Pore Volume Change Research Articles

Experimental Analyses of Pore‐Size Dependent Biomineralization in Porous Media Under Various Flow Rate and Bacterial Density Scenarios

AbstractWe document results of a set of laboratory experiments aimed at exploring impacts of injection rate and bacterial density on biomineralization across water‐saturated porous media. The study relies on a Low‐Field Nuclear Magnetic Resonance technology and the ensuing transverse spin‐spin relaxation time distributions. The latter is documented to provide a robust quantification of temporal histories of pore size distributions during biomineralization. As such, our work explores and quantifies pore‐size dependent biomineralization across the three‐dimensional pore space. The study also provides a quantitative analysis of alterations in porosity and permeability induced by biomineralization, together with a quantification of (time‐averaged) rates of pore volume change. A plugging ratio efficiency index is introduced to quantify the strength of pore‐size‐related biomineralization. Our results reveal that biomineralization induces significant alterations in the pore size distribution within a porous medium, these changes being modulated by bacterial density and injection rate. We find that CaCO3 mainly precipitates in macropores, consistent with the presence of favorable local hydrodynamic conditions and large surface areas therein. Precipitated CaCO3 volume is found to increase with bacterial density. High bacterial densities amplify rate of pore volume change within macropores and adequate plugging ratio of biomineralization and contribute to a significant permeability reduction. Otherwise, a diminished strength of biomineralization in mesopores and micropores is documented for the highest injection rates considered.

Evaluation of volumetric threshold shear strain of gravel-sand mixtures in centrifuge model tests

Evaluation of volumetric threshold shear strain of gravel-sand mixtures in centrifuge model tests

(Invited) open the Gate: Molecular Dynamics Simulation of Adsorption-Induced Phase Transformations of MOF Nanocrystallites

One of the most intriguing features of Metal-organic frameworks (MOFs) is their ability to respond to external stimuli, like the adsorption of guest molecules, with large changes in the accessible pore volume. Theoretical simulations are a key tool to understand such “gate opening” processes on a molecular level. This is typically done within the approximation of periodic boundary conditions (PBC) and using Grand Canonical methods. Such simulations exclude, however, the interface between the MOF and the gas reservoir and ignore any transport effects, which limits them to the thermodynamic equilibrium. Especially for sensing applications, the kinetics of such processes can become important. Recently, our group started to develop and apply methods to simulate MOF nanocrystallites (NCs) beyond PBC, to circumvent such limitations [1,2,3].In the presentation, recent results on the pore opening of DUT-8(Zn) nanocrystallites in carbon dioxide will be shown. Unbiased molecular dynamics simulations reveal a rather fast phase transformation within a few nanoseconds. The first-order phase transition is initiated by a characteristic pore opening at a corner of the crystallite. The anisotropy of the pillared-layer MOF with its channels along the crystallographic c-axis leads to a specific transport pattern for the guest molecules when the pore opening of the MOF proceeds. The simulations allow an unprecedented view of the actual process, including both the mechanics of the phase transformation of the MOF and the diffusive transport of the guest molecules from the reservoir into the MOF.[1] J. Keupp, R. Schmid, Adv. Theory Simul. 2019, 2, 1900117.[2] L. Schaper, J. Keupp, R. Schmid, Front. Chem. 2021, 9, 757680.[3] L. Schaper, R. Schmid, Commun. Chem. 2023, 6, 233.

