Permeability Characteristics Research Articles

Study of geomechanical properties of the Pimienta formation with undrained multi-stage triaxial tests, Central-Western Tampico Misantla Basin, Mexico

The Pimienta Formation (J-Pi) of the Tampico Misantla Basin (TMB) in Mexico is known for its potential as unconventional onshore hydrocarbon reserves. The area of interest in this study is located in the western-central part of the TMB, where no significant production has been established from unconventional resources. Given the low permeability and low porosity characteristics of the carbonaceous mudstone in the Pimienta formation, it is necessary to implement techniques to increase the area of flow from the reservoir to the borehole, achieving profitable oil and gas extraction.The geomechanical properties of rock strata are essential inputs for the design and implementation of shale oil and gas production engineering, such as horizontal drilling and hydraulic fracturing. Understanding the capabilities of the rock to yield and contain hydraulic fractures is essential to designing safe and efficient well stimulations. Likewise, the wellbore stability is of critical importance to the successful development of secondary and tertiary recovery systems.In this study, core samples from the Pimienta Formation in the TMB are analyzed through undrained multi-stage triaxial tests, emphasizing the estimated in-situ geo stresses and the effect of the mineral composition of the rock. The geomechanical parameters of compressional strength, Poisson ratio (PR), and Young's modulus of the Pimienta formation are obtained from the analysis of the experimental data and finding correlations to the mineral composition of the samples. A detailed characterization is completed under the conventional rock mechanics methodologies of Mohr-Coulomb and Hoek-Brown failure criterion, as well as Brittleness Index (BI).

Permeability anisotropy analysis of two-phase flow during hydrate dissociation process

Natural gas hydrate (NGH) is a versatile and energy source. But in the actual extraction process, NGH in the reservoir will be out of phase equilibrium conditions and dissociate. This will induce alterations in permeability characteristics of reservoir and will exert a significant influence on the assessment of hydrate reservoir capacity. In the research, an innovative CT triaxial system was used to obtain the micro-structure of sediment specimen during hydrate dissociation. The anisotropy of absolute permeability (k), capillary pressure (Pc) and relative permeability (kr) were also analyzed using the pore network model (PNM). As demonstrated by the results, k increases gradually in all three directions during the dissociation. Pc gradually decreases. The degree of anisotropy of both Pc and gas-water relative permeability (krg and krw) gradually decreases. The impact of hydrate dissociation on the kr anisotropy during primary gas flooding surpasses that observed during secondary water flooding. As hydrate saturation decreases, the krw increases and the krg decreases in the horizontal directions. The krw does not change significantly and the krg increases in the vertical direction. Along the length of the sample, the distribution of hydrate and pore space exhibits heterogeneity across the sections. This inhomogeneous distribution will lead to anisotropy in permeability.

Gas permeability characteristics of granite-manufactured sand concrete and its numerical simulation using NMR-MIP modified method

Natural sand resources are becoming increasingly scarce with the rapid development of infrastructure. Therefore, manufactured sand usage is inevitable. However, the significant differences in granite powder content between manufactured- and natural sand have a remarkable impact on the pore structure and permeability of cement-based materials, which are crucial for material durability. In this work, several granite powder dosages (0–32 %) of granite-manufactured sand were considered for preparing manufactured sand concrete, and a suitable physical filling model was chosen to quantify the material particle filling for characterizing the overall pore-filling effect. Mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) were used to examine the pore structure of the specimens. The quasi-stationary flow method was used to test the gas permeability of concrete. Finally, a random hierarchical bundle model using the NMR-MIP method is proposed to predict the gas permeability of cementitious materials based on their pore size distribution. The results show that granite-manufactured sand and an appropriate amount (i.e., 8 %) of granite powder can improve the filling effect and anti-permeability performance of concrete. There is a good correlation between the pore structure parameters and gas permeability, where the physico-mathematical relationships can be modeled. The maximum relative difference between the predicted and experimental values of the random tube bundle model was reduced to 30.93 % using the NMR-MIP method compared to 70.87 % with the traditional MIP method.

