The Cambrian System in the Tabei area underwent multiple phases of tectonic movement. The paleostructures have been significantly reconstructed, which makes geomorphological restoration very difficult. Previous studies in this area have mostly focused on traditional, single technical methods, resulting in limitations in the characterization of complex paleogeomorphology. For this reason, this paper proposes a new paleogeomorphology restoration method based on combining the shoreline trajectory method with the stratigraphic thickness method. First, the denudation volume at the end of the Late Cambrian sedimentation is calculated using the layer flattening method and the impression method, constrained by the double-sided restoration method. Then, on this basis, the tectonic uplift of the Xiaoerbulake sedimentary period is restored using the stratum thickness method. Finally, the relationship between accommodation space and sediment supply rate is used to derive the law of shoreline migration. Shoreline migration indicates the direction of tectonic movement and identifies the period of tectonic uplift during the Xiaoerbulake sedimentary period. The results indicate that the Xiaoerbulake Formation's sedimentary period in the early Cambrian was the main uplift period. The amount of tectonic uplift increased in a northeasterly direction, with the maximum located in the northern part of the Yuqi-6 Well. This controls the direction in which the Xiaoerbulake sediments prograde and the formation of the platform-margin. The Xiaoerbulake sedimentary period experienced two phases of uplift and three sedimentary stages, causing the northern sedimentary line to move eastward.

This study investigates the resonant interactions between artificial Extremely Low Frequency and Very Low Frequency waves, generated via modulated ionospheric heating, and energetic electrons in Earth's radiation belts. Using test particle simulations, we analyze how discrete multi‐frequency waves (with characteristics derived from DEMETER observations) scatter electrons, examining the dependence on wave frequency, electron energy, and equatorial pitch angle. Key findings reveal that higher‐frequency waves resonate with a broader range of electrons but at higher magnetic latitudes, while lower‐frequency waves are more effective for pitch‐angle scattering. Multi‐frequency waves, even with modest amplitudes (e.g., 10 pT per frequency), significantly enhance diffusion rates, particularly for 100–300 keV electrons near the loss cone, achieving bounce‐averaged pitch‐angle diffusion coefficients of ∼10 −4 /s. The results demonstrate strong energy dependence, with sub‐MeV electrons exhibiting higher scattering rates than MeV‐range populations. Diffusion coefficients generally increase with equatorial pitch angle but exhibit non‐monotonic fluctuations due to the detuning of lower‐frequency components. These findings highlight the potential use of ionospheric heating to artificially modulate radiation belt dynamics and suggest that multi‐frequency wave generation could optimize electron scattering efficiency. This study bridges observational data with theoretical modeling, providing insights for future experiments aimed at controlled electron precipitation.

Identification of reservoir types in deep carbonates has always been a great challenge due to complex logging responses caused by the heterogeneous scale and distribution of storage spaces. Traditional cross-plot analysis and empirical formula methods for identifying reservoir types using geophysical logging data have high uncertainty and low efficiency, which cannot accurately reflect the nonlinear relationship between reservoir types and logging data. Recently, the kernel Fisher discriminant analysis (KFD), a kernel-based machine learning technique, attracts attention in many fields because of its strong nonlinear processing ability. However, the overall performance of KFD model may be limited as a single kernel function cannot simultaneously extrapolate and interpolate well, especially for highly complex data cases. To address this issue, in this study, a mixed kernel Fisher discriminant analysis (MKFD) model was established and applied to identify reservoir types of the deep Sinian carbonates in central Sichuan Basin, China. The MKFD model was trained and tested with 453 datasets from 7 coring wells, utilizing GR, CAL, DEN, AC, CNL and RT logs as input variables. The particle swarm optimization (PSO) was adopted for hyper-parameter optimization of MKFD model. To evaluate the model performance, prediction results of MKFD were compared with those of basic-kernel based KFD, RF and SVM models. Subsequently, the built MKFD model was applied in a blind well test, and a variable importance analysis was conducted. The comparison and blind test results demonstrated that MKFD outperformed traditional KFD, RF and SVM in the identification of reservoir types, which provided higher accuracy and stronger generalization. The MKFD can therefore be a reliable method for identifying reservoir types of deep carbonates.