Initial Desorption Characteristics of Gas in Tectonic Coal Under Vibration and Its Impact on Coal and Gas Outbursts

The rapid desorption of gas in coal is an important cause of gas over-limit and outbursts. In order to explain the causes of coal and gas outbursts induced by vibration, this paper studies the gas desorption experiments of tectonic coal with different particle sizes and different adsorption equilibrium pressures under 0~50 Hz vibration. High-pressure mercury intrusion experiments were used to measure the changes in pore volume and specific surface area of tectonic coal before and after vibration, revealing the control of pore structure changes on the initial desorption capacity of gas. Additionally, from the perspective of energy transformation during coal and gas outbursts, the effect of vibration on the process of coal and gas outbursts in tectonic coal was analyzed. The results showed that tectonic coal has strong initial desorption capacity, desorbing 29.58% to 54.51% of the ultimate desorption volume within 10 min. Vibration with frequencies of 0~50 Hz increased both the gas desorption ratios and desorption volume as the frequency increased. The initial desorption rate also increased with the vibration frequency, and vibration can enhance the initial desorption capacity of tectonic coal and delay the attenuation of desorption rate. Vibration affected the changes in the initial gas desorption rate and desorption rate attenuation coefficient by increasing the pore volume and specific surface area, with the changes in macropores and mesopores primarily affecting the initial desorption rate and 0~10 min desorption ratios, while the changes in micropores and minipores mainly influenced the attenuation rate of the desorption rate. Vibration increased the free gas expansion energy of tectonic coal as the frequency increased. During the incubation and triggering processes of coal and gas outbursts, vibration has been observed to accelerate the fragmentation and destabilisation of the coal body, while simultaneously increasing the gas expansion energy to a point where it reaches the threshold energy necessary for coal transportation, thus inducing and triggering the coal and gas protrusion. The study results elucidate, from an energy perspective, the underlying mechanisms that facilitate the occurrence of coal and gas outbursts, providing theoretical guidance for coal and gas outburst prevention and mine safety production.

Evaluation of Different Fly Ash-Blast Furnace Slag Formulations for Design of Geopolymers in Radioactivity Disposal Applications

Geopolymers in radioactive waste management have in recent times gained dominance in disposal module acceptance. Here is a comparative study on formulations prepared from industrial wastes to be utilized as radionuclide disposal barriers in near surface disposal facilities (NSDFs). Different tools such as isocalorimetry, compressive strength, chemical durability were utilized for screening the formulations. Water leaching of the samples shows that the release of the ions to the leachant is minimal. Durability studies in acids (H2SO4, HCl and HNO3) show that the samples are mostly acid resistant. X-ray tomography suggests low pore volume change over a period of 2 years. The study concludes that the NSDF requirement of low permeability of water and better chemical durability criterion is met by the optimized geopolymerization formulation.

The Early Determination Method of Reservoir Drive of Oil Deposits Based on Jamalbayli Indexes

Summary Historically, the concept of “reservoir drive” aimed to simplify the mathematical modeling in reservoir engineering. Within this framework, the energy of the reservoir, particularly its aquifer, was idealized, leading to classifications such as “partial waterdrive,” “full waterdrive,” “gas cap drive,” and so forth. However, in reality, all existing energy sources interact simultaneously within reservoirs. Accordingly, this study aims to develop a new concept for a more realistic description of reservoir drive mechanisms and evaluation of reservoir energy performance. Numerous computer simulations have revealed a strong correlation between the ratio of relative changes in pore volume to relative changes in reservoir pressure and the reservoir’s energy nature and activity level. Moreover, the noted ratio did not depend on production technology, pressure/volume/temperature properties of hydrocarbon systems, rheological properties of reservoir rocks, or other factors. Based on this correlation, specific parameters termed as Jamalbayli Indexes (JI) have been identified to quantitatively describe reservoir energetic performance. JI consist of two parameters. One of them describes the relative change in pore volume per unit of relative change in reservoir pressure, and the second is the relative change in pore volume per unit of relative change in formation porosity. Here, “relative change” means a change in a parameter relative to its original value. These parameters are dimensionless and can have values around or equal to unity. A new conceptual framework for describing reservoir drive mechanisms based on JI has been formulated. According to this framework, reservoir drive mechanism is determined by comparing the computed JI values with unity rather than relying on subjective assessments of the trend of some functional dependencies. For the first time, it has become possible to express the reservoir drive performance quantitatively and determine the level of energy activity of the reservoirs with the help of JI. Additionally, a technique has been developed to evaluate the numerical values of JI for specific oil (including volatile oil) deposits based on the production data at any stage of production. The proposed methodology was tested using data from the eighth horizon of the Russkiy Khutor field in Russia. The test results not only confirmed the reliability of the obtained model but also demonstrated the adequacy of the proposed concept as a whole. Summarizing the results of other works by the authors, the adequacy of the proposed concept for both oil, gas, and gas condensate deposits has been confirmed. The research findings are expected to contribute to updating the traditional principles used for the mathematical problem statements in fluid flow in porous formations. Additional Key Terms and Phrases Reservoir Drive Mechanism; Early Determination Methods; Reservoir Performance Analysis; Production Data Interpretation; Enhanced Oil Recovery; Reservoir Management; Drive Mechanism Identification; Reservoir Fluid Dynamics; Production Rate Analysis; Reservoir Engineering Techniques; Field Development Planning; Reservoir Simulation; Pressure/Volume/Temperature (PVT) Analysis; Production Monitoring and Evaluation drive mechanisms; production data analysis; volatile oil; Jamalbayli indexes; drive performance indexes

