Low-field Nuclear Magnetic Resonance Measurements Research Articles

Evaluation of pore characteristics evolution and damage mechanism of granite under thermal-cooling cycle based on nuclear magnetic resonance technology

During the development process of deep geothermal energy (Hot dry rock, HDR), the high-temperature granite matrix in the wellbore needs to withstand thermal-cooling cycles, easily leading to wellbore instability and collapse. Considering the actual drilling engineering using different types of drilling fluid, thermal-cooling cycle experiments (cycles of 1, 2, 4, 8, 12 times) of granite were conducted using natural, water, and liquid nitrogen (LN2) cooling methods. Based on the low-field nuclear magnetic resonance measurement, the development and evolution of pore size, quantity, and distribution under different cooling ways and thermal cycles were studied, and the changes in rock mechanical parameters under different cooling methods and thermal cycling conditions were quantified. Then, the rock damage coefficients based on the variation patterns of different types of pores were calculated, and a quantitative relationship was established among T2 spectrum, pore, and mechanical damage. Finally, the proton weighting method was used to analyze the changes in the internal bearing area of rocks, revealing the deterioration mechanism of rock mechanical properties under different cooling ways and thermal cycling conditions. The results showed that the porosity increased with thermal cycles during the thermal-cooling cycle treatment, and the growth rate was first fast and then slow. Under the same number of thermal cycles, the groundwater cooling porosity was the highest, followed by LN2 and natural cooling. The relationship between T2 spectral area and rock damage was established on this basis, and the rock damage value increased with thermal cycles in an exponential function, and the proportion of large pores significantly affected the pore damage. A relationship (positively proportional linear) between pore damage and the mechanical degradation coefficient of high-temperature cooling cycle granite and a method for predicting rock degradation through pore damage were established, the deterioration mechanism of rock mechanical properties under thermal cycle treatment was revealed.

Research Note: Relationships between texture and water property measurements in raw intact broiler breast fillets with the wooden breast condition

Relationships between texture measurements and meat water properties were investigated in raw intact broiler breast fillets with the wooden breast (WB) condition. Texture measurements included subjective WB scores and blunt Meullenet-Owens Razor Shear (BMORS). Water properties were determined with low-field nuclear magnetic resonance (LF-NMR). Spearman correlation was used to estimate relationships between WB scores and water properties, while Pearson correlation was used for relationships between BMORS force and water properties. LF-NMR measurements exhibited 3 water components: protein-associated or hydration water T2b, intra-myofibrillar water or immobilized water T21, and extra-myofibrillar water or free water T22 in chicken breast meat. Significant and strong Spearman correlations were found between the WB scores and T21 time constant, the abundance (normalized areas) of T22, and the proportion of T21 and T22 (rs > 0.60, P < 0.001). Strong Pearson correlations (r = 0.72) were noted only between the T21 time constant and BMORS force. These results demonstrate that water may contribute to the specific texture characteristics measured with subjective WB scoring (palpable hardness and rigidity) and BMORS (hardness and share force) in raw broiler breast fillets with the WB condition.

Predicting the compressive strength of tight sandstone based on the low field NMR and pseudo-triaxial compression measurements

The compressive strength is very important for petroleum and other engineering studies. However, the effect of pore size and fluid distribution on the rock’s strength is not fully understood. We developed comprehensive research to study the controlling factors of the compressive strength based on low field nuclear magnetic resonance (NMR) measurements and pseudo-triaxial compression test for tight sandstones. The relationship between the compressive strength and the NMR obtained parameters are investigated completely, aiming for a better estimation of the compressive strength using the NMR data. The result shows that the rock’s strength is strongly controlled by the pore size distribution and the fluid existing state. Generally, the compressive strength is negatively correlated with the average transversal relaxation time, the movable water saturation, and the porosity, but positively correlated with the irreducible water saturation. The result reveals that the rock with larger pore radius and higher percentage of movable fluid is easier to reach the failure state. Further, the precision of the empirical model by multiple regression of the geometric mean of the relaxation time and the porosity is greatly improved compared with the model established by the brittle minerals, which is potentially to be use for geophysical prospecting when the NMR logging data is available.

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]:&#x0D; 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].&#x0D; 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.

