T2 Cutoff Research Articles

Dynamic wetting mechanism of coal under different CO2 pressure: A new analytical basis through T2 cutoff

The technology of injecting carbon dioxide into coal seams to reduce greenhouse gas emissions and has brought attraction on the wettability of coal. As a fast and non-destructive method, nuclear magnetic resonance (NMR) is widely used in the evaluation of coal wettability, but the inconsistency of analytical basis makes the quantitative evaluation of coal wettability changes uncertain. In this study, based on NMR combined with centrifugal experiments, a novel analytical basis using irreducible water defined by T2 cutoff value was proposed to quantitatively analyze the dynamic wetting mechanism under different CO2 pressures. The results show that when T2 < 72.32 ms, the water in coal is irreducible water; when T2 > 72.32 ms, the water in coal is movable water. CO2 pressure hindered free water conversion to adsorbed and capillary water, but impacted adsorbed water more. Increased CO2 pressure caused the wetting porosity of coal to decrease from 1.62 % to 1.08 %, and coal gradually changed from water-wet to CO2-wet. The increase in CO2 pressure enlarged the CO2 aggregations in the seepage channel, thus weakening the wetting rate of water to coal. CO2 preferentially occupied small pores, which will hinder the migration of water into small pore spaces. Molecular diffusion controls water to achieve wetting equilibrium more than gravity/pressure difference and capillary force. As CO2 pressure increases, the wetting equilibrium time decreases.

Pore structure evolution of mortars with manufactured sand aggregate under the influence of aggregate size and water saturation environment

To investigate the effect of aggregate size on pore structure and pore evolution in water saturation of manufactured sand aggregate (MSA) mortars, five MSA mortars with small range of aggregate sizes were prepared and their pore characterization were monitored over 365 days. The findings showed that an increased surface volume ratio (SVR) leads to an increase in total and macroporous porosity, and three pores with different connectivity were quantified using double T2 cutoff method. Moreover, continued hydration by unhydrated cement caused an increase in micropores during the initial stage of service in a water-saturated environment for 365 days, and an increase in macropores at the later stage as a result of enhanced hydraulic solvation, furthermore, solvation was more significant in the mortar with larger SVR to the point where it eventually produced pores larger than 100 μm. This research would provide guidance for the durability evaluation of cement mortars.

Integrated geological quality evaluation using advanced wireline logs and core data: a case study on high clay shale oil reservoir in China

Abstract In the unconventional energy sector, shale oil is increasingly recognized as a crucial supplement to production. In recent years, China has made significant advancements in the development of shale oil. A unique type of pure shale reservoir in the Songliao basin, distinct from established shale oil reservoirs worldwide, has emerged as a focal point for exploration and research endeavors. This kind of shale exhibits enhanced heterogeneity, high clay content, intricate rock electricity relationship, posing significant challenges to formation evaluation. This study introduces conversion coefficients for the elements and minerals, a decision tree model, a variable T2 cutoff value method, and 2D NMR cluster analysis, all based on the integration of microimaging, spectroscopy, and 2D NMR logging. These novel approaches facilitate a comprehensive geological quality evaluation of key parameters, including mineral composition, lithology, effective porosity, total organic carbon content, fluid composition, and saturation characteristics within pure shale formations from the Songliao Basin. The established petrophysical model has been validated by core analysis data and successfully applied in exploration wells. Through systematic petrophysical analysis, the optimal landing point for horizontal wells was identified based on the identification of the best reservoir quality interval with high movable oil and oil saturation. The subsequent drilling of horizontal wells demonstrated the reliability of petrophysical evaluation in terms of oil production. This integrated evaluation method for pure shale holds reference significance for similar shale reservoirs in other blocks in the future.

