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Table of Content

    25 September 2002, Volume 23 Issue 3
    MODELING MODEL FOR HYDROCARBON EXPULSION IN CARBONATE SOURCE ROCKS AND ITS APLICATION IN PRACTICE: EXAMPLE FROM THE MAJIAGOU FORMATION OF ORDOVICIAN IN ORDOS BASIN
    Chen Yicai, Shen Zhongmin, Huang Zeguang, Li Yanjun, Guo Xiuying, L? Qiang, Zhang Jun, Shi Xiaoying
    2002, 23(3):  203-206.  doi:10.11743/ogg20020301
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    With well development of cementation, carbonate hydrocarbon source rocks would be consolidated into rocks quite earlier, therefore, compaction effect is not merely chief one instead of multi-effects existence in hydrocarbon expulsion. Different evolution stages with various ways of hydrocarbon expulsion, in the higher-over maturation stage, micro-fissure hydrocarbon expulsion and molecular diffusion are believed to play a chief role. A mathematical model of diffusively hydrocarbon expulsion and micro-fissure hydrocarbon expulsion can be established quantitatively in line with the principle of mass conservation of hydrocarbon generation and expulsion on the basis of one dimensional geological model. Modeling results from this model indicate that Majiagou Formation in the Ordovician in Ordos basin had entered hydrocarbon generation threshold by the end of the earlier Permian and reached the peak of hydrocarbon generation in the Triassic, and began getting into the over saturation-dry stage in the earlier Cretaceous; Accumulative total hydrocarbon expulsion rate is 60%-80%, of which compactively hydrocarbon expulsion, diffusively hydrocarbon expulsion and micro fissure hydrocarbon expulsion are predominant whereas water soluble facies hydrocarbon expulsion occupies a small proportion.

    APPLICATION OF FLUID INCLUSION IN PALAEOPRESSURE MODELLING RESEARCH
    Chen Honghan, Dong Weiliang, Zhang Shulin, Yang Jihai
    2002, 23(3):  207-211.  doi:10.11743/ogg20020302
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    The minimum trapping pressure ratio of hydrocarbon fluid inclusions can be defined by their isochore single value variations in P-T space projection and physical property of their isochore. Calcite veins, quartz secondary enlarged margins and fluid inclusions in particle cracks in sandstones of Yancheng Formation of YC21-1 structure in Qiongdongnan(southeastern Hainan) basin of the South China Sea indicate in geologic history that four phases of fluid inclusions were developed in that region; the capping bed was once burst during the third mobile phase of thermo-fluid inclusions which would be healed soon after. Therefore, no many free-state natural gas reservoirs could be formed there.

    ORIGIN OF LOWER PALEOZOIC DISSOLVED GASES IN CENTRAL GAS FIELD OF ORDOS
    Li Xianqing, Hou Dujie, Hu Guoyi, Zhang Aiyun, Liu Changqing
    2002, 23(3):  212-217.  doi:10.11743/ogg20020303
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    Characterized by higher contents of methane, the lower Paleozoic dissolved gases in central gas field in Erdos have a little amount of heavy hydrocarbon and non- hydrocarbon compositions basically indicating a dry gas feature of high-over maturation(C1/C1-5>0.95). Differences between "East block & West block" in compositions of the lower Paleozoic dissolved gases(high contents of heavy hydrocarbon C2+,benzene,toluene in compositions of dissolved gas in the east block while in the west block above compositions are either very low or absent) reveal that east and west block dissolved gases come from different sources. Dissolved gases from the east block are combinations of coal-formed gas in the upper Paleozoic and oil-type gas in the lower Paleozoic, whereas dissolved gases from the west block mainly come from oil-type gas in the lower Paleozoic.

