (531-746 m2 g-1 and ink-bottle like pores with three dimensional interconnected network. Furthermore, the specific surface area and porous parameters such as pore volume, pore size, and pore size distribution of MPGs can be rationally controlled by regulating the initial mass ratio of P123 to GO. With the increase of P123 ratio, the average mesopore size is decreased from ∼16.4 nm to ∼9.5 nm, which is similar to the diameter size of P123 micelles. Also, the adsorption capacities of MPG-20 for 52 indoor air standard components (100 μg mL-1, Supelco) are compared with two different materials, namely commercial porous polymers (2,6-diphenyleneoxide) and reduced graphene oxide (RGO). The result shows that MPG-20 has significantly better adsorption capacity than RGO but also similar or slightly better than commercial porous polymer. The mesoporous structure and surface chemistry of MPGs were the most important factors for the enhancement of the adsorption efficiency for volatile organic compounds.

Influence of In Situ Pyrolysis on the Evolution of Pore Structure of Oil Shale

The evolution of pore structure during in situ underground exploitation of oil shale directly affects the diffusion and permeability of pyrolysis products. In this study, on the basis of mineral analysis and thermogravimetric results, in combination with the low-pressure nitrogen adsorption (LPNA) and mercury intrusion porosimetry (MIP) technique, the evolution of pore structure from 23 to 650 °C is quantitatively analyzed by simulating in situ pyrolysis under pressure and temperature conditions. Furthermore, based on the experimental results, we analyze the mechanism of pore structure evolution. The results show the following: (1) The organic matter of Fushun oil shale has a degradation stage in the temperature range of 350–540 °C, and there is no obvious temperature gradient between decomposition of kerogen and the secondary decomposition of bitumen. The thermal response mechanisms of organic matter and minerals are different in each temperature stage, and influence the change of pore structure. (2) Significant changes occur in pore shape at 350 °C, where thermal decomposition of kerogen begins. The ink-bottle pores are dominant when the temperature is less than 350 °C, whereas slit pores dominate when the temperature is greater than 350 °C. (3) The change in pore structure of oil shale is much less significant from 23 to 350 °C. The pore volume, porosity, and specific surface area (SSA) of samples increase rapidly with temperature varying from 350 to 600 °C. The variation of each parameter is dissimilated from 600 to 650 °C: the porosity and pore volume increases with a small gradient from 600 to 650 °C, and SSA decreases significantly. (4) The lithostatic pressure does not cause change in the evolution discipline of the pore structure, but the inhibitory effect on the pore development is significant.

Diffusion of Water and Electrolytes in Mesoporous Silica with a Wide Range of Pore Sizes

The diffusion of alkaline chlorides (LiCl, KCl, and CsCl) and water in mesoporous silica samples with pore sizes covering the range from micropores (2 nm) up to mesopores larger than 30 nm have been measured by resorting to a simple diffusional technique in the case of electrolytes and 1H NMR in the case of water. The morphology of the silica samples varies from a microporous structure, an interconnected network of pores, and typical mesoporous materials with ink-bottle pores, with increasing pore size. The release of electrolytes from the silica as a function of time exhibits two differentiated regimes, at short and long times, which correlates quite well with the size of the pores and that of necks of the pores, respectively. The diffusion of water inside the pores follows the same trend with pore size that the diffusion of electrolytes, indicating a coupling between the ions and water diffusional mobilities. The tortuosity effect on the diffusion of all studied electrolytes and water shows a monotonic ...

Effect of pore geometry on the electrocatalytic performance of nickel cobaltite/ carbon xerogel nanocomposite for methanol oxidation

A new nickel cobaltite/carbon xerogel nanocomposite (NiCo2O4/CX) is obtained by preparing carbon xerogel (CX) by using sol-gel technique followed by growing the NiCo2O4 nanoneedles over CX using hydrothermal method. The used characterization techniques are XRD, HRTEM, FESEM and surface area measurements. The physicochemical properties of NiCo2O4/CX show face centered cubic nanoneedles -like structures containing different lengths and widths. In addition, BET analysis clarify that NiCo2O4/CX nanocomposite is mesoporous with uniform cylindrical pore geometry with two modular systems compared to narrow necks ink-bottle pore geometry for pristine NiCo2O4. Electrocatalytic activity and stability of glassy carbon modified electrode with NiCo2O4/CX towards methanol electro-oxidation in basic medium are studied using cyclic voltammetry and chronoamperometry techniques. Data shows, the NiCo2O4/CX modified electrode gives a catalytic current density of 98 mA cm−2 at 0.29 V with a good stability of 90.6% current retention after 100 repetitive cycles compared to 37.8 mA cm−2 at 0.38 V for pristine NiCo2O4. The highly electrocatalytic activity of NiCo2O4/CX modified electrode is correlated to the synergistic effects between the pore geometry and accessible porosity.