Study on the fluidity of the pore-fracture binary system in a tight sandstone reservoir-NMR

Fluid movability in tight sands may not be accurately characterized by pore size-based classification methods solely because of the complex pore structure and heterogeneity in pore size. In this study, on the basis of casting thin slices and scanning electron microscope observation, pore structure was analyzed using mercury injection, NMR, and micron CT to classify and evaluate the tight oil reservoir. The experiment suggest that the quality of tight reservoir is determined by its pore structure, particularly the throat radius, with the microthroat being an essential factor in permeability. Uniquely, we divide the reservoir by Q-cluster with throat radius, displacement pressure, permeability and other parameters. Based on reservoir classification, this study proposed a method for studying the pore size classification of samples on the T2 spectrum by combining CT scanning with mercury intrusion and a NMR experiment. Pore fluids are generally classified into movable fluid and irreducible fluid by one or two NMR T2 cut-offs. The pore size distributions and capillarity boundaries are converted from T2 and mercury injection capillary pressure (MICP). We categorized pores into micropores (T2 < 1), macropores (T2 > 10, with T2 > 300 as fractures), and medium pores (the rest). The saturation of movable fluid and the percentage of micro-fractures can characterize the seepage characteristics of tight reservoirs, which is of great significance for the later periods of oilfield development.

Evolution of Pore Structure and Fractal Characteristics in Red Sandstone under Cyclic Impact Loading

Fatigue damage can occur in surface rock engineering due to various factors, including earthquakes, blasting, and impacts. The underlying cause for the variations in physical and mechanical properties of the rock resulting from impact loading is the alteration in the internal pore structure. To investigate the evolution characteristics of the pore structure under impact fatigue damage, red sandstone subjected to cyclic impact compression by split Hopkinson pressure bar (SHPB) was analyzed using nuclear magnetic resonance (NMR) technology. The parameters describing the evolution of pore structure were obtained and quantified using fractal methods. The development of the pore structure in rocks subjected to cyclic impact was quantitatively analyzed, and two fractal evolution models based on pore size and pore connectivity were constructed. The results indicate that with an increasing number of impact loading cycles, the porosity of the red sandstone gradually increases, the T2 cutoff (T2c) value decreases, the most probable gray value of magnetic resonance imaging (MRI) increases, the pores’ connectivity is enhanced, and the fractal dimension decreases gradually. Moreover, the pore distribution space tends to transition from three-dimensional to two-dimensional, suggesting the expansion of dominant pores into clusters, forming microfractures or even macroscopic fissures. The findings provide valuable insights into the impact fatigue characteristics of rocks from a microscopic perspective and contribute to the evaluation of time-varying stability and the assessment of progressive damage in rock engineering.

Study on the multifractal characterization and seepage of the shale matrix: A case study of the Longmaxi Formation in southwestern Sichuan Basin, China

The pore structure and heterogeneity of shale significantly impact the occurrence and permeability of shale gas. Studying these aspects is beneficial for exploring and developing shale gas. In this study, organic-rich shale from the Longmaxi Formation in the Luzhou-Changning area was selected as the research subject. Experiments, including spontaneous imbibition, pressure saturation, and nuclear magnetic resonance, were conducted to characterize the pore structure and heterogeneity of the shale in this area. Using multifractal theory, we analyzed and discussed the multifractal characteristics of pores with different connectivities in relation to permeability. The results indicate that the T2 cutoff value (T2f) of the shale is greater than the T2c value, suggesting that the pore size of connected pores exceeds that of pores retaining bound water. The sizes of connected pores primarily range from 1 to 30 nm, predominantly between 1 and 10 nm. Significant differences were observed in the multifractal spectrum functions under dry, spontaneous imbibition, and water-saturated conditions, reflecting varying degrees of heterogeneity. The multifractal parameters differ, with higher ΔD values under water-saturated conditions, indicating that pores with weaker connectivity enhance the overall heterogeneity of the shale when saturated. Conversely, lower ΔD values under dry conditions suggest less heterogeneity in pores containing bound water. Total organic carbon (TOC) and clay content were identified as the main factors influencing the development of connected pores. Based on these findings, a discriminant 3D diagram correlating permeability with porosity, tortuosity, and multifractal parameters (D0-Dmax) of strongly connected pores was established for the Luzhou-Changning area. This diagram serves as an effective tool for evaluating the flow capacity of shale reservoirs and offers guidance for identifying sweet spots within the reservoir.

