Medium Pore Research Articles

Retention properties and mechanism of agricultural waste maize whisker on atmospheric mercury

Mercury (Hg) is a global pollutant transmitted mainly through the atmosphere, posing a serious threat to biological survival and human health. Porous materials, with high specific surface area, high porosity, and high adsorption, are particularly suitable for the purification of atmospheric Hg mixtures. However, plant porous materials are rarely directly used for atmospheric Hg purification. In this study, the properties and mechanism of maize whisker in removing atmospheric Hg were analyzed. The results show that the Hg content in the whiskers increases significantly as the initial Hg concentration increases, and 79.38% Hg can be removed by 0.2 g maize whiskers after 1 h exposure when the initial Hg concentration is 0.1 μg m−3, indicating that maize whiskers can accumulate atmospheric Hg rapidly and effectively. The hole diameter of the maize whisker is between 0.83 and 3.06 μm, which is suitable for the adsorption of small substances. Correlation analysis shows that maize whiskers have a significant correlation between atmospheric Hg retention and its specific surface area, pore size, medium pore ratio, and micropore ratio, suggesting that the maize whisker hole feature has a significant influence on its ability to retain atmospheric Hg. Compared with the energy profiles before and after Hg treatment, the peak of Mg decreased after Hg adsorption. Fourier infrared spectrometer analysis suggests that functional groups such as -OH, -COOH, and -O- are involved in the adsorption process. The change in pH value shows an obvious effect on the overall change in zeta potential in the adsorption process. Therefore, a variety of mechanisms, including physical adsorption, electrostatic adsorption, complexation, chelation, and ion exchange, are involved in Hg retention with the maize whisker. This study reveals the important potential value of agricultural waste maize whiskers in the purification of atmospheric heavy metal Hg.Graphical

Study of microscopic imbibition and formation plugging mechanism of the compact oil reservoir based on SEM and NMR analysis

Unconventional reservoirs, such as compact reservoirs, have been extensively developed. The Changqing Oilfield is currently the largest compact reservoir oilfield in China. An effective method for developing compact reservoirs using hydraulic fracturing for reservoir modification is required. Some wells exhibited small production increases after fracturing, and some showed reductions in production. The impact mechanism of the fracturing fluid on the reservoir remains unclear. We used nuclear magnetic resonance (NMR) analysis and scanning electron microscopy (SEM) to investigate the utilization of a nano-micropore fluid and the surface morphology of the matrix during imbibition after fracturing. The results indicated polymer adhesion on the rock wall after the imbibition. The capillary force and the soaking pressure were the dominant driving forces during the imbibition. The capillary force was dominant in the small pores, and the soaking pressure had a larger influence on the fluid utilization of the large pores. The medium pores exhibited more significant solid phase damage, and the fluid utilization degree was relatively low. This study clarifies the impact mechanism of the fracturing fluid on the reservoir and the imbibition mechanism of slickwater. The results provide theoretical support and a scientific basis for optimizing fracturing, flowback methods, and post-fracturing stimulation in compact reservoirs.

Mechanical properties and meso-structure of concrete under the interaction between basalt fiber and polymer

Insufficient adhesion of the fibers to the concrete matrix causes the fibers to be pulled out under load, making the fiber concrete unable to meet the support requirements of deep roadways. Basalt fiber (BF) and polymers were selected for the design of mechanical experiments and studied using CT scanning, scanning electron microscopy (SEM) and discrete element simulation. The results show that the fiber mainly affects the compressive and flexural strength of concrete, and the polymer has an effect on the splitting tensile strength of the fibers. From the fine viewpoint, the increase in BF admixture resulted in the conversion of medium pores to small pores within the concrete. Incorporation of polymers results in a smooth polymer film inside the concrete matrix and more hydration products on the surface of the BF to enhance the adhesion of the BF to the concrete matrix. In the discrete element simulation, the fracture evolution can be divided into three stages and the angle of the microscopic fracture is mainly distributed in the range of 60°∼130°. Under loading, BF shares the stress of the matrix and presents itself as a tensile force at its tip, and the increase in BF doping improves the integrity of the specimen at damage.

