The tectonics of the Nansha trough-Northwest Palawan is important for understanding the origin and evolution of the South China Sea (SCS). Based on the analysis of geological and geophysical data in the southern margin of SCS, we suggest that the very thin crust of the Nansha trough may not be the remnant of the Proto South China Sea (PSCS), but may be an abandoned spreading center. As a result of a compressional event after the formation of the SCS, the thrusting structures developed very late on the Nansha trough and were not related to the opening of the SCS. The comparison between the extrusion of the Nansha trough and the Pagasa wedge in Northwest Palawan shows that the time of compressional termination in the east is earlier than in the west in the southern margin of the SCS. The ophiolite in South and Central Palawan was the product of its southern northward thrusting, indicating that the PSCS may subduct from south to north. It is suggested that the Southern Palawan ophiolite may derive from the oceanic crust of Neo-Tethys and the Central Palawan ophiolite may come from the PSCS. The subducted remnants of oceanic crust in different periods were finally overthrusted onto the island arc system. The Palawan ophiolite is the result of a long-term thrusting from south to north, and the time of the final emplacement may be the Middle-Late Miocene.

During the Early Eocene-Early Oligocene rifting period, the Zhuyi depression in the Pearl River Mouth basin mainly experienced acts Ⅰ and Ⅱ of the Zhu-Qiong movement and developed the Wenchang and Enping Formations. Xijiang sag is located in the west of Zhuyi depression. Panyu 4 sag is a proven hydrocarbon-rich depression, while Xijiang main sag and Xijiang 36 sag are not well explored. Based on the latest 3D seismic data and interpretation results, combined with limited drilling data, this paper systematically analyzes the sag structure, fault activity, migration of subsidence center and distribution of depositional system during the Wenchang period and Enping period. It is found that the tectonic transformation during the rift period is mainly reflected in the regular changes of sag structure, fault system, and the migration of subsidence center during the Early Wenchang, Late Wenchang and Enping periods. The migration of the depositional center is consistent with the subsidence center. The subfacies of semi-deep lake and deep lake were developed in the Early and Late Wenchang period, and the depositional center moved southwestern. The depositional center shifted to the north side of Xijiang sag in Enping period. Under the background of clockwise rotation of regional extensional stress direction, the activation of NW trending pre-existing faults in Wenchang led to the transformation of sag structure, fault activity and subsidence center, which controlled the distribution of the depositional system. The tectonic transformation and depositional system distribution of Xijiang depression have a certain significance for searching lacustrine source rocks and hydrocarbon-rich sag in the deep part of Zhuyi depression.

Hangjinqi area is an important hydrocarbon bearing area in the north of Ordos basin. The study of petroleum accumulation periods and fluid potential is conducive to exploring the generation of petroleum filling, the distribution characteristics of fluid potential, and further determining the migration direction of oil and gas during the accumulation period. In this paper, the reservoir sandstones of the First Member of Xiashihezi Formation (He 1) of the Permian system in five wells of Shiguhao block and Shilijiahan block are taken as the research objects. Based on the fluid inclusion analysis, the petroleum accumulation periods are determined, the fluid potential of the key reservoir formation periods in the study area is calculated, and the migration direction of petroleum is revealed by combining the fluid potential theory. The research results showed that the petroleum accumulation time of He 1 Member reservoir was 132-102 Ma in Shiguhao area, and 132-101 Ma in Shilijiahan area. The fluid potential of petroleum in He 1 Member of Shiguhao area in the north of Hangjinqi is 18 128-22 872 J/kg, and of Shilijiahan area in the south of Hangjinqi is 22 975-27 153 J / kg. It is considered that hydrocarbon accumulation time of the Permian He 1 Member reservoir was in the Early Cretaceous. The overall fluid potential in Shilijiahan area is higher than in Shiguhao area, and the petroleum has a migration trend from south to north.

