The performance characteristics and the accurate prediction methods of overpressure in deep strata has become a hot topic in oil and gas exploration and development. Based on a lot of relevant literature and patent works of formation pressure prediction technology at home and abroad, the paper summarizes the challenges and problems in deep formation pressure prediction, the new progress and shortcomings of deep formation pressure prediction technologies, and the future research directions. The main understandings are as follows: (1) The classical pressure prediction theories and algorithms effectively applicable to the shallow and middle strata can not be directly applied to the study of more complexive deep formation pressure. (2) Due to the complex geological conditions, engineering difficulties, complex overpressure genetic mechanism, and the lack of prediction algorithm in deep strata, there is still great challenges and problems although the research based on porous elastic theory, petrophysical model, and tectonic pressurization has promoted the progress of deep pressure prediction. (3) Different from the common overpressure causued by undercompaction, the overpressure in deep strata is offen related to non-undercompacted mechanisms such as pressure transfer of structure and fault, hydrocarbon generation, and caprock sealing, which is often characterized by the coexistence of multiple mechanisms in the same areas and the various changes among different pressure systems. In order to accurately predict the deep overpressure, the more adaptable models are needed including the improved classical methods and formulas facing to the actual problems by analyzing the main and secondary overpressure mechanism. The seismic prediction technologies for the deep formation pressure that adapt to the complex lithology, the coexistence of multiple overpressure mechanisms and the variation of lateral pressure distributions, is the main research direction in the future.

The exploration targets for marine oil and gas in the Ordos Basin have gradually shifted from the early weathering crust reservoirs of the Majiagou Formation to the inner carbonate reservoirs below the unconformity at the top of Ordovician. However, the research level of deep Cambrian and Ordovician in the basin is relatively low, and the overall characteristics and configuration relationship of the source, reservoir, and cap rock are unclear. Based on the latest drilling and seismic data, combined with basic geological work such as field outcrop investigation, laboratory analysis, core and thin section observation, the author has compiled a series of maps of tectonics-lithofacies paleogeography, maps of hydrocarbon source rocks and favorable sedimentary facies zones, to clarify the development characteristics and configuration relationship of source, reservoir, and cap rocks of the Cambrian-Ordovician. The Cambrian system in the Ordos Basin has a structural pattern of inherited uplifts developing within the platform and inherited rifts developing at the platform edge. The southwestern and northeastern rifts of the basin control the development of Middle and Lower Cambrian source rocks mainly in the sea troughs and bays, while the Wushenqi and Qingyang ancient uplifts control the development of granular shoals and weathered crust reservoirs mainly in the periphery and platform edge zones of the ancient uplifts. The Ordovician has a sedimentary pattern of multiple uplifts and depressions developing within the platform, and the differential distribution of sedimentary facies is jointly controlled by sedimentary paleogeomorphology and sea level changes. The three uplift zones within the platform control the distribution of favorable microfacies such as granular shoal and gypsum dolomite tidal flat, while the two depression zones within the platform control the distribution of marine source rocks. Tectonic-sedimentary models of the platform margin rift in Cambrian and the platform inner depression in Ordovician control the development of source rocks and reservoirs, and form three sets of excellent sourcestorage-cap combinations, which have great potential for natural gas accumulation and are important areas for future risk exploration in the Ordos Basin.

The research of paleodrainage system is of great significance for the exploration and development of carbonate karst reservoirs. Based on restoration of paleogeomorphology, this paper utilizes the trend surface method, seismic frequency division coherence attribute analysis, fine coherence attribute analysis of superimposed seismic profiles, and RGB frequency division color mixing extracted along the weathered crust layer to delicately characterize the paleodrainage system of Majiagou Formation on the top of Middle Ordovician in the Fuxian area. The results show that: (1) The research area is located in the early Hercynian karstification zone, with a overall characterisic of being high in the southwest and low in the north and east, and the paleogeomorphology can be divided into four third-class units: residual hill, platform, terrace and trench. (2) Two types of palaeodrainage systems, surface and subsurface, are developed in the study area. The surface palaeodrainage system is developed in the southwest high part (southwest region), which is nearly symmetrical dendritic and dominated by deep-cut meandering currents. And the subsurface palaeodrainage system is developed in the northeast structurally low part (northeast region), which is dominated by dark rivers and subterranean flows, with stronger karstification and more collapses, and sinkholes. The surface and subsurface jointly constitute a deep- cut meander-subterranean flow development model. (3) Karst remnant mounds and platforms are favorable areas for the development of high-quality reservoirs. In this study, a variety of methods are used to describe the paleodrainage system, overcoming the limitations of single technology. The combination of multiple morphological features enhances the reliability of identifying surface and subsurface palaeodrainage systems, determines the development locations of dominant reservoirs, and provides important reference significance for the exploration and development of the Lower Palaeozoic in the study area.

