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Western Hunan province and its surrounding areas are significant targets for shale gas exploration and development in southern China, where the black shale of the lower Cambrian Niutitang Formation and Wunitang Formation is extensively distributed. Geochemical analysis was conducted on the lower Cambrian black shale from a new exploration well of XAD1 located at the southeast margin of the Yangtze paraplatform, followed by a discussion on gas-bearing properties using molecular dynamics simulation. The geochemical characteristics indicate that the black shale in well XAD1 was primarily deposited in a strongly reducing marine environment, with organic matter predominantly composed of type I kerogen derived from algae. Currently, it has reached a stage of high to over maturity with limited potential for liquid hydrocarbon generation. The recovery of the original hydrocarbon generation potential shows that they are excellent source rocks and have completed the main hydrocarbon generation evolution. Despite the favorable conditions for shale gas formation observed in well XAD1, the low measured gas content within the Niutitang Formation suggests that other geological factors may have contributed to a substantial loss of shale gas. Gas adsorption simulation reveals that the maximum methane adsorption capacity (15.77 m3/t) was achieved by Niutitang shale during the late Silurian period when there was an abundant source of natural gas without any influence from CO2, H2O or other molecules. However, due to a lack of natural gas replenishment and subsequent tectonic uplift and subsidence causing variations in temperature and pressure, the methane adsorption capacity gradually decreased (to 6.56 m3/t). Furthermore, water occurrence within the shale reservoir further reduced the methane adsorption capacity (below 2 m3/t), while tectonic activities exacerbated the loss of shale gas potential within this study area. The findings indicate that the dynamic alteration of gas-bearing properties in shale reservoirs due to tectonic movements is a crucial factor influencing the success rate of shale gas exploration in the study area, provided that there are sufficient gas resources and superior reservoir conditions. [ABSTRACT FROM AUTHOR]

Craniomaxillofacial disease, which is common all over the world, is difficult to screen at early stage. It will probably affect the patient' facial appearance once someone suffers from it. This paper introduces an integrated system that is composed of data collection, three-dimensional reconstruction, and disease screening, facilitating timely detection of craniomaxillofacial diseases. With an expanding number of data, the system will steadily improve the accuracy of disease screening, step by step, enabling patients to conventionally recognize craniomaxillofacial diseases with greater ease and accuracy. • We propose a method for early screening of craniofacial diseases through video. • More accurate estimation of craniofacial diseases through a combination of dynamic and static features. • This study is expected to enhance the public's understanding of the necessity of craniofacial tumors, in order to promote early diagnosis and improve the overall prognosis of patients. [ABSTRACT FROM AUTHOR]