Influence of chemical damp proof cream on the capillary action and microstructure of mortars

This study tests the impact of using a chemical damp-proof cream, containing mainly silanes and siloxanes, on disrupting the damp rising in mortars. The test is performed on mortar specimens using a mercury porosimetry, a contact angle tester and a thermographic camera. Based on the test, the differential pore volume distribution and content of ink-bottle shape pores were defined, areas of apparently different hydrophobicity were indicated and the maximum distances of the chemical injections were set. The results show that the chemical damp-proof cream has a significant influence on the hydrophobicity and microstructure.

Evaluation of the combined deterioration by freeze–thaw and carbonation of mortar incorporating BFS, limestone powder and calcium sulfate

The durability performance of cementitious material is traditionally based on assessing the effect of a single degradation process. However, this study investigates the coupled deterioration properties of mortar incorporating industrial solid waste—ground granulated blast furnace slag (BFS) and different mineral admixtures, such as calcium sulfate (CS) and limestone powder (LSP). The combined deterioration properties caused by carbonation and frost damage in the mortar sample were experimentally investigated with respect to accelerated carbonation and freeze–thaw tests. Different degrees of deterioration, i.e. after subjected to 12, 30 and 60 freeze–thaw cycles, were induced in the freeze–thaw tests. The experimental investigation of single degradation revealed that the compressive strength, frost resistance and carbonation resistance decrease as the BFS replacement ratio increases by weight from 0 to 45%. The less amount of CH in the BFS cement leads to the carbonation progress more easily. Moreover, to achieve the same strength as ordinary Portland cement, 2 wt% CS and 4 wt% LSP in the BFS mortar are required. However, the data shows that incorporating LSP into the BFS mortar produces a lower frost resistance. The combined damage tests revealed that different deterioration degrees resulting from 12, 30 and 60 freeze–thaw cycles slightly decreased the carbonation resistance, which is related to the decrease in the inkbottle pore volume due to its water retention characteristics. Simultaneously, the pre-carbonation deterioration could effectively decrease the surface mass scaling of the freeze–thaw and the pore structure undergoes densification due to pre-carbonation.

Effect of fly ash on the pore structure of cement paste under a curing period of 3 years

The service life and durability of concrete structures strongly depend on the transport properties of the concrete. These transport properties are highly related to their microstructure, especially the pore structure of the hydrated cement paste. In this paper the microstructure development of cement paste and cement paste blended with fly ash is investigated, from solid phase to pore phase, at a long-term curing period up to 3years. The solid phases are observed by environmental scanning electron microscope. The pore structure of blended cement paste is determined by mercury intrusion porosimetry. The results indicate that the addition of fly ash increases the total porosity of cement paste, not only at early ages, even at curing age of 3years. The voids in hollow fly ash particles act as ink-bottle pores with progress of the pozzolanic reaction of fly ash, resulting in the increase of the total porosity of blended cement paste.

Experimental investigations on the geometry and connectivity of pore space in organic-rich Wufeng and Longmaxi shales

The nano-scale pore systems of organic-rich shale reservoirs were investigated from Upper Ordovician Wufeng and Lower Silurian Longmaxi Formations in southeast Sichuan Basin. These two formations are the most important target plays of shale gas development in China. The purpose of this article is to assess the geometry and connectivity of multi-scale pore systems, and to reveal the nature and complexity of pore structure for these over-mature gas shales. To achieve these objective, total organic carbon, mineralogy, image analyses by focused ion beam-SEM, low pressure nitrogen adsorption, mercury injection capillary pressure (MICP) and spontaneous fluid [deionized (DI) water and n-decane] imbibition were performed.Most of the visible pores from SEM work in Wufeng and Longmaxi shales are within nm- and μm-size regimes and belong to organic matter (OM) pores. The shapes of OM pore in Longmaxi samples are elliptical, bubble-like, irregular or rounded. Wufeng pores are mainly irregular, linear and faveolated, even though two shales have small depth difference, as well as similar thermal maturity, kerogen type and TOC content. Nano-scale pores in Longmaxi are mainly associated with narrow platelike or slitlike pores with pore size of 3–50 nm; while inkbottle pores are dominant in Wufeng samples and over 88% of the pore volume is contributed by pores with diameter <20 nm. Overall, porosity, pore volume and surface area values from Wufeng samples are much higher than those in Longmaxi, which is mainly correlated with the different TOC contents and mineral compositions. MICP tests show that a total of 5 inflection points (indicative of different connected pore networks) are identified in all pressure regions for Longmaxi, while only 2 for Wufeng in high pressure region with the associated permeability at nano-darcy range. Imbibition curves of n-decane are divided into three stages: the initial stage (Stage Ⅰ), linear imbibition stage (Stage Ⅱ) and late imbibition stage (Stage Ⅲ), and the slopes of linear imbibition stage are around 0.5, suggesting well-connected pore spaces for n-decane. In contrast, imbibition curves for DI water are divided in two stages with linear slopes of between 0.25 and 0.5, indicating moderately-connected pore networks for the movement of DI water. This is consistent with the mixed-wet nature of these shales, with observed weak wettability for hydrophilic, while complete wetting for hydrophobic fluids.