Based on bulk analyses of core observation,thin section identification,physical analysis and logging analysis,this paper studied the lithologic features and diagenesis in low permeability reservoir of Sangonghe Formation in block 1 of central Junggar Basin,divided seven lithofacies and seven diagenism facies.Through reasonable combination with lithofacies and diagenism facies,the authors divided twelve sedimentary-diagenetic synthetic facies in the study area.On this basis,using the logging curve characteristics of spontaneous,natural gamma,interval transit time,density,compensated neutron and deep lateral resistivity,the Fisher typical discriminant was adopted to determine the quantitative discrimination functions of each sedimentary-diagenetic synthetic facies Cross-plot of logging parameters was established,and sedimentary-diagenetic synthetic facies of each well were calibrated and the correctness of the identification result was tested.Combined thin section identification with logging identification results,this paper analyzed sedimentary-diagenetic synthetic facies of each well meticulously and predicted the distribution of the reservoir sedimentary-diagenetic synthetic facies in the study area.

Based on the tectonic,sedimentary,geo-chemistry,reservoir,and gas potential studying,we systematically discusses the forming conditions and characteristics of the Lower Cambrian Niutitang Formation shale gas by using outcrop,drilling,and core data.It indicates that deep shelf and half-bathypelagic sedimentary environment controlled the development and distribution of the Niutitang Formations organic-rich black shale.The black shale is characterized by high thickness,fine kerogen type,rich organic matter content and high thermal evolution.The mineral composition of shale is quartz and clay minerals (illite and montmorillonite mixture),with high siliceous and low carbonate composition.It is useful for absorbing gas and fracturing shale reservoir.Through the geological evaluation and resources calculation,the Niutitang Formation in the Huayuan block has favorable geological conditions for shale gas resources enrichment.Therefore,it is considered as a the practical targets of shale gas exploration and production.

In this paper,we consider the Altun strike\|slip fault zone and its surrounding fault zones with uniformed spread direction and similar motion mode to be the Altun strike\|slip fault system.Based on composition of these fault zones,extension scale,active period,activity behavior as well as lithofacies paleogeography of the Meso-Cenzoic sedimentary strata in the area of the Altun strike-slip fault system,seismic data interpretation of the upper sedimentary strata of the basin,and the fission-track dating of the Paleogene System sedimentary rock in the Chaixi depression and remote sensing geology,we discuss the tectonic movements process of The Altun strike\|slip fault.The results suggest that the general tectonic movement pattern of the Altun strike-slip fault system is in the uplift condition under the Indo-China movement action,and there is lack of the Jurassic deposition as denudation phase.With influence of Yanshain movement and week extension tectonics,the Altun strike-slip fault systems accepted the Jurassic deposition in the relative whole settlement,and the big Altun Lake was formed.At the middle and late Yanshan Period,the close of new Tethyan tectonic domain made the regional tectonic uplift,resulting in the big Altun lake disappeared.During the end of the Yanshan Period,the left\|lateral strike slip motion was developed within a regional range,and the Altun strike-slip fault was formed.After the Himalayan period,the southeast  depression and the Qaidam basin came into the relative depression stage.The Paleocene thick sediments reveal that the Altun fault uplift began to raise,and the tectonic process of the Altun strike-slip fault intensified gradually,especially at the later of the Paleogene.With influence of this tectonic event,the Cenozoic Minfeng depression as a strike-slip pull-apart basin was formed by compressive deformation between the Altun strike\|slip fault and the north Minfeng salient,and the Ruoqiang depression as a pull\|apart basin was formed by compressive action among the Cheerchenhe River fault zone,Qiemo-Ruoqiang fault and Altun northern fault.

The frequency of layer supplementing and layer exchanging is used to ensure the stable oil-gas output,since the tension of petroleum production supply during the multi layered reservoir development.This behavior led to the bad effects for later potentiality exploitation of reservoir and scheme adjustment.There are the efficient and effective methods in site practice,such as comprehensively analyzing well logging interpretation data,dynamic production data.They can provide the references for in site worker.Here,we point out the splitting method of oil and gas production in multiple completion wells of multi layered reservoir in combination with comprehensively analyzing well logging interpretation data,dynamic production data.It's helpful to find out residual resources and guide potentiality exploitation measure.

Based on the analysis of core,mud log,Inspection,well logging and other information,the relationship has been established between well logging curve and the sedimentary microfacies by using the self-potential,natural gamma,resistivity and acoustic logging.The type and characteristics of well logging curve shape in different sedimentary microfacies also have been described.Microfacies of the H1 Formation have been researched from three different level of single well,section correlation and planar distribution.The results show that oil-bearing layers of the HSS oilfield are river-delta depositional system,mainly including of delta front and shoreward lake sub-facies.The shapes of well logging curves corresponding to subaquatic distributary channel show as cylinder or bell-shape,corresponding to mouth bar as reversed cedar shape,to front sheet sand mostly as dentate shape,and to shore-shallow lake as dentate or finger-like shape.

