Subsurface lithological distribution is essential for extrapolating geological information from core to block or basin scales. Given the limited availability of core data, there is a critical need to develop a reliable method for establishing robust correlations between logging curves and lithologies in cores, thereby maximizing the value of large historical logging data. Here, we propose a novel attention-based convolutional neural network (ATT-CNN), which employs a 1D-CNN to transform six types of logging curves into high-dimensional feature space at each depth, and applies an attention mechanism to the 1D-CNN outputs along both the depth and feature dimensions. The architecture is designed to mimic human perceptual processing for lithology identification, leveraging curve combination, thresholding, and local pattern recognition within this enriched and high-dimensional feature representation. In addtion, the study employs wavelet-based preprocessing on logging curves to eliminate the impact of compaction-induced data drift on model generalization-an issue rarely considered in prior studies. The result showes that: (1) The proposed ATT-CNN model demonstrates superior performance over benchmark models-the bidirectional gated recurrent unit (BiGRU) and an ensemble of machine learning models (En-ML)-across all evaluation metrics; (2)Wavelet-based preprocessing enhances the generalization capability of both ATT-CNN and BiGRU, yielding higher metric scores and improved predictions, particularly in shallow-depth intervals; (3) For blind wells, the ATT-CNN outperforms BiGRU and En-ML in both accuracy and its ability to capture lithological variations even from low-amplitude curve deviations. The integration of ATT-CNN with wavelet-based preprocessing demonstrates significant potential for accurately characterizing subsurface lithological distribution, then provides critical support for key petroleum geology workflows, including provenance analysis, sedimentary facies mapping, and reservoir property prediction.

The Toarcian Oceanic Anoxic Event (T-OAE, or Jenkyns Event, similar to 183 Ma) was a significant hyperthermal event that might have led to global carbon-cycle disruption, driven by a massive increase in isotopically light carbon emission into Earth's surface reservoirs. Remarkable paleoceanographic change and paleoenvironmental perturbations during the T-OAE are well recognized in many sedimentary basins. However, the spatio-temporal evolution of oceanic salinity during this time interval remains poorly constrained, which hampers our understanding of the hydrological condition of aqueous system in critical area. Here, high-resolution B/Ga analyses were performed on two typical sections (i.e. lagoonal Biluocuo section and shelfal Suobucha section) from distinct sedimentary facies in the Qiangtang Basin to trace Toarcian salinity variations. This study provides the first record of stratigraphic variations in bulk sediment B/Ga ratios during the early Toarcian from the eastern Tethyan Ocean. The B/Ga ratios indicate that the lagoonal area was characterized by prevalent hypersaline conditions, while the shelf area experienced freshwater to normal marine conditions. Pre-T-OAE trends suggest increasing shelf salinity and decreasing lagoonal salinity likely orchestrated by eustatic rise. A coeval decline in B/Ga ratios within the lagoonal and shelfal sections at the onset of the T-OAE reveals a progressive seawater freshening at this time. This basin-scale salinity decrease during the T-OAE is attributed to a climate-driven shift in regional hydrology. Global warming-induced intensification of hydrological cycle led to increased precipitation and runoff, reducing surface water salinity in the Tethys realm through elevated riverine freshwater input. This study advances our understanding of the spatial extent and scale of freshwater perturbations and provides new salinity evidence for an intensified hydrological cycle in response to global warming during the T-OAE.

