In recent years, Mesozoic magmatic rock has been found in many offshore petroleum-bearing basins in China, and it is widely distributed, such as the Bohai Bay basin, the East China Sea basin, the Pearl River Mouth basin, and the Qiongdongnan basin. Petrological, geochemical and reservoir research of Mesozoic magmatic rock in these basins are not only of theoretical significance for the formation and evolution of the basement of basins, but also of practical value for oil and gas exploration in magmatic buried hills. This paper systematically compares the characteristics of Mesozoic magmatic rock and the types of oil and gas reservoirs in the typical basins of the Bohai Bay basin, the Pearl River Mouth basin, and the East China Sea basin using petrological, geochemical, and petroleum geological data. Research has shown that the Mesozoic magmatic rock in China’s offshore petroleum-bearing basins consists of two major categories of volcanic and intrusive rocks with more than 20 types of lithologies. There are different volcanic rocks from basic to acid in the Bohai Bay basin, and a lack of basic volcanic rocks in other basins. They developed mainly in three stages: Late Jurassic, Early Cretaceous, and Late Cretaceous. Controlled by the subduction of the Paleo-Pacific plate and subsequent back-arc rifting, the offshore basins underwent differential tectonic evolutions under a transition environment from a compression in the Jurassic to an extension in the Cretaceous. The East China Sea basin and the Bohai Bay basin underwent back-arc rifting, and the Pearl River Mouth basin was an offshore magmatic arc. There are three types of reservoirs, namely, granitic weathered crusts, igneous complex, and intermediate-acidic volcanic rocks. Favorable lithological facies, intense tectonic and weathering modification, and strong dissolution are the keys to the reservoir formation of magmatic rocks for buried hills.

 The exploration potential of Mesozoic volcanic rocks in Liaodong Bay depression of Bohai Bay basin is great, but the development law of high-quality volcanic rocks reservoir is not well understood. Aiming at the difficulty of exploring the genesis of favorable reservoirs of Mesozoic volcanic rocks, the reservoir space types, physical properties, pore microstructure, and other characteristics of Mesozoic volcanic rocks in  Jinzhou 25-A structure area in Bohai Sea are studied by a comprehensive application of drilling data, thin section, and physical property data, and the conditions and reservoir development model of high-quality volcanic rocks are analyzed and discussed. The results show that the Mesozoic volcanic rocks in Jinzhou 25-A structure area are mainly composed of trachyandesite and andesite in the lower subfacies of the intermediate-acid overflow facies, and a small amount of basalt in the basic overflow facies. Favorable reservoirs are mainly developed in trachyandesite and trachyte of the intermediate-acid overflow facies. The reservoir space is dominated by secondary origin, which mainly develops matrix pores, intracrystalline pores and fractures. Some intergranular pores can also be seen in the breccia on top of volcanic rocks. The average porosity and permeability of the reservoir are 20.3% and 0.209 mD respectively. It belongs to the high porosity and low permeability reservoir. Thick weathering crust is often developed on the top of volcanic rock mass after a long time weathering and denudation. At the same time, the inner reservoir of secondary weathering crust between eruptive units is also developed in the mother rock zone. The effective fracture direction is mainly NEE-SWW and NS direction, which creates good conditions for the formation of favorable reservoirs. Therefore, this paper established a volcanic rock regular model reservoir development model of “weathering as the main control, thick weathering crust reservoir developed on the top of volcanic rock, and secondary thin weathering crust inside reservoir developed on the top of eruption unit”.

 Mesozoic volcanic rocks are widely distributed in the Bozhong depression of Bohai Bay basin. At present, volcanic oil and gas reservoirs have been found in several formations, which have great exploration potential. However, the complexity of the volcanic lithology and lithofacies in the northern part of the Bozhong depression and the non-homogeneity of the reservoirs due to multiple tectonic movements and fluid modification make the study of the mechanism of reservoir formation relatively weak at present. In order to clarify the main controlling factors of Mesozoic volcanic reservoir formation, this study analyses the petrological characteristics of volcanic rocks by core observation, thin section description, physical properties and major element data, classifies the volcanic facies based on the seismic data, and systematically summarizes the formation mechanism of the effective volcanic reservoirs and hydrocarbon accumulation features. The study shows that: There are 7 types of volcanic rocks and 6 kinds of lithofacies, the dominating reservoir space is pore + fracture network type. The intermediate-acid volcanic rock is the basic condition for the formation of high-quality reservoir, and the effusive intermediate-acid lava is the favorable lithology and lithofacies for the formation of high-quality volcanic reservoirs. The tectonic fracture and the dissolution of meteoric fresh water and organic acids in the later period ensure the effectiveness of high-quality reservoirs and greatly improve the porosity and permeability of volcanic reservoirs. The main hydrocarbon source rocks in the study area are directly connected to the volcanic buried hills, or can be effectively transported through faults and unconformities, and can be aggregated into reservoirs by developing multiple anticline trap in the main period of reservoir formation, while the Third Member of the Shahejie Formation and Dongying Formation, with thick layers of super-pressured mudstones, act as an effective cover and are steadily laterally distributed on the whole area. 