Temperature effect analysis of paste backfill rheological properties based on inter-particle potential and water evolution

This study focuses on investigating the rheological properties and micro-mechanisms of paste filling materials under varying temperatures, which is crucial for addressing the issue of transporting paste materials through pipelines at different temperatures. The rheological properties of Pure Tailing sand Paste Backfill (TPB) with a mass concentration set at 66% and Cement Paste Backfill (CPB) with a 1:4 ratio of the cementing agent were analyzed at different temperatures were compared and analyzed at different temperatures using rheometer, Zeta potential, and low-field nuclear magnetic resonance measurement technology. The study aims to identify the macroscopic trends in the dynamic yield stress and viscosity coefficient of paste slurry under temperature influence, and to determine the microscopic mechanisms of the competition between water activity and electrostatic interaction between particles. The study not only examines the characteristics of paste slurry at macro and micro levels but also provides a model of rheological parameters and temperature for the optimization of paste filling technology. Studies have shown that temperature has the opposite effect on dynamic yield stress and consistency factor, and both should be considered in practical applications.

Textural characterization of calcium salts-induced mung bean starch-flaxseed protein composite gels as dysphagia food

Effects of calcium gluconate (CG), calcium lactate (CL) and calcium dihydrogen phosphate (CDP) on the structural and functional properties of mung bean starch (MBS)-flaxseed protein (FP) composite gels were investigated to explore the feasibility of developing dysphagia food. The water-immobilizing, rheological and structural properties of MBS-FP composite gels adding different calcium salts (10, 30, and 50 mmol/L) were analyzed by low-field nuclear magnetic resonance measurement, rheological and textural analyses, fourier transform infrared spectroscopy, scanning electron microscopy and confocal laser scanning microscopy. Results showed that calcium salts imparted various soft gel properties to the composite gels by influencing the interactions between MBS and FP. Calcium salts could affect the conformation of amylose chains, accelerate the aggregation of FP molecules, and increase the cross-linking between starch and protein aggregates, resulting in the formation of large aggregates and a weak gel network. Consequently, calcium salts-induced composite gels showed lower viscoelastic moduli and gel strength than the control gel. In particular, different calcium salts had various impacts on the gel properties due to their diverse ability forming hydrogen bonds. Compared with CL and CDP, the gels containing CG presented the higher viscoelastic moduli and hardness, and possessed an irregular cellular network with the increased pore number and the decreased wall thickness. The gel containing 50 mmol/L CL had the highest water-holding capacity, in all the gels tested, by retaining more immobilized and mobile water in the compact gel network with larger cavities. The gels adding CDP presented lower hardness and gumminess due to the obvious lamellar structure within the network. International dysphagia diet standardization initiative (IDDSI) tests indicated that the gels adding CG and CL could be categorized into level 6 (soft and bite-sized) dysphagia diet, while the samples adding CDP could be classified into level 5 (minced and moist). These findings provide insights for the development of the novel soft gel-type dysphagia food.

Study on the quality change and deterioration mechanism of leisure dried tofu under different storage temperature conditions

The quality change and deterioration mechanism of leisure dried tofu (LD-tofu) were investigated during storage at 4 °C, 25 °C, and 37 °C for 150 d. The results indicated the protein content, fat content, carbohydrate content, and pH of LD-tofu significantly decreased, while the total viable counts and moisture content increased with a bigger storage time. Moreover, the hardness and springiness of LD-tofu stored at 4 °C and 37 °C for 150 d were 2.43 N and 0.932, as well as 1.44 N and 0.842, respectively. Insights from low-field nuclear magnetic resonance measurements revealed that the bound water in the LD-tofu could be transformed into free water, whereas the free water mobility increased significantly at 25 °C and 37 °C. Additionally, the peroxide value and thiobarbituric acid reactive substances level of LD-tofu stored at 25 °C and 37 °C increased, indicating that the high-temperature storage promoted lipid oxidation. Overall, concrete pieces of evidence were provided for the deterioration in the quality of LD-tofu under high-temperature storage due to changes to the protein gel network structure caused by protein oxidation, induced by lipid oxidation. This work paves the way for the development of reasonable storage programs for LD-tofu.