Dolomitization and dolomite distribution are the key factors that restrict the development and distribution of reservoir of the 2nd member of Maokou Formation in central Sichuan Basin. Based on the previous research results of dolomite and the understanding of regional geological background, through the observation of core and thin sections, and the introduction of cathode luminescence, X-ray diffraction, inclusion, C and O stable isotope, Sr isotope and REE analysis, the further study of dolomitization of the 2nd member of Maokou Formation in central Sichuan Basin has been carried out. The results show that: (1) There are three types of dolomite in the study area: very fine-fine crystalline anhedral dolomite, very fine-medium crystalline euhedral dolomite, and saddle dolomite. Very fine-fine crystalline anhedral dolomite is formed by syngenetic evaporative seawater dolomitization. This dolomitization does not produce reservoir space itself, but plays a fundamental role in the formation of dolomite reservoirs. Very fine-medium euhedral dolomite is formed by burial dolomitization in the early diagenetic period, and the intergranular pores and intergranular dissolution pores are developed at the site of dolomitization, which can form dolomite dissolution pore type reservoir. Saddle dolomite is formed by hydrothermal dolomitization in early diagenetic period (Dongwu period). This dolomitization is accompanied by hydrothermal fracture and hydrothermal dissolution, which can lead to the development of dissolution fractures and the formation of dolomite dissolution fracture and cavernous reservoirs. (2) Marginal platform, coupling with the platform margin fault，is the best place to develop syngenetic seawater dolomitization, burial dolomitization and hydrothermal dolomitization in the early diagenetic period, and is also the advantageous development zone of dolomite reservoir. In the intra-platform highland area, syngenetic evaporative seawater dolomitization and burial dolomitization in the early diagenetic period are mainly developed, making it a relatively favorable zone for dolomite reservoir development. However, intra-platform depressions lack favorable conditions for dolomitization, resulting in poor dolomite development.

The marine shales of Wujiaping Formation and Dalong Formation in Sichuan Basin have favorable conditions for shale gas accumulation, making them significant replacement fields for natural gas exploration in the future. However, due to mixed sedimentation influences, diagenesis and pore evolution vary significantly among different lithofacies. The lithofacies classification, diagenesis, and microscopic pore structure of Wujiaping Formation and Dalong Formation shales of Well DY1H in northeast Sichuan Basin are confirmed by useing X-ray diffraction, scanning electron microscopy, energy spectrum analysis, and thin section observation techniques. We also discuss the coupling relationship between diagenesis and pore development. The results reveal that four types of shale lithofacies are predominantly present in well DY1H: siliceous, mixed, calcareous, and clay-rich shales. The siliceous shale has the highest TOC. Part of the quartz in the siliceous shale comes from the transformation of siliceous organisms in the early diagenesis. This early cementation enhances the compaction resistance of the reservoir, and the retained micropores can provide space for the migration and enrichment of organic matter. With the increase of burial depth, a large number of organic pores can be formed under the thermal evolution of organic matter. Due to their high-quality material foundation and favorable storage conditions, siliceous shales have become preferred lithofacies within the Wujiaping Formation and Dalong Formation shales in northeast Sichuan Basin. Finally, a diagenetic pore evolution model is established specifically for these favorable lithofacies which can serve as a reference for studying pore genesis and reservoir distribution prediction in marine shales.

Many exploration wells in the southern margin of Junggar Basin have obtained high-production oil and gas flow from the Lower Cretaceous Qingshuihe Formation in wells, which proves that high-quality reservoirs is developed in Qingshuihe Formation. Based on the paleo-geomorphologic data, this paper analyzes the differences in sedimentary facies of the bottom sand body of Qingshuihe Formation, the reasons for the stable distribution of sand bodies, and the distribution patterns of different rock types, by combining analysis of the sand body structures, petrologic characteristics, heavy mineral assemblages and paleocurrent characteristics of the reservoir. The study suggests that before the deposition of Qingshuihe Formation, the paleo-geomorphology of the southern margin in Junggar Basin was characterized by the development of a steep-slope area in the south and a large gentle-slope area in the north, whereas two slope breaks were globally developed in the gentle-slope area. During the depositional period of Qingshuihe Formation, the study area was in the process of lake transgression, and retrogradational braided-river deltas and fan deltas were formed under the control of paleo-geomorphology. In the southern steep-slope area, fan deltas depositional system was developed, and the thickness of sandstone and conglomerate reservoirs is at the range of 10-30 m. In the northern gentle-slope area, three stages of regressive braided-river deltas depositional system were developed under the control of two slope breaks, resulting in the widely developed sandstone reservoirs in the middle and northeastern parts of the southern margin in Junggar Basin. The sandstone reservoir formed by northern and northeastern source system with a thickness of 20-50 m and relatively good physical properties, making it a favorable reservoir development area for the Qingshuihe Formation.

