Transverse Relaxation Time Distribution Research Articles

Real-time detection of cerebral edema in mice based on low-field nuclear magnetic resonance

Real-time detection of cerebral edema in mice based on low-field nuclear magnetic resonance

Pore structure characterization and reservoir quality prediction in deep and ultra-deep tight sandstones by integrating image and NMR logs

Pore structure characterization and reservoir quality prediction in deep and ultra-deep tight sandstones by integrating image and NMR logs

Investigation on Mechanical Parameters and Microstructure of Soil-Based Controlled Low-Strength Materials with Polycarboxylate Superplasticizer

This study aims to optimize the sustainable utilization of excavated soil by incorporating it exclusively as a fine aggregate and cement in the formulation of soil-based controlled low-strength materials. The polycarboxylate superplasticizer was introduced to enhance flowability. Various factors, including the cement contents, initial water contents, and curing time, were systematically analyzed for their effects on the fresh properties, mechanical parameters, transverse relaxation time distribution, pore size distribution, porosity, and corrosivity of soil-based controlled low-strength materials. The results indicate that polycarboxylate superplasticizer effectively dispersed clay minerals and cement particles, enhancing the flowability. The unconfined compressive strength increased with the rising cement content and decreased with the increasing initial water content. Additionally, the transverse relaxation time distribution curves of the soil-based controlled low-strength materials exhibited two peaks. These curves shifted to smaller transverse relaxation time values with the increasing cement content, while gradually shifting to larger transverse relaxation time values with the increasing initial water content. An increase in the cement content resulted in higher volume percentages of small and mesopores, while extra-large pores and macropores decreased. The addition of the polycarboxylate superplasticizer had minimal impact on the pore volume percentage distribution. Furthermore, porosity experienced a decline with the rise in the cement content and curing time, in contrast to a notable increase with a higher initial water content. This investigation provides valuable insights into the engineering properties and microstructural characteristics of soil-based controlled low-strength materials, offering a foundation for sustainable waste management practices in geotechnical applications.

Permeability evaluation based on Nuclear Magnetic Resonance analysis for gas hydrate reservoir

Permeability (or hydraulic conductivity) is one of the most important parameters for analyzing hydraulic behavior of underground. For example, in the geotechnical engineering, permeability is necessary to calculate water inflow and draw down of water level during excavation, to predict the deformation time due to the consolidation, and to evaluate the barrier of the ground for radioactive waste disposal. In the petroleum industry, permeability is considered an essential parameter which is directly linked to the productivity of oil and natural gas. Therefore, predicting permeability using wireline logging or logging while drilling (LWD) is required during the assessment of the reservoir. Nuclear Magnetic Resonance (NMR) logging is performed at this point. Low-field NMR measurements are sensitive to the hydrogen proton, 1H, in liquid water but not to the 1 H bond in solid form, making it possible to obtain the bulk water volume. In addition, the hydrogen proton NMR- T2 (transverse or spin-spin) relaxation time distribution is used to infer pore-size information and to estimate permeability [1, 2]. The major methods used for estimating permeability, k, are the Schlumberger Doll Research (SDR) model and Timur-Coates (TC) model [3, 4]:
 Where fNMR is the NMR-estimated (effective) porosity. SDR model uses the averaged value of the T2 distribution plotted on log-scale of time and matches it to the experimental reference permeability with the fitting parameter a [mD/(ms)2]. The TC model seeks to differentiate between the fraction of free (mobile) fluid volume (FFV) and bound fluid volume (BFV) and estimates permeability with FFV/BFV ratio and the material constant c [m2/s2]. The permeability in the research and development of methane hydrate, which is expected to be a next-generation resource, has been estimated using above methods. Methane hydrate is an ice-like solid crystalline structure of water and methane molecules. Because hydrate is solid, NMR is not sensitive, the initial (effective) permeability can be estimated by NMR analyzer. On the other hand, A strong disconnect (up to 2 orders of magnitude) between NMR-based estimates of permeability with those determined from a laboratory study of pressure cores from the same reservoir has further cast uncertainty in the application of borehole NMR data in hydrate evaluation [5, 6]. Recently, authors provided comparisons between NMR-derived values and direct fluid flow estimates of permeability in naturally occurring hydrate-bearing sediment [7, 8]. On the basis of the NMR measurement for hydrate-bearing pressure core sediments, which were recovered from the Gulf of Mexico and Alaska North Slope, the following new hydraulic radius model was proposed [7].
 This equation estimates the specific surface based on the NMR signal and has been shown to successfully estimate the initial permeability of a hydrate reservoir by expressing a hydraulic radius model based on Kozeny's equation [9]. However, the proposed equation is not universal and has been found to overestimate for clayey and silty hydrate free sediment. This study summarizes the methods and parameters used to estimate permeability using NMR signals from hydrate-bearing sediment obtained from logging and laboratory tests for the Gulf of Mexico and Alaska North Slope. In addition, we reports parameters for predicting model for muddy sediments which was recovered from overburden of hydrate-reservoir in the Hyuganada sea in 2022 Japan [10, 11]. When using the hydraulic radius model to predict permeability of hydrate-bearing sediment, reasonable estimates can be obtained by setting the shape factor for grains Cs = 1/2 (for a circular grain) and the shape factor for the flow path cn = 4 (for the cylinder network), respectively. Although, for hydrate free muddy sediment, Cs = 1/3 for parallel plate grain shape and cn = 2 for the fracture network model matched its permeability. Furthermore, the conversion parameter from T2 relaxation time to the pore size for hydrate free muddy sediments r2 = 0.009 (mm/s) was confirmed based on the result of mercury injection capillary pressure analysis, which is lower than r2 = 0.0325 (mm/s) of hydrate-bearing sediments.

