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The Triassic Yanchang Formation in the Pengyang area of Ordos Tianhuan depression is an important oil and gas formation. However, most of the oil pays in the study formations are low-resistivity or low-contrast reservoirs with low permeability, bringing challenges to the reservoir identification and evaluation by well logs. In this paper, we first measured the nuclear magnetic resonance (NMR), phase permeability, cation exchange capacity (CEC), and X-ray diffraction for core samples. Then, the genetic types for the low-resistivity pays were analyzed based on the experiment results, water analysis, and well log data collected. It was found that large variations of formation water salinity, high irreducible water saturation, and clay conductivity are the primary genetic types. Further, the random forest (RF) algorithm with sensitive parameter inputs was used to identify the oil, oil and water, and water layers. The anomaly of spontaneous potential (∆SP) that characterizes water salinity, the relative value of gamma ray log (∆GR) that describes the bound water content, resistivity, density, and acoustic logs were taken as sensitive logs according to the genetic analysis. Finally, this identification method was verified by comparison with the traditional crossplot method and oil test results. The identification accuracy of the RF is 90%, far higher than that by the crossplot method. [ABSTRACT FROM AUTHOR]

Both laboratory and downhole nuclear magnetic resonance (NMR) measurements are commonly used to calculate the pore size distribution (PSD) that is important in determining the reservoir storage capacity and evaluating producibility, etc. The surface relaxivity is a key parameter to calculate the PSD using NMR transversal relaxation time (T 2) distributions. Accurate surface relaxivity value would result in a reasonable PSD. In order to comprehensively study surface relaxivity, the conventional sandstone, tight sandstone, and shale samples are selected to perform experiments including porosity, permeability, NMR, mercury injection capillary pressure (MICP) and low temperature nitrogen adsorption (LTNA), etc. Three approaches, including LTNA, MICP, and Kozeny's equation, are used to determine the surface relaxivity. We find that for all samples, the surface relaxivity determined with Kozeny's equation is greater than that using LTNA and MICP data, indicating that surface relaxivity of smaller pores is less than that of bigger pores. It is also observed that the surface relaxivity of conventional sandstone is greater than that of tight sandstone and shales. The surface relaxivity of sandstone and shale samples are both affected by clay content. For shale samples, the surface relaxivity ranges from 3.41 μm/s to 9.79 μm/s and is influenced by organic matter contents as well. An equation for predicting surface relaxivity of shale is established. Finally, we propose an advanced method for calculating reasonable PSDs of sandstone and shale formation by the combination of two surface relaxivities, which could be applied to laboratory and field wells. • Three practical approaches are proposed to calculate the surface relaxivity, and the calculation results are discussed. • This paper provides insights into the effecting factors on the surface relaxivity. • An advanced method for calculating reasonable PSDs of sandstone and shale formation is proposed. [ABSTRACT FROM AUTHOR]

Bisphenol-A (BPA) is a representative exogenous endocrine disruptor, which is extensively composed in plastic products. Due to the capability of passing through the blood-brain barrier, evidence has linked BPA exposure with multiple neuropsychological dysfunctions, neurobehavioral disorders and neurodegenerative diseases. However, the underlying mechanism by which BPA induces neurodegeneration still remains unclear. Our study used human embryonic stem cells-derived human cortical neurons (hCNs) as a cellular model to investigate the adverse neurotoxic effects of BPA. hCNs were treated with 0, 0.1, 1 and 10 μM BPA for 14 days. Impacts of BPA exposure on cell morphology, cell viability and neural marker (MAP2) were measured for evaluating the neurodegeneration. The intracellular calcium homeostasis, reactive oxygen species (ROS) generation and organelle functions were also taken into consideration. Results revealed that chronic exposure of BPA damaged the neural morphology, induced neuronal apoptosis and decreased MAP2 expression at the level of both transcription and translation. The intracellular calcium levels were elevated in hCNs after BPA exposure through NMDARs-nNOS-PSD-95 mediating. Meanwhile, BPA led to oxidative stress by raising the ROS generation and attenuating the antioxidant defense in hCNs. Furthermore, BPA triggered ER stress and increased cytochrome c release by impairing the mitochondrial function. Ultimately, BPA triggered the cell apoptosis by regulating Bcl-2 family and caspase-dependent signaling pathway. Taken together, BPA exerted neurotoxic effects on hCNs by eliciting apoptosis, which might due to the intracellular calcium homeostasis perturbation and cell organellar dysfunction. Image 1 • Human embryonic stem cell-derived cortical neuron served as in vitro neural model. • BPA upregulated NMDARs and disturbed intracellular calcium homeostasis. • BPA induced mitochondrial dysfunction and endoplasmic reticulum stress. • BPA induced neural apoptosis and neuronal network damage. • BPA-triggered excitatory neurotoxicity alleviated by NMDARs antagonists. [ABSTRACT FROM AUTHOR]