 Lower Paleozoic carbonate buried hill is an important oil and gas exploration field in Bohai Bay basin. The existing buried hill is mainly concentrated in the high structural position. The reservoir development and hydrocarbon accumulation scale in the low structural position of low slope carbonate buried hill are less understood. In order to understand the developing principles of slope carbonate buried hill and the forming conditions of hydrocarbon accumulations, the tectonic evolution of buried hill, the genetic mechanism of reservoir spaces, the comprehensive analysis of hydrocarbon accumulation were carried out in northwest Shaleitian. It is concluded that: 1) The lithology of the lower Paleozoic buried hill in the slope belt of northwest Shaleitian is composed of the upper association (large set of limestone and muddy limestone) and the lower association (oolitic limestone, interbedded limestone and mudstone), the stable mudstone in the Gushan Formation is the boundary between these two units. 2) The buried hill in the slope zone have undergone five periods of tectonic movements, namely the Indosinian, the Early Yanshanian, the Middle Yanshanian, the Late Yanshanian, and the Xishanian, and had the characteristics of seesaw-type structural evolution. A large number of fractures formed by multi-stage tectonic activities is favorable for the foundation of reservoirs. The component coupling of dominant lithology, superposition stress fracture formation and multi-stage karst transformation controlled the development of carbonate buried hill reservoirs, forming stratiform fracture-soluble high-quality reservoirs, of which the upper association is the dominant oil-gas accumulation layer. 3) The low-slope carbonate buried hill is located in the transitional zone, with the oil-gas accumulation model of upper supergene karst reservoir-lower dense layer shielding and sealing formation, forming large and medium-sized oilfield groups in the slope area.

 The volcanic rocks of Yixian Formation in Bozhong sag of Bohai Bay basin are widely distributed, but the stratigraphic structure is complex and the lateral variation is fast. The division of volcanic eruption cycles is of great significance for studying the spatial distribution characteristics of volcanic rocks and guiding oil and gas development. Based on the geological data such as core, wall-core thin section, zircon U-Pb dating and logging and seismic data of volcanic rock strata in 38 wells, the volcanic eruption cycle, volcanic rock distribution and its relationship with faults, as well as the oil and gas geological significance of volcanic eruption cycle of Yixian Formation in Bozhong sag of Bohai Bay basin were studied by using volcanic stratigraphy method and seismic volcanic stratigraphy theory. The results show that:1) The volcanic rocks of Yixian Formation in Bozhong sag of Bohai Bay basin can be divided into three cycles. The first cycle is a basic cycle, which mainly develops basalt and basaltic tuff. The average drilling thickness is 189 m, and the eruption time of volcanic rocks is 128-122 Ma. The second cycle is a intermediate cycle, which mainly develops andesite and trachyandesite. The average drilling thickness is 232 m, and the eruption time of volcanic rock is 122-115 Ma. The third cycle is an acidic cycle, mainly developed rhyolite and crypto-explosive breccia rocks. The average drilling thickness is 241 m, and the volcanic eruption time is 115-114 Ma. 2) Volcanic rocks of Cycle 1 are the most widely distributed in the Bozhong sag, and only the Bonan low uplift, Shijiutuo uplift, and the northern part of the Bodong low uplift lack the strata. Their distribution is mainly controlled by the Yanshanian strike-slip faults and is dominated by fissure eruption. Volcanic rocks of Cycle 2 are widely distributed in Bozhong sag, only Bonan low uplift, Shijiutuo uplift and Bodong sag are lack of this stratum. Its distribution is mainly controlled by strike-slip faults in Yanshanian and pre-existing faults in Indosinian  in NWW direction, which is dominated by central eruption. The distribution area of the Cycle 3 acid volcanic rocks in the Bozhong sag is significantly reduced, and the formation is missing in a large area in the northern part of the Bozhong sag. Its distribution is mainly controlled by the strike-slip faults in the Yanshanian  and some pre-existing faults in the NWW Indosinian. 3) The volcanic rocks of Cycle 2 and Cycle 3 in this area have good reservoir physical properties, and the oil and gas display effect is good, which can be used as a favorable horizon for the exploration of volcanic oil and gas reservoirs in Yixian Formation of Bozhong sag in Bohai basin.

The reservoir fractures of  volcanic rock of Kenli 16 structure on the southern slope of Laizhou Bay depression   in Bohai Bay Basin are developed, which has a significant effect on reservoir quality. However, its formation period and distribution law are not clear, which restricts the in-depth understanding of the reservoir. Based on core, imaging logging and outcrop data, this paper studies the fracture types, formation stages and distribution of Mesozoic volcanic rocks in Kenli 16 structure. The main  results are as follows:  Six kinds of cracks are identified, including explosion cracks, crypto-explosion cracks, condensation shrinkage cracks, weathering cracks, structural cracks, and corrosion cracks. The fractures are mainly of middle  to high  angle. The condensation contraction fractures are mainly of medium scale, and the structural fractures are mainly of large scale.  The fracture opening  degree descends from pyroclastic rock, pyroclastic lava,  and sedimentary pyroclastic rock  to lava. The fracture formation period can be divided into five  stages, and a large number of structural fractures are formed under the strike-slip stress system. The fracture surface densities of each lithology  descend from lava,  pyroclastic lava, and pyroclastic rock  to sedimentary pyroclastic rock.The fracture surface densities of each facies  descend from lava flow subfacies, hot clastic flow subfacies, and hot foundation wave subfacies,  to collapse retransported accumulation subfacies. In the outcrop area, the fracture zone width of lava can reach 2 m, the cracks are mostly open, and the fault of the pyroclastic rock develops scratches, forming a decimeter-dense zone, which reduces the permeability of the rock. 