Seismic sedimentology is a subject using seismic method to make researches on sedimentary rocks and their formation processes.It is a new marginal intersection subject following the seismic stratigraphy and sequence stratigraphy.Using the technologies of frequency division,phase shift and stratal slicing,this paper studies seismic sedimentology of the organic reef from the Changxing Formation of Sichuan basin.The results show that using the frequency division technology can create fine isochronous stratigraphic framework; phase shift seismic data are similar to wave impedance data and prone to interpretative; the combination of stratal slicing and seismic attributes analysis is more effective than the conventional amplitude slices on capturing the tiny lateral changes and displaying the various depositional characteristics.Examples showed that seismic sedimentology has unique advantages in the analysis of sedimentary facies and the forecast of organic reef.

 

 The gas industry in China shows excellent developing trends: firstly, from count ry poor in natural gas to the one rich in it. In 2005, the gas output has reache d near 500×10⁸ m³; secondly, the theory of natural gas exploration develops  from monism(oil type gas-generating theories) to dualism(oil-type and coal-f ormed gas-generating theories); thirdly, the increasing gas output calls for st rengthening in natural gas exploration and development. During the past more tha n 20 years, the natural gas geological theories have developed much: The coal me asure source rocks mainly generate gas with minor oil; the identification index  with high credibility and accuracy on various natural gases have been set up; th e studies on the controlling factors of great gas field formation, by quantifica tion or semi-quantification; the carbonate with TOC content about or lower than  0.2% can hardly be regarded as sources rocks and the TOC content of effective c arbonate source rocks must reaches or more than 0.5%. Not only the abiogenic gas  exists in the nature, but also can it form gas pools. Several CO₂ gas pools h ave been found in eastern basins of China. And the first abiogenic alcane gas re servoir in the world has been.

The Zhangjiatan shale of the Lower Chang 7 member of Yanchang Formation,Ordos Basin is an important exploration target for shale gas.Since the silty beds/laminae in the shale play an important role in gas storage,fluid flow,fracturing and development of shale gas/oil,it is of great significance to ascertain the thickness and the distribution characteristic of the silty beds/laminae.The measurement results from outcrop,core and thin section show that the silty beds/laminae have larger detrital grains than those in the clayey laminae and the silty laminae thickness mainly ranges from 0.5mm to 8mm.Their total thickness can occupy 7%-26% of the shale formation with an average density of 8-40 layers/m,which shows strong vertical heterogeneity.The thickness distribution of silty beds/laminae presents a fractal distribution on a dm to mm scale and the fractal dimension D has scale invariance over the whole thickness range.According to the data from the relatively thick layers of silty beds,the accumulative number of the thinner silty beds/laminae was estimated using the Number-size model.The accumulative thickness of silty beds/laminae and its ratio to the shale formation thickness were calculated.It has been verified that this method can ascertain the thickness of the silty beds/laminae effectively.

Through detailed studies of marine shale gas in China and investigation of typical shale gas zones in the United States,similarities and differences of geological features of the shale gas in USA and China were summarized.The comparative study is of important theoretical and practical significance for marine shale gas in Sichuan Basin.(1)Barnett,Marcellus and Haynesville shale basins are foreland basin,while Sichuan basin in Paleozoic is intra-craton basin.Their depositional environments are deep water shelf,mainly siliceous and calcareous shale,with high brittleness mineral content.(2)TOC of Barnett shale is 3%-13%，averaged at 4.5%;Marcellus is 3%-12%,averaged at 4.0%;and Haynesville shale is 0.5%-4%.TOC of Wufeng-Longmaxi and Qiongzhusi is 1.5%-3% and 2.5%-4.5%,respectively.(3)Maturity of three major shale formations is moderate,while that of Sichuan Basin is at over-mature stage.The R_O values of the Barnett,Marcellus and Haynesville formations are 0.5%-2.1%，1.2%-3.5%，and 1.2%-3%,respectively.However,the R_Ovalues of the Longmaxi and Qiongzhusi formations are 2.5%-4.5% and 1.5%-3%,respectively.(4)Barnett shale has thickness of 30-180m,porosity of 4%-5%,and permeability less than 1×10^-3μm²;Marcellus shale has thickness of 15-60m,porosity averagely of 10%,and permeability less than 1×10^-3μm²;Haynesville shale has thickness of 70-100m,porosity of 8%-9%,and permeability less than 5×10^-3μm².Longmaxi shale has thickness of 25-120m,porosity of 3%-10%,and permeability of(0.01-1)×10^-3μm²;Qiongzhuxi shale has thickness of 40-100m,porosity of 0.1%-3%,and permeability of(0.01-42)×10^-3μm².(5)Gas contents of Barnett,Marcellus and Haynesville shale are 4.2-9.9,1.70-2.83 and 2.5-9m³/t,respectively,and that of Longmaxi and Qiongzhusi shale are 1.7-4.5 and 0.55-1.2 m³/t,respectively.(6)Except Qiongzhuxi shale,the other four shale formations have good sedimentary cover,which is conducive to gas preservation.(7)American shales have more favorable surface conditions,mostly plains,while mostly hills in Sichuan Basin.(8)Except Haynesville shale,fractures are well developed in other shale formations.(9)Shale gases from both  the USA and China have rich resource potential.The Geological and technically recoverable resources of Longmaxi Formation are 17.5×10¹²m³ and 1.77×10¹²m³,respectively while that of Qiongzhusi Formation are 8.86×10¹²m³ and 0.886×10¹²m³,respectively.

