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Significance The micromigration of shale oil refers to the phenomenon in which oil is generated in organic-rich layers and expelled at short distances to adjacent, preferable porous and permeable, organic-lean layers in shale systems. Micromigration can effectively improve the oil content and quality of organic-lean layers, even surpassing some organic-rich shale layers based on the exploration practices. Therefore, it is necessary to conduct a systematic study on the micromigration phenomenon of shale oil. Progress Based on the current research progress, this paper first identifies the main tracers of shale oil micromigration, which include rock pyrolysis parameters, hydrocarbon components, biomarkers, NSO compounds, as well as isotopes. The fundamental principle relies on fractionation between migrated hydrocarbons and retained hydrocarbons based on their geochemical properties. Analysis revealed that micromigration can lead to a dispersed distribution of hydrocarbon generation activation energy in organic-lean shale layers, resulting in an earlier hydrocarbon generation threshold. Moreover, the accumulation of light hydrocarbons in a free state in organic-lean layers can further increase the difference of hydrocarbon components between generative units and in-source reservoirs, thereby affecting the oil-bearing and mobility characteristics of shale. Based on the effects of petroleum migration and geological zonation, this paper reveals that micromigration occurs throughout the entire process of hydrocarbon generation, expulsion, and retention. It serves as a bridge connecting all elements of petroleum accumulation within shale systems, influencing the differential enrichment of shale oil. Conclusions and Prospects Comprehensive geochemical and geophysical methods are effective ways to identify micromigration in shale systems and will provide a new perspective for revealing the dynamic differential enrichment of lacustrine shale oil.

Objective In geothermal exploration, a clay cap is a typical hydrothermal geothermal system, and its depth and distribution range can provide crucial information for delineating the scope of geothermal resources and determining the location of geothermal drilling. Clay caps are usually composed of a clay layer formed through hydrothermal reactions and are characterized by low resistance. The low-resistivity cap can be effectively imaged using the audio-frequency magnetotelluric method. To obtain uncertainty information about the distribution of clay cap layers and imaging results, this paper employs the 1D trans-dimensional Bayesian inversion method to investigate the detection capabilities of low-resistance cap layers in geothermal areas through audio electromagnetic data. Methods In this paper, a model test is first carried out to establish a geoelectric model of a typical geothermal system.Subsequently, a 1D trans-dimensional Bayesian algorithm is used to invert the synthetic data to obtain the uncertainty information of the subsurface electrical structure and interface position. Then, the method was applied to the processing of measured audio frequency magnetotelluric data in the Yanggao geothermal area of Shanxi Province. Results This method has relatively accurate identification ability for low-resistivity clay caps, and the obtained uncertainty analysis results of the upper and lower interfaces of low-resistivity caps are also relatively reliable according to numerical tests. It was found that this method has a good ability to identify shallow low-resistivity caps and can provide an uncertainty evaluation of the clay cap interface position via field data tests. The 2D inversion results of this survey line verify the reliability of the 1D inversion. Conclusion This method has relatively accurate imaging capabilities and uncertainty analysis capabilities for shallow geothermal clay caprocks and has strong application prospects in geothermal detection.

Objective Black carbon is a carbonaceous mixture formed by the incomplete combustion of biomass and fossil fuels. Since black carbon has a high carbon content and an aromatized molecular structure, it can persist in the natural environment, suggesting that black carbon is an important component of the global carbon cycle. Although pioneering studies have advanced the understanding of nature, circulation fluxes, and reserves of black carbon in the geosphere, it is still necessary to further clarify the source-sink processes of black carbon and explore the importance of black carbon in the global carbon cycle. Methods Here, this study reviews the available data on pathways, fluxes, and time scales of the global black carbon cycle and analyses and summarizes the migration mechanisms and constraints in the source-sink process of marine black carbon. Results This paper concludes that marine sediments serve as a large reservoir for black carbon, with a reserve of 569-1 380 Pg. Black carbon can persist over millennia in marine sediments, which is associated with a long turnover time as an "effective carbon sink" in the context of "carbon neutrality". Moreover, black carbon exerts a negative feedback effect on global warming due to its longer turnover cycle time than biomass carbon. The deposition of black carbon into the sea is an effective means to enhance carbon sequestration in the ocean and could be an effective way to implement the carbon capture, utilization, and storage (CCUS) strategy. Conclusion In this paper, we propose that human-induced production of black carbon from biogenic combustion may be actively regulated and that the deposition pathways and burial areas of black carbon into the sea should also be optimized given the premise of ecological and environmental friendliness based on a summary and assessment of the strategic value and climate significance of black carbon in marine sediments in the context of "carbon neutrality". Therefore, the positive role of black carbon in "negative ocean carbon emissions" can provide a basic theoretical framework for achieving the goals of "carbon neutrality".

Objective Palaeomagnetic methods can be used to quantitatively constrain the Early Palaeozoic palaeo-position of the North China Block (NCB), which provides a crucial scientific basis for researching the evolution of the Proto-Tethyan Orogeny and the affinity of the NCB for Gondwana. However, the NCB has undergone considerable tectonic activity since the Early Palaeozoic, and the Ordos Basin in the western part of the NCB is rich in hydrocarbon resources. Late tectonic activity and the migration of hydrocarbon resources may have caused remagnetization of Early Palaeozoic strata. Methods Thus, in this paper, to determine the main magnetic minerals in various rocks and their ability to record the primary remanent magnetization, we carry out a series of detailed petrography, rock magnetism and stepwise demagnetization experiments on the limestone and tuff samples of the Upper Ordovician Zhaolaoyu Formation in the Fuping area of the southern Ordos Basin, including optical microscope identification, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), saturated isothermal remanent magnetization (SIRM) acquisition curve, three-axis isothermal thermal demagnetization test, κ-T curve test, hysteresis loop experiment, first-order reversal curve (FORC), and thermal demagnetization and hybrid (TD+AF) demagnetization. Results The results indicate that the main magnetic minerals in the limestone and tuff samples are magnetite, pyrrhotite and/or greigite, and some samples also contain a tiny quantity of haematite with impurities and goethite. Mineral particles possess single domains (SDs) as well as multiple domains (MDs) within their magnetic domains. Combining petrographic and demagnetization data, this paper suggests that the main magnetic minerals in the samples are likely secondary minerals associated with later fluid alteration (maturation and migration of organic matter). Conclusion The remanent magnetic signals conveyed by these rocks cannot be directly used to constrain the Early Palaeozoic palaeoposition of the NCB but may be used to constrain hydrocarbon migration and accumulation in the Lower Palaeozoic strata of the southern Ordos Basin.

Objective Machine learning has been widely applied in the fields of collapse, landslide and debris flow susceptibility analysis. The selection of nonhazard samples is a key issue in landslide susceptibility analysis. Traditional random sampling and manual labelling methods may involve randomness and subjectivity. Methods In view of the potential randomness and representativeness of noncollapse samples, this paper considered soil collapse susceptibility evaluation a positive-unlabelled (PU) learning problem and proposes a two-step convolutional neural network framework (ISpy-CNN) that combines an information value model and the Spy technique. First, 15 collapse-related factors were selected for modelling based on the geomorphological, geological, hydrological, and artificial environmental conditions of the study area. Low-information-value samples that were able to map the distribution structure of noncollapsing samples were screened by the information value model. Then, through the Spy technique and training the CNN model, negative samples with high confidence were identified from low-information-value samples that were classified as noncollapsed samples. Finally, based on the framework and traditional random sampling, we used support vector machine (SVM) and random forest (RF) models to compare and verify the reliability, prediction accuracy and data sensitivity of the proposed learning framework and other models. Results The results illustrate that the proposed ISpy-CNN method can improve the accuracy, F1 value, sensitivity and specificity on the validation set by 6.82%, 6.82%, 6.82%, 8.23%, respectively compared to random sampling and 2.86%, 2.89%, 2.86%, 2.31%, respectively compared to the traditional Spy technique. The prediction accuracy of step 2 in PU learning using the CNN model is higher than that of the RF and SVM models. The sample set screened by the ISpy-CNN framework exhibited greater stability, prediction accuracy and growth rate than those screened by the traditional Spy technique by adding the same number of training samples. Conclusion The ISpy-CNN framework proposed in this paper can better assist in the selection of nonhazard samples and real collapse spatial distribution maps, and the results of the framework are more consistent with the actual collapse distributions.