Investigations on asphaltene aggregate formation by high-field diffusion NMR and low-field ghost solvent NMR relaxometry

Aggregation of asphaltenes remains a scientific challenge. In the present contribution, at first, transverse magnetization relaxation (T2) data from low-field NMR measurements of the asphaltenes from heavy, medium-heavy, or light crude oil samples were recovered. Following this, diffusion ordered spectroscopy nuclear magnetic resonance (NMR) spectra of these asphaltenes were acquired to obtain average molecular weights (M w) of asphaltene aggregates. Analyzing the relaxation and diffusion behavior of asphaltene aggregates as a function of solution percentage and hence molecular weights are utilized to explain the difference between light, medium-heavy and heavy crude oil asphaltenes in aggregate formation. The main results suggest that light crude oil asphaltenes form a small but significant number of aggregates. In contrast, heavy crude oil asphaltenes demonstrate a more complicated picture at high concentrations with small, medium, and large aggregates. The relaxation behavior of medium-heavy asphaltenes is similar to those of heavy crude oil asphaltenes in diluted solutions and similar to light crude oil asphaltenes in concentrated solutions. Diffusion NMR results showed that the light crude oil asphaltene samples have a relatively smaller aggregate size, higher diffusion coefficient, and hence a smaller molecular weight than the samples extracted from heavy crude oils.

Porous Colloidal Nanoparticles as Injectable Multimodal Contrast Agents for Enhanced Geophysical Sensing.

Injecting fluids into underground geologic structures is crucial for the development of long-term strategies for managing captured carbon and facilitating sustainable energy extraction operations. We have previously reported that the injection of metal-organic frameworks (MOFs) into the subsurface can enhance seismic monitoring tools to track fluids and map complex structures, reduce risk, and verify containment in carbon storage reservoirs because of their absorption capacity of low-frequency seismic waves. Here, we demonstrate that water-based Cr/Zn/Zr MOF colloidal suspensions (nanofluids) are multimodal geophysical contrast agents that enhance near-wellbore logging tools. Based on experimental fluid-only measurements, MIL-101(Cr), ZIF-8, and UiO-66 nanofluids have distinct complex conductivity and/or low-field nuclear magnetic resonance (NMR) signatures that are relevant to field-deployed technologies, implying the potential to enhance near-wellbore monitoring of CO2 injection and associated processes with downhole logging tools. Small- and wide-angle X-ray scattering characterization of ∼0.5 wt % MIL-101(Cr) suspensions confirmed phase stability and provided insight into the fractal nature of colloidal nanoparticles. Finally, low-field (2 MHz) NMR measurements of MIL-101(Cr) nanofluid injection into a prototypical Berea sandstone demonstrate how paramagnetic high-surface area MOFs may dominate the relaxation times of hydrogen-bearing fluids in porous geologic matrices, enhancing the mapping of near-surface and near-wellbore transport pathways and advancing sustainable subsurface energy technologies.

Rapid characterization of crude oil by NMR relaxation using new user-friendly software

This study demonstrates the feasibility of using low-field nuclear magnetic resonance (LF-NMR) relaxometry for the identification and characterization of crude oils as an alternative and robust technique. In general, the NMR relaxometry is based on monitoring nuclear spin dynamics (molecular dynamics) and analyzing its dependencies on the physicochemical properties of samples. The approach reported in this study comprises the initial analysis of crude oils by several standard American Society for Testing and Materials (ASTM) methods followed by a series of routine LF-NMR measurements. The LF-NMR based method showed the following practical advantages: It is non-destructive, requires minimum sample preparation without hazardous solvents, which helps keeping analysis costs reasonably low. The NMR analysis itself is fast and takes a few seconds for a crude oil sample. The whole method workflow is simple and easy to perform in specially developed user-friendly software that was “trained” to determine physical properties including kinematic viscosity, density, oAPI gravity, sulfur content, total acid number, refractive index, specific gravity, asphaltene content, microcarbon residue of crude oils using empirical correlations between the oil properties and experimental NMR relaxation values.