Accurate determination of the oil-charging threshold throat plays an important role in recognizing the oil accumulation process.The oil-charging threshold of throats in tight sandstone in Gongshangmiao Oilfield of Sichuan Basin has been studied by means of theoretical calculation and of the observation using environmental scanning and energy spectrum (ESEM) in this paper.Based on the fluid mechanical equilibrium,the calculated theoretical threshold near the interface between source rocks and reservoirs is 29.06 nm.Because the direct influence of the oil-generation overpressure on the fluid is not as strong as the one near the interface,the threshold in the middle of tight sand reservoirs was measured as 59.66 nm with ESEM instead of mechanical analysis.Connecting the thresholds with the mercury injection capillary pressure test (MICPT) on tight sandstone reservoirs,it is predicted that oil saturation near the interface between source rock and reservoir and the one in the middle of reservoirs are 69.5% and 60.4% respectively,which are in good accordance with the well test.Researches on thresholds in different parts of reservoirs could provide a theoretical basis for the study on tight oil charging mechanism and a practical method for tight oil saturation prediction and play assessment.

一、天然气同位素组成所谓同位素系指质子(Z)数相等的同一元素中中子(N)数不同的各种原子,即原子序数相同而中子数不同的各种原子。同一元素的诸同位素,它们彼此化学性质几乎相同,在周期表中占同一位置。同位素的表示是在该元素符号的左上角(或在右上角)注明中子数,需要时同时在左下角(或右下角)注明原子序数。

The thickness and distribution of organic-rich shale are important parts of forming conditions appraising about shale gas and shale oil.The distribution of shale is controlled by sedimentary environments.This study determined the sedimentary environment of dark shale of the Chang 7 Member by field profile and cores.Vertical overlaying features of dark shale were confirmed by field profile and wells.Sedimentary structures and micro-bedding structures were delineated by cores and sections.Differences of total organic content and organic types between dark shale in different sedimentary environments were revealed by testing data and logging interpretation.Dark shale of the Chang 7 member distributes in the subaqueous distributary bay of delta front and semi-deep to deep lacustrine.In semi-deep to deep lacustrine,dark shale has great continuous thickness and sandstones have thin thickness.However,in delta front,dark shale has thin continuous thickness,shale and sandstone interbeddings have similar thickness or thin shale layer and thick sandstone layer.In semi-deep to deep lacustrine,dark shale always has lamellation,horizontal lamination and sandy lamination,whereas lamellation does not develop very well in delta front shales.Organic types of delta front are mainly type Ⅱ₂ and Ⅲ,and type I and type Ⅱ₁ to semi-deep to deep lacustrine shales,respectively.TOCof semi-deep to deep lacustrine shale are higher than that of delta front shale.Based on these comparisons,we concluded that shales which distribute in semi-deep to deep lacustrine are the more favorable prospecting target for shale gas/oil in the Yanchang Formation.

Deep oil and gas exploration and exploitation have made a series of significant breakthroughs in recent years.However，the progress，challenges and development trend of exploration and development of onshore deep oil and gas resources in China have not been systematically analyzed.This article summarized five fundamental characters of deep petroleum resources：(1)More gas and less oil，with complicated phase state；(2)Universally high temperature and high pressure，but great differences existing in different basins or strata；(3)Multi hydrocarbon accommodation，multi hydrocarbon sources；(4)Relatively dense reservoir，but having large scale efficient reservoirs；(5)Complicated accumulation and multi period reconstructions.Based on the exploration and development history of deep oil and gas，it is regarded that the exploration and development of deep petroleum in China is at the “large-scale discovery stage”，and great achievements have been obtained in the carbonate/clastic/volcanic reservoirs，but four challenges still exist：(1)complex hydrocarbon generation，reservoir evolution and accumulation restrict the exploration orientation and targets；(2)the long period and high cost of well drilling restrict the petroleum discovery and efficient development；(3)immature high temperature & high pressure slim hole logging technology restricts accurate identification of hydrocarbon reservoir;(4)unadapted petroleum recovery technique and equipment restrict effective development and large scale utilization.On the basis of comprehensive analysis，it is concluded that deep petroleum resources mainly exist in three areas of six basins in onshore China，with great exploration potential，which is strategic replacement.It is suggested that petroleum companies，universities research institute should be gathered to overcome problems in limited time，integrate innovative achievements，and develop deep oil & gas exploration and development theories and technical system to support deep oil & gas rapid development.

