Abstract:Abstract：The sedimentary basin incorporates organic and inorganic， metallic and non-metallic mineral deposits， forming a relatively independent mineral resource-hosting unit and an reservoir-forming （mineralization） macro-environment， which may be called the sedimentary basin reservoir-forming （mineralization） system. The system is generally located in a low-temperature， low-pressure environment and an open system， in which mineralizing fluids， organisms/organic matter （fluids） play a vital role and are significantly affected by temperature changes. Mineralization generally has no direct genetic relationship with magmatic activities.The initial occurrences of mineralizing materials that form sedimentary deposits are mostly scattered； from their initial accumulation through mineralization to mineral deposit formation， marked changes take place in their environment. They generally experience a process from primitive mineralizing material accumulation→mineralization→enrichment， mineral deposit formation， reworking and reposition. The driving force of migration of mineralizing materials mainly comes from compaction and abnormal pressure， tectonism， seepage flow， molecular diffusion， volatilization and buoyancy force. The main passageways of migration are pores， faults formed by tectonic processes and microfractures and unconformity produced by non-tectonic processes. The relationships between mineral source rocks and reservoirs are highly varied， including such associations as self-generating and self-accumulation， late generation and early accumulation， early generation and late accumulation. The sites where sedimentary minerals are deposited are generally traps （e.g. anticlinal， fault and lithologic traps） sealed by mudstones and evaporites with poor permeability or abrupt boundary transformation zones of geochemical environment， tectonic features and lithology-lithofacies. Generally， the time interval between primitive mineralizing material accumulation and mineral deposit formation-redeposition may be long， even up to several hundred million years. The formation of sedimentary mineral deposits usually progresses through a mineralization process， generally characterized by multiple mineralization phases and marked reworking in the late phase， which results not only in repeated superimposition and further enrichment of a mineral deposit but also in its reworking and modification or formation of a secondary mineral deposit. The above-mentioned characteristics determine that the sedimentary mineral deposit forms and especially is sited relatively late. The useful sedimentary minerals in a basin are rich， with diverse features. Their mineralization and distribution pattern have complex relations and show the diversity of coexistence， synthetic affinity and exclusivity. The above-mentioned characteristics vary somewhat in different types of sedimentary mineral deposit and each type of deposit has its own characteristics. According to different tectonic dynamic environments， the basin mineralization system may be divided into various types， such as the rift extension， convergence， transformation and cratonic types， and the mineral deposits in various environments differ in mineralization characteristics， types， distributions and combinations. Affected obviously by the evolution of the hydrosphere， atmosphere and biosphere on the earth's surface in the geological history and its reversibility， the formation of exogenous sedimentary mineral deposits of the basin is generally characterized by significant stages， development with time and more complex mineral types. The enrichment and deposit formation of sedimentary minerals in the basin system also show characteristics of obvious spatial regionalization and partial enrichment. Owing to its own mineralization characteristics and reservoir-forming/mineralization environments， the sedimentary basin reservoir-forming/mineralization system should be proposed as an independent mineralization system that stand side by side with and is distinguished from other mineralization systems such as orogenic and shield mineralization systems. The special study of it will certainly reveal the intrinsic relation between various types of sedimentary mineral deposit and their coexisting basin as well as their reservoir-forming patterns and distribution characteristics and enrich and develop the system of mineralization theories. Moreover， it lays a theoretical foundation for overall consideration of multiple mineral deposits in the basin， scientific and high-efficiency mineral exploration and comprehensive prediction.

