Number Of Pores Research Articles

Diagenetic characteristics and microscopic pore evolution of deep shale gas reservoirs in Longmaxi Formation, Southeastern Sichuan basin, China

The Lower Silurian Longmaxi Formation is the favorable target area for deep shale gas exploration and development in southeastern Sichuan Basin. Based on whole-rock X-ray diffraction analysis, scanning electron microscope, reservoir evolution thermal simulation experiment and nitrogen adsorption experiment, the diagenetic characteristics of deep shale reservoir in Longmaxi Formation were analyzed, and the reservoir pore evolution law was clarified. The results show that: ①The diagenetic minerals of the deep shale in the Longmaxi Formation are mainly quartz and clay minerals, with a small amount of carbonate minerals and feldspar. The primary inorganic pores are mainly controlled by mechanical compaction and cementation (quartz, carbonate, clay, pyrite). The organic pores are mainly controlled by the thermal maturity of organic matter, dissolution and later compaction. ②In the process of thermal simulation experiment, the organic pores of shale show a process of change from scratch, from small to large and then from large to small. Later, the organic matter is affected by compaction and graphitization, and the volume of micropores and mesopores begins to decrease. ③The shale pores of Longmaxi Formation have undergone several evolutionary stages. In the early stage of diagenesis, compaction caused a large number of inorganic pores to disappear. In the middle stage of diagenesis, kerogen hydrocarbon generation occupied pores, dissolution and cementation transformed pores. In the late diagenetic period, liquid hydrocarbon cracking gas and pressurization promote the development of organic pores.

Mechanism of interaction between hydration–carbonation of C2S

The physical and microscopic properties of γ-C2S and β-C2S under hydration, carbonation, and hydration–carbonation cycle reactions were investigated. The hydration–carbonation cycle reaction facilitated the carbon sequestration of C2S, and the generation of CaCO3 filled the pores of the matrix and enhanced the matrix density in the carbon fixation reaction process. In the subsequent hydration and reaction process, the formation of hydration products increased the number of pores in the matrix and reduced the matrix density. Post-hydration, γ-C2S slurry became powder and had no mechanical strength. However, after carbonation reaction and two carbonation–hydration cycles, γ-C2S exhibited better mechanical properties than β-C2S.

Effect of laser power on the microstructure and corrosion resistance of laser cladding Mo2NiB2 coatings

In this study, Mo2NiB2 coatings were prepared by the laser cladding technique and the relationship between coating microstructure and corrosion resistance with cladding power was analyzed. The results showed that Mo2NiB2 was reactively generated in all coatings while Mo2FeB2 and (Fe, Ni) were also present in the coatings due to dilution of the substrate. There was a good metallurgical bond between the coating and the substrate. The white cermet phase and black Fe-rich phase alternated within the coatings. As observed from the surface, the ceramic phase spreads out in a flattened shape and the black Fe-rich phase was present in a large number of pores. Due to the overdilution of the substrate, the volume of the ceramic phase decreased at a power of 800 W and the Fe content within the coating increased. The corrosion resistance of the coatings increased as the laser power increased from 500 to 700 W. Then the corrosion resistance of the coatings decreased at 800 W due to the excess Fe content and the decrease in the relative content of Mo2NiB2 and (Fe, Ni). Mo2NiB2 coating prepared at 700 W has the best corrosion resistance.

Elucidating the performance of hexamethylene tetra-amine interlinked bimetallic NiCo-MOF for efficient electrochemical hydrogen and oxygen evolution.