Objective Landslide dams are a geological body of key concern for engineering construction in alpine canyon areas. This paper takes the Dalongchi landslide dam in the South Tianshan Mountains as the research object to explore the origin and evolution process of the landslide dam in alpine canyon areas of the South Tianshan Mountains. Methods Based on satellite remote sensing images, regional data, field investigation, and geological drilling data in the Dalongchi region, combined with theoretical calculations and finite element discrete element simulations, this paper systematically delved into the deposit characteristics and the formation and evolution process of the Dalongchi damming body. Results The results show that (1) Many landslide scratches and grooves can be seen on the steep mountain surface on the North side of the Dalongchi damming body, of which the packing structure has obvious inverse grading features and a jigsaw structure, and it is speculated that the formation may be caused by the accumulation of the high-speed and long-distance ancient landslide of Dalongchi. (2) By conducting the recurrence of the northern original surface of the Dalongchi landslide and theoretical calculation and numerical simulation on its kinematic characteristics, the results were then induced that there was a high-speed and long-distance landslide on the north side of the mountain that led to the formation of the damming body of Dalongchi. (3) The formation and evolutionary phases of the Dalongchi damming body can be divided into the embryonic stage of ancient landslides, the river-blocking forming stage of the damming stage by ancient landslides, and the overlapping stage of ancient damming bodies. Conclusion The study of the formation and evolution of the Dalongchi dammingbody can provide a reference for the subsequent genetic analysis of similar studies in the southern Tianshan region.

Objective 3D geological modelling is a kind of technology that converts multisource geological data into 3D geological models through computer. It reveals the spatial distribution relationship between various underground geological bodies, which helps geologists understand underground geological structures more intuitively, providing certain support for resource exploration, disaster prediction, engineering construction.However, complex geological environment, scarcity of effective geological data, large amount of calculation and other factors make the construction of large-scale complex geological bodies become an urgent problem to be solved in the development of 3D geological modelling. Methods To address these issue, this paper proposes a large range of complex geological body block modelling methods. Based on the model horizontal distribution scope of bounding box, large range of research area will be divided into several relatively smaller ones to perform modelling. At the same time, virtual borehole and stratum partition automatic tracking algorithm will be introduced for the block model at the bottom, top and middle part for the consistency of boundary constraints.At the same time, when modelling each block, the range of modelling data is extended to ensure that the strata between merged blocks can achieve smooth transition at the boundary of block. Results Each block of model is combined into a complete one with coherent and smooth stara so that a large range of complex three-dimensional geological body modelling can be realized. Conclusion Taking the shallow underground model of the Xiamen Maluan Bay New urban area as an example, this paper constructed corresponding geological model to test the modelling effect. The model is dissected and compared with the real borehole. The feasibility of proposed method is verified in terms of modelling efficiency, continuity and smoothness of strata connection.

Objective With the development of drilling technology for deep strata, the study of the dynamic characteristics and parametric response law of drill bits and deep complex strata during drilling has become a key and difficult point in research. Methods In this paper, a combination of numerical simulation and response surface analysis was used to study the dynamic characteristics of PDC bits and typical complex strata in the drilling process, and parametric analysis was carried out. In this paper, soft-hard-staggered strata with dip angles as a typical complex formation were studied, the dynamic damage finite element simulation model between the PDC drill bit and the soft-hard-staggered strata with the full real size was established based on Abaqus, and the dynamic characteristics of the drill bit subjected to the reaction force of the strata during drilling were derived. Numerical simulation experiments were also conducted by orthogonal tests to investigate the dynamic characteristics of the PDC bit under different formation parameters and drilling parameters. Results The single factor analysis and response surface analysis were used to model and identify the relationship between drilling parameters and stratigraphic parameters and the reaction force on the drill bit by the stratum and to obtain the changing trend and regression model of the reaction force on the drill bit by the stratum under multiple parameters. The results showed that the higher the inclination angle of soft-hard-staggered strata, the higher the average value and peak impact value of the bit subjected to the stratigraphic reaction force. The larger the ratio of softness to the hardness of the strata is, the larger the average and peak reaction forces on the drill bit. Within a certain range, increasing the rotational speed will reduce the impact of the reaction force on the drill bit. Conclusion The research results provide a basis for predicting the bit reaction force during drilling in deep and complex formations and guide the control of the drilling trajectory in deep and complex formations, which is of great significance for deep geological drilling.

Objective Recently, the seismic damage of an actual bridge structure in a frozen soil area has shown that the presence of frozen soil will increase the lateral stiffness of the bridge foundation, which may cause more serious seismic damage to the bridge structure, but there is a lack of research on the frozen soil-pile interaction effect of frozen soil bridge structures under seismic loadings and the corresponding seismic responses. Methods The present paper proposed efficient nonlinear numerical models to consider the effect of the frozen soil-pile interaction on the seismic responses of structures. First, the relationship between the depth of frozen soil and surface temperature was constructed. Then, the p-y spring modelling approach was presented to simulate the seismic behavior of frozen soil. Several as-recorded ground motions were selected as the seismic input. The seismic responses of piers and bearings of regular bridges with different depths of frozen soil under seismic loadings were investigated. Results The results show that the proposed efficient nonlinear numerical model can be adopted to model the seismic behavior of bridges considering frozen soil. And the proposed p-y curves for frozen soil can accurately predict the p-y relationship from the existing tests. When the PGA is relatively small, the pier curvature increases slightly; by contrast, in the case of large PGA, frozen soil can significantly increase the curvature demands, which can make the pier enter into the inelastic behavior. When the depth of frozen soil is small (the temperature is -5℃), the bearing displacement increases significantly, which increases the probability of unseating under seismic loadings. Moreover, frozen soil can transfer to the adverse locations of structural systems under seismic loadings. Conclusion Therefore, the conclusions of this paper can provide the necessary theoretical basis and data support for studying the seismic performance and corresponding seismic design methods of frozen soil bridge structures in China, which is of great significance for promoting the development and engineering application of disaster prevention and mitigation of bridge engineering in frozen soil areas in China.

Objective Monitoring natural attenuation (MNA) is a widely used, economical and effective remediation technique for soil and groundwater contamination. The migration of nonaqueous phase liquid (NAPL) in heterogeneous strata is an important element in the assessment for the efficiency of MNA. Methods Based on three consecutive years of dynamic groundwater quality monitoring data, the purpose of this study is to accurately characterize the biodegradation processes of multiphase fluids at a typical phenol contaminated site in northern China. A multiphase flow numerical model of phenol transport considering Monod biodegradation processes based on TOUGH3/TMVOCBio software was developed and applied. The model depicted the spatial distribution and temporal variation of phenol under the current conditions well and analysed the sensitivities of the adsorption and biodegradation parameters. The paper also discussed the removal contributions of dissolution, volatilization, adsorption and biodegradation effects under uncertainty of adsorption and microbial degradation parameters and predicted two different natural attenuation scenarios for source disposal. Results The contribution of phenol removal varies over a range under the influence of parameter uncertainty, with 17.91% to 58.02% for biodegradation, and precipitation conditions affect the seasonal variation in phenol concentrations. In the future 20 years, under the conditions with complete removal of the phenol source and the present leakage model, the total mass removal rate of phenol will arrive at 98% and 80% at the end of the 20th year, respectively. Conclusion This paper identifies the biodegradation parameters with high sensitivity in the multiphase flow model, which provides a reference for the numerical simulation of the organic matter biodegradation process at petrochemical sites and can also provide a theoretical basis for the application of MNA technology in China.

Objective In order to understand groundwater systems, it is useful to study the changing characteristics and mechanisms of hydrogeological parameters with time. Responses of groundwater level microfluctuations to natural periodic loadings, such as earth tides and barometric pressure, serve as low-cost and effective investigation technique to calculate aquifer hydrogeological parameters. Methods In this paper, we systematically reviewed theoretical methods of hydrogeological parameters estimation based on groundwater level response to earth tides, barometric pressure, and their combination. We presented earthquake-related and mining-related parameters change with time in well-aquifer system. The barometric pressure response method also applies to the assessment of aquifer vulnerability. Results We conclude that studying the microfluctuation of groundwater level may provide insight into the interaction among hydrogeological processes, tectonic activities, and artificial influences in the shallow crust at spatial and temporal scales. Conclusion This paper also proposes three scientific problems to be solved in the future: the application of skin and wellbore storage effects, the improvement of computation accuracy of hydrogeological parameters by combining multiple methods for determining basic geological parameters, and the investigation of other artificial influences such as groundwater overdraft and subsidence to regional aquifer systems.

Based on geological surveys and experimental data, numerical modeling of metallogenic dynamics (NMMD) establishes a mathematical model (mathematical-physical equation) that quantitatively characterizes metallogenic processes using the basic laws of mathematics, physics and chemistry. Then, using the finite element or finite difference method, the model is built through efficient computer calculation, simulating the metallogenic dynamic process and its metallogenic response, revealing metallogenic law and guiding prospecting. NMMD integrates theories and methods of geology, mathematics, physics, chemistry, computers and other disciplines and has distinct characteristics of interdisciplinary integration. In recent years, driven by the rapid development of computational science and mathematical geology, important progress has been made in NMMD. This paper summarizes the basic theories and methods of NMMD, compares the characteristics of four metallogenic numerical simulation software programs, and introduces the development and application status of NMMD with progress of the author′s team in the past decade. The main conclusions and understandings are as follows: ①Multi-field coupled metallogenic dynamics numerical simulation is the only feasible method to reproduce the large-scale complex metallogenic process. With the rapid development and improvement of high-performance computing technology and nonlinear dynamics theory, it becomes one of the research hotspots and development directions of modern mathematical geoscience. It is important to reveal the metallogenic mechanism and obtain mineral exploration information, which has great potential for development; ②At present, there are some limitations in NMMD, such as uncertain simulation parameters and incomplete coupling of multifield processes, which will be the focus of its future development. Numerous studies have been devoted to solving these problems; ③Under a new paradigm of scientific research driven by big data, a combination of NMMD and machine learning can effectively invert the metallogenic process and quantitatively predict mineral resources. This method is an important breakthrough in the application of NMMD in deposit genesis and mineral exploration. This paper clarifies the basic methods and key problems of NMMD in promoting the study of deposit genesis and exploration, and expounds the frontier direction of NMMD, which provides basic guidance for the study of computational modeling of metallogenic dynamics.