Abstract:Abstract：An integrated analysis of the distribution of the apatite and zircon fission track ages and its relation to coarse clastic sediments and stratigraphic unconformity provides the chronological constraint on the Meso-Cenozoic tectonic events and their sedimentary response in the Ordos basin. The Indosinian tectonic event mainly occurred at 230-190 Ma with two statistic peak ages (195 and 215 Ma). On the southwestern margin of the basin there occur Late Triassic coarse clastic molasse-like deposits, which have a disconformable contact with the overlying strata. The Yanshanian tectonic event mainly occurred at 150-85 Ma with three statistic peak ages (145, 120 and 95 Ma) in the mid-late Yanshanian. On the southwestern margin of the basin there occur middle Yanshanian Late Triassic and Early Cretaceous coarse clastic molasse-like deposits and angular unconformity. The Himalayan tectonic event is mainly marked by polycyclic tectonic uplift of the basin at a regional scale, including at least three statistic peak age events at 55, 25 and 5 Ma respectively. The peak age of 145 Ma offered by zircon and apatite fission tracks and its related angular unconformity, overthrusting and regional magmatic activity all indicate a key Meso-Cenozoic tectonic reworking event in the Ordos basin.

Abstract:Abstract：Most predecessors held the view that the western Ordos basin was tectonically a foreland basin during the Late Triassic. This paper questions the validity of this view mainly based on the following three lines of evidence. First, three sequences of coarse clastic sediments in the Late Triassic Yanchang Formation in the Rujigou, Shigouyi and Kongdongshan areas on the western margin of the basin were revisited. The Yanchang Formation in the Rujigou area is of marginal facies indeed, but the appearance of intraplate basalt in the horizon nearby suggests that the Yanchang Formation in the area was deposited in an extensional environment during the Late Triassic. Recent study indicates that the Yanchang Formation in the Shigouyi is not very thick, less than 1500 m in thickness. The conglomerate in Kongdongshan is not typical of the sediments in the western part of the basin because it was probably influenced by the Qinling-Qilian orogen to the southwest of the Ordos basin. Secondly, through the compilation of the isopach map of the Late Triassic Yanchang Formation and several E-W-trending stratigraphic correlation sections it is found that a N-S-trending, very thick subsidence belt, as thought previously to be present in the western part of the basin during this period, does not exist. Finally, through the analysis of the seismic profile, balanced cross section and fission track data, the authors think that the present Hengshanbu back-thrust belt and large-scale Majiatan thrust nappe belt did not form in the Late Triassic but in the Late Jurassic. Therefore, tectonically the western Ordos basin was not a foreland basin during the Late Triassic but a component part of a superposed basin in a residual and extended craton.

Abstract:Abstract：A uniform E-W compressional thrust nappe model was constructed for the north and south of the western Ordos block on the basis of a study of the structure of the western Ordos block conducted in the 1970s-1980s. However, this model has become more and more difficult to explain real geological problems as petroleum exploration and research in the area go on. In addition, the structural model of the uniform E-W-trending movement and N-S zoning in the western Ordos block is questioned, no large-scale foreland basin exists in the area and such problems as the transverse structural belt, N-S zoning and N-S-trending movement are presented—all these indicate that the complexity and diversity of the regional structures in the western Ordos block should be reconsidered. In analyzing and summarizing the structural characteristics and development model in the area, we should strengthen a comprehensive study and continuously supplement, revise and improve our original knowledge.

Abstract:Abstract：This paper analyzes in detail the characteristics of sandstone dikes in outcrops and cores in the Late Triassic Yanchang Formation in the Ordos basin and preliminarily elucidates the formation mechanism and evolutionary process of the sandstone dikes. The unconsolidates fine sands deposited in the early stage were liquefied in the late stage in response to earthquakes, and meanwhile with rapidly increasing pressures inside sands, the liquefied sands were injected into the fissures in surrounding rocks very quickly, thus forming sandstone dikes. According the above-mentioned analysis, combined with the tectonic setting, the authors think that sandstone dikes acted as conduits for oil migration and also exerted a certain influence on the formation and destruction of oil accumulations.