We studied the lithology,pore characteristics,physical properties,diagenesis,diagenetic stage division and diagenetic evolution history of the volcanic rock reservoir in northwestern Junggar basin by extensive drilling core observation,combining with laboratory analysis (including ordinary thin sections,cast thin sections,scanning electron microscopy,X-ray diffraction and so on).The basic volcanic rocks and acidic volcanics dominated in volcanic rocks.The diverse reservoir interspace included six kinds of primary pore,three kinds of primary fracture，seven kinds of secondary pore and three kinds of secondary fracture，and the pores with poor physical properties were charactered with poor sorting and narrow pore throat radius.The volcanic reservoir had experienced three stages of syndiagenetic stage，epidiagenetic stage and buried diagenetic stage,and a variety of diagenesis including the early diagenesis of welding and condensing contraction,and the late diagenesis of tectonic,weathering and leaching,dissolution,zeolitization，chloritization.Different types of reservoir space were formed in different diagenetic evolution stages.There formed the primary pores and condensation contraction fractures in syndiagenetic stage,some filled secondary pores and weathering sutures in epidiagenetic stage,secondary pores,structural fractures and dissolved fractures in the burial diagenetic stage.

The lithology characteristics,reservoir property and pore structure,diagenesis,diagenetic minerals,diagenetic environment,diagenetic stage and diagenetic evolution sequence of Bashijiqike Formation tight sandstone reservoirs are studied by making full use of normal thin sections,casting thin sections,cathode luminescence,scanning electron microscope analysis data and mercury injection test data.The results show the reservoirs have experienced diagenesis such as compaction,cementation,corrosion and fracturing.It is now in the phase A of middle diagenetic stage.Then five types of diagenetic facies are divided based on type and intensity of diagenesis,diagenetic minerals and their effect on the reservoir quality.They are: tight compaction facies;,carbonate cemented facies,mixed-layer illite-smectite filling facies,diagenetic micro-fracture facies and corrosion of unstable components facies.According to the various well logging response characteristics of different types of diagenetic facies,five normal logging curves which are sensitive to the diagenetic facies are chosen to characterize the diagenetic facies.They are: neutron logging (CNL),density logging (DEN),acoustic slowness (AC),natural gamma ray (GR),array induction log (M2R2).Thus we can set up the logging recognition model and standard of diagenetic facies.Actual log data of wells in Keshen area were processed using this method,and the diagenetic facies of Bashijiqike Formation reservoir in this well is figured out on the vertical profile.When the logging recognition results of diagenetic facies of Bashijiqike Formation are corresponded with the actual gas test data,it is found that the diagenetic micro-fracture facies are always coexisting with tectonic fractures.When there are no tectonic fractures,the gas bearing property of the layer with the corrosion of unstable component facies is the best,while the diagenetic facies such as tight compaction facies,carbonate cemented facies and mixed-layer illite-smectite filling facies correspond to the dry layers.It is an effective way to comprehensively evaluate the reservoir and predict the sweet spot of tight gas sandstones by analyzing the diagenetic facies.

Well Gucheng 6,which lies in the Gucheng region,obtained industrial gas flow at Lower Ordovician dolostones in 2012,and represented a kind of unconventional reservoir-cap combination and gas accumulation type with great importance on gas exploration.Since reservoirs are mainly controlled by pene-contemptuous dolomitization and hydrothermal alternations,and gases accumulate along slide faults,the reservoir-cap rock combination characteristics and hydrocarbon accumulations in Gucheng 6 were studied.Based on the research of reservoir formation and gas accumulation in well Gucheng 6,double cap rocks and slide faults controlling reservoir and reserves model is suggested,i.e.,hydrothermal fluids upwells along slide faults,then transports horizontally beneath cap rocks completing reservoir constructive reformation at early stage,gas inputs along slide faults and accumulates under cap rocks in gas discharging process.According to the distribution study on the Upper Ordovician mudstone,the Middle Ordovician compact limestones and the slide faults,it is redeemed that Manxi-Gucheng area is advantaged distribution district of combined cap rocks and slide faults,and that northern Manxi Uplift and southern Gucheng Uplift are the most practical area for the Lower Ordovician dolostones explorations.

Integrative and multidisciplinary analyses of the development and evolvement and the geologic functions of Pearl River Mouth Basin reveal that it is filled with two types of source rocks that are Eocene Wenchang Formation middle-deep lacustrine facies and Lower Oligocene fluviolacustrine paludal facies. It had Upper Oligocene Zhuhai Formation facies and Middle Upper Miocene sandstone reservoirs and the associated caprocks at the stage of faulting-depression. A lot of NWW faults caused by intense tectonic and faulting activities not only controlled the tectonic framework of the basin but also supplied tunnels for the deep oil and gas migration and accumulation. It has reservoirs characterized by lower oil generation and upper oil accumulation as well as continent oil generation and marine accumulation.