Diagenesis is one of the most predominant factors controlling reservoir quality in the deeply buried siliciclastic sandstones of the third member in the Eocene Shahejie Formation (Es3), in the Raoyang Sag, the Bohai Bay Basin. In this study, thin section, cathodoluminescence (CL), scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectrum, carbon and oxygen isotopes, and fluid inclusion analyses are used to restructure paragenetic sequences and detect origins of carbonate cements recorded in this deeply buried member. Based on petrographic analyses, the Es3 sandstones are identified as lithic arkoses and feldspathic litharenites at present, but derived from original arkoses and lithic arkoses, respectively. Geohistorically, the Es3 sandstones have undergone two diagenetic episodes of eogenesis and mesogenesis. Events observed during eogenesis include chemical compaction, leaching of feldspar, development of chlorite coating and kaolinite, precipitation of the first generation of quartz overgrowth (QogI), dissolution of feldspar, and precipitation of calcite and nonferroan dolomite cement. Mesogenetic alterations include chemical compaction, precipitation of kaolinite aggregate and the second generation of quartz overgrowth (QogII), precipitation of ankerite, development of I/S and illite, and formation of pyrite. Carbon and oxygen isotopic data show that calcite cements are characterized by 13C ( δ 13 C PDB ranging from -0.7‰ to 1.0‰ with an average of 0.1‰) and 18O ( δ 18 O SMOW varying from 12.3‰ to 19.0‰ with an average of 16.2‰); these stable isotopic data combined with Z value (from 114.69 to 122.18) indicate skeletal debris ( δ 13 C PDB ranging from -1.2‰ to -1.1‰ with an average of -1.15‰; δ 18 O SMOW varying from 23.0‰ to 23.2‰ with an average of 23.1‰) and ooids in adjacent carbonate beds involved in meteoric water and seawater from outside jointly served as the carbon sources. For nonferroan dolomite, the δ 13 C PDB value of -4.1‰ is a little bit negative than the calcite, and the δ 18 O SMOW of 14.3‰ is coincident with the calcite, which suggest the nonferroan dolomites come from the diagenetic fluids with a similar oxygen isotopic composition to that of the calcite but modified by the external acidic δ 13C-depleted water. However, the ankerites are actually rich in 12C ( δ 13 C PDB ranging from -10.0‰ to -1.2‰, mean = − 4.3 ‰) and 16O ( δ 18 O SMOW varying from 10.1‰ to 19.4‰, mean = 14.9 ‰), when combined with the distribution of cutting down along the direction pointing to sand-body center from the margin and microthermometric temperature (Th's) data mainly varying between 115.2°C and 135.5°C with an average of 96.0°C, indicating the main origination from the Es3 source rocks with effective feldspar buffer action for the acidic fluids in the margins of the Es3 sandstones. In addition, the necessary elements for ankerite such as Fe2+, Ca2+, and Mg2+ ions also come from organic matter and clay minerals during thermal maturation of the Es3 source rocks. The study provides insights into diagenetic processes and origination of carbonate cements in the Es3 sandstones; it will facilitate the cognition of predictive models of deeply buried sandstone reservoirs to some extent, which can reduce the risks involved in oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

Deeply buried (3.5–4.5 km) fan deltaic and braided deltaic sandstones of the Eocene Shahejie Formation are important hydrocarbon reservoirs in the Raoyang Sag of the Bohai Bay Basin (North China). An integrated approach incorporating petrophysics, thin‐section petrography, scanning electron microscope (SEM), cathodoluminescence (CL), and well log analysis was applied to investigate diagenesis, diagenetic minerals, and their impacts on reservoir quality. The sandstones of the Sha‐3 (the third Member of the Shahejie Formation) are dominated by lithic arkoses and arkoses with a low‐moderate compositional maturity and a moderate textural maturity. The pore systems are dominated by secondary pores resulting from dissolution of framework grains, micropores among authigenic clays, and minor amounts of primary intergranular pores. Chemically unstable framework grains such as feldspar and lithic fragments experienced alteration and resulted in formation of authigenic kaolinite. Dissolution and alteration of feldspars and rock fragments and pressure solution of detrital quartz grains were the main sources for quartz cements. Mechanical compaction and cementation by calcite, dolomite, quartz, kaolinite, and mixed‐layer illite/smectite destroyed primary pores, whereas dissolution of framework grains generated secondary pores. Five types of diagenetic facies are identified based on framework mineralogy, texture, diagenetic minerals, and pore systems. These comprise the following: (a) quartz‐cemented sandstone, (b) tightly compacted sandstone, (c) carbonate‐cemented sandstone, (d) clay‐mineral‐cemented sandstone, and (e) clean dissolved sandstone. Diagenetic processes and evolution sequences for the five diagenetic facies were reconstructed based on textural relationships from thin section, SEM, and CL studies. The reservoir quality evolution of various diagenetic facies is predicted by considering variations in grain size, sorting, shape, and matrix content of sandstones. This work, which investigates the diagenetic sequence of sandstones, will provide insights into reservoir quality prediction for low‐permeability sandstones with similar tectono‐depositional settings. [ABSTRACT FROM AUTHOR]