This paper selected the Eocene low-permeability sandstones in the G oilfield, Bohai Bay basin as an example, and the influences of pore structure on reservoir quality and fluid occurrence were investigated by cast thin sections, scanning electron microscope (SEM), mercury injection capillary pressure (MICP), and nuclear magnetic resonance (NMR). Due to a highly variable pore size distribution, micro-scale and nano-scale pore throats coexist. The pore-throat size distributions generally present bimodal behaviors. The large pore systems are mainly composed of residual intergranular pores and enhanced intergranular dissolution pores，while the micropore systems are dominated by intragranular dissolution pores and intergranular pores. The results indicate that pore connectivity is the key factor affecting the physical properties and fluid occurrence state of the low permeability sandstone reservoirs. The sandstones with better petrophysical properties have a high proportion of macroscopic pore throats (right peak) with good connectivity, and the permeability capacity of the sandstones is strong. In contrast, the pore systems of the sandstones with poor petrophysical properties are dominated by the microscopic pore throats (left peak) with poor pore connectivity, and the permeability capacity of the sandstones is weak. Bound fluids mainly exist in small pore systems with poor pore connectivity and large fractal dimensions, while large pore systems have good pore connectivity and small fractal dimensions and mainly contain movable fluids. The study also clarified that the permeability and fluid occurrence state of low-permeability sandstone reservoirs is mainly controlled by the relatively large pore throats in the pore network. It is revealed that the permeability prediction model based on MICP data and porosity derived from the “effective movable fluid method” provides a better estimation effect compared with the classic models (e.g., Coates and SDR).

The formation tectonic background and mineralization process of the barite-witherite mineralization belt in the Silurian black rock series on the northern margin of the Yangtze plate have always been the focus of many scholars. This article selects the barite minerals in the mud shale of the Longmaxi Formation in the Lower Silurian of the Yueliangping section at the northern margin of the Sichuan basin as the research object. Starting from petrology and mineralogy, the development characteristics of barite are discussed, and the genesis of barite and its geological significance are analyzed by combining strontium isotopes. The results show that barite mainly develops into acicular shaped crystals dominated by diagenesis, larger particle size dissolution shaped crystals dominated by cold methane seeps, dendritic crystals dominated by hydrothermal processes, and small particle size ellipsoidal crystals dominated by biological processes. The barite nodules are distributed along the layers with oblate ellipsoid shape, with a concentric stratification structure, dense homogeneity structure, and turtle-crack filling structure. The genesis is mainly diagenesis, and local late hydrothermal fluid filling shrinkage cracks form turtle-cracks. The 87Sr/86Sr value of layered barite is 0.708 4, indicating that its formation process was influenced by the mixing effect of the deep mantle sources (low 87Sr/86Sr value) and the host rocks (high 87Sr/86Sr value). It is speculated that its formation was the result of the joint action of deep mantle derived hydrothermal fluids and cold methane seeps (or diagenesis). Research suggests that the sedimentary period of the Longmaxi Formation on the northern margin of the Sichuan basin was a passive continental margin with an extensional tectonic background, and synsedimentary faults developed in the North Dabashan. In the early stage of the Longmaxi Formation, the northern slope area of the Sichuan basin was subjected to weak extension, and the scale of fault development was not large, forming intermittent small-scale cold methane seepage. In the late stage of the Longmaxi Formation, the extension was strengthened, the fault deepened, and a black chimney of barite was generated. A large amount of hydrothermal fluids containing Ba2+ and H2S entered the seawater, forming barite deposits in the North Dabashan area.

To study the lithofacies types and reservoir characteristics of gas-bearing shale in the Upper Permian Dalong Formation in western Hubei area, the drilling cores of Endi 2 Well were taken as the research object and analyzed by whole rock X-ray diffraction, organic carbon content, vitrinite reflectance, kerogen microscopy, field emission scanning electron microscopy, carbon dioxide and nitrogen physical adsorption experiments, shale gas content and trace elements. The results show that the main lithofacies types of the Permian Dalong Formation in western Hubei include siliceous rocks, clayey siliceous rocks and mixed siliceous rocks, and the clayey siliceous lithofacies has the highest average organic carbon content. The shale of Dalong Formation has multiple pore types. Micropores and mesopores contribute to the main pore volume and specific surface area of shale. High organic carbon and clay mineral content are conducive to the accumulation of shale gas and the establishment of micro-pore system (pore size < 50 nm) in shale, and the adsorbed gas in micropores and mesopores is an important part of the total gas content. This paper established the evaluation criteria of Permian Dalong Formation shale in western Hubei based on gas content and TOC. The results show that clayey siliceous lithofacies and mixed siliceous lithofacies are Ⅱ1 class advantageous lithofacies types, siliceous lithofacies are Ⅱ2 class advantageous lithofacies types, and the 1 241.0-1 250.4 m section of Endi 2 Well is the “sweet section” of shale gas. The relationship between trace elements and organic carbon content of shale shows that the high organic matter content of Dalong Formation is the joint result of high productivity and water reduction environment, and the high ancient productivity is the main reason for the enrichment of organic matter.