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

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

A Method to Identify Pore Fluids in Heterogeneous Conglomerate Reservoirs Using a Nuclear Magnetic Resonance Log with Oil-Based Mud Invasion

Summary Nuclear magnetic resonance (NMR) logging has been extensively utilized for identifying pore fluids in recent years. However, after oil-based mud (OBM) invasion, OBM filtrate partially takes the place of the original fluid in the reservoir and the morphology of the NMR T2 (transverse relaxation time) spectrum changes. OBM invasion makes it difficult to identify the formation fluid using routine NMR fluid identification methods. In this study, we took heterogeneous conglomerate formation in the northwestern Junggar Basin as a case study and carried out core experiments under four conditions (viz., water-saturated, OBM displacing water, oil-saturated, and OBM displacing oil) and simulated the states of OBM invasion into water and hydrocarbon-bearing formation. Comparative analysis finds that when the OBM invades the water layer, the movable peak of the T2 spectrum primarily reflects the bulk relaxation characteristics of OBM filtrate, whereas when the OBM invades into the oil layer, the T2 spectrum may exhibit a three-peak distribution, where the first peak mainly indicates irreducible water, the second peak reflects OBM filtrate, and the third peak primarily reflects nondisplaced oil. To facilitate fluid identification, two T2 cutoffs are adopted to divide the T2 spectrum into three segments, and combined with the T2 geometric average, a fluid identification factor (ifluid) is proposed. Finally, identification criteria for reservoir type are established on the NMR logging and drillstem test data. The field application verifies the reliability of the proposed methods. These methods realize the identification of oil layers under OBM drilling and guide the subsequent production and development of oil reservoirs.

Determining the pore structure and fluid characteristics of different ranks of coal using nuclear magnetic resonance

The microstructure of coal reservoirs and their fluid-endowment characteristics are important indicators for evaluating coalbed methane during mining. This study aimed to investigate the influence mechanism of the nanopore structure of different coal ranks on the fluid distribution characteristics. Low-field nuclear magnetic resonance (NMR), centrifugal force, and heat treatment tests were conducted. The results indicated that as the degree of coal metamorphism increases, micro-transition pores increase significantly, mesopores–macropores decrease, and the nonhomogeneity of the pores increases. The optimum centrifugal forces for low-, middle-, and high-rank coals were 1.68, 1.08, and 1.08 MPa, respectively. The corresponding mean T2C1 (first T2 cutoff) values were measured as 8.01, 1.61, and 5.09 ms, respectively, while the mean T2C2 (second T2 cutoff) values were 0.23, 0.26, and 1.25 ms, respectively. Pore sizes less than 11.6 nm indicate unrecoverable fluid, those higher than 88 nm indicate free fluid, and the rest (11.6–88 nm) indicate capillary bound fluid. As the degree of coal metamorphism increases, free fluid saturation decreases, capillary bound fluid saturation increases and then decreases, and unrecoverable fluid saturation increases.

Evaluation method of oil saturation index OSI for shale oil reservoir based on well logging data