Effect of supercritical carbon dioxide on pore structure and methane adsorption of shale with different particle sizes

Effect of supercritical carbon dioxide on pore structure and methane adsorption of shale with different particle sizes

Microstructure and damage characteristics of cement mortar with different aggregate sizes after cooling based on nuclear magnetic resonance technology

Microstructure and damage characteristics of cement mortar with different aggregate sizes after cooling based on nuclear magnetic resonance technology

The Response Characteristics of Pore Volume and Specific Surface Area of Different Phases of Carbon Dioxide Injection into Anthracite Coal Pores

After the coal sample reacts with CO2, the porosity and pore volume change. Compared with dry raw coal sample, the porosity of coal after CO2 adsorption is increased. With the increase of CO2 injection pressure, the porosity of coal will gradually increase, especially when CO2 enters the supercritical phase. In terms of pore capacity of coal samples, CO2 adsorption time, CO2 adsorption pressure and CO2-H2O treatment do not show obvious regularity in the changes of pore capacity of coal samples, but in general, the increase of CO2 adsorption pressure and CO2-H2O treatment have a positive effect on the increase of pore capacity of coal samples, especially ScCO2-H2O. The mesoporous pore capacity increased by 137.1%. In terms of macro pore volume of coal sample, the change of macro pore volume after CO2 adsorption is more regular. Extending CO2 adsorption time, increasing CO2 adsorption pressure and CO2-H2O treatment all have positive effects on the increase of macro pore volume of coal sample. Under 8MPaScCO2-H2O, macro pore volume reaches a maximum of 0.016462ml/g. The increase also reached 130.4 percent. On the mesoporous specific surface area of coal sample, increasing CO2 adsorption pressure, prolongating CO2 adsorption time and CO2-H2O treatment can increase the mesoporous specific surface area of the sample. The mesoporous specific surface area of the sample at 8 MPa ScCO2-H2O is 0.631 m2/g, which reaches the maximum in this experiment, with an increase of 334.27%.

Effect of corrosion pit distribution of rebar on pore, and crack characteristics in concrete

Effect of corrosion pit distribution of rebar on pore, and crack characteristics in concrete

On the effect of thermal activation on the surface chemistry of natural mineral sorbents