Accurate estimation of hydrocarbon saturation is significant for log interpreters to evaluate tight sandstone formations. It is difficult to use conventional wireline logs to calculate hydrocarbon saturation in complex reservoirs. Dielectric dispersion logs are processed using dielectric models to obtain accurate saturation assessment, especially in high salinity shaly sand formations. However, the dielectric models consist of complex refractive index method model and shaly sand model ignore the impact of clay effects on complex refractive index method model, and the dielectric dispersion logs generated by them appear several unphysical phenomena in the clay‐bearing formations, such as the permittivity data at the highest frequency are greater than those at the second highest frequency and the conductivity data at the highest frequency are lower than those at the second highest frequency. This paper modifies the dielectric models by introducing a combined conductive phase in complex refractive index method model to correct the unphysical behaviours. Revised models are combined with four permittivity and four conductivity logs acquired by dielectric scanner at 24, 102, 360 and 960 MHz to inverse the water saturation, water salinity, textural index for water‐bearing pore and fraction of clay‐related phase. The complex refractive index method model interprets the logs measured at 960 MHz and shaly‐sand model interprets other dielectric dispersion logs. The particle swarm optimization algorithm is used to search inversion parameters. The results of forward simulation show that the revised models can correct unphysical behaviours of dielectric dispersion logs generated by the original models. Moreover, we apply original models and revised models to laboratory core data. The results of experiments show that the mean relative error values of the original models are 19.38% and 23.60% and of the revised models are 5.54% and 6.28% in two cases. It shows that the revised models are more accurate than the original models to interpret dielectric dispersion logs of tight sandstone reservoirs. [ABSTRACT FROM AUTHOR]

Abstract Understanding the complexity and heterogeneity of pore structure can improve the comprehensive characterization for complex unconventional reservoirs and better exploit those resources. In this paper, multifractal analysis was conducted on low temperature N 2 adsorption and NMR T 2 distribution for the pore structure investigation in Middle Bakken formation in Williston Basin, USA. Results show that the averages of specific surface area, total pore volume, the average pore size of five N 2 adsorption samples are 3.31 m2/g, 0.008 cm3/g, and 19.57 nm, respectively. Six NMR T 2 distributions are bimodal and the signals of left dominant peaks are mainly distributed between 0.3 ms and 10 ms. The T 2 logarithmic mean value ranges from 2.18 ms to 2.95 ms with an average value of 2.57 ms. Both N 2 adsorption isotherms and T 2 distribution demonstrated the multifractal nature of different pore sizes. The key multifractal parameter, singularity strength range (Δ α) calculated from N 2 adsorption and T 2 distribution are respectively distributed in scopes of 0.72–1.54 and 1.63–2.89, indicating that the heterogeneity of pore space from T 2 distribution is stronger than that from N 2 adsorption. It was observed that the specific surface, micro pore volume, and average pore size are correlated well with Δ α. There are no any correlations between Δ α and porosity and T 2lm, but the cumulative porosity and width of right secondary peaks have an impact on the Δ α , which means that the heterogeneity difference between the two methods is attributed by larger pore and micro fractures. Highlights • The pore structure of Middle Bakken formation was studied by NMR T 2 distributions and low temperature N 2 adsorption. • The multifractal theory was applied to Middle Bakken formation for insights into pore structure and heterogeneity. • The effect of larger pore or micro-fracture on the heterogeneity of pore space was revealed. [ABSTRACT FROM AUTHOR]

Abstract Thermal maturity is an important geochemical parameter for the study of source rocks in unconventional shale plays. Using well logs to estimate thermal maturity would overcome the discontinuity of core sample analysis and can provide continuous profiles. However, estimating thermal maturity from well logs, unlike total organic carbon (TOC) content has received less attention. In this paper, we used vitrinite reflectance (R o) to characterize thermal maturity and proposed a practical method to produce a continuous profile of thermal maturity from well logs. For this purpose, a maturity indicator (I m) regarding with kerogen element compositions and types was defined. I m was calculated for different kerogen types based on their H/C versus O/C atomic ratios. It was found that R o decreases with the I m of all three types of kerogen monotonically, which was used as a foundation for thermal maturity predictions. Then, the I m was related to the compensated neutron log (CNL) responses of kerogen by considering the variations in elemental compositions of organic matter with maturity. Based on known CNL response of major sedimentary minerals and pore fluids, a petrophysical equation was established to obtain I m from well logs. Finally, the proposed method was applied to Chang 7 Shale of Triassic Yanchang Formation of the Ordos Basin, China and the Bakken Shale of Williston Basin, North Dakota, USA, two major source rocks with different kerogen types and maturities. The results showed an acceptable agreement between lab measurements and predictions of R o with a good correlation coefficient, verifying the new method is effective and reliable. [ABSTRACT FROM AUTHOR]