Bimetallic metal-organic frameworks (MOFs) play a significant role in the electrocatalysis of water due to their large surface area and availability of increased numbers of pores. For the inaugural time, we examine the effectiveness of a hexamethylene tetra-amine (HMT)-induced 3D NiCo-MOF-based nanostructure as a potent bifunctional electrocatalyst with superior performance for overall water splitting in alkaline environments. The structural, morphological, and electrochemical properties of the as-synthesized bifunctional catalyst were examined thoroughly before analyzing its behavior towards electrochemical water splitting. The HMT-based NiCo-MOF demonstrated small overpotential values of 274 mV and 330 mV in reaching a maximum current density of 30 mA cm-2 for hydrogen and oxygen evolution mechanisms, respectively. The Tafel parameter also showed favorable HER/OER reaction kinetics, with slopes of 78 mV dec-1 and 86 mV dec-1 determined during the electrochemical evaluation. Remarkably, the NiCo-HMT electrode exhibited a double-layer capacitance of 4 mF cm-2 for hydrogen evolution and 23 mF cm-2 for oxygen evolution, while maintaining remarkable stability even after continuous operation for 20 hours. This research offers a valuable blueprint for implementing a cost-effective and durable MOF-based bifunctional catalytic system that has proven to be effective for complete water splitting. Decomposition of water under higher current densities is crucial for effective long-term generation and commercial consumption of hydrogen.

Enhancing the seawater desalination performance of multilayer reduced graphene oxide membranes by introducing in-plane nanopores: a molecular dynamics simulation study.

In this study, using MD simulation, the effect of creating in-plane nanopores in a reduced graphene oxide (rGO) membrane and the formation of a reduced nanoporous graphene oxide (rNPGO) membrane is proposed to increase salt rejection and water flux. To this end, the desalination performance of r1NPGO, r2NPGO and r4NPGO membranes, which have 1, 2 and 4 pore(s), respectively, with a diameter of 0.9 nm and the r1NPGO-3 nm membrane, which has 1 pore with an approximate diameter of 3.0 nm, was investigated and compared from a molecular point of view. The simulation results show that in the rNPGO membranes, by increasing the number of pores from 1 to 4, water flux increases by ∼6 times compared to the rGO membrane. Meanwhile, upon increasing the pore size from 0.9 to 3.0 nm, water flux is enhanced by ∼16 times compared to the rGO membrane. The simulation results also demonstrate that the rGO membrane has two paths for water penetration, which are called the interlayer pathway and in-slit pathway. Moreover, pores in the rNPGO membranes provide another additional path for water transfer by shortening the lateral size of the membranes. This path is referred to as the in-pore pathway. By increasing the size of the pore in the r1NPGO-3 nm membrane, the contribution of the in-pore pathway increases and plays an important role. Furthermore, the simulation results show that in all rGO and rNPGO membranes, the interlayer space acts as a barrier for ions. Therefore, complete salt rejection is observed. Interestingly, by increasing the pore size in the r1NPGO-3 nm membrane, this membrane still maintains complete salt rejection. The observed phenomenon can be a result of very high water flux in this membrane. By increasing water flux, the presence of water molecules around Na+ and Cl- ions decreases. As a result, the formation of Na+Cl- ionic clusters is strengthened in such a way that these clusters do not have the ability to pass through large pores of 3.0 nm.

Cervical Collagen Network Porosity Assessed by SHG Endomicroscopy Distinguishes Preterm and Normal Pregnancy - a Pilot Study.

Preterm birth (PTB) remains a pressing global health concern associated with premature cervical ripening and weakened cervical mechanical strength. Second harmonic generation (SHG) microscopy has proved instrumental in tracking progressive changes in cervical collagen morphology during pregnancy. To translate this imaging modality into clinical practice, we have developed a flexible SHG endomicroscope for label-free visualization of cervical collagen architecture. This study aims to assess the feasibility of our SHG endomicroscope for non-invasive differentiation of normal and PTB mouse models, with the ultimate goal of enabling early diagnosis and risk assessment of PTB in vivo. in this pilot investigation, we conducted endomicroscopic SHG imaging on frozen cervical tissue sections and intact cervices resected from both normal pregnant mice and mifepristone-induced PTB mouse models, and then analyzed the acquired images to identify collagen morphology characteristics associated with abnormal cervical collagen remodeling. quantitative image analysis revealed significantly altered collage spatial distribution, larger collagen fiber diameter and pore size, along with reduced pore numbers in SHG endomicroscopy images from PTB mouse models compared to normal pregnant mice. Similar trends were consistent across SHG endomicroscopy images of subepithelial collagen fibers acquired directly from intact cervices. overall, the experiment results underscore the potential of SHG endomicroscopy, coupled with quantitative image analysis, for clinically evaluating cervical collagen remodeling and PTB risk.