A great number of sediment-hosted Cu-Pb-Zn deposits, including the ultra-large Uragen Pb-Zn deposit and the large Sareke Cu deposit, are found in the Meso-Cenozoic sedimentary basins (Kuzigongsu basin, Wulu-Wuqia basin, Keping basin and Kuqa basin) within the southwest Tianshan orogeny. These basins compose a significant base mental metallogenic belt in NW China. Numerous studies suggest that those deposits mainly include three types: The conglomerate-hosted Cu deposits, the sandstone-hosted Pb-Zn deposits, and the sandstone-hosted Cu deposits. Based on the main geological characteristics of each deposit type, this paper summarizes the research progress concerning the ore-forming ages, nature and source of the ore-forming fluids, and material source (metals and S). Results indicate that the conglomerate-hosted Cu deposits were formed at the end of the Early Cretaceous during the basin tectonic transition. The sandstone-hosted Pb-Zn and Cu deposits were formed in the Late Miocene and were both closely related to large retrograde thrust tectonics. The ore-forming fluid of conglomerate-hosted Cu deposits dominated by organic fluids, the sandstone-hosted Pb-Zn deposits by basin brine, and sandstone-hosted Cu deposits by a mixture of organic fluids and basin brine, with atmospheric precipitation contributing to the ore-forming process. The orogenic zone materials and the sedimentary sulfate are the main sources of metals and S for all deposit types in this region. This paper suggests enhancing research on the ore-forming age of sandstone-hosted Cu deposits, mineralization of the sandstone-hosted Pb-Zn deposits, and comparative study with newly discovered marine sandstone-hosted Cu deposits.

A detailed investigation of the Dafoyan bauxite deposit in Nanchuan District, Chongqing, was conducted to assess the distribution of beneficial components and associated elements. The study established a mineral resource availability evaluation model based on field investigations and sample analyses. High Ga quality scores are distributed in a northeast and nearly north-south direction, with higher Ga in the central and western regions and lower Ga in the northeast and eastern regions. The Li mass fraction is highest in the upper part of the Liangshan Formation, dense bauxite having the highest, followed by bauxite rock, and lower in soil bauxite. The enrichment of Li is closely related to bauxite. The enrichment sites of rare earth elements are more likely to occur at the bottom of the ore bearing strata. The evaluation model shows that bauxite resources in the mining area are exploitable. In developing and utilizing bauxite resources, the recovery and utilization of Ga elements can be considered. However, limitations in Li, Sc, and REE elements caused by factors such as beneficiation technology and beneficiation costs pose economic bottlenecks, despite the feasibility of current recycling technology. Therefore, alongside developing and utilizing bauxite resources, exploring more cost-effective recycling and utilization technologies is crucial to improve resource utilization efficiency. This evaluation model, with an an index system, can provide scientific guidance for bauxite resource utilization and evaluation, as well as for the evaluation of other mineral resources. Adjusting and optimizing evaluation indicators and weights according to specific mineral resources and scenarios is necessary to better serve practical needs.

In order to discuss the tectonic framework and evolution of the Northern Zhangguangcai Mountains, LA-MC-ICP-MS zircon U-Pb chronology, petrology, and petrogeochemistry studies were conducted on monzonitic granite, syenite granite and alkali-feldspar granite in this area. The zircon U-Pb ages of two monzonitic granites, one syenite granite, and one alkali feldspar granite are (191.4±1.1)Ma, (202.6±1.0)Ma, (190.8±1.5)Ma, and (198.1±1.0)Ma, respectively, in Early Jurassic. These granites are mainly classified as low aluminous, high potassium, and calc-alkaline series, have enrichment of large ion lithophile elements and lightly rare earth elements, like Rb, Ba, K, etc., whlie have depletion of high field strength elements and heavy rare earth elements, such as Nb, P, Ti, etc.. They exhibit characteristics of I-type granite, indicative of an active continental margin environment resulting from Paleo-Pacific plate subduction to Eurasia.