    STUDY ON SEDIMENTARY SIMULATION OF FAN DELTA IN LOWERSUB-MEMBER ES3 OF BAIMIAO GAS FIELD IN PUYANG DEPRESSION
    Xia Changhuai, Zhang Chunsheng, Zhou Haibin, Shi Bingquan, Liu Zhongbao, Li Li
    2002, 23(3):  218-223.  doi:10.11743/ogg20020304
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    Simulation of genetic process of sand body in sub-member Es3 which is designed on the basis of sedimentation characteristics of the sandbody in Baimiao region indicates that the development of delta in sub-member E s3 fan is the result and caused chiefly by the intersected process of clastic current and traction current. The clastic current played a main rule in the flooding period while the traction current played a chief rule in the period of normal water level year; Two types of combinations(stack and spread)exist in the fan delta, the former with small size but in great thickness, and the later in small thickness but with big size. The development and evolution of sub-member E s3 fan delta is largely effected by several factors of upper reaches current intensity, migration of muddy sand, braiding and migration of water current, uplift and subsidence of lake water level as well as subsidence rate of the mobile bottom bed etc.. It is believed by simulating that the width of three braided channels between Bai No.5,and No.3 and No.28, and No.7 well which mainly developed in the process of the development of the delta in sub-member Es3 fan are 750m at maximum and 300m at minimum; In Duzai fault where purified sandstones are found in the braided channels with great thickness and good physical property, between Lanqing fault and Duzai fault sandstones are with great thickness and widely spread while sandstones near Lanqing fault become thinner and thinner and with poor property.

    THE SIGNIFICANCE OF THE ANALYSIS OF TARIM PALEOZOIC PROTOTYPE BASINS IN OIL AND GAS EXPLORATION
    Xu Xuhui
    2002, 23(3):  224-228.  doi:10.11743/ogg20020305
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    Five types of prototype basins in two categories of discrete and convergent can be divided according to the changes of Paleozoic structure and thermo-system. Tazhong and Tabei uplifts were developed respectively (or against the background) due to the emergence of fissured-subsidence troughs in the early Sinian; with the development of marginal sags from the late Sinian to the early Ordovician and with the subduction,closure and collision of the oceanic basins from the middle-late Ordovician to the Devonian Period. The whole Carboniferous-Permian period was under the environment of extension. Different prototype basins have different significances for oil and gas exploration. Located in the passive continental margin, Manjiaer sag has greater subsidence and sedimentary rate and has well- developed oil and gas-producing source rocks. The ancient uplift represented by Tazhong and Tabei is a main guiding area of Hercynian oil and gas accumulation and has good conditions for oil and gas reserving and capping and is a very important area for oil and gas accumulation.

    STRATIGRAPHIC SEQUENCES IN THE MIDDLE YANGTZE & ADJACENT REGION AND EVOLUTION OF PROTOTYPE BASINS
    Dai Shaowu
    2002, 23(3):  229-235.  doi:10.11743/ogg20020306
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    Prototype basins in the middle Yangtze and its adjacent region can be divided into nine mega- sequences. Sequence I-VI are composed of Mesozoic-Palaeozoic marine beds; Sequence VⅡ is made up of the early-middle Jurassic terrestrial deposits; Sequence VⅢ consists of Jurassic foredeep deposits; Sequence IX is characterized by the late Cretaceous and Tertiary rift basin deposits. During the Sinian Period, the central region was in the environment of platform facies while the south region was in the environment of shallow marine shelf and the north region was mainly in the environment of epicontinent sea. The Cambrian to the early Ordovician is characterized by typical continent marginal basins. Rift basins were well developed during the middle-late Ordovician-Silurian; Extensive transgression events occurred during the Devonian and Carboniferous which connected with several places of the South China Sea waters and the Pacific Ocean sea waters; From the Permian to the middle Triassic, the prototype basins were in the stage of transformation with Mianlue palaeo-oceanic basin(which separated Qinling micro-plates from the Yangtze plate)opening towards east and the former regional uplift in the northern margin of the Yangtze was transformed into the continent marginal basins of deepening northward. During the late Triassic, two episodic depositional cycles occurred in the region where Badong Formation is characterized by slow subsidence deposits and Jiuligang Formation by rapid subsidence deposits. The prototype basins experienced slow deposition in the early Jurassic and rapid deposition dominated by underwater sedimentation in the middle Jurassic. Two tectonic evolution stages can be classified in the late Jurassic, tectonic activities in the early stage was relatively quiet and in the late stage was quite strong. During the late Cretaceous-early Tertiary, the basins became smaller in size dominated by lacustrine and fluvial deposits. Therefore,the middle Yangtze and its adjacent region have experienced in geological history four types of prototype basins with the characteristics of episodic sedimentation.