A set of typical sedimentation of sublacustrine fans in lower Cretaceous in Wuliyasitai sag of Erlian basin is composed of feeder channel, inner fan, middle fan, and outer fan. The main micro-facies include feeder channel and main channel in inner fan, furrow dam and braided channel in middle fan, inter-channel and sheet turbidite sand in outer fan. Although a single sub-lacustrine fan is not large in scale, the sedimentation is characterized as multi-stage development, group distribution, vertical superposition, and superimposed horizontal lace. Thus, the depositional scale is large. The big open ended space and continuous supply of deposits are two key factors for f-ming the thick sub-lacustrine fan. Meanwhile, the place of downthrown block of growth fault or the slope-break zones is the favorable area for the sub-lacustrine fan development. The conglomerate body in sub-lacustrine fan is close to hydrocarbon-generated sag and prone to lithologic trap formation and hydrocarbon accumulation; thus it is important for oil and gas exploration.

Basins in Northern South China Sea belong to passive margin basins, and they are located at the junction of the Eurasian, the Pacific and the Indian-Australian plates, and also at the Superposed areas of Palaeo-Tethyan structural regimes and Palaeo-Pacific structural regimes. So the geological settings of these basins are complex, their Tertiary sediments developed well, and the phenomena of petroleum geology are rich and colorful. Based on the characteristics of framework and tectonics, the basins in Northern South China Sea can be classified into two types, strike-slip basins and rift basins. The source rocks of the former are mainly the well-developed, huge thickness of Neogene marine depression sedimentary rocks and Miocene marine sedimentary rocks; those of the latter are significantly the rift sediments of Paleogene continental facies, and large-scale source rocks of medium-deep lacustrine facies and inshore paludal facies with coal measure strata well-developed.

By statistic of distribution of basins and typical deep oil and gas fields in the world, the deep gas and oil are distributed mainly in the foreland basins, passive continent margins, and rift basins and intermountain.Source rocks mainly consist of Paleozoic and Mesozoic shale or mudstone.Low geothermal gradient and abnormal high pressure are favorable for the deep oil and gas formation.Lithology of deep oil and gas reservoirs are mainly clastic rocks and carbonate rocks in Paleozoic and Mesozoic.The formation and preservation of high quality reservoir is constrained by favorable facies zones, low geothermal gradients, diagenetic process (i.e.including cement dissolution and dolomitization process), abnormal high pressure, early entrapment of hydrocarbons and fracture development, etc.The deep oil and gas accumulation is controlled by geological background of foreland basins or passive continental margin basins, good assemblage of reservoir and cap, and abnormally high pressure.These factors are important to the deep oil and gas exploration.

According to the ideas of exploration and the reservoir accumulation characteristics of shale gas，we have collected shale gas data in Ziliujing Formation from a batch of exploratory wells in Yuanba area of Sichuan basin. And industrial gas flow has been discovered in three wells of the exploratory wells. Research shows that Ziliujing Formation in Yuanba area is formed in shallow lake-semi-deep lake environment. Thick dark shale，high content of organic carbon and moderate thermal maturity of organic matter which is at the peak of gas production are developed in Ziliujing Formation. Moreover，quartz content is generally more than 60% in the mineral composition of shale, while clay content is below 30%. Gas content is high in shale of Ziliujing Formation, which is the basic condition for the formation and exploration of shale gas. And Ziliujing Formation is the favorable strata for the shale gas exploration.

World offshore petroleum resource is abundant.With rapid economic development and onshore exploration becoming mature,the exploration and development for offshore petroleum resource has gradually become a hot spot.Two databases of IHS and USGS (United States Geology Survey) suggested that the recoverable oil and gas reserve would be 1 321.5 billion barrels oil equivalent,about 35.8% of world total petroleum reserve.They are distributed in 12 regions around offshore.The undiscovered oil and gas resources in offshore are not uniformly distributed in the world.By statistics of undiscovered petroleum resources and exploration layers in the main global offshore basins,the first and second class potential exploration areas are 16 basins,10 of which was in the moderate exploration degree for undiscovered oil and gas resources,accounting for 42% of total resource.So it is good target for petroleum exploration.

Kozeny-Carman(KC)equation is a semi-empirical equation,which is widely used to predict permeability of porous media in the field of flow.Since the establishment of this equation,many new methods were adopted to increase its accuracy.In this paper,an analytical expression for the permeability in porous media using the fractal theory and capillary model was derived based on Posenille law and Darcy equation,which reflects the permeability,porosity,specific surface area relation.The new proposed model is expressed as a function of three properties of porous media considering the specific surface area from the classical KC equation.Meanwhile the fractalKC constant with no empirical constant is obtained.The result shows that permeability of porous media is the function of fractal dimension of pore structure,tortuosity,macroscopic petrophysical parameters(porosity and specific surface area).The KC constant is not constant and has close relationship with tortuosity,fractal dimension and microscopic pore structure parameters.It is concluded that the permeability calculated by using new fractal model is more accurate than that by other KC equations.