Competitive adsorption in CO2 enhancing shale gas: Low-field NMR measurement combined with molecular simulation for selectivity and displacement efficiency model

CO2 enhanced shale gas recovery is considered to be a potential method of shale gas development and CO2 reduction. However, core experiments cannot independently analysis competitive adsorption when the partial pressure of CH4 in the core sample keeps changing during displacement. In this study, an experimental method based on low-field nuclear magnetic resonance (NMR) and in situ gas chromatography is developed to quantitatively analyze the competitive adsorption of shale particles. As was demonstrated in our previous study, the adsorption capacity of the nanopores at various pressures can be obtained from the transverse relaxation spectrum of NMR and the change in pressure in a reference cavity. By NMR experiment combined with gas chromatography, the competitive adsorption selectivity of CH4 and CO2 in nanopores is investigated. In addition, molecular simulations are used to simulate the competitive adsorption and selectivity of CO2 and CH4 in shale nanopores with different pore structures, sizes, and shapes. The results reveal that as the pressure, carbon dioxide mole fraction, temperature, and pore size increases, the competitive adsorption selectivity S decreases. However, it remains greater than one, which demonstrates that CO2 has a stronger adsorption ability than CH4. For shale gas development, as the total pressure decreases, the contribution of the competitive adsorption effect becomes significant. A competitive adsorption model for CO2 and CH4 is established, and it is shown to fit the experimental data and simulation data well at different pressures. Finally, based on single-component adsorption results, we can separate the different effects and predict the displacement efficiency, which may provide a criterion in field scale simulations.

Prediction of the stability and compatibility of Colombian heavy crude oils by 1D low field nuclear magnetic resonance relaxometry and chemometric methods

Stability and compatibility can be described by the insolubility number (IN), the solubility blending number (SBN) and the ratio (R) between them, which has become a critical index in daily refineries operation. In this work, a new methodology for predicting the stability and compatibility of heavy crude oils by 1D low field nuclear magnetic resonance (LF-NMR) relaxometry has been developed. Various chemometric models were developed to predict the IN,SBN and R properties of Colombian heavy crude oils (°API from 6 to 27), by integrating intervals of either the 1D free induction transverse magnetization decay curves (T2 FID) obtained with a low-field (LF) nuclear magnetic resonance (NMR) spectrometer, or their T2 relaxation distributions obtained via the inverse Laplace transform (ILT). Correlations between the relaxometry curves and said properties were evaluated using the principal component regression (PCR) and the partial least squares regression (PLSR) methodologies. The obtained prediction models yielded coefficients of determination (R2) above 95% with as few as 6 components and values of cross validated root mean squared error of prediction (RMSEP) as low as 0.71 for the IN, 2.37 for the SBN and of 0.03 for the R property, respectively. The best prediction models were attained using PLSR and employing the FIDs as the predictors. The use of chemometric predictive models from LF-NMR measurements represent a low-cost and faster alternative to estimate critical properties of the independent crude oils to be blended, and thus, will help in predicting the stability and compatibility of crude oil blends, which in turn may help accelerate the decision-making process in daily refineries tasks.

Application of a Modified Low-Field NMR Method on Methane Adsorption of Medium-Rank Coals

Methane adsorption capacity is an important parameter for coalbed methane (CBM) exploitation and development. Traditional examination methods are mostly time-consuming and could not detect the dynamic processes of adsorption. In this study, a modified low-field nuclear magnetic resonance (NMR) method that compensates for these shortcomings was used to quantitatively examine the methane adsorption capacity of seven medium-rank coals. Based on the typical T 2 amplitudes obtained from low-field NMR measurement, the volume of adsorbed methane was calculated. The results indicate that the Langmuir volume of seven samples is in a range of 18.9–31.85 m3/t which increases as the coal rank increases. The pore size in range 1-10 nm is the main contributor for gas adsorption in these medium-rank coal samples. Comparing the adsorption isotherms of these coal samples from the modified low-field NMR method and volumetric method, the absolute deviations between these two methods are less than 1.03 m3/t while the relative deviations fall within 4.76%. The absolute deviations and relative deviations decrease as vitrinite reflectance ( R o ) increases from 1.08% to 1.80%. These results show that the modified low-field NMR method is credible to measure the methane adsorption capacity and the precision of this method may be influenced by coal rank.

