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A case study on the internal pressure induced by a local failure on the vulnerable gable roof of a low-rise building was extensively conducted experimentally and numerically. Five roof opening configurations were tested in the wind tunnel under three different boundary layer conditions, based on 1:40 scaled models. The effects of opening shape, opening position, opening ratio, building internal volume, and wind speed on peak transient and steady-state internal pressures were studied. The study results indicate that the peak transient and steady-state internal pressures and the corresponding transient overshoot ratio all increase with an increasing opening ratio. The peak steady-state internal pressure is little affected by the approaching wind speed; while the peak transient internal pressure coefficient shows a significant linear relationship with the wind speed. The coupling effect of vortex shedding and Helmholtz resonance in double building volume compensation situation may cause larger fluctuating internal pressure. Both the vortex shedding and Helmholtz resonance reduce the internal pressure coherence to some extent. The agreement between the numerical and experimental results is much better for the mean internal pressure than that for fluctuating internal pressure or peak internal pressure.

A novel oxygen reduction reaction (ORR) electrocatalyst silver@platinum-cobalt-rGO nanoflower (Ag@PtCo-rGO NFs) is prepared by hydrothermal reduction method. The formation of silver chloride likes elm leaf microstructure in the reaction process, performing as a template. The Ag@PtCo-rGO NFs exhibit excellent electrocatalytic activity, whose specific activity is 9 times higher than that of commercial Pt/C. More importantly, Ag@PtCo-rGO NFs demonstrate excellent durability than JM Pt/C for ORR in acid media, as evidenced by accelerated durability test after 40,000 cycles. These excellent performances can be attributed to the special structure, atomic steps and synergistic effect between Pt, Ag and Co. The density functional theory calculation shows that Ag@PtCo has the best activity, which is related to the transition state for O–O bond. This work proposes a promising pathway for the synthesis of surfactant-free nanoflowers structure catalysts with high catalytic performance and low cost.

Sugarcane smut, caused by Sporisorium scitamineum, is one of the most devastating fungal diseases affecting sugarcane worldwide. To develop a potent sugarcane smut fungicide, secondary metabolites of marine-derived Bacillus siamensis were isolated and screened for inhibitory activities, which led to the discovery of five new 24-membered macrolactins, bamemacrolactins A-E (1-5), with 3 being the most potent inhibitor. The antifungal mechanism of 3 was studied by assessing its effects on mycelial morphology and the cell wall. Differential proteomics were used to analyze proteins in S. scitamineum upon treatment with bamemacrolactin C and to elucidate its antifungal mechanism. A total of 533 differentially expressed proteins were found. After the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses, eight target proteins were selected, and their functions were discussed. Six of the eight proteins were reported as antifungal targets. The target proteins are involved in the oxidative phosphorylation pathway. Therefore, the potent inhibition of S. scitamineum by compound 3 is most likely through oxidative phosphorylation and targeting a series of enzymes.

A new Lewis acid-catalyzed [2 + 2] cycloaddition/retroelectrocyclization (CA-RE)/1,6-addition relay of aurone-derived 1-azadienes and 1-alkynylnaphthalen-2-ols has been reported, leading to the regio- and diastereoselective synthesis of 1,2-dihydrobenzofuro[3,2-b]pyridine with a chiral carbon center and an axial chirality in good yields. This protocol enables the C-C double-bond scission/recombination to rapidly construct aza-heterocyclic architectures and features 100% atom utilization, a wide substrate scope, good compatibility with substituents, and excellent diastereoselectivity.

Tunable electrocatalytic annulation reactions of o-arylalkynylanilines have been established, leading to green and divergent syntheses of skeletally diverse indoles by adjusting the electrolytes and the solvents. The presence of ammonium halides as the electrolytes enabled the halogenation of o-arylalkynylanilines to give C3-halogenated indoles whereas naphtho[1',2':4,5]furo[3,2-b]indoles could be obtained by changing the electrolyte from ammonium halides to KI. Interestingly, by combining acetone as the solvent and both NH4I and NH4Cl as the electrolytes, the reaction worked through an intramolecular annulation and [5 + 1] cyclization cascade to form naphtho[1',2':5,6][1,3]oxazino[3,4-a]indoles.

Simplified Molecular Input Line Entry System (SMILES) provides a text-based encoding method to describe the structure of chemical species and formulize general chemical reactions. Considering that chemical reactions have been represented in a language form, we present a symbol only model to generally predict the yield of organic synthesis reaction without considering complex quantum physical modeling or chemistry knowledge. Our model is the first deep neural network application that treats chemical reaction text segments as embedding representation to the most recent deep natural language processing. Experimental results show our model can effectively predict chemical reactions, which achieves a high accuracy of 99.76% on practicality judgment and the Root Mean Square Error (RMSE) is around 0.2 for yield prediction. Our work shows the great potential for automatic yield prediction for organic reactions under general conditions and further applications in synthesis path prediction with the least modeling cost.

A new copper/silver-co-mediated three-component bicyclization of benzene-linked 1,6-enynes with ICF2CO2Et with TMSN3 was reported, and used to produce a wide range of hitherto unreported difluorinated tetrahydroindeno[1,2-c]azepine-3,6-diones with moderate to good yields. The mechanistic pathway consists of radical-induced 1,6-addition–cyclization, oxidative addition, reductive elimination, nitrene insertion and N–O cleavage, resulting in continuous multiple bond-forming events including C–C and C–N bonds to build up a 6/5/7 tricyclic framework.

Two classes of new catalytic spiroannulation-fluormethylfunctionaliztions of para-quinone methide (p-QM)-containing 1,5-enynes have been established under redox-neutral conditions. Palladium-catalyzed spiroannulation-iododifluoromethylation with ethyl difluoroiodoacetate oriented completely stereoselective access to (Z)-spiroindenes and the latter included copper-catalyzed three-component spiroannulation-cyanotrifluoromethylation starting from Togni's reagent and trimethylsilanecarbonitrile (TMSCN). Both reaction pathways involve fluoroalkyl radical-triggered 1,6-addition/5-exo-dig annulation/metal radical cross-coupling/reductive elimination sequence, providing practical and stereoselective protocols for rapidly constructing cyclohexadienone-containing spiroindenes with generally good yields.

Tight sandstone gas reservoirs have poorer porosity–permeability relationships, so conventional reservoir classification schemes can hardly satisfy the classification and evaluation demand of this type of reservoirs. To solve this problem, this paper took the Permian tight sandstone gas reservoir in the Linxing Block along the eastern margin of the Ordos Basin as an example to describe the micro-structures of the tight sandstone reservoirs by means of high-pressure mercury injection, nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and so on. Then, the control effect of micro-structure parameters on the macrophysical properties was studied. Finally, classification and evaluation of tight sandstone reservoirs were carried out on this basis. And the following research results were obtained. First, NMR can identify the distribution of pores of different sizes, and high-pressure mercury injection can reflect the pore–throat configuration and percolation capacity of a reservoir. Second, both methods are better coincident in the description results. With an increase of the right peak of T2 spectra, the mercury intrusion curve presents a concave shape and the pore throat radius increases while the pore type gradually changes from intragranular dissolution pores and intercrystalline pores to intergranular pores and intergranular dissolution pores and the reservoir quality gets better. Third, micro-pore structure controls reservoir physical properties and fluid mobility. And the porosity of large pores is best correlated with the effective porosity, so it can be used to evaluate the reservoir capacity of tight sandstone. Fourth, the throat radius R15 obtained by high pressure mercury injection is in the best correlation with porosity and permeability, so it can be used to evaluate the percolation capacity of tight sandstone. Fifth, by combining the porosity of large pores with the R15, the tight sandstone reservoirs in the Linxing Block are classified into 4 categories, and the classification results are in a good agreement with the on-site well test data. It is concluded that the combination of high-pressure mercury injection and NMR can effectively identify the key parameters which reflect the reservoir capacity and percolation capacity of tight sandstone, and improve the reliability and integrity of reservoir classification. And by selecting the key parameters that reflect reservoir capacity and percolation capacity, it can provide guidance for the classification and evaluation of tight sandstone reservoirs.