The 1st Hanrahan Lecture: Geotechnical properties of Irish glacial and interglacial soils

This paper reviews the current state of the art in relation to geotechnical design in unsorted till deposits, commonly called boulder clays by engineers or diamictons by geologists, generally taking the topics discussed by Professor Eamon Hanrahan in his seminal work of 1977 on Irish tills. These topics include the permeability, stiffness and consolidation characteristics of these deposits, together with their undrained and drained behaviour. The geological background to the deposition of these tills is discussed and the available information on the presence of interglacial soils around the country is presented. Where possible, practical experience from working with these deposits is compared with predictions made from field or laboratory test results: for example, in settlement assessment of foundations, slope stability and in earthworks. Whilst most of Ireland is covered with stony boulder clays, which is the main topic of this paper, the geotechnical parameters of a fine-grained till encountered on the east coast, known as Irish Sea Till or colloquially as Macamore Clay, are discussed and the implications of this on slope stability is investigated.

Mechanics and permeability properties of ecological concrete mixed with recycled engineering muck particles

The excavation of construction foundation pits, tunnels, channels, and other projects generates a significant volume of engineering muck, posing challenges in management. Prolonged accumulation of this muck can lead to environmental pollution. The effective recycling of this type of construction waste is crucial for the advancement of a circular economy, necessitating immediate attention to research and solutions. In this study, a novel method is introduced for the preparation of low-carbon and environmentally friendly ecological concrete. This method involves the utilization of recycled engineering muck particles to substitute a portion of the natural aggregate and enables the comprehensive recycling of engineering muck. Subsequently, the mechanical and permeability properties of ecological concrete under varying muck particle content and porosity conditions are analyzed through experiments, taking into account the impact of relative average pore diameter and pore tortuosity. A predictive model has been developed for the tortuosity of pore channels in ecological concrete, taking into account effective porosity and average pore diameter. The enhanced Kozney-Carman model is employed to describe the correlation between pore properties and hydraulic conductivity. The findings indicate that a composite curing agent is formed by combining ordinary Portland cement with a hydrophilic polyurethane solution. This composite curing agent demonstrates superior performance compared to pure cement in the solidification of engineering muck. As the replacement rate of unsintered recycled residue particles increases, the porosity of concrete may increase by up to 29.7 %. This results in enhanced permeability characteristics but a decrease in compressive strength. In contrast to lightweight aggregates manufactured through the sintering process, the carbon emissions of unsintered recycled residue particles are reduced by 57.7 %. This study provides suggestions for the repurposing of construction waste and contributes to the advancement of sustainable practices within the concrete production sector.

Effects of Different Reclamation Years and Modes on Soil Moisture Transport Pathways and Permeability Characteristics in an Open-Pit Mining Area in Guangxi

The microstructural characteristics of reclaimed soil in Guangxi’s bauxite mining area play a pivotal role in determining soil reclamation quality, yet they remain poorly understood. To explore the impact of varying reclamation years and modes on pore structure characteristics in this region, we selected four reclamation regions: grassland reclamation with 2 years (RG2a), grassland reclamation with 10 years (RG10a), bare ground reclamation with 2 years (RW2a) and bare ground reclamation with 10 years (RW10a). Utilizing X-ray CT technology, we scanned soil columns within a 30 cm depth to analyze pore distributions using Avizo 2020 software combined with ImageJ 1.53c and its plugins. The findings revealed a significant increase in the number of 2D and 3D macropores by 1.09% and 88.89% in RG10a compared to RG2a, as well as 39.01% and 13.33% in RG10a compared to RW10a, respectively. Furthermore, RG10a was observed to be more effective in enhancing the rounding rate of macropores and mesopores, as well as average branch length and density. Additionally, RG10a demonstrated a greater capacity to increase porosity and connectivity while reducing curvature and specific surface area among the three-dimensional parameters. The 3D reconstruction illustrated that RG modes exhibited a more abundant distribution of macropores compared to RW modes and 10a modes showed a higher presence of macropores than 2a modes, which displayed a tilted laminar pattern. Soil moisture movement simulations conducted through Avizo 2020 under various modes indicated that RG modes presented a more extensive capacity for vertical flow, while 10a modes displayed more abundant flow lines and a higher infiltration rate (K) compared to 2a modes. In conclusion, prolonged reclamation years favoring grassland reclamation modes could enhance water and nutrient transport pathways toward traditional agricultural soil.