    THE DEVELOPMENT FEATURE AND HYDROCARBON EXPLORATION POTENTIAL IN MUGLUD BASIN
    Zhang Yamin, Chen Fajing
    2002, 23(3):  236-240.  doi:10.11743/ogg20020307
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    The development and evolution of Muglud basin can be divided into three stages: (1)in the early Cretaceous, with the Africa-South America continent splitting, the first extension downchasm basin ocured; (2)in the late Cretaceous, with the original Atlantic Ocean formation, the second extension downchasm basin occurred; (3)in Kainozoic, with the regional subsidence, this basin evoluted into a sag basin. From the end of the late cretaceous, there were apparent movements, resulting in reverse structure. In the west-north basin, there were strik-slip movements along the great central African fracture. As a result, Tullus, Bagarra sub-basins were greatly reformed. The main structural styles of Muglud basin are half graben, half horst(or horst), extension fault-block, rollover anticline, compression anticline and flower structure. Among them, rollover anticline, compression anticline and horst are the main area of hydrocarbon enrichment. In the early Cretaceous, the basin was filled with mudstone of half-abyss and abyss facies, which controlled the distribution of hydrocarbon rocks. As the sediment center continuously moved southwards, good thick upper Cretaceous mudstone deposited in the south area, and formed regional cap-rock of giant oil field.Therefore,good potential region for oil and gas exploration in Muglud basin is decided by the above factors.

    RELATIONS BETWEEN JURASSIC INCLUSIONS AND OIL & GAS MIGRATION & ACCUMULATION IN YANQI BASIN
    Chen Wenxue, Li Yonglin, Zhang Hui, Zhao Deli
    2002, 23(3):  241-243,247.  doi:10.11743/ogg20020308
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    Inclusions in Jurassic sandstone reservoirs in Yanqi basin are mainly distributed in Jianghe Formation and Badaowang Formation, their homogeneous temperature is between 101℃~110℃ and 121℃~130℃,carbon numbers of n-alkane appear in double- peaks state, main front peak with 18 or 20 carbon numbers, Main back peak with 26 or 27 carbon numbers. These features indicate that accumulations of oil and gas took place twice in the basin during the middle-late Jurassic, namely, the first phase is believed to be mainly for low matured oil & gas generation, migration and accumulation in Badaowang Formation in the late Jurassic, and the second phase is for the maturation of oil & gas in end Jurassic. It is believed by analyzing the history of hydrocarbon generation that the accumulation of oil and gas should have taken place once more in this region by the end Tertiary, this event has not been detected because of the inactive diagenesis and low abundance of the inclusions.

    SEVERAL GEOLOGICAL ISSUES ABOUT MESOZOIC-PALAEOZOIC OIL AND GAS PROSDPECTING IN SOUTHERN CHINA AND THE WAY OF HOW TO DEAL WITH
    Guo Tonglou, Tian Haiqing
    2002, 23(3):  244-247.  doi:10.11743/ogg20020309
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    Superimposed reformation of multi-cyclic tectonic movements experienced by marine basins in Southern China result in quite differences of oil and gas reserving in various areas. Therefore, a special regularity of the generation of oil and gas reservoirs (play) in these basins must be probed. Focal point shall be stressed in the research and each oil and gas play pattern shall be summarized accordingly to the feature of various areas by fanning out from point to area. At present, emphasis shall be put on the assessment of regional block tectonics and on the reassessment of re-determination and reserving conditions of hydrocarbon resource rocks when studying marine facies in Southern China. The latest exploration target can be selected out by dissecting play conditions of typical oil and gas reservoirs and getting to know favorable matching of play elements.