Pore structure is a critical parameter to estimate the reservoir quality and evaluate the resource potential. However, the pore structure and heterogeneity of the unconventional tight oil reservoirs of Permian Lucaogou Formation of Jimusaer Sag, Junggar Basin are not studied well. In this paper, the multifractal analysis based on the NMR T 2 distributions was applied to investigate the pore structure and heterogeneity. The reservoir quality index ( RQI ) and flow zone indicator ( FZI ) were calculated using porosity and permeability. Two parameters T 35 and T 50 were newly defined as relaxation times corresponding to the 35% and 50% saturation on the T 2 reverse accumulative curve, respectively. The results showed that the RQI , and FZI values were extremely low, and that the NMR T 2 distributions of water saturated samples had much short relaxation components with no or little long relaxation components, indicating a complex and poor microscopic pore structure of tight oil rocks. The typical multifractal characteristics, such as the large values of singularity strength range (Δ α ), revealed that the pore structures of samples were strongly heterogeneous. It was also found that the clay contents have an obvious influence on the multifractal parameters, and the FZI and new defined T 35 are two good indicators for heterogeneity of pore structure. In addition, the feasibility and applicability of calculating the multifractal parameters from NMR and other well logs were discussed. [ABSTRACT FROM AUTHOR]

Determination of the total organic carbon (TOC) from well logs is an important step in formation evaluation of shale reservoirs. The ΔlogR model is one of the most commonly used methods in determining the TOC of the source rocks. Wang et al. (2016) made three revisions on ΔlogR model to enhance the prediction accuracy, one of which is to use a changeable slope of log 10 R t versus porosity logs to replace a fixed value. Based on the original ΔlogR model and Wang's revision, we propose an improved model for a better TOC estimation in this paper. Specifically, the approximate linear baseline is replaced by a theoretical one. Under this condition, both the slope and resistivity and porosity log values of the baselined rocks vary from depth to depth. The determination of theoretical baseline is presented, and the varied baseline log values are obtained by a simple mathematical technique. In addition to the shale play of Western Canada Sedimentary Basin, two study areas of Sichuan Basin and Ordos Basin in China, were used to assess the applications of the proposed model and its improvement over the original model. The analysis and discussions presented in this paper indicate that the improved model offers more reliable results in shale plays with large lithological variations. Also, the TOC content of the three study areas was estimated using the proposed model. The results showed that the TOC values estimated from well logs and core analysis are in good agreement. [ABSTRACT FROM AUTHOR]

Microplastics could accumulate and enrich antibiotics in the aquatic environment. Despite this, the joint effects of microplastics and antibiotics on aquatic organisms are not clear. Here, we investigated the changes of microbial interactions in both gill and gut of marine medaka exposed to polystyrene microbeads (PS) and/or tetracycline for 30 days by using co-occurrence network analysis based on 16S rRNA gene amplicon sequences. We found that the single and combined effects of PS and tetracycline were more profound on the gut than on the gill microbiome. SourceTracker analysis showed that the relative contributions from the gill microbiome to the gut microbiome increased under combined exposure. Moreover, the combined exposure reduced the complexity and stability of the gut microbial network more than those induced by any single exposure, suggesting the synergistic effects of PS and tetracycline on the gut microbiome. The PS and tetracycline combined exposure also caused a shift in the keystone taxa of the gut microbial network. However, no similar pattern was found for gill microbial networks. Furthermore, single and combined exposure to PS and/or tetracycline altered the associations between the gut network taxa and indicator liver metabolites. Altogether, these findings enhanced our understanding of the hazards of the co-occurring environmental microplastics and antibiotics to the fish commensal microbiome. [Display omitted] • Gut and gill microbial compositions of marine medaka were changed by exposure to PS and/or tetracycline. • Gill microbiome was more stable under combined exposure than gut microbiome. • PS and tetracycline altered the keystone taxa of the gut microbial networks. • PS and tetracycline disrupted the associations between gut microbiome and liver metabolites. [ABSTRACT FROM AUTHOR]

The nuclear magnetic resonance (NMR) technique is a crucial means for formation evaluation. It can provide an accurate set of formation parameters in single-phase-flow reservoirs, such as porosity, permeability, and pore structure distribution; however, in most cases, there are hydrocarbon-water two-phase fluids in the reservoirs. The secondary change of the T 2 distribution makes the accuracy of the evaluation a challenge. Hence, it is necessary to clarify the impact of changes in hydrocarbon content on the response of NMR signals before using the traditional evaluation methods. In this paper, we analyzed the response mechanism of NMR T 2 distribution under different saturation conditions. Based on the theoretical derivation, we established a nuclear magnetic model that describes the relation among the T 2 geometric mean value of water signal, hydrocarbon signal, and water saturation. The accuracy of each model part was verified by numerical simulation. In addition, the calculation results in core samples show that the proposed model is more effective and reliable than two existing models (the T2 saturation ratio model and the Xiao empirical model), especially in extreme conditions (irreducible water and hydrocarbon saturated samples). Finally, we applied the proposed model to field application in the Tertiary formation in the Bohai Bay Basin, China, which achieved good effects in the NMR fluid substitution and the NMR saturation evaluation. • The relation among NMR T 2gm of the water, hydrocarbon signal and the water saturation could be expressed mathematically. • A new model was established for characterizing the NMR response in hydrocarbon bearing rocks. • Compared with the traditional model, the new model was proved to be better regional adaptability and stability. • The model could be used for NMR fluid substitution and saturation evaluation in hydrocarbon bearing formation. [ABSTRACT FROM AUTHOR]