Experimental study on vertical seepage of coarse-grained calcareous sand

Calcareous sand, a special geotechnical material employed as foundation fill in numerous reef constructions, exhibits susceptibility to seepage deformation in complex marine dynamic environments. Its permeability characteristics are notably distinct from conventional terrestrial soil, making the understanding of these properties critical for further applications. This study conducted vertical seepage tests on coarse-grained calcareous sand samples with varying coefficients of uniformity (Cu), coefficients of curvature (Cc), relative compactions (Dr), and soil skeletal structures. These tests utilized a custom-designed apparatus, supplemented with image binarization and particle image velocimetry techniques. Based on the results, the findings revealed a three-stage vertical seepage process: steady seepage, hydraulic adjustment, and seepage failure. The permeability coefficient k20 of the calcareous sand samples was observed to transition from a decreasing to an increasing trend with rising Cu and Cc values. Moreover, the k20 of tightly compacted and medium-tightly compacted samples exceeded that during the steady seepage stage upon entering the second stage, while the opposite holds true for relatively loose samples. The spatial organization of the sample skeleton had a considerable impact on its permeability, with coarse-grained calcareous sand imposing a greater constraint on fine particle migration compared to river sand.

STUDY OF HYDROGEN-HELIUM PERMEABILITY OF SILICATE MICROSPHERES AND SORBENT BASED ON THEM

The work is devoted to research on the applicability of the membrane-sorption method for the separation of hydrogen-helium mixtures. The sorption dependences of hydrogen and helium absorption were experimentally obtained for synthetic hollow microspheres made of sodium borosilicate glass of the MS-V-1L type, silica microspheres and granular sorbent based on MS-V-1L microspheres. A significant difference in the rates of sorption processes of hydrogen and helium for the sorbents under study was shown. Based on the gas diffusion model, the kinetic characteristics of absorption, permeability and selectivity coefficients, and dynamic characteristics of the processes of sorption of hydrogen and helium of heliumhydrogen mixtures of various compositions by these sorbents were determined. For silica microspheres, the selectivity coefficient with respect to hydrogen and helium at T = 24 C exceeds 130, and for a granular sorbent based on MS-V-1L microspheres it is about 1000 at T =110 C. The high selectivity values of the studied sorbents confirm the possibility and efficiency of using the membrane-sorption method for the separation of hydrogen-helium mixtures.

Permeability Prediction in Nonwoven Geotextiles Using Mathematical Modeling and Numerical Simulation

The vertical permeability coefficient is a pivotal hydraulic index of needle-punched nonwoven geotextiles. The accurate determination of the permeability coefficient is important for assessing engineering properties. This study employed mathematical modeling, numerical simulations, and physical experimentation to investigate the permeability behavior of nonwoven geotextiles. Mathematical modeling relies on the fiber and pore size characteristics of the geotextiles extracted through two-dimensional image analysis. The numerical simulation method was based on a pore network model acquired through three-dimensional image analysis. The results of the physical experiments served as benchmarks for evaluating the precision of the two methods. These findings underscore the efficacy of mathematical modeling and numerical simulation in predicting the permeability characteristics of nonwoven geotextiles.

Predicting permeability coefficient in soil-rock mixtures using parameters from the negative exponential continuous grading equation

Soil-rock mixtures (SRMs) are widely utilized for embankment filling of highways in mountainous areas. The permeability characteristics of SRMs must be investigated as mountain highways are often exposed to strands of rainwater subjected to extreme rainfall. For the same species of SRM, its permeability is determined by its pore distribution and grading characteristics, which can be considered as an expression of particle grading and pore parameters. The predictive model of the SRMs permeability coefficient encompassing gradation coefficients and porosity was proposed based on the negative exponential continuous gradation equation and the Kozeny–Carman model. The applicability of the prediction model was verified based on the existing literature and performing SRMs seepage tests. The findings indicated that the permeability coefficient formula for SRMs established on the particle grading parameters and porosity was reasonable. Nevertheless, its current applicability is limited to the prediction of permeability coefficients for continuously graded SRMs. Consequently, further investigation is required to assess the suitability of the model for intermittently graded SRMs.