Assessing the Efficiency of Saturating Shale Oil Cores and Evaluating Hydrocarbon Gas Huff ‘n’ Puff Using Nuclear Magnetic Resonance

SummaryShale oil formations have a very low primary yield despite advances in multistage hydraulic fracturing and horizontal drilling. In so doing, gas huff ‘n’ puff (HnP), among other improved oil recovery methods, is implemented to recover more liquid hydrocarbons. Gas HnP has proven to be an effective recovery process in shales taking into account the fracture properties, fluid-fluid interactions, and gas diffusion controlled by matrix properties. However, a laboratory-scale understanding of the gas HnP mechanism proves challenging. At this scale, measuring saturation before and after HnP tests in a nonintrusive and nondestructive manner, and understanding rock properties that affect diffusion is essential. In addition to ascertaining how the multiscale pore systems and varying mineral composition of shales affect its evaluation. The nuclear magnetic resonance (NMR) is considered a suitable tool for estimating fluid content in shales and understanding rock/fluid interactions. Generally, synthetic oil samples are used on either outcrop core plugs or crushed reservoir samples for NMR measurements, which may not be representative of rock/fluid interactions in bulk shales.This study is focused on carrying out NMR tests with dead oil on reservoir core plugs at relatively different depths to determine an effective means of saturation and understand oil production due to gas HnP. Gas HnP experiments were performed at reservoir conditions (3,500 psi and 125°C) on representative rock types from the Lower Eagle Ford (LEF) interval. Low field NMR measurements were subsequently carried out on the LEF core plugs at different states: as-received, saturated, and after gas HnP. The results show that oil recovery due to gas HnP occurred mainly in the organic pores (OPs) and inorganic pores (IPs) and ranged from 48 to 56% of the oil-in-place with indications of adsorbed/trapped methane (CH4) and remaining heavier components. This plays a vital role in evaluating the HnP process to know the extent of invasion and remaining oil components.In saturating the core plugs, the optimum saturation period was found to be 2 weeks for the LEF shale at current conditions. This presents an idea of how long to saturate a shale oil core effectively before it is tested for gas HnP. On the basis of the impact of varying mineral composition on the recovery mechanism, we observed the LEF core plug with the highest clay content to have the least recovery. This is in line with a high T1/T2 ratio alluding to reduced mobility of fluids in the presence of clay minerals with relatively small sizes of clay porosity and adsorptive surfaces.

Methyl-grafted silica nanoparticle stabilized water-in-oil Pickering emulsions with low-temperature stability

HypothesisThe viscosity of water-in-oil Pickering emulsions may dramatically increase upon cooling. The solvation of the long-chain alkyl groups grafted on the particles stabilizer is the likely cause of the strong dependence of rheological property on temperature. Thus, we hypothesize that silica nanoparticles (NPs) grafted with short-chain alkyl groups can stabilize Pickering emulsions, yielding weakly temperature-dependent rheological property. ExperimentsUsing alkyl-grafted (methyl, octyl, and octadecyl) silica NPs as emulsifiers, the rheological properties and microstructure of the water-in-oil Pickering, as well as the solvation of the silica NPs, were studied using diffusing-wave spectroscopy microrheology measurements, confocal laser scanning microscopy, and low-field nuclear magnetic resonance measurements. FindingsThe use of methyl- and octadecyl-grafted silica NPs, which have almost identical optimum contact angles, to stabilize emulsions dramatically reduced the effect of cooling on the viscosity. Moreover, the emulsions stabilized by these methyl-grafted silica NPs exhibited nearly constant rheological properties as the temperature decreased from 75 to 5 °C. The nearly constant rheological properties are attributed to the nearly constant solvation in this temperature range. These materials have potential applications in the cosmetics and petroleum industries.

Water evolution and hydration kinetics of cement paste under steam-curing condition based on low-field NMR method

The presented study focuses on the water evolution and hydration characteristics of Portland cement paste under steam-curing condition. The detailed information concerning water consumption and micro-pore network as well as the corresponding hydration kinetics of hydrating cement paste (HCP) during steam-curing process were discussed based on the low-field nuclear magnetic resonance measurement. The results indicate that, within steam-curing period, most of the free water in HCP are distributed in smaller pores less than 500 nm. The water evolution rate of paste system can be divided into three stages, i.e. acceleration stage within heating period and the first 2 h of constant-temperature period, rapid low-down stages in later constant-temperature period and diffusion stage in rest period. The curing temperature predominantly controls the water evolution rate. Finally, the hydration kinetics model of paste within steam-curing period is established and verified by experiment.

Effect of myoglobin, hemin, and ferric iron on quality of chicken breast meat.