Using the data from the first satellite of the Republic of China (ROCSAT-1) obtained during high-solar-activity periods (2000–2003), the distributions of plasma density enhancement (plasma blobs) with local time, season and longitude were investigated. Some new features of plasma blobs can be concluded: (a) The distribution of plasma blobs shows remarkable seasonal and interhemispheric asymmetries, with the higher occurrence in June solstice months and in the winter hemisphere. (b) The occurrence of plasma blobs displays longitude dependence, more in the −180~−90°E, −60~0°E and 90~180°E longitude regions. (c) The seasonal and interhemispheric asymmetries of plasma blobs also depend on the longitude. Meridional wind plays an important role in the formation and evolution of low-latitude plasma blobs. Inclination and declination may control the longitudinal distribution of plasma blobs.

Siliceous minerals of the Dengying Formation in the Gaoshiti–Moxi area in the central Sichuan Basin exhibit four types of quartz crystals (cryptocrystalline quartz, chalcedony, microcrystalline quartz, and megacrystalline quartz) and three structural types: cryptocrystalline, microcrystalline, and mosaic (laminated mosaic, window-hole interrupted mosaic, and arc-laminated mosaic). Siliceous minerals have a great influence on the storage performance of the reservoirs in the Dengying Formation. According to the petrophysical parameters of the Dengying Formation and porosity intersection diagrams, the siliceous dolomite and the reservoirs have low impedance characteristics, which makes it difficult to distinguish between them and leads to difficulties in the characterization and prediction of the reservoirs. The transverse wave velocity is favorable for reservoir characterization. Currently, the main method used to estimate the transverse wave velocity is petrophysical modeling, which establishes a relationship between the elastic and physical parameters of the reservoir. In this paper, the siliceous minerals in the dolomite in the study area are regarded as solid inclusions, and the calculation method of the rock matrix modulus is improved by using solid replacement. Then, an improved petrophysical model is constructed by combining the KT (Kuster–Toksöz) model, the DEM (Discrete Element Method) model, the Gassmann equation, and the Wood equation. The transverse wave velocity is estimated using the improved model under the constraint of the longitudinal wave velocity. The shapes of the transverse wave velocity curves obtained by the improved model and the deviations from the measured velocities are significantly better than those of the Xu–Payne model and other models. The results show that the improved model can effectively estimate the transverse wave velocity of the reservoir in this area, which provides a basis for future reservoir predictions in this area.

Carbonate reservoirs in the Sinian Dengying Formation, central Sichuan Basin, are a hot spot for hydrocarbon exploration and development in deep and ultra-deep sequences in China. Multi-type and multi-scale natural fractures are widely seen in the Dengying reservoirs, and of significant impacts on the seepage flow pattern and well productivity. In this study, the genetic types and developmental characteristics of natural fractures in the fourth member of Dengying Formation (Deng 4 Member), Gaoshiti-Moxi area, are clarified utilizing the cores, thin sections, image logs, experimental tests and production testing data. Major geological factors controlling the development of natural fractures are used to analyze the impact of natural fractures on well productivity. Results show that natural fractures in the Deng 4 Member reservoirs in Gaoshiti-Moxi area are mainly of tectonic and diagenetic types. The tectonic fractures can be divided into shear fractures and tension fractures, and the diagenetic fractures are mainly bedding fractures and stylolites, among others. The shear fractures dominate the Deng 4 Member reservoirs, and are mainly of high-angle ones and striking in the NNW-SSE, nearly EW, NE-SW and nearly SN directions. Factors controlling the shear fracture effectiveness include the timing of fracture formation, cementation, dissolution, fracture occurrence and current in-situ stress. The shear fractures in NNW-SSE and nearly EW orientation are more effective than others. The development degree of shear fractures is closely related to the lithology, mechanical layer thickness and faults. The shear fractures are more highly developed in micritic dolomites, and their density decreases and scale enlarges along with the increasing thickness of mechanical layers. The shear fractures near the main strike-slip faults, in particular within the tip and superimposed part of faults, are better developed. The development degree and effectiveness of fractures jointly determine gas well productivity. The effective fractures in different occurrences and scales can form fracture network, and get relatively isolated pores interconnected, which greatly improves the seepage capacity of reservoirs and elevate well productivity. In the Deng 4 Member reservoirs of Gaoshiti-Moxi area, the shear fractures in NNW-SSE and nearly EW orientation are of stronger ability to enhance reservoir permeability, and make greater contribution to the improvement of well productivity.

