Oil and gas exploration and development breakthroughs in the Shahejie Formation, Bohai Bay Basin, have provided key support for increasing reserves and production of offshore oil and gas in China. However, the potential and volume of its shale oil resources remain unclear. Theoretical studies are needed for key sags to improve the shale oil classification and evaluation system, so as to provide scientific guidance for accelerating oil and gas exploration and development in the Bohai Sea area.Based on analyses of geological and geochemical characteristics, rock pyrolysis, and multi-temperature-step pyrolysis data of Paleogene shale in the Liaozhong Sag, this study clarified the characteristics of retained hydrocarbons. Three indexes, namely TOC, free hydrocarbon content (S₁), and S₁/(ω)TOC, were selected as the key parameters for shale oil sweet-spot evaluation. According to the enrichment degree, shale oil resources in the study area were classified into four levels: enriched, moderately enriched, low-efficiency, and ineffective resources. Classified resource volumes of each interval were then calculated using the volumetric method.The results show that:① The Paleogene shale in the Liaozhong Sag consists of seven lithofacies, dominated by felsic and mixed shale;② Multiple kerogen types are developed, dominated by Type Ⅱ₁ and Ⅱ₂ kerogen with favorable oil-generation potential. The shale is generally in the mature stage, with an average TOC value above 1.4%, indicating excellent hydrocarbon generation potential;③ After light-hydrocarbon restoration and heavy-hydrocarbon correction, the oil-bearing property of shale is significantly improved. The third member of the Shahejie Formation has the best geological conditions, and the northern Liaozhong Sag is the most favorable exploration sub-sag. Comprehensively considering hydrocarbon generation, oil-bearing property, and mobility, organic-rich felsic shale and organic-rich mixed shale are confirmed as the dominant lithofacies with the highest exploration value;④ The total estimated shale oil resource volume in the study area is 13.42×10⁸ tons by conventional calculation, and reaches 29.09×10⁸ tons after correction. The third member of the Shahejie Formation contributes the largest proportion of resources, with enriched resources mainly concentrated in the northern Liaozhong Sag, which is the key exploration breakthrough target in the future.

Improving the understanding of plant water uptake strategies and the underlying mechanisms in ecologically vulnerable regions significantly contributes to the local ecological protection and hydrological management. However, the water uptake patterns of different growth forms, as well as the relative importance of belowground and aboveground stresses on plant water uptake variations within and between life forms under the dual influences of human activities (e.g. tunneling) and environment, are not sufficiently understood in this region. Isotope, soil water content, and chlorophyll fluorescence indicator (Fv/Fm) were combinedly used to investigate patterns of water uptake in four areas (low elevation-LE, middle elevation with tunneling-MT, intermediate elevation without tunneling-MUT, and high elevation-HE) along a southeastern margin of the Qinghai-Tibet Plateau. In LE and HE, plants used high proportion (55.1 %) of shallow water during the early growth season (May), whereas the contribution of shallow water was low (30.4 %) in intermediate elevations in this season. An average 11.4 % higher contribution from shallow soil water and 5.1 % lower contribution from groundwater in MUT compared to MT was observed in the period of tunneling, which was related to the hydrological change by tunneling. Belowground stress exhibited a significant correlation with the contribution of the 0-40 cm soil layer for herbs, whereas aboveground stress was significantly correlated with the contribution of a deeper layer (40-80 cm) for trees. The links between niche overlap and belowground stress explained the varied water uptake proportions for different plant forms. This study emphasized the effect of tunneling on plant water uptakes and varied strategies of adaptation on belowground and aboveground stresses for coexisting plants.