Recent Advances in Water Treatment Membranes Based on Nanomaterials (A Review)

Nanomaterials have emerged as the next generation of materials for high-performance water treatment membranes, with the ability to address the global problem of pollution in water. Application of nanoparticles as membranes improves permeability feature for water, mechanical performance, efficiency of separation, and membrane fouling. As a result, the nanomaterials open up a new avenue for effectively selective membranes for purification of the water. This paper discusses the enhancements in membrane caused by the presence of various nanomaterials, such as nanoparticles (NPs), two-dimensional nano-materials (2D), nanofibers, nanosheets, and other nano-composite structure materials. Furthermore, the many uses of these membranes-based nanoparticles in treatment of water applications are emphasized. The goal is to show how important nanoparticles are in the membrane manufacturing in treatment of water. Nanomaterials and nanotechnology were discovered to have enormous promise for the progress of sustainable treatment of water and its wastes.

Investigation of pore structure evolution and damage characteristics of high temperature rocks subjected to liquid nitrogen cooling shock

Liquid nitrogen (LN2) can be utilized in the development of enhanced geothermal systems, as well as for deep/ultra-deep hydrocarbon reservoir stimulation, fire suppression, and other high-temperature geological projects. It is a crucial issue in the utilization of LN2 to investigate the pore structure evolution, permeability, and damage characteristics of high-temperature rocks under the influence of LN2 cooling shock. These rocks were first slowly heated to 150∼600°C and held for 2 h, followed by LN2 or natural cooling. The evolution of pore volume in high-temperature rocks affected by liquid nitrogen cooling was quantified. T2 cutoff values were determined through centrifugal tests, while the contents of irreducible and mobile fluids were estimated. Based on the aforementioned analysis as well as changes in irreducible fluid saturation, pore throat, tortuosity, and permeability, this study examines the closure and development of pores along with permeability behavior. The findings suggest that, despite a more pronounced decrease in porosity at lower heating temperatures, LN2 cooling specimens exhibit superior pore connectivity and permeability compared to those cooled naturally. LN2 stimulation not only induces crack initiation and propagation but also results in further cooling induced densification based on heating densification. 225°C is considered to be the optimal temperature for cooling contraction induced densification in this study. At higher heating temperatures, the damage to rock cooled with LN2 is more severe than that of naturally cooled. This results in a greater increase in porosity, movable fluid content and proportion, and permeability of LN2 cooled specimens compared to naturally cooled specimens. The damage mechanism can be better understood by the constructed damage model that coordinates the pore increase/decrease and mutual pore transformation from the perspective of pore evolution.

Fracture propagation morphology and parameter optimization design of pre-CO2 hybrid fracturing in shale oil reservoirs, Ordos Basin

Shale reservoirs typically exhibit the characteristics of large burial depth, low permeability, and well-developed bedding. Despite the implementation of water-based fracturing techniques with high displacement, attaining the optimal reservoir stimulation effect remains a formidable challenge. Consequently, in recent years, a novel method of hybrid fracturing method using pre-CO2 + sand-carrying slick water has been proposed. Within this framework, the meticulous design of fracturing operation parameters stands out as a pivotal factor influencing the efficacy of reservoir stimulation. This paper presents a coupled 3-D hydraulic fracture propagation model, investigating the influence of injection displacement, injection volume, and three-stage pre-injection fluid volume ratio on the fracture propagation. Two quantitative evaluation metrics, namely fracture surface area S and fracture transverse plane fractal dimension D, are precisely defined. Additionally, real-time analysis of bottom-hole pressure is conducted to further comprehend the dynamics of the process. Numerical investigations have revealed that both pre-CO2 injection displacement and volume exert a substantial influence on fracture half-length and complexity. Furthermore, the proportion of hybrid fracturing fluid demonstrates a notable impact on fracture height and complexity. The design of injection parameters does not exhibit a significant effect on the formation breakdown pressure. This study quantitatively evaluates fracture propagation under different working conditions from the perspective of fracture morphology, and serve as practical guidance for optimizing the process parameters design for hybrid fracturing in shale oil reservoirs, Ordos Basin.

