Objective Shallow-water deltas are widely observed in petroliferous basins and can form large-scale hydrocarbon reservoirs. Based on the relative proportions of mud and sand in their deposits， they can be classified into three types—sand-rich， sand-mud， and mud-rich deltas—whose geomorphological expression， depositional characteristics， sedimentary architecture， and sediment heterogeneity differ substantially. At present， systematic research on these three types of shallow-water deltas remains limited， which has severely constrained the efficient exploration and development of oil and gas resources. Methods This study employed sedimentary numerical simulation technology to reproduce the depositional evolution processes of the three types of deltas. Their sedimentary architecture and grain size models were reconstructed from the simulated depositional interfaces and grain size data. Subsequently， from a detailed analysis of the evolutionary processes， sedimentary architectural models for shallow-water deltas were established and the characteristics of sedimentary heterogeneity within this model framework were elucidated. ［Results and Conclusions ］ （1） The sediment supply ratio is a crucial influencing factor in deltaic depositional evolution， as it determines the sedimentation rate and erosion resistance of channel margins. On this basis， the evolution and ultimately the resultant architecture and heterogeneity are determined. （2） As the sand-to-mud ratio decreases， distributary channels exhibit reduced quantity， hierarchical complexity and areal proportion， as well as increased sinuosity， greater stability， diminished lateral migration capacity， and a transition from lateral migration-dominated filling to abandonment-dominated filling. （3） Sand-dominated deltas typically exhibit lobate or triangular shapes， with extensively developed distributary channels forming multistage， radial patterns. They frequently display lateral migration characteristics. Sand-mud deltas manifest as multi-fingered， branching forms with fewer distributary channels that are primarily controlled by trunk distributary channels with multi-directional bifurcations at their termini， creating multiple laterally amalgamated finger-like bar assemblages. Mud-rich deltas possess few distributary channels， being characterized by the development of narrow， sinuous， belt-like trunk distributary channels lacking lateral accretion features. These channels are predominantly infilled with muddy sediments following avulsion and abandonment. （4） Sand-rich deltas show near-continuous sand distribution with downstream fining. Coarsest grains occur in trunk channels， with finer grains in mouth bars， yielding weak planar heterogeneity but strong vertical heterogeneity due to multi-stage lateral/progradational fine-grained interbeds. Sand-mud deltas exhibit broad-banded sand bodies with coarse-grained reservoirs in trunk channels and mouth bars， weak planar heterogeneity， and strong vertical heterogeneity from muddy interbeds. Mud-rich deltas display strong planar heterogeneity， with reservoirs being restricted to mouth-bar cores that are laterally isolated by muddy channels， with weak vertical heterogeneity resulting from multi-stage muddy interbeds.

Objective The discharge rate regulates the sedimentary evolution and morphological scale of a braided river. In this study， the influence of discharge rate on the formation of braided channels， bars and internal sedimentary architecture is systematically analyzed for the first time. Methods Five groups of three-dimensional sedimentary numerical simulation experiments with different flow rates were carried out using Delft3D software to explore the evolution， morphological patterns and scale differences of braided channels and bars formed as a result of various flow rates. The models reproduce the internal architectural patterns of a range of bars developed in braided rivers with different flow rates and summarize the sedimentary characteristics and evolution of sandy braided rivers. Results （1） The rate of discharge is positively correlated with the sedimentary evolution of braided rivers. Low-discharge braided rivers exhibit limited evolution， in which bars mainly tend to migrate vertically and are less dissected by channels. By contrast， high-discharge braided rivers undergo intensive evolution， characterized by lateral migration and frequent dynamic equilibrium processes involving compound bars and dissection. （2） The discharge rate influences the plane pattern and channel depth of braided channels. As discharge increases， the braided channel becomes wider and deeper， resulting in a reduced overall number of channels but more highly developed chutes of the channel bars. Lower-discharge braided channels are shallower and primarily consist of numerous narrow， relatively fixed interwoven river networks. （3） Discharge further governs the co-evolution of channels and bars. Greater discharge enhances bar complexity， promoting the development of large complex compound bars and side bars with intricate internal stacking relationships and more frequent chutes. （4） Despite strong spatial heterogeneity in the internal architecture of channel bars in sandy braided rivers， consistent patterns emerge： all bars develop downstream accretions （DA） in the core， vertical accretions （VA） layered above， and lateral accretions （LA） deposited at the sides. A key distinction lies in the increased proportion of LA at higher discharge conditions. （5） Discharge correlates positively with accretion size but inversely with aspect ratio and flakiness ratio. Median aspect ratios of bars are 3.5 in low-discharge systems versus 4.5 in high-discharge systems. Conclusions The study proposes a positive correlation between discharge and the scale of channel bars and accretions in sandy braided rivers. This clarifies flow-controlled sedimentary characteristics and scale variations， providing a basis for analyzing complex subsurface reservoir architectures.