    CHARACTERISTICS OF BURIED HILL RESERVOIRS FROM LOWER PALAEZOIC OF JIYANG DEPRESSION
    Xu Guoshen, Li Guorong, Wang Zhixiong
    2002, 23(3):  248-251,256.  doi:10.11743/ogg20020310
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    According to the development of fissures and karsts, Jiyang depression can be divided into four types of arched-extension fold, fractured-block fault, weathered- remaining hillock and multi-phases structure composite. Reserving space for the first and second type above mentioned are mainly fissures- dissolution cavities, electric resistances in both flanks of reserving intervals are lower, and time difference of the sound wave often jumps; Space for the third type are karst-remaining hillocks; The fourth type represents features of above multi-compositions. In the lower Palaeozoic in Jiyang depression, reservoirs(bodies) in arched-extension fold type are mainly developed on the weathered crusts of the folded- mountain with evidence of dezoning vertically of the karst effect. In the case of reservoirs in fractured-block fault type covered by the upper Palaozoic roof rocks, the karst belts are developed in stratification and progressing in sequence in large area. In the case of those uncovered by the Upper Palaozoic roof rocks, dissolution cavities, holes and fissures are well developed. Reservoirs in weathered- remaining hillock type are commonly developed on the whole remaining hillock-mountain. Outcrop area in reservoirs in multi-phases structure composite type is a favorable area for the development of reservoir and with the vertical development of the karst belt.

    APPLICATION OF LINEARIZED SEISMIC PROFILE IN SEDIMENTARY FACIES RESEARCH
    Zhang Xinrong, Wang Dongpo, Gao Fuhong, Xu Kaizhi
    2002, 23(3):  252-256.  doi:10.11743/ogg20020311
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    Linearization processing is somehow to turn black and white isopic axis into a line where the positive axis indicated by a solid line while the negative axis shown by a dotted line. After the linearization processing, geological information in the available two dimensional or three dimensional geological profile will be more highlighted and reflect it more clear for what it is. Take Yingcheng Formation within Anda fault depression in Songliao basin for example, a corresponding relation between seismic phase and sedimentary facies has been established by analyzing single well facies of Dashen No.1 well and through sedimentary microfacies division.It is believed by interpreting sedimentary facies after the linearization processing for through wells and non-through wells in the region that in the period of Yingchen Formation the volcanic activity was strong and overflow facies was a dominant one developed by swamp facies, braided stream facies and semi-deep lacustrine facies etc. The extension of the sedimentary facies belt is just like a ringlike belt divided into two S-N fault depressed lakes by the uplift, small Anda area in the north is mainly composed of flood plains with volcanic rocks in the middle and Mingshui slope and hills around are believed to be material source areas; Small Songzhan area in the south trend to E-W direction with the volcanic rock uplift at the center, and with two semi-deep lacustrine deposit centers and uplift zones around are material source areas.