Development of a Single-Sided Magnetic Resonance Surface Scanner: Towards Non-Destructive Quantification of Moisture in Slaked Lime Plaster for Maintenance and Remediation of Heritage Architecture

Single-sided time-domain proton magnetic resonance (MR) surface scanners are useful for non-destructive measurements of moisture. A mobile single-sided MR sensor unit employing two concentric ring magnets was constructed for the in situ quantification of moisture in slaked lime plaster used in the outer walls and roofs of heritage architecture. This sensor unit allows for non-destructive measurements of water proton relaxation 1.5 to 13.5 mm beneath the surfaces of walls and roofs. The following laboratory experiments on water-saturated porous slaked lime plaster samples were performed. (i) The porosity (water volume fraction) was measured in approximately eight minutes with a root mean square error of 1.9 vol%. (ii) The fundamental MR-related property (i.e. proton surface relaxivity) needed for the estimation of the pore size distribution was also measured successfully. (iii) The pore volume expansion due to frost damage was successfully detected as a significant change in the transverse relaxation time distribution. These results demonstrate that the portable MR surface scanner is a promising non-destructive testing tool for the maintenance and remediation of heritage architecture made of plaster.

Evidence of hydrothermal fluid migration pathways in pores and microfractures based on nuclear magnetic resonance and electron microscopic analyses from the Southwest Indian Ridge

Evidence of hydrothermal fluid migration pathways in pores and microfractures based on nuclear magnetic resonance and electron microscopic analyses from the Southwest Indian Ridge

Amphoteric retarder for long-standing cementing: Preparation, properties and working mechanism

Amphoteric retarder for long-standing cementing: Preparation, properties and working mechanism

Rapid and Simultaneous Measurement of Fat and Moisture Contents in Pork by Low-Field Nuclear Magnetic Resonance.