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FMI (Formation Micro-Scanner Image) is widely used to analyze reservoir properties with the advantages of high resolution,visible and quantified.In this study,11 FMI facies are classified based on the combination of borehole images,cores,thin sections and open-hole logs.It includes reservoir types like carves and tectonic fractures,sedimentary interlayer types like high resistivity facies and two compound facies of fractures and holes.Besides description of karst systems in borehole images,anomalies in GR curve attracting the researchers are analyzed by FMI images.It shows that compound facies of fractures and holes could be effective reservoir instead of caves with high GR value because oil/gas-bearing holes are connected by fractures.Two suites of karst system were formed in the OY1 while small scale caves and holes were formed in the OY2 because of lithological and structure locations.The results of this study demonstrated that,uncomformity and tectonic geomorphology control the differences of the paleokarst system.

Deep\|water basin of northern South China Sea is under complex geodynamic setting of quasi\|passive continental margin in Cenozoic,with a passive continental margin extensional tectonic rifting of basic properties and oil and gas geological features.Geological conditions for oil and gas migration and accumulation in the deep-water basin of quasi\|passive continental margin in northern South China Sea is similar with some typical deep-water oil and gas-enriched area in global passive continental margin,but there is also some difference and particularity.In this paper,we discuss the special geological background for oil and gas in deep-water basin of the northern South China Sea,accumulation and migration of oil and gas,and geological and geophysical exploration,in comparison with regional geological setting and structural properties,geological condition,and oil and accumulation in dee-|water basin of typical passive continental margin in the world.We also received some important suggestion and reference about oil and gas exploration in deep-water basin.

DN gas fields are located in the Dongqiulitage structure belt in Kuqa depression. Currently, three gas reservoirs, DN1, DN2 and DN3, have been discovered with 3P reserves of more than 2 000×10⁸m ³ in the reservoirs. More gas are expected to be discovered. With the successful application of varying velocity mapping technology, we have estimated the DN2 gas field and discovered the DN3 gas reservoir. Interval velocity is the key factor in discovering traps. This paper discusses the method about varying velocity mapping used in estimating the DN2 gas field and discovering the DN3 gas reservoir. The good method to discover or estimate traps is that the prestack depth migration technology is used in 3D work area and the interval velocity filling is used in 2D work area.

The estimation of fault sealing is a crucial issue in studying petroleum migration and accumulation in sedimentary basins. In 1966 Smith has proposed the theoretical model of Fault Sealing, since then, many scholars have done a lot of work in estimating and predicting the fault seal in clastic strata, and have made great progress of the study during last 10 years.The paper analyses deeply on the lateral fault seal by clay smear on the basis of the precensors studies. Using the Shale Gouge Ratio by Yielding .

Despite of the wide attention that the exploration and development of unconventional hydrocarbons has attracted, neither a distinct and consistent definition nor a systematic classification of the unconventional hydrocarbons can be found in the literature. Based on a comprehensive investigation and analysis, this paper defines the unconventional hydrocarbons as such a kind of hydrocarbon resources that is distinguished from conventional hydrocarbons by reservoir features and accumulation mechanism, and cannot produce economically with traditional measures of exploitation. Comparison between unconventional hydrocarbons and continuous accumulation shows that the former is broader than the latter in connotation, notwithstanding the continuous accumulation is a dominant part of the unconventional resources. Unconventional hydrocarbons can be divided into (1) gaseous, liquid, and solid types according to the state of hydrocarbon phases; (2) tight reservoired oil/gas, shale oil-gas, and coalbed methane in terms of the reservoir types; (3) continuous, quasi-continuous, and discontinuous types based on the characteristics of petroleum distribution or trapping; (4) self-sourced and outer-sourced types according to the source\|reservoir relationship; and (5) the primary and secondary types in terms of the genesis of accumulation. Investigation of resource assessment in China indicates that the original in\|place resource of unconventional oil is roughly 720×10⁸t, and recoverable resource is about 210×10⁸t(excluding tight oil and shale oil); the original in-place resource of unconventional gas is some 320×10¹²m³, of which the sum of tight gas, coalbed methane, and shale gas resources is possibly 175×10¹²m³, and their recoverable resource is about 70×10¹²m³, approximately 3 to 4 times that of conventional gas. Based on the analyses of the condition and characteristics of hydrocarbon accumulation, we suggest a new resource triangle concept that petroleum resources are divided into three grades, namely the discontinuous (conventional), quasi\|continuous (tight), and continuous (self-sourced unconventional) accumulations, respectively. From this concept, we forecast that in petroleum basins where tight reservoirs are developed the amount of petroleum resources from the tight reservoirs is presumably in between that of the conventional accumulation and that of continuous unconventional accumulation from the source rocks. Because tight hydrocarbons are of better quality of reservoirs than coalbed methane and shale gas and are predicted to be of greater resource potential than assumed previously, they should be given top priority in the exploration of unconventional resources in China.
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The exploration of shale gas was firstly put into practice in USA. Shale gas is a kind of unconventional natural gas, which mainly accumulates in adsorbed and free phases. Shale gas is characterized by insitu accumulation, and controlled by the thickness and distribution, organic geochemical characteristics, porosity and permeability, fracture development and seal conditions of the shale. The shale of Yanchang Formation is widely distributed in Ordos Basin, and is characterized by big thickness, high TOC, moderate thermal evolution, popping gas survey, and well developed fractures. The preliminary research shows that the south Ordos Basin is the favorable area of the shale gas development of Triassic Yanchang Formation, and the “L-type” area of Dingbian\|Huachi\|Fuxian is the most favorable area for the shale gas development. The shale gas potential decreases gradually outwards to the surrounding area.