Wet precipitation, as an important process of geochemical cycling and the most effective way of cleaning fine atmospheric particles (PM 2.5), can introduce the toxic substances in the atmosphere into the water environment. The adverse effect of wet precipitation of PM 2.5 on marine fish is still unclear. In this study, PM 2.5 samples were collected from six locations along coastal areas of the south China sea for 30 days and used to simulate the impacts of multiday discontinuity wet precipitation of PM 2.5 on marine medaka (Oryzias melastigma) in the case of 30 days discontinuity heavy rain (rainfall ≥ 7.6 mm/h and persist 1 h each day). Results showed that wet precipitation of PM 2.5 significantly inhibited the body weight gain of fish. In accordance, the size and number of lipid droplets in liver of the exposed groups were lower than those in normal control (NC) group. The expressions of genes involving in lipid degradation including lipoprotein lipase gene (LPL) and carnitine palmitoyltransferase gene (CPT) were up-regulated after exposure. The composition, diversity and function of gut microbiome were affected by wet precipitation of PM 2.5. PM 2.5 from industrial areas that have higher concentrations of metal profiles show more obvious impacts than PM 2.5 from agricultural leisure areas that possessed lower concentrations. All together, the results indicated that wet precipitation of PM 2.5 can decrease the diversity of gut microbiome, affect the lipid metabolism, and finally suppress the growth of marine medaka. It confirmed the potential ecological risks of long-term rainfall in air pollution areas to the aquatic organisms. Unlabelled Image • The impacts of PM 2.5 wet precipitation on the lipid metabolism in fish were studied. • Long-term PM 2.5 wet precipitation affects fish growth. • Upregulation of genes related to inflammation, antioxidase, and lipid metabolism was observed. • Long-term PM 2.5 wet precipitation disturbs fish gut microbiota. • Long-term rainfall in air-polluted area has potential risk on aquatic organism. [ABSTRACT FROM AUTHOR]

Hydrocarbon saturation is an important petrophysical parameter in reservoir evaluation and reserve calculation. Dielectric dispersion logs have been widely used to estimate the hydrocarbon saturation, especially in high salinity shale formations. However, there is still room to improve the accuracy of interpretation of dielectric dispersion logs. In this paper, we used two interpretation models combined four dielectric permittivity and four conductivity logs measured by Array Dielectric Tool (ADT) at four frequencies to predict the hydrocarbon saturation in shale oil reservoirs, Triassic Yanchang Formation, Ordos Basin, China. The logs measured at the highest frequency are interpreted by the Complex Refractive Index (CRIM) model. And the other three frequencies measured logs are processed by the shaly sandstone (SHSD) model. Based on the two models, simulated annealing algorithm is selected to calculate water saturation and rock textual parameter, the dispersive phase fraction, and water salinity. Besides, accurate porosity, dielectric permittivity of rock matrix, and temperature are input information to the proposed method. The proposed method is applied to shale oil reservoirs of Triassic Yanchang Formation in two wells. The effectiveness and reliability of proposed model is verified by synthetic log responses. The mean relative error between synthetic and field logs is small. The predicted hydrocarbon saturation is consistent with core data, and its variation is consistent with characteristics of NMR T 2 distributions, verifying the accuracy and reliability of proposed method and inversion results. Our estimated hydrocarbon saturation of the two wells is about 30%, showing a good oil generation potential of the studied shale oil reservoirs. [ABSTRACT FROM AUTHOR]

The Lucaogou Formation in Jimuaser Sag of Junggar Basin, China is a typical tight oil reservoir with upper and lower sweet spots. However, the pore structure of this formation has not been studied thoroughly due to limited core analysis data. In this paper, the pore structures of the Lucaogou Formation were characterized, and a new method applicable to oil-wet rocks was verified and used to consecutively predict pore structures by nuclear magnetic resonance (NMR) logs. To do so, a set of experiments including X-ray diffraction (XRD), mercury intrusion capillary pressure (MICP), scanning electron microscopy (SEM) and NMR measurements were conducted. First, SEM images showed that pore types are mainly intragranular dissolution, intergranular dissolution, micro fractures and clay pores. Then, capillary pressure curves were divided into three types (I, II and III). The pores associated with type I and III are mainly dissolution and clay pores, respectively. Next, the new method was verified by "as received" and water-saturated condition T2 distributions of two samples. Finally, consecutive prediction in fourteen wells demonstrated that the pores of this formation are dominated by nano-scale pores and the pore structure of the lower sweet spot reservoir is more complicated than that in upper sweet spot reservoir. [ABSTRACT FROM AUTHOR]