Abstract:Abstract：Based on data of logs, cores and outcrops, the characteristics of the stratigraphic sequence and sedimentary facies of the Yanchang Formation in the Longdong area, Ordos basin, are studied. Four third-order sequence boundaries are recognized in the formation. The authors divide the formation into four third-order depositional sequences and ten systems tracts. Four main depositional systems are identified： the fan delta, braided river delta, meandering river delta and lacustrine sedimentary systems. The distribution characteristics of the depositional systems in various systems tracts are analyzed and the depositional models of the systems tracts and the relationship between depositional sequences and petroleum are also discussed. The authors think that the sand bodies in channels of the delta plain and subaqueous distributary channels in the delta front in the lowstand systems tracts are main reservoirs, the sand bodies of turbidites in transgressive and highstand systems tracts are potential reservoirs, and the lacustrine mudstone and shale developed in transgressive and highstand systems tracts are good source rocks and cap rocks-all these show that the Longdong area is located in a favorable petroleum-bearing system with favorable source-reservoir-cap assemblages and has good petroleum prospects.

Abstract:Abstract：The indications for identification of sequence boundaries of different order are analyzed in detail according to the theory of high-resolution sequence stratigraphy and on the basis of the observations and descriptions of the main field outcrops and cores of the Upper Triassic Yanchang Formation in northern Shaanxi, Ordos basin, combined with abundant well logging curves. The results indicate that there are one super long-duration depositional cycle, four long-duration depositional cycles, nine medium-duration cycles and some short-duration cycles in the Yanchang Formation. Affected by the Indosinian movement, two regional uplift and subsidence surfaces (SLSB2 and SLSB1) of tectonic movement formed in the study area and the two sequence boundaries are the top and bottom of a super long-duration cycle. The long-duration cyclic sequence is a regional lake transgressive-regressive depositional sequence and its boundary is a low-angle erosion unconformity and its corresponding conformity. There are three long-duration cyclic sequence boundaries in the study area; they are in ascending order：(1) the transgressive boundary formed by regional base-level elevation, which is approximately equivalent to the “Lijiapan shale”; (2) the regional marker bed of mudstone and tuff, which is approximately equivalent to marker bed k2 located at the bottom of oil layer set Chang 6; and (3) the regional facies transition boundary, which is approximately equivalent to the boundary between layer sets Chang 4+5 and Chang 3. The medium- and short-duration cyclic sequence boundaries are lake flooding surfaces of different orders, erosion surfaces, transition surfaces of rock types or facies groupings, surfaces of bedding change within rock facies and boundaries of cyclic change in thickness of sandstone and mudstone. On the basis of identifying boundaries, the depositional cycles and spatial distribution of boundaries in the study area are analyzed. The identification of boundaries of different orders is the key to the study of high-resolution sequence stratigraphy and plays an important role in petroleum exploration and exploitation.

Abstract:Abstract：The authors analyzed the directions of paleocurrents and main sediment sources and features of parent rocks in the provenance during the deposition of the Sixth Member of the Yanchang Formation and studied the features of the parent rocks of the provenance based on the framework grains, heavy minerals, cathodoluminescence of framework grains and REE features of sandstone in the strata in the Yangjiayuanze oil prospect area, Zichang oilfield, northeastern Ordos basin, combined with measurements of the paleocurrent direction on typical outcrops located on the northeastern margin of the Ordos basin. The study shows that the paleocurrents and main sediment source were derived from the northeast during the deposition of the Sixth Member of the Yanchang Formation. The parent rocks of the provenance are mainly metamorphic rocks with a small amount of igneous rocks. The study is of great theoretical and practical significance for an analysis of the tempo-spatial distribution of sandstones of the Yanchang Formation in the northeastern Ordos basin, evaluation of favorable hydrocarbon accumulation areas and arrangement of further hydrocarbon exploration in the study area.

