Objective In geological logs of shale oil cores from the Chang 7 oil member of the Yanchang Formation in the Longdong region， Ordos Basin， for a long time the resolution of single layer thickness of each rock type has been basically 10 cm， resulting in a large number of rock-type combinations being described as a single rock type. Exploring a new method for the quantitative study of shale oil rock-type combinations and reservoir capacity benefits the efficient exploration and development of shale oil in the Chang 7 oil member. Methods In this study， the shale oil rock types in the Chang 7 oil member were re-identified by high-resolution core observation （single layer thickness resolution 1-5 cm） together with stereo microscope and thin-section identification of 405 samples and analysis of physical property data， then the rock-type combinations and reservoir capacity of Chang 7 oil member were explored quantitatively. Results There are 11 main rock types in the shale oil of Chang 7 oil member of the Yanchang Formation in the Longdong region of the Ordos Basin. Firstly， four combinations of rock-type form （unitype， stratified type， interstratified type and interstratified type） and 65 rock-type combinations were quantitatively identified for the first time. Secondly， a new method is proposed for calculating reservoir capacity on the basis of quantitative evaluation of the reservoir capacity of each of the 11 rock types， combined with the thickness percentage of each rock type， for 65 rock-type combinations. Conclusions This study demonstrates that， to guide the efficient exploration and development of the shale oil in the Chang 7 oil member， the traditional single rock-type study for shale oil should be modified to encompass the study of rock-type combinations. However， this research for the Chang 7 oil member is at the exploratory stage； further improvement will be achieved by examining the effect of combining these findings with a large amount of shale oil exploration and development data.

Objective The reservoirs in the bottom conglomerate of the Qingshuihe Formation in the Gaoquan structural zone of the Sikeshu Sag， southern Junggar Basin， are strongly heterogeneous. The objective was to clarify the development and distribution of high-quality reservoirs in the study area. Methods The sedimentary and reservoir characteristics of the Qingshuihe Formation were examined by facies analysis in cores， well logs and seismic records， and a model of the sedimentary evolution was established based on paleogeomorphological data. The influence of microgeomorphology on the distribution of high-quality reservoirs is clarified. Results Three slope breaks developed in the Gaoquan structural zone， each striking northwest-southeast and comprising groove and platform paleogeomorphological units. A regressive fan delta was formed on the slope breaks during lake transgression， each of which formed conglomerate reservoirs 10-15 m thick. Groove and platform areas controlled the mud content of the reservoirs. Brown conglomerate with high mud content readily developed in the groove areas. Gray or gray-green conglomerate with low mud content developed in the platform areas， forming high-quality reservoirs. Conclusions Groove/platform units at slope breaks controlled the formation and distribution of high-quality reservoirs in the Qingshuihe Formation. The most favorable reservoirs in the study area are in the platform units at each slope break.

Objective The architecture of marine sandy beach-bar reservoirs is complex， and dominant seepage channels and barriers are developed. The current lack of architecture models for underground reservoirs means that there are few effective guidelines for the recovery of residual oil. Methods A system is proposed for recognizing the architecture patterns of marine sandy beach-bar reservoirs from outcrops in the Hudson Donghe sandstone， obtained through the use of satellite photographs and numerical simulations. Results The depositional architecture of individual sand bars within composite beach-bars is affected by many factors （e.g.， shoreline shape， coastal slope， wave direction and height）. Multiple types of sandbar may be formed （e.g.， conical bar， crescent-moon-shaped bar， positive linear bar， nonlinear inclined bar and sandy beach bar）. Based on the identification of boundaries between individual sandbars， and guided by the architecture mode， 13 sandbars of different sizes were identified in the C1 layer in the study area， comprising five crescent-moon-shaped bars， seven forward linear bars and one oblique bar. Differences in scale are evident between different sandbar types： the length of crescent-moon-shaped bars is about 1.5-3.0 km； the length of oblique bars is about 4.5-5.0 km； and the length of positive linear bars is more than 6 km. The sandbars exhibit either progradational or retrogradational stacking patterns； bars in the C1 layer exhibit progradational lateral separation and progradational lateral stacking patterns. The migration rate of the coastline has affected the stacking relationship between the sandbars. Numerical simulations and outcrop observations indicate differences in the developmental patterns of the internal accretion bodies， including top accretion， top- and side accretion， and different interval types. Three internal interlayer patterns were identified in the C1 layer： a two-stage “top- and side-accretion” feature in the No. 16 sandbar， and “side accretion” in the No. 19 sandbar. The slopes of the top and side accretion interlayers range from about 1°-3° to 3°-7°. The layers between No. 14 and 15 sandbars are arranged in an “interval” pattern. Conclusions The fine characterization of the internal architecture of marine sandy beach-bar reservoirs described in this study can effectively guide the recovery of remaining oil.