The effect of egg shape index on pore number and hatching performance in Susex hens

This study was carried out to investigate the effect of egg shape index on pore number and hatching performance in Sussex chickens. The material of the study consisted of 63 eggs obtained from the Sussexbreed chicken flock of a private enterprise engaged in chicken rearing in Konya. Eggs were divided into two groups as below 75 (Group-1, 75

Green Synthesis Nanopartikel Karbon Aktif dari Limbah Tempurung Kelapa

Activated carbon from coconut shell waste is a porous solid that has a large surface area with high absorption capacity, making it an alternative for reducing levels of heavy metal ions in the air. Active carbon is made by carbonization and chemical activation, then SEM testing is carried out to see the morphology of the activated carbon and analyzed using ImageJ software. This research aims to determine the effect of chemical activation and no activation on the number of pores formed in activated carbon. From the results of research that has been carried out, there are more pores formed after carbon is activated compared to carbon without activation. This is because the carbon surface without activation is still covered by impurities. In addition, unactivated carbon and activated carbon from coconut shells have pore sizes that fall into the mesoporous category.

Silene commelinifolia var. ruscifolia (Caryophyllaceae) taksonunun morfo-anatomik, palinolojik ve karyolojik karakterizasyonu

A morphological, anatomical, palynological, and karyological of Silene commelinifolia var. ruscifolia, an endemic taxon for Türkiye, was examined in the present study. The anatomical approach described the root from outside to inside, by the periderm, cortex, endodermis, perisycle tissues, and vascular system. The stem is formed by cuticula layer, epidermis tissue, cortex tissue, sclerenchymatical rings and vascular system. The leaves, sepals and petals are formed by cuticula layer, epidermis tissue which is at the bottom, and the upper surface of the leaf and mesophyll tissue. The length of the root 30-130 mm and the diameter of the root 6-22 mm, type of root taproot, stem erect, and cylindric, the length of the stem is 46-156 mm and the diameter of stem 20-35 mm, intensive glandular puberulous, cauline leaves ovate-cordate, 6-34 x 1-25 mm, intensive glandular puberulous, basal leaves linear-oblanceolate, 6-69 x 1-9 mm, intensive glandular puberulous, the flower monocline, diclamideic, fruit 9-18 mm, denticid capsula, seeds reniform, brown, at the size of 1.62-2.17 x 1.25-1.67 x 0.75-1.125 mm. Pollen periporate, prolate-spherical (A/B=1.03), long axis of pollen (A) 31.18 μm, short axis of pollen (B) 30.14 μm, structure tektat, ornamentation microechinat-perphorate, number of pores 24-34, the length of pore (Plg) 4.95 μm, the width of pore (Plt) 4.18 μm, distance between pores 5.34 μm, the width of ecsin 2.23 μm on the average. In our study, it was determined that the chromosome number of the species was 2n=24.

Enhanced Performance of Solid Polymer Electrolyte Separator Lithium Battery with Cellulose Acetate From Empty Palm Fruit Bunch Coated Al2O3-Polyacrylic Acid

As lithium battery technology improves, it becomes more important to have solid polymer electrolyte dividers that work better. The objective of this study is to enhance the efficiency of solid polymer electrolyte separators in lithium batteries. This research aims to expand the limits of innovation in hybrid separator development by utilizing empty palm fruit bunches (OPFEB) as a plentiful source of cellulose acetate. This approach enhances ion transfer by increasing the number of pores in the separator. However, there are challenges to achieving the desired levels of optimal ionic conductivity. In order to address these constraints, this study presents a novel Al2O3-PAA inert ceramic oxide coating treatment that is applied to the separator by a spin coating technique. An electron microscope was utilized to observe the pore structure of the separator. Additionally, the separator underwent physical, mechanical, thermal, and cyclic voltammetry tests. The findings of this research indicate a significant increase in the physical properties, particularly the porosity and mechanical strength. The thermal shrinkage of the Al2O3-PAA coated separator is below 10% when exposed to a temperature of 140 oC for 30 minutes. The Cyclic Voltammetry test results demonstrate a pronounced loop curve, indicating an improvement in the ionic conductivity of the Al2O3-PAA coated separator. The findings of this study provide a method to enhance the efficiency of separator performance at high temperatures while maintaining safety and long battery life.