This paper systematically investigates and compares the petroleum geology elements and oil and gas exploration potential in the deep-water basins along the conjugate passive margins between Morocco in NW Africa and Nova Scotia in Canada. Both the deep-water basins along the passive margin in Morocco and its conjugate passive margin deep-water basin in Nova Scotia have undergone similar multiple stages of tectonic evolution. These conjugate basins both have Jurassic and Cretaceous source rocks; Triassic sandstone, Jurassic-Cretaceous carbonate and sandstone, and Miocene-Pliocene sandstone reservoirs; multiple sets of mudstones and regional Triassic salt as caprocks. These characteristics indicate good hydrocarbon accumulation conditions and exploration prospects. The comparison also reveals that the key exploration targets in the deep-water basins of Morocco should be Tertiary turbidite sandstone reservoirs and Jurassic-Cretaceous sandstone and carbonate reservoirs. Compared with the Scotian Basin, the Morocco deep-water basins may have Paleozoic play potential sourced from the mature Silurian hot shale source rock that extends from the onshore NW African Plate. The prospective exploration targets in the deep-water Scotian Basin should be focused on the Jurassic and Cretaceous deep-water turbidite sandstone reservoirs formed by widely-developed large river systems.

Deep lithospheric processes associated with the formation of major orogens, including the removal of lower crust and underlying mantle through delamination associated with orogen building are poorly constrained. With a view to evaluate the potential link between deep geodynamic processes and magmatic events, we performed in situ zircon Hf-O-Li isotopic analyses of granitoids from the Eastern and Western Junggar, Altai and Beishan orogens, within the Central Asian Orogenic Belt (CAOB). The eHf(t) and δ18O values of magmatic zircons crystallized during 443 Ma and 252 Ma indicate diverse and heterogeneous magma sources. The corresponding δ7Li peaks at ~440 Ma and ~250 Ma, suggesting two distinct high-temperature magmatic events. Based on a comparison with global data, we argue that large-scale delamination formed through Gondwana and Pangaea supercontinent assembly, may have occurred at Ordovician to Silurian boundary (OSB) and Permian to Triassic boundary (PTB), which we term as super-delamination. The subsequent widespread magmatism and volcanism might have made significant impact on the Earth surface ecosystems, ultimately leading to the OSB and PTB mass extinction events. We propose super-delamination as a potential mechanism to explain the link between Earth's internal and external processes, thus providing novel insights into the trigger for mass extinction events.

The pore–throat systems and physical properties of tight sandstone reservoirs are complex, and deposition is thought to be a fundamental control for them. In this study, the impacts of the full ranges of rock types (from pebbly coarse sandstone to fine sandstone) on the pore structures and physical properties of the Permian tight sandstone reservoir in the eastern Ordos Basin were investigated comprehensively through a series of experiments including conventional physical testing, thin-section analysis, scanning electron microscopy, nuclear magnetic resonance analysis and high-pressure mercury injection tests. The results showed that the coarser-grained sandstones tend to have higher feldspar content and lower percentage of cements, leading to strong dissolution, weak cementation and improved porosity and permeability. The medium sandstone has the highest level of quartz and the lowest average content of feldspar, resulting in strong heterogeneity of physical properties. Only those medium sandstone reservoirs with relatively high content of feldspars have better physical properties. Additionally, the coarser-grained sandstones contain relatively large dissolution pores (nearly 200 μm), whereas the finer-grained sandstones have more intercrystalline pores with a relatively more homogeneous pore structure. The pebbly coarse sandstone and coarse sandstone reservoirs are favorable targets with best physical properties.

A new electrochemical three-component annulation-iodosulfonylation of 1,5-enyne-containing para-quinone methides (p-QMs) has been established by using available arylsulfonyl hydrazides and potassium iodide under environmentally benign conditions. The electrosynthesis offers sustainable and efficient access to construct spirocyclohexadienone-containing (E)-indenes without any additional catalyst or oxidant through a sulfonyl-radical-triggered 1,6-addition and an I+-mediated ipso-cyclization cascade. Notably, potassium iodide plays the triple role of an electrolyte, a redox catalyst, as well as an iodination reagent.

The Solonker Belt is an important tectonic unit of the Central Asian Orogenic Belt in Inner Mongolia, China and the sediments in the Solonker Belt record the paleogeographic evolution of the Paleo-Asian Ocean. This study characterizes the spatial distribution of the lithofacies and lithofacies associations, and environment variations in the Mandula Basin. The Upper Carboniferous to Lower Permian Amushan Formation shows typical features of slump deposits occurred in the lower slope environments. The Lower to Middle Permian Baotege Formation develops the channelized lobes, channel–levee–overbank, and hemipelagic/pelagic deposits that are formed in the base of slope to basin floor environments. The Lower to Middle Permian Dashizhai Formation represents volcanic edifice and volcaniclastic aprons in the basin floor. The Middle Permian Zhesi Formation includes the shallow water reefs, deep-water biogenetic limestones, and volcaniclastic aprons developed in the abyssal slopes of the volcanic edifice. The sedimentary facies in the Mandula Basin constitute two depositional systems: the continental slopes adjacent to marginal carbonate platform and the volcaniclastic aprons associated with volcanic edifice in the basin floor. The Mandula Basin is an extensional deep-water basin and akin to the marginal sea of an ocean.

Organic matter enrichment in shale is one of the key factors that control shale oil resources; however, studies of the mechanism of organic matter enrichment in shale in saline lacustrine rift basins are still lacking. In this study, analyses of total organic content (TOC), stable isotopes of carbon and oxygen for carbonate, major and trace element, rare earth element, biomarker composition, and field emission-scanning electron microscopy analyses were performed on 31 core samples from the source rocks of the middle interval of the third member of the Shahejie Formation (Es3M ). The aims of these analyses were (1) to investigate the controlling effects of paleoenvironment, paleosalinity, redox conditions, dilution, sediment accumulation rate, terrestrial input, and paleoproductivity on organic matter enrichment, (2) to reconstruct the paleoenvironment, and (3) to propose a model of differential accumulation mechanism for organic matter in saline lacustrine source rocks in rift basins. Results show that obvious differences exist in the paleoenvironment of the Es3M between the southern and northern regions in the Dongpu Depression. The TOC of the northern source rocks is generally greater than that of the southern source rocks. The southern source rocks were mainly deposited in a closed, warm, and humid environment with medium chemical weathering [the chemical index of alteration (CIA) values and Mg/Ca ratios range from 57.9 to 75.8 and 0.08 to 0.61, with averages of 70.93 and 0.19], with fresh–brackish water, weak water stratification, reducing conditions, moderate paleoproductivity (the P/Ti and P/Al ratios range from 0.13 × 10−4 to 0.26 × 10−4 (mean 0.18 × 10−4) and 5.11 × 10−3 to 11.31 × 10−3 (mean 7.62 × 10−3), respectively). The northern source rocks were mainly deposited in an open, cold, and arid environment with a weak chemical weathering (CIA values and Mg/Ca ratios range from 57.9 to 75.8 and 0.08 to 0.61, with averages of 70.93 and 0.19), with hypersaline water, strong water stratification, strong reducing condition, moderate paleoproductivity [P/Ti and P/Al ratios range from 0.13 × 10−4 to 0.26 × 10−4 (mean 0.18 × 10−4) and 5.11 × 10−3 to 11.31 × 10−3 (mean 7.62 × 10−3)]. The paleosalinity, redox condition, paleoproductivity, and terrestrial input controlled the differential enrichment of organic matter in saline lacustrine source rocks. For the southern region, organic matter enrichment increased with increasing paleosalinity, reduction degree, and terrestrial input. Organic matter enrichment of the northern source rocks increased with increasing paleoproductivity, which was mainly due to high water salinity, stable deep paleowater depth, and strong reducing condition.