Relict plants, remnants of Tertiary flora, survived geochronological ages, however, studies intended to ascertain the background of their fungal symbionts are limited. Different from many other relict plants, Gymnocarpos przewalskii Maxim. inhabits arid deserts region, mainly distributed in northwest China. In order to inquire the arbuscular mycorrhizal fungi (AMF) associated to G. przewalskii and their ecological significance in desert ecosystems, the seasonal dynamics of AMF and glomalin were surveyed in Anxi and Minqin in Gansu Province, northwest China. Soil samples in the rhizosphere of G. przewalskii were collected in July, September and December 2019, respectively. In total, 41 and 46 AMF species were identified via morphological techniques in Anxi and Minqin, respectively. Meanwhile, high throughput sequencing (HTS) data diagnosed 29 and 61 AMF OTUs in Anxi and Minqin, respectively. Glomus was the dominant genus in different seasons and locations in both morphological investigation and HTS data. AMF colonization (44.67–75.30%) and spore densities (19–248 per 20 g soil) varied sharply among seasons and locations. AMF colonization and spore densities showed significant positive correlations to most edaphic factors, except soil carbon: nitrogen ratio. Glomalin-related soil protein (GRSP) dramatically contributed to local soil carbon pool (51.54% in Anxi, 40.37% in Minqin), and the GRSP contents in soil were significantly affected by soil properties, season, and location. Random forest analysis indicated that soil humidity and total GRSP were the main factors shaping AMF communities. Our results showed that AMF colonization, spore density, and species diversity were higher and AMF community composition was less variable in Minqin where the soil nutrition levels were lower, which emphasized the necessity of AMF symbiosis for plants in harsh environments. The present research demonstrated the seasonal dynamics of soil AMF communities and glomalin and determined influential environmental factors in desert ecosystems. Our findings provide novel views on desert soil resource management and relict plant protection from an aspect of plant-AMF symbiosis. • Gymnocarpos przewalskii is a typical relict plant in the desert region of northwest China. • The colonization and structure of AMF have obvious seasonal and location heterogeneity. • Glomus spp. dominated AMF communities in desert soil across all seasons. • Glomalin might be useful indicators for evaluating soil quality and desertification. • Seasonal and location changes drive specific soil properties affected AMF community. [ABSTRACT FROM AUTHOR]

A comprehensive study of the lithology, mineralogy, major element and trace element geochemistry of the organic-rich shales in the Lower-Middle Cambrian Niutitang and Wunitang Formations in South China was performed to assess the depositional environments and the mechanisms for organic matter enrichment. Results show that the Lower Cambrian Niutitang shales were mainly deposited under anoxic conditions with high paleo-productivity, while the overlying Wunitang shales were deposited under dysoxic conditions with lower paleo-productivity. Both these shales were deposited in a moderately restricted deep-water basin. This paleogeographic setting was conducive to limited water interchange between the outer shelf and open ocean, resulting in a high flux of nutrients from shelf upwelling. These nutrients were produced from upwelling and hydrothermal vents and were carried by oceanic currents, enhancing blooms of primary producers within the surface waters. Organic matter enrichment of the Niutitang and Wunitang shales was mainly controlled by redox conditions and paleo-productivity. The intermittent renewal of connections to open ocean water during sea level rise weakened the restricted conditions in the depositional area, which significantly accelerated the consumption of organic matter. • Productivity was promoted by nutrient from hydrothermal activities in Niutitang Formation. • Moderately restricted deep-water continental shelf environment benefits the anoxic environment. • Synergistic processes of redox condition and sea surface productivity controlled organic-rich shale development. [ABSTRACT FROM AUTHOR]

Fractal geometry provides an effective method for characterization of the complex and irregular pore structure of Eocene Shahejie low permeability sandstones in the Raoyang Sag, the Bohai Bay Basin, China. Laboratory measurements including porosity, permeability, scanning electron microscope (SEM), thin sections, nuclear magnetic resonance measurements (NMR) and X-ray computed tomography (CT) technology are used to provide insights into the fractal characteristics of pore structure in sandstones of Eocene Shahejie Formation in the Bohai Bay Basin, China. Quantitative CT analysis reveals the pore radius is not always linear to T 2 (transverse relaxation time) value obtained from the NMR tests, but instead power function of T 2. Fractal analysis was performed on the T 2 distribution using various fractal models, and the related fractal dimensions are calculated. The fractal dimensions calculated using various fractal models are correlated with NMR parameters and permeability. The fractal curves break into two segments at the T 2cutoff (T 2 separating the immovable and movable fluids) value or smaller when using fractal model Ⅰ and fractal model Ⅱ, and only the large-scale pore networks can be described by the fractal geometry. Mostly the entire pore size distributions (micro-pores to large-scale pore networks) can be described by the fractal model Ⅲ, and the calculated fractal dimensions are in accordance with the CT scanning and thin section data, and are strongly correlated with the T 2gm (geometric mean of T 2), permeability and BVI (bulk volume of immovable fluids). The fractal behaviors of pore size distributions from NMR analysis have implications for pore structure evaluation in low permeability sandstones with similar geological settings. • Fractal analysis was performed on the NMR T 2 spectrum. • Fractal dimensions are calculated using various fractal models. • Fractal dimensions are related with the NMR parameter and permeability. [ABSTRACT FROM AUTHOR]