Pore characteristics and mechanical behaviors of autoclaved aerated concrete produced from coal bottom ash and tailings

AbstractThe solid wastes such as coal bottom ash and tailings are currently widely used in various building materials, but further research on their application in autoclaved aerated concrete (AAC) is needed. To study the physical and mechanical properties of AAC produced from coal bottom ash and tailings, the pore characteristics of two different density grades of AAC were extracted and analyzed, and wave velocity and uniaxial compressive tests under water‐saturated and dry conditions were carried out. The results show that the AAC produced from solid waste has excellent performance. The specimen is anisotropic, and the pore size distribution of its cross‐section is mainly concentrated in the ranges of <0.1, 0.1–0.5, and 0.5–1.0 mm. The pore size perpendicular to the direction of rise is smaller and the pores number is greater. The wave velocity and uniaxial compressive strength of the test specimens in the water‐saturated state are significantly lower than those in the dry state. The strengths of specimens loaded perpendicular to the direction of rise are higher than those loaded parallel to the direction of rise whether water‐saturated or dry. The failure mode of the water‐saturated specimens are different from those of dry specimens, which is manifested in the act that there are fewer surface cracks when the specimens fail in the water‐saturated state, while there are more surface cracks in the dry specimens, and their morphology is irregular. The physicochemical effect between water and components and the mechanical effect of pore water are the reasons for the deterioration of AAC's mechanical properties. The results help to reveal the performance of AAC produced from solid waste and have good practical significance.

Aeolian sand stabilized by using fiber- and silt-reinforced cement: Mechanical properties, microstructure evolution, and reinforcement mechanism

Northwest China has a large amount of aeolian sand, which exhibits poor gradation, low cohesive force, and loose structure; thus, this sand is difficult to be directly used as engineering construction materials. To solve this problem, this study mixed fiber, silt, and cement to stabilize aeolian sand. The effects of the fiber content (0%, 0.5%, 1%, 2%, 3%, and 4%), fiber length (6, 12, and 19 mm), silt content (10%, 15%, and 20%), and curing time (7, 14, and 28 d) were evaluated by conducting indoor unconfined compressive strength tests, and the strength prediction and constitutive models were established. In addition, the microstructural and pore variation characteristics were studied by performing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and nuclear magnetic resonance (NMR) tests, and the stability mechanism was elucidated. The results showed that the addition of fibers and silt can significantly improve the strength and ductility of cement-stabilized aeolian sand. Under the optimal mixing conditions (fiber length: 12 mm; fiber content: 2%; silt content: 15%), the strength of the sample increased by 274.2% (reaching 1684 kPa) compared with that of cement-stabilized aeolian sand (450 kPa). A positive correlation was observed between the curing time and strength development of the samples. The established strength prediction model effectively predicted the strength variations in the specimens, whereas the constitutive model accurately reflected the stress-strain relationship of the specimens. The SEM results revealed that the coupling effect of fibers, silt, and cement makes the specimens more compact and improves the overall stability. The results of the NMR showed that the numbers of macropores and mesopores decreased significantly and that the numbers of small pores and micropores increased with 2% fiber content; the porosity of the specimen was 12.3%, which was 28.6% lower than that of ordinary-cement-stabilized aeolian sand. This study advocates making full use of local silt to stabilize aeolian sand, which has significant advantages in terms of improved mechanical properties, environmental protection, and reduced project costs compared with traditional cement-stabilized aeolian sand. The results of this study have important theoretical and practical significance for the engineering and design of projects in aeolian sand areas.

Initial pore distribution characteristics and crack failure development of cemented tailings backfill under low impact amplitude

The stability of the cemented paste backfill is threatened by the dynamic disturbance during the excavation of the surrounding ore body. In this paper, the computerized tomography (CT) and Split Hopkinson Pressure Bar (SHPB) tests were conducted to explore the initial pore distribution characteristics of the cemented tailings backfill (CTB) and the development of the crack under low impact amplitude. SHPB tests were conducted with impact amplitudes of 34, 37, and 39 mV, respectively. Results show that the initial pores of CTB were steadily distributed with the height of CTB. The CTB contained many initial pores with similar pore size distribution characteristics, and the largest number of pores is between 0.1 and 0.3 mm. Most of the cracks in CTB after low impact amplitude develop and expand along the initial pores, and the damage of CTB mainly exists in shear cracks. A dependence has been established that the dynamic uniaxial compressive strength of the CTB increases, the total crack volume first increases and then decreases, and the number of cracks increases as the impact amplitude increases. The research results can provide a valuable reference for the dynamic performance of CTB under low impact amplitude and the design of mining backfill.