In order to improve the efficiency of Soxhlet extraction and oven drying, low-field nuclear magnetic resonance (LF-NMR) technology was used to detect fat and moisture contents in pork. The transverse relaxation time (T2) distribution curves were constructed by Carr−Purcell−Meiboom−Gill (CPMG) experiments. In addition, the optimal conditions of adding MnCl2 aqueous solution was explored to separate water and fat signal peaks. Finally, the reliability of this method for the determination of fat and moisture contents in pork was verified. The present study showed that adding 1.5 mL of 20% MnCl2 aqueous solution solution at 50 °C can isolate and obtain a stable peak of fat. The lard and 0.85% MnCl2 aqueous solution were used as the standards for fat and moisture measurements, respectively, and calibration curves with R2 = 0.9999 were obtained. In addition, the repeatability and reproducibility of this method were 1.71~3.10%. There was a significant correlation (p < 0.05) between the LF-NMR method and the conventional methods (Soxhlet extraction and oven drying), and the R2 was 0.9987 and 0.9207 for fat and moisture, respectively. All the results proved that LF-NMR could determine fat and moisture contents in pork rapidly and simultaneously.

Characterization of mechanical properties and microstructure of silica mortar and coral mortar based on nuclear magnetic resonance technology

It is crucial to use coral sand to replace traditional sand and gravel aggregates to produce coral aggregate concrete for island development and construction to minimize environmental damage to offshore islands and reefs. Coral sand particles are irregular in shape, porous, and break easily, resulting in substantial differences in engineering mechanical properties and the microstructure compared to land-based sand. Uniaxial compressive strength tests were carried out on coral mortar and silica mortar to determine the influence of the sand-cement ratio on the mortars’ compressive strength. Low-field nuclear magnetic resonance (NMR) technology was used to analyze the compressive strength of the two mortars at the microscopic scale. The optimum sand-cement ratio of coral mortar was determined. At the same mixture ratio, the compressive strength of coral mortar was lower than that of silica mortar. In the early hydration reaction, only one main peak occurred in the transverse relaxation time distribution of the silica mortar, but a secondary peak was observed in the coral mortar, and a transition peak appeared 84 hours later. The pore size range of the internal pores of the coral mortar was large, and the interval was continuous. The significantly higher proportion of harmful pores and very harmful pores resulted in the lower strength of the coral mortar than the silica mortar. The research results can provide a reference for using NMR to evaluate coral mortar.

Quantitative characterization of methane adsorption in shale using low-field NMR

Quantitative characterization of methane adsorption in shale using low-field NMR

Characterization of unfrozen water in highly organic turfy soil during freeze–thaw by nuclear magnetic resonance

The unfrozen water content (ωu) is an important parameter affecting the hydrothermal-mechanical characteristics of soil and is of important significance with regard to engineering construction and environmental effects in cold regions. In this study, a widely-distributed special humus soil called turfy soil, with poor engineering geological properties, from seasonally frozen regions of northeastern China was investigated. Soil fundamental properties were determined, and ωu under various temperatures during a freeze–thaw process was measured by the nuclear magnetic resonance (NMR) method. Based on NMR theory and transverse relaxation time (T2) distribution curves, two thresholds were determined to divide the types of pore water in soil. Soil freezing characteristic curves (SFCC) of the total and pore water were drawn, and changes in the internal microstructure and pore characteristics of the soil during the freeze–thaw process were analyzed. The results showed that a drastic phase change within the soil occurs during −2 °C to −4 °C, and the freezing process can be divided into three stages. The formation of small pores and the connection of large pores make the soil looser after freeze–thaw. The division of pore water and variation in ωu show that freezing starts from large pores, while thawing starts from small pores. The capillary water content significantly decreases after freeze–thaw, and the bulk water content tends to increase. At freezing Stage I, ωu is closely related to the initial properties of the soil, whereas ωu at −3 °C almost determines the value of ωu during subsequent freeze–thaw. Finally, a ωu-power function for turfy soil was proposed, and good fitting results were obtained for both freezing and thawing soil. This work can serve as the basis of studies on soil with high organic matter content as well as soil unfrozen water content during freeze–thaw cycles in cold regions.