Abstract:Abstract：Permian source rocks are important and potential source rocks in the Ordos basin. A systematic analysis of the trace element and REE geochemistry and organic geochemistry of argillaceous carbonate rocks and mudstones has been carried out mainly according to the geochemical data of the well core samples. The LREE abundance is high and the HREE abundance is low and Ce/Ce* has a relatively pronounced positive anomaly, indicating that the source rocks were deposited in a reducing environment. The contents of trace elements in the source rocks are significantly different from their clarke values in similar rocks in the Ordos basin. Study shows that grayish black mudstone source rocks deposited in semi-deep lake-deep lake facies zones are strongly reduced and rich in organic matter, where organic matter could be buried timely, and grayish black mudstone source rocks deposited in a fluvial-swampy environment have a low organic matter abundance. The strongly reduced depositional facies zone with a fairly deep water body was an ideal locus for deposition of primary organic matter, where the organic matter could be buried and preserved timely; whereas organic matter abundance was obviously low in argillaceous carbonate source rocks deposited where the climate was dry with little precipitation and terrigenous clastic material supply was inadequate or in a long-term oxidizing environment.

Abstract:Abstract：The laser Raman technique has the merits of easy operation and more accuracy. Through the laser Raman microprobe analysis of bitumen in oil we can study the composition and evolution of bitumen in oil. Oil bitumen in the Ordos basin widely contains reducing gases such as CH4 and, in addition, some samples also contain oxidizing gas such as CO2. They have an antithetic relation. This relation and the antithetic range also reflect the degree of late-stage reworking of the basin.

Abstract:Abstract：Sm-Nd isotope study has been performed on chloroform bitumen in oil, coal, uranium-bearing sandstone and its country rocks in the Ordos basin. The results indicate that the activity of fluids (including deep fluids) in the basin shows the multi-stage character, and that the late-stage fluid activity played a significant role in the formation of uranium deposits. Uranium-bearing sandstone bitumen, oil bitumen and coal bitumen in the same sequence of strata have the enriched mantle features, but they are not products of the same stage. A comparison between the coal bitumen in the Jurassic Zhiluo Formation of the Dongsheng field and that in the Jurassic Yan'an Formation of the Chengjiashan field in the southwest of the basin indicates that: there is appreciable difference in ages of the bitumen sources; the associated bitumen did not all form by thermal evolution of coals but might contain exotic fluids, and the associated bitumen in coals of the Zhiluo Formation was derived from an even deeper source than that in coals of the Yan'an Formation in the Dongsheng field. There is some internal genetic relation between the oil bitumen of the Zhiluo Formation in the Maling oilfield and the coal bitumen and oil bitumen in the coal bed of the Ya'nan Formation of Chengjiashan in the Ordos basin.

Abstract:Abstract：On the basis of the statistic analysis of the oil tests and data of production of 110 wells in the study area, the paper summarizes the areal and vertical variations of oil content in the Lijiacha prospect area in the east of the northern Shaanxi slope and discusses the cause of the high water content. The water content in the study area is high in the north, low in the south, low in the center and high in the east and west and vertically has the trend of becoming low from the base upward. According to the source rock and physical conditions and a comparative study of these conditions with neighboring areas, the authors think that: the lack of hydrocarbon is the most important cause for the high water content in the oil reservoir of the Lijiacha prospect area, the poor migration conditions are an important cause and the low-porosity and -permeability reservoir conditions are also one of the causes for the high water content.

Abstract:Abstract：In the Longdong area, Changqing oilfield, Ordos, casing corrosion and damage influence oil production seriously. The main cause is thought to be electrochemical and biochemical reactions between casing and formation water of Na2SO4 type in the Cretaceous Luohe Formation. The desert-facies sandstone of the Luohe Formation distributed uniformly in the whole basin is characterized by high permeability and homogeneity, so it can provide good conduits and spaces for the recharge, runoff and discharge of groundwater and the resulting strong leakage field accelerates casing corrosion and damage. Analysis confirms that only relying on raising the quality of casing and cementing is not enough to prevent casing corrosion and damage in the study area, and only by using new materials and technologies can we solve this problem.