Efficient oxygen reduction reaction (ORR) electrocatalysts are critical for fuel cells. Herein, we report a facile synthetic method to prepare Co–N–C porous nanofibers (Co–N-CNFs) for high performance ORR electrocatalyst. Specifically, Polyacrylonitrile/Bimetallic (Cobalt and Zinc) ZIFs (PAN@BZIFs) hybrid is obtained by electrospinning and finally resulting in Co, N doped carbon nanofibers after pyrolysis. Electrochemical measurements demonstrate that it possesses remarkable ORR performance, superior stability and methanol tolerance under alkaline condition compared to commercial Pt/C catalyst. In this Co–N–C system, the ratio of Co/Zn in BZIFs and temperature of pyrolysis are confirmed as the important factors of specific surface area, graphitization and even ORR property. Thereby, through changing them, the best electrocatalytic activity was acquired with the ratio equals to 0.2 and pyrolyzing at 800 ℃. In addition, the excellent catalytic property can be attributed to the synergic coupling pores and hierarchical pore structure.

To better implement super critical carbon dioxide (SC-CO2) fracturing on shale, it is important to investigate effects of SC-CO2 on rock mechanical properties. Because micro-scale mechanical properties determine the overall mechanical response, the determination of micro-scale mechanical properties is necessary. In this paper, continuous stiffness measurement (CSM) and constant loading rate (CLR) mode nanoindentation was performed on shale samples before and after SC-CO2 treatment. With the aid of scanning electron microscope and energy dispersive spectra mapping technique, mechanical strength difference on clay-rich and quartz –rich areas in shale sample can be identified. The results demonstrated that samples treated by SC-CO2 present lower Hardness, Young’s modulus and fracture toughness. The average decrease rates of hardness and Young’s modulus under CSM mode for three sample are 32.01 % and 11.75 %. The hardness, Young’s modulus and fracture toughness under CLR mode for the three samples have decreased at average rates of 29.5 %, 11.0 %, and 11.3 %, respectively. Moreover, the mechanical strength substantially decreases in the clay-rich area because CO2 adsorption and mineral dissolution happen after the SC-CO2 treatment. The change in mechanical properties in quartz-rich area is much smaller because there is little effect on quartz. The close examination of indentation fracture geometry indicate more micro fractures have been generated in the post SC-CO2 treated shale, thus we can expect the capability of SC-CO2 for rock weaken. This study can provide more insights for fracture mechanism in target areas with different mineral distribution, which is beneficial for SC-CO2 engineering applications.

A new Lewis acid catalyzed alkyne–carbonyl metathesis/oxa-Michael addition relay was first reported, leading to the atom-economic synthesis of unreported functionalized indolone-containing naphtho[...

Interval-censored failure times arise when the status with respect to an event of interest is only determined at intermittent examination times. In settings where there exists a sub-population of individuals who are not susceptible to the event of interest, latent variable models accommodating a mixture of susceptible and nonsusceptible individuals are useful. We consider such models for the analysis of bivariate interval-censored failure time data with a model for bivariate binary susceptibility indicators and a copula model for correlated failure times given joint susceptibility. We develop likelihood, composite likelihood, and estimating function methods for model fitting and inference, and assess asymptotic-relative efficiency and finite sample performance. Extensions dealing with higher-dimensional responses and current status data are also described.

Cox regression models are routinely fitted to examine the association between time-dependent markers and a failure time when analyzing data from clinical registries. Typically, the marker values are measured periodically at clinic visits with the recorded value carried forward until the next assessment. We examine the asymptotic behavior of estimators from Cox regression models under this observation and data handling scheme when the true relationship is based on a Cox model using the current value of the marker. Specifically, we explore the impact of the marker process dynamics, the clinic visit intensity, and the marginal failure rate on the limiting value of the estimator of the marker effect from the Cox model. We also illustrate how a joint multistate model that accommodates intermittent observation of the time-varying marker can be formulated. Simulation studies demonstrate that the finite sample performance of the naive estimator aligns with the asymptotic results and shows good performance of the estimators from the joint model. We apply both methods to data from a study of bone markers and their effect on the development of skeletal complications in metastatic cancer.

The Cambrian strata in the North China Platform are fully exposed. A wide variety of carbonate oncoids with different shapes occur in the Xuzhuang and Zhangxia formations (Miaolingian Series) from six Cambrian sections in the study area. A comprehensive study involving outcrop description, microscopic observation, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and carbon and oxygen isotope analysis is conducted to determine the facies, morphology, internal structure, and geochemical properties of the oncoids. The oncoids are divided into six types based on their morphology and internal structure. Microscopic and ultrastructural observations reveal typical microbial fossils (Girvanella) and microbially-related sediments (framboidal pyrite), indicating the biogenicity of the oncoids. Additionally, the XRD and carbon and oxygen isotope analysis results suggest that the formational environments of these oncoids are different due to terrestrial influences. Statistical data on the oncoids from the six sections show that there are obvious differences in the types of oncoids and the proportions of different varieties in each section. The spatial differences in the oncoid morphologies are associated with different palaeogeographic settings. The rough oncoid growth patterns developed in nearshore environments were influenced by terrigenous debris and steep terrain, whereas the delicate oncoid growth patterns developed in offshore environments were less affected by terrestrial factors and were featured by more stable depositional processes related to microbial mats.

[Abstract The Chagan Depression in the Yingen‐Ejinaqi Basin, located at the intersection of the Paleo‐Asian Ocean and the Tethys Ocean domains is an important region to gain insights on terrestrial heat flow, lithospheric thermal structure and deep geodynamic processes. Here, we compute terrestrial heat flow values in the Chagan Depression using a large set of system steady‐state temperature data from four representative wells and rock thermal conductivity. We also estimate the “thermal” lithospheric thickness, mantle heat flow, ratio of mantle heat flow to surface heat flow and Moho temperature to evaluate the regional tectonic framework and deep dynamics. The results show that the heat flow in the Chagan Depression ranges from 66.5 to 69.8 mW/m2, with an average value of 68.3 ± 1.2 mW/m2. The Chagan Depression is characterized by a thin “thermal” lithosphere, high mantle heat flow, and high Moho temperature, corresponding to the lithospheric thermal structure of “cold mantle and hot crust” type. We correlate the formation of the Yingen‐Ejinaqi Basin to the Early Cretaceous and Cenozoic subduction of the western Pacific Plate and the Cenozoic multiple extrusions. Our results provide new insights into the thermal structure and dynamics of the lithospheric evolution in central China., System steady‐state temperature data measurements for typical wells in the Chagan Depression. ]

The marine shale in southern China has undergone complex tectonic evolution with a high thermal evolution degree. Excessive thermal evolution brings certain risks to shale gas exploration and development. With the advancement of experimental methods, the evolution process of shale reservoirs can be better understood from the micro-nanoscale. This work takes the Ordovician-Silurian Wufeng and the first member of Longmaxi Formation in the Sichuan Basin and Lower Cambrian Niutitang Formation in Outer Margin of the Sichuan Basin to study the impact of maturity upon the genesis of shale gas and development features of the reservoir. A series of geochemical research methods, including TOC, gas component and gas isotope, were adopted to study the impact of different thermal evolution stages of organic matter upon the genesis of shale gas. The nanoscale micro-imaging technique, such as FIB-SEM and FIB-HIM, was used to analyze the development of OM-hosted pores. As shown from the results, when R o = 1.2–3.5%, the marine shale gas is dominated by methane and other hydrocarbon gases, since the mixture of cracking gas from liquid hydrocarbons and kerogen-cracking gas cause the carbon isotope reversal. Besides, the pyrobitumen pores characterized by the strong connectivity and storage capacity were primarily developed. When R o > 3.5%, the organic matter is at the graphitization stage. The shale gas is mainly composed of nitrogen at this stage. The nitrogen is originated from the atmosphere and the thermal evolution process, and the OM-hosted pores (pyrobitumen and kerogen pores) characterized by the bad connectivity and storage capacity are developed. Finally, the main component of shale gas, the genesis of shale gas and the pattern of OM-hosted pores under different thermal evolution stages of organic matter are summarized, which provide technical support for the exploration and development of shale gas.