Fractal analysis on CO2 hydrate-bearing sands during formation and dissociation processes with NMR

Injecting CO2 into submarine sediments to form hydrates is one of the potential methods of CO2 sequestration. The transition behavior of CO2 hydrates in porous media is of great practical significance. In this work, CO2 hydrate formation/dissociation in porous media was monitored in real time by a low-field magnetic resonance (MR) system, and a series of dynamic fractal dimensions of the pore space occupied by converted water during the hydrate formation/dissociation process were obtained based on the transverse relaxation time (T2) distributions. In general, the dimension of the converted water space increases with hydrate formation and decreases with the hydrate dissociation progress. A smaller particle size of porous media and a lower initial water saturation can promote hydrate formation, and the corresponding fractal dimension is higher during the hydrate formation process. There is a special status of the fractal period observed during the hydrate formation/dissociation process, and it is considered the temporally and spatially uniform distribution of hydrate crystal formation/dissociation inside the porous media. These results also indicate the relationships between the hydrate transition progress and the dynamic fractal dimension, which are useful for future works on pore-scale hydrate-bearing transitions during hydrate-based CO2 sequestration.

Emergence of non-aqueous phase liquids redistribution driven by freeze-thaw cycles in porous media based on low-field NMR

• Redistribution of NAPLs driven by freeze–thaw (FT) cycles was confirmed in a wide saturation range (14.34% to 72.05%). • Substantial remobilization of NAPLs occurred between macropores and mesopores during FT cycles. • Distribution of NAPLs in micropores remained almost unchanged during FT cycles. • Contribution of micropores to NAPLs redistribution was much smaller than that of mesopores and macropores. • A model related to freezing-induced pressure was proposed to explain the change in the redistribution rate of NAPLs. Increasing human activities in cold regions have led to serious environmental problems due to non-aqueous phase liquids (NAPLs) contamination. However, the NAPLs redistribution driven by freeze–thaw (FT) cycles is not well understood. In this study, the redistribution of NAPLs in porous media subjected to FT cycles in a temperature range from 20 °C to −15 °C was investigated using the low-field Nuclear Magnetic Resonance (NMR) technique. The redistribution of NAPLs in the prepared samples with NAPLs saturation ranging from 13.56% to 72.05% was confirmed using the transverse spin-spin relaxation time ( T 2 ) distribution and the magnetic resonance imaging (MRI). Experimental results revealed that substantial remobilization and distribution of NAPLs occurred between the macropores ( T 2 greater than 300 ms) and the mesopores (60 ms < T 2 < 300 ms) while the NAPLs in the micropores ( T 2 < 60 ms) remained almost unchanged during 30 FT cycles. The main reason is attributed to the fact that the redistribution rate in micropores is much lower than in macropores and mesopores. Furthermore, the NAPLs content and the number of FT cycles were positively correlated for macropores while negatively correlated for mesopores. For the samples with low NAPLs saturation (e.g., S N =13.56% and 13.56%), the redistribution rate of NAPLs versus FT cycles exhibited an overall linear relationship for macropores and mesopores while a non-liner relationship for micropores. For all pore categories, the increment in S N can cause a remarkable deviation extent. The balance between capillary pressure and freezing-induced pressure was evaluated by the newly introduced dimensionless pressure ratio Δ P , which could help determine the ultimate mobilization and redistribution of NAPLs during FT cycles. Experimental tests suggested that the Δ P was much larger in macropores than in mesopores and micropores. This can explain the dramatic difference in the redistribution rate among different pore categories. This fundamental study is helpful in understanding the mobilization and redistribution mechanisms of NAPLs in cold regions.

Chitosan Effect on Hardening Dynamics of Calcium Phosphate Cement: Low-Field NMR Relaxometry Investigations.