Natural gas hydrate is a kind of clean energy with great development potential but is still not commercially developed due to the bottlenecks such as exploitation technology, economical efficiency, and environmental effects.In recent years, people have explored the application of hydrate technology in the field of CO2 capture, seawater desalination, energy storage, gas separation, etc. One of the most challenging and critical problems is how the hydrates are formed and decomposed at any time. This paper summarizes the fundamental research on hydrate decomposition dynamics, including hydrate decomposition properties, influencing factors, and dissociation mechanisms. Moreover, the paper reviews the development of hydrate dissociation dynamics models. The existing models are divided into four categories according to dissociation mechanisms: Thermal dissociation models, intrinsic dynamics models, mass transfer dissociation models and integrated models, and their assumptions, main understanding and limitations are highlighted. Future directions for improving hydrate dissociation dynamics research are foreseen to deepen the understanding of hydrate dissociation dynamics and promote the development and utilization of hydrates.

It is necessary to plat the multiple-map sheet data sets into a single map when processing the geochemical data from the entire map sheet and compiling a large-scale geochemical map, but step effects might readily arise where different map sheets converge. There are currently few papers that compare and optimize various methods, and most systematic error-related studies focus on a specific way to correct and assess the step effect of geochemical data in a particular area. With the map sheet from the Yuanyi, Bajiabielichier, Goulixiang, and Zhiyi in Gouli region of Qinghai Province as a case study, this paper applies the framing standardization method, normalized method, and contrast method to perform systematic error correction and method optimization on 1∶50 000 stream sediment geochemical data and provides the effective method reference for the systematic error processing of the geochemical prospecting data of the rock cuttings. The results indicate that these three methods have distinct effects on systematic error correction.After the original data are corrected, the background difference between adjacent map sheets is basically eliminated, the step effect is effectively weakened, the geochemical zoning is continuous, the strong anomalies are appropriately suppressed, and the weak anomalies are appropriately enhanced and represented in the background. After the same element is corrected with various methods, there are differences in the anomalous area, form of anomalies, and goodness of fit with the mineral deposit (point). The goodness of fit between anomalies and known deposits (points) after correction with the framing standardization method and normalized method is 75%; the anomalies are evenly distributed throughout the region, but individual ore-induced anomalies are weakened, and the influence of invalid anomalies cannot be avoided. The nonmineral anomaly in the high background area can be effectively suppressed by the contrast method, and the mineral-induced anomaly in the low background area can be strengthened. The anomaly's goodness of fit with the deposit (point) is 87.5%, the invalid anomaly's influence is minimal, and the geological background has the maximum goodness of fit. Combined with the study on the physical geological body conditions in the region of interest, the contrast method is more suitable for the correction of systematic errors in stream sediment geochemical survey data on different map sheets in the Gouli Region and can be selected and applied in geochemical data processing under similar topographic and geomorphic conditions in Northwest China.

Groundwater pollution risk assessment is an effective tool for preventing and controlling groundwater pollution. The study on groundwater pollution risk assessment can serve as a basis for the management of groundwater contaminated sites. The present risk assessments often ignore the spatial variability of pollution within the site and the susceptibility of receptor. This paper proposes a new site groundwater pollution risk index system that can be used for pollution sites with a variety of features. The index system considers the spatial distribution of pollutant at the site and nearby receptors. Based on the four aspects of pollution load, vadose zone vulnerability, aquifer vulnerability, and receptor susceptibility, this paper conducted index screening and weight calculation using the analytical hierarchy process. A site groundwater pollution risk assessment index system was constructed, and the risk was divided into four levels: low, medium, higher, and high. Using the constructed risk index system, the spatial risk distribution of a hexavalent chromium site in Henan Province was studied. The results show that the site was at a medium risk level, with the highest risk at the chrome slag heaps and the southeastern of the buried chrome slag. The potential loss of surrounding receptors and the pollution load are the main causes of groundwater contamination risk at the site. Single parameter sensitivity analysis shows that the effective weights of each index are in line with the theoretical weights, indicating the rationality of the constructed site groundwater pollution risk assessment system, which can be applied to other sites with characteristic pollutants.

To clarify the final breakup characteristics of the crustal lithosphere at the tip of the Southwest Subbasin in South China Sea and its evolution stages, this paper interpreted 2D deep seismic lines and analyzed the fault activities, the proto-basin type in different stages, the rates of subsidence and the history of tectonic and subsidence evolutions. It was clear that the distal domain and ocean continental transition consist of the final breakup zone of continental lithosphere at the tip of southwest South China Sea. According to the shape of the crust, this final breakup zone could be subdivided into a box domain, wedge domain and proto-oceanic domain. The basins within the wedge-shaped domain had been divided into the rifting basin (Tg-Sd), the detachment basin (Sd-Pd), and the sag basin (Pd-Bi). The basins within the box-shaped domain were of the rifting type from the Paleocene to Oligocene (Tg-Sd) and then transitioned to the passive sedimentation stage. From the Cenozoic, the sedimentation center on the tip of the Southwest Subbasin migrated from continental to ocean during the tectonic evolution of this region. The magmatism developed strongly and finally broke up the continental crust. The comparison of high-resolution seismic data showed that the tectono-sediments and magma type were different within different domains at the V-shape tip of the Southwest Subbasin. The continental crust of the research area broke apart after the "double detachment faulting". Then, the magma came in and formed the proto-oceanic crust. The research in this paper was of great value for oil and gas exploration in the deep-water basin in the southwest South China Sea.

Mesozoic sags of the Qiongdongnan Basin are prospective areas for oil and gas discovery. To make petroleum breakthroughs in Mesozoic sags in the Qiongdongnan Basin, it is urgent to clarify the conditions of hydrocarbon accumulation and the favorable areas for exploration in those Mesozoic sags. Based on geophysics, geochemistry, drilling and paleontology data, systematic research on Mesozoic sags in the Qiongdongnan Basin was carried out. The results show that Mesozoic sedimentary formations were distributed in the Yabei Sag, Yacheng Uplift, Yanan Uplift, Lingnan Uplift and Southern Massif in the Qiongdongnan Basin. According to the analysis of tectonic evolution, Mesozoic formations were formed in the back-arc extensional basin in the Yanshanian period with subduction of the Pacific Plate to the Eurasian Plate, which has the possibility of forming source rocks, reservoirs, and traps. Because the potential of Mesozoic sags is larger in the Yacheng-Yabei area of the northern depression than in other areas in the Qiongdongnan Basin, this paper focuses on the comprehensive study of petroleum geology in the Yacheng-Yabei area that includes the definition of the Mesozoic formation and defines the favorable area and prospects of Mesozoic rocks. This paper further notes that Mesozoic lacustrine source rocks, delta reservoirs, structural and stratigraphic traps developed in the Yacheng-Yabei area. The southern slopes of the western sag and central massif are two favorable areas for exploration. To expand exploration in these areas, we hope to make petroleum breakthroughs in Mesozoic formations.

Pockmarks are a kind of negative geomorphology formed by overpressure fluid spilling from the seabed. They are widely distributed in various underwater tectonic environments (such as continental margin basins and accretion wedges). Based on the recent research progress and achievements of pockmarks, this paper systematically divides the types of pockmarks according to their shapes, diameters, length width ratios, distribution characteristics and vertical filling modes. Moreover, this paper detailed introduces the main conditions and influence factors (such as diapir and fault)and deeply analyzes the genetic mechanisms of pockmarks. The local abnormal fluid pressure (overpressure) is the key factor to trigger the formation of pockmarks. According to the formation and leakage speed of overpressure during pockmark formation, the genetic mechanisms of pockmarks can bedivided into progressive, sudden and transitional three types. In the progressive formation model, both the formation and leakage processes of overpressure are slow. Whilst in the sudden formation model, the formation and leakage processes of overpressure are fast. For the transitional model, the formation and leakage processes of overpressure are faster than those of the progressive model but slower than those of the sudden model. The formation of pockmarks is affected by many factors, such as seawater and underlying strata. The physical and numerical simulation of dynamic overpressure formation and vertical migration to the seabed may be the future study directions of pockmarks.