To evaluate the characteristics of microorganisms and the origin of organic matter of the Wufeng Formation and Longmaxi Formation (WF-LMX) in Sichuan Basin (South China), the type and number of microorganisms were determined in this study using scanning electron microscope (SEM) microphotographs and microbial extraction. The contribution of various microorganisms to organic matter was analyzed in combination with the data of biomarkers and total organic carbon (TOC). It can be deduced from the paleogeography and pristine/phytane (Pr/Ph) ratio that the microorganisms of WF-LMX resided in 60 m–200 m deep shelf with anoxic bottom water. From SEM microphotographs and microbial microscopy analysis, it was demonstrated that the microorganisms in the WF-LMX can be divided into 3 types: planktonic algae (mainly including acritarchs and green algae), fungi, and benthic algae. Acritarchs were the most common microorganisms in the WF-LMX with the average relative content of 60.5%. The average relative contents of benthic algae, fungi, and green algae were 17.6%, 18.0% and 3.9%, respectively. Since the acritarchs and green algae in the Wufeng Formation and the Longmaxi Formation basically belong to planktonic algae, the relative content of planktonic algae in them is about 64.4%. The strata of WF-LMX can be divided into 3 sections based on the distribution characteristics of various microorganisms. The relative content of acritarchs gradually decreased upwards, while that of benthic algae gradually increased. The multiple proxies of biomarkers proved that the planktonic algae was the main source of organic matter in the WF-LMX. Combining the statistical data of microorganisms, it was considered that the organic matter in WF-LMX was mainly derived from acritarchs, which might be the components of planktonic algae. The fungi had a significant contribution to the organic matter in organic-rich layers (TOC > 2.0%) rather than in organic-poor layers, while green algae and benthic algae made little contribution to the organic matters in WF-LMX.

In this study, matrix-related pores from differing depositional shales were explored comparatively. Among of them, Lower Cambrian shale (3.83%Ro) and Lower Silurian shale (2.61%Ro) were marine sediments with abundant oil-prone kerogen and rich siliceous minerals, while Upper Permian shale (2.44%Ro) were transitional sediments with redundant gas-prone kerogen and rich clay. The morphology and geometry of pores were investigated via fractal analyses based on N2 adsorption and direct imaging. The effects of organic matter (OM) within different shales were also highlighted through N2 adsorption before and after OM isolation. Lower Cambrian shale possessed the lowest pore volumes (PV) (averaging 0.0109 ml/g) and the lowest pore surface areas (PSA) (averaging 9.09 m2/g) as well as the smallest average pore diameters (APD) (averaging 5.47 nm). Dissolved pore with dead-end openings was the main type. The PV and PSA of isolated OM were only approximately 1 and 2 times higher than that of corresponding samples, respectively. In contrast, Lower Silurian shale possessed the highest PV (averaging 0.0109 ml/g) and the highest PSA (averaging 9.09 m2/g) as well as relatively large APD (averaging 13.43 nm). Organic-hosted pores (OMP) with cellular structure is the main type. The PV and PSA of isolated OM were approximately 8.5 and 3 times higher than that of corresponding samples, respectively. Upper Permian shale with the largest averaging pore diameters (averaging 18.82 nm) presented high PV (averaging 0.0209 ml/g) similar to that of Lower Silurian shale, and a low PSA (averaging 10.85 m2/g) like that of Lower Cambrian shale. Pore associated with clay flakes was the main type. The PV and PSA of isolated OM were only approximately 0.6 times and 1 times higher than that of corresponding samples, respectively. For marine shale, matrix-related pore features are synergy effects of the matrix basis where pre-existing space controls the occurrence of porous OM and functions as the shelter for OMP with an appropriate thermal maturity. However, extensive diagenesis can overprint the effects of matrixes on pore properties, because oil-prone kerogen is sensitive to thermal maturity. The specific material composition of transitional shale limit pore properties, because dominant structured OM is thermally stable with limited migration ability and pore contribution. Hence, diagenetic differences and material diversities may be attributed to the discrepancies of pore properties between marine shale and transitional shale.

Context Fruit of Avicennia marina (Forsk.) Vierh. (Acanthaceae) is used as a Chinese herb. Studies have found that it contains marinoid J, a novel phenylethanoid glycoside (PG) compound, but its neuroprotective functions are largely unknown. Objective This study evaluated the effects of marinoid J on vascular dementia (VD) and determined its potential mechanisms of action. Materials and methods The VD model was established by the ligation of the bilateral common carotid artery in Sprague–Dawley rats, who received daily intragastrically administration of saline, marinoid J (125 or 500 mg/kg body weight/d), or oxiracetam (250 mg/kg body weight/d) for 14 days (20 rats in each group). The Morris water maze (MWM) was used to evaluate cognitive performance. The hippocampus was subjected to histological and proteomic analyses. Results Marinoid J shortened the escape latency of VD rats (31.07 ± 3.74 s, p

Integrated analysis of reservoir quality, pore structure, depositional and petrologic characteristics, and types and degree of diagenetic alterations was done in this study by employing petrophysical evaluation, thin section observation, stable isotope analysis, scanning electron microscopy combined with EDS, X-ray computed tomography, and high-pressure mercury intrusion. The purpose was to investigate the macroscopic and microscopic heterogeneities, and the effects of depositional factors and diagenetic alterations responsible for them. The results indicate that the Chang 8 tight oil sandstone of the Longdong area in the Ordos Basin can be divided into three categories, namely the Type I reservoir, with porosity greater than 10% and permeability greater than 1.0 mD, having sparse lenticular distributions in the mouth bar of the braided delta front, the Type II reservoir, with porosity of 6–10% and permeability of 0.1–1.0 mD, mainly distributing in the distributary channel, and the Type III reservoir, with porosity less than 6% and permeability less than 0.1 mD, having a reticular distribution in the distributary bay. The Type I reservoir has an intergranular pore (Inter-P) dominant pore system with a greater pore-throat radius (1–10 μm), a larger pore volume and better connectivity. The Type II reservoir has a mixed system consisting of intragranular pores (Intra-P) and Inter-P with a pore-throat radius of 0.1–1 μm, smaller pore volume, and worse connectivity. The Type III reservoir is characterized by an Intra-P dominated system with a radius between 10 and 500 nm, smallest pore volume and worst connectivity. The wide range of porosity, permeability, and pore structure parameters can be attributed to the frequent variations in depositional facies and diagenetic alterations. Larger grain size, higher content of quartz and feldspar, and moderate grain-coating chlorite content (less than 8%) are favorable for the preservation of intergranular pores and dominate the formation of the Type I reservoir. The mesogenetic calcite and ferrocalcite cementation and pore-filling kaolinite precipitation obstruct the intergranular space and are the predominant factors tightening the reservoirs in the distributary channel and distributary bay, leading to multi-scale heterogeneities. Secondary porosity from dissolution plays a much more important role in contributing to the porosity and permeability of the Type II and III reservoirs than of the Type I reservoir. The study provide a comprehensive understanding for the multi-scale heterogeneities and can be used to predict the potential high-quality zones in tight oil sandstone reservoirs.