Calcium phosphate cements are used in dentistry and orthopedics to repair and reconstruct bone defects. The properties of these bone cements can be improved by introducing additives into their composition. One favorable additive is chitosan, which can be beneficial but can also cause considerable damage if it has a high load, thus, limiting its clinical applicability and performance. That is why understanding chitosan’s role in cement composition is an important issue when developing new materials. The present work uses low-field nuclear magnetic resonance (NMR) relaxometry to investigate the effect introduced by the addition of chitosan on the hardening process of calcium phosphate cement. Two samples, prepared with and without chitosan, were comparatively investigated during the first six minutes of hardening. The liquid evolution inside these samples was monitored using transverse relaxation time distributions. It demonstrated an acceleration effect on the hardening dynamics introduced by the presence of chitosan. Furthermore, it was shown that even after one hour of hardening, there were still unreacted monomers inside the bone cement and their amount was reduced in the presence of chitosan.

A new method for capillary pressure curve prediction based on NMR echo data using integral transform, the quantum genetic algorithm, and the artificial neural network in tight sandstone

The capillary pressure curve (CPC) is an important tool with which to investigate the petrophysical properties and pore structure of oil and gas reservoir rocks. However, the method of obtaining the CPC directly via laboratory measurements is usually time-consuming and costly, prone to the contamination or destruction of core samples, and can only be applied to limited cores. A new method adopting integral transform, the quantum genetic algorithm, and the artificial neural network (IT-QGA-ANN) based on nuclear magnetic resonance (NMR) echo data is proposed to improve CPC prediction accuracy in tight sandstone. First, 7 parameters that characterize rock properties are directly extracted from echo data using integral transform. This process does not require to obtain the transverse relaxation time (T2) distribution by inversion of echo data, thereby avoiding the influence of inversion uncertainty. These characteristic parameters are then used as the input of the ANN, and the QGA method is utilized to optimize the weights and thresholds of ANN. Numerical simulation results prove the validity of integral transform to extract characteristic parameters. A total of 18 tight sandstones are used for mercury injection and NMR tests. The results indicate that, compared with the traditional nonlinear regression and ANN methods, the proposed IT-QGA-ANN method can more accurately predict the CPC. The proposed method achieves the direct and accurate transformation from echo data to the CPC, and provides important guidance for solving complex nonlinear problems in oil and gas reservoir evaluation based on NMR.

NMR Relaxometry Studies on the Drying Kinetics of Cellulose Nanofibers

Nanocellulose is an emerging biopolymer with increasing interest from a variety of engineering fields. Given the complex textural properties and structural changes induced by drying, understanding the dehydration dynamics of nanocellulose is highly important. However, common bulk characterization techniques cannot be performed in real working conditions and usually require aggressive sample preparation. As an alternative, time-domain nuclear magnetic resonance (TD-NMR) can be applied with minimum interference. Here, well-established drying kinetic models and TD-NMR relaxometry were used to monitor water evaporation in a cellulose nanofiber slurry. The applied equations reasonably predicted the moisture contents from gravimetry but provided no information about the fluid/solid distribution during the drying event. As a complement, relaxometry results indicated the presence of water in different confinement environments based on obtained transverse relaxation time distributions. Free (bulk) water was observed during the initial 24 h of drying, and intrapore water presented a bimodal fashion with similar temporal trends but different rates. Lastly, the drying kinetic models were applied to the ratio of areas obtained from T2 curves with a notable fit. The results discussed here support the use of relaxometry experiments as a viable method for drying kinetic studies with potential expansion to a myriad of wetted systems.

Fractal Dimension Calculation Method from NMR Measurement and Its Application

Abstract The pore structure of organic shale with nano-scale pores is important for reservoir evaluation. Fractals shows the self-similarity of shale rocks and can reflect the pore structure. The fractal dimension of organic shale from nuclear magnetic resonance (NMR) measurement was studied and some equations were directly derived based on NMR transverse relaxation time (T2) distribution. In a case study, the fractal dimensions were calculated by the proposed method and numerical simulation, and the formation cementation index in Archie equation for saturation evaluation was calculated from the fractal dimension of NMR logging. The comparison of calculated water saturation and the core experiment result prove that the proposed method is more effective than the previous Archie’s equation with default cement index.