• The spontaneous imbibition (SI) and displacement characteristics of mixed-wet tight sandstone reservoir are studied by high-precision balance and NMR method. • The pores of tight sandstone were divided into adsorption pores, capillary bound fluid pores, and movable fluid pores by NMR T 2 spectra. • The SI and displacement behaviors of different pores were studied and compared. • The wettability of different pores in the mixed-wet rock was accurately characterized. Wettability is the key to understanding the complex seepage characteristics of tight sandstone reservoirs, which will affect the distribution of the residual hydrocarbon resources during the reservoir exploitation process. Complex wettability, strong heterogeneity and tiny pore space make it more challenging to study the imbibition characteristics of mixed-wet tight sandstone reservoirs. In this study, the spontaneous imbibition (SI) and displacement characteristics of mixed-wet tight sandstone reservoirs are studied by high precision balance and nuclear magnetic resonance (NMR) T 2 experiment. 3 rock plungers (A1, B1, C1) were put into the CaCl2 solution for SI, while their parallel samples (A2, B2, C2) were carried out SI experiments in the experimental oil. Then all the plungers are respectively displaced by the imbibition liquid after SI experiments. The weight and NMR T 2 spectra of the plungers in the above different conditions were measured. According to the experiment results, the pores of tight sandstone can be divided into 3 types with different wettability. The adsorption pores with T 2 distribution of 0.01–2.5 ms are water-wet, the capillary bound fluid pores with T 2 between 2.5 and 50 ms and the movable fluid pore with T 2 greater than 50 ms are mainly oil-wet. The SI and displacement behaviors of different pores were studied, the results show the oil absorbed per cc rock is more than 4 times that of brine. The weight gain after SI in the first 24 h can indicate the total SI result. The study results can accurately characterize the wettability of different pores and contribute to a novel wettability evaluation method in mixed wettable tight sandstone. [ABSTRACT FROM AUTHOR]

After long-term water injection, many developed oilfields in the Ordos Basin, China, have entered a period of the high water-cut stage. In waterflooded layers, formation water is a mixture of injected water and primary formation water. The variation of formation water salinity will significantly affect the evaluation of reservoirs using resistivity logging curves while having little effect on the NMR response. It lays a foundation for identifying fluid type and evaluation of waterflooding grade by NMR logging. However, in waterflooding layers with mixed wettability, the NMR T 2 responses are still complicated and unclear. In this paper, the tight sandstone samples with different wettability of Chang 6 and Chang 8 members of Triassic Yanchang Formation in the Ordos Basin are used to investigate the NMR experiments under three saturation states: water-saturated state, oil displacing to bound water state (abbreviated as oil flooding) and water flooding to the residual oil state (abbreviated as water flooding). Results show that the distributions of standard T 2 spectra, without an external gradient magnetic field, of the water-saturated state in mix-wetted samples is very close to that of after oil flooding. Thus, the standard T 2 spectra will be hard to distinguish the oil layer, water layer, and waterflooded layer of mix-wetted reservoirs. The diffusion coefficients of water and oil in pores differ, resulting in different shift T 2 spectra results under gradient magnetic field. Therefore, the shift T 2 spectra with the external gradient magnetic field and different echo time TEs were calculated and measured. When the echo time TE = 3.6 ms is adopted, the T 2 signal of water-saturated tight rock samples will be nearly distributed less than 100 ms with magnetic field gradient G = 18 G/cm, rather the T 2 signal greater than 100 ms is the oil signal. This characteristic makes the shift T 2 spectra outstanding in the fluid identification of tight reservoirs with complex wettability. Finally, based on this experiment, a residual oil index based on the shift T 2 spectrum is constructed to evaluate the flooded grades of tight waterflooding reservoirs. The evaluation results are consistent with the core description and oil test results in the study infilled wells. • The NMR experiments of mixed wetting and water wetting tight rock samples are performed and analyzed. • The standard T 2 spectra have difficult in distinguishing the oil and water layer of the mixed wetting reservoir. • Shift T 2 spectra have an excellent effect in identifying and evaluating fluid properties in complex wettability reservoirs. • The residual oil index is constructed by shift T 2 spectra to evaluate the waterflooded grades. [ABSTRACT FROM AUTHOR]

Fractal parameters of porous media have been a focus of study in petroleum engineering and hydrogeology for several decades because they provide an effective way to describe the complexity of pore structure across a wide range of scales. This paper combines 3D process-driven digital rock modeling with fractal analysis in order to understand the effect of varying sorting, compaction, cementation, and the fine grain fraction of binary models on the fractal parameters and specific surface area of porous media. Digital rock models (DRMs) were constructed to simulate sandstone using a process-driven modeling technique which simulates sedimentation. The fractal parameters of the resulting pore geometry were calculated using the box-counting method on 2D and 3D representations of the DRMs. Our simulations indicate that increasing compaction or cementation lead to significant decreases in fractal dimension, specific surface area (S Sp) and porosity, showing that these two diagenetic processes can affect the pore microstructure of the rock significantly. While interface fractal dimension (D i) and S Sp both increase slightly with decreases in sorting (grain size variety), and porosity decreases slightly. Examining the behavior of binary models, the porosity of our digital models shows a V-shaped curve as fine grain fraction increases from 0 to 1, consistent with, but higher than the theoretical values, which we attribute to incomplete packing of the grains arising from the simplified packing algorithm and finite boundary of models. The value of both S Sp and D i increase as the fine grain fraction increases. However, we must notice that the porosity may be underestimated, and the fractal dimension may be overestimated when we use models consisting of very fine spherical grains due to the effect of image resolution. • Construct 3D digital rock models by a process-driven method. • Calculate the fractal dimension of pore volume and pore/grain interface. • Reveal the effects of grain sorting, compaction and cementation on the fractal dimension parameters of porous media. [ABSTRACT FROM AUTHOR]