A growing number of studies have examined the effects of group counseling on students' mental health or academic functioning in China; no meta-analysis of these studies has yet been conducted, which may limit school-based applicability or the development of service systems. This study sought to establish an overall effect size for group counseling interventions, as well as identify potential moderator variable effects on their efficacy for Chinese mainland adolescents in particular. A total of 611 studies, comprising 15,320 adolescent participants altogether, were included, with meta-analyses conducted for six mental health outcomes and five academic functioning outcomes. The results showed that, at posttest, group counseling had statistically significant medium to large effects on depression symptoms (standardized mean difference [SMD] = -0.835), anxiety symptoms (SMD = -0.722), loneliness (SMD = -0.791), sleep problems (SMD = -1.075), self-harm (SMD = -1.463), suicidal ideation (SMD = -1.055), learning motivation (SMD = 0.952), learning engagement (SMD = 1.478), academic self-efficacy (SMD = 1.264), academic procrastination (SMD = -1.528), and learning burnout (SMD = -1.591). The moderator results suggest that group counseling might work best as a small-scale intervention and that online intervention resulted in improvements comparable to face-to-face intervention. This study demonstrates that school-based group counseling effectively enhances both the mental health and academic functioning of Chinese adolescents. Our finding highlights the importance of such interventions in addressing psychological and educational challenges in schools, providing evidence for educators and policymakers to strengthen these support systems. Future research should explore how intervention components interact to optimize their impact in school settings. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Eliminating implicit local government guarantees (ILGGs) is crucial for regulating government borrowing and preventing local debt risks. As a key tool for structural deleveraging, the weakening of ILGGs has significant policy spillover effects, yet the micro-level transmission pathways remain underexplored. From the perspective of ILGG weakening under central government debt resolution policies, this study examines its impact and mechanism on corporate effective tax burden using a sample of 2,178 listed firms in China from 2015 to 2023, employing an intensity-based Difference-in-Differences approach. The findings reveal that the weakening of ILGGs significantly reduces corporate effective tax burden. Mechanism analysis indicates that this reduction occurs through the channel of enhancing firms' new quality productive forces. Heterogeneity analysis further shows that the reduction effect is stronger for non-state-owned enterprises and firms in competitive industries. This study enriches research on the microeconomic effects of weakening ILGGs and provides novel empirical evidence for alleviating corporate effective tax burden.

Due to the complexity of the lithofacies associated with shale oil in saline lacustrine basins, the differences of shale oil occurrence state and its controlling factors in different lithofacies are not completely clear. This hinders efficient shale oil exploration and development. We investigated the shale oil in the Permian Lucaogou Formation in the Jimusar Sag, Junggar Basin, China, based mainly on sequential solvent extraction, petrological, organic geochemical, and nuclear magnetic resonance techniques. The fluidity of extractable organic matter decreased from the first extract to the fourth extract, which was caused by the gradual decrease in the contents of saturated and aromatic hydrocarbons, and gradual increase in the contents of NSO compounds and asphaltenes. The contents of free hydrocarbons (the first and second extracts) and adsorbed hydrocarbons (the third and fourth extracts) are very different among the lithofacies. The free hydrocarbon ratios in the siltstones and carbonate rocks are >70% and the main pore throats are >1 mu m in size, corresponding to the best sweet spots. The contents of free hydrocarbons in the laminated silty mudstones and shales with bedding fractures are >50%, which are also available. The free hydrocarbons in the siltstones and carbonates are saturated with migrated hydrocarbons, with the contents being more affected by the physical properties of rocks. In contrast, the free hydrocarbons in the mudstones are mainly self-generated and -stored, and their contents are controlled by total organic carbon contents and maturity. For the adsorbed hydrocarbons, the contents in all lithofacies are controlled mainly by the total organic carbon contents. The biomarker parameters record a slight increase in maturity from the fourth to the first extract. The & sum;C22-/& sum;C23+ values of n-alkanes in the third extract are the lowest, because carbonate minerals tend to capture long-chain n-alkanes. The sequential solvent extraction method provides new insights into the occurrence state and molecular geochemical characteristics of lacustrine shale oil in different lithofacies. Future exploration should focus on siltstones and carbonate rocks with a relatively high proportion of the first extract (free hydrocarbons occurring in large pores and fractures), and mudstones with a relatively high proportion of the second extract (free to adsorbed hydrocarbons occurring in matrix pores) that are suitable for hydraulic fracturing to aid production.(c) 2025 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The Early Jurassic Toarcian Oceanic Anoxic Event (T-OAE), also known as the Jenkyns Event, approximately aligns negative carbon isotope excursions (N-CIE), a stratigraphic marker for Toarcian environmental change. It represents a significant period of greenhouse warming and marine anoxia during the late Early Jurassic, impacting both marine and terrestrial ecosystems. This study explores its effects on terrestrial ecosystems at high latitudes for the first time, specifically focusing on the lacustrine Junggar Basin in northwest China, located at approximately 60 degrees N. By utilizing organic geochemical analyses of fine-grained sedimentary rocks from the Lower Jurassic Sangonghe Formation, we mapped the presence of higher-plant-derived hydrocarbons to reconstruct vegetation shifts before, during, and after the N-CIE interval. Our findings reveal an initial dominance of ferns, with a shift toward gymnosperms such as conifers and cycads during the event, and a subsequent return to fern dominance, as recorded by anomalies in di- and tri-cyclic aromatic hydrocarbon fractions. This suggests sig-nificant ecological adaptations and potential recovery or further adaptation following the N-CIE. Our findings underscore the sensitivity of high-latitude terrestrial ecosystems to dramatic climatic events like the T-OAE, emphasizing their importance in understanding past environmental changes and improving predictions of future ecological responses. These results also highlight the suitability of molecular terrestrial plant fingerprints as archives of global environmental change