Gas hydrate accumulations in high-altitude permafrost settings remain notoriously difficult to characterize seismically, yet they hold significant resource potential This study addresses key technical challenges in seismic exploration for gas hydrates in the permafrost of the Tso Co area, Qiangtang Basin, Tibetan Plateau, including low signal-to-noise ratio, complex static corrections, and difficult structural imaging. An integrated acquisition, processing, and interpretation workflow was developed to provide a high-precision seismic detection system suited to plateau permafrost conditions. A wide-line high-density geometry, combined with a low-frequency vibrator source with a sweep frequency of 1.5–96 Hz and point-receiver technology, enhanced low-frequency penetration and raw-data fidelity. Data processing used pseudo-three-dimensional wide-line tomographic static correction and global-optimization residual static correction to resolve high-frequency static distortions through iterative refinement. A multi-domain, stepwise, amplitude-preserving denoising workflow effectively suppressed high-energy noise, including surface waves and linear interference. Refined velocity modeling based on the Dip Moveout velocity field and finite-difference time migration achieved accurate positioning of complex structures. High-quality seismic profiles reveal alternating depression-uplift structural frameworks and major fault systems. The base of the permafrost layer shows a low-frequency, high-amplitude reflection of 10–35 Hz, with varying thickness (30–140 m). Ultra-low-frequency (5 Hz) relative impedance highlights permafrost distribution and indicates hydrate potential zones concentrated along faults, demonstrating structural control on gas migration. Low-frequency amplitude anomalies provide a reliable regional indicator for hydrate exploration.

The Quemocuo area in the Qiangtang Basin is a key prospect for permafrost gas hydrate exploration in China. This study investigates source-reservoir-caprock characteristics and their control on gas hydrate accumulation based on drilling results from wells QK-8 and QK-9, integrated with multiple analytical methods. Two high-quality marine source rocks with cumulative thickness similar to 1000 m exhibit TOC values of 0.74-2.5%, Type II2 kerogen, and vitrinite reflectance (Ro) of 1.37-2.94%, indicating high to over-mature thermal evolution primarily generating dry thermogenic methane. Gas logging shows hydrocarbon anomalies with a maximum desorbed gas content of 90 mL, confirming strong gas generation capacity. Although reservoir matrix properties are poor (porosity mostly <5%, permeability < 0.2 x 10(-3) mu m(2)), multi-phase tectonics and dissolution formed a secondary fracture-vug system. Permafrost conditions are favorable (thickness 100-120 m; geothermal gradient 4.5-4.7 degrees C/100 m), with extremely low permeability at high ice saturations, forming an effective multi-level seal together with thick mudstones. A key novel finding is the significant mixing of biogenic and thermogenic gases, with the biogenic component interpreted to originate from overlying Jurassic-Quaternary low-maturity strata, facilitated by late tectonic uplift and fault conduits. NW-trending faults connect deep thermogenic reservoirs and provide pathways for shallow biogenic gas migration. For the first time, this study establishes a region-specific composite accumulation model for the Qiangtang Basin, characterized by "lower generation and upper storage, fault-fracture conduit and permafrost sealing", which reveals fault-controlled migration, fracture-vug-controlled storage, permafrost-controlled sealing, and mixed gas enrichment under a high geothermal gradient.

The occurrence environment and fundamental characteristics of natural gas hydrate (NGH) in the permafrost regions of the Tibetan Plateau are highly complex. A significant barrier to advancements in NGH exploration within these areas is the lack of effective exploration methods. The Juhugeng mining area represents the sole location in China’s permafrost zone where NGH has been identified. In this study, we conducted a thermal released mercury (TRM) exploration experiment in the Juhugeng area, covering an area of 11.75 km2 with a sampling density of 16 points per square kilometer. Soil samples were collected to a depth of 60 cm, totaling 163 samples, which were analyzed for TRM using the XG-7Z Zeeman mercury analyzer. The experimental results indicate that high-value anomalies of TRM occur at the boundaries of NGH deposits, while lower values are observed directly above the hydrates, forming an annular anomaly pattern. The maximum value of TRM recorded was 127.37 ngg−1, with an average value of 32.59 ngg−1, and the lower limit of the anomaly was established at 39.24 ngg−1. By analyzing the spatial relationship between TRM anomalies and hydrocarbon anomalies, this study proposes a geogas migration mechanism for the formation of TRM anomalies. The anomalies are closely linked to NGH deposits, suggesting that TRM analysis is an effective auxiliary exploration technology for NGH in permafrost regions.

