Geological reservoir and resource potential(10^(13)m^(3))of gas hydrates in the South China Sea

A detailed understanding of the distribution and potential of natural gas hydrate(NGHs)resources is crucial to fostering the industrialization of those resources in the South China Sea,where NGHs are abundant.In this study,this study analyzed the applicability of resource evaluation methods,including the volumetric,genesis,and analogy methods,and estimated NGHs resource potential in the South China Sea by using scientific resource evaluation methods based on the factors controlling the geological accumulation and the reservoir characteristics of NGHs.Furthermore,this study compared the evaluation results of NGHs resource evaluations in representative worldwise sea areas via rational analysis.The results of this study are as follows:(1)The gas hydrate accumulation in the South China Sea is characterized by multiple sources of gas supply,multi-channel migration,and extensive accumulation,which are significantly different from those of oil and gas and other unconventional resources.(2)The evaluation of gas hydrate resources in the South China Sea is a highly targeted,stratified,and multidisciplinary evaluation of geological resources under the framework of a multi-type gas hydrate resource evaluation system and focuses on the comprehensive utilization of multi-source heterogeneous data.(3)Global NGHs resources is n×10^(15)m^(3),while the NGHs resources in the South China Sea are estimated to be 10^(13)m^(3),which is comparable to the abundance of typical marine NGHs deposits in other parts of the world.In the South China Sea,the NGHs resources have a broad prospect and provide a substantial resource base for production tests and industrialization of NGHs.

Growth behavior and resource potential evaluation of gas hydrate in core fractures in Qilian Mountain permafrost area, Qinghai-Tibet Plateau

The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.

Resource Potential and Exploration Techniques of Stratigraphic and subtle Reservoirs in China

The onshore oil and gas exploration has stepped into a new stage in China, with equal attention paid to both stratigraphic and subtle reservoirs and structural reservoirs. In the past few years, the increases in oil reserves in most basins were found mainly in the stratigraphic and subtle reservoirs. Latest resource evaluation shows that the onshore stratigraphic and subtle reservoirs in China account for 42% of the total remaining resource, the highest in the four major exploration regions. Therefore, these reservoirs will be the most practical, potential and prevalent fields for long-lasting oil and gas exploration in onshore China. Among PetroChina's annual oil geologic reserves of 4.3 × 108t^4.6× 108t, the stratigraphic and subtle reservoirs account for more than 50%. In such basins as Songliao, Ordos, Bohai Bay, Junggar, Tarim, Sichuan and Erlian basins, stratigraphic and subtle reservoirs with geologic reserves ranging from 5×107t to 3×108t were discovered, including Ansai, Jing'an, Daqingzijing, Liuxi, well-21 area in Shinan, and Hadexun. Stratigraphic and subtle reservoirs in the four types of inland basins differ from each other in the formation conditions and the distribution patterns. While continental basins are controlled by unconformity surface, maximum flooding surface and fracture surface, the Paleozoic marine basins are influenced by paleouplift, unconformity surface, and fluctuation of the sea level. Through exploration practices and research, PetroChina has formed its own technique series focused on 3-D seismics and sequence stratigraphy.

Uranium Metallogenic Regionalization and Resource Potential in China

This paper is comprehensively involved in main types of uranium deposits and their general metallogenic characteristics, metallogenic fields, provinces, regions and belts, and uranium resources potential evaluation. Generally speaking, there are favorable conditions and good uranium resources potential for uranium mineralization in China.

The copper polymetallic deposits and resource potential in the Tibet Plateau

Many large and super-large copper deposits have been discovered and explored in the Tibet Plateau,which makes it the most important copper resource reserve and development base in China.Based on the work of the research team,the paper summarizes the geological characteristics of the main copper deposits in Tibet and puts forward a further prospecting direction.A series of large accumulated metal deposits or ore districts from subduction of Tethys oceanic crust to India-Asia collisionhave been discovered,such as Duolong Cu(Au)ore district and Jiama copper polymetallic deposit.The ore deposits in the Duolong ore district are located in the lowstand domain,the top of lowstand domain,and the highstand domain of the same magmatic-hydrothermal metallogenic system,and their relative positions are the indicators for related deposits in the Bangong Co-Nujiang metallogenic belt.The polycentric metallogenic model of the Jiama copper polymetallic deposit is an important inspiration for the exploration of the porphyry mineralization related to collision orogeny.Further mineral exploration in the Tibet Plateau should be focused on the continental volcanic rocks related to porphyry-epithermal deposits,orogenic gold deposits,hydrothermal Pb-Zn deposits related to nappe structures,skarn Cu(Au)and polymetallic deposits,and the Miocene W-Sn polymetallic deposits.