The article discusses adsorbents, their characteristic features, structural sizes, geometric forms, porosity, the concept of porosity and the influence of their thermal activation on the structure and sorption parameters of natural mineral sorbents - Angren kaolin and Azkamar bentonite. Here is given the chemical composition of kaolin and bentonite clay samples before and after thermal activation. Thermal activation of kaolin clay at 1023K is shown, which has almost no effect on the content of basic oxides in the clay mineral. It leads to the removal of adsorbed moisture and partially constitutional water, as a result of which the mass loss on ignition (WLP) of a thermally activated kaolin clay sample is reduced. The adsorption isotherms of water vapor on thermally activated samples of kaolin and bentonite have an S-shape according to the BET classification, which is due to capillary condensation in the P/P-1.0 region. All isotherms are characterized by the presence of a hysteresis loop over the entire range of relative pressures. The reason for the appearance of a hysteresis loop in the case of sorption of water vapor is associated with the swelling of clays in the vapor phase. The change in the chemical composition of the initial and clays activated at 1023K is shown in the form of a table. Based on the research, it was concluded that during thermal activation of PMS, processes associated with dehydration and dehydroxylation occur, which leads to changes in porosity, specific gravity, and total pore volume.

EXPLORATION OF GEOPOLYMER BINDERS UTILIZING FLY ASH AND SEWAGE SLUDGE ACTIVATION: IMPACTS ON FRESH PROPERTIES, STRENGTH, DURABILITY, MICROSTRUCTURE AND THERMAL CONDUCTIVITY

This research aims to investigate the effect of the incorporation of sewage sludge as an activator in the formation of fly ash-based geopolymers. The geopolymer paste is made up of 15% sewage sludge by weight, with the remainder consisting of fly ash. The blended mix is activated using a hydroxide solution containing 10% Na2O relative to the total base material. To assess the mechanical and microstructural characteristics of the resulting geopolymer paste, it is necessary to conduct compressive strength tests as well as FESEM, SEM, XRD, and TG/DTA analyses. To evaluate the workability of the designed geopolymer paste, an area factor test can be used here. GPP4, using sodium silicate, achieved the highest 3-day compressive strength (38.0 MPa) with a dense, amorphous structure and minimal mass loss. In contrast, GPP3 with sludge showed a porous texture and moderate strength. TGA supports the observation of GPP4's amorphous nature, aligning with the findings from XRD and FESEM analyses. Further, sorptivity tests revealed changes in pore size and volume based on the activator and fly ash type. GPP4 also exhibited a thermal conductivity of 2.44×10⁻⁴ cal/cm/°C/s, demonstrating sludge's potential as an economical alternative for geopolymer binders.

Sol-gel synthesis of zirconia-based nanoparticles from the side product of tin mining

Indonesia has been one of the world’s primary source of tin since the early of 19th century. Bangka island has the largest tin abundant with a side product is zircon sand (ZrSiO4). The existence of zircon (ZrSiO4) is mostly associated with some of the valuable oxide compounds (VOC) and rare earth oxides (REO). The zirconia powders were synthesized from the zircon sand of PT. Timah Tbk by caustic fusion method followed by sol-gel method. The raw material zircon sand and as-synthesized zirconia were characterized through x-ray fluorescence (XRF), x-ray diffraction (XRD), surface area analysis and porositymeter, thermogravimetric and differential scanning calorimetry analysis (TG-DSC), fourier transform infra-red (FTIR) and scanning electron microscopy (SEM) techniques. The results show that zircon sand from PT Timah Tbk contains some of VOCs, such as ZrSiO4, ZrO2, HfO2, SiO2, Al2O3, TiO2, Fe2O3 and some REOs, such as La2O3, Y2O3, Nb2O5. The fusion temperatures varied from 600 to 800 °C which resulted in an increase of the purity of ZrO2 to 76% based on the XRF analysis. The surface area analysis and porositymeter results showed the significant change in specific surface area, pore size and pore volume of as-synthesized zirconia. The specific surface area increased dramatically from 0.28 m2/g to 173.97, 125.18, and 102.14 m2/g, at fusion temperatures of 600, 700, and 800 °C, respectively. The average particle size of as-synthesized zirconia showed the significant change from 21.31μm to 34.48 nm. The results of this work open new opportunities for the development of zirconia-based nanoparticles from the side product of tin mining.