Objective The distribution patterns of favorable sand bodies in deltaic sedimentary systems serve as the theoretical foundation for oil and gas exploration. Traditional lobe classification and microfacies analysis methods have limitations in revealing the evolution mechanisms of the channel-lobe system， thus restricting the development of studies on lobe morphology and sand body connectivity. Methods Using the Cretaceous delta of the eastern depression of the Doseo Basin as a model， a flume experiment with a movable base was conducted. By capturing Hi-Res time-series images and sand body morphology data， and applying a new lobe classification method， an effective regional sedimentary model was established. Results （1） A consistent overlapping relationship exists between channels and lobes， where the migration， evolution， or disappearance of channels leads to the formation of new lobes. （2） Within the channel-lobe system， three main evolution mechanisms are driven by hydrodynamic strength： erosion of existing lobes， formation of lobes dominated by sandy deposition， and formation of mud layers dominated by fine-grained deposition. （3） The characteristics of channels determine the type of lobe development， whereas lobe morphology is influenced by factors such as sedimentary slope， tectonic activity， base level， and sediment source conditions. （4） The connectivity of sand bodies is affected by the constituent units of lobes， their contact relationships， lobe properties， and the types of lobe complexes. Later channel evolution can improve sand body connectivity to a certain extent. （5） The eastern depression of the Doseo Basin exhibits two sedimentary models： deep-water and shallow-water delta systems. In the deep-water delta model， the channel evolution area is larger， and connectivity improvements are more pronounced. In contrast， the shallow-water delta model features larger lobe deposition areas and wider planar distribution of lobes. Conclusions The new lobe classification method and the channel-lobe system evolution mechanism are applicable to the study of sand body connectivity and sedimentary models in the study area， and they are expected to be widely used in future delta sedimentary simulation research.

Objective The Permian Jiamuhe Formation in the Zhongguai area of the Junggar Basin contains a suite of proximal coarse clastic deposits developed during the tectonic transition from rifting to depression. However， the depositional system type， depositional model， and formation mechanism of thick conglomerates remain poorly constrained， thereby limiting hydrocarbon exploration of conglomeratic reservoirs in the region. This study aims to clarify the depositional system type of the coarse clastic succession in the Jiamuhe Formation， reveal the controlling factors governing the development of thick conglomerates， establish a depositional model， and discuss its exploration significance. Methods Based on analyses of heavy mineral assemblages， paleogeomorphologic reconstruction， and seismic profile interpretation， combined with results from tectonic evolution and fault characterization， extensive core-based lithofacies analyses were conducted. On the basis of sedimentary microfacies identification and classification， the depositional system was summarized， the geological controls on thick conglomerate formation in the Jiamuhe Formation were clarified， and a depositional model was established. Results Three subfacies—fan delta plain， fan delta front， and pro-fan delta—and nine sedimentary microfacies were identified in the Jiamuhe Formation of the Zhongguai area， indicating an overall progradational fan delta depositional system controlled by multiple syndepositional fault terraces. The depositional development was jointly governed by four major factors： （1） during the rift⁃depression transitional stage， elevated topography， abundant sediment supply， and high topographic potential energy provided sufficient coarse clastic input； （2） under arid to semi-arid climatic conditions， frequent short-duration intense precipitation triggered high-energy transport processes including flood flows， debris flows， and clastic flows； （3） continuous syndepositional fault activity generated large accommodation space， promoting sustained aggradation of thick conglomerates； and （4） the development of multi-stage fault terraces controlled the continuous progradation of subaqueous fan bodies， resulting in basin-filling conglomerate distribution. Based on these characteristics， a fault-terrace-controlled fan delta depositional model was established. Conclusions The fault-terrace-controlled fan delta represents a distinctive fan delta depositional system developed under a rift-depression transitional tectonic setting， controlled by multiple syndepositional fault terraces and characterized by sustained proximal supply of high-energy coarse clastic sediments. It exhibits continuous progradation and aggradation， the combined action of multiple high-energy transport mechanisms， and the superposition of thick， mud-poor conglomerates. This model challenges the traditional perception that “proximal source areas necessarily correspond to poor reservoirs” and provides a depositional analogue for hydrocarbon exploration of deep to ultra-deep conglomeratic reservoirs in basin depressions and slope zones， fault transition belts， and concealed fault-terrace zones in other basins.