Basin structure and multiresource potential based on high-precision airborne gravity and magnetic data

In this paper,we use high-precision airborne gravity and magnetic data to study the geophysical characteristics of the western slope of the Songliao Basin and its adjacent areas and evaluate the resource potential.We performed an in-depth analysis of three aspects of the basin characteristics:the characteristics of residual strata,the development characteristics of faults,and the distribution characteristics of magmatic rocks.Next,we analyzed the forming background of organic(oil and gas)resources and inorganic(uranium ore and hot dry rock)resources.The results showed that the new Upper Paleozoic strata have significant differences in different regions of the study area(with a thickness of 0–8000 m),mainly distributed in the eastern and northern regions but absent in the middle eastern and western regions.Furthermore,the thickness and depth of the Mesozoic layer varied between the eastern and western regions;it was thicker and deeper in the middle eastern region but thinner and shallower in the western region,and it is absent in most western regions.The main faults in the region are in the north–northeast(NNE)direction.Faults in the NE–NNE and NW directions jointly controlled the morphology of the secondary structural units.Magmatic rocks are relatively developed in the middle and eastern parts of the region.Most magmatic rocks are distributed along the faults and their sides,clearly reflecting the control of the faults on magmatic activities.The western slope of the Songliao basin and its surroundings have a favorable geological setting for the accumulation(mineralization)of oil,gas,shale oil,hot dry rock,and uranium ore.It is conducive to oil and gas exploration of deep new strata and collaborative exploration of multiple resources.

Evaluation of groundwater resource potential by using water balance model:A case of Upper Gilgel Gibe Watershed,Ethiopia

Groundwater resource potential is the nation’s primary freshwater reserve and accounts for a large portion of potential future water supply.This study focused on quantifying the groundwater resource potential of the Upper Gilgel Gibe watershed using the water balance method.This study began by defining the project area’s boundary,reviewing previous works,and collecting valuable primary and secondary data.The analysis and interpretation of data were supported by the application of different software like ArcGIS 10.4.1.Soil water characteristics of SPAW(Soil-plant-air-water)computer model,base flow index(BFI+3.0),and the water balance model.Estimation of the areal depth of precipitation and actual evapotranspiration was carried out through the use of the isohyetal method and the water balance model and found to be 1664.5 mm/a and 911.6 mm/a,respectively.A total water volume of 875829800 m^(3)/a is estimated to recharge the aquifer system.The present annual groundwater abstraction is estimated as 10150000 m^(3)/a.The estimated specific yield,exploitable groundwater reserve,and safe yield of the catchment are 5.9%,520557000 m^(3)/a,and 522768349 m^(3)/a respectively.The total groundwater abstraction is much less than the recharge and the safe yield of the aquifer.The results show that there is a sufficient amount of groundwater in the study area,and the groundwater resources of the area are considered underdeveloped.

Fractal Principle of Mineral Deposit Size Forecasting and Its Implication for Gold Resource Potential Evaluation in China

Mineralization distributions are very heterogeneous in nature. As large orsuperlarge mineral deposits are quite rare whether in time or in space, it is difficult to detectall the largest mineral deposits in a region in a limited period of time owing to the restriction oftechnology and exploration degrees-this is called 'not all discovered'. However, all discoveredlarge, especially superlarge, mineral deposits generally have a complete census in the geologicalliteratures. On the other hand, not all discovered small mineral deposits are recorded in thegeological literatures because for economic reasons people have not much interest in them-this iscalled 'not all recorded'. This practice often results in the observation truncations, that is, thedata points near the two ends in an observable population, which is obtained by fitting a power lawsize-frequency distribution to discovered mineral deposits in a given region, show concave-downdeparture from the correlation line fitted. The authors suggest that the size and number ofundiscovered deposits may be forecast by fitting a fractal size distribution to discovered mineraldeposit sizes between the upper and lower truncation observations and then extrapolating thescale-independent area to deposit sizes larger than the upper truncation limit. Based on thestatistical results obtained by the fractal size-frequency distributions of 394 discovered golddeposits with sizes greater than 2 t Au in China and 83 known gold deposits with sizes over 0.3 t Auin the Jiaodong area of China, the authors forecast according to the present commercial standardsfor gold ores that the total resources of undiscovered gold deposits ranging in tonnage from 50 to2000 t Au are more than 4500 tin China, and that in the Jiaodong area of China the total resourcesof potential gold deposits with sizes in the range of 30 to 650 t Au are about 700 t.