Global-scale cycling of silicon through the biosphere, atmosphere, and hydrosphere has received much attention although, silicon cycling in the Earth’s lithosphere remains poorly understood. As the products of internal heat and material exchange, igneous rocks preserve significant information of silicon migration through the lithosphere. Here we report silicon isotopic compositions of nine peraluminous granites from the Chinese Altai, which forms part of the Central Asian Orogenic Belt. These rocks are characterized by the heaviest δ30Si values (−0.13 ± 0.03‰ to +0.78 ± 0.05‰) compared to global granites, with a linear variation in the silicon isotopic values against silica content, with high silica-rich granites displaying more depleted isotopic compositions. In conjunction with the whole rock weakly negative ɛNd(t) and uniform δ26Mg values, as well as high δ18O values, we suggest that the δ30Si values of these granites were mainly inherited from the magma source, rather than produced by magmatic fractionation. In addition, the wide range of initial 87Sr/86Sr ratios and high Ba content of the samples suggest the role of aqueous fluids. The Chinese Altai is considered to have formed through accretion of volcanic arcs associated with subduction of the Paleo-Asian oceanic lithosphere. The magma derived through partial melting of metasomatic mantle scavenges the heavy 30Si isotopes derived through fluids released from oceanic sediments and transfers to the upper crust where partial melting of crustal sedimentary rocks occur. Mixing of these two melts generated the peraluminous granites. Our study offers a novel insight into a potentially important mechanism of silicon cycling in the lithosphere.

A silver-catalyzed nitration/annulation of α-alkynyl arylols is reported by using tert-butyl nitrite (TBN) as a NO2 radical precursor, from which a set of 3-nitrated benzofurans were synthesized with moderate to good yields. This transformation initiated by an in situ generated NO2 radical proceeds efficiently under mild and neutral redox conditions, which provides a new pathway toward the 3-nitrobenzofuran framework via catalytic difunctionalization of internal alkynes.

The Wufeng organic-rich shale is widespread in the Upper Yangtze platform, and it is one of the most advantageous shale gas producers in China. Its deposition commenced with the onset of the Boda warming event in the late Katian and terminated at the Hirnantian glacial maximum. The depositional mechanism of the Wufeng Formation was poorly understood owing to its relatively thin thickness, being interpreted as the result of organic matter (OM) accumulation in a shelf setting under anoxic conditions. This study integrated detailed geochemical analyses based on the core samples from three boreholes which are located in the outer-, middle- and inner-shelf of the Upper Yangtze platform, in order to investigate the depositional environments during the deposition of the Wufeng Formation. Geochemical redox proxies (Mo-EF, U-EF, and V/Cr) and productivity proxies (P, Baxs, Sixs) indicate that the deposition of the Wufeng Formation was associated with four intervals (WF1 to WF4), each characterized by its unique geochemical features related to sea-level fluctuations. Black siliceous mudstones deposited during WF1 and WF2 are relatively organic-lean due to low productivity, less favorable preservation conditions, and terrestrial dilution. Whereas black siliceous mudstone deposited during WF3 and WF4 is organic-rich due to high paleoproductivity and conducive preservation conditions. The geochemical proxies (Cd/Mo, Co x Mn) associated with the modern upwelling settings were replicated in the Wufeng Formation, revealing that the outer-shelf of the Upper Yangtze platform was dominated by persistent upwelling. The upwelling-driven primary productivity is considered as the first-order control for the OM enrichment at the outer-shelf of the Upper Yangtze platform. Seasonal upwelling may influence the middle-shelf of the Upper Yangtze Platform, where both primary productivity and preservation played essential roles in the OM accumulation. In contrast, the OM accumulation at the inner-shelf was fundamentally driven by good preservation conditions.

Two types of new oxidant-free radical multicomponent reactions of β-alkynyl ketones, aryldiazonium salts, and DABCO·(SO2)2 (DABSO) were established, leading to the tunable generation of two class o...

Organic matter is the material basis of shale hydrocarbon generation. The current organic matter content in shale is controlled by the original sedimentary organic matter abundance. Therefore, the study of the enrichment mechanism of sedimentary organic matter in shale has become an important issue to be solved. The Upper Yangtze area is the important exploration and exploitation area of marine shale gas in China. The shale of the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in the Yangtze area is the research object. Choosing redox indicator and biological productivity indicator, the study explores the enrichment mechanism of sedimentary organic matter from two aspects, sealing of water and volcanic activity. The results show that excess siliceous mineral in the shale of the Wufeng Formation-Longmaxi Formation in the Upper Yangtze area is bioorigin. Excess siliceous mineral can be used as one of the indicators of biological productivity. On the one hand, layer phenomenon occurred since the strong water sealing during the sedimentary period of Wufeng and the lower section of the Longmaxi Formation, which results in the high content of oxygen in surface water. On the other hand, the active volcanic activity brought volcanic ash which was beneficial to biological reproduction. Both of these factors led to higher biological productivity during this period. At the same time, the strong sealing of water made the lower layer of the water more reductive, and the active volcanic activity caused climate change, enhancing the reduction of the lower layer of the water, which made the rich organic matter deposited from the surface water well preserved. In the sedimentary period of the upper section of the Longmaxi Formation 1st member in the Upper Yangtze area, on the one hand, due to the weakened sealing of water, the oxygen content of the upper water decreased. On the other hand, the volcanic activity weakened until it stopped, and the source of volcanic ash rich in nutrient elements decreased. These two aspects led to lower biological productivity during this period. At the same time, the weaker water sealing could lead to a decrease in the reduction of the lower layer of the water, and the gradual cessation of volcanic activity no longer affected the climate, causing the destruction of sedimentary organic matter by oxidation.

The Jiaoshiba shale gas field and Pengshui area are both located in the southeast Sichuan Basin with only 100 km apart. Although these two areas obtained shale gas flow from the Lower Silurian Longmaxi marine shale, there is a huge difference of production in these two areas where the Jiaoshiba shale gas field is more productive than the Pengshui area. In order to figure out the reason that caused this difference, this study analyzed the Longmaxi marine shale in these two areas by using drilling cores, and mineralogical and geochemical data. The results show that the Jiaoshiba shale gas field has a higher quality shale reservoir (higher content of quartz, higher porosity, higher permeability and higher TOC (Total Organic Carbon)) in the Lower Silurian Longmaxi Formation than that of the Pengshui area. The Lower Silurian Longmaxi marine shale in the Jiaoshiba shale gas field contains a higher total gas content (3.65 m3/ton in average) than that of the Pengshui area (1.19 m3/ton in average). Through structure analysis, this study found that the Jiaoshiba shale gas field and the Pengshui area located in the different tectonic units. The Jiaoshiba shale gas filed is located in the East Sichuan fold belt (wide spaced anticlines area) at the west side of the Qiyue mountain fault where less fractures are developed and the pressure coefficient is more than 1.5, resulting in much more free gas preserved in the shale reservoirs in the Lower Silurian Longmaxi Formation (the ratio of free gas content and absorbed gas content is 1.6), while the Pengshui area is located in the Hunan-Hubei-Guizhou thrust belt area at the east side of the Qiyue mountain fault where much more fractures are developed and the pressure coefficient is less than 1.0, leading to less free gas preserved in the Longmaxi marine shale (the ratio of free gas content and absorbed gas content is 0.6), that is why the shale reservoir in the Pengshui area has a lower total gas content than that in the Jiaoshiba shale gas field.

Deposition of the organic-rich shales of the Wufeng and lowermost Longmaxi formations (late Katian through Hirnantian) occurred in a relatively stable tectonic setting and commenced at approximately 4.5 Myr prior to the end-Ordovician glacial maximum. These organic-rich shales are important because they provide a continuous sedimentary record of high-frequency eustatic changes associated with ice-sheet expansion and shrinkage. Here, we carried out a high-resolution cyclostratigraphic study of Fe3+ series and associated geochemical analysis of the Wufeng and lowermost Longmaxi shales in order to better understand sea-level cyclicity in the late Katian through Hirnantian ocean. The organic-rich shales deposited during this interval in the EHD1 drill core (Yichang, China) record four major Myr-scale eustatic cycles, which were associated with third-order sea-level fluctuations. Within each of these major cycles, 3–4 minor eustatic cycles corresponding to 405-kyr long eccentricity astronomical cycles were recognized and representing fourth-order eustatic changes. The cyclostratigraphic age of this study is generally in agreement with the radiometric dates in GTS2012, although the duration of the Hirnantian stage is ~0.5 Myr longer than previously thought. This study also infers glacial controls on the depositional environment of the organic-rich shales, as enhanced cooling triggered ice-sheet expansion and concurrent sea-level fall, leading to higher thermohaline circulation intensity and enhanced paleoproductivity through upwelling and terrestrial influx. In contrast, warming intervals led to ice-sheet shrinkage and concurrent deepening characterized by water column stratification and reduced nutrient supply. The results provide evidence in support of continuous continental glaciation in the late Katian through Hirnantian.

