Oil/gas resources is rich in marine strata in China, due to the evolution history of complicate tectonics and the variation of thermal system, the features of formation and accumulation of marine oil/gas reservoirs are relatively complicated. The variation of geotemperature field would result in the multistage hydrocarbon-generating of source rocks;Multistage tectonic movements result in the multistage reservoir-forming and adjustment, reconstruction and damaging; During the later period, strong tectonic deformation made the marine oil/gas reservoirs generate very late. The favorable tectonic positions such as marine paleo-uplift, promising reservoiring belts and paleo-fault belts, are regarded as the main areas for exploration.

High-quality clastic reservoirs deep-buried in superimposed basins of China, with many layers and wide distribution, are the important oil and gas reservoir bodies and exploration targets, which are also key conditions to increase in the exploration effect in seeking for large-scale, high-quality clastic reservoirs in deep superimposed basins. Five reservoir's types, including low-thermal-maturation, solution-pores, fracturepores, high pressure-resistant and heat-resistant, and high fluid-pressure, are the typical better clastic ones, which are also advantageous exploration targets of superimposed basins in China. Among these types, the low-thermal-maturation reservoir is formed by rapid burial and overthrust structure in the later period, mainly controlled by the geothermal gradient, the thermal evolution path as well as the structure deformation history of the basin; Dissolution-pore reservoir may be divided into the meteoric water leaching dissolution and the organic acid dissolution, mainly controlled by the scale of unconformity and the condition of acid dissolution; Fracture-pore reservoirs often form in middle-later diagenesis period, including structure fracture-pore and crushed fractures pore. High pressure-resistant and heat-resistant reservoir may bemainly controlled by rock structure and the rigid component content, such as quartzose sandstone and siliceous sandstone and so on. Due to the abnormal formation could restrain the diagenesis evolution of high-pressure-fluid reservoir, so this type are controlled by formation pressure coefficient, the origins and the period of abnormally high pressure fluid originated.

Ordos Basin is a large multicycle superimposed basin, developed on the basement of early Proterozoic crystalline basement. Its evolution progress had undergone four developed stages,i.e. middle-late Proterozoic aulacogen basin , Paleozoic craton basin ,Mesozoic foreland basin and Cenozoic fault-depression basin in its adjacent region. Due to multistages of basin evolution, two series of source rocks and many combinations of reservoir-caprock are developed.With the multicycle of sedimentary structures and formation evolution, superimposed basin has difficulty in exploration, long time needed for exploration, and large potential of exploration. From the regional, natural gas exploration should be focusing on the central-eastern part of Ordos Basin. On the stratum, natural gas exploration should be eyed on the Ordovician weathering crust and upper Paleozoic fluvial-delta reservoirs. With the development of exploration, on the guidance of ideas to deep and to area, west and south of the basin on the area, Cambrian oolitic limestone and Ordovician dolomite rock deposited in the 4th member of Majiagou Formation and dolomite under the sub-salt, will be the new targets of exploration in Ordos Basin.

The abundance of organic matter in Ordovician source rock of Pingliang Formation is rather high in western Ordos Basin. The organic matter is mainly typeⅠand at the stage of high to post maturity. Gas generation potential is large, total gas generation quantity is about 151 trillion cubic meters, and gas resource amount is up to 936.2 billion cubic meters. The rate of gas generation is fast in the western margin thrust zone of Ordos Basin and it is favorable for gas accumulation. In this area, the two intervals of carbonate reservoirs have been developed, dolomite reservoir in the 4th member of Majiagou Formation in Ordovician and Kelimoli Formation's weathering-crust reservoir. The direct seal and up-dip lower Carboniferous mudstone cover have the strong sealing ability. Therefore, the condition of gas accumulation is superior in this area, and it has the geological advantages to form large- and medium- sized gasfields. According to the relation among source, reservoir and cover,it is thought that Etuokeqi-Dingbian and Tianchi-Bulike areaswould be the favorable targets for natural gas exploration in the future.

The Silurian is composed of upper member of Kepingtage Formation, Tataaiertage Formation and Yimugantawu Formation from the bottom to the top.There are grey and grey-white fine sandstone, middle sandstone and siltstone, green-grey mudstone, silty mudstone, mudy siltstone in Silurian in Tazhong area. The author presents the shore-neritic shelf depositional system, in which sandstone body types include shore beach, tidal flat, neritic sand bar, shelf sand and etc. Foreshore-nearshore beach facies, neritic sand bar, neritic shelf facies were developed in the lower bitumen-bearing sandstone member during Silurian period in Tazhong area, Tarim basin. There are mainly tidal flat depositional system in the upper bitumen-bearing sandstone member and Tataaiertage Formation and Yimugantawu Formation. There are transgressive, aggradational and progradational parasequence sets, in which the superimposition by different parasequences constitutes the three third-order sequences of Silurian stratum .Sequence correlation shows Silurian transgression onlapped from northwest to southeast direction. The sandstone body, developed in transgression system tract (TST), better reservoir are mainly located near the maximum marine flooding surface, i.e. the favorable position for marine sandstone body development would be the upper part of TST and the lower part of high system tract (HST). Silurian oil/gas show and bitumen-bearing sandstone mainly distributed in the third-order sequence near the maximum marine flooding surface. Oil/gas reservoirs types include lithologic reservoirs, which are superimposed by many bedded sandstone lens in vertically and horizontally, and fault-anticline reservoirs controlled by structures.