    SEDIMENTARY CHARACTERISTICS OF EOGENE PINGHU FORMATION AND HUAGANG FORMATION IN CHUNXIAO ZONE OF XIHU LAKE DEPRESSION
    Wang Guoshou, Zhou Zuoming, Xiao Chaohui, Li Meizhou, Zhou Weikui, Wang Lin
    2002, 23(3):  257-261,265.  doi:10.11743/ogg20020312
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    Eogene Pinghu Formation and Huagang Formation can be divided into four main sedimentary systems of semi-closed bay, lake, delta and river; and six main sedimentary types of shore-tidal flat, lagoon, shore-lake, river-controlling delta, tide-controlling delta and river etc., and several subfacies and microfacies. The development and evolution of the sedimentary systems in Pinghu Formation and Huagang Formation indicate change characteristics from the sea to the land; namely Pinghu Formation is chiefly composed of semi-closed bay environment with its own feature of development of bay-lagoon facies which is distributed largely in the central belt of working area. Huagang Formation consists mainly sedimentary systems of lake, delta and river which apparently can be divided into two sedimentary systems; the lower section is made up of ingression lake facies, the upper section is composed of fresh water lake sediments and interlayering sediments of meandering river flooding plain. The lake sedimentary system is mainly distributed in the northeast and central part of the working area, the delta system is chiefly developed in the south and southeast part of the working area while the meandering river system developed in the west part. Tidal channel, tidal-flat bar, river mouth bar, front sheet-like sand and microfacies of braiding flow river are main favorable reservoir belts in the area.

    CHARACTERISTICS OF ORDOVICIAN CARBONATE ROCK RESERVOIRS IN TAHE OILFIELD
    Yan Xiangbin
    2002, 23(3):  262-265.  doi:10.11743/ogg20020313
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    Rock cores testing indicate that space of carbonate rock reservoirs in Tahe oilfield are mainly interparticle pores, fissures and cavities; Their matrix almost do not have reserving capability. Reservoirs in cavity type, weathering fissure type and structural fissure type are commonly developed in Tahe region. Fissures in the surface eluvial belts-cavity reservoirs are largely spread near the unconformable contacts of C1 and O1. Reservoirs in dissolution porosity- type in particle limestone in the platform edge of bank facies are commonly spread along the area of the lower Ordovician in Southern Sha well No.76.It is conjectured by analyzing relations between extension of the fissure series and the diagenetic fabrics that the cam shaft part in Akekuler would be favorable well-developed area for reservoirs in cavity type. New results from well drilling indicate that the area along well S69-S76 in southern margin of Tahe oilfield will be a very important one for the exploration of reservoirs in dissolution porosity-type in particle limestone in the platform edge of bank facies.

    SEDIMENTARY CHARACTERISTICS OF QUANTOU FORMATION IN LISHU SAG OF SONGLIAO BASIN
    Tang Liming, He Xinghua
    2002, 23(3):  266-268,273.  doi:10.11743/ogg20020314
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    The mainly developments of sedimentary facies in Quantou Formation of Lishu Sag in Songliao basin are as follows: alluvial fan, braided river, mendering river, shallow water lake and shore shallow water lake etc. Slightly vibration-uplift and subsidence of the basin make it possible to divide it sedimentary evolution into 4 stages; early stage(Quan No.1 interval) is the stage of fault subsidence transited to sag deposition; middle stage(Quan No.2 interval) is the stage of large scale shallow water lakes developed due to great subsidence rate of the basin and weak effects of river alluviation, and sedimentary environment is composed of shallow water lakes, flooding lacunae and a few meandering rivers; later stage(Quan No.3 interval and middle stage of Quan No.4 interval) reservoir intervals were quite developed due to the slow down of regional sedimentation and reinforcement of river effect; during final stage(later stage of Quan No.4 interval)Songliao big lake-basin came into an embryonic form and began to expand due to the effect of the development of the whole basin. Sedimentary evolution of Quantou Formation has experienced a complete sedimentary sequence of river alluvium plain sedimentation representing the sedimentary characteristics of transformational period of Songliao basin fault sag.