Basic consolidation and impermeability laws for nano-silica-sol grouted mudstone

The engineering characteristic of the water absorption, swelling, softening, and disintegration of muddy soft rocks can cause long-term large deformation and instability in muddy tunnels. Due to the poor injectability of conventional cement slurry into rock microcracks and insufficient reinforcement and anti-seepage effects on mudstone, this research performed tests on the modification and reinforcement with silica sol. Taking nano-silica sol as the research subject, this study analyzed the injectability of the slurry, the anti-seepage performance of the gel, and the macro and micro characteristics of the pore closure of consolidated mudstone. Ultimately, the basic laws of silica sol grouting and anti-seepage reinforcement for mudstone are obtained. Besides, the impact of silica sol consolidation on grouting is examined, with its performance being compared with traditional slurries. Research indicates that the silica sol slurry exhibits superior injectability and permeability, with its gel demonstrating enduring volume stability and a compact structure. When applied to mudstone, silica sol grouting markedly diminishes both porosity (by 1.68–1.88%) and permeability, reaching an ultra-low level of 10-9 cm/s. NMR tests further elucidate that silica sol is more efficacious in sealing medium and large pores (with T2 > 10 ms, >0.1 μm) compared to smaller ones (with T2 < 10 ms, below 0.1 μm). Therefore, silica sol is a prime candidate for grouting and sealing applications in micro-cracked mudstones of coal mine tunnels, particularly in muddy tunnel projects necessitating extended maintenance and anti-seepage measures. The research is expected to provide solutions to the anti-seepage and reinforcement of mudstone.

The Characteristics of Fracturing Fluid Distribution after Fracturing and Shut-In Time Optimization in Unconventional Reservoirs Using NMR

Post-fracturing shut-in, as an important means of improving the energy efficiency of fracturing fluid, has been widely used in the development process of unconventional reservoirs. The determination of the shut-in duration is key to the effectiveness of shut-in measures. However, the distribution characteristics of the fracturing fluid during the post-fracturing shut-in period in unconventional reservoirs, such as the Chang 7 reservoir, were not clear, and the shut-in duration needed further optimization. Therefore, this paper employed low-field nuclear magnetic resonance (NMR) technology to study the distribution characteristics of the fracturing fluid during the post-fracturing shut-in period in unconventional reservoirs and optimized the shut-in duration. The study showed that the Chang 7 reservoir had a complex pore structure and relatively low porosity and permeability. During the shut-in process, the filtrate was distributed in pore throats with radii ranging from 0.0012 μm to 0.025 μm. Pore throats with radii ranging from 0.003 μm to 0.07 μm acted as dynamic pore throats in the process of imbibition displacement. When the shut-in duration for the Chang 7 segment was 7 days, the growth rate of the retained volume of fracturing fluid filtrate was the highest. When the shut-in duration was 10 days, there was no oil displacement in the medium and large pores, and the retained volume of filtrate was lower than that at 7 days shut-in, indicating that an optimal shut-in duration would be 7 days. This study can provide theoretical and technical support for the development of unconventional reservoirs.

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

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

Experimental Study on Pore Structure and Soil-Water Characteristic Curve of Ionic Rare Earth Ore under Seepage