There are successes and failures in the exploration of marine shale gas in South China. In some shale gas plays with great basis for hydrocarbon generation, a phenomenon exists that gas loggings reflect low gas bearing in some of the wells and the gas is dominated by nitrogen rather than hydrocarbon gas. The study of nitrogen concentration in shale gas contributes to solve the question that how shale gas diffuses in complex tectonic areas, which helps to figure out the preservation requirements and accumulation mechanisms of shale gas and avoid exploration crisis. This study focused on the lower Cambrian shale in Xiuwu Basin, Lower Yangtze Region, with emphasis on the well Jiangye-1, using gas component analysis, stable nitrogen isotope analysis, overburden permeability tests in parallel and perpendicular directions, and FIB-HIM experiments, also combining with core description, outcrop observation, and seismic interpretation to explore the causes of the high-content nitrogen and low-content hydrocarbon in the lower Cambrian shale gas. The results show that the nitrogen of the lower Cambrian shale in Xiuwu Basin is derived from the atmosphere and the deep crust-upper mantle. The bedding planes and the detachment layer at the bottom of the lower Cambrian compose the lateral pathways, and the widespread deep faults are the vertical pathways for shale gas migration and diffusion. Combining these two, an effective pathway network was built, favorable to gas exchange between the shale gas interval and the atmosphere, partly leading to the concentration of nitrogen and the diffusion of hydrocarbon gas. In the Jurassic, the magmatic activities occurred frequently in the surrounding areas, which not only brought nitrogen from the deep crust-upper mantle but also increased the value of paleo-heat flow even though the basin began to uplift, which promoted the graphitization of organic matter and the collapse of organic pores and accelerated the loss of shale gas. Based on the study above, an explanation model was summarized to expound the causes of high-content nitrogen and low-content hydrocarbon in shale gas plays near the plate-active region in Xiuwu Basin, Lower Yangtze Region.

The exploration practices of marine and lacustrine shale gas in the Upper Yangtze Platform, South China show that there is a huge difference in gas content, which is mainly related to the difference of pore structure. This study is focused on marine Longmaxi and lacustrine Da'anzhai shales in the Upper Yangtze Platform, and their pore structure characteristics were compared and the mechanism of shale gas occurrence were discussed. First, the pore structures of marine and lacustrine shales were characterized and the effects of organic matter abundance, maturity and inorganic minerals on porosity were investigated. Then the contributions of different components to porosity were evaluated and the occurrence mode of methane in the pores of marine and lacustrine shales was established. The results show that (1) Three pore types can be observed in both marine and lacustrine shales: organic matter-hosted pores (OM pores), framework minerals-associated pores (FM pores), and clay minerals-associated pores (CM pores). OM pores are more developed in marine shale and CM pores are more developed in lacustrine shale. (2) Low pressure gas adsorption (LPGA) results show that the micropores of marine shale are dominated by pores of 0.4–0.7 nm and the micropores of lacustrine shale are dominated by pores of 0.5–0.9 nm, while the mesopores of marine shale are dominated by pores of 2–10 nm and the mesopores of lacustrine shale are dominated by pores of 3–30 nm, which are consistent with MIP results. (3) Organic matter has an impact on porosity of marine and continental shales but is not the most important controlling factor. And the contribution of organic matter to porosity in marine shale is greater than the contribution of organic matter to porosity in lacustrine shale. Shale porosity increases first and then decreases with the increase of maturity, which may be related to the carbonization of organic matter. (4) OM pores and CM pores tend to be preserved due to the presence of rigid grains that form rigid frameworks preventing these pores from collapsing. FM pores are mainly related to the dissolution of framework minerals by organic acids, and these dissolution pores can greatly improve the porosity and permeability of shale. (5) Quantification of porosity as related to mineralogy shows that OM pores contribute approximately 37% to total porosity of marine shale and 24% to total porosity of lacustrine shale and CM pores contribute approximately 53% to total porosity of marine shale and 67% to total porosity of lacustrine shale. (6) Shale gas occurrence is mainly controlled by the distribution mode of pore systems which are composed of OM pores, FM pores and CM pores. It is due to higher percentage on OM pores and lower percentage on CM pores that gas content of marine shale is generally higher than that of lacustrine shale.

The generation of S-type granites in the continental crust generally requires partial melting of metasedimentary rocks at relatively high temperatures, and is typically associated with syn- or post-collisional tectonics. These melts are generally expected to inherit the geochemical characteristics of their metasedimentary protoliths, and their Nd, Hf, and O isotopic compositions have been widely used to trace the origin of the magmas. Here we show that these isotopic systems are decoupled in S-type granites from the Chinese Altai, displaying a wide range of zircon ɛHf(t) values (−0.7 to +6.2), and a limited range of whole rock ɛNd(t) values (−6.1 to −2.2) and zircon δ18O values (+8.49‰ to +12.91‰). Zircon xenocrysts are common in these plutons, and show markedly negative ɛHf(t) values (from −30.7 to −18) and highly positive δ18O values (from +9.61‰ to +13.03‰). In addition, these granites exhibit high Lu/Hf (0.15 to 1.38) ratios, and substantial depletions in Zr and Hf. We develop a new model to explain the observed relationship between residual zircon content and Nd–Hf–O isotope decoupling. We propose that these S-type granites formed from partial melting of metasedimentary crustal rocks, associated with a ridge subduction-related heat source. Limited crustal heating, due to mantle upwelling through the slab window on a small scale, may have resulted in significant disequilibrium melting of the metasedimentary crust. Our findings provide new insights into melting processes in the deep continental crust.

The basins of the South Atlantic passive margins are filled with early rifting stage lacustrine sediments (Barremian, 129–125 Ma), transitional lacustrine and marine sediments (Aptian, 125–113 Ma), and drift stage marine sediments since early Cretaceous (Albian, 113 Ma). The South Atlantic margins can be divided into three segments by the Rio Grande Fracture Zone and the Ascension Fracture Zone according to variations in the basin evolution history and configuration style. The lacustrine shale and marine shale source rocks are developed in the rift stage and drift (post-rift) stage in the South Atlantic passive margins, respectively. The southern segment of the margins is dominated by the lacustrine sedimentary filling in the rifted stage overlain by a thin marine sag system as a regional seal, where the hydrocarbons are mainly accumulated in the structural-stratigraphic lacustrine reservoirs formed in the rift stage. The middle segment developed salty rift-sag-type basins with rift and sag systems and with salt deposited in the transitional intercontinental rift stage, where the lacustrine shale in the lower part of the rifted lacustrine sequence and the marine shale in the lower part of the sag sequence formed in the marine post-rift stage are high-quality source rocks. This segment in the middle is mainly dominated by pre-salt lacustrine carbonate and post-salt marine turbidite plays. The northern segment is characterized by sag-type basins with a narrowly and locally distributed rifted lacustrine system and its overlying widely distributed thick marine sag systems. Gravity-flow (mostly turbidite) marine sandstones as good reservoirs were extensively developed in the sag stage due to the narrow shelf and steep slope. The post-rift marine shales in the lower part of the sag sequence are the main source rocks in the northern segment and the hydrocarbons generated from these source rocks directly migrated to and accumulated in the deep marine turbidite sandstones in the same sag sequence formed in the drift stage. From southern segment to northern segment, source rocks and hydrocarbon accumulations tend to occur in the stratigraphically higher formations. The hydrocarbon accumulations in the southern segment are mainly distributed in the rifted lacustrine sequence while that in the northern segment primarily occur in the post-rift marine sequence.