To elucidate the petrogenesis and tectonic settings of the Mesozoic rock formations in the Xing’an region of the Greater Khingan Range, this study employs petrology, chronology, and whole-rock geochemistry methods to investigate the Early Cretaceous intrusive rocks in the Huma area of Heilongjiang Province. The results reveal that the intrusive rocks are calc-alkaline to high-potassium calc-alkaline, quasi-aluminous to weakly peraluminous, crystallizing between (121.3±1.2) and (118.7±0.9) Ma. The rare earth element distribution patterns display a rightward trend with a weak positive Eu anomaly (0.98-1.11), enriched in large ion lithophile elements like K, Sr, Ba, and depleted in high field strength elements such as Nb, Ta, Ti, and P. The rocks show elevated ratios of Sr/Y (57.66-145.76), LaN/YbN (11.66-29.52), high Mg# (50.93-57.63), w(Cr) (77.00×10-6-92.60×10-6), and w(Ni) (23.20×10-6-32.60×10-6), indicating adakitic-like characteristics. Based on the comprehensive research, it is believed that the intrusive rocks primarily crystallized in an extensional environment following the closure of the Mongolian-Okhotsk Ocean, likely caused by lithospheric delamination thickening the lower crust and resulting in the upwelling of mantle-derived magma, forming adakitic-like rocks.

In this paper, the metamorphic siltstones of the Wanbao Formation in Dunhua, Jilin Province, were studied. The research included detailed analysis of detrital zircon trace elements and U-Pb-Hf isotopes to determine the sedimentary timeframe and source characteristics of the Wanbaoyan Formation. Further, the variation pattern of Late Paleozoic crustal thickness, inferred from detrital zircon trace elements, was used to explore the Late Paleozoic tectonic evolution history of the eastern part of the Northern margin of the North China plate. The Wanbao Formation consists of interbedded marble, metamorphic siltstone and metamorphic fine sandstone. The detrital zircon dating results show that the youngest peak age of the Wanbao Formation is ~316 Ma, in addition to peak ages of 355 Ma, 398 Ma, 1 842 Ma and 2 360 Ma. The Paleozoic detrital zircons (409-312 Ma) have negative  εHf(t) values (-15.32--1.60) and a TDM2 age (2 293-1 480 Ma) in the Neo-Paleozoic-Paleozoic period, with the age of the amphibolite bodies intruding Wanbao Formation is 276 Ma. The comprehensive study concludes that the depositional timeframe of Wanbao Formation in Dunhua area is 312-276 Ma, i.e., the Early Permian period, and shares similarities in depositional timeframe and rock assemblage characteristics with the Miaoling Formation in Yanbian area. The Paleozoic detrital zircons in Wanbao Formation are derived from partial melting of materials from the Paleozoic-Tertiary crystalline basement of the North China plate. Furthermore, the prevalence of Precambrian detrital zircons (62.9%) implies the presence of Precambrian crystalline basement of the North China plate in or near the Dunhua area. The crustal thickness calculation shows a similar trend in Late Paleozoic crustal thickness between Dunhua and Inner Mongolia regions, indicating synchronized evolutionary histories. The crust reached its maximum (80 km) thickness at ~245 Ma, suggesting the final closure of the Paleo-Asian Ocean.

The simulation accuracy of the particle discrete element method (DEM) mainly depends on the accuracy of calibrated mesoscopic parameters. To improve the calibration accuracy and efficiency of mesoscopic parameters, firstly，the rolling-resistance linear contact model was used to simulate sand triaxial compression tests. Then, the variance analysis method in orthogonal experiments is used to select the controlling mesoscopic parameters (CMP), and response surface equations are established to relate the macro parameters to the CMP. By substituting the macro parameters determined from triaxial tests into the response surface equations, the values of the CMP are solved. Finally, the accuracy of the calibrated micro parameters is verified by comparing the simulation results with the triaxial test results. The results show that the macro parameters include elastic modulus, Poisson’s ratio, dilatancy angle, and peak friction angle. The CMP for the elastic modulus are effective modulus and friction coefficient, while the controlling micro parameters for Poisson’s ratio are stiffness ratio and friction coefficient. The CMP of the peak friction angle and dilatancy angle are the friction coefficient. The elastic modulus, Poisson’s ratio, peak friction angle and dilatancy angle from the triaxial tests, are 83.83 MPa, 0.45, 34.47° and 8.93°, respectively. The corresponding mesoscopic parameters are determined as follows: Effective modulus of 153.35 MPa, stiffness ratio of 2.16, and friction coefficient of 0.45. Comparing simulation results from the calibrated mesoscopic parameters with the triaxial tests, the difference in peak strength is 7.2% at a low level of confining pressure (100 kPa), and the errors are within 15.0% at higher level of confining pressures (300 and 500 kPa).