Atmospheric convection is predicted to change in response to anthropogenic global warming, leading to a poleward expansion of the Hadley cells and associated arid climate belts. The magnitude of possible latitudinal change in the position of climate belts is, however, poorly understood. Here, we address this issue based on a case study of the early Toarcian (late Early Jurassic) Oceanic Anoxic Event (T-OAE, similar to 183 Ma), one of the most significant global change events of the Phanerozoic, characterized by elevated humidity and major disturbances to terrestrial ecosystems on land. We present new leaf-wax n-alkanes delta 13C data from the high-paleo-latitude Junggar Basin (northwest China) spanning the T-OAE and develop a time-space framework of plant-fractionation change, from low- to high-paleolatitudes across this time interval. We show that significant latitudinal changes in humidity occurred across the T-OAE (similar to 10 degrees), likely because of a significant northward expansion of the low-latitude arid belts to mid-paleo-latitudes, and by inference a latitudinal expansion of the Hadley cells. This has important implications for the anthropogenic global warming and its effects on climate belts.

The WRF model often struggles to accurately replicate specific characteristics of the atmospheric boundary layer, particularly under highly stable conditions. In this study, we reconstructed an OBS-nudging module using meteorological data with high spatiotemporal resolution, then coupled it in the WRF model (WRF-OBS) to improve stable boundary layer (SBL) simulation over the North China Plain (NCP). The results showed that WRF-OBS improved the simulation of SBL characteristics and reduced the deviation from observations significantly. The correlations (R2) between WRF-OBS simulations and observations of 2 m temperature, relative humidity, and 10 m wind speed at 460 stations across the NCP were 0.72, 0.56, and 0.75, respectively, which were much higher than the values for results from the unassimilated WRF model (WRF-BS). The simulated vertical profiles of temperature, relative humidity, and wind were generally consistent with observations at Pingyuan station. The meteorological factors which caused heavy air pollution was also investigated based on WRF-OBS simulation. The SBL characteristics obtained from WRF-OBS showed that light wind persisted over the NCP region during the period of heavy pollution, and Pingyuan was affected by warm and humid air. Vertically, the persistent temperature inversion at Pingyuan station was one of the main drivers of the heavy pollution. The WRF-OBS simulation captured the characteristics of the two temperature inversion layers very well. The two inversion layers covered the NCP, with a horizontal scale of approximately 200 km, and created very stable conditions, preventing the vertical diffusion of pollutants and maintaining high PM2.5 concentrations.