The ionic rare earth (RE) ore body undergoes particle transport and pore structure change during the leaching process, resulting in "uneven percolation, preferential channel, leaching blind area," and other problems, leading to structural changes in the ore body, low leaching efficiency, and waste of resources. The unsaturated infiltration process is also the key stage that causes these problems. The initial pore structure evolution of the ore body plays a decisive role in the permeability coefficient of the ore body, and the direct influencing factor of the permeability coefficient is the distribution of the pore radius. We carried out research through indoor simulated leaching, the filter paper method for determining matrix suction, and nuclear magnetic resonance (NMR) testing. An ionic rare earth ore soil-water characteristic curve within a large matrix suction range was obtained by the filter paper method. With the increase in volumetric water content, the matrix suction presents a sharp downward trend. When the volumetric water content is less than 20%, this rule is particularly obvious. With the increase in matrix suction, the thickness of the adsorbed water film on the particle surface and pore radius show a decreasing power function trend. Under percolation, the porosity of an ionic rare earth ore sample tends to increase linearly with the increase in volumetric water content during the process from non-saturation to saturation; the porosity of a saturated ore sample after seepage expanded by 17.5 times compared to that of an unsaturated ore sample before seepage. The change rule of the internal microstructure of the ore sample is reflected in the gradual disappearance of micro pores and the gradual formation of small, medium, large, and mega pores, which shows a gradual increase trend. In the pore radius distribution, the more large and medium pores, the larger the permeability coefficient; the more micro and small pores, the smaller the permeability coefficient. For some ore bodies with poor permeability, the ore body is infiltrated with clear water under small water pressure before leaching with a leaching solution, which can improve the permeability of the ore body, effectively improve the efficiency of rare earth leaching, and increase the economic benefits.

Scaling Mechanism and Permeability Evolution of Sandstone Reservoir

Knowledge of scaling mechanisms and the permeable behavior of rocks is highly important for geothermal energy development. In this study, the sandstone was soaked in a solution with the same chemical composition as geothermal water in Linyi City, Shandong Province. Permeability tests, scanning electron microscope tests, and nuclear magnetic resonance tests were performed on sandstone samples after different soak times (0, 30, 60, and 90 days) and temperatures (25 and 85 °C) to characterize the changes in microstructure and permeability properties. In addition, the changes in ion concentration in chemical solutions were compared. The results show that the wet mass and porosity of sandstone increase with the increase of soak time (0-70 d), and then entered the stable periods (70-90 d). As the soaking time, the medium and large pores inside the sandstone are transformed into small pores. The permeability of sandstone shows an overall decreasing trend, with the maximum decline when the soaking time is 30 d. At 25 °C, the scaling behavior is mainly involved by Ca2+, but at 85 °C Mg2+ is also involved in the scaling behavior. The scaling mechanism becomes the joint participation of Ca2+ and Mg2+. The results of the PHREEQC simulations are almost the same as the laboratory test results, indicating that sodium feldspar, potassium feldspar, and chlorite are generated slowly during the fouling process.

Pore evolution and shear characteristics of a soil-rock mixture upon freeze-thaw cycling

The changes in pore structure within soil-rock mixtures under freeze-thaw cycles in cold regions result in strength deterioration, leading to instability and slope failure. However, the existing studies mainly provided qualitative analysis of the changes in pore or strength of soil-rock mixture under freeze-thaw cycles. In contrast, few studies focused on the quantitative evaluation of pore change and the relationship between the freeze-thaw strength deterioration and pore change of soil-rock mixture. This study aims to explore the correlation between the micro-pore evolution characteristics and macro-mechanics of a soil-rock mixture after frequent freeze-thaw cycles during the construction and subsequent operation in a permafrost region. The pore characteristics of remolded soil samples with different rock contents (i.e., 25%, 35%, 45%, and 55%) subjected to various freeze-thaw cycles (i.e., 0, 1, 3, 6, and 10) were quantitatively analyzed using nuclear magnetic resonance (NMR). Shear tests of soil-rock samples under different normal pressures were carried out simultaneously to explore the correlation between the soil strength changes and pore characteristics. The results indicate that with an increase in the number of freeze-thaw cycles, the cohesion of the soil-rock mixture generally decreases first, then increases, and finally decreases; however, the internal friction angle shows no apparent change. With the increase in rock content, the peak shear strength of the soil-rock mixture rises first and then decreases and peaks when the rock content is at 45%. When the rock content remains constant, as the number of freeze-thaw cycles rises, the shear strength of the sample reaches its peak after three freeze-thaw cycles. Studies have shown that with an increase in freeze-thaw cycles, the medium and large pores develop rapidly, especially for pores with a size of 0.2–20 μm. Freeze-thaw cycling affects the internal pores of the soil-rock mixture by altering its skeleton and, therefore, impacts its macro-mechanical characteristics.