As a new type of fiber optic sensing technology for long-distance, distributed and real-time monitoring, distributed acoustic sensing (DAS) has been a wide concern since its initiation. Compared with the traditional seismic wave sensing system (node array, geophone, seismometer), DAS has the advantages of high spatial sampling density, wide measurement range, and strong environmental adaptability (anti-electromagnetic interference, corrosion resistance, waterproof).Recently, researchers have carried out a large number of exploratory experiments around DAS technology and made important progress in the field of earth exploration.This paper reviews the latest research on the application of DAS technology for earth exploration. Starting from theworking concept of DAS, the basic concept of DAS is elaborated, and the performance of DAS and seismometer is fully compared.And we introduce the applications of DAS in oil and gas exploration, seismic observation, and structural imagingby reviewing several representative experiments. Finally, this paper summarizes the current bottleneck of the earth exploration technological system based on DAS and analyzes the development trends in the future.

The engineering geological interface is defined as the contact surfaces between two or more media in strata, as well as the transition surfaces that control the migration of three-phase matter, the change in physical states and the stability of rock and soil masses. Under the combined action of natural loads and engineering activities, they play a controlling role in the emergence, propagation, and triggering of geological disasters. How to accurately capture multifield evolution information, understand the catastrophic dynamics, and clarify the interaction mechanism of the interface are key scientific issues in the research field of geohazard mitigation and prevention. On the basis of reviewing the development history of engineering geological interface-related research areas, this paper summarizes the basic concepts, classification systems, and critical characteristics of the interface. Taking the landslides in the Three Gorges reservoir area of the Yangtze River as an example and combined with the research works of our team, we elaborated the latest research progress in multivariate characterization and evolution mechanism of engineering geological interfaces, and finally prospected the future development trends in this paper. The above review shows that the engineering geological interfaces is the critical zone inducing geological hazards, which can be divided into three types: material interface, state interface, and motion interface. By introducing fiber optic sensing and other technologies, the intelligent characterization of multivariate of engineering geological interfaces is preliminarily realized. On the basis of long-term in-situ monitoring of reservoir landslides, the disaster evolution mechanism and interface control modes are systematically summarized. According to the discipline development trend and national demand, more attention should be given to developing and building an integrated three-dimensional space-sky-surface-body monitoring network in the future, considering the characteristics of engineering geological interface. In this way, real-time acquisition and identification of thermal-hydrologic-mechanical multifield coupling information of key interfaces will be realized. By combining big data and artificial intelligence technologies, corresponding early warning and forecasting systems will be developed, so as to improve the prevention level and response capability of major geological disasters.

Currently, double reduction method (DRM) is widely used in the field of slope stability. However, one of the main challenges of the double reduction method is how to define the comprehensive safety factor based on two reduction parameters. The trajectory reduction method developed by Isakov can be used to ensure the minimum comprehensive safety factor on different conditions. However, its main shortcoming is that the method needs expensive calculation to determine the safety factor for a certain slope configuration. The paper examines the relationship between the comprehensive safety factor and cohesive and internal friction angle of soil, by using the FEM and trajectory method to calculate the minimum safety factor and corresponding reduction factor with respect to different inclinations of the slope. The initial strength effect on double reduction parameters are analyzed accordingly. The result shows for a certain slope configuration; the initial strength has little effect on the critical strength which is related to the minimum comprehensive safety factor. It means that for a slope with a certain inclination, even if the strength of soil is different, the critical strength is identical. The critical strength of soil slope is linear with the inclination of the slope, which means that every inclination corresponds to one critical cohesive and one critical internal friction angle. Consequently, a novel method to calculate the minimum safety factor is proposed in this paper. The result obtained by this method is close to the result which is from the limit equilibrium method, and compared with the original method by Isakov, this alternative method can simplify the calculation, and keep the result as accurate as the limit equilibrium method. Thus, it can be used to analyze the stability of slope.

The limit analysis of slope stability has a relatively higher calculation efficiency and accuracy because it ignores the constitutive relation of materials. Compared to the limit equilibrium method, its assumptions are strict and realistic. In the classical upper bound limit analysis, the slope surfaces are required to be a regular straight line. However, the surfaces of natural or cutting slopes are normally nonlinear. In addition, the stability number Ns=c/γH is used to calculate the critical height of slopes without considering the external power caused by pore pressure. Different from the static equilibrium conditions adopted by the traditional limit equilibrium method, this paper aimed to evaluate the stability of slopes with nonlinear surfaces based on kinetic analysis. First, a method for determining the rotation center of landslides with nonlinear surfaces based on upper bound limit analysis and the principle of virtual work was proposed. Second, it was assumed that the sliding surface was a logarithmic helix, and the virtual work under gravity and energy equilibrium equation of slopes were established. Third, the stability coefficient K defined by the ratio of internal power to external power was proposed to evaluate the stability of the slope, and the results were compared with the Bishop method to verify its effectiveness. The influences of slope degree (β), internal friction angle (φ), cohesion (c) and pore pressure coefficient (ru) on the stability coefficient K of different natural and cutting slopes were analyzed. The results confirmed that the stability of steep slopes would be improved by cutting. The stability coefficient K increased with increasing cohesion and decreased with increasing pore water pressure coefficient. When the impact of cohesion on the stability coefficient K was more significant than that on the pore water pressure coefficient, K increased with increasing internal friction angle (φ). In contrast, the stability coefficient K decreases with increasing internal friction angle (φ). The above results followed the general understanding of slope stability analysis, and the rationality of the model was verified. By comparing the calculation results with the Bishop method, it was found that the intension of the critical state represented by safety factor FS=1 was the same as the stability coefficient K=0 defined in this paper. The stability coefficient K increased nonlinearly with increasing cohesion, which was in line with the progressive failure mode of the soil slopes.

Due to the influence of reservoir water level, rainfall and geological conditions, the Three Gorges Reservoir area is a landslide hazard-prone area, and the landslide genesis mechanism and evolution process are also extremely complex.By taking the Xinpu Xia'ertai landslide as an example, this paper summarizes and analyses the resurgence law of large palaeo-landslides based on multiple sources of data, such as GPS displacement monitoring data, fracture data, rainfall and reservoir water level, and through a geotechnical creep compression model. The paper also verifies the mechanism of fracture formation on the trailing edge of the displaced landslide.The results show the following: ①Rainfall is the dominant factor of landslide deformation. Landslide deformation causes the landslide body to produce cracks and form rainfall infiltration channels, which intensifies rock fragmentation and weak layer mudification and reduces landslide stability; besides, concentrated and continuous rainfall can destabilize landslides. ②By comparing the predicted value of the model with the surface monitoring data, it is feasible to take annual rainfall as the controlling factor in the medium- and long-term landslide prediction model and help to improve the prediction accuracy of landslides. ③Pushing landslide trailing edge cracks consist of landslide pushing displacement and geotechnical body compression. In this paper, the compression creep model is introduced to calculate the crack width and compare it with the monitoring data. This shows that the compression creep model is suitable for this type of slope, and the average deformation modulus of the geotechnical body is obtained by applying the backpropagation of the geotechnical body creep compression model. Thus, we judge the degree of rock fragmentation, which provides a reference for landslide stability analysis and subsequent engineering management.

In the progressive failure process of multiple landslides, different parts of the slip zone have different yielding degrees and failure modes with different strength parameters. Under strong rainfall conditions, water-filled tension cracks generated on the slope surface give rise to hydrostatic pressure. The current widespread transfer coefficient method, which takes the same strength parameter for different locations of the slip zone, also has not yet taken into account the hydrostatic pressure effect. In this paper, we propose an improved transfer coefficient method which takes into account the hydrostatic pressure effect and the difference in strength parameters of different parts of the slip zone. The results show that, compared with the calculation method without considering the hydrostatic pressure and the difference in strength parameters in different parts of the slip zone, the anti-sliding force calculated by the improved transfer coefficient method is relatively small, the residual sliding force is relatively large, and the stability coefficients of landslides at all levels are reduced by approximately 33.26%, 17.92%, 24.95% and 16.94%, respectively. Based on the high stability coefficient before the improvement, it may lead to insufficient safety reserve of the retaining engineering. The improved transfer coefficient method proposed in this paper can provide a safer reference for multiple landslide disposal.

To study the deformation destruction mechanism and stability of the Middle Pleistocene ice-water sediment landslide in the western Sichuan Depression, this paper takes the K1887+350 landslide in the Chengdu-Yaan section of the G5 Beijing-Kunming Expressway as an example. Engineering geological surveys, physical and mechanical tests, and comprehensive monitoring are applied. Based on the actual deformation of the landslide, the paper analyzes the deformation and destruction mechanism of the landslide and studies the stability of the landslide before and after the reinforcement treatment and comprehensive monitoring technology. The results show that an unfavorable geological structure, slope toe, and precipitation induction are the main reasons for the deformation and instability of the K1887+350 landslide. The swell ability of fine-grained soil in the Middle Pleistocene ice-water sediment layer further reduces the soil shear properties. The long-term infiltration of atmospheric rainfall eventually leads to the superficial creep-pull deformation of ice-water sediments. Surface crack monitoring is an effective way to judge the current state of a mountain and analyze the stability of a landslide.