Oil saturation index (OSI) serves as an important indicator for potential movable hydrocarbons evaluation of shale oil reservoirs, which is mainly obtained through rock pyrolysis experiments. A new method is proposed to evaluate the OSI of shale quantitatively by NMR logging. The OSI value can be accurately obtained through the experimental measurement of organic carbon content (TOC) and rock pyrolysis of shale samples, which can identify the development of mobile hydrocarbons. Subsequently, the mobile fluid porosity can be obtained based on NMR logging. In order to establish the relationship between OSI value and mobile fluid porosity, it is important to determine the T2 cutoff value corresponding to the mobile fluid porosity. Take shale samples from the first member of the Qingshankou Formation (“Qing 1 Member”) as an example, based on 2D NMR experimental analysis in three different states (original, dried state at 105°C, saturated kerosene), the NMR T2 cutoff value of movable fluid porosity in the shale of Qing 1 Member is clarified as 8 ms. Integrating rock pyrolysis and 2D NMR experiments, it suggests that the NMR bin porosity with T2&amp;gt;8 ms has a good linear relationship with the OSI value obtained by pyrolysis analysis. The NMR bin porosity with T2&amp;gt; 8 ms reflects the OSI value of shale effectively. The larger the NMR bin porosity with T2&amp;gt;8 ms, the higher the mobile oil content of shale reservoir, which is consistent with the understanding of oil-bearing large pores in the Gulong Shale. The NMR bin porosity can continuously evaluate the vertical variation of the mobile hydrocarbon content. Compared with the traditional experimental measurement of finite depth points, this method has significant advantages, and can avoid the possibility of missing potentially movable oil layers.

Shale primary porosimetry based on 2D nuclear magnetic resonance of T1-T2

Porosity, a key parameter in assessing the physical properties of shale reservoirs and the reserves, is of great significance to the selection and evaluation of shale sweet spots. There are many methods at present to characterize shale porosity, most of which are aimed at post-core cleaning shale, such as those involving helium and saturated fluid (namely liquid-involved porosimetry). However, due to the low efficiency of shale core cleaning and the possible damage to pore structure during the core cleaning process, it's hard to guarantee the accuracy of porosity measurement. In this regard, we resort to the two-dimensional (2D) nuclear magnetic resonance (NMR) technology of T1-T2 in characterizing the primary shale porosity with samples taken from pressure coring in the 4th member of Shahejie Formation (Sha 4 Member) in well Fanxie 184 in the Jiyang Depression. Moreover, comparative experiments of shale porosity measurement by three methods, namely the simultaneous distillation extraction (SDE), helium and fluid measurement, are carried out simultaneously. The results show that the values obtained by SDE, gas and liquid measurement are similar, which are about 0.6 times of 2D NMR porosimetry. Core cleaning efficiency tends to seriously affect the results involving gas and liquid. In addition, the core cleaning treatment is bound to change the shale pore structure, and this is especially true in clay which tends to swell; consequently, porosity results are to be distorted by gas and liquid methods. It is thereby recommended to utilize the 2D NMR technology to characterize the primary total porosity of shale samples without core cleaning. The effective porosity of samples from pressure coring is determined by T2 cutoff value of around 0.3 ms.

Applications of Two-Dimensional Laboratory Higher-Frequency NMR in Unconventional Shale Characterization

The complexity of the microstructure and fluids in unconventional reservoirs presents challenges to the traditional approaches to the evaluation of geological formations and petrophysical properties due to the low porosity, ultralow permeability, complex lithology, and fluid composition. Nuclear magnetic resonance (NMR) techniques have been playing major roles in unconventional shale characterization in the last decades as NMR can provide critical information about the reservoirs for quantifying their petrophysical parameters and fluid properties and estimating productivity. Laboratory NMR techniques at higher frequency (HF), e.g., 23 MHz, especially two-dimensional (2D) T1-T2 mapping, and their applications have been essential for the noninvasive characterization of tight rock samples for identifying kerogen, bitumen, heavy or light hydrocarbons, and bound or capillary water. Traditional T2 cutoffs, established with low frequency (LF) NMR, no longer apply and need new definitions to reflect the inferences from water and hydrocarbons separately. The crushed rock analysis method, as applied to unconventional formations, has been successful in evaluating total porosity and water saturation but also suffers from inconsistency in results due to desiccation and solvent effects. In the past decade, the oil and gas industry has witnessed significant development of HF NMR techniques that couple advances in petrophysics, petroleum engineering, and geochemistry with a broad range of applications. It is necessary to review such technological advances and draw conclusions to benefit unconventional core analysis programs. This article will summarize key advances in laboratory NMR applications in unconventional shale characterization, including monitoring processes of liquids equilibrium, desiccation, and imbibition in fresh shale samples, determination of activation energy of hydrocarbons in shales, monitoring changes in a shale sample during liquid flooding experiments, and direct measurements on kerogen.