 The focus of exploration gradually shifted from shallow to deep Paleogene strata in Zhu Ⅰ depression, the Pearl River Mouth basin. Volcanic materials are widely developed in Paleogene strata, which is one of the important factors affecting the physical properties of deep clastic rock reservoirs. This study comprehensively utilizes methods such as thin section, element surface scanning, morphological characteristics and U-Pb dating of detrital zircons, combined with the volcanic background of the study area, to study the volcanic materials properties of the Paleogene detrital reservoirs in the Zhu Ⅰ depression. The results showed that the Paleogene in the study area mainly developed acidic, intermediate, and basic volcanic materials. Acidic volcanic materials often have a high mass fraction of Si, rich in Al and K. The alteration products are mainly clay minerals such as kaolinite and illite, and their formation is related to acidic magma eruptions. They are often associated with acidic volcanic rock fragments such as rhyolite and can be identified as synsedimentary volcanic zircons, mainly distributed in the Lufeng sag. The intermediate volcanic materials have a moderate Si mass fraction and are relatively rich in potassium. The main alteration product is authigenic quartz, often associated with intermediate volcanic rock fragments such as andesite. It is distributed in Enping sag, eastern Yangjiang sag, and Lufeng sag. The basic volcanic materials have extremely low Si mass fraction and is rich in Fe and Mg. The alteration products are mainly mafic clay minerals and zeolite, mainly distributed in the Huizhou sag, with a small amount distributed in the Xijiang sag. In addition, a small amount of alkaline volcanic materials is locally developed in the Lufeng sag 13 structural belt of the study area, which is mainly distinguished by the alteration product being apatite. Low porosity and low permeability are commonly observed in tuffaceous reservoirs, but under specific diagenetic conditions, the locally developed small amount of volcanic materials and the dissolution properties of volcanic materials can play a role in increasing and preserving pores, which has a certain improvement significance for later petroleum charging.

 To analyze the geochemical characteristics of crude oil in the Kaiping sag of the Pearl River Mouth basin and to ascertain the hydrocarbon sources for more scientific and rational exploration and development strategies, this study conducted an analysis of geochemical features, crude oil genesis, and sourcing based on geochemical experimental analysis and testing data of crude oil and source rocks from the middle-deep layers in the southern region of the Kaiping sag. The results indicate that the crude oil in the southern Kaiping sag is characterized by high wax content and light-to-medium density. The crude oil from the K18-1 and K11-4 hydrocarbon-bearing structures in the southern Kaiping sag exhibits similar geochemical features, including a dominance of C21TT or C23TT, low oleanane content, a preference for C27 and C29 regular steranes, and the presence of 4-methyl C30 sterane, suggesting a contribution from both algal aquatic organisms and terrestrial higher plants. However, there are still certain differences in organic matter input and depositional environments between the hydrocarbon-generating precursors of the crude oil from the two hydrocarbon-bearing structures. The crude oil from the K18-1 hydrocarbon-bearing structure is relatively unique, differing from that of K11-4 and other regions. It has low oleanane content and a high C21TT/C19+20TT index, indicating it is a typical lacustrine crude oil. In contrast, the crude oil from the K11-4 hydrocarbon-bearing structure is similar to that from other regions in the Kaiping sag, with relatively high oleanane content and a lower C21TT/C19+20TT index, suggesting it is more fluvial-deltaic in nature. An evaluation of source rocks and an analysis of molecular geochemical characteristics indicate that there are significant differences in the geochemical features of source rocks from different intervals in the southern Kaiping sag. The lower member of the Wenchang Formation consists of Type Ⅰ-Ⅱ2 organic matter lacustrine source rocks, while the upper member of the Wenchang Formation to the Enping Formation comprises Type Ⅱ1-Ⅲ deltaic coal-measure source rocks. The former exhibits superior organic matter abundance and hydrocarbon generation potential compared to the latter. Based on an analysis of the depositional environments, organic matter sources, and maturity levels of crude oil and source rocks, combined with a comparison of oil-source biomarker compound parameters and an analysis of the hydrocarbon generation potential of source rocks, it is believed that the crude oil in the southern Kaiping sag primarily originates from the lower member of the Wenchang Formation underlying the respective hydrocarbon-bearing structures. The southern Kaiping sag possesses relatively high-quality hydrocarbon source conditions and exhibits favorable exploration prospects.

 Baiyun sag is one of the main oil and gas producing areas in the northern continental margin of the South China Sea. It has been widely discussed by scholars wroldwide because of its broad oil and gas prospects. However, the tectonic background, source rock composition, ancient water system, and ancient landform characteristics of the Eocene sedimentary source area need to be further studied. The evolution of the source system during the depression-fault-depression transition period is still not clear. In this paper, the characteristics of paleogeomorphology evolution and provenance distribution of Eocene in Baiyun sag  are systematically revealed based on rock mineralogy, rare earth element, and three-dimensional seismic data.  The results show that the tectonic background of the source area in Wenchang and Enping periods has the attribute of recycled orogenic belt, and the deposition of Enping Formation is restricted by the mixed orogenic belt and the stable continental block source area, which shows the characteristics of mixed source in the fault-depression transition period. In addition, the proportion of deep rock minerals such as rutile/garnet is higher in the Enping Formation, which may indicate strong tectonic metamorphism in the source area. The characteristics of rare earth elements show that the distribution patterns of Eocene source rocks and granites in Baiyun sag are similar. The ancient water system transits clockwise from convergence to divergence in the depression-fault-depression transition period. The source supply generally shows the characteristics of axial supply in the basin-the supply of the northern gentle slope-the long axis supply outside the basin. The characteristics of the lake basin also show the characteristics of small basin shallow lake-large basin deep lake-wide gentle lake basin-shallow water wide basin.