Abstract:Abstract：This paper presents the following distinctive characteristics of the Dengsheng sandstone-type uranium deposit in the Ordos basin: (1) there exist a pronounced ore-controlling green alteration zone and the bleaching phenomenon in the deposit; and (2) discontinuous, lenticular, carbonated, calcareous-cemented sandstone is widespread in the ore horizon. X-ray diffraction analysis, SEM identification and analysis of the inclusion chemical composition of clay minerals indicate that the green alteration and bleaching phenomenon formed in an extensive reducing environment, and that the reducing fluids are mainly related to hydrocarbon escape. Carbon isotope analysis of fill-up gas and carbonates and analysis of part of organic geochemical parameters in the ore horizon indicate that the above-mentioned alteration is mainly related to NE-directed escaped hydrocarbon alteration of coal gases containing components such as CH4, H2S, CO and CO2. So, it can be thought that the basin margins in the direction of hydrocarbon escape and front of the green alteration zone are favorable areas for uranium mineralization and ore finding.

Abstract:Abstract：The formation of sedimentary uranium deposits has close relation to organic matter. Experimental simulation study indicates that: aromatic organic acid is very easy to coordinate with uranyl ions under the weakly acid to weakly alkaline conditions and the oxygen atoms of its carboxyl coordinate with uranium atoms in a variety of coordination forms to form coordinate bonds. The results of the experiment simulation validate some previous conclusions and intuitionally exhibit some migration forms of main organic matter functional groups and uranyl ions in solution. The results also show the reduction of hydrocarbon in the formation of uranium deposits under hydrothermal conditions. It can reduce U (Ⅵ) into U (Ⅳ) and deposit the latter.

Abstract:Abstract：The authors used the hydrocarbon accumulation-forming dynamic system and sandstone-type uranium mineralization dynamic system to analyze the relationship between the mineral deposit (petroleum accumulation) assemblage belt and sedimentary system in which the sandstone-type uranium deposit and petroleum accumulation. They think that it is a common geological phenomenon that repeated migration of hydrocarbon promotes sandstone-type uranium mineralization, which is manifested as follows: primary migration results in preconcentration of uranium mineralization, secondary hydrocarbon migration ends early oxidation zone-type uranium mineralization and seals uranium orebodies in the gray strata, and slight leakage of the petroleum accumulation leads to uranium concentration and mineralization in red sandstone. Furthermore, according to the reduction effect of hydrocarbon on the sandstone-type uranium deposit, the authors have constructed the Tuha-, Dongsheng- and Qianjiadian-type basic models of coexistence of the petroleum accumulation and sandstone-type uranium deposit in the same basin, which enrich the theory on search for sandstone-type uranium deposits and provide reference for comprehensive development and utilization of multiple energy resources.

Abstract:Abstract：Gamma energy spectral survey is a direct method for uranium prospecting. However, because of lower grades and deep burial, sandstone type uranium deposits occurring in Meso-Cenozoic sedimentary basins have low and uniform gamma-ray values and show no pronounced radioactive anomaly information in the airborne gamma spectral measurements above and around a uranium orebody. So the anomaly is difficult to recognize using conventional data processing methods (e.g. mono-element distribution trend analysis and mono-element ratio). In this case, the element parameters U, Th and K are combined for the airborne gamma spectral measurements, and furthermore, the authors have constructed a mathematical model of multi-element combination parameters to enhance and extract weak information of gamma energy spectral data relating to sandstone type uranium deposits, used the cluster analysis and logical regression analysis in the mathematical statistics to perform integrated evaluation of the prospect area and gave the metallogenetic probability of sandstone type uranium deposits. Experiments demonstrate that, in comparison with routine methods, the use of multi-element combination parameters to enhance and extract weak information of airborne gamma energy spectral data from the Shihongtan and Alxa Youqi areas can significantly enhance weak information about prospecting of sandstone type uranium deposits. Therefore, this method is an effective and applicable method for forecasting areas favorable for sandstone type uranium mineralization.