Unconventional tight oil reservoirs have recently emerged as a significant source of oil worldwide, and juxtaposed to organic‐rich source rocks, tight mixed siliciclastic–carbonate sedimentary reservoirs are widely found. In China, such reservoirs are mainly found in saline lacustrine basins. In this paper, we conduct a systematic study on advantageous source–reservoir combinations (SRCs) in the Cretaceous Xiagou Formation in the Qingxi Sag of the Jiuquan Basin, a tight saline lacustrine and mixed siliciclastic–carbonate sedimentary oil reservoir. Mixed sediments result in multiple SRCs as follows: self‐contained SRC, thick interbedded‐type SRC, thin interbedded‐type SRC, and down generated‐up stored SRC. Geochemical characteristics of organic matter in the Cretaceous Xiagou Formation are established on the basis of Rock‐Eval pyrolysis and total organic carbon (TOC) and vitrinite reflectance analyses. TOC (0.5–4.12%, av. 1.62%) and S2 (0.36–26.63 mg/g, av. 5.62 mg/g) indicate a good hydrocarbon generative potential. The organic matters contain predominantly Type II kerogen with minor contributions from Type I kerogen. The samples analysed have vitrinite reflectance in the range of 0.65–1.0%Ro, and pyrolysis Tmax in the range of 430–450 °C indicate that the source rocks are early mature to mature and within the main stage of oil generation. The tight oil resources are divided into 4 classifications according to TOC versus S1 diagram, and dolomitic mudstone in lower K1g3 and K1g1 is primarily considered to be potentially generative and productive. Reservoir characterization such as porosity, permeability, and pore‐size distribution derived from nuclear magnetic resonance indicates that nano‐meter‐sized pores dominate pore size distribution, regardless of the lithology. Fractures contribute to the creation of relatively higher productivity reservoirs. The statistics of oil testing results shows that the daily oil productions increased basically from the down generated‐up stored SRCs to thin interbedded‐type SRCs to thick interbedded‐type SRCs to self‐contained SRCs. The movable oil saturations derived from nuclear magnetic resonance have the same changes as daily oil production. The self‐contained SRCs and the thick interbedded‐type SRCs are identified as advantageous SRCs that are important for tight oil prediction. [ABSTRACT FROM AUTHOR]

The development characteristics of organic matter pores (OMPs) in shales is fundamental to the gas-bearing property of the shales. Detachment is one of the most common types of structural deformation in shale formations. To investigate the characteristics of OMPs in shear-deformed shale and the associated effects on the pore structure of shale gas reservoir, two sets of detachment zones and the intercalated non-detachment zone of shale formations in the Niutitang Formation of the Well XAD1 are studied. Based on scanning electron microscope observations and low-pressure gas adsorption tests, the impacts of shear on the shale pore structure are evaluated quantitively and the deformation mechanism for OMPs in shale is established. Results indicate that the dominant pore type of shale in the Niutitang Formation of the Well XAD1 is OMPs. With the mineral rheology, organic matters are enriched in the clay gouge, which are more prone to shear deformation compared with those outside the gouge. Under shear, pores developed within the organic matter experienced directional elongation and compression, decreasing the pore sizes and lowering the volumes of the corresponding pores <30 nm; and the contact surface between organic matter and minerals becomes dislocated and open, increasing the volumes of the corresponding pores >30 nm. The effect of shear on OMPs is dominated by pore reduction. The volume loss ratio of shale micropores in detachment zones is the highest which can reach over 90%. The impact of shear on pore structures of non-detachment zone cannot be neglected within the thickness range of 5–20 m from the detachment surface, and the degree of pore reduction gradually decreases as the distance from the detachment zones increases. It is indicated that the detachment and its adjacent horizons are not favorable for shale gas exploration because of the low porosity and adsorption capacity. • The deformation of organic matter pore is controlled by the micron-wide clay gouge in the shale matrix. • Shear deformation can result in a significant reduction of pore volume, especially for organic matter pores <30 nm. • The impact of shear on pore structures of non-detachment zone cannot be neglected. • The competency of shale formations and their distance from detachment zones can affect the pore deformation degree. [ABSTRACT FROM AUTHOR]