The Upper Triassic of the Qiangtang Basin is a key strata for oil and gas exploration in the Qinghai-Tibet Plateau. However, it has been controversial argued about the paleoenvironmental control mechanisms for the development of its source rocks. Based on the core samples from Well QK-9, this study reveals the climate and salinity on organic matter accumulation through comprehensive analysis of both organic geochemistry (TOC, Rock-Eval pyrolysis) and inorganic geochemistry (major and trace elements, pyrite content and isotopes). The results are: (1) The middle section consists of relatively good source rocks with relative high TOC (TOC = 0.70%–2.27%, with an average of 1.22%), while the upper and lower sections are poor source rocks for the low TOC (TOC = 0.07%–0.58%, with an average of 0.30%). (2) Paleoclimate (transitioning from humid to arid and back to humid) and paleosalinity (shifting from low to high and then to low) are the primary factors contributing to the vertical differentiation of source rocks. In contrast, the influence of oxidation conditions and biological productivity during that period was relatively minor. (3) In the upper and lower parts of the Bagong Formation, the accumulation of pyrite (with an average of 3.2%) is negatively correlated with low TOC (<0.3%), indicating that the sulfate-reducing bacteria (BSR) exacerbate the degradation of organic matter in a reducing environment. In the middle section, pyrite is less and the TOC increases significantly (with an average of 1.22%). This study reveals the negative correlation between pyrite accumulation and low TOC, challenging the traditional understanding that “reducing environments favor source rock formation” and proposing a “climate-salinity coupling” model for organic matter accumulation as a new theoretical basis for the evaluation of marine source rocks and oil and gas exploration in the complex tectonic background of the plateau.

In order to find out the impact of human activities on the hydrological environment of Muli permafrost area,Juhugeng mining area of Muli Coalfield with the most significant human activities in the alpine permafrost area was selected,and the river water of Datong River tributary system in the area was taken as the research object.Based on the spatial characteristics of hydrochemical composition,the research was carried out by using multiple isotopes such as hydrogen,oxygen,carbon,nitrogen,sulfur and strontium.The results show that:(1)The supra-permafrost water is the main supply source of the river water.Human activities such as coal mining and natural gas hydrate drilling destroy the original frozen soil structure and increase the contribution proportion of the supra-permafrost water to river water;(2)The increase of the concentration of main dissolved nutrients(SO42-,NO3-and DOC)in river water is due to the influence of human activities:sulfur and oxygen isotopes reveal that large-scale open-pit mining in coal mine promotes reduced sulfur oxidation,which is the main reason for the increase of SO42-in the supra-permafrost water and river water;Nitrogen and oxygen isotopes show that the high concentration of NO3-in the river comes from livestock manure of free range grazing;DOC mainly comes from soil organic matter produced by plant degradation in alpine meadow,and there are strong microbial activities in the river water in the source area;(3)Except for H2CO3 weathering carbonate rocks,the weathering of carbonate rock and silicate rock participated by sulfuric acid is enhanced under the influence of human activities and coal mining,which further affects the carbon sink of regional rock weathering.The research results provide research ideas for understanding the evolution of hydrological environment in Alpine permafrost area under the influence of human activities,and provide scientific basis for ecological environment protection in Alpine permafrost area.

The project of geological survey of unconventional oil and gas was organized by the Oil and Gas Survey of the China Geological Survey. And a series of projects were carried out in this project, including geological survey of coal bed methane in Jixi Basin of Heilongjiang Province, the geological survey of oil shale in Songliao Basin and its surrounding areas, the in-situ test production of oil sands in the western slope of Songliao Basin, the geological survey of continental natural gas hydrate, the construction of the Muli natural gas hydrate field observation station in Qilian Mountains, the geological survey of helium in Guanzhong area of Shanxi Province and national survey of unconventional oil and gas resources, and a large quantity of basic data were acquired. Besides, a series of breakthrough and important progress have been achieved in well Heijidi-1, well Heijidi-3 and well Heijidi-4, and the potential of unconventional oil and gas resources in China has been known preliminarily, such as oil shale, oil sands, continental natural gas hydrate, helium, and coal bed methane in Jixi Basin. The project has an important impact in the fields of coalbed methane, oil shale, helium, etc., which has boosted confidence in unconventional oil and gas exploration and development, and promoted the deep integration of scientific and technological innovation and geological survey, and furthered the development of unconventional oil and gas discipline.