Matrix decomposition methods for accurate water saturation prediction in Canadian oil-sands by LF-NMR T2 measurements

This article presents a novel method for quantifying water saturation in oil-sand reservoirs by employing 1D low-field nuclear magnetic resonance (LF-NMR) spin-spin relaxation and bulk density measurements as indicators of pore volume variations. One of the challenges in accurately determining the volumes of bitumen and water in oil-sands is the effective separation of their overlapping T2 signals, attributed to similar spin-spin relaxation decay times and diffusive coupling. Conventional methods require deconvolution of T2 peaks and or experimentation to determine T2 cutoff values, differentiating between bitumen and water signals, notably capillary and clay-bound water. In contrast, our approach predicts the proportion of water by utilizing matrix decomposition methods to compress the T2 relaxation distribution and extract significant components. These components subsequently train the regression model, facilitating the accurate estimation of relative water saturation percentages.The NMR dataset was obtained by benchtop LF-NMR T2 measurements from 82 oil-sand samples, with preserved bitumen and water saturations at both reservoir and ambient temperatures (6 °C and 25 °C), yielding 164 observations. We examined four matrix decomposition methods, including principal component analysis, its variation integrating a kernel function, canonical correlation analysis, and partial least squares regression. X-ray CT measurements and Dean-Stark extraction ascertained the respective sample bulk densities and fluid-solid volume proportions.The PCA model prediction statistics (RMSE = 0.86%, R2 = 0.84), indicate its application can be extended for saturation prediction from NMR and bulk density well logs. Moreover, we underscore the importance of incorporating bulk density measurements and establish the statistical and physical correlations between these measurements and NMR T2 relaxation, providing insights into the approach's efficacy and causality.

A novel method for quantitative evaluation of oil content and mobility in shale oil reservoirs by NMR logging: a case study of the inter-salt shale oil in the Jianghan Basin

The evaluation of oil content and mobility in shale oil reservoirs is the key to the optimization of the "sweet spot" of shale reservoirs and the evaluation of available resources. In order to address the challenge of quantitative evaluation of oil content and mobility in shale oil reservoirs, a combined multi-temperature pyrolysis and NMR experimental platform and experimental procedure are innovatively designed and implemented in this paper. The experiments reveal the NMR T2 distribution characteristics of hydrocarbon components in different reserve states. Accordingly, the NMR T2 cutoff values of different hydrocarbon components are determined, and the quantitative evaluation method based on NMR logging for total oil content and movable hydrocarbon content is established. The method has been applied to the inter-salt shale oil BYY2 well in Jianghan Oilfield, and the results show that the total porosity of the shale reservoir in the Qian 4 sub-Member is similar, but the total hydrocarbon content (0.04 g/kg∼16.0 g/kg) and the movable oil content (0.02 g/kg∼4.9 g/kg) are significantly different. Compared with the preferred scheme of reservoir based on porosity, accurate quantitative evaluation results of oil content and mobility based on logging provide a more straightforward indication of the resource potential of the reservoir that is available for exploitation. The experimental scheme of multi-temperature pyrolysis-NMR and the quantitative evaluation method for oil content and motility based on NMR logging will provide an important basis for resource evaluation, optimal formation selection and efficient development of shale oil reservoirs.

Identification and quantification of soil water components in kaolin by thermogravimetric and kinetic analysis