Harnessing nanofiber alignment and pore size to promote stem cell self-renewal and differentiation

Stem cell therapy holds immense potential for regenerative medicine, but its applications are limited due to the loss of pluripotency during in vitro expansion. One promising approach to regulate stem cells is through nanotopographies, such as nanofibers. This study reveals that the arrangement of electrospun fibers aligns with the distribution and strength of the electric field through both experimentation and simulation. An electrospinning collector is thus designed to produce nanofibrous membranes with defined alignment and pore size. The cell study shows that randomly oriented nanofibers with small pores promote self-renewal and adipogenic and osteogenic differentiation of human mesenchymal stem cells. Conversely, aligned mesh membrane, particularly those with medium pores, decreases cell proliferation, stemness, and differentiation potential by elongating the cells. Furthermore, our study suggests that stem cell behavior is sensitive to the nanofiber structure, which offers a potential direction in promoting stem cell expansion efficacy.

Microstructural changes in building materials after various consolidation treatments studied by small-angle neutron scattering, mercury intrusion porosimetry and scanning electron microscopy

Stone or rendered facades of historical buildings often encounter loss of cohesion after long-term weathering. Specialist consolidating agents containing nanoparticles which can penetrate the degraded layer are used to extend the lifetime of such facades. Clay mortar prepared in the laboratory was used in the present study as a material for testing the effectiveness of several consolidating agents. Changes in porosity after treatment of the sample layers were assessed using small-angle neutron scattering, mercury intrusion porosimetry and scanning electron microscopy techniques. The scattering differed for the various samples, mainly in the medium range of scattering vector magnitudes. The cause of the scattering was ascribed to three populations of pores: large (micrometres), medium-sized (thousands of ångströms) and small (hundreds of ångströms). While the non-treated sample and the sample treated with a silicic acid ester-based product do not exhibit significant differences, the sample treated with a nano-lime suspension shows a decrease of 16% in the volume fraction of medium-sized pores. A difference was also observed in the sample treated with a dihydrogen ammonium phosphate solution: the size of the medium pores increased while their volume fraction decreased, and a change in the large pores was observed. The modelled small pores remained unaffected by the consolidating treatment.

Effect of Freeze–Thaw Cycles and Initial Water Content on the Pore Structure and Mechanical Properties of Loess in Northern Shaanxi

Spalling disease caused by freeze–thaw cycles often occurs on the loess cut-slopes in northern Shaanxi. The deterioration of the pore structure and mechanical strength of loess under a freeze–thaw environment is one of the critical reasons underlying the occurrence of spalling disease in the slopes. In order to explore the effects of freeze–thaw cycles on the pore structure and the mechanical strength of loess, four initial water contents (7%, 9%, 12%, and 14%) and six freeze–thaw cycles (zero, one, three, five, 10, and 20) were considered in this study. Nuclear magnetic resonance (NMR) and triaxial compression tests were carried out to analyze and reveal the mechanisms of effect causing the deterioration of the soil strength that affects the stability of loess cut-slopes. The results showed that the porosity growth increased with the initial water content and continued to increase during the freeze–thaw process until a later stage of the freeze–thaw cycle, when it gradually stabilized. The stress–strain curves were primarily influenced by the number of freeze–thaw cycles, the initial water content of the samples, and the confining pressure. Both the cohesion and the internal friction angle exhibited a decay law that showed a significant decrease, then a slow decrease, and finally stabilization during the freeze–thaw process. Small and micropores were predominant among the pore structures of the loess, while medium pores were the second most common, and large pores were the least common. With the increase in the initial water content, the pores transformed from micropore structures to medium and large pore structures. The soil strength deterioration was primarily driven by the phase changes of the pore water, as well as the water migration during the freeze–thaw process. This study will be beneficial for identifying the characteristics and types of freeze–thaw disease in cut-slope engineering in seasonally frozen loess areas and providing a theoretical reference and design basis for achieving green and sustainable development in slope engineering, management, and maintenance.