Wetlands are an important source of atmospheric methane (CH4) and are sensitive to global climate change. Alpine swamp meadows, accounting for similar to 50% of the natural wetlands on the Qinghai-Tibet Plateau, were considered one of the most important ecosystems. Methanogens are important functional microbes that perform the methane producing process. However, the response of methanogenic community and the main pathways of CH4 production to temperature rise remains unknown in alpine swamp meadow at different water level in permafrost wetlands. In this study, we investigated the response of soil CH4 production and the shift of methanogenic community to temperature rise in the alpine swamp meadow soil samples with different water levels collected from the Qinghai-Tibet Plateau through anaerobic incubation at 5 degrees C, 15 degrees C and 25 degrees C. The results showed that the CH4 contents increased with increasing incubation temperature, and were 5-10 times higher at the high water level sites (GHM1 and GHM2) than that at the low water level site (GHM3). For the high water level sites (GHM1 and GHM2), the change of incubation temperatures had little effect on the methanogenic community structure. Methanotrichaceae (32.44-65.46%), Methanobacteriaceae (19.30-58.86%) and Methanosarcinaceae (3.22-21.24%) were the dominant methanogen groups, with the abundance of Methanotrichaceae and Methanosarcinaceae having a significant positive correlation with CH4 production (p < 0.01). For the low water level site (GHM3), the methanogenic community structure changed greatly at 25 degrees C. The Methanobacteriaceae (59.65-77.33%) was the dominant methanogen group at 5 degrees C and 15 degrees C; In contrast, the Methanosarcinaceae (69.29%) dominated at 25 degrees C, and its abundance showed a significant positive correlation with CH4 production (p < 0.05). Collectively, these findings enhance the understanding of methanogenic community structures and CH4 production in permafrost wetlands with different water levels during the warming process.

To reduce deforestation and ensure energy security for socioeconomic advancements, Rwanda must find alter-natives to wood fuel. Widely developed metasedimentary mudstones gradually became a petroleum survey object due to the progress of petroleum exploration theories and practices in the Mesoproterozoic strata all over the world. In this study, extensive field and experimental work was conducted to explore the organic features of the Mesoproterozoic strata and their relationship with the geological background, which is important for a petroleum survey of such strata. The results show that (1) the Mesoproterozoic samples have low total organic carbon (TOC) and S1+S2 and (2) except for the high degree of thermal maturity (Ro ranging from 3.71 to 3.82, avg. 3.77), the low TOC is mainly caused by the hypoxia degree and dissolution of terrigenous clastic materials in shallow water environments related to the fluvial delta. Hence, the Gikoro and Pindura groups should be paid more attention in Northwestern Rwanda (offshore direction in paleography) in subsequent exploration work for their thicker mudstones.

In order to determine the significant role of gas hydrate in seasonal wetland methane emission at the drilling-affected permafrost, the carbon isotopic monthly field monitoring of methane (CH4), as well as carbon dioxide (CO2), emitted from near-surface soil and a gas hydrate drilling well (DK-8) was conducted in the Muli permafrost of the Qinghai-Tibet Plateau. The methane source effused from the well DK-8 was calculated as −25.9 ± 1.4‰ and −26.5 ± 0.5‰, respectively, by the Keeling and Miller Tans plots, with the carbon isotope fractionation (εC) between CO2 and CH4 from −25.3‰ to −32.1‰. The carbon isotopic signatures are indicative of thermogenic origin associated with gas hydrate dissociation. The near-surface soil-emitted methane has δ13CCH4 values between −52.0 ± 1.2‰ and −43.2 ± 1.8‰ with the heaviest in December and the lightest in July. Further, the εC values of near-surface soil-emitted gases were between 28.6‰ and 47.9‰, significantly correlated with the δ13CCH4 values. The linear correlation between εC and δ13CCH4 values indicated binary end-member of microbial and thermogenic sources control the seasonal variation of wetland methane emission. The thermogenically derived methane was identified as the dominant methane source in autumn and winter, compared with the increasing contribution of microbially derived methane in spring and summer. The finding provides reliable evidence for gas hydrate release on the seasonal wetland methane emission in the Muli permafrost affected by drilling activities. The combined application of εC and δ13CCH4 to distinguish thermogenic from biogenic methane is well established and powerful in complex environments, which can provide an improved constraint on source apportionment for wetland emitted methane in the permafrost of the Qinghai-Tibet Plateau.