In order to investigate the jacking characteristics of continuous penetration of jacked piles in layered soils, a field test is conducted in a pile foundation project in Shanghai to explore the evolution of jacking resistance with penetration depth. Combined with numerical simulation by software ABAQUS, the variation of vertical stress, radial stress and radial displacement of the soil around the pile during the penetration process of jacked pile is clarified. The results show that the softness and hardness of the layered soil govern the magnitude of the jacking resistance. When the pile body is located in the cohesive soil layer, the pile sinking resistance increases slowly or even decreases, and when the pile body is located in the silty clay and sandy silt soil layer, the pile sinking resistance increases faster, and the growth rate can reach 174% in the sandy silt soil layer. The vertical stress and radial stress in the soil around the pile are closely related to the soil properties. The maximum values of the vertical stress and radial stress appear when the pile end penetrates into the clay soil, which are 558.0 kPa and 1 178.0 kPa respectively. When the pile end penetrates into the softer silty clay layer below, the maximum vertical stress and radial stress both deteriorate significantly. The radial stress degradation rate reached 52%. The radial displacement decreases with the increase of radial distance, and its variation regular basically reflects the variation characteristics of soil layer properties.

Iron roughneck is advanced drilling auxiliary operation equipment, and domestic iron roughnecks have many shortcomings in automation degree, clamping positioning accuracy and work smoothness. In order to solve the problem，a new type of iron roughneck structure and its hydraulic control system are designed in this paper. Firstly, through the machine-hydraulic co-simulation analysis, the axis deviation angle and radial force change of the drill pipes during the makeup and breakout process of the iron roughneck were studied. Then, the control system of the iron roughneck is optimized on this basis, and the synchronous motor and PID (proportional integral differential) control are used to further analyze the influence of increasing hydraulic cylinders input flow rate on the synchronous performance of the hydraulic cylinders, clamping positioning accuracy and radial force of the joint thread of the fixed plier and moving plier. The results show that PID control has better clamping effect than synchronous motor. When the input flow rate of a single hydraulic cylinder is 18 L/min, the x and y axial deviation angles of the drill pipe can be controlled within 0.10°and 0.06°when clamped with fixed plier, and the response speed is about 6.8 seconds. The distance between the center of gravity of the upper and lower drill pipes along the x and y axis directions can be respectively controlled within 1.93 and 2.85 mm, which ensures the clamping positioning accuracy, rapidity and stability of the fixed plier and the moving plier. The radial force curve of the joint thread also indicates that the unbalanced radial force between the drill pipe joints during the iron roughnecks punching (17.2 kN) is much greater than that of the spinning (641.0 N), which is more likely to cause the drill bit to wear.

 In order to study the ground settlement caused by subway shield construction, firstly,based on Biot consolidation theory, a visco-elastic-plastic constitutive relation of soil mass and the dynamic change of soil permeability is considered, a three-dimensional fully coupled numerical model is established. Then, taking the shield construction section from Maluowei Station to Shitang Park Station of Jiangbei New District of Nanjing Metro Line 11 as an example, the settlement of the shield section is simulated and predicted, and the model is calibrated. Finally, the model is used to simulate and predict the ground settlement law caused by shield excavation, and the parameter changes of soil above the shield arch and under the shield bottom are simulated. The results show that the measured ground settlement is in good agreement with the calculated values, and the model is reliable. Taking the second section of the model as an example, the settlement of the eastern line is in the range of 52.41-54.52 mm, and the settlement of the western line is in the range of 53.28-55.60 mm. The settlement of shield tunnel in the eastern line is symmetrically distributed in the center of the tunnel axis, and the cumulative ground settlement of the tunnel in the western line is larger between the axes after tunnel excavation. With the progress of excavation, the porosity, permeability coefficient and Poisson’s ratio of the soil above decreased, and the deformation modulus increased, while the change of the soil below was opposite.