Objective Deep carbonate reservoirs have an enormous potential for oil and gas exploration. However， due to their complex diagenesis， they are highly heterogeneous and dense. To clarify the modifying effect of hydro-thermal fluid activity on the carbonate reservoirs in a petroliferous basin， this study investigated Upper Carboniferous strata in the southwestern Tarim Basin. Methods The main study area includes some key well locations in the Bachu Uplift and Maigaiti Slope， and typical field outcrop profiles in the Kunlun piedmont thrust belt. Previous research on hydrothermal fluid activity has mainly focused on the northern and Tazhong region of the Tarim Basin， mostly concentrating on the Ordovician System. These studies have accumulated rich experience and obtained many results； however， generally little exploration has been carried out in the southwestern Tarim Basin. To strengthen the basic research， the method of combining geology and geochemistry was adopted in the study area： core observation， thin sections， cathodoluminescence， scanning electron microscopy， isotope data， rare earth element characteristics and previous information were used to identify the indicators of hydrothermal activity in the target formation， defining the alteration mode of carbonate reservoirs in the study area and establishing their logging responses to alteration by the heated fluid. Results A detailed classification of the petrology of the study area found that the presence of typical hydrothermal minerals （e.g.， fluorite， barite， and saddle-shaped dolomite） is an indicator of hydrothermal fluid activity. The geochemical responses of these carbonate rocks to modification by hydrothermal fluids includes high ⁸⁷Sr/⁸⁶Sr values， very low δ¹⁸O， light rare earth element enrichment， loss of heavy rare earth elements， and positive Eu anomalies. Hydrothermal fluids often contain many chemically active substances and release a large amount of heat energy in their interaction with rock and produce physical and chemical reactions with the rock. In particular， such reactions promote strong dissolution of carbonate rocks. Conclusions It has been demonstrated that hydrothermal fluids have both positive and negative effects on the alteration of carbonate rock reservoirs. In the constructive role， the high temperature and rapid flow rate of hydrothermal fluids have strong chemical dissolution and mechanical erosive effects on the rock， expanding migration channels， increasing reservoir porosity， improving pore structure， and generally enhancing reservoir physical properties. Most of these occur at the earliest stage of hydrothermal activity and in the proximity of fault zones. They are identified in the logging response by high acoustic time difference， neutron porosity， low natural gamma and low resistivity values. The dissolution pores and fractures are developed over a large zone， and most are not filled. Conversely， a destructive effect occurs at lower temperature and pressure of the hydrothermal fluid， and is recognized by hydrothermal mineral infill in pores and fractures. As the fluidity decreases， the material carried by the hydrothermal fluid is constantly precipitated， forming new mineral combinations filling pre-existing pores and fractures， which reduces reservoir porosity and damages pore structure. This type of alteration mostly occurs in the late stage of hydrothermal activity far from the fault zone. It is evident in logging response by high resistivity and low natural gamma and acoustic time difference， and low neutron porosity； the pores and fissures are mostly isolated and extensively filled. Overall， however， the target strata were mainly affected by constructive hydrothermal dissolution and its positive impact on reservoir development.

Objective The sedimentary environment of the Pearl River Delta is complex with abundant Perinereis trace fossils. The characteristics， distribution， and assemblage of Perinereis and their relationships with sedimentary environment and sediment properties are significant for the study of trace fossils and the palaeoenvironment. Methods Based on sedimentary and ichnological methods， grain size analysis， salinity， turbidity， total organic carbon （TOC）， X-ray scans， and three-dimensional （3D） reconstruction were applied to the modern biogenic sedimentary structures in different microenvironments of the Pearl River Delta tidal flat， discussed the composition， assemblage， and distribution characteristics of Perinereis in a tidal flat of the Pearl River Delta， and analyzed the relationship between the biological assemblage and the sedimentary environments. Results （1） The Perinereis mainly lives in the tidal flat area of the tidal channel and the interdistributary bay in the Pearl River Delta. （2） The remains of the Perinereis mainly have grazing trails and dwelling trails. However， the grazing trails on the layer are difficult to observe， the dwelling trails in the layer mainly have simple Y-， I-， and U-shaped and complex network structures， and there are bulges at the joints. （3） The Perinereis is suitable for living in the tidal flat or channel of the interdistributary bay with low hydrodynamic conditions， low salinity， low turbidity， and rich total organic carbon content. Conclusions The spatial distribution of Perinereis neoichnology is imbalanced， and multiple environmental conditions jointly control the abundance of Perinereis neoichnology. The habitat of Perinereis is similar to the trace fossil Polykladichnus， which can belong to both the Mermia and Glossifunites ichnofacies； the trace fossil assemblage of this relic mainly appears in the channel and tidal flat area， and this study supplements the biological data for the modern neoichnology of Perinereis.