Junggar Basin is a large composite and superimposed basin, which is developed from the basement of micro- plate after suture and accretion and Paleozoic island-arc belts, controlled by the evolution of paleo-Asian ocean and its peripherial orogenic belt. Since Phanerozoic eon, the basin has undergone five cycles of tectonic evolution, i.e. the extension-subduction cycle of Cambrian-middle Silurian north Junggar ocean, the pull-apart and convergent cycle of late Silurian-early Carboniferous Kelameili limited ocean-basin, fully extinct cycle of late Carboniferous -Triassic paleo-Asian ocean, the intra-continent fault-depression cycle during the period of early Jurassic-Eogene and the strong transpressional and convergent orogenic cycle during the period of Neogene and Quaternary. During the extending period, the stable sequences of original basin often develops better source rock, and in convergent period, the proto-type basin was suffered from reconstruction, and this period becomes the development stage of structural trap or oil/gas accumulation. In addition, after resuming the evolution process of the basin, it is pointed out that the Devonian-Carboniferous will become new target for oil/gas exploration in Junggar Bain in the future

Junggar Basin is one of key regions of petroleum resources increase in China, and is characterized by oil/gas accumulation of "multisource, multi-stage and multi-type secondary reservoir formation".Through the study for key techniques of superimposed basin, it is put forward that the law of oil/gas enrichment in the basin,and three stages foreland basins developed in the basin evolution history ,giving the different significance in petroleum geologic evolution. Basin superimposed style controls the law of oil/gas enrichment: (1)Oil/gas accumulated at positive position of inheriting and extending plaeo-uplift;(2)Fault cut and reconstructed petroleum accumulation, as a result, the scope of petroleum distribution was enlarged, and the number of oil-bearing beds was increased, which resulted in oil/gas mixed-generating of different sources and made the features of oil/gas distribution complicated;(3)Due to the interrupted change of unconformity, the bottom conglomerate over the unconformity and the weathering crust under the unconformity became the favorable pathways of oil/gas migration;(4) The reservoircap rock combination, controlled by early Cretaceous maximum lake flooding surface, might be important litho-stratum oil/gas reservoirs developed in medium-shallow strata of the basin.

Chepaizi-Mosuowan paleo-uplift in Junggar Basin belongs to southwest-eastnorth Yanshan paleo-uplift, its area is more than 20000 sq. km. In the deep part of Chepaizi-Mosuowan paleo-uplift at present, low-amplitude anticlines and nose structures also exist; however, the shallowstructures are simple, fault is not developed. The evolution of Chepaizi-Mosuowan paleo-uplift can be divided into five stages, i.e. uplift formation stage, slowly growing stage, violently developing stage ,subtle and burial stage as well as reconstructing and adjusting stage. Chepaizi- Mosuowan paleo-uplift have provided with the conditions to form the various subtle traps such as lithologic and stratigraphic traps, and good settings for oil/gas migration and accumulation, which are favorable to generate the large-scale and regional oil/gas reservoirs inside the basin.

A oversized anticline trap exists in deep Carboniferous of Mosowan uplift in Junggar Basin, but to explore deep oil/gas successfully, it is crucial to determine whether volcanic rocks exists in the upper Carboniferous or not. By comparing the features of oil/gas reservoirs in Mosuowan uplift with those in its adjacent region, it is indicated that there are the large difference of magnetic and seismic anomaly between volcanic and sedimentary rocks, but the magnetic anomaly and seismic facies feature of Moshen-1 well on the top of Mosuowan uplift are similar to those in oil/gas field in Shixi uplift, which is approached to the magnetic anomaly of middle-acid volcanic rocks, standing in the transition belt from strong to weak magnetic anomaly. The analysis result of seismic facies shows that the majority of Mosuowan uplift has the feature of strong amplitude reflection, and weak amplitude reflection ismainly distributed in the southeast sag ofMosuowan uplift. By integrating the magnetic anomaly and seismic facies feature, it is inferred that the upper Carboniferous in Mosuowan uplift would have the following lithologic-facies characteristics: middle-acid volcanic rock plus sedimentary rocks are mainly distributed in the central part of the uplift, and middle-basic volcanic rocks are distributed in the southwest and northeast limbs, and sedimentary rock is occurred in the southeast limb (Fang- 2 well area) of the uplift, the central-southern part of Dongdaohaizi sag and Lunan-1 well area. The late reconstruction of Carboniferous volcanic rocks in Mosuowan uplift has four favorable conditions, it is, therefore, inferred that the Carboniferous volcanic reservoirs would be well developed in the uplift.

Through new correlation and interpretation of seismic profiles, the new idea has formed to understand the tectonic framework, formation and evolution of Qaidam Basin. It is thought that in Quaternary and Tertiary, Qaidam Basin is a superimposed basin developed under the different tectonic backgrounds.During Tertiary, the basin is mainly located in the west ofWutumeiren-Dachaidan fault zone, and inQuaternary, it is mainly situated in the east ofWutumeiren-Dachaidan fault zone. Yiliping sag belongs to the main superimposed area generated by the basin during the two periodsQuaternary and Tertiary. TertiaryQaidam Basin formed during earlyHimalayanmovement, grewduringmiddleHimalayan movement, and died out in later Himalayan movement, underwent a whole process from fault-depression, depression and reversal to uplift. In lower Tertiary, there are several depositional centers in Qaidam Basin, in Miocene and Pliocene period, the basin has a relatively uniform depositional centre, in the later period, tectonic deformation was much more strong, and faults and folds developed. The Quaternary basin, formed in later Himalayan movement, is a strike-slip basin, the depositional centre moved straight forwardly toward the east, tectonic deformation wasweak, these structures are syn-depositional ones, the amplitude is relatively small. QaidamBasin has the uniquepetroleum geologic conditions, so we must adopt the unconventional idea and method to explore for oil and gas in this basin, the big discovery could be discovered in the syncline position and structure fractures.