Preparation of 1D Porous Fe-N-C based ORR Electrocatalysts by Pyrolysis of Trace Fe-doped ZIF-8/PAN Electrospun Fibres

The development of a simple and efficient method for batch preparation of porous Fe-N-C catalysts is of great significance for it large-scale application. Electrostatic spinning is a common method that can be used to produce carbon-based catalysts on a large scale simply by increasing the number of needles. However, it is still difficult to control the pore structure and composition of the pyrolysis products of electrostatically spun fibers by modulating the composition. In this paper, highly graphitized one-dimensional Fe-N-C catalysts with a large number of open pores were prepared by pyrolysis of electrospun fibres of trace Fe-doped ZIF-8 particles with PAN. The materials were structurally and compositionally analyzed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and nitrogen adsorption-desorption test. The electrocatalytic ORR performance of the catalysts was characterized by cyclic voltammetry, linear scanning voltammetry, and rotating ring-disk electrode tests. The results show that trace Fe doping achieves a transition from closed to open pores, exposing the active sites within the pores to allow them to participate efficiently in the reaction. Fe could catalyze the formation of surface graphite structures during pyrolysis, which reduces the charge transfer resistance and indirectly increases the ORR reaction rate. The formation of highly reactive Fe-N-C and graphite-N sites, the optimization of pore structure and the enhancement of graphitization allow 5% Fe-NC to achieve excellent ORR catalytic performance beyond that of commercial 20% Pt/C.

The introduction of Mn component improves the selectivity of NO adsorption separation in simulated flue gas of Co‐MOF‐74 at ambient conditions

Synthesized of bimetallic Mn0.17Co0.83‐MOF‐74 via the solvent‐thermal method, which retained the same structure as that of monometallic MOF‐74, and the two metals were uniformly dispersed in the crystals of Mn0.17Co0.83‐MOF‐74. The introduction of Mn gave the Mn0.17Co0.83‐MOF‐74 a higher pore number than the monometallic MOF‐74, exposing more accessible metal active sites, and the in situ IR demonstrated that NO adsorption on Mn0.17Co0.83‐MOF‐74 was modelled as the linear adsorption of metal‐centred Co (II)⸱⸱⸱NO and Mn (II)⸱⸱⸱NO, with strong interactions of adsorbed NO with both metal sites, suggesting that the introduction of Mn provided new accessible metal adsorption sites for NO that increased the adsorption of NO. The NO adsorption capacity of bimetallic Mn0.17Co0.83‐MOF‐74 was significantly increased to 160.3 cc.g−1 at ambient conditions, and the adsorption selectivity of NO/CO2 achieved 397, which was 37% higher than monometallic Co‐MOF‐74, and 214% higher than Mn‐MOF‐74 at low pressure. Furthermore, when exposed to a simulated mixed atmosphere, the Mn0.17Co0.83‐MOF‐74 exhibited a NO/CO2 adsorption selectivity of 35.5 and demonstrated favourable recyclability. These findings indicated that the bimetallic Mn0.17Co0.83‐MOF‐74 outperforms traditional materials in the adsorption separation of flue gas NO, positioning it as a material of choice in this field.