Objective At present， the iron dolomite genesis mechanism of the Maosan-Wuyi in north-central Sichuan is not clear. Methods Based on the rock-mineral characteristics of the Maosan-Wuyi， we combined rock TIMA scanning， whole-rock X-ray diffraction analysis， microzonation in situ main trace elements， strontium isotopes fluid inclusions homogeneous temperature， and in situ U-Pb chronology of iron dolomite to study the mechanism of iron dolomite genesis. Results The study shows that： （1） the rock types of the Maosan and Wuyi are cherts， dolomites and tuffs. The tuffs mainly include mud crystal clastic， bright crystal clastic， and cloudy tuff； the dolomites are semi-autogenous-to-autogenous powdery-to-fine crystalline dolomite； the sedimentary tuffs are mainly composed of volcanic clasts， carbonaceous， calcium-magnesium， sand-grade clasts， and metallic minerals， among which the volcanic clasts are glassy clasts， basalt， and other clasts， and the calcium-magnesium mainly consists of dolomite and calcite. （2） The average values of trace elements in the dolomite at the top of Maosan and Wuyi show extremely high Fe content （10 678.40×10^-6）， high Mn content （822.95×10^-6）， Si content （1 929.81×10^-6）， Al content （394.11×10^-6）， and high Na+K content （362.38×10^-6）， indicating that the fluids in the closed environment are characterized by high salinity and alkaline metal content. This also indicates that the rock-forming fluids in the confined environment are characterized by high salinity and high alkaline metal content. The ⁸⁷Sr/⁸⁶Sr in the matrix of ankerite and mud crystal clastic tuffs are within the range of seawater from the same period in the Maokou and Wujiaping groups， and they also have low total rare earth element （REE） values and light REE （LREE） loss， consistent with the LREE loss pattern of seawater， indicating that the dolomitized diagenetic fluids and seawater of the same period have similar characteristics. （3） The U-Pb age of powdery-to-fine crystalline dolomite in the Maosan and Wuyi is 245.36±1.08 Ma， and the dolomitization mainly occurred in the Late Permian to Early Triassic. Conclusions The source of dolomitization fluids in the powdery-to-fine crystalline dolomite of the Maosan and Wuyi is the dewatering of clay minerals in the argillaceous tuffite and tuffaceous mudstone of the overlying Wuyi and Wuer. During this process， a large number of Mg²⁺， Fe²⁺， Al³⁺， and Si⁴⁺-rich ions were precipitated and transported to the granular tuffs at the top of Maosan and Wuyi to form iron dolomite using the seawater residual from the Maokou Formation to Wujiaping Formation during the same period as the carrier.

Objective By studying the geometric characteristics and formation mechanism of pyrite and tuff dikes in shales of the Qingshankou Formation in Gulong Sag， this paper discusses their formation time， sedimentary environment， sedimentary process， sediment state and diagenetic environment， and estimates the diagenetic compaction rate of shale， which provides reference for the formation mechanism and significance of the same type of dikes. Methods Based on detailed core observation， thin section analysis and dynamic calculation of dike formation， pyrite and tuff dikes are found in the Gulong shale， and their genetic mechanism and geological significance are explored. Results The pyrite and tuff dikes in shales of the Qingshankou Formation in Gulong Sag are small in scale， and pyrite dikes can be divided into two types according to their scale. One is the thick pyrite dikes with a width of 1-4 mm and a length of several centimeters； The other is a thin pyrite dike， which is less than 1 mm wide and several millimeters to several centimeters long. Tuff dikes are mostly less than 1 mm in width and several millimeters to several centimeters in length， and most of them are strongly bent into ptygmatite， erect， inclined or horizontally produced. It is speculated that gravity subsidence may be caused by density inversion， and the dynamic formation model of pyrite and tuff dike is established by calculation. Conclusions The shape of pyrite dike in shale oil reservoir of the Qingshankou Formation in Gulong Sag is very complex， which is formed by gravity subsidence sand dike after late pyritization， that is， there are silt dikes first and then pyrite dikes formation. The tuff formed by volcanic eruption settling on unconsolidated mud of lake， and then tuff dike formed due to gravity subsidence caused by density inversion， rather than overpressure filling from bottom to top caused by seismic liquefaction. The oblique pyrite dike and tuff dike are symmetrical at a distance of 180 degrees， which are subjected to bedding shear action. There are many silt-grade mud debris and large flame-like mud debris in the interior dikes， which are formed by the sand dike and tuff dike sinking into the unconsolidated or even muddy mud at the lower part and being captured.