This study examines the evolution of China's education policy transmission system and analyzes its influencing factors. Data were collected from 5793 policy documents issued by the Chinese central government from 1978 to 2013. Using policy document bibliometrics and social network analysis, we studied the "citing-cited" policy reference relationship to undertake an in-depth characterization of the different stages of education policy and reform since China's economic reform and opening up in 1978. We determined changing trends in the education policy transmission system through using an environment-actors-institutions framework to uncover the factors behind such trends. Results showed that China's education policy transmission system has experienced a rapid expansion in the last few decades, and that characteristics are distinct from onetime period to another. Central governance ideologies had a relatively strong impact on the popular themes and topics of education policy in different stages. Meanwhile, the policy-issuing institutions played a significant role in the effectiveness of a certain policy measure. Additionally, the supervisory institution was an important factor that affected the degree of centrality in the evolving education policy network. [ABSTRACT FROM AUTHOR]

Numerous attempts have been conducted to construct a reliable model to relate petrophysical and geomechanical characteristics of shale to geochemical properties. In this study, continuous logs were built to predict the thermal maturity of the Bakken Formation from a set of petrophysical logs. First, dynamic modulus (E d) was created from shear and compressional sonic and, density logs and then converted to E i (nanoindentation based Young's modulus) using the existing experimental relationship between E d and E i. Next, continuous TOC logs were generated for the Bakken Shales based on an empirical relationship between well log derived E i and TOC contents that were measured in the lab. There was found an acceptable difference between estimated log-based TOC and measured values in three separate wells. Solid bitumen reflectance as a reliable indicator of thermal maturity was measured on all samples from the same wells in the scarcity/absence of vitrinite maceral. The relationships between GR/NPHI/RHOZ wireline logs versus solid bitumen reflectance (BR O %) as the maturity index was then investigated in twelve wells. Based on the strength or weight of the relationship between each log and BR O %, a new parameter "Ʈ" was defined to represent thermal maturity from well logs. A good agreement between parameter Ʈ and BR O % values was observed which provided an empirical equation to make the estimation of BR O % values for the whole length of the shale members possible. Ultimately, the continuity of BR O % values, would enable us to establish a relationship between BR O % and measured T max values to generate continuous T max logs for the Bakken Shale members. Using these newly developed well logs, it would become possible to make a 3D property models for BR O % and T max (the thermal maturity property cube) for an accurate petroleum system evaluation based on GR/NPHI/RHOZ logs. • A log-based continuous estimation of thermal maturity in source rocks is developed. • A new parameter "Ʈ" based on relationships between GR, CNL-FDC logs and solid bitumen reflectance is defined. • BR O % logs for the entire interval (depth) of the source rock (UB and LB) to interpret thermal maturity is developed. [ABSTRACT FROM AUTHOR]

Lucaogou tight oil reservoir, located in the Junggar Basin, Northwest of China, is one of the typical tight oil reservoirs. Complex lithology leads to a wide pore size distribution (PSD), ranging from several nanometers to hundreds of micrometers. To better understand PSD and fractal features of Lucaogou tight oil reservoir, the experiment methods including scanning electron microscope (SEM), rate-controlled mercury injection (RMI) and pressure-controlled mercury injection (PMI) were performed on the six samples with different lithology. The results indicate that four types of pores exist in Lucaogou tight oil reservoir, including dissolution pores, clay dominated pores, microfractures and inter-granular pores. A combination of PMI and RMI was proposed to calculate the overall PSD of tight oil reservoirs, the overall pore radius of Lucaogou tight oil reservoir ranges from 3.6 nm to 500 μ m. The fractal analysis was carried out based on the PMI data. Fractal dimension (Fd) values varied between 2.843 and 2.913 with a mean value of 2.88. Fd increases with a decrease of quartz content and an increase of clay mineral content. Samples from tight oil reservoirs with smaller average pore radius have stronger complexity of pore structure. Fractal dimension shows negative correlations with porosity and permeability. In addition, fractal characteristics of different tight reservoirs were compared and analyzed. [ABSTRACT FROM AUTHOR]

Effects of anisotropy and viscoelasticity of Earth media on Rayleigh waves propagation are studied by numerical simulation based on a finite-difference (FD) scheme, which calculates the spatial derivatives via a 12th-order staggered grid difference operator and the time derivatives through the fourth-order Runge-Kutta method. In the homogeneous half-space, the accuracy of FD algorithm is tested against the isotropic-elastic (IE) analytical solution; the calculation method of the theoretical phase velocities of the anisotropic-viscoelastic (AV) Rayleigh waves is developed to verify the correctness of modeling results; the characteristics of Rayleigh-wave are analyzed by comparisons among IE, anisotropic-elastic (AE) and AV modeling results in terms of the wave field snapshots, the synthetic seismograms, and the dispersive images, respectively. Then, the two-layer models and the four-layer models are utilized to further analyze the characteristics of Rayleigh waves in the AV layered media. Results show the substantial differences among these three kinds of media. Anisotropy of medium leads to the significant changes of Rayleigh-wave in amplitude, waveform and phase velocity due to anisotropy of velocity, but does not cause the phase velocity dispersion of Rayleigh-wave. Viscoelasticity of media arouses the amplitude attenuation and phase velocity dispersion of Rayleigh-wave. This is the first report for FD modeling and characteristics analysis of Rayleigh-wave in the AV media, which will provide a valuable reference for near-surface geophysical investigation. [ABSTRACT FROM AUTHOR]