A set of organic-rich shales of the upper Permian Longtan Formation, which is widely developed in the northeastern part of the Sichuan Basin, is a key formation for the next step of exploration and development. At present, most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales, and basic studies on the palaeoenvironment and organic matter（OM） enrichment mechanism have not been fully carried out. In this paper, we recovered the sedimentary palaeoenvironment by mineralogical, elemental geochemical and organic geochemical analyses, and explored the enrichment mechanism of OM under the constraints of palaeoenvironmental evolution. The shales can be divided into two stages of sedimentary evolution: compared with the shales of the Lower Longtan Formation, the shales of the Upper Longtan Formation are relatively rich in quartz, poor in clay and carbonate minerals, and the OM type changes from type Ⅲ to type Ⅱ 2 . The depositional environment has undergone a change from sea level rise, from warm and wet climate to dry and cold climate, and from oxygen-poor condition restricted to open reduction environment; the land source input has decreased, the siliceous mineral content has increased, the biological productivity has improved, and the deposition rate has changed from high to low. A depositional model was established for the shales of the Longtan Formation, reflecting the differential reservoir formation pattern of organic matter. For the Lower Longtan Formation shales, the most important factors controlling OM content are terrestrial source input and deposition rate, followed by paleoclimate and paleooxygen conditions. For the Upper Longtan Formation shales, the most important controlling factor is paleo-productivity, followed by sedimentation rate. The depositional model constructed for the Upper and Lower Longtan Formation shales can reproduce the enrichment of organic matter and provide a basis for later exploration and development.

Planetary boundary layer height (PBLH) plays a significant role in air quality and climate change. At present, there is a lack of study that focuses on the PBLH characteristics with high spatiotemporal resolution and the subregional variation over China. In this study, we investigated PBLH climatology and its relationship with meteorological parameters across China from 2000 to 2020 using the ERA5 datasets. The PBLH varied diurnally and peaked between 14:00 and 16:00 Beijing Time at an average height between 0.8 km and 1.5 km. The seasonal characteristics of the PBLH also varied among regions. In most regions, the PBLH at urban sites is highest in spring and summer, and lowest in autumn and winter. Interestingly, the PBLH at most urban sites in East China was highest in autumn and lowest in spring. Spatially, in warm seasons (spring and summer), the PBLH showed a strong north-to-south gradient. PBLH was positively correlated with temperature at 2 m, wind speed at 10 m, sensible heat flux, and latent heat flux at most urban sites. However, PBLH was negatively correlated with relative humidity, as well as with surface PM2.5 concentrations. The vertical profiles of PM2.5 and PBLH exhibited an opposite trend that the lower PBLH was accompanied by higher PM2.5 concentration below PBLH at the same time on different days both at Qingshen and Rongchang Stations. In addition, we investigated the relationship between high and low temperatures and PBLH, and found that most sites have a positive correlation between high and low temperatures and PBLH, while coastal cities have a negative correlation between PBLH and low temperatures. We further explored the PBLH characteristics during two periods of extremely high temperatures in July and August 2022 in the Sichuan Basin and extremely low temperatures in the north of Northeast China in January 2023. Compared with the same months during 2011-2020, the PBLH at 16:00 BJT in July (August) increased significantly with 0.68 km (1.24 km), 0.38 km (1.06 km), and 0.69 km (0.89 km) in Chengdu, Chongqing and Yibin, respectively. During the period of extremely low temperature, compared with the corresponding period of the past decade, the PBLH decreased by 45 m (23% reduction), 100 m (37% reduction) and 70 m (16% reduction) at Mohe, Qiqihar and Jixi sites. This study helps to better understand the characteristics of PBLH in China, and it can also provide a reference for studies focusing on the evolution of atmospheric boundary or changes in air quality under the background of climate change.

高峰场地区上二叠统发育吴家坪组黑色页岩,为四川盆地页岩气勘探的新层系,但是吴家坪组页岩中石英的形成机制尚不清楚,影响到该层系储气潜力等的评价.本次研究利用X衍射分析、扫描电镜、主微量元素、稀土元素、能谱分析等手段,对川东高峰场地区吴家坪组页岩的石英成因进行深入解剖.研究认为,在该地区吴家坪组页岩主要发育的黏土质页岩、硅质页岩和混合质页岩三种岩相类型,识别出了陆源石英、生物成因石英和成岩转化过程中形成的石英三种类型,不同岩相中石英的成因类型存在差异.黏土质页岩中,石英含量与TOC,Ba(bio)无相关性,SiO2与Zr呈正相关性,表明陆源石英是黏土质页岩中最主要的石英成因类型;混合质页岩中,石英含量与TOC,Ba(bio)具有一定相关性,且SiO2与Zr呈正相关关系,表明具有陆源石英和生物成因石英的复合类型.在硅质页岩中,石英含量与TOC,Ba(bio)具有一定相关性,且SiO2与Zr呈负相关关系,表明生物成因石英为其主要石英类型.从而厘清了岩相与石英成因的耦合机制,并建立相应的模式图.