    RESERVOIR CHARACTERISTICS OF GAO NO.81 BLOCK AND ITS HYDROCARBON-BEARING POTENTIAL IN GAOSHENG OILFIELD
    Tang Qingshan, Chai Liwen, Huang Taiming, Gao Zhenzhong, Kuang Hongwei, Tong Yanming, Liu Chenxin
    2002, 23(3):  269-273.  doi:10.11743/ogg20020315
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    Gao No.81 Block in Gaosheng Oilfield of Liaohe basin is a monocline structure plunging towards east, and its confined by faults in three directions of northwest, southwest and southeast. The oil bearing strata is upper sub-member of Es4 which is mainly composed of fan-delta sediments, and its lower part(Dujiatai oil layer) is fan-delta front subfacies, consisting of underwater distributary watercourse, river mouth sandbar and interfluve microfacies.Whereas its upper part is chiefly made up of profan-delta subfacies which is interbedded by underwater distributary watercourse and river mouth sandbar of fan-delta front subfacies occasionally. Dujiatai oil layer can be divided into three sand groups, located at the upper part of the layer, No.1sand group has great change laterally, whereas No. 2 and No.3 group(below No.1) which are quite stable. The physical property of reservoir of No.3 sand group is believed to be the best, and with the greatest effective thickness of oil bearing on the average and oil bearing area is relatively large too. Therefore, No.3 sand group has made greatest contributions to reserving oil and gas in Gao No.1 Block. No.2 sand group, with small effective thickness of oil bearing on the average, lowest oil-water interface and largest oil-bearing area, has made less contributions to reserving oil and gas on the average than No.3 sand group. No.1. group tends to pinch out towards the higher part of the structure and has made a little contribution to reserving oil and gas due to its highest oil-water interface and smallest oil-bearing area.

    CHARACTERISTICS OF COMPOSITE FAN BODIES IN WEIZHOU FORMATION OF BEIBUWAN BASIN AND OIL & GAS PROSPECTING SIGNIFICANCE
    Du Zhenchuan, Wei Kuisheng
    2002, 23(3):  274-278.  doi:10.11743/ogg20020316
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    Sequence stratigraphy of Paleocene system in Weizhou Formation of Beibuwan basin can be divided into 3 extra sequences and 9 Ⅲ-order sequences, a composite fan is largely developed in lowstand system tracts of extra sequence I, Ⅱ and Ⅲ in the low part of Weizhou Formation. Rocks with coarse lithology are found namely, massive miscellaneous sandstone, conglomerate bearing sandstone with graded bedding, moderate coarse sandstone, massive bedding sandstone, sandstone with cross bedding, siltstone with wave bedding or deformed bedding, mudstone with horizontal lamination bedding and typical turbidite etc. The composite fan, as for its distribution and form, was formed due to cross-superimposition of leafy body which chiefly originated from braided channel and gravity flow waterway during lowstand sedimentation and has double original features of traction current and gravity flow. The fan body was formed by gradually prograding of clastic sediments from the slope of lake edge to the lacustrine basin, produced from downwards to upwards a succession of sediment namely, distal fan,medium-part fan and near-end fan. Curves of well-logging show as fingerlike or tooth-like, toothed box-like and bell-like with high and medium amplitude and seismic reflection is a hill-like protruding. The composite fan surrounded by hydrocarbon- producing lacustrine mudstones is a favorable assembly for hydrocarbon origin, reserving and capping, with quite good physical properties, where stratigraphic traps or structure-stratigraphic composite trap hydrocarbon reservoirs are commonly formed.

    STOCHASTIC SIMULATION OF P2w1 CONGLOMERATE OIL RESERVOIRS IN BLOCK 530 OF KARAMAY OILFIELD
    Xiang Yuzhang
    2002, 23(3):  279-284.  doi:10.11743/ogg20020317
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    Two-Step Stochastic Simulation is employed on the basis of the characteristics of P2w1 conglomerate oil reservoir in block 530 of Karamay oilfield namely; seismic phase, logging phase, well testing phase as well as data collected from analysis of the rock cores etc. are used in setting up a succession indicator simulating reservoir sedimentary model and the semi-Markov simulating space distribution of reservoir property parameter either in consideration of sedimentary history or in consideration of sedimentary mechanism to simulate respectively sediments in the study area and characteristic parameters of reservoir physical property. It can be obviously observed from the static model of reservoir sedimentary facies established by setting up a succession indicator simulating reservoir sedimentary model that ancient waterflow entering sedimentary area from upper left part, and where subfacies of middle part of the fan and edge of the fan in the downdip block of the fracture deposit and subfaices of the fan top is absent, XW3 sediments are uncontinuously and XW2 sediments become gentle and even. It can be seen very clearly from reservoir characteristic parameters of the static model set up by the semi-Markov simulating technique that the thickness of XW3 sediments is great and change frequently, the thickness of XW2 sediments is small and with a distinct regularity. Variation value of XW3 porosity and permeability is greater than that of XW2 but saturation of oil content is on the contrary. It is believed by simulating predication that parameters of the reservoir physical property near the west section of Ke-Wu fracture zone is better than that of other sections, and which is a favorable oil and gas reservoir region where first priority for prospecting should be given.16 wells have been cancelled from well pattern(saved drilling footage 4.27?104 m) because of the reservoir space distribution regularity accurately expressed by the static model of the reservoir.