Abstract:Abstract：The fact that oil, natural gas, coals and sandstone uranium minerals exist in the same basin and form a mineral deposit provides favorable conditions for co-exploration of multiple energy minerals. The seismic and well logging methods have been widely used in exploration of various energy minerals. So co-exploration of multiple energy minerals is possible in terms of techniques and methods. Because the degree of exploration of oil, natural gas and coals is generally higher than that for sandstone uranium at present, we should use the available data (seismic and logging data) of exploration of oil, natural gas and coals to look for sandstone uranium deposits in co-exploration of multiple energy minerals in the basin. According to the statistics, more than 300 oil/gas wells have been drilled in the prospect areas of sandstone uranium deposits at the peripheries of the Ordos basin, such as the Tianhuan subbasin, thrust belts on the western edge of the basin, Yimeng uplift and western Shanxi flexural fold belt. These wells provide abundant seismic and logging data for exploration of sandstone uranium.

Abstract:Abstract：According to the diagenetic sequence of the reservoir, characteristics of oil-gas inclusions and homogenization temperatures of hydrocarbon-bearing saline inclusions and isotope dating of authigenic illite, combined with the tectonothermal evolution history and fission-track path data, an integrated study has been performed on the stages of coalbed methane accumulation in Permo-Carboniferous coalbeds and roof sandstone in the Qinshui basin. The authors think that two stages of hydrocarbon injection occurred in the methane accumulation. The first stage occurred in the terminal Triassic to Early Jurassic, when the main coal seams of the Shanxi and Taiyuan formations were in a mature stage and liquid hydrocarbon and gas-liquid hydrogen inclusions formed; and the second stage took place in the Late Jurassic to Early Cretaceous, corresponding to the phase of thermal cracking of kerogen, when large amounts of coalbed methane were produced, so the stage is the main accumulation stage of Permo-Carboniferous coalbed methane. The age of authigenic illite in roof sandstone, Shanxi Formation, is ~191 Ma, which implies that the Early Jurassic was the earliest time for filling of oil/gas desorbed from coalbeds methane in the sandstone reservoir with basin uplift and erosion.

Abstract:Abstract：The age assignment of the Xiangshan Group has long been controversial since its establishment. Regional geological data indicate that the Xiangshan Group is Middle-Late Cambrian in age. In order to discuss the sedimentary environments and tectonic setting of the Xiangshan Group on the southwestern margin of the Ordos basin, the petrological and geochemical characteristics of cherts in the Langzuizi Formation of the Xiangshan Group are analyzed. The analysis of cherts suggests that: the SiO2 content is 82.44%-98.13%, the Al/(Fe+Mn+Al) ratio ranges from 0.46 to 0.69 and Al2O3/(Al2O3+Fe2O3) is 0.53-0.77; the fractionation between LREE and HREE is strong with LREE/HREE=3.57-8.45, LaN/CeN is 0.66-1.15 and Ce/Ce* is 0.66-0.93. These characteristics show that the cherts formed in a continental-margin environment and that the diagenetic processes included hydrothermal deposition and normal deposition. The geochemical characteristics of clastic rocks and diabase sills in cherts indicate that: clastic rocks were also deposited on the passive continental margins and diabase belongs to the oceanic tholeiite series formed in an extensional setting. An integration of geological data suggests that an environment of divergent continental-margin nature occurred on the southwestern margin of the Ordos block and the southern margin of the Alxa block during the Mid-Late Cambrian.

Abstract:Abstract：The Yanqi basin of Xinjiang is a Meso-Cenozoic basin. According to the field survey and strata/rock geochemical analysis of the Lower Jurassic Badaowan Formation in the basin, the authors think that: the source area lies in the north of the basin and fragments were transported from north to south, with coarse fragments deposited in the north and fine fragments in the south; braided stream facies sediments occur in the north of the Yanqi basin, while lakeshore and shallow lake facies sediments in the south; and the new apatite fission track data show that the mountains on the western, southern, and northern margins of the Yanqi basin were uplifted late; and Jurassic strata still remain in mountains around the Yanqi basin at present. All these show that the primary sedimentary boundary of the basin is wider than that of the present basin. Based on the above analysis and its comparison with the Kuqa basin, the authors find that the Yanqi basin was connected with the Kuqa basin and that the two basins were a part of the Tarim basin in the Badaowanian period.