 The southern subsag of the Baiyun sag-Liwan sag is a passive margins basin, located in the Pearl River Mouth basin, northern South China Sea. Its geological background is complex and it has experienced many periods of stretching and subsidence. The tectonic evolution from the Eocene to the Miocene includes rifting and downwarping, forming a multi-level sedimentary structure. In this study, tectonic-thermal modelling is used to recover the tectonic subsidence history and basement heat flow history, so as to explore the geodynamic background of the basin evolution. This study selected 19 seismic lines (7 east-west, 12 north-south), established 380 simulation Wells, carried out tectono-thermal modelling, and recovered the tectonic subsidence history and tectono-thermal evolution history of southern subsag of the Baiyun sag-Liwan sag. It is found that there are two periods of rapid subsidence in southern subsag of the Baiyun sag-Liwan sag since Eocene, which occurred in Eocene (47.8-33.9 Ma) and Miocene (23.0-13.8 Ma), and their tectonic subsidence has significant differences between east-west and north-south. Meanwhile, the basement heat flow experienced two significant increases, the first time in the Eocene, the basement heat flow rapidly increased to about 86 mW/m2. The second time in the Miocene, the basement heat flow reached the highest value at 13.8 Ma, and reached 125 mW/m2 in the southern Liwan sag. The results show that the subsidence and heat flow characteristics of southern subsag of the Baiyun sag-Liwan sag are closely related to its tectonic evolution.

 Baiyun sag is located in southern Pearl River Mouth basin, which is an inherited deep sag. The current exploration results show that it is a gas-rich sag. However, it is controlled by the paleogeomorphology pattern, fault combination, source supply, and paleo-valley-slope break system of the Paleogene Wenchang Formation and Enping Formation in Baiyun sag. There are many different types of source-sink systems in the study area. In this paper, through detailed rock mineralogical analysis and three-dimensional seismic data, the coupling and time-space evolution of the Paleogene source-sink system in Baiyun sag are revealed. In the early stage of rifting (Lower Wenchang Formation), the source was dominated by Mesozoic intermediate-acid igneous rocks in the basement of the basin. The basin as a whole showed a pattern of depression and uplift. The sedimentary center and deep sag were controlled by two groups of axial faults trough sources with different distribution directions in NWW and NE directions, and formed felsic-rich sand bodies. The distribution range of sand bodies in this period is very limited, mainly showing the characteristics of short range and low structural maturity. The axial provenance of the Upper Wenchang Formation gradually shrank, and the scale of the northern provenance channel restricted by the gully system gradually increased. Compared with the Lower Wenchang Formation, the clastic rocks of the Upper Wenchang Formation had higher structural maturity and compositional maturity, showing a large-scale transportation process. The lithofacies paleogeography and provenance system pattern of the Eenping period are obviously different from those of the Wenchang period. It is characterized by the typical sedimentary characteristics of shallow water and wide basin, and large-scale shore-shallow lacustrine facies and braided river delta are developed on the side of the northwest channel. The scale of the source area in the basin is significantly reduced, and the long axis source system outside the basin restricts the distribution of large-scale sand bodies.

  Baiyun sag in the Pearl River Mouth basin is an important target for deepwater exploration, which has a highly variable geothermal gradient. The geothermal gradient of a single well is as high as 66.4 ℃/km. The high geothermal field has an important control effect on the diagenesis of the reservoir, affecting the evolution of pores and the changing trend of the relationship between porosity and permeability. However, the influence mechanism of geothermal gradient on reservoir quality under the background of high geothermal gradient is still unclear, which seriously restricts the further exploration deployment.By analyzing  rock samples from  Eocene to the Early Miocene in the study area, the relationship among genthermal field, formation temperature, petrological composition and reservoir evolution in deepwater area is comprehensively analyzed by means of comparative study.   The permeability of  Zhujiang Formation and Zhuhai Formation decreases rapidly with the increase of  formation temperature and burial depth. When the formation  temperature exceeds 140 ℃, the permeability is usually less than 1 mD. The sandstone pores are mainly secondary pores with carbonate cement and authigenic clay minerals inside. However,  Enping Formation exhibits different characteristics, maintaining a high permeability up to 200 mD, even with a rapid decrease in porosity. The sandstone of  Enping Formation is a set of coarse-grained sandstone, mainly composed of quartz, with preserved primary pores, good pore structure, less intergranular filling with cement, and good porosity-permeability relationship. It could be concluded that the decreasing rate of porosity and permeability in the reservoir was controlled by the geothermal field as well as the primary composition of sandstone.

 In order to clarify the evolution model and controlling factors of distribution of volcanic rocks in the southwestern Enping sag, Pearl River Mouth basin, based on the datasets of the target area and adjacent area, the lithological and lithofacies characteristics are identified with thin section and logging firstly, then the volcanic edifice characteristics are identified with well and seismic datasets, finally, the genesis of volcanic rocks are identified with geochemical data. The results show that basalt-dominated volcanic rocks developed in southwestern Enping sag. Through drilling data, four types of volcanic rock are identified, namely hyaloclastite, massive basalt, amygdaloid basalt, and hydrothermal breccia. The Cenozoic volcanic rocks in the study area are divided into two kinds of lithofacies and four kinds of subfacies：Volcanic conduit facies （including hidden breccia subfacies）, effusive facies （including hyaloclastic rock subfacies, tabular lava flow subfacies, and braid lava flow subfacies）. At the same time, four eruption periods are identified based on sedimentary rock interfaces, and volcanic crater-near volcanic crater, proximal volcanic facies belts, middle-distance and distal volcanic facies belts are divided according to each period. Volcanic reservoirs are complex, and the physical properties of volcanic conduits-near volcanic crater and proximal volcanic facies belts are relatively good. The basaltic magma of different stages in the research area was formed by the separation and crystallization of homologous mantle derived magma. The magma chamber is located in the lower crust and has undergone strong crustal assimilation and mixing. According to the seismic data, it is identified that the fault in the study area is characterized by two phases of activity. The Pearl River Formation is NEE-NE trending in the sedimentary period, and the Hanjiang Formation is NWW-NW trending in the sedimentary period up to now. The origin of the magma is associated with deep-seated faults. The NW sinistral strike-slip component induces a weak leftward rotation in the volcanic facies, gradually transforming its shape from a straight line into an inverse S-curve.