Dynamic Evolution of Coal Pore-Fracture Structure and Its Fractal Characteristics under the Action of Salty Solution

The instability and failure of coal pillars is one of the important factors leading to the catastrophic consequences of coal mine goaf collapse. Coal mine water has the characteristics of high salinity. Long-term mine water erosion can easily deform the coal pillar structure, eventually leading to instability and damage. This study carried out tests on coal samples soaked in salt solutions with different concentrations, and the nuclear magnetic resonance (NMR) method was used to obtain the dynamic evolution of the pore-fracture structure of coal. On the basis of fractal theory, the changes in fractal dimension of pore structure during the soaking process were discussed. The damage variable based on the pore fractal dimension was defined and the evolution relationship between the damage variable and immersion time was characterized. The findings demonstrated that the porosity change rate has an exponentially increasing relationship with the immersion time, and with the increasement of concentration of salt solution, the porosity change rate also shows increasing trends. The number of seepage pores and total pores increased with the immersion time. While, with the extension of soaking time, the number of adsorption pores first increased and then decreased. The connectivity between pores was enhanced. The relationship between the fractal dimension and the immersion time is linearly decreasing. The damage variable showed an increasing trend with the immersion time. As the concentration of salt solution increased, the damage of coal increased. The research results are of great significance for rationally evaluating the stability of coal pillars and ensuring the safe operation of underground engineering.

Coarse-Grained Monte Carlo Simulations with Octree Cells for Geopolymer Nucleation at Different pH Values.

Geopolymers offer a potential alternative to ordinary Portland cement owing to their performance in mechanical and thermal properties, as well as environmental benefits stemming from a reduced carbon footprint. This paper endeavors to build upon prior atomistic computational work delving deeper into the intricate relationship between pH levels and the resulting material's properties, including pore size distribution, geopolymer nucleate cluster dimensions, total system energy, and monomer poly-condensation behavior. Coarse-grained Monte Carlo (CGMC) simulation inputs include tetrahedral geometry and binding energy parameters derived from DFT simulations for aluminate and silicate monomers. Elevated pH values may can alter reactivity and phase stability, or, in the structural concrete application, may passivate the embedded steel reinforcement. Thus, we examine the effects of pH values set at 11, 12, and 13 (based on silicate speciation chemistry), investigating their respective contributions to the nucleation of geopolymers. To simulate a larger system to obtain representative results, we propose the numerical implementation of an Octree cell. Finally, we further digitize the resulting expanded structure to ascertain pore size distribution, facilitating a comparative analysis. The novelty of this study is underscored by its expansion in both system size, more accurate monomer representation, and pH range when compared to previous CGMC simulation approaches. The results unveil a discernible correlation between the number of clusters and pores under specific pH levels. This links geopolymerization mechanisms under varying pH conditions to the resulting chemical properties and final structural state.

Machine Learning-Assisted Characterization of Pore-Induced Variability in Mechanical Response of Additively Manufactured Components

Manufacturing defects, such as porosity and inclusions, can significantly compromise the structural integrity and performance of additively manufactured parts by acting as stress concentrators and potential initiation sites for failure. This paper investigates the effects of pore system morphology (number of pores, total volume, volume fraction, and standard deviation of size of pores) on the material response of additively manufactured Ti6Al4V specimens under a shear–compression stress state. An automatic approach for finite element simulations, using the J2 plasticity model, was utilized on a shear–compression specimen with artificial pores of varying characteristics to generate the dataset. An artificial neural network (ANN) surrogate model was developed to predict peak force and failure displacement of specimens with different pore attributes. The ANN demonstrated effective prediction capabilities, offering insights into the importance of individual input variables on mechanical performance of additively manufactured parts. Additionally, a sensitivity analysis using the Garson equation was performed to identify the most influential parameters affecting the material’s behaviour. It was observed that materials with more uniform pore sizes exhibit better mechanical properties than those with a wider size distribution. Overall, the study contributes to a better understanding of the interplay between pore characteristics and material response, providing better defect-aware design and property–porosity linkage in additive manufacturing processes.