An active layer detachment slide (ALDS) in the interior portion of the Qinghai–Tibet Plateau (QTP) was investigated within 2 days of its formation on September 21, 2018. The ALDS developed on a relatively gentle slope (4.8° to 9°) at an elevation of 4,850 m above sea level (asl) and was about 145 m long and 45 m wide, with a headscarp 2.2–2.5 m high. Analyses of meteorological data and soil temperatures indicated that it was probably triggered by a record thaw depth which intersected a layer with high ice content at the base of the active layer and in the top of the permafrost. Based on the time window, the minimum downslope velocity of the main slide mass was about 20 m/h which is higher than previously reported values. The ALDS ran into the embankment of the Qinghai–Tibet Railway (QTR) but did not damage the railbed. However, extensive rehabilitation of the slope was needed subsequent to the failure to clear the slide mass and as minor headscarp recession and thaw settlement continued on the slope. In this work, we describe this feature and the most likely mechanisms of development.

Wetland methane emissions in the permafrost regions of the Qinghai-Tibet Plateau is more sensitive to climate warming and can result in a positive climate feedback. Natural gas hydrate, as a potential methane source, may play a pivotal role in wetland methane emission in the permafrost regions. However, it was lacking of evidence. To determine the role of gas hydrate release in wetland methane emission, the two-year field monitoring of methane emitted from a hydrate drilling well, in near-surface soil free gas and low-level air was conducted at a typical gas hydrate reservior in the Qilian Mountains permafrost. The carbon isotope fractionation between CO 2 and CH 4 (ε C ) associated with carbon isotopic composition of methane (δ 13 C CH4 ) is used as a good tracer to identify methane sources of thermogenic origin or of microbial origin. The monitoring results of the gas hydrate drilling well DK-8 indicated a notable release of the deep gas hydrates occurred in April- May and resulted in the increase of methane content in low-level air. The significance of gas hydrate release in the permafrost region on local wetland methane emission as well as low-level air methane was confirmed by the seasonal variation of methane source of near-surface soil fluxes and low-level air. The thermogenically derived methane were identified as the dominant methane source in autumn and winter compared with increasing contribution of microbially derived methane in summer. The carbon isotopic signatures of tracing methane sources can provide more reliable evidence for gas hydrate release and its effect on the wetland methane emission in the Qilian Mountains permafrost.

1 研究目的(Objective) 尼玛盆地构造上位于班公湖—怒江缝合带中部,是发育在侏罗系—白垩系海相地层之上的古近系陆相裂谷盆地,北接羌塘地块,南邻冈底斯地块,近东西向展布,面积约3000 km2.本次研究目的是初步查明尼玛盆地东部冻土发育特征,调查盆地东部古近系地层层序,获取古近系烃源岩、储盖层等关键评价参数,进一步评价盆地油气资源潜力.

The Qinghai-Tibet Plateau (also referred to as the Plateau) is the largest area bearing alpine permafrost region in the world and thus is endowed with great formation conditions and prospecting potential of natural gas hydrates (NGH). Up to now, one NGH accumulation, two inferred NGH accumulations, and a series of NGH-related anomalous indicators have been discovered in the Plateau, with NGH resources predicted to be up to 8.88×1012 m3. The NGH in the Qinghai-Tibet Plateau have complex gas components and are dominated by deep thermogenic gas. They occur in the Permian-Jurassic strata and are subject to thin permafrost and sensitive to environment. Furthermore, they are distinctly different from the NGH in the high-latitude permafrost in the arctic regions and are more different from marine NGH. The formation of the NGH in the Plateau obviously couples with the uplift and permafrost evolution of the Plateau in spatial-temporal terms. The permafrost and NGH in the Qilian Mountains and the main body of the Qinghai-Tibet Plateau possibly formed during 2.0–1.28 Ma BP and about 0.8 Ma BP, respectively. Under the context of global warming, the permafrost in the Qinghai-Tibet Plateau is continually degrading, which will lead to the changes in the stability of NGH. Therefore, The NGH of the Qinghai-Tibet Plateau can not be ignored in the study of the global climate change and ecological environment.