    CHARACTERISTICS OF MESOZOIC VOLCANIC ROCKS AND ITS CONTROLLING EFFECT ON GAS RESERVOIR IN SONGLIAO BASIN
    Meng Qian, Men Guangtian, Zhao Hongwen, Jiang Tao, Shao Mingli
    2002, 23(3):  285-288,292.  doi:10.11743/ogg20020318
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    Volcanic rock reservoir is a main target layer for deep gas exploration in Songliao basin, controlled chiefly in distribution by deep and major fractures showing widespread in belt along the fracture not only in mountainous areas but also in sedimentary layers in the fault subsidence basins; Space of the reservoir are observed to be primary bubble pores, amygdale interior pores, secondary phenocryst solution pores, matrix dissolution pores, structural solution fissures. Pore structural assemblies are discovered to be pore structures made up of unitary fissures, phenocryst solution pores and fissure assemblies. Three stages can be divided in terms of origin namely; primary bubble pores formed in the period of overflow eruption, secondary pores originated by the process of weathering eluviation in the period of eruption intermittent and diagenesis and structure effects in the burial process. Fissures are key factors for the improvement of property of volcanic rock reservoir, diagenesis either intensified secondary pore fillings or intensified the formation of solution fissures,compaction has no an effect on the reservoir property . Relatively independent distribution of volcanic rocks in hydrocarbon source rocks make it possible for them to have exceptional advantages for the formation of reservoir, tectonic movements and deuteric weathering-erosions are main factors for controlling property of the reservoir,development of fractures controls the distribution of gas reservoir.

    RESERVOIR CHARACTERISTICS FOR VOLCANIC ROCKS FROM MEMBER Ⅰ,Ⅱ OF FUNING FORMATION IN NORTHERN MINBEI REGION IN SUBEI BASIN
    Ji Guosheng, Dai Junsheng, Ma Xinben, Wang Zhiyun
    2002, 23(3):  289-292.  doi:10.11743/ogg20020319
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    There are mainly two types of pores(primary and secondary) in the space of volcanic rock reservoirs in northern Mingqiao region of Jinhu depression in Subei basin. The primary pores consisting of intergranular pores,intercrystalline pores, gas pores and primary joints were formed during the accumulation of volcanic rocks and diagenesis. The distribution of the primary pores are mostly isolated and filled. The secondary pores including intraparticle dissolution pores, dissolution pores, seams and caves etc. were formed after the diagenesis of volcanic rocks caused by the effects of weathering, leaching, dissolution and structural stress. The secondary pores can improve reservoir quality greatly especially for structural joints and play very good rule in communicating isolated primary pores. The ratios of porosity and permeability of a rock flow unit in the profile are observed to have a trend of being enlarged gradually from downwards to upwards by analyzing volcanic rock porosity and well log of permeability. Variations of porosity and permeability in a rock flow group correspond to these in a rock flow unit or reveal several repetitions of the same regularity above. The ratio variations of porosity and permeability of east-west in the study area are quite big while ratio variations of south-north are relatively stable. Reservoir qualities of Ⅶ-Ⅺ rock flow group in 1st member of Funing formation and Ⅲ rock flow group in 2nd member of Funing Formation are quite good.