Objective The Upper Paleozoic Yanghugou Formation-Taiyuan Formation in the northwestern margin of the Ordos Basin is a good prospect for oil and gas exploration. The strata are completely developed and continuous， with large thickness changes and various types of sedimentary facies. Defining the distribution characteristics of sand bodies and clarifying the law of sedimentary evolution directly affect the selection of preferred exploration zones for oil and gas. Methods This study takes the Yanghugou Formation to Taiyuan Formation in the northwestern margin of Ordos Basin as the target horizon. Based on previous studies， through typical field profile measurement， drilling core observation， paleocurrent direction analysis， logging data， and test data analysis， the sedimentary environment， facies type characteristics， evolution， and model of the study area were evaluated. ［Results and Conclusions］ There are 19 lithofacies types and three sedimentary systems in the study area， including four sedimentary facies types， and 13 sedimentary microfacies are further divided. The Yanghugou Formation-Taiyuan Formation in the study area is supplied by the two provenance systems of the Alxa ancient land in the northwest of the basin and the Yinshan ancient land in the northeast. The Dickinson triangle plot reveals that the tectonic background of the provenance area is dominated by the recycled orogenic belt. The characteristics of heavy mineral assemblages are clear. The northwestern margin of the basin has a clear affinity with the Alashan Group （Ar₃-Pt₁）， Archean Jining Group （Ar₃）， and the Wulashan Group （Ar_1-2）. The ZTR index shows that the unstable minerals gradually decrease from north to south； analysis of the paleocurrent direction also reflects the material sources from northwest to southeast and from northeast to southwest. Based on the above provenance analysis， paleo-sedimentary environment evolution and sedimentary facies type characteristics， it is clear that the main body of the Yanghugou Formation-Taiyuan Formation in the study area is the coexistence stage of sea and land. During the sedimentary deposition of the Yanghugou Formation， under the background of the revival of Helan aulacogen and the backlog of north-south tectonics， the sea water enters rapidly. The whole study area is controlled by the delta-clastic coastal sedimentary system. The northern source supply is sufficient， resulting in the development of tidal-controlled delta deposits in the north. Affected by tides and waves， tidal flat-barrier island-desalination of lagoons-shelf sedimentary microfacies are developed in the south. During the deposition of the Taiyuan Formation， the crust continued to sink and seawater invaded. During this period， the basin became the most widely distributed period of the sea area. The sedimentary environment was similar to that of the Yanghugou Formation. The overall performance was the coexistence of tidal-controlled delta， tidal flat， desalination of lagoons-barrier island sedimentary environment， and the erosion range in the northern region was relatively reduced， the source supply continued to increase， and the tidal-controlled delta range extended wider to the south.

Objective The Wuotuo village in Zongdi town， Ziyun county， southern Guizhou province， developed an Early Permian coral reef that is exposed with a thickness of approximately 45 m and lateral exposure of nearly 100 m. The reef displays a positive relief. It is of great importance to the study of the construction of shallow marine organisms and the paleoenvironment. Methods The coral reef in this area was systematically studied from the perspectives of paleontology and sedimentary petrology. Results The fusulinids collected from the reef indicated an Early Asselian age. The primary reef-building organism was identified as the fasciculate colonial coral Fomichevella， whereas biotic compositions of the coral reef included foraminifers， brachiopods， gastropods， and calcareous algae. The coral reef in Wotuo village and its underlying and overlying strata contained a broad variety of microfacies types， including bioclastic wackestone-packstone， coral bafflestone， bioclastic packstone， bioclastic grainstone， phylloid algae-cement framestone， fasciculate coral framestone， bioclastic wackestone， and foraminifer-fusulinid grainstone. Conclusions During the Early Permian， glacial-interglacial cycles were the primary factors influencing the variations in palaeoocean temperature and global sea levels. The vertical microfacies succession in this study provides a record of relative sea-level change. The decline of Late Paleozoic glaciation， which resulted in global warming and a relative rise in sea level， played a pivotal role in the development and flourishing of the coral reefs in southern Guizhou province.