Computer simulations of a single or set of fractures were conducted previously, and the effects of cavities on fracture width variation were hardly concerned. In this paper, we established a finite element model of fracture width variation for different fracture\|cavity groups according to the finite element method of fracture mechanics and computer simulation, and discussed 3 types of fracture-cavity groups models related with fractured/caved carbonate reservoirs in Tahe oilfield.The relationships among the fracture width, length, positive differential pressure and cavity development were probed. The simulation results showed that, the fracture width increment increased with the increasing of the positive differential pressure; under the same positive differential pressure, the fracture width increment increased with the growing of fracture length; and the occurrence of cavities intensified the fracture width variation.  The richer the cavities porosity was, the bigger the fracture width increment was; the growing of fracture width increment was coming with the increasing of cavity radius. The computer simulation of fracture width variation can provide a theoretical basis for choosing suitable lost circulation materials and improving lost control technologies.

At present, Sichuan basin is a petroliferous basin which has the biggest number of H₂S-bearing gas reservoirs and of which the H₂S-bearing gas reserves is also the biggest in China. Reservoirs producingH₂S-bearing natural gas are distributed in Sinian, Carboniferous, Permian, and Triassic. Transversely, the East Gas District(EGD) has the highest content of H₂S, followed by the West Gas District(WGD) and the Middle Oil-Gas District(MOGD), and the South Gas District(SGD) has the least. Vertically, the content of H₂S is various among the different reservoirs and even in different members of the same strata or well. TheH₂Scontent of natural gas in Triassic Feixianguan Formation is the highest, followed by those in the Permian Changxing Formation and in the Triassic Leikoupo Formation, and that in the Permian Maokou Formation is the least. The differences of the H₂S content among different wells in the Sinian Dengying Formation are slight, and the similar phenomenon also exists in Carboniferous Huanglong Formation. SignificantH₂S content differences have been observed in the natural gas from different members of Jialingjiang Formation, in which the gas from the fifth and the forth members have the highest H₂S content. According to the comprehensive analysis of the sedimentary facies, burial history, thermal history, homogenization temperature of the fluid inclusions, as well as the sulfur isotope ratios and the components of the natural gas, it can be concluded that theH₂S of the Feixianguan Formation and the Changxing Formation in EGD, the Jialingjiang Formation(except the first member) in EGD and SGD, the Dengying Formation gas pool of Weiyuan gas reservoir in SGD, the Leikoupo Formation gas pool of Zhongba gas reservoir in WGD and the Leikoupo Formation gas pool of the Moxi gas reservoir in MOGD were generated by the thermochemical sulfate reduction(TSR), while that in the Huanglong Formation in EGD and the Maokou Formation in SGD were generated by the cracking of the organic matter(kerogen or oil ) which contains sulfur.

The high-resolution sequence stratigraphy represented By T. A. Cross in Clorado School of Mines is a new principle that basing on the data of drilling, outcrop, logging and high resolution seismal section, using fine techniques of sequence partition and comparison to change one-dimension drilling information into three-dimension stratigraphy relationship, it can set up genetic stratugraphy comparison construction, and evaluate and forecast the distribution of reservoirs, cap formation and oil source bed.

一、伸展盆地的一般概念伸展盆地是在引张作用下与地壳和岩石圈产生伸展、减薄作用有关的一类裂陷盆地。裂谷是最常见的一种伸展盆地,是“由于整个岩石圈遭受伸展破裂而引起的,并且常常是一侧为正断层限制的断陷盆地”。

This paper presents the application of 3D visualization technology to the Gangzhong area in Huanghua depression, including seismic horizon calibration, trace strata, structural interpretation, fault interpretation etc. The preliminary approach to the fault structures allows the problems about such a systematic interpretation and description of fault structures in studied area to be well solved, which are difficult to be done by the conventional seismic interpretation methods.