河网水系是重要的地形特征要素,数字河网的提取则是DEM数据一个重要的应用方面,在此基础上进行水文信息参数计算,对于水文研究具有重要的意义.以九江市为研究区域,基于DEM数据,运用ArcGIS的水文分析模块对研究区进行小尺度的河网特征信息提取与分析.结果表明,基于DEM提取数字河网的精度和效率能够达到使用要求,河网密度等参数的计算结果能反映实际的情况,具有较高的可靠性,可进一步应用于水文研究.

Plasma irregularity in the equatorial and low-latitude ionosphere, which leads to ionospheric scintillation, can threaten the operation of radio-based communication and navigation systems. A method for forecasting scintillation activity is still pending. In this study, we examined the performance of ionospheric parameters, including the critical frequency (foF2), peak height of the F2-layer (hmF2), scale height (Hm) and virtual height (h’F), around local sunset from ground-based ionosonde observations, and also the characteristics of Equatorial Ionization Anomaly (EIA) derived from Gravity Recovery and Climate Experiment (GRACE) observations in equinoctial months (March–April and September–October) during high solar activities (2012–2013) at a low-latitude station at Sanya (18.3° N, 109.6° E; dip lat.: 12.8° N), China. Furthermore, the simplified linear growth rate of Rayleigh–Taylor (R–T) instability inferred from ionosonde measurements and EIA strength derived from GRACE observations were used to estimate the day-to-day occurrence of post-sunset scintillation. The results indicate that it is not adequate to determine whether scintillation in a low-latitude region would occur or not based on one ionospheric parameter around sunset. The simplified growth rate of R–T instability can be a good indicator for the day-to-day occurrence of scintillation, especially in combination with variations in EIA strength. An index including the growth rate and EIA variations for the prediction of the post-sunset occurrence of irregularity and scintillation is proposed; the overall prediction accuracy could be about 90%. Our results may provide useful information for the development of a forecasting model of the day-to-day variability of irregularities and scintillation in equatorial and low-latitude regions.

In this study,we present characteristics of post-sunset GHz scintillation occurrence and their correlations with ionospheric parameters derived from ionosonde observations in high solar activity years(2012-2013)of solar cycle 24 at Sanya(18.3°N,109.6°E;dip lat.:12.8°N),China.The analyzed data include the F2-layer's critical frequency(foF2),peak height(hmF2),and minimum virtual height(h'F),as well as the scale height around the F2-layer peak(Hm),and virtual height(h'F5)and true height(hF5)measured at 5 MHz.We have investigated relationships between the equinoctial asymmetry of these scintillations and these ionospheric parameters.In addition,we calculate the growth rates of Rayleigh-Taylor instability on the basis of the ionosonde measurements and theoretical models,respectively.We find that the equinoctial asymmetry of scintillation onset time is associated with the scale length of the vertical electron density gradient(L),which has been shown to affect the growth of Rayleigh-Taylor instability at the bottom of the F-layer.The seasonal variations of foF2,Hm and scale length of vertical electron density gradient appear to cause the seasonal variations of scintillation occurrence;the equinoctial asymmetry of scintillation occurrence rate over low latitudes appears to be related to background electron density and vertical drifts in the F-layer around time of sunset.Further study is required to explain the observed correlational weakness in low latitudes between scintillation strength,represented by the daily maximum S4,and daily maximum values of foF2,hmF2,h'F,Hm,and also the drifts.