Damage characteristics of pore and fracture structures of coal with liquid nitrogen freeze thaw

Liquid nitrogen (LN2) fracturing technology is a novel waterless fracturing technology that has significant potential for application in the development of coalbed methane. However, the changes in the microstructure after coal samples are treated with LN2 freeze thaw are poorly understood. Therefore, a combination of mercury intrusion porosimetry and micro-computed tomography (micro CT) was employed to investigate the evolution of pore and fracture structure of coal samples treated with LN2. The experimental results showed that the pore volume and average pore size of coal samples increase after LN2 freeze thaw. After 12 freeze thaw cycles, the change in pore volume of micropores and minipores of coal samples was not significant, while the pore volume of mesopores and macropores increased significantly before LN2 freeze thaw. The specific surface area of the pores in different size ranges of coal samples increases with the increase in the number of LN2 freeze thaw cycles; the structure of micropores and miniopores were damaged by thermal stress and frost heave force during LN2 freeze thaw; and the pore size gradually increases to form mesopores and macropores. Micro-CT images of coal samples after LN2 freeze thaw indicated the primary fractures of coal sample expanded and generated a large number of secondary fractures. The primary and secondary fractures are interconnected and ultimately form penetrated fracture enhancing the connectivity of fractures, enhancing the connectivity of the fracture structure. The key finding study is expected to provide a theoretical basis for LN2 fracturing.

The chemical damage of sandstone after sulfuric acid-rock reactions with different duration times and its influence on the impact mechanical behaviour

The low-permeability characteristic of sandstone-type uranium deposits has become the key geological bottleneck during the in-situ leaching mining, seriously restricting the development and utilization of uranium resources in China. At present, the blasting-enhanced permeability (BEP) and acidizing-enhanced permeability (AEP) are confirmed to be mainstream approaches to enhance the reservoir permeability of low-permeability sandstone-type uranium deposit (LPSUD). To clarify the synergistic effect of BEP and AEP, the acid-rock reaction and dynamic impact experiments were conducted, aiming to study the effect of chemical reactions on pore structure, dynamic mechanical properties and failure pattern of sandstone. Results show that with the increasing acid-rock reaction time, the total pore volume of samples is promoted largely and exhibits obvious chemical damage. The change of pore volume depends on the pore size, the 100-1000nm and 1000-10000nm pores are more susceptible to acid-rock reactions. The dynamic peak strength and the dynamic elastic modulus are decreased and the dynamic peak strain and strain rate are increased when lengthening the acid-rock reaction time, whose evolution laws can be fitted by the logistic expression, the linear expression and the exponential expression, respectively. The acid-rock reactions also have an influence on the fracture development of samples after the dynamic impact. The damaged fractures on the end faces of samples grow from the isolated short fracture, the isolated long fracture to the fracture network, and the damaged fractures on the sides of samples develop from the non-penetration fractures, penetration fractures to the multi-branch fractures. This study clarifies the physical and chemical combined damage mechanism, demonstrates the potential of reservoir stimulation by uniting the BEP and the AEP, and provides a theoretical reference for the reservoir stimulation of LPSUD.

Simulating the structural phase transitions of metal-organic frameworks with control over the volume of nanocrystallites

Flexible metal-organic frameworks (MOFs) can undergo structural transitions with significant pore volume changes upon guest adsorption or other external triggers while maintaining their porosity. In computational studies of this breathing behavior, molecular dynamics (MD) simulations within periodic boundary conditions (PBCs) are commonly performed. However, to account for the finite size and surface effects affecting the phase transition mechanism, the simulation of non-periodic nanocrystallite (NC) models without the constraint of PBCs is an important alternative. In this study, we present an approach allowing the analysis and control of the volume of finite-size structures during MD simulations by a tetrahedral tessellation of the (deformed) NC’s volume. The method allows for defining the current NC’s volume during the simulation and manipulating it regarding a particular reference volume to compute free energies for the phase transformation via umbrella sampling. The application on differently sized DMOF-1 and DUT-128 NCs reveals flexible pore closing mechanisms without significant biasing of the transition pathway. The concept provides the theoretical foundation for further research on flexible materials regarding targeted initialization of the structural phase behavior to elucidate the underlying mechanism, which can be used to improve the applications of flexible materials by targeted controlling of the phase transition.