Land subsidence is a prominent geological hazard in the Beijing area, posing a serious threat to the sustainable development of the economy, environment and society. This paper takes the Chaoyang-Tongzhou area, which is a severely subsiding region of the Beijing Plain, as the research object. Based on Sentinel-1 A/B satellite track data and using PS-InSAR (persistent scatters InSAR） technology, the characteristics of land subsidence in the study area from 2019 to 2021 was obtained. The dynamic time warping (DTW) algorithm was used to quantitatively analyze the response relationship between land subsidence and groundwater levels at different depths, and then the contribution rate of groundwater at different depths to subsidence was quantified. The results show as follows: 1) From 2019 to 2021, land subsidence in the Chaoyang-Tongzhou area developed continuously. The most severe subsidence areas with an annual subsidence rate exceeding 50 mm/a were mainly distributed in the east of Chaoyang and the north of Tongzhou, and the maximum subsidence rate of 91 mm/a. 2) The difference in regional distribution of compressible layer thickness in the Chaoyang-Tongzhou area provids favorable geological conditions for the occurrence and development of land subsidence. On the whole, the thickness of the compressible layer is positively proportional to the land subsidence rate. The thickness of compressible layer at the location of PS points with a land subsidence rate greater than 80 mm/a in the study area was greater than 180 m, mainly in areas with a compressible layer thickness of 200-220 m. 3) Land subsidence responds differently to groundwater level time series at different depths. The water level in the confined aquifer with a burial depth of 50-180 m has a relatively high response degree to land subsidence, with the groundwater level at depths of 92.00 m and 121.42 m showing the highest response degree to land subsidence time series, reflecting that the groundwater level changes at this depth are the main inducing factors for subsidence.

Microcracks have increased the permeability of pores in limestone formations to varying degrees. In order to clarify the impact mechanism of different development of microcracks on the ability of drilling waste to be reinjected during the reinjection process and ensure the safe implementation of drilling waste reinjection, firstly, X ray CT (computed tomography) scanning was used to digitally reconstruct the limestone core collected from a certain gas field to obtain its matrix model, and the migration and sedimentation mechanism of waste particles in the pores were studied. Then, based on numerical algorithms, a fracture-matrix model is constructed, and the fracture connectivity coefficient and fracture orientation factor are introduced to quantitatively characterize the connectivity and orientation of fractures, and to reveal the influence of fracture opening on the permeability of reinjected formations and the ability of waste reinjection. The results have shown that as the crack direction factor increases, the lateral tortuosity shows a decreasing trend, with a maximum decrease of 35.21%, while the longitudinal tortuosity shows an increasing trend, with a maximum increase of 21.59%. The larger f (fracture connectivity coefficient), the more likely the fracture matrix model is to exhibit dominant channel effects (especially significant when f≥0.7), and the higher the permeability and particle escape rate. Compared with the matrix model, the permeability increases by 0.671 3  μm2, and the particle escape rate increases by 15.06%.

There are some important ecological reserves and oil exploitations in modern Yellow River delta, which located at the junction of sea and land. Influenced by rivers, currents and human activities, the modern Yellow River delta has a complex composition of sediment grain size and sources. A total of 219 sediment samples from the Yellow River delta were collected in this paper. Firstly, the grain size distribution and material source of the modern Yellow River delta sediment were analyzed by particle size analysis method. Then the parametric endmember model analysis method was used to divide the material sources of sediments. Finally, the cluster analysis method was used to analyze the surface sediment types. The results show that the grain size composition of delta sediments is mainly silt (71.10%) and sand (27.62%), most of the sediments are of medium grain size sorted and the curve of the grain size distribution is nearly symmetrical. The delta sediments can be divided into three types of end-mumber such as EM1, EM2 and EM3, which represent three different material sources. Among them, EM1 is from fluvial sediments, EM2 is from tidal current sediments and EM3 is from the current Yellow River fluvial sediments. According to the results of cluster analysis, the Yellow River delta is divided into three types of sedimentary environments. The first type is mainly distributed in the middle and upper reaches of western part of the Yellow River delta rivers, including Maxin River, Zhanli River, Caoqiaogou River and Tiaohe River, which is mainly deposited by old river with weak hydrodynamic force. The second type is mainly distributed in the eastern part of rivers such as Diaokou River, Shenxiangou and the current Yellow River (Qingshuigou), and the current Yellow River has strong sedimentary dynamics. The third type is mainly distributed along the northern coast and tidal flat of the Yellow River delta, which is strongly affected by the marine tidal and the coastline is eroded. In addition, human activities also had a certain impact on the changes of the coastline in the Yellow River delta.