Comparative Study between Different Oil Production Enhancement Scenarios in an Iraqi Tight Oil Reservoir

This paper presents a comparative study between different oil production enhancement scenarios in the Saadi tight oil reservoir located in the Halfaya Iraqi oil field. The reservoir exhibits poor petrophysical characteristics, including medium pore size, low permeability (reaching zero in some areas), and high porosity of up to 25%. Previous stimulation techniques such as acid fracturing and matrix acidizing have yielded low oil production in this reservoir. Therefore, the feasibility of hydraulic fracturing stimulation and/or horizontal well drilling scenarios was assessed to increase the production rate. While horizontal drilling and hydraulic fracturing can improve well performance, they come with high costs, often accounting for up to 100% of the total well cost. To ensure economically viable flow rates and achieve maximum ultimate oil recovery, a technical and economic comparative study was conducted. The results indicate that hydraulic fracturing offers promising outcomes, with a total oil production of 153,816 Mbbl over 30 years from 25 fractured wells, resulting in a final Net Present Value (NPV) of 3,583.32 MM$. In contrast, the planned two horizontal wells exhibit lower eventual production and NPV compared to the majority of fractured wells. However, the 2000 m lateral section of well HF00Y-S00YH shows a slightly higher NPV. Considering the operational benefits and profitability, hydraulic fracturing should be seriously considered for the further development of the Saadi reservoir. This comparative study provides valuable insights into the most effective approach for enhancing oil production in tight reservoirs like Saadi, balancing the technical feasibility and economic viability of different stimulation scenarios. The findings can guide decision-making processes and contribute to maximizing oil recovery in similar challenging reservoirs.

Enhanced recovery of tight reservoirs after fracturing by natural gas huff-n-puff: Underlying mechanisms and influential factors

Tight oil resources are abundant in the world. It is very important to strengthen the research on the development theory and technology of tight oil reservoirs for ensuring national energy security. Natural gas huff-n-puff can effectively improve the oil recovery of tight oil reservoirs. However, the pore-scale oil production characteristics and the mechanisms of natural gas huff-n-puff in matrix-fracture cores are poorly understood. The influence degree of important factors on oil recovery is not clear and the interactions between factors are rarely considered. In this paper, the oil production characteristics and mechanisms of natural gas huff-n-puff in tight cores with different fracture lengths were quantitatively analyzed by combining nuclear magnetic resonance (NMR) with numerical simulation technology. The influencing factors and their interactions were evaluated by the response surface method (RSM). The results show that tight cores mainly consist of medium pores (0.1–1 μm) and small pores (0.01–0.1 μm). The fracture mainly increases the proportion of macro-pores (1–10 μm) and medium pores. In the natural gas huff-n-puff process, crude oil from macro-pores (1–10 μm) and medium pores is mainly developed, and the contribution percentage of crude oil in medium pores to oil recovery is the largest, up to 98.28%. The position of gas–oil contact (GOC) moves deeper as the number of huff-n-puff cycles increases. The contents of CH4 and CO2 in the oil phase remain at a high level within the GOC, while between the GOC and the component sweep front, the contents of CH4 and CO2 in the oil phase decrease with the increase in dimensionless distance. The gas component sweep volume is increasing with the increase in fracture length. Moreover, the injected natural gas mainly extracts C3–C10 components from crude oil. The reduction law of crude oil viscosity is consistent with the migration laws of CH4 components along the path. Compared with soaking time and gas diffusion coefficient, the injection pressure is the most significant factor underlying the recovery of natural gas huff-n-puff in tight cores. Besides the influence of single-factor, the interaction effects of gas injection pressure and diffusion also should be considered to determine the huff-n-puff parameters in the field implementation of natural gas huff-n-puff in tight reservoirs after fracturing.