Frictional and poromechanical properties of the Delaware Mountain Group: Insights into induced seismicity in the Delaware Basin

Frictional and poromechanical properties of the Delaware Mountain Group: Insights into induced seismicity in the Delaware Basin

Pengaruh Kadar Air Terhadap Pengembangan Tanah Ekspansif

Expansive soil is one type of problematic soil, very sensitive to changes in moisture content. This soil has the characteristics of large shrinkage expansion due to changes in pore volume which can cause lifting forces on existing construction can cause damage to the construction. This research aims to determine the effect of water content on expansive soil in increasing the percentage of swelling soil. The research was conducted experimentally with materials used in this test is expansive soil taken from Sambungmacan, Sragen, Central Java. The main test equipment used in this test is a steel cylindrical mould. Cylindrical mould is filled with expansive soil then compacted a depth of 12 cm. Then the expansive soil is gradually moistened with water until it reaches maximum moisture content to determine its effect on the swelling value. The results of this study show that the increasing water content, then swellin percentage increases in expansive soils until the soil no longer expands at a certain water content.

Analysis of the bond behavior of a GFRP rebar in concrete by in-situ 3D imaging test

Computed tomography combined with mechanical tests offers completely new insight into the behavior of concrete samples under stress. Particularly the development of new fiber reinforcement materials for concrete elements requires appropriate material models and thus for investigating the interior of the concrete structure. In 3D image data obtained by computed tomography, local structural changes within the sample due to mechanical loading can be observed without further altering the sample. We applied this state-of-the-art approach to a concrete core with an embedded glass fiber reinforced polymer rebar under increasing forces applied to pull out the rebar. In this paper, authors describe a novel in-situ setup for non-destructively 3D imaging during the pull-out test. Conducting the pull-out test leads to the formation of local pore volume changes along the rebar. These pore volume changes are not only visualized but quantified analytically based on the images. Interpreting these volume changes, we derive a novel method for calculating strain and normal stresses in the rebar. Our new method captures the detailed distribution of the bond stresses between rebar and concrete and consequently describes the bond behavior more accurate. It turns out that the observed bond behavior cannot be explained completely by commonly assumed material laws. This emphasizes the need for further, more extensive research combining 3D imaging, mechanical testing, and quantitative image analysis.

A Temperature-Controlled Apparatus for Gas Permeability under Low Gas Pressure

The measurement of soil gas permeability is influenced by the temperature and pressure fluctuation in the low gas pressure region. In order to investigate these influences, a soil temperature-controlled apparatus connected to a low-gas-pressure supply equipment is proposed in this study. The low constant gas pressure is supplied by two Mariotte bottles, by which the airflow rate is measured. Meanwhile, the soil specimen is controlled by a temperature-controlled apparatus. During the test, the negative pore water pressure and volume change of the soil specimen are measured. Through the temperature-controlled apparatus, it is observed that as the temperature increases from 25 °C to 60 °C, there is a corresponding increase in soil sample porosity by 5.4%, while the negative pressure of pore water decreases by 11.1%. This can be attributed to the reduction in the surface tension of contractile skin caused by elevated temperatures. Furthermore, due to variations in gas viscosity with temperature, there was a significant decrease in the gas flow rate by 50.5%. And, the relationship between permeability and volumetric gas content at different temperatures in low-pressure regions well confirms the existing power-law model. In addition, the existence of a temperature-independent critical negative pore water pressure is observed, beyond which the intrinsic permeability remains constant. At 36 kPa of negative pore water pressure, the intrinsic permeability at 60 °C exhibits an 81.8% reduction compared to that at 25 °C. This decline in intrinsic permeability can be attributed to a diminished pore connectivity, resulting from elevated temperatures.