Enrichment mechanism and resource potential of shale-type helium:A case study of Wufeng Formation-Longmaxi Formation in Sichuan Basin

China’s helium resource is highly dependent on overseas imports.Organic-rich and U/Th-rich shale reservoirs generally contain helium,and although the helium content is low,the total reserve is large.Therefore,the effective development and utilisation of shale-type helium resources is a realistic way to improve the security of helium resources in China.In this study,the generation mechanism,helium source and content,migration modes and pathways,controlling factors of enrichment,distribution pattern,and resource potential of the helium were analysed,using the Wufeng-Longmaxi shale in the Sichuan Basin and its periphery.Furthermore,countermeasures were proposed for shale-type helium exploration and development.The results show that the Wufeng-Longmaxi shale has a high content of U and Th and a good ability to generate helium.The helium is generated by a typical crustal source of helium and is characterised by self-generation,self-storage,and wide distribution.The helium resource potential is a product of its content and the resources of the associated natural gas.The continuous supply of helium and effective preservation are the main geological factors that control the enrichment of shale-type helium.The preliminary evaluation results show that the reserves of helium in proven shale gas reserves are 10.8×10^(8)m^(3)in the Sichuan Basin and its periphery,where the extra-large helium fields are likely to be discovered.Additionally,0.0912×10^(8)m^(3)of helium was produced,along with the annual production of shale gas.To avoid the waste of helium and to improve the self-supply ability,it is suggested that research on the resource potential,enrichment mechanism,and distribution pattern of shale-type helium should be carried out as soon as possible,and helium extraction techniques for helium-bearing natural gas should be studied.

Deep geothermal resources in China:Potential,distribution,exploitation,and utilization

Deep geothermal resources mainly refer to the thermal energy stored in subsurface rocks and fluids therein at a depth of 3-10 km,which is a kind of renewable and sustainable clean energy unaffected by weather and seasonal changes.Large scale exploitation of the deep geothermal resources is of great significance to ensuring national energy security and achieving the“Carbon Peak and Carbon Neutrality”.Based on the latest terrestrial heat flow data,this paper estimated the potential of deep geothermal resources in the terrestrial areas of China,and the results show that the total amount of geothermal resources within 3e10 km under the Earth's surface in the terrestrial areas of China is 24.6×10^(15)GJ.In line with climate zones categorized,the geothermal resource proportion is 43.81%for severe cold regions,29.19%for cold regions,6.92%for mild regions,13.82%for hot summer and cold winter regions,and 6.26%for hot summer and warm winter regions.Statistics according to the burial depth range reveal that the resources within depth ranges of 3-5 km,5-7 km and 7-10 km under the Earth's surface are 4.3119×10^(15)GJ,6.37674×10^(15)GJ and 13.89594×10^(15)GJ respectively,showing an increasing trend of geothermal potential with increasing burial depth.The deep geothermal resources are mainly of medium-to-high temperature reserves,and the energy supply strategy can be optimized by combining the climate conditions and population distribution,as well as considering power generation.In regions of cold or severe cold climate,the geothermal resources may be applied to geothermal power generation and district heating in combination;in regions of hot summer and cold winter or mild climates,the resources can be used for geothermal power generation combined with cooling and heating;in regions of hot summer and warm winter climates,the resources may be applied to geothermal power generation combined with cooling and industrial and agricultural utilization.Exploitation of deep geothermal resources also can be combined with carbon dioxide sequestration,multi-mineral resources extraction and energy storage to realize comprehensive exploitation and utilization of various energy resources.It is suggested that theoretical technology research should be combined with pilot tests and field demonstrations,and large-scale economic exploitation of deep geothermal resources should be arranged in a coordinated manner,following the principles of overall planning and step-by-step implementation.