Porosity, total organic carbon content, brittle mineral content, and gas content are now the primary references for classifying and evaluating marine shale gas reservoirs in China. Is there a more effective and appropriate reservoir classification scheme for deep marine shale? The Longmaxi Formation in Luzhou, southern Sichuan Basin, China, is the main object of study. Quantitative analysis and modeling using data from field emission scanning electron microscopy, nitrogen adsorption, and logging were used to characterize organic matter (OM) pore multi-scale development and reveal the relationship between OM pore and the high-quality reservoirs. Microscopic and macroscopic indications from OM pores show that a large number of OM pores were developed in high-quality reservoirs. OM surface porosity occupancy of the high-quality reservoir in the Luzhou area was more than 60%. OM porosity occupancy was more than 50%. The nitrogen adsorption–desorption hysteresis loops demonstrate the development of bottleneck and wedge-shaped OM pores. Characterization of multi-scale pore structure by box dimension, pore volume and specific surface area. It is found that the key to the formation of high-quality reservoirs was the massive development of OM mesopores in siliceous shale and the relatively homogeneity structure, which was conducive to the enrichment and migration of shale gas. Furthermore, the improved model decreased the relative error in predicting the OM porosity by about 32.5%. The use of OM porosity occupancy for high-quality reservoir classification was better, and the results were consistent with geological understanding. OM porosity occupancy showed that the area from Lunanxi to Luzhou to Rongchang to Jiangjin was the key exploration area for high-quality reservoirs in southern Sichuan. This study is expected to provide a new idea for OM pore modeling analysis and deep marine shale gas reservoir classification.

Organic matter (OM)-hosted pores are the primary pore type in the deep shale reservoirs of the Longmaxi Formation, in the Sichuan Basin, China, as well as the main locations for shale gas enrichment. However, the quantitative characteristics of OM pore space are not clear, and there is a lack of characterization methods. In this study, scanning electron microscopy (SEM), mercury intrusion porosimetry, low temperature gas adsorption, and logging data are all used to carry out multi-scale quantitative characterization of OM-hosted pores. The shape factor (F) model, fractal dimension model, and the OM porosity model are improved by combining them with mathematical morphology. The study primarily examines the effect of heterogeneity and the development of full scale pores in the OM pore space of the Luzhou area. The results show that (1) the ideal shape factor (F*) reflects the compaction degree of OM-hosted pores. From macropores to micropores, F* ranges from 0.61 to 0.93 as the shape gradually changes from flattened to round. (2) Shape factor and fractal dimension analyses revealed that the heterogeneity strength of the nanopore structure is mainly controlled by macropores. At the micro level and macro levels, the OM space shows lateral homogeneity and vertical heterogeneity. (3) Compared to the established method, the relative error of the improved model used in this study for predicting OM porosity was reduced by 19%. (4) Compaction and pore structure heterogeneity influence the formation of nanoscale pores in the Luzhou region and these factors also promote the development of mesopores and micropores, respectively. Furthermore, the OM porosities of the dominant shale reservoirs in Luzhou account for more than 50% of the overall porosity. This understanding will be of considerable benefit for evaluating deep shale reservoirs.

以江西省为研究区,基于区内85个气象台站1981-2010年的时间序列气温观测资料,对数据进行探索性分析.结合研究区的先验知识,分别采用反距离权重法、普通克里金法、基于数字高程模型(DEM)的多元线性回归插值法和梯度递减插值法进行空间插值,并通过交叉验证法对比分析了这些插值方法的精度.结果表明,基于DEM的插值方法精度均有一定程度的提高,且两种误差检验指标整体更小,优于传统方法.梯度递减插值法随月份变化平稳,插值结果能更精细地体现江西省气温的空间分布特征.

In this paper, characteristics of medium and small-scale ionospheric disturbances over Beijing were studied by ionosonde observation data. The cases of medium and small-scale ionospheric disturbances over Beijing on Nov.13, 2017 were analyzed using the rapid-run observation data of the PDI ionosonde. The results show that the V-shaped (or U-shaped) descending structure in the ionograms is an "explicit" feature of the medium-scale ionospheric disturbance. On the other hand, the small-scale ionospheric disturbances mainly occur at lower altitudes. They are not accompanied by distinct anomalous structures in the ionograms. The characteristics of the occurrence rate of medium-scale ionospheric disturbances over Beijing were presented by statistically studying the abnormal trace events in ionograms from 2010 to 2021. The median-scale ionospheric disturbance characterized by these abnormal traces is a mainly daytime phenomenon. Its occurrence rate is significantly higher in winter than those in other seasons. Furthermore, the occurrence rate is higher under low solar activities, which shows an inverse correlation with solar activity. The correlation with geomagnetic activity is still unclear.