Objective The Taiyuan Formation of Permian System in Ordos Basin has the characteristics of large thickness， wide distribution， and rich types of oil and gas resources， which indicates a substantial potential for exploration. At present， the study of this formation is mainly concentrated in the eastern part of the basin， while the exploration and study of Taiyuan Formation in the western part of the basin need to be further discussed due to the complex and variable tectonic pattern and sedimentary evolution. Methods The detrital material source， tectonic setting and paleogeographic evolution of Taiyuan Formation in western Ordos Basin are systematically studied by means of outcrop observation， drilling sample collection， detrital zircon U-Pb dating and paleo-flow analysis. Results The sediments in the northeastern part of the study area （Group A） are mainly from the Yinshan Orogenic Belt under the collision-compressional tectonic background， with strong provenances. The delta plain， delta front， tidal sand ridge and tidal sand bar are successively developed in the middle of the basin. The sediments in the northwest （Group B） are derived from the Alxa Block under the collisional compression and convergent orogenic tectonic background， and the delta plain， delta front and lagoon-tidal flat develop successively towards the middle of the basin. The sediments in the southern （Group D） area came from the North Qilian and North Qinling tectonic belts under the extension-subduction-collision tectonic environment of the Paleo-Tethyan Ocean. The central paleo-uplift of the Taiyuan Period was slow， the provenance-supply was weak， and the mainly developed barrier island-barrierisland-lagoon-tidal flat deposits. Conclusions The northern part of the study area is characterized by high uplift and strong provenance supply in the context of collision and convergence orogenic structures， and large tide-delta complex system， while the southern part is characterized by weak provenance supply in the context of tensile extension structures， and is dominated by tidal flat and lagoon. This study not only deepens the understanding of the sedimentary system and provenance supply mechanism in the western Ordos Basin， but also provides a new perspective and reference for the reconstruction of the tectono-sedimentary evolution process and paleogeographic pattern in the western Ordos Basin.

Objective The Second member of the Middle Permian Lucaogou Formation is the main exploration target for lacustrine carbonate shale oil in the Santanghu Basin， Xinjiang province， China. Clarifying its paleoenvironment and organic matter enrichment mechanism provides scientific evidence in support of shale oil exploration and development in the study area. Methods Tests for total organic carbon content， major and trace elements and carbon-oxygen isotopic composition of primary carbonate rocks were conducted on shale samples collected from the well Luye 1 in the Second member of the Lucaogou Formation in the in the Malang Sag， Santanghu Basin. These deciphered the paleoenvironment and associated organic matter enrichment mechanism of the shale sequence， hence helping to gain a better understanding of the effects of paleoproductivity， paleoclimate， paleosalinity and paleoredox conditions on the organic matter enrichment and the key elements. Results Shale oil sweet spots are present in the middle and upper parts of this shale sequence. The tests indicated a closed lacustrine setting. The lowest part of the middle sweet spot was deposited in an arid， saline and reduced deep-water environment with low paleoproductivity， whereas its upper section has high paleoproductivity and was deposited in a semi-arid， brackish and weakly reducing deep-water environment. The upper sweet spot was deposited in an arid， saline and weakly reduced semi-deep water setting with medium paleoproductivity. Conclusions The organic matter enrichment mechanisms vary between the different shale sections. The influencing elements were the redox conditions and paleoproductivity in the lowest part of the middle sweet spot， paleoclimatic conditions and paleoproductivity for the upper part of the middle sweet spot， and paleoproductivity in the upper sweet spot. This study will assist in shale oil exploration and development in the Second member of the Lucaogou Formation in the Santanghu Basin.