Studies on the mechanisms of shale gas adsorption are of great significance for shale gas accumulation and reserves evaluation. In order to investigate the mechanisms of shale gas adsorption from the perspective of methane adsorption thermodynamics and kinetics, high-pressure methane adsorption and adsorption kinetics experiments were measured at 40.6 °C, 60.6 °C, 75.6 °C and 95.6 °C at pressures up to 52 MPa for the Lower Silurian Longmaxi shale sample collected from the Southern Sichuan Basin, China. The adsorption isotherms and kinetics curves of methane were obtained and a detailed analysis was performed. The results indicate that (1) Under the condition of 0–52 MPa, the absolute adsorption isotherm of methane on shale has the characteristics of type I adsorption isotherm. Temperature has an important effect on the maximum excess and absolute adsorption of methane. At the same temperature, the absolute adsorption amount of methane on shale increases slower at a higher pressure, which suggests that the methane adsorption rate decreases at a higher pressure. (2) The average isosteric heat of adsorption of methane on shale is 21.06 kJ/mol, indicating that the dominant adsorption process of methane on shale may be physical adsorption. The isosteric heat of adsorption increases with increasing absolute methane adsorption amount, indicating that the adsorption heat is mainly affected by the interaction between the adsorbed methane molecules. (3) Bangham kinetic model can be used to describe the dynamic adsorption process of methane on shale. Higher temperature and pressure lead to a lower Bangham adsorption rate constant, which makes it more difficult to adsorb methane molecules for shale. This is consistent with the conclusion drawn from the thermodynamics study of absolute adsorption isotherms of methane on shale.

Shale and its roof and floor are very important for shale gas preservation. How to clarify the mechanism of its vertical sealing and its effect on shale gas enrichment is a significant problem to be solved. In this paper, the objective layers are the Upper Ordovician Wufeng Formation, the first member of the Lower Silurian Longmaxi Formation and the Lower Cambrian Qiongzhusi Formation, which are all in the representative shale gas blocks in the Sichuan basin of the Yangtze region. Studied by statistical drilling data, the focus is on the detailed analyses of the JiaoYe-1, Ning-201 and Wei-201 well, and experiments were carried out such as the porosity test, the TOC content analysis and the experiment of overburden permeability, permeability experiments before and after adsorption of methane under different osmotic pressure, and isothermal adsorption experiments. The experiments results are applied on studying the effect of shale and its roof and floor on shale gas enrichment, combined with formula deduction. The results show that the roof and floor have a vertical sealing effect on the organic-rich shale by the difference of physical properties. In eastern Sichuan, the roof of the organic-rich shale of the Wufeng Formation and the first member of Longmaxi Formation is assemblage of argillaceous siltstone and siliceous shale, while in southern Sichuan it is assemblage of gray shale and siliceous shale. The floor is nodular limestone and limestone in both areas. The combination of roof and floor, with low porosity, can form a quality roof and floor sealing ability in the absence of fracture development. Its sealing ability is stronger than that in the upper part of the Qiongzhusi Formation, considering its roof and floor composed of argillaceous siltstone and siliceous shale. The floor of the organic-rich shale at the bottom of the Qiongzhusi Formation is a dolomite reservoir with good storage capacity, between which there is an unconformable contact causing the worst sealing ability among the three intervals. With the increase of burial depth, the overlying pressure of shale increases. With the increase of TOC content and thickness, the amount of adsorption gas of shale increases. These two aspects of factors can lead to the permeability decline and self-sealing enhancement of the organic-rich shale. In this study, focusing on the Upper Ordovician-Lower Silurian and the Lower Cambrian in the Sichuan basin, four patterns of organic-rich shale and its roof and floor were summed up, and the rapid evaluation method of sealing of shale and its roof and floor under the limited geological data was established.

Numerical simulation of the tight reservoir oiliness has always been an important issue in tight oil resources exploration. It is hard to take some special situations into simulations such as the micro-nano thermodynamic system, the multi-fluid phase behavior, and the superimposed tectonic stress field of tight oil reservoirs. In our research, we use MCMC methods to simulate the tight reservoir oiliness constrained by some visualized, spatial-related and interacted geological parameters based on the statistic Bayesian theory, instead of taking the complicated accumulation mechanism into consideration. In this research, we built a posterior probability density distribution (Post-PDD) matrix using the spatial relation between oiliness, fracture, and lithofacies parameters of a typical Yanchang tight oils outcrop. In the simulation, one Monte Carlo Step (MCS) was settled N = 80 × 36 × 5000, where 80 and 36 represent the horizontal and longitude grid number respectively, and 5000 represents the sampling times for each grid. In total, simulations of 50000 MCSs were made for each realization. For the simulation results, the variation in the fluctuating trends of the fitted and actual values matched well with the analytic variogram for the MCMC realizations. Additionally, we found that the simulation uncertainty was consistent with the reservoir heterogeneity. Even though the lamina, intercalation or the barrier was not defined in the grid model, the oiliness realization of the different types was remarkably consistent with the reservoir heterogeneity, which may be caused by the sedimentary rhythm similitude between different scale sedimentary cycles, particularly in the lacustrine tight reservoir.

Based on detailed sedimentological observations and geochemical analyses, four geological events have been identified, and a genetic depositional model has been established within a sequence stratigraphic framework. The organic-rich siliceous shale interbedded with dense bentonite layers in the transgressive systems tract 1 (TST 1) is attributed to the first stage of high-frequency volcanism (which started at ∼447.62 Ma) associated with the collision of the Cathaysia and Yangtze Blocks. The presence of the organic-fair lime mudstone/shelly limestone indicates that Hirnantian Glaciation in the highstand systems tract (HST). The occurrence of organic-rich siliceous shale interbedded with scarce bentonite layers in the transgressive systems tract 2 (TST 2) is attributable to the second stage of low-frequency volcanism (which started at ∼443.83 Ma) and to postglacial effects. The formation of organic-fair mixed shale with silty laminae is attributed to bottom-current activity in the early highstand systems tract (EHST). The occurrence of organic-poor clay-rich shale is due to terrigenous input in the late highstand systems tract (LHST). Our research also shows that the high marine productivity caused by volcanic ash and a high burial rate in an anoxic depositional setting led to organic matter and siliceous mineral enrichment in the TST 1 and TST 2. The favorable organic matter preservation conditions and the postglacial biotic recovery played significant roles in the formation of the organic-rich shale in the TST 2.

Markov processes offer a useful basis for modeling the progression of organisms through successive stages of their life cycle. When organisms are examined intermittently in developmental studies, l...

A Cu-catalyzed [4+1] annulation of N-aryl-1,2,3,4-tetrahydroisoquinolines (N-aryl THIQs) with α-diazoketones has been established under oxidative conditions, leading to the construction of a series of indolo[2,1-a]isoquinolines with generally good yields. The reaction enables dediazotized dicarbonylation of α-diazoketones, creating direct C(sp3 )/C(sp2 )-H bond bifunctionalization to access tetracyclic aza-heterocyclic skeletons.