Tight carbonate reservoir evaluation case study based on neural network assisted fracture identification and analytic hierarchy process

Comprehensive evaluation of reservoirs is an important link in gas reservoir exploration and development. The evaluation of tight carbonate reservoirs often focuses on the characteristics of porosity and permeability, ignoring the important factor of fractures, also the quantitative evaluation of reservoirs is relatively few. It is difficult to identify fractures and evaluate the reservoir factors qualitatively and quantitatively. Herein, the sedimentary microfacies and microporosity of the tight carbonate reservoir of the Ma55 submember in the eastern Sulige area are comprehensively studied by casting thin section, rock physical property, and capillary pressure test data. The backpropagation (BP) neural network algorithm is used to identify and predict fractures. Finally, through the analytic hierarchy process, the above reservoir influencing factors are modeled and quantitatively analyzed for reservoir evaluation. The results show that the highest probability of fracture development in the central and northwest areas of the study area can reach 0.92. The accuracy of the BP neural network model in identifying cracks can reach 80%, which is reliable and effective compared with the conventional logging identification method. Reservoirs can be classified into four types according to their quality. The synthetic weights of porosity, permeability and fracture development probability are 0.2, 0.2 and 0.216 respectively, which are the three most important evaluation parameters. This study improves the accuracy of fracture identification and prediction of tight reservoirs in comprehensive reservoir evaluation, which provides guidance and scheme for more detailed exploration and development of tight carbonate reservoirs.

Experimental Study on the Mechanical Strength, Deformation Behavior and Infiltration Characteristics of Coral Sand

In this investigation, coral sand is presented as a sustainable substitute for conventional river and machine-manufactured sand. This study comprehensively investigated the macro-scale strength, deformation, and permeability characteristics of coral sand, alongside analyzing the mechanical behavior, deformation, and permeability under various conditions and in relation to distinct particle characteristics. It revealed that coral sand primarily consists of biotite and high-Mg calcite, featuring abundant internal pore space. Its compressive properties resemble clayey soils, displaying minimal unloading rebound and predominant plastic deformation during compression. In direct shear tests, the stress–strain relationship follows an approximate hyperbola, with no pronounced strain softening. Describing particle fragmentation in the process proves challenging, making indicators like internal friction angle less applicable in engineering. Triaxial tests indicate a rapid initial bias stress increase, followed by a gradual decrease post-stress peak, suggesting a strain softening phenomenon. As surrounding pressure rises, the axial strain needed to reach peak strength also increases. The permeability coefficient of coral sand correlates linearly with pore ratio increase, represented by 10e. The complex interaction of multiple factors influences the strength, deformation, and permeability of coral sand blown fill mixes, with specimen porosity having the greatest impact. The design and construction of high-weight foundation elements in coral sand blown fill projects should consider porosity effects.

Research on Permeability Characteristics and Gradation of Rockfill Material Based on Machine Learning

The density of rockfill material is an important index to evaluate the quality of rockfill dams. It is of great significance to accurately obtain the densities and permeability coefficients of rockfill material dams quickly and accurately by scientific means. However, it takes a long time to measure the permeability coefficient of rockfill material in practice, which means that such measurements cannot fully reflect all the relevant properties. In this paper, using a convolutional neural network (CNN), a machine learning model was established to predict the permeability coefficient of rockfill material with the full scale (d10~d100), pore ratio, Cu, and Cc as the inputs and the permeability coefficient as the output. Through collecting the permeability coefficient and related data in the literature, the set samples were sorted for model training. The prediction results of the trained CNN model are compared with those of the back propagation (BP) model to verify the accuracy of the CNN model. Laboratory constant head penetration experiments were designed to verify the generalization performance of the model. The results show that compared with the BP model, the CNN model has better applicability to the prediction of the permeability coefficient of rockfill material and that the CNN can obtain better accuracy and meet the requirements of the rough estimation of rockfill materials’ permeability in engineering.