Objective The Chang 7 member of the Triassic Yanchang Formation in the Ordos Basin mainly developed semi-deep lake-deep lake subfacies； deep-water gravity flow deposits are widely developed. This study aimed to clarify its sedimentary characteristics and distribution rules which can indicate the direction of oil and gas exploration. Methods Taking the Chang 7 member in the Fuxian area of the southeastern basin as the research object， based on the fine description， grain size analysis and logging data of centimeter-level cores from 13 coring wells， the types and characteristics， distribution law and evolution model of gravity flow deposits in the Chang 7 member were clarified. Combined with oil and production test data， the control effect of gravity flows on reservoir distribution was analyzed. Results The results show that the Chang 7 member in the Fuxian area mainly developed three types of gravity flow sedimentary microfacies： sliding-slump， sandy debris flow， and turbidity current deposition. The sliding-slump deposits are characterized by the development of enclave bedding， crumpled deformation structures， and syn-depositional stepped small faults and sliding surfaces and are dominated by mixed deposits of sandstone and mudstone. Sandy debris flow deposits have developed thick massive sandstone， mudstone tearing debris， and mud-encapsulated gravel structure. The thickness of single sand body is 0.3-3.5 m， and the cumulative thickness can reach more than 10 m. Turbidity current deposits have developed flame-like structures， groove molds， other bottom mold structures， and incomplete Bouma sequences. Sand bodies are small in scale and limited in development. The thickness of single sand bodies is several centimeters to tens of centimeters. The Chang 7 member is divided into six typical logging facies combinations and 11 lithofacies types. The grain size probability accumulation curve is characterized by “one-stage suspension” and a “wide arch”. Most of the data in the C-M diagram are parallel to the C=M baseline. Conclusions Among the three kinds of gravity flow sedimentary microfacies in the Chang 7 member， the sandy debris flow has the largest scale of development， accounting for approximately 80%， and the drilling frequency is 60%， making it the most favorable reservoir. Sliding-slump and turbidity current deposits account for approximately 10%. The formation mechanism of the gravity flow in the Chang 7 member is a variety of effects of underwater slope break zones， volcanos， and earthquakes. The development scale of deep-water gravity flow deposits is large， and it forms a good “source-reservoir-cap” combination configuration with source rocks vertically， creating conditions for the near-source accumulation of tight oil. On the plane， the Chang 7₃ sub-member mainly developed turbidity current deposits， and the Chang 7₂ and Chang 7₁ sub-members mainly developed sandy debris flow and turbidity current deposits. The sandy debris flow sand body has a high oil level， mainly oil immersion and oil spots. In the sandy debris flow development area， the industrial oil flow wells account for 21% of the total number of test wells， making it the key target area for the next exploration.