ObjectiveThe objective was to evaluate the impact of different forms of iron including myoglobin, hemin, and ferric chloride on the quality of chicken breast meat.MethodsChicken breast muscles were subjected to 1, 2, 3 mg/mL of FeCl3, myoglobin and hemin treatment respectively, and the production of reactive oxygen species (ROS) and malondialdehyde, meat color, tenderness, water holding capacity and morphology of meat was evaluated.ResultsHemin was found to produce more ROS and induce greater extent of lipid oxidation than myoglobin and ferric chloride. However, it showed that hemin could significantly increase the redness and decrease the lightness of the muscle. Hemin was also shown to be prominent in improving water holding capacity of meat, maintaining a relatively higher level of the immobilized water from low-field nuclear magnetic resonance measurements. Morphology observation by hematoxylin-eosin staining further confirmed the results that hemin preserved the integrity of the muscle.ConclusionThe results indicated that hemin may have economic benefit for the industry based on its advantage in improving water holding capacity and quality of meat.

Permeability dynamic variation of coal under various confining pressures using LFNMR relaxation method

Although an extensive literature has emerged on the use of low-field nuclear magnetic resonance (LFNMR) relaxation spectrometry for the determination of various petrophysical properties of conventional reservoir rocks, relative few papers have reported the use of LFNMR discovering coal characterizations, especially the permeability dynamic variation. In this study, LFNMR measurements were conducted to analyze the permeability dynamic variation under various confining pressures of three coal samples with different metamorphic grades and were compared with the conventional experimental and empirical calculating methods. The results show that low rank coal (MLC) has relatively higher permeability, poorer adsorption capacity, and weaker compressibility compared with medium (TLC) and high rank coals (DQC). The permeability of coal reservoir decreases under the effect of effective stress during coalbed methane (CBM) development, of which the decreasing rate is reduced with confining pressure increasing and Ro, max increasing. Both the empirical calculating and LFNMR evaluating methods can be used to reflect permeability of coal reservoirs under low confining pressure condition, while the LFNMR evaluating method is more suitable than the empirical calculating method to reflect coal reservoir permeability under high confining pressure condition.

Investigation on pore structure and multifractal of tight sandstone reservoirs in coal bearing strata using LF-NMR measurements

In this study, pore structures of tight sandstone reservoirs in coal bearing strata were evaluated by combining the low field nuclear magnetic resonance (LF-NMR) measurements with multifractal theory. The effects of petrophysical properties, pore structure parameters, and reservoir components on multifractal parameters in different probability measure areas were then discussed. The results show that tight sandstone reservoirs in coal bearing strata have complex pore structure, low porosity (2.43%–5.18%), low permeability (0.0005–0.0125 mD), and poor pore connectivity with significant multifractal characteristics. Multifractal characteristics are well correlated with petrophysical property, pore structure, and lithology, which is useful for evaluating pore structure heterogeneity of such tight sandstone reservoirs. Moreover, the multifractal parameters of different probability measure areas are strongly associated with petrophysical parameter porosity, whereas the multifractal parameters of low probability measure areas αmax, (Dmin-D0) are weakly related to the characteristics of pore structure parameters and reservoir components. This suggests that the multifractal parameters of the high probability measure areas are more sensitive than other multifractal parameters to the pore structure, and therefore can be chosen for effective pore structure characterization. Additionally, other parameters A, (D0-D1), and (D0-D2) can also reflect the property of pore structure to a certain extent.

Experimental study on methane hydrate formation in a partially saturated sandstone using low-field NMR technique

Kinetics of hydrate formation in the porous media is important for carbon storage and the feasibility assessment of developing natural gas hydrates. In this study, we used a novel and real-time monitoring apparatus which combined the hydrate formation system with the low-field nuclear magnetic resonance measurement system to study on the characteristics of methane hydrate formation in a partially saturated sandstone. Results show that hydrate coexists with water and methane in the sandstone at the end of methane hydrate formation by an excess-gas method. Magnetic resonance imaging shows that the spatial distribution of hydrate is affected by the initial distribution of water in the sandstone. Water content plays a role in controlling the termination of hydrate formation. Based on the transverse relaxation time distribution analysis, free gas exists mainly in the large pores, while methane molecules can enter the small pores by dissolution and diffusion, forming methane hydrate with water molecules in the absence of free gas. Methane hydrate is formed in the center of both large and small pores by the excess-gas method. The rate of methane hydrate formation is slower in the small pores than that in the large pores. The range of pore size gradually decreases with the hydrate formation.