Analysis of mortars with old plastering waste using state-of-the-art method: nuclear magnetic resonance

One of the major problems we face today is the correct management of waste generated in all spheres of activity. Thus, the concept of sustainable development aims to develop strategies that prevent and solve problems already generated. Domain construction is the one that generates the most waste worldwide, according to recent studies, which requires the imposition of clear, effective, and future-proof measures to improve the environment and the health of the population. This paper is the continuation of a research program in which 3 types of mortar recipes are analyzed. The study involves replacement of aggregates, in different percentages (10% and 15%), with plaster waste from historic buildings. The obtained results show that the values fall within the limits stipulated in the norms in force, so the study will continue with the analysis of the samples using the state-of-the-art method: nuclear magnetic resonance. The paper aims to analyze the properties of the proposed mortars at the nanoscopic level, following the relationship between the plaster mortar matrix and the plaster waste introduced in different percentages in the samples. In addition, the impact of these wastes on the hydration of the cement and on the porosity of the composition of these mortars is also observed, being noticed that the relationship between the porosity of the samples and the mechanical resistances is inversely proportional, that is, the resistances decrease as the porosity increases. It will also be identified the location of hydrogen in the structure: in hydrated mineralogical compounds of cement and in large, medium and small pores. For each studied sample, the investigations were conducted at the age of 7, 14 and 28 days (even at 3 days for samples with 10% and 15% substitution of aggregates with old plastering mortars). The results for the proposed samples will be compared to the standard recipe.

Interpretation of Petrophysical Properties in Reservoir Rock Using Capillary Pressure Data of the Mishrif Formation in West Qurna Oilfield, Southern Iraq

In this study, capillary pressure tests for twenty-nine samples acquired from four wells, (Rn-83, WQ-155, WQ286, and WQ-355) were used to estimate pore size distribution, pore-throat sorting, displacement pressure, reservoir grade, oil column, effective porosity, and relative permeability of the Mishrif Formation at West Qurna Oilfield, southern Iraq. Interpretation of capillary pressure data revealed that the formation can be divided into four reservoir facies with different reservoir production performances: very good, good, medium, and poor. The facies with very good performance is characterized by large pore sizes, excellent reservoir grade, low displacement pressure, and high oil saturations. The good facies is characterized by the presence of good pore throat sorting, good reservoir grade, and good porosity. Contrary, Medium-performance reservoir facies are characterized by the presence of medium pore sizes, medium pore throat sorting, and medium reservoir grade. Poorly performing reservoir facies is characterized by small pore size, high displacement pressure, poor throat sorting, and high water saturation levels. Based on the relative permeability calculations some samples are wet with water (water-wet), while others are wet with oil (oil-wet).

Experimental study on the plugging and profile control of preformed particle gels in high temperature and salinity reservoir

AbstractA novel modified polysaccharide composite preformed particle gel (MCPG) was synthesized as a profile control agent to improve the situation of high water cut and low oil recovery. Then, the structure of MCPG was characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and environmental scanning electron microscope (ESEM). Subsequently, the impact of MCPG on enhanced oil recovery was investigated through nuclear magnetic resonance (NMR) and core displacement experiments. The results of FTIR, XRD, and ESEM indicate that monomers have been successfully intercalated into the layered structure of nanoscale sodium bentonite. In the condition of 130°C and salinity of 240,000 mg/L, the value of the swelling ratio and the toughness factor can reach about 30 and 0.87, respectively. The results of nonlinear fitting indicate that the relationship between the resistance coefficient and residual resistance coefficient with the matching coefficient (β) followed a power function, while the blocking water efficiency with β followed an exponential function. When the permeability ratio was as high as 30.58, MCPG still exhibited excellent profile improvement performance. NMR experiments proved that MCPG increased the displacement resistance in large pores and effectively enhanced the displacement efficiency in medium pores and small pores. The oil displacement efficiency in MCPG flooding and subsequent water flooding stages increased by 18.65% and 8.42%, respectively.