It is of great significance to quickly determine the location information of seepage hazard for the treatment of embankments. However, in the process of magnetic weakening data processing of leakage channel, it often takes a long time to calculate the normal field of an embankment, which seriously restricts the locating efficiency of potential leakage hazards. In order to solve the above problems, based on the finite element method,  the modeling and simulation of the detection of embankment leakage by magnetometric resistivity method was carried out, and  the distribution characteristics of the internal stable current field and the external magnetic field of the embankment with different sizes were explored, and  a certain number of model databases were built. The results show that the overall fluctuation value of  y component of magnetic induction intensity in the middle part of the measurement domain is larger than that of x component and z   component, and its value decreases with the increase of the upper width of the embankment, and increases with the increase of the slope angle or the height of the embankment. According to the distribution characteristics summarized in this paper,  the missing normal field of embankment in the database can be predicted, and the mean relative error of the embankment model is 9.63%.

The time-domain electrical source electromagnetic detection method is an effective and fast method for detecting mineral resources. The polarization effect can lead to rapid attenuation of the electromagnetic response and even a symbol reversal phenomenon. In this paper, the Cole-Cole model is used to describe the polarization effect, and arbitrary fractional Cole-Cole models are rationalized by using the integer order rational approximation algorithm. Yee’s grid is used to divide the simulation area, and the three-dimensional numerical simulation of induction-polarization effect of electrical sources is realized based on the finite difference time domain (FDTD) method. The electromagnetic responses of three typical models, namely uniform half-space model, polarized half-space model and three-dimensional polarized body model, are numerically simulated. The results show that the electromagnetic response of  uniform half-space model is basically consistent with the analytical solution, and the relative error is less than 10%, which proves the feasibility of the three-dimensional numerical simulation method. The electromagnetic responses of  polarized half-space model and three-dimensional polarized body model both have negative responses in the late stage, which is consistent with the polarization theoretical results. 

The Poyang Lake area is located in a humid subtropical monsoon climate zone, but deserts are developed in many places along the lakeside. Duobao Desert is the largest desert among them, which has caused severe harm to the local environment. Previous researchers mostly believed that Duobao Desert was eolian, however, the stratigraphic stratification of many coastal outcrops is characterized by water formation. For further verifying the genesis of Duobao Desert, a combination of geophysical exploration (high-density resistivity method and transient electromagnetic method) and field geological outcrop investigation were applied in this study. It was found that the thickness distribution and sequence stratigraphy of the Quaternary of Duobao Desert are also  hydrogenic, besides the eolian features. This study indicated that Duobao Desert was the result of the combined action of both wind transport and underwater sedimentation, and its formation was related to the coupling of multiple factors in time and space, including the multiple fluctuations in the lake level, the southward expansion of the Penglize, a flat landform of the lake bottom, the rapid sedimentation of the delta, the differential movement of fault blocks, and the strong winter monsoon. Duobao Desert was developed in the Holocene， located in the subfacies of the front edge of the ancient Ganjiang River delta. After tectonic uplift, Duobao Desert was reconstructed by strong winds. The sand covered the paleotectonic highlands except for Xishan Mountain and Bijia Mountain, and finally made the current Duobao Desert.