Canopy stomatal ozone (O 3 ) flux ( F st,O3 ) in a plantation of Schima superba , an ecologically and economically important evergreen pioneer tree species in subtropical China, was quantified based on sap flow measurements during a 2-year period. Mean F st,O3 and accumulated F st,O3 ( AF st 0) were significantly higher in wet seasons from April to September (4.62 nmol m − 2 s − 1 and 35.37 mmol m − 2 , respectively) than in dry seasons from October to March (3.90 nmol m − 2 s − 1 and 24.15 mmol m − 1 , respectively), yet comparable between the 2 years of the experiment, being 4.23 nmol m − 2 s − 1 and 58.23 mmol m − 2 in April 2013–March 2014 and 4.29 nmol m − 2 s − 1 and 60.80 mmol m − 2 in April 2014–March 2015, respectively. At the diurnal scale, F st,O3 generally peaked in the early to middle afternoon hours (13:00–15:00), while the maximum stomatal conductance ( G st,O3 ) typically occurred in the middle to late morning hours (09:00–11:00). Monthly integrated AF st 0 reached the maximum in July, although accumulated O 3 exposure ( SUM 0) was highest in October. Seasonally or yearly, the accumulated O 3 doses, either exposure-based or flux-based, notably exceeded the currently adopted critical thresholds for the protection of forest trees. These results, on the one hand, demonstrated the decoupling between the stomatal uptake of O 3 and its environmental exposure level; on the other hand, indicated the potential O 3 risk for S. superba in the experimental site. Therefore, the present study endorses the use of sap flow measurements as a feasible tool for estimating F st,O3 , and the transition from the exposure-based toward flux-based metrics for assessing O 3 risk for forest trees. Further studies are urgently needed to relate stomatal O 3 uptake doses with tree growth reductions for an improved understanding of O 3 effects on trees under natural conditions. [ABSTRACT FROM AUTHOR]

The special intrinsic characteristics of shale formations, such as multiscale pore systems and complex mineral components, make the simulation of shale properties more difficult than that of sandstone properties. As such, one prerequisite of numerically predicting the physical properties of shale samples is to construct accurate shale models that include those special features. To this end, the study presents a novel hybrid stochastic modeling algorithm, called DEM-QSGSA, which integrates the discrete element method (DEM) and the quartet structure generation set algorithm (QSGSA), to build the necessary multicomponent and multiscale shale models. To investigate the effects of the components on the shale properties, the DEM-QSGSA was used to generate a dozen digital shale models with different mineral components containing quartz, feldspar, calcite, clay minerals, pyrite, and organic matter. The accuracy of the models was verified by comparing the characteristics of pore systems and the percentages of mineral components of the generated models with the ones of the SEM images of real shale samples. The electrical resistivity, bulk modulus, and shear modulus of these shale models were obtained using FEM. The results of electrical and elastic properties of these digital rocks indicate that the increase in abundance of the organic matter (OM) pores, intraparticle (intraP) pores, clay minerals, or OM results in a decrease in the electrical resistivity and elastic moduli when the pore systems of shale models are saturated with water. However, when the volume fraction of pyrite becomes larger, the elastic moduli increases and electrical resistivity decreases. Moreover, comparison of the sensitivity indices of the variables shows that pyrite has the largest effect on the electrical and elastic properties of shale samples, whilst clay minerals exert a moderate impact on them. • A novel hybrid stochastic modeling algorithm called DEM-QSGSA is proposed. • The effects of the components on electrical and elastic properties are investigated. • Pyrite has the highest impact on the electrical resistivity and elastic moduli. • The electrical and elastic properties are computed using the finite element method. [ABSTRACT FROM AUTHOR]

The hydraulic properties of reservoir rocks have a directly impact on the flow path of exchange fluid in geothermal and oil reservoir systems. Estimation of hydraulic properties by means of electrical measurement is convenient and nondestructive in these reservoir systems. The mechanism beneath which the pore structure affects electrical and hydraulic flow in porous media is not yet fully understood. In this study, we present a new permeability-formation factor relation based on pore-throat size model and fractal geometry theory. Furthermore, an updated model accounting for the effect of tortuosity and connectivity is applied to characterize the permeability of porous media. The experimental results show that the pore-throat ratio cannot fully describe the relationship between the permeability and the formation factor without considering tortuosity and connectivity. The combined model including pore-throat ratio, tortuosity and connectivity is further proposed to exactly estimate the influence of complex pore structure on the transport behavior associated with electrical parameters. The result also indicates that pore-throat ratio, tortuosity, and connectivity are the three key factors determining hydraulic properties in porous media. This means the estimation of electrical conductivity changes with permeability that depends on accurate characteristic of micro-structural properties of reservoir rocks. • A relationship between hydraulic property and electrical conductivity is proposed. • The pore-throat structure is variable based on fractal scaling in the model. • Prediction of the model matches the regular order of magnitude of permeability. • The tortuosity and connectivity influences on permeability are presented. [ABSTRACT FROM AUTHOR]