Lacustrine Shale Oil Resource Potential of Es3L Sub-Member of Bonan Sag, Bohai Bay Basin, Eastern China

Following shale gas, shale oil has become another highlight in unconventional hydrocarbon exploration and development. A large amount of shale oil has been produced from a host of marine shale in North America in recent years. In China, lacustrine shale, as the main source rock of conventional oil and gas, should also have abundant oil retained in place. In this study, geochemical and geologic characteristics of lacustrine shale from Es3L sub-member in Bonan sag were characterized by using total organic carbon（TOC）, Rock-Eval pyrolysis, X-ray diffraction, and ？log R method. The results show that the Es3L sub-member shale have TOC contents ranging from 0.5 wt.% to 9.3 wt.%, with an average of 2.9 wt.%. The organic matter is predominantly Type I kerogen, with minor amounts of Type II1 kerogen. The temperature of maximum yield of pyrolysate（Tmax） values ranges from 424 to 447 ℃, with an average of 440 ℃, and vitrinite reflectance（Ro%） ranges from 0.7% to 0.9%, indicating most of shales are thermally mature. The dominant minerals of Es3L shale in Bonan sag are carbonates（including calcite and dolomite）, averaging 51.82 wt.%, and the second minerals are clay（mostly are montmorillonite-illite-mixed layer and illite） and quartz, averaging about 18 wt.%. Finally, its shale oil resources were evaluated by using the volumetric method, and the evaluation result shows that the shale oil resource is up to 5.94 billion tons, and mostly Class I resource. Therefore, the exploration of the lacustrine shale oil of Es3L in Bonan sag should be strengthened.

Gold Resources Potential Assessment in Eastern Kunlun Mountains of China Combining Weights-of-evidence Model with GIS Spatial Analysis Technique

Resources potential assessment is one of the fields in geosciences,which is able to take great advantage of GIS technology as a substitution of traditional working methods.The gold resources potential in the eastern Kunlun Mountains,Qinghai Province,China was assessed by combining weights-of-evidence model with GIS spatial analysis technique.All the data sets used in this paper were derived from an established multi-source geological spatial database,which contains geological,geophysical,geochemical and remote sensing data.Three multi-class variables,i.e.,structural intersection,Indosinian k-feldspar granite and regional fault,were used in proximity analysis to examine their spatial association with known gold deposits.A prospectivity map was produced by weights-of-evidence model based on seven binary evidential maps,all of which had passed a conditional independence test.The study area was divided into three target zones of high potential,moderate potential and low potential areas,among which high potential areas and moderate potential areas accounted for 20% of the total area and contained 32 of the 43 gold deposits.The results show that the gold resources potential assessment in the eastern Kunlun Mountains has a higher precision.

Alteration and Reformation of Hydrocarbon Reservoirs and Prediction of Remaining Potential Resources in Superimposed Basins

Complex hydrocarbon reservoirs developed widely in the superimposed basins of China formed from multiple structural alterations, reformation and destruction of hydrocarbon reservoirs formed at early stages. They are characterized currently by trap adjustment, component variation, phase conversion, and scale reformation. This is significant for guiding current hydrocarbon exploration by revealing evolution mechanisms after hydrocarbon reservoir formation and for predicting remaining potential resources. Based on the analysis of a number of complex hydrocarbon reservoirs, there are four geologic features controlling the degree of destruction of hydrocarbon reservoirs formed at early stages： tectonic event intensity, frequency, time and caprock sealing for oil and gas during tectonic evolution. Research shows that the larger the tectonic event intensity, the more frequent the tectonic event, the later the last tectonic event, the weaker the caprock sealing for oil and gas, and the greater the volume of destroyed hydrocarbons in the early stages. Based on research on the main controlling factors of hydrocarbon reservoir destruction mechanisms, a geological model of tectonic superimposition and a mathematical model evaluating potential remaining complex hydrocarbon reservoirs have been established. The predication method and technical procedures were applied in the Tazhong area of Tarim Basin, where four stages of hydrocarbon accumulation and three stages of hydrocarbon alteration occurred. Geohistorical hydrocarbon accumulation reached 3.184 billion tons, of which 1.271 billion tons were destroyed. The total volume of remaining resources available for exploration is -1.9 billion tons.