The structural evolution and sedimentary differentiation of the Sichuan Basin in China are complex, with intricate reservoir pore structures that significantly impact shale gas production. This study examines the complexity and heterogeneity of the microscopic pore structures in the deep marine shale reservoir in the Longmaxi Formation. Pore structure characterization techniques are used to compare deep and shallow–medium marine shales, and siliceous and silty shales. The results reveal the factors influencing pore structure and their impact on exploration and development. The key points are as follows: (1) The pore structure of deep siliceous shale is the most complex due to its diverse range of pore development patterns, pore types, and sizes. (2) The box dimension of full pore size is about 1.52 for deep marine shale and 1.46 for shallow–medium shale. Organic matter (OM) content, the degree of pore development, and inorganic mineral content all correlate positively with the complexity of the pore structure in deep marine shale, which affects the formation of high-quality reservoirs. (3) Lateral heterogeneity of pore structures shows strong regional variations in the study area. Heterogeneity is more pronounced in the deep marine shale than in the medium and shallow shale formations. OM mesopores significantly influence the overall heterogeneity of the shale pore system. The deep marine shale reservoir is situated in an area with strong regional variations. The pore structure of high-quality reservoirs is more complex than those of shallow–medium marine shales, displaying notable heterogeneity. Pore structures with fractal dimension values close to that of the shallow–medium formations (box dimensions within 1.5) offer promising targets for the exploration and development of deep marine shale gas.

By using fast ionogram observations, we report the first simultaneous observations of ascending ion layers at equatorial and low latitudes. The ionosonde measurements at Sanya (18.3°N, 109.6°E; dip lat. 12.2°N) and Chumphon (10.7°N, 99.4°E; dip lat. 3.8°N) show that a high Es layer, which might contain metallic ions, was directly lifted upward from the local E region to F region bottomside at morning hours, in a pattern similar to the vertical drift of the F region background ionosphere driven by the daytime eastward electric field. A statistical analysis with Sanya ionosonde measurements shows that the low latitude ascending ion layer is not a rare phenomenon, with a maximum occurrence of 22% during equinox. The results indicate that at the latitudes far away from the magnetic equator, the local E region metallic ions could be directly brought into the F region with the ascending layer. It can be expected that fast ionogram measurements, which can easily capture the rapid evolution of the background ionosphere, will play an important role in studying the formation of some unexpected high altitude metallic layers.

利用我国覆盖高中纬到低纬5个台站第22-23太阳活动周(1995-2006)的foF2每日整点观测数据,分析研究了中国地区foF2的纬度变化、太阳活动变化、日变化、月变化、季节变化、半年变化、年变化和地磁活动变化等变化特性.结果表明:foF2随地理纬度变化,呈负相关关系,即纬度越低,其值越大;foF2与太阳活动F107有较强的正相关关系,太阳活动强度越大,foF2值也越大;foF2表现了较强的月变化和季节变化特征,结合日变化,在白天,foF2冬季大于夏季,表现出明显的"冬季异常",在夜晚,夏季大于冬季,"冬季异常"现象没有出现;地磁活动受太阳活动影响,而foF2无明显的地磁活动依赖;foF2呈现明显的半年变化特征,与季节变化交叉相关,表现为"半年异常",即两分点大于两至点.

The brittleness of shale reservoirs is of great significance for shale gas development. The brittleness index is the most intuitive parameter reflecting reservoir brittleness. The key exploration and development strata of shale gas in Pengshui area of southeastern Chongqing are Wufeng Formation of Upper Ordovician and Longmaxi Formation of Lower Silurian, and the high-quality shale reservoir is Wufeng–Long 1 section. The results show that the high brittleness grade of shale corresponds to low Poisson's ratio and high Young's modulus, but the relative distribution index of brittle minerals also affects brittleness. Through the analysis and calculation of brittle minerals and clay minerals in reservoir, the brittle index is calculated using rock physical parameters and mineral composition, and the advantages and disadvantages of the two are compared. Then a new formula for calculating brittleness index is obtained by combining rock physical parameters and mineral composition. Finally, the brittleness of high-quality shale reservoir in southeast of Chongqing area is evaluated comprehensively. Compared with the measured brittleness, the new formula has good effect. The average brittleness index of the Wufeng–Long 1 is more than 70% in Nanchuan area, China. The lateral distribution is stable and the fracturing conditions are good.