Pore and its structural characteristics are key parameters affecting shale gas reservoir development. Accurate quantitative characterization of shale pore and its structural characteristics is of great significance for evaluating shale reservoir state. In this study, 15 shallow marine shale samples were collected in Well Y108. X-ray diffraction results indicate that brittle minerals are the most common components in shale. In this paper, various pore types are classified and characterized by scanning electron microscope images. The total porosity of shale measured by the mercury intrusion method is between 3.2% and 6.5%. In addition, a petrophysical model is established to calculate matrix porosity and fracture. The results of this model are consistent with the measured porosity. Three key parameters (VTOC > VBri > VClay) were obtained. The low-pressure N2/CO2 adsorption experiment allows for the analysis of pore volume, specific surface area, and pore size. Finally, it was determined that the primary pore types and primary shale gas reservoir space in shallow marine shale are mesopores and micropores. The impact of shale constituents on pores and their structural properties is also covered in this work. The results indicate that the enrichment of total organic carbon and brittle minerals is conducive to the development of shallow marine shale pore-fracture system. Additionally, there is a positive linear relationship between matrix porosity, pore volume, specific surface area, average pore diameter, and surface porosity.

The upper Permian Longtan Formation (LTF) shale is a new shale gas exploration and development focus in China, which was formed in a transitional depositional environment. Because of the difference in the sedimentary environment between marine-continental transitional shale and marine shale, the enrichment characteristics and mechanism of organic matter (OM) are very different. Because of a weak research foundation, the enrichment mechanism of OM in the LTF shale in the Sichuan Basin is still unclear. In this paper, shale samples of the upper Permian LTF from the Well F5 were collected, and the abundance, source and sedimentary environment of organic matter were studied by using paleoclimate, detrital input, redox, paleopmductivity and sedimentation rate parameters. The results show that the TOC content of the LTF shale is high (average = 3.04%) and reaches the high to overmature stage (average = 2.46%), indicating a favorable source rock. The LTF shale was deposited in a humid and hot climate, which was conducive to the growth and prosperity of a large number of plants. The source of organic matter was mainly terrestrial plant fragments. The sedimentary environment of the LTF shale was oxic, it had a high sedimentation rate, which reduced the oxidation rate of OM, promoted the rapid deposition of OM, and ensured the preservation of organic matter. In summary, the enrichment of OM of LTF shale in the Sichuan Basin was affected by the sedimentary environment, which was complicated. The main controlling factors were detrital input, redox conditions and sedimentation rate.

Accurate and quantitative numerical modeling of phase behavior and speciation of gas-water-rock systems is crucial for fluid and rock evolution analysis, and important in scientific research and engineering applications. In our previous work, mutual solubility models of series gases and brine have been developed for wide temperature, pressure and composition ranges. The gas components included CO2, CH4, H2S, N2 and O2. The existing experimental data can be reproduced accurately. In this paper, the models are extended to include water-rock interactions by means of a full coupling with the open-source software package PHREEQC. With the new coupled model, the solubility of gases and various minerals can be correctly and reliably reproduced. The proposed numerical framework is properly implemented and it can be applied in different scenarios of gas-water-rock interactions. Three practical applications have been investigated: calculation of uranium in situ leaching, CO2 geological storage and natural gas souring are provided in the paper. The application cases have additionally proven the stability and reliability of the proposed model.