Different types of soil water, such as bound water and capillary water, have distinct effects on the physicochemical and engineering properties of soils, particularly unsaturated clayey soils. Therefore, it is crucial to develop an accurate and physically meaningful experimental method for identifying and quantifying these components. This study pioneers the use of a multi-step kinetic model to identify and quantify different soil water components across a wide range of relative humidity (RH) using thermogravimetric analysis (TGA) data. To validate the determined kinetic parameters (i.e., activation energy, preexponential factor, and reaction model) and the identification and quantification results of soil water components, TGA with multiple heating rates, nitrogen adsorption method, cation exchange capacity measurement, and nuclear magnetic resonance (NMR) were performed on kaolin samples equilibrated under various RH conditions. These experimental results cross-validate the superior performance of the kinetic model in determining soil water components and predicting the thermal desorption behaviors of soil water. Based on the cross-validation results, the soil water components obtained from the kinetic analysis are further identified as tightly-bound, loosely-bound, and capillary water, which exhibit variations consistent with empirical soil water isotherm models. The T2 cutoff value between bound and capillary water is determined to be 1.79 ms based on TGA and NMR results. The determined thermal kinetic parameters of different soil water components can exhibit their distinct retention mechanisms. The method and results in this study provide a new perspective on identifying different soil water components, as well as understanding the mechanism of soil-water interactions in unsaturated soils.

A method to classify coal pore system by using cumulative amplitude ratio and its dynamic variation

AbstractAs coal pore development is decisive for choosing the engineering site and predicting the CO2 storage capacity, this paper provides a new method to define the double T2 cutoff values by using cumulative amplitude ratio measured by nuclear magnetic resonance measurements, classifies the coal pore systems, and analyzes the influences on cumulative amplitude ratio. The following cognitions are achieved. The minimum ratio always varies narrowly and ranges from 0.9 to 1.1, which is quite stable and approximately equals to 1. Ranges of maximum and average ratios are 1.2–3.5 and 1.1–1.8, respectively. T2c1 represents the dividing point of diffusion pore and permeation pore, and its average value is about 4.1 ms. T2c2 represents the dividing point of permeation pore and cleat, with an average value of about 81.9 ms. The volumetric proportions of diffusion pore range from 1.5% to 76.2%, with an average value of 34.6%; the volumetric proportions of permeation pore are from 14.9% to 98.5%, with an average of 46.8%; while the volumetric proportions of cleat are between 8.4% and 57.5%, with an average of 26.6%. According to the different influencing degrees on maximum and average ratios, three types of parameters can be divided. The first type is strong correlation parameters and includes permeability, volumetric percentage of cleat, and relative volumetric percentage of cleat. The second type is medium correlation parameters, such as volumetric percentage of diffusion pore. The third type is weak correlation parameters, including T2 cutoff values, porosity, and maximum vitrinite reflectance. © 2023 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Predicting irreducible water saturation of unconventional reservoirs by using NMR T2 spectra: Methods of morphological division and fractal models

AbstractIrreducible water saturation restricts an efficient petroleum drainage in unconventional reservoirs. T2 cutoff value identification by using NMR T2 spectrum is the key to clarifying irreducible water saturation. In this paper, saturation and centrifugal T2 spectra of sandstone and coal samples were carried out to calculate T2 cutoff value, with methods of single fractal dimension, multi‐fractal dimension, and spectrum morphological discrimination; In addition, the applicability of these three methods in characterizing T2 cutoff was discussed. The parameters related to T2 cutoff can be divided into two types: (1) The first type is morphological parameters including main peak position ™ and smaller pore volume percentage (SPVP); with an increase of T2 cutoff, TM increases linearly and SPVP decreases exponentially, and the correlation between SPVP and T2 cutoff is stronger than that of TM; (2) Second type is fractal parameters of D2 (larger pore), D−10‐ D10 and D−10/D10; with the increase of T2 cutoff, all single and multi‐fractal dimensions increase linearly, and correlation between D2 and T2 cutoff is stronger than that of multi‐fractal dimension. When calculating the T2cutoff of samples with developed macro‐pores, spectrum morphological methods should be preferentially used, while the fractal dimension discrimination methods need to be used for T2cutoff of samples with developed micro‐pores.