Diagenetic evolution of tight sandstone and the formation of an effective reservoir in the lower member 3 of the Shahejie Formation, Bohai Bay Basin, East China

Heterogeneity in the physical properties of tight sandstones is mainly caused by complex diagenetic interactions in various combinations during the burial process. The tight sandstone oil in the Linnan Sag of Bohai Bay Basin has great development potential but it is unclear how effective reservoirs were formed, and this is a significant reason why exploration in the deep reservoir is so difficult. Here we studied the diagenetic evolution of the tight sandstone of Lower Member 3 of the Shahejie Formation, Linnan Sag, Bohai Bay Basin, by using cores, thin sections, XRD, SEM, grain-size analysis, high-pressure mercury intrusion porosimetry, fluid inclusions, and carbon and oxygen stable isotopes. Compaction, replacement, cementation and dissolution diagenesis are identified; all four processes mainly occur in the A phase of mesodiagenesis. The interaction of formation burial, thermal evolution of organic matter and dehydration of gypsum leads to the alternating presence of three stages of alkaline fluids and two stages of acidic fluids. The average dissolution porosity of the dissolution sandstone facies is greater than the lower limit of the porosity for the effective reservoir in the study area, which is key to the formation of effective reservoirs. By determining differential diagenetic evolution sequences of tight sandstone reservoirs under the constraints of different lithologies where sandstone is interbedded with mudstone, we are able to elucidate the formation of the effective reservoir as follows: (1) In the eodiagenetic stage, a large amount of early carbonate cement developed in the sandstone adjacent to the mudstone, filling the primary pores and forming a cementation sandstone facies. Smaller amounts of early carbonate cement developed in the interior of the sandstone, which “fixed” the primary pores, and has a positive effect on the formation of a large number of secondary pores in the dissolution stage. (2) In the early stage of mesodiagenesis (A1), due to the filling of primary pores, it is difficult for acidic fluids to enter the cementation sandstone facies adjacent to mudstone, and the dissolution is weak. But dissolution within the sand body was strong, producing a large number of dissolution pores and forming a dissolution sandstone facies that clearly enhanced the physical properties. (3) In a second early stage of mesodiagenesis (A2), dissolution still played a dominant role in the dissolution sandstone facies, due to the development of dissolution pores in the previous stage (it is easy for acidic fluids to enter the dissolution sandstone facies). The physical properties of the dissolution sandstone facies were once again enhanced and an effective reservoir gradually began to form. (4) At the end of mesodiagenesis stages A1 and A2 (26.2–24.6 Ma; 7.5–2.8 Ma), the reservoir experienced two phases of petroleum charging. The charging of the cementation sandstone facies developed at the margins of the sandstones was difficult due to the filling of primary pores. The dissolution sandstone facies are oil-bearing, with higher porosity, which indicates an effective reservoir. By coupling the thermal evolution of organic matter and the dehydration of gypsum with differential diagenetic evolution and the porosity evolution of reservoir, we are able to establish a reservoir genetic model that involves alternating seepage of organic acids and alkaline brines.

Degradation behavior and ageing mechanism of E-glass fiber reinforced epoxy resin composite pipes under accelerated thermal ageing conditions

In this work, accelerated ageing experiments with circulating air and simulated oilfield water were carried out at 95 °C on aromatic amine-cured GFRP pipes used in oilfield environments, with effective ageing times of 5000 h and 3000 h respectively. The differences in ageing behavior and ageing mechanisms of the GFRP tubes at different times under the two conditions were then analyzed and discussed. The changes in the apparent morphology and microstructure of the samples after thermal ageing were first observed using optical microscopy and scanning electron microscopy, and the results demonstrated that the thermal oxygen environment triggered more drastic color changes and obvious oxidation layers. The resin matrix manifests a large number of nano-scale micropores and modest matrix shrinkage pores in the micron size range, this is accompanied by damage to the fiber cross-section. Hydrothermal ageing causes further dissolution of the surface resin and dissolution of the exposed fibers. ATR-FTIR analysis verifies the increase in CO bonding of the ester group during thermal oxidation and the decreasing strength of the C–O–C and C–H bonds, while the behavior of ageing water absorption and glass fiber hydrolysis is illustrated by changes in the intensity of the –OH and Si–O characteristic bands. NMR hydrogen spectroscopy verified the formation of amides, methyl ethers and carboxylic acids in the thermal oxidation products of epoxy resins. Furthermore, the decay pattern of the circumferential tensile strength indicates that the hydrothermal environment has a more significant effect on the mechanical properties of GFRP pipes, which is attributed to the physical dissolution of the surface resin, significant hydrolytic damage to the surface exposed fibers, and the combined damage to the resin-fiber interfacial bonding by chloride ions in simulated oilfield water.