Upper Paleozoic structure in the east part of Ordos basin as a large smooth westward monocline was characterized by simple structure short of folds and faults.Accumulation and distribution of natural gas in the upper Paleozoic in Yulin area was mainly controlled by sedimentary facies,and the types of gas reservoir were regarded as lithologic type.Nevertheless,the structural evolution suggested that the Yulin region has experienced 3 structural stages,i.e.level structure in middle Triassic,paleo\|uplift in late Triassic to early Cretaceous,and monoclinal slope in late Cretaceous to present.The paleo-uplift of upper Paleozoic was probably formed through the Indosinian movement in late Triassic,intensified by the early Yanshanian movement in the end of early Cretaceous and reformed by the Himalayan movement in the Cenozoic.The formation and development of this paleo-uplift coincided with time of peak generation and expulsion of hydrocarbons from Carboniferous and Permian source rocks.Thus,the paleo\|uplift became the most favorable area for natural gas accumulation.The giant gas fields of Yulin and Daniudi were distributed at paleo\|uplift and its surroundings,inferring that the formation and occurrence of giant gas fields would be controlled by the paleo\|uplift.But the present local structures have little or even no effect on the distribution of the giant fields.On the contrary,we found out that the Upper Paleozoic natural gas fields in the Ordos Basin would be continuous tight gas accumulations,which are characterized by widespread hydrocarbon generation,vaporizing\|like expulsion,short-distance migration and pervasive distribution.Recognition of continuous tight gas accumulation in the Ordos basin may give a greater resource volume and a bigger exploration potential in this basin.

It is rapid development of CBM in China,in contrast shale gas is starting.It is important to elucidate the common and difference between CBM and shale gas,because of similar aspects of gas sources,migration,preservation and accumulation between them.There is mixing of CBM and shale gas in some basins.The accumulation of both gases is constrained by reservoir thickness,thermal maturity,organic matter content,and reservoir pore and microfracture.The CBM is also affected by structure and hydrogeology.By contrast of depositional conditions,the coal was mainly formed in the seashore,delta plain,alluvial plain and front of alluvial fan,while the shale was quickly deposited in the reductive environment.

The pore structure of shales plays an important role in the evaluation of hydrocarbon content,gas exploration and development.However,there is little study on the pore structure of shales at home.High-pressure mercury injection and nitrogen adsorption experiments are employed to study the pore structure of shales and the pore structure parameters are also obtained.The effect of pore structure on gas adsorption and movement is analyzed.The results show that micropores and transitional pores are the main pore in shales,which provide the vast majority of pore volume.Micropore in the organic matter is the primary contributor to specific surface area and functions as the main adsorption space.The pore types are complicated and the pore morphology is diverse.There are airtight pores with a close end,air pores,and ink-bottle pores in shales and the pore connectivity is poor.The high content of micropore and transitional pore is beneficial for gas adsorption in shales,but the mesopore and macropore are backward,which goes against for shale gas seepage and production.

Based on the investigation of shale gas at home and abroad,this article systematically studies the basic characteristics of shale gas reservoir,analyzes formation mechanism of shale gas reservoir and its controlling factors.In addition,it discusses the matching identification method and resource assessment methods aiming at the shale gas reservoir′s special accumulation characteristics.Studies show that shale gas reservoir generally has characteristics such as self-generation and self-storage,fine particle size,low porosity and low permeability,fracture development,big reservoir area,continuous distribution,wide formation temperature and burial depth,abnormal formation pressure,low capacity,low recovery ratio,long production period and its occurrence mode is mainly adsorption state.Shale gas reservoir formation has transitional characteristic,with reservoir formation mechanism of both source-contacting gas and conventional natural gas.The type,content and maturity of organic matters,the fracture,porosity and permeability,mineral composition,thickness,humidity,burial depth of shale,as well as the temperature and pressure have certain controlling effect on the formation of shale gas reservoir.Shale gas can be identified qualitatively or quantitatively with core analysis method,geophysical method and new logging techniques such as ECS logging and imaging logging.According to the difference of principles,there are mainly four shale gas resource assessment methods for different geological and data conditions,which are analogy method,statistic method,genetic method,comprehensive analytical method. 〖WT5HZ〗Key words〖WT〗:

Hydrocarbon source rocks in Lianyuan depression include carbonate rock, mudstone and coal. The authors studied geochemical characteristics and maturation of organic matters in the Devonian\|Permian source rocks from Lianyuan depression based on the geochemical data of residual organic carbon content, chloroform bitumen A, vitrinite reflectance and fluid inclusions of specimens. Results suggest the source rocks of Lianyuan depression mature and generating mainly gas. The authors estimated the hydrocarbon generation intensity of the source rocks due to the high thermal evolution and little residual organic matter abundance. After analyzing the geochemical characteristics, the hydrocarbon generation intensity and the matching relationship between tectonic movement and hydrocarbon generation of the source rocks, the authors believe that the Devonian\|Permian source rocks of Lianyuan depression are of middle hydrocarbon generation potential. And the source rocks of the Permian Longtan Coal Formation have the potential to secondary hydrocarbon generation.

By means of interpreting Carboniferous oil and gas formation and reservoir in the Hongche fault belt,Carboniferous reservoir formation in the Hongche fault belt was constrained by fault belt,volcanic lithofacies and unconformity surface.After we elucidated three factors above，four patterns of reservoir formation were proposed as follows: assemblages of eruptive oil reservoir and volcanogenic seal,eruptive oil reservoir and overflowing seal,eruptive and overflowing transitional oil reservoir and volcanogenic seal,and overflowing oil reservoir and volcanogenic seal.