With the rapid development of economy, there is a huge demand for sand and gravel, and the development of marine sand has become a current hot spot. The east exit of Qiongzhou Strait is rich in marine sand resources, and its resource potential is in the billions of square meters. This paper evaluates the suitability of exploitation and utilization of marine sand in the east exit of Qiongzhou Strait.Six indicators of mud content, sand content, grain size, sea sand thickness, water depth and offshore distance are considered.The collected data are analyzed using analytic hierarchy process, where in the weights of considered indicators are calculated and superimposed based on constructed judgment matrix and ArcGIS spatial analysis. Furthermore, the study area are divided into five grades of exploitation suitability. It is found that the marine sand in the shoal area has the best exploitation suitability because of its large scale, good quality, shallow water depth and little influence on mining environment.In addition, this paper analyses the influence of different indicators on the suitability of marine sand exploitation. In the shoal area, the thickness and sand content contribute greatly. In near shore bay, environmental impact is the main factor. In the deep trough area, the water depth becomes the main restrictive condition for marine sand exploitation. Finally, this paper establishes a marine sand exploitation and utilization suitability evaluation system based on key factors of natural property of resources, technical conditions of exploitation, ecological environment impact and administrative management.

It is still a difficult problem to determine the sliding surface of a rock slope quickly and accurately because the efficiency and accuracy cannot be met at the same time in traditional searching methods. The limit equilibrium method is widely accepted in the stability analysis of rock slopes. The planar shear sliding model of a rock slope is adopted to characterize the position of the potential sliding surface by the inclination of the sliding surface; the analytical solution of the potential sliding surface of a multistage rock slope under the condition of limit equilibrium is derived based on the extreme value method, and its accuracy is verified combined with the Sau Mau Ping slope in Hong Kong. Furthermore, the system stability of the Dayingpanshan slope in Yibi, Sichuan Province with multiple steps in a highway is analysed. The results show that the slope potential sliding surface inclination determined by this method is in agreement with the practical sliding inclination of the Sau Mau Ping slope. In practical engineering applications, the dip angles of the sliding surface obtained by using the Cuckoo search method and simulated annealing method in Slide software are 38.0° and 37.0°, respectively, and the dip angle obtained by the analytical method in this paper is 34.8°.The Janbu method, Morgenstern-Price method and Sarma method are selected to calculate the corresponding stability coefficients, the results are approximately 1.04. The stability coefficient obtained in this paper is 1.15. The results obtained by this method are basically accurate. Through parameter sensitivity analysis, it is found that with the increase in cohesion, the inclination angle of the slope slip surface decreases, and the stability coefficient also increases. When the internal friction angle increases, the slope slip surface inclination and stability coefficient also increase.

Aiming at the scientific problem of transmission line foundation freeze-thaw failure in frozen subsoil, this paper takes an assembled foundation with cone tubes and slabs as the research object. The research method of the indoor model test and analysis is adopted, and a series of freezing tests and uplift loading tests of the model foundation are carried out under different ambient temperatures. The distribution characteristics of the temperature field and displacement field of the foundation and the relationship between the ultimate uplift capacity and temperature are analysed. Simultaneously, the failure mode of the frozen soil foundation under uplift load is also revealed. The research results show that in the freezing test, the displacement of the model foundation is less than the frost heave displacement of the surrounding foundation soil; the closer the distance from the foundation is, the stronger the frost heaving anti-restraint effect of the foundation is.In the uplift loading test of the foundation under different freezing ambient temperatures, the ultimate uplift capacity increases approximately linearly with the decrease in the ambient temperature, and the increase rate is close to 1.8 kN/℃. Under the double action of freezing and uplift, the foundation soil first exhibits local tensile failure, and with the increasing uplift load, the foundation soil gradually transitions from local tensile failure to overall shear failure. The results of this paper can provide a theoretical basis and practical experience for the application of this type of foundation in frozen subsoil.

With the development of computer vision technology, studies on landslide identification have gradually been carried out by means of deep learning. By introducing the dual attention model, an optimization algorithm for landslide image recognition based on a convolutional neural network is proposed in this paper. Based on 2 200 landslide image datasets, this paper discusses the effects of 10 network structures and 4 attention models on landslide recognition results. The effectiveness of this method is verified by using a 4∶1 training set and test set for landslide recognition. The results show that the ResNet structure performs better than other network structures. For this example, the ResNet-101 structure has the highest recall rate, precision rate and F1-measure. Compared with a single neural network, the convolutional neural network with a dual attention model has a higher accuracy of landslide identification, and the segmentation result of the landslide boundary is closer to the real landslide boundary. Among them, the ResNet-101+DAN model is the optimal model. In contrast, a single neural network cannot overcome the influence of the image noise, and the result of the image segmentation is poor.

Translational rockslides are an important disaster that endangers the safety of mountain towns. The dip slopes with weak interlayers are the areas prone to translational rockslides. The regional translational rockslide susceptibility assessment should consider the sliding mechanism and spatial distribution uncertainty analysis of the weak interlayer. Taking Tiefeng Town of Wanzhou District as the study area, based on the detailed investigation of the material, structure and spatial distribution of weak interlayers, this paper analysed the evolution mechanism of shale and mudstone developing into sliding surfaces under the action of primary deposition, tectonic deformation and supergene transformation and summarized the deformation and failure mechanism of translational rockslides. Considering the spatial distribution uncertainty of the weak interlayer, a calculation model of the vertical distribution of the weak interlayer and the contribution of the weak interlayer to slip control in the effective control depth are proposed. The key factors that characterize the sliding structure, including the type of weak interlayer and the contribution degree of the weak interlayer, are selected as susceptibility assessment factors. In addition, four elements, topography, slope structure, hydrogeology and human activities, are considered. The susceptibility of translational rockslides in the study area was assessed with slope units adopting the analytic hierarchy process. The investigation and assessment results show that the mud interlayers of the Jurassic Zhenzhuchong Formation and the shale layer of the Ziliujing Formation are the main potential slip surfaces of the translational rockslide in the study area. The extremely high susceptibility area and high susceptibility area accounted for 9.7% and 25.8%, respectively. The distribution of the underlying weak interlayer and the excavation of the slope units are the main factors affecting the susceptibility to landslide disasters. Human activities such as house building and road excavation are the main triggering factors of translational rockslides.Compared with the susceptibility assessment results without considering the factors of the weak interlayer, the results of the method proposed in this paper are more consistent with the facts.

The theory of regional groundwater flow proposed by Tóth provides a quantitative analysis approach for the study of basin-scale groundwater circulation. This paper summarizes the development of the theory of regional groundwater flow from four aspects, compares the description of the theory of regional groundwater flow in foreign hydrogeology textbooks, and systematically summarizes the evolution of descriptions in the theory of regional groundwater flow in the four editions of the textbook "Fundamentals of hydrogeology" in Chinese published from 1986 to 2018. It is concluded that the textbook "Fundamentals of hydrogeology" plays an important role in promoting the study of regional groundwater flow in China. This paper also puts forward some scientific problems to be solved in the theory of regional groundwater flow and some suggestions to guide more young students to conduct research in this field.

Objective Many important discoveries have been made in shale gas exploration in the Lower Carboniferous Luzhai Formation in the central and northern Guizhong Depression, southern margin of the Xuefengshan Uplift, and commercial test production has achieved successful gas ignition. However, the structure and evolution of the depression in this area have not been clearly defined, which restricts an accurate understanding of the formation conditions for organic-rich mud shale, the distribution of favourable sedimentary facies zones, and shale gas enrichment law. Methods Taking the Rongshui area as an example, this paper studies the main structures and their relationships with shale gas preservation through geological investigation and analysis, 2D-3D seismic section structural interpretation, evolutionary equilibrium section interpretation and other technologies. Results It is believed that there are three main faults and four main NE-NNE synclines in the study area. The preexisting NNE-trending Sanjiang-Rong'an fault is the main factor involved in extensional fault depression and compression-strike-slip transformation. In the study area, the extensional fault depression developed in the Late Devonian, strengthened in the Early Carboniferous and stopped in the late Early Carboniferous. The compression-strike-slip effect of the depression reconstruction developed in the Indochinese and Yanshanian stages, and the local tensioning effect developed in the Alpine stage. The main part of the present fold system was formed in the Indosinian period. Influenced by the increasing thrust of the Sanjiang-Rong'an fault from west to east, the structure pattern of broad and slow synclinal-compound synclinal-faulted folds is distributed. Complex synclines are favourable structural units for shale gas preservation, and the favourable structural styles for shale gas preservation are synclines and anticlines. Conclusion This understanding clearly defines the direction of shale gas exploration and deployment in the next step, and provides a beneficial idea for the structure and evolution of the Liucheng slope in the north-central part of the Guizhong Depression.