Abstract:Abstract：Recently major advances have been made in the study of Ordovician sedimentary reservoirs in Lunnan, Tarim Basin. Three weathering crust reservoir systems of two phases have been found: one Hercynian reservoir system occurs at the top of the Ordovician and two Caledonian systems in the interior of the Ordovician. The Ordovician reef bank-facies reservoir in Lungudong is determined to be a weathering crust karst fissure-cave one, and a reef bank-facies reservoir is found in the Sangtamu Formation. In the early deposition of the Sangtamu Formation, a reef-forming environment occurred, with small organic reefs developed locally. The previous division of Ordovician sedimentary facies is revised, and the location of the Ordovician carbonate platform margin is shifted eastward for 30 km. The thermal subsidence mechanism is proposed for the interpretation of the formation of the weathering crust reservoir inside the Ordovician. It is thought that there existed a thermal uplift and subsidence movement in the Tarim basin during the early Late Ordovician, which resulted in nonuniform uplift of the Lunnan area and erosion and exposure of the Lianglitag Formation, thus forming the weathering crust karst reservoir system in the area and revealing good petroleum prospects in the Lunnan area.

Abstract:Abstract：The present geothermal gradient of the Huh Lake depression is 3.54℃/100 m, so it is a middle-temperature geothermal field. The paleogeothermal gradient reconstructed by the vitrinite reflectance, microthermometric measurements of fluid inclusions and fission-track path method was 3.7-6.5℃ /100 m, which is higher than the present geothermal gradient, and the ancient subsurface temperatures are higher than the present subsurface temperatures. The reconstruction of the paleogeothermal gradient and modeling of the thermal history indicate that the maximum paleogeothermal values were reached in the Late Cretaceous and that the paleogeothermal field controlled the maturity of Lower Cretaceous hydrocarbon source rocks. Study of the relation between the thermal history and hydrocarbon shows that the formation of hydrocarbon in the Huh Lake depression mainly progressed through two stages: the late Early Cretaceous stage and stage since the Paleogene, with the late Early Cretaceous being the main stage of hydrocarbon accumulation. The intensity of hydrocarbon generation has become weak since the Paleogene with decreasing temperatures in the target strata.

Abstract:Abstract：Study of the petrological and physical characteristics, reservoir opening space types and formation and evolution of volcanic rocks in the Cretaceous Yingcheng Formation in the Shengping gas field, Songliao basin, shows that the major volcanic reservoir rocks are lavas, pyroclastic rocks and sedimentary-volcanic rocks, with rhyolite predominating, in addition to small amounts of dacite and andesite. The volcanic gas reservoir spaces are dominated by secondary solution pores (cavities), with subordinate primary pores and fissures. The evolution of the volcanic reservoir rocks involves the early and late phases. The early phase was characterized by volcanic activity, when mainly primary pores including vesicles and pores between volcanic fragments; the late phase included cooling of lavas and epi-petrogenesis of volcanic rocks, which was the main period of formation of volcanic reservoir spaces. The erosion and weathering surfaces as well as faults and fractures in the study area were main conduits for gas migration and also favorable reservoir spaces for gas accumulation.

Abstract:Abstract：According to the latest data from several energy resource evaluation agencies, the authors make an integrated statistic study of the total resources, supply and demand of the world's energy minerals, including oil, gas, coal and uranium and then analyze the characteristics of their changes. On that basis, they propose the supply-demand balance coefficient S to evaluate the balance and stability state of supply and demand of energy minerals. The lower the absolute value S is, the more balanced the supply and demand will be, but this does not mean the stability of supply and demand; only when S is a low and positive value and fluctuates little on the axis of time, can the supply and demand relationships reach balance and stability. By combining the statistic data from various sources and using the analogy and trend analyses, this paper presents an outlook for the supply and demand relationships of the world's energy mineral resources.