Since the 1980s, the porous dolomite reservoir of Huanglong Formation of Carboniferous in Sichuan Basin has been an important exploration object and a key production layer in the east Sichuan Basin. With the gradual increase of reserves utilization, it is urgent need for discovery and replacement of new reserves. In recent years, with the addition of high-quality seismic data, combined with drilling and outcrop data, comprehensive geological analysis of Carboniferous strata, Silurian hydrocarbon sources and reservoir-forming conditions on the western side of Huaying Mountain has been made, and three main understandings have been obtained: (1) Carboniferous strata are distributed in a large area on the western side of Huaying Mountain. The favorable area of carbonate rocks is over 8 000 km 2 , and the predicted thickness is up to 40 m, which provides stratigraphic and sedimentary basis for the formation of large-scale reservoirs. (2) Pingchang- Bazhong and Guang ' an-Quxian large trap groups with a total area of 5 460 km 2 are developed under the control of paleo- uplift slope belt, stratigraphic denudation belt and fault belt, which have favorable conditions for large-scale reservoir formation; (3) The Pingchang-Bazhong trap development area, if the Carboniferous reservoir is developed, has good gas source conditions, well-developed structural traps, and favorable accumulation combination of lower sources and upper reservoirs, so it is a favorable area to explore for large-scale natural gas reserves.

Post-rift magma is widely distributed in Jiaojiang Sag, East China Sea Basin. However, the type, spatial distribution and formation period of magmatism have not been systematically studied, which seriously limits the oil and gas exploration and deployment in the basin. Based on the newly acquired high-precision 3D seismic data, drilling data，this paper identifies and finely describes the magma in the post-rift period, and determines the development regulation of magmatism and the control effects on oil and gas accumulation in Jiaojiang Sag. The results show that the volcanic rocks are mainly distributed in the central and eastern parts of Jiaojiang Sag, with overflow facies as the main type. They are developed along the T 20 interface and up and down, but more developed along the T 20 interface. There are three types of occurrences of magma intrusion, including saucer, sill, and dike, with saucer being the main occurrence. The emplacement of magma intrusions in the Jiaojiang Sag mainly include three stages: before the Wenzhou stage (>43 Ma), during the Pinghu-Huagang stage (43-23.3 Ma)，during and after Longjing stage (<23.3 Ma), and the Pinghu-Huagang stage is the most important period for magma intrusion. The distribution of magma intrusion channels in the study area are related to the northwest striking basement hidden faults, but separated from the Cenozoic faults and have no symbiotic relationship between them. It is traditionally suggested that the magmatism in the post-rift stage may cause damage or alteration to early oil and gas reservoirs, therefore, when selecting potential targets, efforts should be made to avoid the influence of magmatic activity as much as possible. On the other hand, magma intrusion has formed a large number of forced anticlines, and their formation time is later than the peak period of oil and gas generation, which belongs to a good potential trap type. Therefore, these forced anticlines in the magma-rich activity area within Jiaojiang Sag are still worth exploring.

Structural fracture is an important condition for obtaining high gas yield from the deep tight glutenite reservoir of the Cretaceous Yageliemu Formation in KT-1 gas reservoir of Kuqa Depression. To study the distribution and effectiveness of structural fracture is conducive to favorable reservoir prediction of Yageliemu Formation. Based on core and imaging logging data, the characteristics of structural fractures in Yageliemu Formation of KT-1 gas reservoir are described, and the distribution of structural fractures is semi-quantitatively predicted by finite element method. The effectiveness of structural fractures is evaluated from two aspects: time and space effectiveness. Finally, the numerical simulation of structural fracture is carried out under the condition of constant horizontal stress and increasing gravity load of overlying strata. The results show that the glutenite reservoir of Yageliemu Formation in KT-1 gas reservoir develops tensile fractures and shear fractures, mainly at medium-high angles, and the dominant trend is NW-SE, which has a good correspondence with the maximum paleotectonic stress orientation in the NNW direction. There are at least two stages of fracture in Yageliemu Formation of KT-1 gas reservoir. The first stage of fracture is invalid, which was formed before the depositional period of the Neogene Kangcun Formation. The second stage of fracture is effective formed in the depositional period of the Pliocene Kuqa Formation-Quaternary (5 Ma until now), which has a good matching relationship with natural gas charging, and is an important condition for the formation of large-scale natural gas reservoir. The fracture spatial effectiveness is mainly controlled by the fracture density and fracture opening. The fracture density in the high position of anticline of KT-1 gas reservoir is lower than that in the wing, but the fracture opening is larger and the fracture permeability is significantly higher than that in the wing, which is an important reason why Well KT204 located in the wing has the highest fracture density but the lowest gas production. The numerical simulation results show that in a certain depth range, with the increase of reservoir buried depth, the density of structural fractures decreases, but the aperture and permeability increase significantly, and the effectiveness becomes significantly better, which is more conducive to the efficient flow of natural gas in the reservoir.