Objective The aperture of fractures (hydraulic equivalent aperture of fractures) of rock fractures is one of the key mechanical parameters of rocks.It has significant indicative significance in water conservancy projects, geological surveys and so on.At present, large-scale test methods such as cross-hole tests are often used to obtain the fracture apertures of deep rock masses in the field, but this method is rarely used many times in projects, and it is difficult to analyse the spatial variation in the aperture of fractures. This spatial variation is precisely what we need to focus on and discuss because it affects the accurate definition and application of the hydraulic equivalent fracture aperture in engineering applications. Methods In this paper, taking the surrounding rock of an underground power station cavern on the right bank of the Three Gorges Dam as an example, a new inversion method for determining the hydraulic equivalent aperture of fractures is proposed by using conventional single-hole water injection test data and three-dimensional fracture network simulation. The statistical data obtained from the measured fracture cataloguing data are used to carry out random simulation of fracture characteristics, and a three-dimensional discrete fracture network seepage model connected with water injection test boreholes is constructed to fit the relationship between the single-hole steady-state flow rate and injection. The hydraulic equivalent apertures of fractures at different depths of rocks are inverted. Results The results show that the hydraulic equivalent aperture of fractures in the research area is generally 0.07-0.30 mm, which confirms to the statistical characteristics of the log-normal distribution. Most of the inverted hydraulic equivalent apertures of fractures in boreholes decrease exponentially with burial depth, while a few boreholes show strong randomness of the hydraulic equivalent aperture of fractures and no obvious change with burial depth. Conclusion Compared to those of traditional methods, the inversion results of this approach are significantly different and require further verification.

Objective Knowledge of the regional groundwater level is an important foundation for groundwater resource evaluation and protection. Due to the limited amount of groundwater level data available at the regional scale, Kriging interpolation and deep learning methods are gradually being used for regional groundwater level prediction, but their applicability and robustness lack comparative analysis. Methods In this paper, spatial interpolation of groundwater levels in the Shenzhen-Shanwei Special Cooperation Zone was carried out using ordinary Kriging, coKriging and deep learning methods to explore the potential of these three methods for practical application to regional groundwater level prediction. To investigate the effect of the training set sample size on the prediction effect of the three methods, 239 monitoring wells were divided into two groups of 76 and 163 wells for the training of the three models. Results The results showed that the RMSEs were 6.09, 4.04, and 7.11 when the training data of 76 wells were used to fit the validation set, and the Kriging method, which accounts for surface elevation information, was significantly better than the ordinary Kriging method and the deep learning method. In addition, the predicted water level distribution improved when a larger number of samples was used to predict the water level in the region. However, the spatial distribution characteristics still differed significantly. Conclusion The results show that when the observation data are sparse, the prediction effect of coKriging with elevation information is significantly greater than that of ordinary Kriging and deep learning methods, while the RMSEs obtained by the three methods are similar when the amount of observation data increases to a certain amount.

X gas field is located in the central inversion structural belt of Xihu Sag, East China Sea Basin.The main target layer H4 is in shallow water delta sedimentary environment.The dominant frequency of seismic data of the gas field is low (25 Hz), while the buried depth of H4 layer is large (3 300-3 400 m).The reservoir has low porosity and low permeability, and the consistency of sand body thickness predicted by conventional seismic inversion is low.Aiming at the characteristics of full coverage of 3D seismic data and less drilling in X gas field, this paper makes up for the lack of sample points in SVR algorithm through forward and inverse modeling under the guidance of geological model and setting up virtual wells.Then, by extracting seismic attributes and optimizing sensitive attributes characterizing sand body thickness, SVR algorithm is used for multi-attribute fusion to complete the quantitative prediction of H4 sand body.Based on the reservoir prediction results, it is proposed that H4 layer is a distributary channel deposit of shallow water delta meandering flow type, and further completed the dissection of sand body deposition model.After the development adjustment wells drilled, the coincidence between the actual drilled sand body thickness and the predicted sand body thickness is more than 84%.This paper explores and obtains the quantitative reservoir prediction scheme of SVR algorithm constrained by geological model under the condition of few wells on the sea, which completes the accurate prediction of the middle and deep distributary channel reservoir in X gas field, and also has certain guiding significance for the reservoir description of the same type of oil and gas fields.

Due to the high concealment, short-lived time and low predictability of the rock avalanche, it is difficult to visually observe the process of it. In order to study the dynamic characteristics and the catastrophicto houses of rock avalanche, this paper analyzes the rock avalanche congeries and its particle size distribution.Taking the rock avalanche in Pusa Village as an example, this paper uses the PCAS system to identify congeries particles by image.And through the dimensional analysis method, the quantitative relationship between the congeries of particles and the damage of the building is analyzed.The author found that: compared with on-site screening statistics, the data obtained by the method of image recognition of congeries particles is more comprehensive and detailed, and can save a lot of manpower and material resources.In addition, the interaction between the house and the rock avalanche is explored, and it is found that the house has the effect of "blocking coarse and fine discharge" on the rock avalanche particles. At the same time, using the particle size data obtained by image recognition to derive the discrimination formula for building damage, the discriminating effect is good, laying the foundation for follow-up research.

Changde-Anren fault is a large NW-trending fault in eastern Hunan Province.Based on a large number of basic geological data, this paper summarized the segmental characteristics of the fault; according to the oringin and distribution of Indosinian granite in the fault zone, the paper suggests that the activity of the fault in the main episode of Indosinian movement in the Late Middle Triassic was segmented.According to the structural characteristics of the fault and its two sides, the exposed strata and magmatic rocks, the Changde-Anren fault can be divided into four segments such as Anren-Hengshan segment (Ⅰ), Xiangxiang segment (Ⅱ), Taojiang segment (Ⅲ) and Changde-Shimen segment (Ⅳ), between which are NE-trending deep faults that cut through the deep crust and even the mantle.The NE-trending deep faults were mainly formed in Caledonian movement with sinistral strike-slipping, and cut the Changde-Anren fault into several disconnected segments, which resulted in the segmentation of the movement in Mesozoic of the Changde-Anren fault.In the region, the Late Triassic granites are mainly S-type granites formed by deep crustal melting in a post-collisional environment.The distribution characteristics of Late Triassic granites in the Changde-Anren fault indicate that the activity of the fault in the main episode of Indosinian movement is obviously segmented: there occurred shearing of the Xiangxiang segment of Changde-Anren fault in the deep part in Middle Triassic Indosinian movement, when the movement amplitude, shear strength and corresponding warming effect decreased from the middle to the end of the segment for the end restriction, which caused that the decompression-melting of deep crustal in Late Triassic only occurred in the middle part of Xiangxiang segment, and the corresponding granites were exposed in the middle and northern sections of Xiangxiang segment.This structural-magmatic mechanism is also reflected in Anren-Hengshan segment and Taojiang segment.The segmental movement of the Changde-Anren fault in Indosinian is a "passive" segmental movement after the first penetrating fault was divided into several segments by the NE-trending deep fault, which is different from the general "active" fault segmental movement or segmental growth with many small faults occurring, expanding and finally being connected into a large fault.

With the deepening of global oil and gas exploration research, the North Atlantic polar region has gradually become the frontier of oil and gas exploration, but the exploration degree of Jan Mayan micro-continent is very low.The study on stratigraphy, structures and tectonic evolution modelling of the Jan Mayan microcontinent (JMMC)is presented in the paper based on seismic, gravity and magnetic data newly acquired by CNOOC in its contract area and other new published papers which show the most update progress of the JMMC. Located in the central part of the Norwegian-Greenland Sea of the North Atlantic, the JMMC is conjugate with the Jameson Land Basin on the Greenland continent margin and the Vøring Basin on the Norwegian shelf margin of the Beltic Continent in accordance with similar Paleozoic-Mesozoic stratigraphy. The JMMC extends southwards from the Jan Mayan fracture zone towards northern Iceland and its architecture shows the characteristics of detachment faults which is similar to the Mesozoic fault system of the Vøring Basin. The distribution of SDR, volcanic intrusion and explosion can be interpreted on the seismic data which indicates the JMMC is the distal domain of the volcanic passive margin in the North Atlantic mostly during the Cenozoic age. The tectonic evolution model is setup by analogic basin analysis and is supposed to start from the Paleozoic-Mesozoic orogeny to rifting, and then be influenced by the twice seafloor spreading of the age 55 Ma and 25 Ma. The first seafloor spreading of 55 Ma age caused the continental crust break-up and formed the volcanic passive margin between the Greenland and Beltic, especially the JMMC's separating from the conjugate Norwegian shelf margin. The second seafloor spreading of 25 Ma age caused the oceanic ridge jump due to the Iceland mantle plume drifting off the Greenland and also caused the JMMC's separation from the Greenland Continent as an 'abandoned orphan' floating on the oceanic crust. The meaning of this study is to discuss kinematic evolution of residual continental crust detached from the distal domain of the plate and to indicate lithospheric extension and break while the embryonic oceanic crust generating through the detachment movements and mantle upwelling.

Basalt platform is a special type of landslide, however, its stability has received little attention before.This paper takes the Diyayuan landslide in Shengzhou city as the research object, and uses the method of three-dimensional numerical simulation to analyze and evaluate its stability.Then the rainfall recurrence period was determined based on the P-Ⅲ distribution curve, and the geotechnical software MIDAS was used to simulate the landslide stability and the 3D motion simulation platform DAN3D software was used to calculate the landslide impact range; finally, sensitivity analysis was carried out for the stability factors affecting the landslide The results show that different rainfall intensity has great influence on the stability of Diyayuan landslide.At this time, the stability coefficient of landslide is 0.946, the failure probability is 65.25%, and the maximum impact range increases by 36.83%; the angle of internal friction and rainfall are the main factors affecting the stability of Diyayuan landslide The analysis shows that the stability of basalt platform landslide is obviously correlated with the development of diatomite slip zone, joint and fissure surface, and the hysteresis of rainfall infiltration.The results of this paper can provide reference for the stability evaluation of similar landslide.