The Baiyun sag in the deepwater area of the Pearl River Mouth basin is characterized by complex tectonic features and low exploration levels. There is still a need for in-depth research on the fault structures within the sag, and the activity of faults during the rifting stage and the dynamic evolution of the regional stress field remains unclear. To reveal the fault activity characteristics and dynamic mechanisms during the rifting stage in the Baiyun sag of the northern margin of the South China Sea, this paper takes the Baiyun sag in the Zhu Ⅱ depression as an example. Based on the latest 3D seismic data and stratigraphic interpretation schemes, methods such as coherence attributes and ancient fault throw analysis are used to analyze the tectonic characteristics of the Baiyun sag. The main active faults in the Baiyun sag are classified into three levels: First-order basin-controlling faults, second-order sag-controlling faults, and third-order zone-controlling faults. Based on high-resolution 3D seismic data, five fault types were identified in the study area: Flower-like faults, imbricate faults, step faults, Y-shaped faults, and nested V-shaped faults. Four fault combination patterns were identified: Parallel faults, en-echelon faults, oblique faults, and broom-like faults. By quantitatively analyzing the characteristics of 507 faults across different periods, the dynamic evolution of the regional stress field and its associated dynamic mechanisms were further explored. The study shows that from the Late Eocene to the Early Oligocene, the fault orientations underwent a clockwise rotation from NE-NEE to EW. Based on the analysis of ancient fault throw, the activity intensity of the first-order faults gradually weakened, and significant differences were observed in the activity of different faults during the same period, as well as in different segments of the same fault. Three phases of fault activity were identified in the study area: The Late Wenchang, Early Wenchang, and Enping Formations. Finally, the paper discusses the dynamic mechanisms during the rifting stage of the Baiyun sag, which corroborates previous views that it was a result of the coupled effects of the collision between the Indian and Eurasian plates, the rollback of the Pacific Plate subduction, and the continuous southward migration of the ancient South China Sea. This formed a typical extensional tectonic background in the study area. By revealing the fault activity characteristics and dynamic mechanisms in the Baiyun sag, this study contributes to Eocene rifting-stage oil and gas exploration in the northern South China Sea and provides important insights for analyzing fault activity in similar basins.

 Based on 3D seismic data, the mechanism of fault deformation and its control on hydrocarbon accumulation in the Zhu Ⅰ depression of Pearl River Mouth basin are studied by means of the determination of fault activity period, dislocation-distance curve and balanced section, in order to clarify the migration characteristics and distribution law of hydrocarbon source rocks. The results show that the Lufeng X sag is a north-south superhalf graben controlled by the NE-NEE-NWW arc fault (F1), and the NE, NEE and EW trending secondary faults are developed in the depression. The study is divided into two sub-depressions, east and west, according to the segmentation characteristics of the main fracture and the fracture combination style. The main fault is active in multiple stages, and has undergone three stages of tectonic deformation: Rift-Ⅰ, Rift-Ⅱ and Rift-Ⅲ. Five fault systems, namely, long-term active fault, Early Wenchang-Enping active fault, Early Wenchang-Enping active fault, Late Wenchang-Enping active fault and Enping active fault, have been formed in the basin with different deformation characteristics. In terms of origin, the internal fault of Lufeng X sag is generally controlled by the NE-NEE-NWW-arc-shaped pre-thrust and transformation fault system of the basement. In the basin forming period, the west sub-depression has extensional deformation along the pre-existing NE-NEE trending fault, and the east sub-depression has tension-torsion deformation along the pre-existing NWW-trending strike-slip fault. In the deformation process, the west sub-depression has formed a reverse cutting fault due to the influence of section reconstruction. The east sub-depression forms a special structural pattern of “V” shape. The controlling subsidence faults all have the characteristics of segmented growth, controlling the migration of sedimentary centers from northwest to southeast and from the edge of the basin to the basin, and affecting the distribution of source rocks in the 3rd and 4th member of the Wenchang Formation.

The sedimentary-tectonic evolution of Baodao sag in the Qiongdongnan basin is complex, with many sets of source-reservoir-seal assemblages in Baodao sag, Qiongdongnan basin. The south-north step-fault zone is the main oil and gas enrichment area in Baodao sag, the high-quality deltaic sand bodies in the Third Member of the Lingshui Formation of Paleogene are the main target beds. Based on the data of logging, seismic and geochemical data, this paper makes a comparative study on the static factors of gas enrichment in the Third Member of Lingshui Formation, and expounds the difference of gas dynamic accumulation by combining with basin simulation technology, the main control factors were summarized. The results show that the methane content is low and the non-hydrocarbon gas content is high in the northern step-fault zone, and the dry gas is the main gas in the southern step-fault zone. In the northern part of the step-fault zone, the medium porosity and low permeability reservoirs are mainly transported by T-type and Z-type mixed reservoirs, while in the southern part of the step-fault zone, the medium porosity, low permeability and ultra-low permeability reservoirs are mainly transported by Z-type reservoirs. The trap of block BD21-1 in the northern fault step zone was formed at the end of the Sanya Formation, and the structural high point of the trap turned to the east-west direction, in the early stage, the oil and gas generated in Yacheng Formation entered the reservoir through secondary faults. The trap in the northern part of block YL10-6 in the southern fault step was characterized as a small anticline trap at the F10-1 fault zone, which was formed at the end of the Sanya Formation and was influenced by compressive stress at the late stage. The Third Member of Lingshui Formation in the south-north step-fault zone experienced three stages of oil and gas charging. The gas differential enrichment depends on the differences in hydrocarbon potential of sub-depression, enrichment degree during primary migration, and preservation situation of secondary migration.