Significance Cold seep activity has a significant impact on marine ecosystems and global climate change， and has been widely developed globally at active and passive continental margins. The fundamental process operating at seeps is the anaerobic oxidation of methane （AOM） mediated by a combination of anaerobic methanotrophic archaea （ANME） and sulfate-reducing bacteria （SRB）. This increases the alkalinity of pore water， forming a favorable environment for carbonate mineral precipitation. Cold seep carbonates are the product of submarine cold seep activity， and their geological and geochemical characteristics are often used to trace seepage fluid information and changes in sedimentary environments. Progress Taiwan area of China is located in the collision zone between the Luzon Island Arc of the Philippine Sea Plate and the Eurasian continental margin， and possesses complex geological structures such as extensive faults， providing appropriate conditions for the development of cold seeps. Cold seep carbonates in the Taiwan area are mainly found in Miocene to Pleistocene strata， which are ideal for the study of ancient cold seeps. A relatively detailed study has been conducted on their fundamental geological and geochemical properties， including mineralogy， petrology and carbon and oxygen isotope content. This study includes a comprehensive analysis of the geological occurrence， mineralogical and petrological characteristics， carbon and oxygen isotopes content， rare earth element （REE） geochemistry， and macrofossil content of cold seep carbonates in the Taiwan area. In addition， it explores the fluid seepage activities and the depositional environment recorded by the cold seep carbonates， taking account of the geological and geochemical features of cold seep carbonates from other regions globally. Conclusions and Prospects The predominantly blocky and chimney-like forms of the cold seep carbonates in the Taiwan area indicate two types of seepage activity： the blocky forms indicate prolonged periods of low-flux diffuse seepage； the chimney-like forms represent shorter periods of high-flux convective seepage. The primary carbonate minerals are dolomite and calcite， with a significant presence of framboidal pyrites. The size of the pyrite grains may be related to the redox conditions during deposition. The carbon isotope composition of cold seep carbonates indicates that the primary sources of carbon were biogenic and thermogenic methane， with additional influence of seawater or residual CO₂ from methanogenesis. Notably， Pliocene cold seep carbonates exhibit the widest range in carbon isotope values， suggesting a greater diversity of carbon sources， potentially due to the complex geological structures in Taiwan area at that time. Furthermore， the δ¹⁸O values of cold seep carbonates from the Miocene to the Pleistocene in the Taiwan area exhibit an increasingly positive trend， suggesting that these carbonates might have undergone a transition from gas hydrate formation to dissociation and release. The geochemical characteristics of the REE indicate a predominantly reducing depositional environment. The cold seep macrofossils are dominated by bivalves， representing few biological species in the Miocene and Pliocene but a greater range in the Pleistocene， possibly as a result of different water depths. For greater in-depth understanding of the ancient cold seep systems in the Taiwan area， future research on cold seep carbonates could focus on in situ micro-scale analysis of carbon and oxygen isotopes， and molybdenum element and isotope， in the carbonate minerals， as well as the spatial differences in the growth of macrofauna of different genera of the Lucinidae family， in conjunction with geochemical analysis.

Objective The study of the relationship between climate proxies and climate factors in sandy surface sediments is highly significant when determining the reliability and applicability of climate proxies. Methods In this study， 32 samples of surface sediments were collected over a large spatial scale in Otindag sandy land. By analyzing correlations between chroma， Hm/Gt， magnetic susceptibility and modern climate factors （average annual precipitation and average annual temperature）， the relationships between each index and climate factors and their environmental significance are discussed. Results The results show that the variation range of a^* and b^* is small， and that the overall trend from east to west is increasing： the minimum value of a^* is 3.87， the maximum value is 8.26， and the average value is 6.09. The minimum value of b^* is 9.49， the maximum is 17.44， and the average is 14.24. a^* and b^* were negatively correlated with precipitation （correlation coefficients -0.88 and -0.77， P < 0.01）， and positively correlated with temperature （correlation coefficients 0.89 and 0.82， P < 0.01）， indicating that both a^* and b^* could be used as effective proxy indicators of climate change， with a^* being the more sensitive to climate factors. The variation range of L^* was small， and no obvious change rule from east to west was evident. The maximum value was 59.54， minimum value 48.80， and the average value was 54.69. The relationship between L^* and climate factors is not obvious， and its change is mainly directly affected by vegetation； it does not appear to have any obvious indicative significance for climate. The peak value of the first derivative of hematite ranges from 0.08 to 0.19， with an average of 0.14. The peak value of the first derivative of goethite ranges from 0.06 to 0.09， with an average of 0.07. The value of hematite/goethite （Hm/Gt） ranged from 1.20 to 2.73 （average 1.88）， and showed an increasing trend from east to west. The correlation between hematite and climate factors is higher than it is for goethite. The ratio of Hm/Gt is negatively correlated with average annual precipitation （correlation coefficient -0.85， P < 0.01）， and positively correlated with average annual temperature （correlation coefficient 0.84， P < 0.01）， which reveals the sensitivity of both hematite and Hm/Gt to precipitation and temperature. It effectively reflects changes of hydrothermal conditions in sandy land. In low-frequency magnetic susceptibility （χ_lf） and high-frequency magnetic susceptibility （χ_hf）， the variation direction of hf amplitude shows a constantly increasing trend from east to west. The percentage frequency magnetic susceptibility does not change significantly from east to west. The magnetic susceptibility of the region does not correlate well with climate factors. The source of the sand material may be the main factor in its variation， emphasizing the complexity and specificity of sand magnetic susceptibility changes. Conclusions a^*， b^*， and b^*/a^* are all effective alternative indicators for studying regional climate， whereas L^* is influenced by vegetation， resulting in ambiguous climate information. Hematite and Hm/Gt values correlate well with climate parameters and are ideal indicators of moisture and heat changes in sandy land. The surface magnetic susceptibility of sandy land is less affected by climate， reflecting the complexity and specificity of magnetic susceptibility changes in sandy land.