At present, there are more than 190 craters have been confirmed on the earth, and most of the simple impact craters with a diameter of less than 1 km are formed by iron impactor.There is a large amount of iron meteorite material around the impact crater struck by the iron impactor.The spatial distribution characteristics of iron meteorite are of great significance for studying the impact process and mechanism of the crater.The enrichment of iron can also be used as important information to explore suspected impact craters on the Earth's surface.In order to obtain iron meteorite fragments around the impact crater, field investigations were mainly conducted manually in the early days, but this method was inefficient and required a lot of manpower and material resources.Based on the unique spectral characteristics of the meteorite, the spatial distribution characteristics of the meteorite material around the impact crater can be easily obtained by using the remote sensing alteration information extraction method.This paper selects Barringer Meteor Crater in Arizona, USA as the research object, considering of the spectral characteristics of iron meteorite, and using Band Math-PCA(principal components analysis).The extraction results fit well with the field survey of the distribution of iron meteorites by the predecessors.The iron meteorite aggregation area on the east, southeast and southwest sides of the impact crater was well reflected in the extraction results.The iron meteorite around the impact crater was well extracted, and the iron meteorite gathering areas on the east, southeast and southwest sides were well reflected on the extraction result map.It shows that it is feasible to use the principal component analysis-band ratio method to extract the iron meteorite information around the Barringer crater.The experimental results accurately obtained the spatial distribution information of iron meteorite around the impact crater.This paper provides a feasible plan for exploring the ring structure of the impact on the earth's surface, and provides an important method reference for the extraction of similar impact craters in the future.

Gravitational decollement is a structural pattern commonly developed in passive continental marginal basins on both sides of the Atlantic Ocean.Two different types of gravity decollement structures with transitional salt and marine mudstone as decollement layers are developed.Based on the stress mechanism, it can be divided into extensional zone, transitional zone and compressional zone successively from the continent to the ocean.In order to clarify the difference between those two types of gravitational decollement structures and their influence on oil and gas accumulation, this paper makes a comparative analysis of two representative basins, the Lower Congo-Congo Fan Basin and the Niger Delta Basin.Through comparing, the differences of structure patterns, sedimentary reservoir distribution characteristics and hydrocarbon accumulation were clarified in the same zone.On the whole, salt gravitational decollement in extensional zone shows that the salt structures are highly active, the oil-gas accumulation conditions are superior, and there are many oil-gas discoveries in this zone.In transitional zone, the intensity of salt activity is moderate and the degree of oil-gas enrichment is the highest.In compressional zone, the salt activity is strong with a large scale salt accumulation, poor source rock and reservoir, and rare oil-gas discoveries.The extensional zone of marine mudstone gravitational decollement is the main oil-gas accumulation area with relatively weak structure activity and good match between the reservoir and source rock.In transitional zone, it has strong extrusion stress, and large amount of mudstone has been accumulated there.The mud diapir is magnificent, and deep-slow diapir structure is the favorable oil-gas accumulation area.The compressional zone is dominated by typical thrust imbricate structure with good match of source rock, reservoir and oil source faults.The oil-gas enrichment in this zone is relatively high.Based on the analysis of those two types of gravitational decollement in source rock, reservoir and hydrocarbon accumulation, this paper have provided some references for the research related to gravitational decollement.

Significance Impregnated diamond bits (IDBs) have been widely used in various hard rock drilling activities, especially deep drilling. Drilling process with IDBs relies on diamond edge wrapped by metal matrices to break the rock formation, which means the wear pattern of the diamond bit reflects the interaction between bits and rock, as well as the existence form of broken particles, which directly determine the drilling efficiency and service life of the drilling tools. But up to now there have not been so much in-depth study on its wear mechanism and analysing method in geological drilling. Progress and Analysis Therefore, this paper reviews the research literature on IDBs wear in the field of geological drilling, summarizes the abnormal bit wear problem according to engineering project experineces and industrial standards. Firstly, based on the experiences of geological drilling activities and industry standards, different types of abnormal bit wear of drill bits were summarized. Then, the evaluation methods of drill bit wear were introduced from the aspects of wear images and drilling signals. The wear mechanism and influencing factors of the drill bit in the drilling process were sorted out from three aspects: The overall drill bit, diamond, and metal matrix. In addition, mainstream methods of controlling drill bit wear performance were listed, and the research progress of wear analysis equations was introduced, besides, how machine learning methods can assist in the study of drill bit wear was discussed. Conclusion and Prospect Thus, IDBs have great potentials in deep hard rock drilling, and their wear performance is the key influnencing the whole drilling activity. To this end, research directions such as artificial intelligence assisting data analysis, microscale computational simulation, additive manufacturing, and material processing modification were analyzed and discussed, aiming to explore advanced methods for monitoring, analyzing, and regulating the wear of diamond drill bits, so as to meet the needs of remote monitoring and controlling in drilling activities such as geological deep drilling and extraterrestrial drilling.

Objective To reveal the structures and evolutionary patterns of faults in the central and northern parts of Tazhong Uplift, Tarim Basin, Methods this paper systematically discusses the types of fault structures, geometric characteristics, differential activity mechanisms, and tectonic evolution processes in this area by analysing detailed structural interpretations and coherent slices of combined large 3D seismic data along with the regional dynamic background. Results The results show that there are 4 types and 7 evolution stages of faults in the central and northern parts of Tazhong Uplift, among which thrust faults and strike-slip faults are particularly common. On the plane, NW arc thrust faults intersect with NE-, NW- and NS-striking strike-slip faults; vertically, the fault stratification and differential activity characteristics are obvious. In the Lower Ordovician and the belowing layers, faults developed in large numbers and were mainly linear in their trending directions. As for the Middle Ordovician-Middle and Lower Devonian layers, faults are mostly in the echelon type. In the Upper Devonian-Permian layers, a few faults developed in the Tazhong Ⅱ fault zone and the southwestern end of the Shunbei 5 fault zone. Conclusion The fault activity in the study area was controlled by stress sites exhibiting diverse properties across multiple phases and directions and experienced an extremely complex evolutionary history: In the Early Caledonian period, a small number of normal faults, such as the Tazhong Ⅱ fault zone, were mainly active; in the Middle Caledonian Ⅰ period, the fault activity was very strong and was characterized by coevolution and mutual coupling of thrust faults and strike-slip faults. The strike-slip faults obviously cut or restricted the thrust faults. The fault activity of the Middle Caledonian Ⅲ period basically inherited the tectonic framework of the Middle Caledonian Ⅰ period, but the characteristics of transtensional fault activity in the Shunbei 4 and 5 fault zones are significant. From the Late Caledonian to Early Hercynian, some of the faults inherited activities with obvious transtensional characteristics. Conversely, in the Indochina-Yanshan period, only a few faults inherited activity, and the development area of transtensinal fault is further expanded to the south. During the Himalayan period, the tectonic movement of this area was relatively stable, and the complex fault structures that formed in the early stage transitioned into the deep burial stage.

Objective The Côte d'Ivoire Basin, which is located in the equatorial section of West Africa and features large-scale strike-slip transform zones, is a typical transformed passive continental margin basin. This area is currently a hot spot for oil and gas exploration and has great exploration potential but has an uneven distribution of hydrocarbons both horizontally and vertically. Methods Based on previous results, well data, seismic data and new discoveries, this paper focuses on the differential controls of hydrocarbon distribution from two perspectives: structure and sedimentation. Results The results show that the basin has experienced three main tectonic-sedimentary evolution stages, namely, intracontinental rift, ocean-continent transition, and passive margin, forming the "narrow west-wide east" axe structure. The basin has a narrow and steep transform margin in the west, a wide and gentle divergent margin in the east, and a transitional margin in the central region, which controls the overall oil and gas distribution of "less in the west and more in the east" in macro-scale. The main response area of the strike-slip transformation stress in the central transitional margin and the central uplift developed many structural traps, which were sourced from both the northern and southern depression and ultimately controlled the distribution of the Albian oil and gas reservoirs. Conclusion The palaeomorphology formed by the strike-slip transform zone plays an important role in controlling the spatial distribution of both the Upper Albian-Cenomanian reservoirs in the early stage and the Turonian reservoirs in the late stage. The stepped or intra-slope ponds on slopes formed by strike-slip transform zone are often the most favourable sand-rich places and benefit stratigraphic-lithologic traps. Additionally, the distribution of oil and gas reservoirs has good consistency with the distribution of sedimentary systems; that is, the transformation controls the reservoirs, and the distribution controls the oil and gas reservoirs.