The reservoir of Meishan Formation in Ledong-Lingshui sag has become a research hotspot, and the study of diagenetic period and reservoir pore evolution in a high-temperature overpressure environment is extremely important in Qiongdongnan basin. In this paper, the diagenesis of Meishan Formation reservoir in Ledong-Lingshui sag was studied by synthesizing the data of thin sections, scanning electron microscopes, reservoir physical properties, carbon and oxygen isotopes, and clay X-diffraction, so as to determine the diagenetic symbiosis sequence and establish the pore evolution model. The results show that the reservoirs of Meishan Formation in Ledong-Lingshui sag have undergone various diagenesis processes such as compaction, cementation and dissolution, and the diagenetic sequences are as follows: early clay cementation→ calcite cementation→ feldspar, carbonate dissolution→ quartz increase, authigenic quartz particles→ iron calcite, iron dolomite cementation→ first-phase oil and gas charging→feldspar, carbonate mineral dissolution→ second-phase oil and gas charging. Under the influence of high temperature and overpressure, the development of cementation is inhibited and the dissolution porosity of diagenetic fluid is improved. The overall porosity increases due to the high temperature and remains unchanged under overpressure.

The exploration degree of buried hill limestone in Weixinan sag is low, and the exploration potential of remaining resources is large. Several buried hill oil fields or oil-bearing structures have been discovered around the No. 2 fault zone, which shows a good exploration prospect. In this paper, the development characteristics and karst structure identification of carbonate reservoir in No. 2 fault zone are systematically studied by using the data of drilling, logging, core, thin section and image logging, and the evolution and development model of karst reservoir in X structure is comprehensively analyzed according to the tectonic evolution and sedimentary background. The results show that the lithology of the buried hill of the X structure in the No. 2 fault zone is mainly limestone and lime dolomite, and the reservoir space is dominated by solution pores, caverns and fractures. The porosity varies from 0.01% to 35.88%, but the average value is only 4.30%. Taking well X-1 as an example, the supergene karst reservoir of X structure is divided into surface weathering zone, vertical seepage zone, horizontal subsurface flow zone and deep slow flow zone from top to bottom. The horizontal subsurface flow zone has the best karst fractures/caverns and is a high-quality reservoir development zone. The development degree of X tectonic fracture-cavern type limestone buried hill reservoir is mainly controlled by lithofacies, paleogeomorphology and late tectonic movement. The lithofacies determined the development degree of dissolution, and the tectonic movement caused differentiated denudation and formed a large number of fractures, which provided favorable percolation space for the later karst process. The paleogeomorphology controlled the relative position of the diving surface and thus controlled the development position of karst, and the high part of the karst slope was subjected to the strongest karst process. Based on three controlling factors, the three-element coupling reservoir development model of “lithology foundation building, fracture capacity expansion and karst reconstruction” is established.

In order to reveal the formation and evolution process of Pinghu fault zone, to determine the segmentation characteristics of large-scale faults and their geological filling response, and to deepen the understanding of the complex fault development mechanism, this article  based on the latest 3D seismic data, conducts geometric and kinematic analysis of Pinghu fault zone. Combined with regional stress field analysis, the genesis and development mode of the faults are discussed. The research results indicate that: Pinghu fault zone is an “X”-shaped fault zone consisting of three segments and five main faults that alternate between NE and near NS. The NE fault segment formed earlier and has segmented development characteristics, while the NS fault segment formed later and controlled the segmented connections of the southern, central, and northern sections. The formation of complex faults in Pinghu fault zone is jointly controlled by two factors: The segmented growth and development of faults, and the rotation of regional stress fields during the Eocene. The growth and evolution process of Pinghu fault zone during the fault depression period is divided into three stages: Early NE fault segmentation development stage, middle NE-near NS fault hard connection stage, and late NS-NNE/NE fault tension torsion transformation stage. The temporal and spatial differences in the development and evolution of Pinghu fault zone play an important controlling role in the migration of local sedimentary subsidence centers and the differential development of compression reversal anticlines in the later stages of the fault.

There are subaqueous eruptive volcanic rocks in  Huoshiling Formation of Chaganhua subdepression, Songliao basin, which are divided into two types of lithofacies and four types of subfacies. It is difficult to identify the subaqueous eruptive volcanic facies in actual production when there are few well cores. Taken  the subaqueous eruptive volcanic facies of Chaganhua area  as the research object, the logging characteristics of four subfacies of two types of lithofacies are analyzed and summarized in this paper: The undeveloped section of volcanic ash ball of the gas-carried subaqueous pyroclastic flow subfacies is high natural gamma and high resistivity, the curve is in the shape of medium-high amplitude finger, and the imaging logging shows high resistivity bright color. The developed section of volcanic ash ball is low natural gamma and low resistivity, the curve is flat with low amplitude, and the imaging logging shows low resistivity dark color. The water-carried volcanic high density flow subfacies is high natural gamma and high resistivity, the curve is in the shape of high amplitude finger, and the imaging logging shows high resistance bright color. The subaqueous landing subfacies is high natural gamma and low resistivity, the curve is low amplitude flat or in the shape of high amplitude finger, and the imaging logging shows low resistivity dark. The exoclastic pyroclastic sedimentary rock subfacies is low natural gamma and high resistivity, the curve is in the shape of high amplitude finger, and the imaging logging shows high resistivity bright color. The lithology logging recognition chart is established and the subaqueous eruptive volcanic lithology logging recognition is achieved.