Development potential and technical strategy of continental shale oil in China

Continental shale oil is a general term for liquid hydrocarbons and many kinds of organic matter in continental organic-rich shale series with vitrinite reflectance of more than 0.5%at buried depth of more than 300 m,and is an important type of source-rock oil and gas.Based on the evolution model of oil generation and expulsion in organic-rich shale series controlled by maturity,continental shale oil is divided into two types:medium-high maturity and medium-low maturity.(1)The continental shale series in China develop high-quality source rocks of freshwater and saltwater lacustrine facies,as well as multiple types of reservoirs,including clastic rocks,carbonate rocks,diamictite,tuff and shale,forming a number of"sweet sections"and"sweet areas"of continuous distribution inside or near source rocks,which have large scale resources.(2)Experimental analysis of organic rich shale samples shows that the shale samples with wavy and horizontal beddings have good storage conditions,and the horizontal permeability of shale is tens to hundreds of times of its vertical permeability,which is conducive to the lateral migration and accumulation of shale oil in the source rocks.(3)After evaluation,the geological resources of medium-high maturity shale oil are about 10 billion tons,which can be effectively developed by horizontal drilling and volumetric fracturing,and will be a practical field of oil exploration in recent years.Shale oil with medium and low maturity has huge resource potential,and technological recoverable resources of(70?90)billion tons,making it a strategic alternative resource of oil industry.However,economic development of this type of shale oil needs in-situ conversion technology breakthroughs.Continental shale oil is an inevitable choice in the process of Chinese continental petroleum exploration from"outside source"to"inside source".Making breakthroughs in the core technologies such as"sweet area"evaluation and optimization,horizontal well volume fracturing and in-situ conversion technology and equipment is the key to realizing scale development of continental shale oil economically.

Uranium Potential and Regional Metallogeny in China

This paper is briefly involved in distributions of China＇s uranium metallogenic types, provinces, regions and belts. Eight target regions have been pointed out to be worthy of prospecting for uranium resources. The regional uranium metallogeny is discussed and great uranium potential pointed out from many aspects. Generally speaking, there are favorable conditions for uranium mineralization and good perspective to explore for uranium resources.

Evaluation of groundwater potential and eco-geological environment quality in Sanjiang Plain of Heilongjiang Province

Sanjiang Plain of Heilongjiang Province has become an important commodity grain base in our country after the construction of more than a century. Groundwater is the main water source for industrial and agricultural production and daily life in the area. With the large-scale development and construction in this area, there are a series of ecological and environmental geological problems, such as the reduction of groundwater resources, which seriously restricts the sustainable development of local agriculture and society as well as economy. Based on the characteristics of three-dimensional flowof groundwater in Sanjiang Plain, this paper adopts the simulation software Visual MODFLOW to evaluate groundwater exploitation potential. The results show that overall there is a certain exploitation potential of Sanjiang Plain groundwater but it is unevenly distributed, and overdraft phenomenon exists in seven farms such as Baoquanling and Chuangye. Based on analytic hierarchy process, the evaluation result of eco-geological environment quality in Sanjiang Plain shows that 94.5% of the region features good geological environment quality, medium stability and medium bearing capacity. The study can provide geological evidence for optimal allocation of water resources, land planning and regulation, and the high and stable yield of the commodity grain base in Sanjiang Plain.

The Major Ore Clusters of Super-Large Iron Deposits in the World, Present Situation of Iron Resources in China, and Prospect