Biomineralization of coral sand by Bacillus thuringiensis isolated from a travertine cave

Travertine is a typical product of microbial mineralization in the nature and its mineral composition is mainly calcite and aragonite. In this paper, Bacillus thuringiensis, a kind of mineralize bacterium is extracted from the travertine crystal to cenment coral sand, and the reinforcement effect of microbial induced carbonate precipitation (MICP) technology on coral sand under different cementation times is studied. Firstly, the culture conditions are optimized in nine pairs of trials, including urea content, microbial inoculation, shaker speed and incubation time. Under the optimal culture conditions, the coral sand is cemented by soaking method. With the increase of reinforcement times, the permeability coefficient of the sand sample is reduced to 10−4 cm/s, and the shear strength is increased by more than 130%. Compared with Sporosarcina pasteurii, the cohesion and internal friction angle of the coral sand column cemented by Bacillus thuringiensis are increased by more than 50% and 10%, respectively. The area distribution of T2 spectrum shows that with the increase of the number of cementation, the amplitude of the main peak decreases, indicating that the large pores are better filled, the number of medium and small pores are also reduced, and the pore area is significantly reduced, with the amplitude of about 44%. The above experiments verified that microorganism in travertine could also be used in MICP technology, and even achieve better reinforcement effect. It also provides a new way and idea for the selection of mineralized bacteria by MICP technology.

Experimental study on water flooding mechanism in low permeability oil reservoirs based on nuclear magnetic resonance technology

Low permeability oil reservoirs are characterized by complex pore-throat structure and complex mechanism of oil and water storage and transmission. At present, the research on cross-scale characteristics of pore-throat structure in low permeability reservoirs needs to be strengthened, and the research on oil-water evolution characteristics needs to be improved. In this paper, based on NMR method, different “porosity-permeability-original oil saturation” coupling evaluation systems are constructed, the study on oil and water distribution characteristics at different water flooding stages has been carried out, and the distribution mechanism of residual oil in pores with different sizes is analyzed. It is found out that: (a) the higher the core permeability, the lower the displacement pressure; the lower the core permeability, the higher the displacement pressure. (b) The T2 spectrum shows that micropores, mesopores and macropores in core samples are well developed. (c) The morphology of T2 spectrum can be divided into three types: high right peak and low left peak, high left peak and low right peak, and basically equal left and right peaks. In addition, under saturated oil conditions, medium and large pores are the main oil storage spaces. (d) There are three factors affecting the water flooding efficiency: the influence of micro-fractures, the influence of pore-throat heterogeneity and the influence of the degree of producing pore-throat.

Alginate/acemannan-based beads loaded with a biocompatible ionic liquid as a bioactive delivery system

Combining biomacromolecules with green chemistry principles and clean technologies has proven to be an effective approach for drug delivery, providing a prolonged and sustained release of the encapsulated material. The current study investigates the potential of cholinium caffeate (Ch[Caffeate]), a phenolic-based biocompatible ionic liquid (Bio-IL) entrapped in alginate/acemannan beads, as a drug delivery system able to reduce local joint inflammation on osteoarthritis (OA) treatment. The synthesized Bio-IL has antioxidant and anti-inflammatory actions that, combined with biopolymers as 3D architectures, promote the entrapment and sustainable release of the bioactive molecules over time. The physicochemical and morphological characterization of the beads (ALC, ALAC0,5, ALAC1, and ALAC3, containing 0, 0.5, 1, and 3 %(w/v) of Ch[Caffeate], respectively) revealed a porous and interconnected structure, with medium pore sizes ranging from 209.16 to 221.30 μm, with a high swelling ability (up 2400 %). Ch[Caffeate] significantly improved the antioxidant activities of the constructs by 95 % and 97 % for ALAC1 and ALAC3, respectively, when compared to ALA (56 %). Besides, the structures provided the environment for ATDC5 cell proliferation, and cartilage-like ECM formation, supported by the increased GAGs in ALAC1 and ALAC3 formulations after 21 days. Further, the ability to block the secretion of pro-inflammatory cytokines (TNF-α and IL-6), from differentiated THP-1 was evidenced by ChAL-Ch[Caffeate] beads. These outcomes suggest that the established strategy based on using natural and bioactive macromolecules to develop 3D constructs has great potential to be used as therapeutic tools for patients with OA.