The First Member of Qingshankou Formation in the Changling depression of the Songliao basin is a major exploration target for shale oil, but the current level of research on its paleoenvironment is relatively low. This paper studies the paleoenvironment changes based on elemental geochemical methods and analyzes the impact of environmental factors on organic matter enrichment, which is of great practical significance for clarifying the main controlling factors of shale oil enrichment and selected-area evaluation. 73 shale samples from the P1-P3 layers of the Upper Cretaceous Qingshankou Formation in the Changling depression were tested for total organic carbon and major and trace elements. The organic matter abundance and major and trace element characteristics of the samples in the study area were discussed. The paleoclimate, paleoproductivity, paleowater depth, paleosalinity, and paleooxidation of the target layer were restored using elemental geochemical indicators, and the paleoenvironmental change characteristics of the First Member of Qingshankou Formation in the study area were reconstructed. The results indicate that the organic matter abundance of shale in the study area is relatively high, with an average TOC of 2.14%. From the Daqingzijing to the Yuzijing to the Tahucheng work areas, as well as vertically from the P1 to P3 layers, the lake water deepens, and the paleoproductivity and organic matter abundance increase. The overall paleoclimate in the study area are warm and humid, with a slightly warmer and wetter climate to the P3 layer. The paleowater is characterized by an oxygen deficient reduction environment of fresh to brackish water, with high salinity forming salinity stratification, making the reduction environment in the study area less susceptible to damage and conducive to the preservation of organic matter. The source of organic matter and paleosalinity are the key factors that lead to the differential enrichment of organic matter in the study area. The input of organic matter and paleosalinity in lakes increases from Daqingzijing to Yuzijing to Tahucheng work area, organic matter is relatively enriched. Vertically, the P1 to P3 layers also exhibit similar patterns of change, forming a set of high-quality black shale in the lower part of the First Member of Qingshankou Formation, which is a favorable interval for shale oil enrichment in the study area.

 Lithofacies model is an important basis for the study of volcanic oil and gas reservoirs and  has important guiding significance for reservoir prediction and oil and gas reservoir evaluation. A major breakthrough has been made in Mesozoic volcanic rocks in Bohai Sea. With the deepening of exploration work, the inapplicability of volcanic facies models in other regions has become prominent in this area. In order to establish the volcanic facies model of Lower Cretaceous Yixian Formation in Bohai Sea, it provides a basis for the exploration and development of volcanic oil and gas in this area. There are abundant outcrop data in western Liaoning. Based on outcrop geological survey, the lithology, lithofacies and reservoir physical properties are comprehensively studied by means of rock and mineral identification, major and trace element analysis, particle size analysis and surface porosity analysis. The results are as follows, there are two kinds of volcanic emplacement environments in the Yixian Formation of western Liaoning Province: onshore and underwater. According to the classification scheme of five facies 15 subfacies 44 microfacies, three facies five subfacies nine microfacies are identified in this study, which are volcanic pyroclastic flow subfacies crater-near crater microfacies, base surge subfacies crater-near crater microfacies, near source microfacies and far source microfacies；Effusive facies subaerial lava flow subfacies simple lava flow microfaciesand composite lava flow microfacies, effusive facies subaqueous lava flow subfacies composite lava flow microfacies and autochthonous debris accumulation microfacies； Extrusive facies lava dome above water subfacies core microfacies. From high to low, the reservoir surface porosity is explosive facies, effusive facies and extrusive facies. The physical properties of the volcanic crater-near-volcanic microfacies of the pyroclastic flow subfaciesare better than those of the volcanic crater-near-volcanic microfacies of the base surgesubfacies, and the total surface porosity is larger. Effusive facies subaqueous lava flow subfacies autochthonous debris accumulation microfacies in nine identified microfacies have the best reservoir. The subfacies aspect ratio of effusive facies and extrusive facies is better than that of small reservoirs.

 There are favorable lava reservoirs in the Mesozoic Yixian Formation in the Bohai Bay basin, but lava reservoirs vary greatly in different phase structures, and there is an urgent need to establish the relationship between lithofacies and reservoirs applicable for early exploration. This study takes the lava of the Cretaceous Yixian Formation in Jianshan, Xingcheng, western Liaoning as an example. Comprehensive research on lithology, lithofacies, reservoir types, and reservoir controlling factors has been conducted using geological surveys, rock and mineral identification, major element analysis, and image analysis. The research results indicate that, based on the geometric shapes and petrofabric characteristics of volcanic rocks, the subfacies of subaqueous lava dome within the extrusive facies and the subfacies of subaqueous lava flow within the effusive facies have been identified. In the aquatic lava dome subfacies of the intrusive facies, the reservoirs are dominated by fissures, with no vesicular development, and the reservoirs are of average quality, showing a distribution pattern of good in top layers and poor in lower layers, low reserve-to-strata ratio, few reservoir layers, and limited distribution range. In the aquatic lava flow subfacies of the extrusive facies, the reservoir space of the simple lava flow microfacies is dominated by vesicular amygdale, and the reservoir is of good quality, showing a distribution pattern of good in upper layers and poor in lower layers, high reserve-to-strata ratio, a large number of reservoir layers, and large distribution range. The lava domes in the caldera-near caldera facies belt and the simple lava flows in the near-source facies belt of the volcanic edifice in the study area have been modified by tectonics and weathering. The lava domes experience great changes in physical properties, while the simple lava flows do not change significantly. In conclusion, when encountering residual lava-like volcanic edifices in volcanic exploration, simple lava flows with good reservoir properties in the near-source facies belt should be the first target, and lava domes with average reservoir properties in the caldera-near-caldera facies belt should be the secondary target.