Endophytic fungi isolated from plants under drought stress have been evidenced to confer hosts adaptive benefits to withstand drought. In this study, endophytic fungi associated with five typical desert shrubs in different tissue from extremely arid desert in Northwest China were investigated based on ITS sequence analysis. A total of 158 endophytic fungal stains were isolated from 1088 tissue segments of 12 samples, and 28 taxa represented by 25 species and 15 genera were identified as Ascomycetes. Alternaria sp. was the dominant genus with generic abundance ranging from 20% to 65%. The colonization rate of root was significantly lower, but the root-endophytic fungi (19 species) conversely presented a higher diversity than stem and leaf (11 and 7 species, respectively). Endophytic fungi had pronounced relative host and tissue preferences, while tissue explained more endophytic fungal variation than plant species. Additionally, soil pH, organic carbon, and phosphatase elicited significant responses from fungal species, which significantly affected the species richness of Fusarium redolens, Alternaria chlamydospore, Didymella glomerata, and Xylariales sp. This research provides a basis for the further understanding of the ecological distribution of endophytic fungi associated with xerophytic plants and their potential application for vegetative restoration and agricultural cultivation in drylands. [ABSTRACT FROM AUTHOR]

Marine shales in southern China experiences multiple complex tectonic movements, which highly affects shale pore characteristics and pore evolution. The effects of tectonic deformation on nanopore structure and petrophysical properties of organic shales remain unclear. Three ductile deformed shale samples were collected and analyzed through an integrated experiment procedure for a comparative research against undeformed shale samples. Field emission-Scanning electron microscopy (FE-SEM), low pressure N 2 and CO 2 adsorption and mercury injection porosimetry (MIP) analyses were performed to characterize pore structure of the shales. The results reveal that the mineral compositions of these shale samples are controlled by sedimentary environment and source and exhibits no obvious relationship with tectonic deformation. With increasing deformation degree, the micropore proportion gradually decreases (from 17% to 6%), and the macropore proportion increases from 16% to more than 20%. Micropore volumes and proportion in the fold core samples are the smallest (4.2 × 10−3 cm3/g and 6.3%) and account for only one-third of the undeformed shale values, while the meso- and macropore values are larger-1.2 times those of the undeformed shale values. The evolution characteristics and deformation modes of organic matter (OM), interparticle (interP) and intraparticle (intraP) pores and microfractures under ductile deformation were examined. All pore types become interconnected during deformation and form microfractures ranging from a few nanometers to tens of microns, which is the main reason for the enhanced shale connectivity caused by deformation. Under the same porosity conditions, the deformed shale permeability is much higher than the undeformed shale permeability, and stronger deformation corresponds to higher permeability. The fold core permeability is generally higher than the limb permeability and exceeds 30 times. The different ductile deformation positions were divided into five levels, and the corresponding reservoir quality was evaluated. This study is of great significance to better understand the pore structure evolution process for shale exploration and development under tectonic deformation. • Pore structure deformation develops widely during tectonic deformation. • Ductile deformation significantly affects the micro- and macropores of shale. • The fold core permeability is generally much higher than the limb permeability. • The pore interconnected during deformation promotes the development of microfractures and increases the permeability. [ABSTRACT FROM AUTHOR]

The article presents a study which discusses recent advances and prospects of mixed siliciclastic-carbonate sediments (S-MSCSs) in China. Topics discussed include (S-MSCSs) as indicator of sea-level history and varying sedimentation, effects of facies dynamics and changes in relative sea-level, and penecontemporaneous metasomatic dolomite as tight-oil reservoir in China.