Understanding the properties of sedimentary rock shale is critical for wellbore stability and hydraulic fracturing design in unconventional shale gas extraction. The mechanical properties of shale are a function of various environmental factors, such as stress, temperature, saturation and loading rate. Thus, in this study, the loading rate effect on the mechanical behavior of shale using nanoindentation was investigated. Nanoindentation tests were performed at a peak load of 500 mN and loading rates of 5–30 mN/s. In addition, X-ray diffraction (XRD) analysis was performed to identify the composition of the selected shales, and reveal the target sample is brittle. Scanning electron microscopy (SEM) analyses were performed to determine the surface morphology and demonstrate the existence of pile up and sink-in events. The results of the nanoindentation study indicate that the material behavior of rock depends on the loading rate at the nanoscale: with the increase in the loading rate, the contact hardness, Young's modulus, yield stress and indentation shear stress gradually increase. However, final penetration depths, the contact penetration depths, the maximum penetration depths and the contact stiffness decrease with increasing loading rates. Pop-ins were imperceptible at both the low and high loading rates, reflecting that the shale is brittle. Comparison of the pressure hardening coefficient in the elastic–plastic yield criterion model and the strain hardening coefficient in the strain rate sensitivity model indicates that shale is more sensitive to pressure hardening than strain hardening. A discussion regarding the uncertainty of evaluating the mechanical properties via nanoindentation indicates that the contact surface determination and the loading rate control are both critical to obtain a meaningful value for the mechanical parameters.

The Pearl River Mouth Basin (PRMB), the largest basin in the northern continental margin of the South China Sea (SCS), has been one of the key areas to characterize geothermal field and thermal evolution of a passive continental margin. The thermal history of the Pearl River Mouth Basin is related to the seafloor spreading of the SCS in the late Early Oligocene. Heat flow measurements show that the PRMB is characterized by a high background heat flow with average heat flow of 71.8 ± 13.6 mW/m2. The present-day heat flow of the northern SCS increases from the northern shelf with the thick crust to the southern slope with the thinned crust. This study employs forward and inverse modeling to simulate the rift and post-rift processes exampled by four wells at different structural settings. Two thermal evolution models of the PRMB are established for continental shelf and continental slope. In the continental shelf, heat flow increased rapidly twice during the syn-rift stage, and then followed by continuous thermal subsidence with heat flow value decreased during the post-rift stage. While the heat flow in the slope continuously increased due to lithospheric thinning, mantle upwelling and resulting multi-episode seafloor spreading in SCS during the Neogene post-rift stage, which is different from the previously proposed decreasing heat model for the slope during the post-rift. Heat flow gradually reduced after the cessation of the sea floor spreading (10 Ma). The local multi-staged magmatic activities mainly contribute to the high level of maturity in the Liwan Sag located in the lower slope.

Sedimentary environment and redox conditions play a significant role in the formation of organic-rich shale. The vertical variations of major/trace elements, TOC (total organic carbon) and mineral compositions were investigated for the Lower Silurian Longmaxi typical marine shale in the Upper Yangtze Platform, South China, to decipher sedimentary environment (redox conditions, detrital input, sedimentation rate (SR), paleoproductivity and watermass restriction). This gives insight to the effects of variations in sedimentary environment on the formation of organic-rich shale. The results show that the Lower Longmaxi Formation is composed of three systems tracts: TST (transgressive systems tract), EHST (early highstand systems tract) and LHST (late highstand systems tract). From TST to LHST, the contents of TOC, quartz and pyrite decline steadily, whereas clay minerals and carbonate show an increasing trend. Thus, organic-rich siliceous (ORSS), organic-moderate mixed (OMMS) and organic-lean argillaceous (OLAS) shales are dominant for TST, EHST and LHST, respectively. Due to a continues fall of the relative sea-level, a deep-water shelf environment with anoxic condition, high paleoproductivity and low detrital input in TST gradually evolves into a semi-deep-water environment with dysoxic-oxic conditions, moderate paleoproductivity, and moderate detrital influx in EHST, further to an environment of oxic condition, low paleoproductivity, and high detrital flux in LHST. As evidenced by Mo-TOC and Mo U patterns, ORSS was deposited in a moderately restricted watermass, weaker than Black Sea, which progressively evolved into an enhanced restriction degree during the deposition of OMMS and OLAS due to a fall of relative sea-level. Major/trace elements and excess silica (EX-SiO2) concentrations illustrate that origins of quartz in the Lower Longmaxi shale are primarily terrigenous, biogenic and authigenic (smectite illitization). The average proportions of EX-SiO2 (biogenic and authigenic quartz) are 52.34%, 24.86% and 6.57% for ORSS, OMMS and OLAS, respectively. Biogenic quartz is the dominant contributor to EX-SiO2, while the contribution of authigenic quartz is limited, and the formation of the former is earlier than the latter according to the diagenetic transformation temperature. As both biogenic quartz and organic matter are firmly related to the abundance and preservation of paleoorganisms, anoxic condition, high paleoproductivity, low detrital flux and moderate restriction collectively control the high enrichment and preservation of organic matter and biogenic quartz, while oxic condition, low paleoproductivity, high detrital flux and stronger watermass restriction are unfavorable for the enrichment of biogenic quartz and organic matter.

Marine shales of the Lower Cambrian Qiongzhusi and Lower Silurian Longmaxi formations are extensively distributed in the Yangtze Platform. Detailed depositional and tectonic analyses and regional mapping indicated that the organic-rich Qiongzhusi-equivalent shale was deposited in an intra-shelf low-slope environment in a passive margin setting. The Longmaxi-equivalent shale was mainly deposited in a widely-distributed intra-shelf low setting in the Upper and Middle Yangtze, and in a distal foredeep area away from clastic dilution in the Lower Yangtze Platform. The transgressive and early highstand system tracts in both Qiongzhusi and Longmaxi shales produced the best-quality shale reservoirs, with high total organic matter (TOC) content (>2%) and high quartz content (>45%). Tectonics has substantial effects on coeval deposition of organic-rich shale and its hydrocarbon accumulation and production. Later tectonism deformed the shales and disrupted early shale gas accumulation. Recent shale gas resource exploration and geologic analysis suggested that the high rate of shale gas production is due to overpressured marine shale reservoirs with high TOC and high gas content in the tectonically-stable area. Shale gas production occurred at reduced rates in slightly underpressured shale reservoirs with lower gas content in the syncline of the tectonically-transitional area deformed by three tectonic movements. There was no gas production from shales in the tectonically-active area disrupted by at least four tectonic movements and complex faults. The results of this analysis indicate that local tectonically-stable areas in the Middle and Lower Yangtze platforms may have shale gas accumulation and production potential.

The mechanical properties such as Young's modulus, hardness and fracture toughness of Lower Silurian Longmaxi shale samples from Youyang area in southeast Chongqing, China were investigated using dot matrix nanoindentation measurements. With the help of field emission scanning electron microscope (FESEM) and energy dispersive X-ray fluorescence spectroscopy (EDS), the indentation morphology and mineral composition in indentation area were quantitatively analyzed. According to mechanical strength classification, a micromechanical model with three components was introduced and the Mori-Tanaka model was used to upscale mechanical parameters from nano-scale to centimeter-size scale, which were further compared with uniaxial compression results. The experimental results show that there is a positive linear correlation between Young's modulus and hardness and between the Young's modulus and the fracture toughness under nano-scale; the Young's modulus, hardness and fracture toughness perpendicular to the bedding are slightly lower than those parallel with the bedding. According to data statistics, the mechanical properties at the nano-scale follow Weibull distribution feature and the dispersion degree of hardness results is the highest, which is mainly due to shale anisotropy and nanoindentation projection uncertainty. Comparing the results from nanoindentation test, with those from upscaling model and uniaxial compression test shows that the mechanical parameters at the nano-scale are higher than those from upscaling model and uniaxial compression test, which proves mechanical parameters at different scales have differences. It's because the larger the core, the more pores and internal weakness it contains, the less accurate the interpreted results of mechanical parameters will be. Key words: nanoindentation, rock mechanics, Longmaxi Formation shale, Weibull distribution, Mori-Tanaka model

A new palladium(II)-catalyzed cyclization-radical addition cascade enables the direct construction of 1,3-dimethylene-substituted isobenzofuran derivatives containing a vinyl aryl sulfone unit in good yields by treating with β-alkynyl ketones, aryl diazonium salts, and DABCO·(SO2)2. The oxidant-free multicomponent reaction features good substrate scope and functional group tolerance, which proceeds through a sequence of Heck coupling, oxo-cyclization, and SO2 insertion.