 Cap rocks are  of great significance for effective reservoir characterization, reservoir quality assessment, and oil and gas reservoir development. The existing marine seismic prediction methods mainly focus on reservoirs, lacking research and analysis on the spatial distribution of cap rocks. It is urgent to establish a pre-stack seismic inversion prediction method for marine oil and gas cap rocks to provide technical support for the seismic prediction of marine oil and gas cap rocks. Therefore, this paper proposes a pre-stack seismic prediction method for marine cap rock facies and physical property parameters based on rock physics constraints, and conducts an in-depth study on the seismic description of  marine cap rock facies and physical property parameters. First, through the rock physics analysis of marine strata, the marine oil and gas cap rock facies and physical property sensitive elastic parameters are optimized. Secondly, based on the rock physics model, the seismic reflection coefficient equation and elastic impedance equation directly characterized by the lithofacies sensitive parameters and physical property parameters are derived respectively, providing technical support for the seismic characterization of the spatial distribution of the marine cap rock facies and the seismic prediction of the physical property parameters. In order to solve the problem of unstable inversion results caused by the correlation between model parameters, the singular value decomposition method is used to realize the decorrelation of model parameters in the seismic prediction process, and the inversion objective functions of sensitive elastic parameters and physical parameters of   marine cap rocks  are derived respectively under the framework of Bayesian inversion theory. This method is applied to actual data to verify the rationality and effectiveness of the pre-stack seismic inversion prediction method for marine oil and gas cap rocks. The results show that the Poisson impedance prediction accuracy can reach 95%, and the porosity prediction accuracy can reach 85%.

 In the eastern Ordos basin,  thin reservoirs in the Third Submember of the Second Member of Shanxi Formation (Shan23 Submember) of Daning-Jixian Block B are frequently closely associated with  carbonate rocks atop  Taiyuan Formation. These reservoirs are tight, with  complex lithology, small impedance difference between sandstone and mudstones strong heterogeneity, and great difficulty in reservoir prediction. In order to effectively improve the accuracy of quantitative interpretation of seismic data and implement the distribution characteristics of thin reservoirs in Block B, a novel prediction method for thin tight sandstone reservoirs amalgamating seismic phase, frequency extension and inversion phase has been proposed. This method firstly makes clear the characteristics of core facies, electrical logging facies and seismic facies of the reservoir based on  geological and logging data. Subsequently, spectral recovery and frequency extension technologies are used to improve the resolution of seismic data. Lastly, the lithology curves are regenerated, and waveform indicative inversion is performed using the high-resolution seismic data after frequency extension and the planar distribution of thin reservoirs is depicted to realize the quantitative prediction of tight and thin reservoirs in the Shan23 Submember of the study area. The results show that there are four types of seismic response characteristics for the target layer: ①Subaqueous distributary channel facies, characterized by a combination of strong, medium-weak and strong amplitude; ②Lateral area of  subaqueous distributary channel facies, characterized by a combination of strong, weak and strong amplitude; ③Sheet sand and distal sand bar facies, characterized by a combination of medium-weak, medium-strong and strong amplitude; ④Distributary bay facies, characterized by a combination of weak and strong amplitude. The dominant frequency of the seismic data is  increased from 30 Hz to 40 Hz, and the frequency bandwidth is  expanded from 10-60 Hz to 8-80 Hz, making more clear images for thin reservoirs in seismic data after frequency extension. The reconstructed curves show a good linear relationship between the sandstone thickness obtained from the post-frequency-extension seismic data inversion and the sandstone thickness from well, with a determination coefficient of 0.911 and a conformity of 84%. Based on the inversion data, horizontal well drilling is  guided, achieving a reservoir encounter rate of 95%.

 The Huajiling molybdenite deposit is a newly discovered molybdenum deposit located in the eastern section of the northern margin of the North China craton. It features an ore body oriented in NNW direction, dipping at 45° to 50°, surrounded by wall rocks of granite porphyry and granodiorite. The ore types include fine veinlet ores and disseminated ores, primarily consisting of molybdenite, magnetite and pyrite, with minor amounts of hematite. The alteration of wall rock involves dolomitization, potassium mineralization, silicification, chloritization, and carbonate mineralization. In order to determine the mineralization age, fluid properties and sources of ore-forming materials, this study conducted molybdenite Re-Os dating, fluid inclusion temperature measurements, and H-O-S-Pb isotope analysis on Huajiling deposit. Results indicate that the Re-Os age of Huajiling molybdenum deposit is (178.0 ± 1.1) Ma, formed in a tectonic environment where the ancient Pacific plate subducted beneath the Eurasian plate. The ore-forming fluid evolved from high temperature, low to medium salinity, and low to medium density to low temperature, low to medium salinity, and medium density. The δ18OH2O values of quartz range from -2.1‰ to 2.6‰, and δDV-SMOW values range from -115.8‰ to -109.7‰, indicating contributions from both magma water and atmospheric precipitation. The w(Re) values of molybdenite range from 19.564×10-6 to 23.128×10-6, exhibiting a crust-mantle mixed source. The δ34SV-CDT values of pyrite (1.9‰-4.2‰, with an average of 2.7‰) indicate that the sulfur mainly originates from the mantle. Additionally, the 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb values of pyrite range from 17.865-18.279, 15.546-15.611, and 38.011-38.486, respectively, further supporting the crust-mantle mixed source hypothesis for ore-forming materials.