P-149 Time is over: time-lapse technology to set time cut-offs defining embryo developmental incompetence

Abstract Study question Can time-lapse technology (TLT) discriminate developmentally incompetent embryos through time cut-offs of fertilization and cleavage stages? Summary answer TLT identifies developmentally incompetent embryos with high precision, through cut-offs of tPNa, tPNf, t2, t4 and t8. No clinically-applicable cut-offs were found for blastocyst euploidy. What is known already TLT is instrumental for continued and undisturbed observation of embryo development. This has produced morphokinetic algorithms aimed at selecting embryos able to generate a viable pregnancy. Such efforts have had limited success. Regardless, the potential of this technology for improving multiple aspects of the IVF process remains considerable. Specifically, TLT could be harnessed to discriminate developmentally incompetent embryos: i.e., those unable to develop to the blastocyst stage or affected by full-chromosome meiotic aneuploidies. If developed, this application would prevent the non-productive use of such embryos, improving laboratory and clinical efficiency and reducing costs derived from unproductive embryo transfer and cryopreservation. Study design, size, duration The training dataset involved embryos of PGT-A cycles cultured in Embryoscope with single- media (836 euploid blastocysts, 1179 aneuploid and 1874 arrested embryos; 2013-2020). Selection criteria were ejaculated sperm, fresh own eggs, trophectoderm biopsy, and comprehensive-chromosome-testing to diagnose non-mosaic aneuploidies. Out-of-sample (30% of training), internal (299 euploid blastocysts, 490 aneuploid and 680 arrested embryos; 2021- 2022) and external (97 euploid, 110 aneuploid, 603 untested blastocysts and 514 arrested embryos, 2018 to early-2022) validations were conducted. Participants/materials, setting, methods A training dataset (70%) was used to define thresholds. Several models were generated by fitting outcomes to each timing (tPNa-t8) and maternal age. ROC-curves pinpointed in-sample classification values associated with 95%, 99% and 99.99% true-positive-rate for predicting incompetence. These values were integrated with upper limits of maternal age ranges (&amp;lt;35, 35-37, 38-40,41-42 and &amp;gt; 42 years) in logit functions to identify time cut-offs, whose accuracy was tested on the validation datasets through confusion matrices. Main results and the role of chance For developmental (in)competence, the best performing (i) tPNa cut-offs were 27.8hpi (error-rate: 0/743), 32.6hpi (error-rate: 0/934), 26.8hpi (error-rate: 0/1178), 22.9hpi (error-rate: 1/654,0.1%), and 17.2hpi (error-rate: 4/423,0.9%) in the &amp;lt;35, 35-37, 38-40, 41-42 and &amp;gt; 42 years groups; (ii) tPNf cut-offs were 36.7hpi (error-rate: 0/738), 47.9hpi (error-rate: 0/921), 45.6hpi (error-rate: 1/1156,0.1%), 44.1hpi (error-rate: 0/647), and 41.8hpi (error-rate: 0/417) in the &amp;lt;35, 35-37, 38-40, 41-42 and &amp;gt; 42 years groups; (iii) t2 cut-offs were 50.9hpi (error-rate: 0/724), 49hpi (error-rate: 0/915), 47.1hpi (error-rate:0/1146), 45.8hpi (error-rate: 0/636), and 43.9hpi (error-rate: 0/416) in the &amp;lt;35, 35-37, 38-40, 41-42 and &amp;gt; 42 years groups; (iv) t4 cut-offs were 66.9hpi (error-rate: 0/683), 80.7hpi (error-rate: 0/838), 77.1hpi (error-rate:0/1063), 74.7hpi (error-rate: 0/590), and 71.2hpi (error-rate: 0/389) in the &amp;lt;35, 35-37, 38-40, 41-42 and &amp;gt; 42 years groups; (v) t8 cut-offs were 118.1hpi (error-rate: 0/619), 110.6hpi (error-rate: 0/772), 140hpi (error-rate: 0/969), 135hpi (error-rate: 0/533), and 127.5hpi (error-rate: 0/355) in the &amp;lt;35, 35-37, 38-40, 41-42 and &amp;gt; 42 years groups. tPNf and t2 showed a significant association with chromosomal (in)competence, also when adjusted for maternal age. Nevertheless, relevant cut-offs were not clinically applicable. Limitations, reasons for caution Study limits are its retrospective design and datasets unbalanced towards advanced maternal age cases. The potential effects of abnormal cleavage patterns were not assessed. Larger sample size and external validations in other clinical settings are warranted. Wider implications of the findings If confirmed by independent studies, this approach could significantly impact on the efficiency of ART reducing the workload (extended culture, cryopreservation, and transfer) associated with embryos that ultimately are developmentally incompetent and should not be considered for treatment. Pending validation, these data might be applied also in static settings. Trial registration number N.A.