Due to the limitation of complex conditions such as topography, the pre-stack seismic data are spatially incomplete or irregularly distributed, resulting in phenomena such as missing or confusing data. In recent years, methods based on convolutional neural networks have been widely used in the reconstruction of missing seismic data. However, the network model of one-step training process is not enough to reconstruct the missing seismic data with a wide amplitude range, and the reconstruction results of the low-amplitude missing part still need to be improved. Therefore,  a coarse-fine network model with a stepwise training process is proposed in this paper. The model consists of a coarse network and a fine network to recover the missing seismic data with a wide amplitude range in a step-by-step process. Discrete wavelet transform is introduced in the fine network instead of pooling operation, and its reversibility facilitates the preservation of detailed features in the up-sampling stage. Using a hybrid loss function, the model reconstructs the true details of the missing signals. The preliminary recovery results of the coarse network are processed by masking operation and input to the fine network, which further accurately recovers the low amplitude signal of the missing part. The experimental results show that compared with the reconstruction methods of residual network (ResNet), U-shaped network (U-Net) and multilevel wavelet convolutional neural network (MWCNN), the method in this paper demonstrates superior reconstruction performance on both synthetic and real data: the signal-to-noise ratio is 18.818 5 dB  on synthetic data with 75% missing, and 12.255 1 dB on real data with 50% missing. In the ablation study, the mean square error of the model reconstruction in this paper is1.689 3×10-4, the signal-to-noise ratio is 19.284 6 dB, the peak signal-to-noise ratio is 43.743 5 dB, and the structural similarity index is 0.984 1, all of which are better than the other three sets of control experiments.

Utilizing conventional well-logging curves for sequence division of glutenite reservoirs faces the problem of unclear interfaces and difficulty in determining division criteria. The variational mode decomposition (VMD) method has high decomposition precision and superior noise resistance, and is less affected by mode mixing, which can decompose the datum cycle information of each level in logging data. In this paper, VMD method  is applied to obtain the intrinsic mode function (IMF) of each frequency domain from  logging curves of thick glutenite strata in the Fourth Member of Yingcheng Formation of Xujiaweizi fault depression in Songliao basin, and  the highly correlated IMF 1 and IMF 10 are selected. According to  instantaneous frequency range and sampling rate, the high-frequency IMF 1 corresponds to the short cycle, and the low-frequency IMF 10 corresponds to the long cycle. The selection of the IMF corresponding to the cycle can guide the division of the corresponding level sequence,which can be divided into  two three-level sequences and five four-level sequences. The application of VMD in the Fourth Member of Yingcheng Formation shows that this method is suitable for high-frequency sequence division of thick glutenite strata.

In recent years, the Mesozoic clastic oil and gas reservoirs in the southern margin of  Junggar basin have made breakthroughs and become an important exploration field in the basin. Mesozoic strata generally contain gypsum, so the lithology optimization of gypsum-bearing strata is the key to reservoir evaluation. In order to improve the accuracy of lithology identification in this area and correct the reservoir curves of gypsum-bearing strata,  the response characteristics of logging curves of different lithologies based on petrophysical experiments is analyzed, and it is found  that the gypsum-bearing strata will lead to the decrease of compensated neutron value, the decrease of acoustic time difference and the increase of resistivity. The gypsum lithology is identified by logging. The Monte Carlo numerical simulation method is proposed to simulate the compensated neutron logging formation under the conditions of different porosity and different gypsum volume fraction in gypsiferous sandstone. A correction model of the compensated neutron porosity curve is established, and the fine division of lithology is finally realized. The coincidence rate between the interpreted lithology and the thin section analysis reaches 88.2%.

The lithology identification of rock thin sections is an indispensable part of geological analysis, and its precision directly affects the determination of the types, properties, mineral composition, and other microscopic information of subsequent stratigraphic rock, which is of great significance for geological exploration and mineral mining. In order to identify lithology quickly and accurately, an improved MobileNetV2 lightweight model is proposed to address the complex and diverse mineral composition in rock slices, which identifies lithology from a total of 3 700 rock slice images of five types of rocks. The coordinate attention mechanism is embedded in the inverse residual structure of MobileNetV2 to fuse global feature information of multiple minerals in the image. In addition, the classifier in MobileNetV2 is improved to reduce the number of parameters and computational complexity of the model, so as to improve the computing speed and efficiency of the model, and the leaky rectified linear unit (Leaky ReLU) is used as the activation function to avoid the problem of gradient vanishing in network training. Experimental results show that the improved MobileNetV2 model proposed in this paper has a size of only 2.30 MB, and the precision, recall rate, and F1 value on the test set are 91.24%, 90.18%, and 90.70%, respectively, which has high accuracy, and has the best classification effect compared with similar lightweight networks such as SqueezeNet and ShuffleNetV2.