Objective An enhanced geothermal system (EGS) is a crucial means of extracting thermal energy from hot dry rock reservoirs, and the pattern of well plays a key role in influencing heat extraction efficiency. Currently, there is limited research on pattern of well considering fractured reservoir exploitation models. Methods This paper establishes a numerical model for heat extraction from hot dry rock fractured reservoirs and analyses the impact of four different patterns of wells on EGS heat extraction performance through a comparative analysis of the temperature decrease of the bedrock, heat extraction rate, production temperature, and heat extraction power. Results The results indicate that, compared to vertical wells, horizontal wells have a larger area for fluid heat exchange, allowing for more efficient heat development between fractures. After 30 years of production, considering the case of hydraulic fracturing fracture connectivity, the one injection and two production schemes of horizontal wells exhibit the highest heat extraction efficiency. In the vertical well direction, the temperature influence range is approximately 690 m, with an average temperature decrease of 38.09 K in the bedrock, a heat extraction rate of 24.42%, and a heat extraction power of 3.5 MW. Conclusion The research results provide a theoretical reference for enhancing the heat production of geothermal systems and achieving efficient and sustainable development of hot dry rock resources.

Objective The embedded granularity of target minerals refers to their particle size and distribution in ore, which directly influences the design and effectiveness of ore beneficiation processes. Therefore, the measurement of embedded granularity of target minerals is a crucial task in process mineralogy research. In traditional process mineralogy research, the main method for observing and analysing ore samples is to use a polarized light microscopy. However, this approach generally suffers from problems such as long processing times, susceptible to subjective factors, and difficulties in achieving automation and large-scale applications. To overcome these limitations, this paper proposes a method for detecting the embedded granularity of metal minerals under the microscope based on based on deep learning. Methods This method takes specimens from the Shuichang magnetic ore deposit in Tangshan City, Hebei Province as the object. We take photographs under the reflected light conditions using a polarized light microscope to create a dataset, and design a mineral recognition network model based on the Deeplabv3+ network. Thereby it enables automated feature extraction and intelligent recognition of the target metal minerals. This method achieves segmentation of the target minerals by generating binary images of the desired metal minerals. Finally, the analysis and measurement of the embedded granularity of the target metal minerals are completed by combining the maximum Feret diameter. Results Compared with traditional manual microscopic measurement methods, the application of image measurement based on deep learning in mineral particle analysis has increased the processing speed by approximately 119.8 times and the measurement accuracy 169.5 times when measuring the same mineral particles, demonstrating its significant improvement in terms of processing efficiency and measurement accuracy. Conclusion The deep learning-based method for detecting the embedded granularity of metal minerals under a microscope significantly reduces the detection time and enhances the detection accuracy for mineral embedded granularity. Moreover, it eliminates the influence of subjective factors, which is of great significance for promoting the intelligent development of process mineralogy.

Objective To reveal the deformation evolution of the Xinhua landslide in Luding County, Sichuan Province under the comprehensive effects of reservoir impoundment, reservoir water level fluctuations and seasonal rainfall, and to explore the progressive cumulative effect of the strength degradation of the landslide rock and soil mass under the coupling of multiple factors. Methods In this paper, based on a field investigation and multisource long sequence monitoring data analysis of the Xinhua landslide in the reservoir area of the hydropower project, combined with the three-stage evolution characteristics of the landslide cumulative deformation-time (S-t) curve and the measured S-t curve of the Xinhua landslide, the evolution stages of the three-step deformation cycles of the Xinhua landslide are identified and divided. At the same time, the improved tangent angle method is used for calculation and analysis, and a quantitative classification standard for Xinhua landslide classification early warning based on the improved displacement tangent angle early warning threshold is constructed. Results The results show that the short-term large increase of water level during the initial impoundment period, the rapid decrease of water level during the reservoir operation period and the influence of seasonal heavy rainfall are the main factors to accelerate the deformation of the Xinhua landslide. Conclusion According to the analysis and discussion, the improved displacement tangent angle early warning threshold can provide guidance for identifying the current stability state and potential risks of the Xinhua landslide to a certain extent, but multiple early warning indicators should still be considered, and the signs of macroscopic deformation and failure of landslides should be integrated for judgement.

Since 2020, with in-depth research on the Shuangji structural belt in the Jimsar Depression, Junggar Basin and high-yield oil flow data obtained from the Triassic Jingjingzigou Formation in the Well Satan 1, it has been demonstrated that the Jimsar and Jinan depressions have promising potential for conventional oil and gas exploration. Objective To further study the geological characteristics and exploration potential of the Jimsar and Jinan depressions, Methods this paper comprehensively analyses data from core samples, logging, well logging, and seismic surveys; identifies regional unconformities; categorizes different tectonic stages; and establishes the correlation between tectonic and stratigraphic evolution. Based on this, the development process of each stratum is restored, and the coupling relationship between tectonics and the evolution of uplift and depression within the research area is established, and the prototype basin is restored. Results This study revealed five large unconformities in the Jimsar and Jinan depressions, which have undergone four episodes of tectonic activity. The stratigraphic evolution characteristics of the study area ranged from "north high and south low" in the Early Permian to "south high and north low" in the Palaeogene and Neogene. The original basin also changed from a "multiconvex and multiconcave" pattern in the Early Permian to a "few convex and large concave" structural pattern in the Palaeogene and Neogene. Conclusion The establishment of the coupling relationship between tectonics and the evolution of uplift and depression at different times and the restoration of the prototype basin during each period lays an important foundation for clarifying the basin characteristics of the Jimsar and Jinan depressions during different periods and helps to enhances oil and gas exploration in these areas.

The Qianyingzi Coalmine is located on the west of the Suxian Mining area of the Huaibei Coalfield, adjacent to the outer edge of the southern segment of the Xu-Su Arc Nappe Belt. Methods Based on the latest geological exploration and production data, this paper analysed the structural framework and coal-controlled structural patterns of the Qianyingzi Coalmine, divided the tectonic stages, and discussed the geotectonic background of the coalmine structures, Objective which provides an important geological basis for the understanding of the tectonic deformation and evolution of the coalmine, the geodynamic mechanism and the prediction of exploration directions. Results The results show that the Carboniferous-Permian coal-bearing formations in the mine are generally a gentle syncline with an NNE-trending axis. The faults in the mine are well developed, and the number of reverse faults is greater than that of normal faults. Both of these faults are mainly NE to NNE, followed by NS. The structural framework of this mine is significantly controlled by several large NS to NE-striking faults and is segmented from west to east by major faults, including the Nanping, F22, F17, DF200 and Shuangdui faults, which exhibit the characteristic of east and west zonation. The coal-controlled structural patterns in the mine can be classified into three types, namely, compressional, extensional and strike-slip. And the coal-controlled patterns can be further divided into nine subtypes, namely, thrust drag folds, hedge structures, pop-up structures, imbricate structures, grabens, horsts, step faults, positive flower structures and pinnated en-echelon structures. The analysis of structural combinations shows that the F17 fault has not only thrusting motion but also significant transcurrent activity. Conclusion The structural deformation of coal-bearing formation in the Qianyingzi Coalmine can be divided into five stages: the Fengjia Syncline with an NNE-trending axis, nearly NS-striking reverse faults, NNE-striking reverse-sinistral faults and NE-striking reverse faults, nearly NS-striking normal faults, and NW-SE-striking normal faults. Combined with the results of previous studies on the regional tectonic background, the first and second shortening structures in this mine are the results of foreland deformation during the convergence of the North China Craton and South China Plate and subsequent continent-continent collisional deformation during the Indosinian period. The third stage compresso-shear structures are related to the rapid oblique subduction of the Izanagi Plate toward the East Asian continental margin at the beginning of the Early Cretaceous in the Western Pacific. The fourth and fifth stage extensional structures developed against a strong extensional background in eastern China during the Early Cretaceous.

Significance To systematically address problems related to the interpretation and evaluation of image logs and expand their application range in geology and engineering fields, firstly, the development history, data processing steps and interpretation process of image log acquisition series are reviewed, and then fine interpretation methods for image logs, constrained by "four levels" (direct interpretation of images, conventional logging constraints, core constraints and geological theory constraints), are proposed in this paper. Progress The image log facies models can be divided into seven categories: massive, banded, cross-stratified, spotted, convoluted, graded and symmetrical groove modes. Image logs can be used for core orientation, formation attitude acquisition, fracture evaluation, fault property analysis, in situ stress direction discrimination, sedimentary characteristic pickup, palaeocurrent direction discrimination, etc. Through the inverse calculation of Archie's formula, the image log data matrix can generate porosity spectra and apparent formation water resistivity spectra, which can be used for reservoir quality evaluation and fluid property identification, respectively. Slab images can reveal information such as sedimentary laminae, fine-grained sediment lamina textures can be identified, and high-resolution logging can be used to evaluate unconventional oil and gas reservoirs. Poro Tex image structure analysis technology can be used to identify the characteristics of reservoir spaces such as pores and fractures and to quantitatively calculate parameters such as porosity and fracture porosity. Therefore, it is widely used in comprehensive logging evaluations of highly heterogeneous carbonate reservoirs. Conclusions and Prospects These research results can help us to avoid misunderstandings in image logs interpretation and expand the application field of image logs.