针对QK-3井取得的曲色组泥页岩、油页岩以及液态油苗进行了有机地球化学特征分析,探讨曲色组烃源岩与液态油苗的亲缘性.研究表明:QK-3井曲色组泥岩及油页岩达一般—好烃源岩标准,有机质类型多为Ⅰ及Ⅱ1型,处于成熟阶段;油页岩、油苗样品生物标志物对比表明,二者形成环境及成熟度特征较为接近,具有很好的可比性,在曲色组中发现的油苗与该组烃源岩有着较好的亲缘关系,油苗源于曲色组油页岩等烃源岩.综合烃源岩有机地球化学特征及曲色组分布范围与沉积厚度认为,下侏罗统曲色组泥质烃源岩的生烃能力属于较好级别,是研究区内最主要的烃源岩,具有较好的勘探潜力.

China has been attaching great importance to research on natural gas hydrate resources. Since the mid-1990s, China has experienced three stages of resource prediction, investigation, and test production. Until now, five hydrate accumulations have been discovered by drilling and sampling in the Shenhu, Dongsha, Qiongdongnan Basins, and offshore Taiwan of the South China Sea and in the Muli area of Qilian Mountain, and seven hydrates have been inferred by various indicators, including geology, geophysics and geochemistry in the South China Sea, the East China Sea, and the Qinghai-Tibet Plateau. According to the hydrate stability zone, the natural gas hydrate resources in the South China Sea are estimated to be 64.6 x 10(12) m(3), those in the East China Sea are similar to 28.5 x 10(12) m(3), and those in the terrestrial permafrost are similar to 38 x 10(12) m(3). The total amount of the natural gas hydrates in China reaches up to 131.1 x 10(12) m(3), which is twice the amount of China's conventional natural gas resources. China has successfully conducted the five field test production of gas hydrates in the Muli permafrost region of Qilian Mountain and in Shenhu area of the South China Sea since 2011, in particular first using horizontal well technologies to exploit hydrates that occurred in the fine-grained reservoirs. It is expected that commercial production from the hydrate reservoir will come true in the 2030s.

基于天然气水合物钻探试验井QK-8井的调查成果,以雀莫错地区发现的高烃类气体显示为线索,从影响高山冻土区天然气水合物成藏的关键地质因素出发,系统分析了影响天然气水合物成藏的冻土厚度、烃源岩特征、储集空间、疏导系统、矿物特征及盖层条件等地质因素,明确了该区天然气水合物成藏潜力.结果显示:雀莫错地区冻土厚度较大(约100 m);上三叠统主力烃源岩整体表现为有机质丰度高,为Ⅱ2型干酪根,成熟度较高(Ro为1.3％ ～1.5％);储集空间以缝洞型储层为主,裂隙、孔隙型次之;具备有效的运移通道和良好的区域盖层,同时多层段发育方解石和黄铁矿等天然气水合物伴生矿物.综合分析认为,雀莫错地区具有一定的天然气水合物成藏潜力,是下一步天然气水合物含油气系统综合能源资源调查的主要方向.

In this study, systematic soil methane cycle geochemical monitoring was carried out in a typical gas hydrate region in the Qinghai-Tibet Plateau. Soil gas samples were collected for hydrocarbon components and carbon isotope analysis. Meanwhile, soil-methane fluxes from the upper active layer (20–30 cm) were monitored during six months of one year. The results of this research provide evidence of a new source of methane emission from wetland soils in permafrost regions: gas hydrate release. Sites with large methane emissions were found using flux monitoring, the characteristics of thermogenic methane were identified using carbon isotope tracing, and the relationship between emission by soils and effusion from gas hydrates was determined through correlation analyses of soil-adsorbed hydrocarbons. Seasonal variation of methane emissions are also discussed by considering the emission of bacterial methane, thermogenic methane, and the absorption of methane from the soil active layer. These comprehensive findings provide valuable information for carbon cycle research of wetlands in permafrost regions.