The metamorphosed sedimentary type of iron deposits（BIF） is the most important type of iron deposits in the world, and super-large iron ore clusters of this type include the Quadrilatero Ferrifero district and Carajas in Brazil, Hamersley in Australia, Kursk in Russia, Central Province of India and Anshan-Benxi in China. Subordinated types of iron deposits are magmatic, volcanic-hosted and sedimentary ones. This paper briefly introduces the geological characteristics of major super-large iron ore clusters in the world. The proven reserves of iron ores in China are relatively abundant, but they are mainly low-grade ores. Moreover, a considerate part of iron ores are difficult to utilize for their difficult ore dressing, deep burial or other reasons. Iron ore deposits are relatively concentrated in 11 metallogenic provinces（belts）, such as the Anshan-Benxi, eastern Hebei, Xichang-Central Yunnan Province and middle-lower reaches of Yangtze River. The main minerogenetic epoches vary widely from the Archean to Quaternary, and are mainly the Late Archean to Middle Proterozoic, Variscan, and Yanshanian periods. The main 7 genetic types of iron deposits in China are metamorphosed sedimentary type（BIF）, magmatic type, volcanic-hosted type, skarn type, hydrothermal type, sedimentary type and weathered leaching type. The iron-rich ores occur predominantly in the skarn and marine volcanic-hosted iron deposits, locally in the metamorphosed sedimentary type（BIF） as hydrothermal reformation products. The theory of minerogenetic series of mineral deposits and minerogenic models has applied in investigation and prospecting of iron ore deposits. A combination of deep analyses of aeromagnetic anomalies and geomagnetic anomalies, with gravity anomalies are an effective method to seeking large and deep-buried iron deposits. China has a relatively great oresearching potential of iron ores, especially for metamorphosed sedimentary, skarn, and marine volcanic-hosted iron deposits. For the lower guarantee degree of iron and steel industry, China should give a trading and open the foreign mining markets.

Oil and Gas Accumulation in the Foreland Basins,Central and Western China

Foreland basin represents one of the most important hydrocarbon habitats in central and western China. To distinguish these foreland basins regionally, and according to the need of petroleum exploration and favorable exploration areas, the foreland basins in central and western China can be divided into three structural types： superimposed, retrogressive and reformative foreland basin （or thrust belt）, each with distinctive petroleum system characteristics in their petroleum system components （such as the source rock, reservoir rock, caprock, time of oil and gas accumulation, the remolding of oil/gas reservoir after accumulation, and the favorable exploration area, etc.）. The superimposed type foreland basins, as exemplified by the Kuqa Depression of the Tarim Basin, characterized by two stages of early and late foreland basin development, typically contain at least two hydrocarbon source beds, one deposited in the early foreland development and another in the later fault-trough lake stage. Hydrocarbon accumulations in this type of foreland basin often occur in multiple stages of the basin development, though most of the highly productive pools were formed during the late stage of hydrocarbon migration and entrapment （Himalayan period）. This is in sharp contrast to the retrogressive foreland basins （only developing foreland basin during the Permian to Triassic） such as the western Sichuan Basin, where prolific hydrocarbon source rocks are associated with sediments deposited during the early stages of the foreland basin development. As a result, hydrocarbon accumulations in retrogressive foreland basins occur mainly in the early stage of basin evolution. The reformative foreland basins （only developing foreland basin during the Himalayan period） such as the northern Qaidam Basin, in contrast, contain organic-rich, lacustrine source rocks deposited only in fault-trough lake basins occurring prior to the reformative foreland development during the late Cenozoic, with hydrocarbon accumulations taking place relatively late （Himalayan period）. Therefore, the ultimate hydrocarbon potentials in the three types of foreland basins are largely determined by the extent of spatial and temporal matching among the thrust belts, hydrocarbon source kitchens, and regional and local caprocks.

Two highly efficient accumulation models of large gas fields in China

Based on reserve abundance,large gas fields in China can be divided into two types：type one of high abundance large gas fields,dominated by structural gas reservoirs; type two of low abundance large gas fields,dominated by stratigraphic and lithologic gas reservoirs.The formation of these two types of large gas fields is related to the highly efficient accumulation of natural gas.The accumulation of high abundance gas fields is dependent on the rapid maturation of the source kitchen and huge residual pressure difference between the gas source kitchen and reservoir,which is the strong driving force for natural gas migration to traps.Whereas the accumulation of low abundance gas fields is more complicated,involving both volume flow charge during the burial stage and diffusion flow charge during the uplift stage,which results in large area accumulation and preservation of natural gas in low porosity and low permeability reservoirs.This conclusion should assist gas exploration in different geological settings.

对潜在信息资源的认识研究

Based on a description of the implication,character and type of information resources,this article analyzes the potential information resourecs which are seldom noticed by people.Emphases are put on their specific properties.The necessity and urgency of developing potential information resources are elaborated.The possibility of developing and utilizing potential information resources are predicted.