Programmable Enzymatic Reaction Network in Artificial Cell-Like Polymersomes.

The ability to precisely control in vitro enzymatic reactions in synthetic cells plays a crucial role in the bottom-up design of artificial cell models that can recapitulate the key cellular features and functions such as metabolism. However, integration of enzymatic reactions has been limited to bulk or microfluidic emulsions without a membrane, lacking the ability to design more sophisticated higher-order artificial cell communities for reconstituting spatiotemporal biological information at multiple length scales. Herein, droplet microfluidics is utilized to synthesize artificial cell-like polymersomes with distinct molecular permeability for spatiotemporal control of enzymatic reactions driven by external signals and fuels. The presence of a competing reverse enzymatic reaction that depletes the active substrates is shown to enable demonstration of fuel-driven formation of sub-microcompartments within polymersomes as well as realization of out-of-equilibrium systems. In addition, the different permeability characteristics of polymersome membranes are exploited to successfully construct a programmable enzymatic reaction network that mimics cellular communication within a heterogeneous cell community through selective molecular transport.

Influence of Structural Symmetry of Fault Zones on Fluid-Induced Fault Slips and Earthquakes

Subsurface fluid injection and extraction can reactivate faults and induce earthquakes. In current research, faults are typically described as symmetrical structures and the presence of asymmetric structures is often overlooked. The reality is that numerous asymmetric faults exist within the Earth’s crust. The architectural and permeability characteristics of fault zones differ significantly between symmetrical and asymmetrical faults. These differences may have a great influence on fault stability during fluid injection or extraction. In this study, the impact of fault zone structures on fluid-induced slips and seismic activity were investigated through numerical analysis. The findings indicated that symmetrical faults were more likely to induce larger slips and earthquakes during various subsurface fluid operations. For asymmetric faults, larger induced slips occurred when fluid was operated in a hanging wall reservoir than in a footwall reservoir. In symmetrical faults, the opposite was true. When evaluating the stability of a fault in subsurface fluid engineering, the fault structure and fluid pattern and their combined effects must be considered comprehensively.

Vienna Rectifier Modeling and Harmonic Coupling Analysis Based on Harmonic State-Space

Due to the high permeability characteristics of power electronic devices connected to the distribution grid, the potential harmonic coupling problem cannot be ignored. The Vienna rectifier is widely utilized in electric vehicle charging stations and uninterruptible power supply (UPS) systems due to its high power factor, adaptable control strategies, and low voltage stress on power switches. In this paper, the three-level Vienna rectifier is studied, and the harmonic state-space (HSS) method is used to model the rectifier. The proposed model can reflect the harmonic transfer characteristics between the AC current and the DC output voltage at various frequencies. Finally, the model’s accuracy and the corresponding harmonic characteristics analysis are further verified by simulation and experimental test results. The results show that the harmonic state-space modeling used for Vienna rectifiers can reflect the harmonic dynamics of the AC and DC sides, which can be used in stability analysis, control parameter design, and other related fields.

Performance of concrete produced with alkali-activated artificial aggregates

The excessive use of natural aggregates raises mining activity. Further, it leads to environmental damage, which can be reduced using artificial aggregates produced from waste powdered materials. This study discussed the production process of alkali-activated artificial coarse aggregates and how their use affects the behavior of concrete. The different concrete mixtures were designed by replacing natural aggregates with artificial ones at different percentages. Various tests were conducted to determine concrete’s fresh, hardened, permeability, and microstructural characteristics. The result showed that concrete incorporated with artificial aggregates can achieve higher workability and lower density than natural aggregate concrete. The mechanical strengths were slightly decreased as the percentage addition of artificial aggregates in a mix increased. However, adding up to 50% showed comparable results to natural aggregate concrete. The water permeability and chloride ion penetration were within the standard limits for all the mixes. The scanning electron micrographs showed a solid and compact ITZ between the phases. XRD pattern revealed that the addition of artificial aggregates had not changed the mineralogical composition of the concrete; the formation of hydrated products helps concrete obtain strength. The study concluded that artificial aggregates could effectively replace natural coarse aggregate in producing structural concrete with many advantages.