The Early Jurassic Jenkyns Event (similar to 183 Ma) represents a major environment perturbation event, characterized by the negative carbon isotope excursion during the early Toarcian. Reconstruction of redox conditions, especially in the mega-lakes, across the Jenkyns Event is of significance to understand the biogeochemical dynamics on land at the time. Here, we report iron speciation and trace metal data from the two drill cores (LQ104X and X3 wells) with different depositional environments in the lacustrine Sichuan Basin of SW China. Results show that the water column in the Sichuan Basin experienced a significant shift of redox conditions in the Toarcian. Frequent development of anoxic-ferruginous conditions interspersed with significant euxinic episodes across the Jenkyns Event. Conversely, during the pre/post-Jenkyns Event interval, dominantly oxic conditions, with shortlived anoxic-ferruginous or euxinic conditions, developed in the water column of the Sichuan Basin. We then proposed three possible mechanisms interdependent in nature that could have induced the water-column redox variability in Toarcian lakes: (1) lake stratifications, (2) enhanced methane release from the lake floor under low sulfate conditions that exhausted bottom water oxygen, and (3) lake eutrophication. We further anticipated that a close link between redox shift and ecological stress in the Sichuan Basin across the Jenkyns Event.

Increasing cases have indicated that oceanic anoxic events (OAEs) appear to have records in terrestrial sediments, which provide valuably high-resolution materials for the debated and challenging issues of OAEs. However, the current works are preliminary and need more geological analyses to test. Here we present a case study in the Lower Jurassic Da'anzhai Member of the Toarcian (ca. 180 Ma) Sichuan Basin, SW China. The petrology and sedimentary facies of the Da'anzhai Member were used to reconstruct the relative water-level fluctuations in the Sichuan Basin, which are revealed to be consistent with coeval changes in global sea levels. The Da'anzhai Member was deposited during a period of lake shallowing with enhanced salinities corroborated by the Sr/Ba and S/TOC ratios, when sea level was generally high after global transgression. During the lake shallowing, there were four complete secondary lacustrine deepening-shallowing cycles over shorter time-scales. The total organic carbon contents and organic carbon isotopic stratigraphy show there was a basin wide terrestrial response to the T-OAE as recorded by the Da'anzhai Member. The enrichment factors of Mo relative to PAAS (Mo-EF) and C-org/P values imply a dysoxic redox condition. The terrestrial response of OAEs is likely caused by changes in hydrological conditions, which were related to the global warming triggered by the Karoo-Ferrar Large Igneous Province. The associated organic carbon accumulation mechanism is a combined effect of elevated primary productivity and oxygen-depleted preservation conditions. Our data suggest that OAEs do have terrestrial response and induce organic carbon accumulation, but the mechanisms are still not much clear and need further studies.

The southern Junggar Basin in NW China is a world‐class location for the study of oil and gas seeps, with widely distributed, highly variable oil and gas seeps including gaseous mud volcanoes, liquid oil seeps, and solid bitumen deposits. However, the sources and origins of these seeps are poorly understood, as there are many potential source sequences of Permian to Paleogene age. The uncertainty surrounding the seeps means that it has not been possible to address their significance for oil and gas exploration in the area, and they are not understood in the context of the tectono‐sedimentary evolution of the basin within the piedmont region of the northern Tian Shan Mountains (in the eastern part of the Central Asian Orogenic Belt, CAOB). In the present study, these issues were addressed using combined geological and geochemical methods. Results show that there are five main types of seeps in the region from west to east. Type A seeps originate from Jurassic source rocks and are best represented by the A'erqingou mud volcano. Type B seeps originate mainly from Paleogene source rocks but also contain a Jurassic‐sourced component; they are best represented by the Dushanzi mud volcano. Type C seeps originate from a Cretaceous source and are best represented by the South Anjihai and Horgos oil sands. Type D seeps originate mainly from Jurassic source rocks but also contain a Triassic‐sourced component; they are best represented by the Qigu oil seep. Type E seeps originate from Permian source rocks and are best represented by the Dalongkou bituminous deposit. The primary controls on seep distribution are both sedimentological (deposition of source rock) and tectonic (faulting). The position and burial history of sedimentary centres controlled the distribution and maturation of source rocks. Tectonic faults provided migration pathways and traps for the oil and gas. The results of this study will help to reduce uncertainty during exploration for oil and gas in the area. The findings also have general implications for petroleum systems and exploration in the piedmont areas of foreland basins worldwide.