Estimating in situ gas content is very important for the effective exploration of shale gas reservoirs. However, it is difficult to choose the sensitive geological and geophysical parameters during the modeling process, since the controlling factors for the abundance of gas volumes are often unknown and hard to determine. Integrated interdisciplinary experiments (involving petrophysical, mineralogical, geochemical and petrological aspects) were conducted to search for the influential factors of the adsorbed gas volume in marine gas shale reservoirs. The results showed that in shale reservoirs with high maturity and high organic content that the adsorbed gas volume increases, with an increase in the contents of organic matter and quartz, but with a decrease in clay volume. The relationship between the adsorbed gas content and the total porosity is unclear, but a strong relationship between the proportions of different pores is observed. In general, the larger the percentage of micropores, the higher the adsorbed gas content. The result is illuminating, since it may help us to choose suitable parameters for the estimation of shale gas content. [ABSTRACT FROM AUTHOR]

The Bakken Formation is a typical tight oil reservoir and oil production formation in the world. Pore structure is one of the key factors that determine the accumulation and production of the hydrocarbon. In order to study the pore structures and main controlling factors of the Bakken Formation, 12 samples were selected from the Bakken Formation and conducted on a set of experiments including X-ray diffraction mineral analysis (XRD), total organic carbon (TOC), vitrinite reflectance (Ro), and low-temperature nitrogen adsorption experiments. Results showed that the average TOC and Ro of Upper and Lower Bakken shale is 10.72 wt% and 0.86%, respectively. The Bakken Formation develops micropores, mesopores, and macropores. However, the Upper and Lower Bakken shale are dominated by micropores, while the Middle Bakken tight reservoir is dominated by mesopores. The total pore volume and specific surface area of the Middle Bakken are significantly higher than those of the Upper and Lower Bakken, indicating that Middle Bakken is more conducive to the storage of oil and gas. Through analysis, the main controlling factors for the pore structure of the Upper and Lower Bakken shale are TOC and maturity, while those for Middle Bakken are clay and quartz contents. [ABSTRACT FROM AUTHOR]

Using the conventional fracture parameters is difficult to characterize and predict the complex natural fractures in the tight conglomerate reservoirs. In order to quantify the fracture behaviors, a fractal method was presented in this work. Firstly, the characteristics of fractures were depicted, then the fracture fractal dimensions were calculated using the box-counting method, and finally the geological significance of the fractal method was discussed. Three types of fractures were identified, including intra-gravel fractures, gravel edge fractures and trans-gravel fractures. The calculations show that the fracture fractal dimensions distribute between 1.20 and 1.50 with correlation coefficients being above 0.98. The fracture fractal dimension has exponential correlation with the fracture areal density, porosity and permeability and can therefore be used to quantify the fracture intensity. The apertures of micro-fractures are distributed between 10 μm and 100 μm, while the apertures of macro-fractures are distributed between 50 μm and 200 μm. The areal densities of fractures are distributed between 20.0 m·m−2 and 50.0 m·m−2, with an average of 31.42 m·m−2. The cumulative frequency distribution of both fracture apertures and areal densities follow power law distribution. The fracture parameters at different scales can be predicted by extrapolating these power law distributions. [ABSTRACT FROM AUTHOR]

Integration of Landsat images and multisource data using spatial statistical analysis and geographical detector models can reveal the individual and interactive influences of anthropogenic activities and ecological factors on concentrations of atmospheric particulate matter less than 2.5 microns in diameter (PM2.5). This approach has been used in many studies to estimate biomass and forest disturbance patterns and to monitor carbon sinks. However, the approach has rarely been used to comprehensively analyze the individual and interactive influences of anthropogenic factors (e.g., population density, impervious surface percentage) and ecological factors (e.g., canopy density, stand age, and elevation) on PM2.5 concentrations. To do this, we used Landsat-8 images and meteorological data to retrieve quantitative data on the concentrations of particulates (PM2.5), then integrated a forest management planning inventory (FMPI), population density distribution data, meteorological data, and topographic data in a Geographic Information System database, and applied a spatial statistical analysis model to identify aggregated areas (hot spots and cold spots) of particulates in the urban area of Jinjiang city, China. A geographical detector model was used to analyze the individual and interactive influences of anthropogenic and ecological factors on PM2.5 concentrations. We found that particulate concentration hot spots are mainly distributed in urban centers and suburbs, while cold spots are mainly distributed in the suburbs and exurban region. Elevation was the dominant individual factor affecting PM2.5 concentrations, followed by dominant tree species and meteorological factors. A combination of human activities (e.g., population density, impervious surface percentage) and multiple ecological factors caused the dominant interactive effects, resulting in increased PM2.5 concentrations. Our study suggests that human activities and multiple ecological factors effect PM2.5 concentrations both individually and interactively. We conclude that in order to reveal the direct and indirect effects of human activities and multiple factors on PM2.5 concentrations in urban forests, quantification of fusion satellite data and spatial statistical methods should be conducted in urban areas. [ABSTRACT FROM AUTHOR]