Evolution Characteristics of Coal Microstructure before and after Supercritical CO2 Treatment Based on the L-Weighing-LNMR Method

To accurately and quantitatively characterize the evolution of coal microstructures before and after supercritical CO2 treatment, this paper proposes a microstructural analysis for coal-rock based on low-field nuclear magnetic resonance (LNMR) technology, the L-weighing method. The experimental results of the L-weighing method and the LNMR method were compared and analyzed. The results showed that there were differences between the experimental results of the L-weighing method and the LNMR method, but the overall laws were basically the same. The L-weighing method quantitatively characterizes the water content in coal and determines water consumption and microscopic component extraction in coal with supercritical CO2, while the LNMR method only determines the dissolution of H-containing substances in the coal by supercritical CO2. According to the combined analysis with the L-weighing method and the LNMR method, after the supercritical CO2 entered the coal, it consumed 0.33 g of water from the coal and extracted 0.32 g of microscopic components from the coal, reacted chemically with both water and microscopic components in the coal, and provided effective water consumption and extraction of the coal. The supercritical CO2 increased the saturable water in the coal by 0.71 g, the porosity by 1.57%, and the pore seepage volume by a factor of 1.10, which expanded the volume and increased the permeability of the coal. After the reaction with supercritical CO2, the centrifugal water loss of the coal increased by 0.16 g, the T2 cutoff (T2C) of the coal had shifted to the left by 0.31 ms, and the free water volume of the coal had increased by a factor of 1.15, which enhanced the pore connectivity in the coal. The water consumption, extraction, volume expansion, permeability increase, and pore connectivity increase were primarily responsible for the changes in the coal microstructure effected by supercritical CO2.

Rock Fabric of Tight Sandstone and Its Influence on Irreducible Water Saturation in Eastern Ordos Basin

After flowback, the residual fracturing fluid will reduce the gas seepage space and influence natural gas production, which attracts widespread attention. In this study, the irreducible water saturation was investigated, and its controlling factors were clarified. We target the Upper Paleozoic Taiyuan and Shihezi Formations, which belong to a tight gas reservoir in the eastern Ordos Basin. The main experiments include porosity, permeability, mineral composition, nitrogen adsorption, mercury intrusion porosimetry, nuclear magnetic resonance, and high-speed centrifugation. The specific surface area is very low and varies from 0.95 to 4.03 m2/g, and the median pore-throat diameter ranges from 28.6 to 698.6 nm. Through the T2 cutoff value, the water saturation can be divided into movable water saturation (Smov) and irreducible water saturation (Sirr). Furthermore, the Sirr can be divided into water saturation in large pores controlled by the small throat (Sirrl) and water saturation controlled by the capillary force (Sirrc). In both formations, the Sirr has a negative relationship with porosity, permeability, and average pore diameter and exhibits a positive relationship with the specific surface area. The Sirrl has a positive relationship with the median pore-throat diameter in Taiyuan Formation, but the Sirrl has a weak relationship with the median pore-throat diameter in Shihezi Formation. The Sirrc has a negative relationship with porosity, permeability, and average pore diameter and displays a positive relationship with the specific surface area in Taiyuan Formation, but the Sirrc has a weak relationship with these parameters in Shihezi Formation. The relationship difference between Taiyuan and Shihezi Formations was mainly caused by the pore structure, demonstrated by the amplitude ratio in three peaks. Based on the above analysis, this study is conducive to understanding the mechanism of water occurrence and its controlling factors.