走滑断层判识及其油气成藏效应是当前构造地质学与石油地质学研究的热点.为进一步认识准噶尔盆地西北缘地区的控藏断层大侏罗沟走滑断层,对其进行了野外露头观察和地震剖面解释,以进一步明确其构造属性与边界,在此基础上,结合油层分布与原油性质及地球化学特征分析,讨论了其成藏效应.结果表明,大侏罗沟断层走滑特征明显,西端野外露头上断线平直、断面陡立、发育水平擦痕,东端地震剖面平面上发育“马尾状构造”、剖面上发育“花状构造”.据此重新限定了断层的边界,西以达尔布特断层为界,东以达探1井为界,全长约80 km.大侏罗沟走滑断层对油气兼具横向和纵向输导效应,使得油气藏在平面上沿断层被动盘富集,纵向上呈“串珠状”分布,这可能是这类走滑断层所具有的普遍特征.据此,研究区一系列走滑断层的被动盘在下步勘探中值得重点关注.

Giant vein-type bitumen deposits in the Wuerhe region within the northwestern Junggar Basin of NW China are representative examples of similar bitumen deposits that are found in a number of other locations in both China and elsewhere. These deposits can provide information on regional tectonics as well as insights into hydrocarbon and bitumen exploration, but the origin of the deposits remains unclear. This study focuses on determining the origin of the Wuerhe bitumen deposit using field, petrological, and geochemical data. Results show that the bitumen veins are generally hosted by shallow high-angle fault systems located within the nose of the Wuerhe fault-fold. The bitumen is of low maturity and has an organic origin, having formed by secondary alteration (most likely biodegradation) of crude oil sourced from the lower Permian Fengcheng Formation (P(1)f). The bitumen contains high concentrations of beta-carotane and gammacerane, low concentrations of Ts and diasteranes, and comprises (in ascending order of concentration) C-20-C-21-C-23 tricyclic terpanes and C-27-C-28-C-29 regular steranes. The bitumen was most likely formed during the Early Cretaceous under the control of faults. A fault-controlled model is presented for hydrocarbon migration and accumulation and the subsequent formation of this bitumen within the northwestern Junggar Basin. This model suggests that future hydrocarbon exploration should focus on the cores of fault-fold noses and areas of minor-fold nose near deep-seated fault zones, especially where these areas correspond to potential moderate- to shallow-depth Jurassic-Cretaceous reservoirs. The new model should be able to guide exploration in other basins with similar tectonic settings of this study, i.e., superimposed thrusting, compression, and transtension.

The Junggar Basin of NW China is representative in containing oil and gas seeps worldwide as there are a wide variety of oil and gas seeps over a large area. However, the genesis of these seeps remains poorly known, limiting the understanding of their implications for petroluem geology and hydrocarbon exploration. Here, we investigate 26 samples of oil and gas seeps from nine outcrops within five areas along the margins of the Junggar Basin to determine the geochemical characteristics of the hydrocarbons, constrain their genesis, and discuss future exploration strategies. Results indicate one type of gas seeps and five types of oil seeps. The gas seeps are derived from low-maturity Jurassic source rocks and occur in the Wusu and Dushanzi areas in the western segment of the southern basin. Type 1 oil seeps, sourced from lower Permian rocks (P1f), occur on the northwestern margin. Type 2 oil seeps, derived from middle Permian source rocks (P2l/P2p), occur on the eastern segment of the southern margin and eastern margin of the Junggar Basin. Type 3 oil seeps, with Jurassic source rocks, occur in the Qigu area in the middle segment of the southern basin. Type 4 oil seeps, with Cretaceous source rocks, occur in the Anjihai and Huoerguosi areas within the middle segment of the southern basin. Type 5 oil seeps mainly have Paleogene source rocks with a minor contribution from Jurassic rocks and occur in the Wusu and Dushanzi areas in the western segment of the southern basin with the single-type gas seeps. These results indicate the presence of lacustrine hybrid petroleum systems within the Junggar Basin with complex oil and gas sources and migration-accumulation. Six potential areas along the basin margin were proposed for exploration in the future.