Objective The shale gas of the Cambrian Qiongzhusi Formation in the Sichuan Basin has good prospects for exploration and development， and a knowledge of its sedimentary environment is necessary to evaluate these resources. Methods The focus of this study was the Chengjiaba section shale series in the Qiongzhusi Formation. A detailed field geological survey and whole rock X-ray diffraction and geochemical analyses were carried out. The elements and ratio parameters in the study area were optimized to determine the sedimentary paleoenvironment of the organic-rich shale. Results （1） The First and Second members of the Qiongzhusi Formation are mainly gray-black or black mudstone and silty mudstone， with siliceous rock and siliceous shale facies. The horizontal bedding indicates a deep-water shelf paleoenvironment. （2） The shale TOC（Total Organic Carbon） is relatively high in the Qiongzhusi Formation， ranging from 0.22% to 4.34% （average 2.68%）. （3） The geochemistry of the elements indicates a warm and humid paleoclimate during the deposition of the black shale. The water body was anoxic and highly retained. Conclusions The formation of organic-rich shale in the Qiongzhusi Formation is controlled by multiple factors. Organic matter enrichment in the First member of the Qiongzhusi Formation conforms to the preservation mode， primarily controlled by redox conditions and sedimentation rate. In contrast， the organic matter enrichment in the Second member of the Qiongzhusi Formation follows the comprehensive model， synergistically controlled by paleoclimate， paleoproductivity， sedimentation rate， and redox conditions.

Objective The Wufeng Formation-Longmaxi Formation black rock series in eastern Sichuan and western Hubei is a focus for marine shale gas exploration in South China. These show great differences in sedimentary characteristics， which record major geological events during the Ordovician–Silurian transition. Further knowledge of these differences is of benefit to exploration for shale gas in western Hubei， and helps to understand global paleo-climate and sea-level changes during that time. Methods The sedimentary properties， main influencing factors and sedimentary processes of the black rock series in the Wufeng Formation and Longmaxi Formation were studied in detail by petrological， sedimentological and geochemical analysis. Results The sedimentary attributes of the Wufeng Formation are similar in both study areas， but in the Longmaxi Formation they differ significantly. In eastern Si-chuan， the large thickness of the Longmaxi black shale with completed graptolite zones and thick silty shale in the Rhuddanian-Aeronian transition is overlain by thick， organic-rich shale. Three long-term sedimentary cycles are recognized in the Longmaxi black rock series， but in western Hubei the Longmaxi black shale is very thin and only two long-term sedimentary cycles are identified. Neither silty shale nor Coronograptus cyphus and Demirastrites triangulatus graptolite zones are present in the Rhuddanian-Aeronian transition， but thin lime-bearing dolomitic mudstone covered by thin organic-rich shale are developed. Additionally， the Longmaxi black shale contains less quartz in eastern Sichuan than in western Hubei. Conclusions In this study， tectonic paleogeomorphology and paleoclimate changes are considered to be the main factors influencing the different evolutionary histories of the Wufeng Formation⁃Longmaxi Formation black rock series in the two study areas. During the Upper Ordovician， eastern Sichuan and western Hubei both subsided as a result of the Cathaysia Block⁃Yangtze Block collision. The paleogeomorphology and sedimentary environments in eastern Sichuan and western Hubei are not significantly different， but continuous tectonic compression beginning in the Early Silurian caused non-uniform subsidence. Continuing subsidence in eastern Sichuan and gradual uplift in western Hubei led to significantly different thicknesses of the Rhuddanian black shale in the two regions. Global sea-level fall during the Rhuddanian⁃Aeronian transition related to intensified glaciation further exacerbated the sedimentary differences in the two study areas， resulting in a sedimentary gap in western Hubei and abundant sandy deposits with low TOC in eastern Sichuan. Subsequent significant sea-level rise following global climatic warming promoted the development of black shale in both areas， although thicker in eastern Sichuan than in western Hubei. However， gradually intensifying tectonic compression and gradual sea-level fall， along with sufficient terrigenous sediment supply， sustained a sedimentary environment in both regions that led to the termination of development of the Longmaxi black shale in the two study areas.