针对高石梯地区(灯影组四段)灯四段储层地震响应特征不明及前期识别的"宽波谷+'亮点'"地震模式适用性问题,在研究区背景地层地震反射特征分析的基础上,研究了储层地震响应差异的影响因素并建立了相应的正演模型,然后结合实际资料总结了灯四段储层的地震识别模式,最后分析了平面地震振幅属性所表征的储层特征.结果 表明,储层性质的相似性是储层地震响应多解性的重要来源;储层组合特征是储层地震响应差异性的成因依据;灯四段顶部储层地震响应主要为震顶波峰减弱或下拉,灯四2储层可通过上亚段中部"亮点"与底部波峰特征进行识别,灯四1储层主要识别依据为单独珠状反射;通过实际地震响应特征建立起了高石梯地区灯四段储层的5种地震成因识别模式,高石1井区中均方根振幅属性与储层厚度具有一定的对应关系,准确提取该属性能够为研究区储层的有效预测提供参考依据.

Abstract The zonal electric field and meridional wind are two major factors to affect the formation of both equatorial ionization anomaly (EIA) and plasma irregularities in equatorial and low‐latitude regions, the correlation between the EIA characteristics and the occurrence of both irregularities and the sequent scintillation is always concerned. In this study, we investigated the relationship between the day‐to‐day occurrence of scintillation based on ground‐based GPS observations at Sanya (18.3°N, 109.6°E; dip lat.: 12.8°N) and Hongkong (22.4°N, 114.2°E; dip lat.: 16.1°N), China, and day‐to‐day variations of EIA inferred from the Gravity Recovery and Climate Experiment observations in equinoctial months (March‐April and September‐October) during high solar activities (2012–2014). The results indicated that EIA strength can be linked with the day‐to‐day occurrence of post‐sunset irregularities and scintillation, and post‐sunset scintillation would be likely to occur as electron density above the EIA trough is low and EIA is strong. There are other key factors to affect the initiation and evolution of irregularities besides zonal electric field and meridional wind, such as seed perturbations or wave‐like structures. The day‐to‐day variations of electron density in EIA regions, EIA strength and EIA asymmetry were not well correlated quantitatively with the scintillation intensity representing by daily S4 maximum in low‐latitude region. These results can help us understand and predict the day‐to‐day variability of irregularities and scintillation in equatorial and low‐latitude regions.

Shale in the Wufeng Formation of the upper Ordovician and Longmaxi Formation of lower Silurian in the Sichuan Basin and its surrounding area is widespread. Shale gas resources are abundant. Shale gas in the Wufeng Formation and the Longmaxi Formation in the basin has been a major breakthrough. The basin margin transition zone in southeastern Chongqing is in an intense tectonic activity area, which is more complicated and special than the stable stratum in the basin. Therefore, it is necessary to put forward higher requirements for preservation conditions and enrichment pattern evaluation of shale gas. Therefore, in view of the complicated structural pattern of the basin margin transition zone in southeastern Chongqing, the preservation conditions and reservoir forming patterns are analyzed through structural evolution, uplift and denudation, fault development, structural styles, roof and floor conditions, and formation pressure. The results show that the main reason for the formation of normal pressure is the late uplift, denudation and fault development. The pressure coefficient from the basin to the outer layer is changed from overpressure to normal pressure, and structural transformation forms the preservation form of shale gas with narrow and steep residual anticline, wide residual syncline and residual slope. The preservation condition evaluation of normal shale gas should be based on structural factors such as structural evolution, structural style, uplift and denudation degree and fault development degree, with formation pressure coefficient as reference condition, combined with material basic conditions such as roof and floor conditions and formation thickness. The findings of this study can help for better understanding of the "sweet spot" prediction of normal pressure shale gas in complex structural area.