The in-situ NMR evidence of gas hydrate forming in micro-pores in the Shenhu area, South China Sea

Nuclear magnetic resonance (NMR) measurement could provide information during the formation and dissociation of gas hydrate on the pore structure properties which are of great important to understand the gas production behavior. In this study, the in–situ NMR and other well logging data achieved during the natural gas hydrate drilling program were used to study the pore size and hydrate formation properties in the Shenhu area, South China Sea by comparing transverse magnetic relaxation time (T2) distributions between the gas hydrate zone and the upper water–saturated zone whose properties represent the virgin status. Compared with those of the upper water–saturated layer, increasing resistivity, higher–than–baseline shear modulus, less–than–density–porosity NMR porosity, shortening T2 peak time, reducing amplitude and covered area of T2 distributions and decreasing water–filling pore size denote the association of hydrate. Based on eight bin porosities distribution derived from user-defined time intervals of the T2 distribution for researching the hydrate formation characteristic in different pore size, macro–pores (T2 ≥ 10 ms, r c ≥ 0.9 μ m), meso–pores (3 ms ≤ T2 < 10 ms, 0.27 μ m ≤ r c < 0 . 9 μ m) and micro–pores (T2 < 3 ms, r c < 0.27 μ m) were divided. It was found that the meso–pores are the dominant pore size in the Shenhu area, but hydrate form more easily in the macro–pores. Just as the previous experience, gas hydrate forms primarily in macro–pores and meso–pores resulting in an increase of micro–pores. In addition, another mode was achieved that gas hydrate forms in the three types of pore spaces leading to a decrease of micro–pores. Both forming modes can develop reservoirs with high hydrate saturation that can exceed 30%.

Hydrothermal solidification of alkali-activated clay-slaked lime mixtures

Waste clay was converted into non-sintered building materials by hydrothermal solidification technology to improve resource utilization. The effects of curing time, curing temperature, initial dry density and alkaline environment on the strength development of the hydrothermally solidified clay-slaked lime mixtures were evaluated by compressive strength tests, and the microstructural evolution and solidification mechanism were analyzed by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM) and low-field nuclear magnetic resonance (NMR). The generated calcium silicate hydrate (C-S-H), katoite, and Al-substituted tobermorite filling pores and cementing mineral particles were the main factors responsible for the improved strength and compactness of the material. The C-S-H gel was transformed into Al-substituted tobermorite crystals in the presence of 4 mol/L NaOH solution, which greatly increased the compressive strength to 45.3 MPa. The transverse relaxation time (T2) distribution was transformed into a pore size distribution curve by combined mercury injection porosimetry (MIP) and NMR, which can effectively characterize the evolution of the pore structure. The synthesis conditions determined the type and quantity of hydrothermal products that affect the pore size distribution and microstructure, thereby exhibiting changes in structural and mechanical properties on the macroscale.

Composition Profiling and Authenticity Assessment of Camellia Oil Using High Field and Low Field 1H NMR.

Camellia oil (CA), mainly produced in southern China, has always been called Oriental olive oil (OL) due to its similar physicochemical properties to OL. The high nutritional value and high selling price of CA make mixing it with other low-quality oils prevalent, in order to make huge profits. In this paper, the transverse relaxation time (T2) distribution of different brands of CA and OL, and the variation in transverse relaxation parameters when adulterated with corn oil (CO), were assessed via low field nuclear magnetic resonance (LF-NMR) imagery. The nutritional compositions of CA and OL and their quality indices were obtained via high field NMR (HF-NMR) spectroscopy. The results show that the fatty acid evaluation indices values, including for squalene, oleic acid, linolenic acid and iodine, were higher in CA than in OL, indicating the nutritional value of CA. The adulterated CA with a content of CO more than 20% can be correctly identified by principal component analysis or partial least squares discriminant analysis, and the blended oils could be successfully classified by orthogonal partial least squares discriminant analysis, with an accuracy of 100% when the adulteration ratio was above 30%. These results indicate the practicability of LF-NMR in the rapid screening of food authenticity.