    PREDICATION OF THE CARBONIFEROUS DISTRIBUTION IN TONGNANBA STRUCTURE
    Chen Zhenlin, Luo Kaiping, Chen Xiao
    2002, 23(3):  293-294.  doi:10.11743/ogg20020320
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    The Carboniferous(only exists in Huanglong Formation)is the most important set of resevoir among carbonate rock strata in eastern and northeastern Sichuan and western Hubei.It is discovered that the distribution of the Carboniferous in unstable and present in some areas in scattered pattern or even completely absent.The Permian in surrounding outcrop areas of Tongnanba structure is in diredct unconformity contact with the Silurian where the Carboniferous can not be found.However,reflection distribution in the seismic cross section,below reflection of TP 1(bottom of the Permian)and above weaker reflection of the Silurian,appears to be in uncontinuously pattern and corresponds to higher impedance area of odd distribution of wave impedance>230?105(kg/m2·s,these features indicate that the Carboniferous exists in the center of Tongnanba structure.

    CHARACTERISTICS OF OIL AND GAS BEARING SYSTEM IN XIHU LAKE DEPRESSION IN THE EAST CHINA SEA
    Gu Huirong, Jia Jianyi, Ye Jiaren
    2002, 23(3):  295-297.  doi:10.11743/ogg20020321
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    Xihu lake depression in the East China Sea has gone through three stages of development since the late Cretaceous, forming three sets of oil and gas systems of Pinghu Formation Huagang Formation, Huagang Formation and Eocene, the former two sets are-known systems, the latter system is a conjectured one. Hydrocarbon source rocks in these two systems are in the stage of maturation. The closure of oil and gas bearing roof rocks in Huagang Formation deteriorates from southward towards northward and the south part with real meaning for oil and gas exploration. Comprehensive analyses indicate that the key moment for oil and gas bearing system in Pinghu Foprmation and is about 7 Ma, oil and gas bearing system in Huagang Formation is about 1.64 Ma.

    EVALUATION ON PERMIAN OIL AND GAS BEARING SYSTEM IN YINING DEPRESSION
    Xiong Liping, Jiao Daqing, Liu Tiezhuang, Ma Fangxia
    2002, 23(3):  298-299.  doi:10.11743/ogg20020322
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    Tiemulike Formation in the Permian above Yining depression is mainly composed of hydrocarbon source rocks which has formed two complete oil-bearing systems of P2t-P2t self-generation & self-reserving and P2t-T2-3 lower intervals generation and upper interval reserving. The former system is a known system proved by drilling; the latter system is a system by deducing. The basin thermo-modeling results and comparatively analysis with Junggar basin indicate that the Permian oil and gas-bearing system in the depression had entered into hydrocarbon generation threshold by the earlier Triassic and had reached the peak of hydrocarbon generation by the earlier of the middle Jurassic and had ended oil generation and then gone into gas generation by the end Jurassic. Large scale of oil and gas generation and migration occurred in J3-J1-2,the last Indo-China episodic tectonic movement(208Ma up to now) is a key movement of the system. The southern slope in the depression is believed to be a favorable region for the exploration of oil and gas on the basis of multi-analyses of the degree of oil and gas-filling, migration direction and trapping conditions etc.

    OIL & GAS RESERVOIR TYPES IN THE WESTERN REGION OF HUNAN AND HUBEI AND EXPLORATION ORIEN TATION
    Hu Xiaofeng
    2002, 23(3):  300-302,306.  doi:10.11743/ogg20020323
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    Located at the slope of an ancient structure, the weak reformation of the structure in the north central part of Huaguoping composite syncline in the region of Hunan,westernHubeiandthe central part of Sangzhi-Shimen composite syncline is a favorable region for exploring a primary oil and gas reservoir. Located below the slope of the ancient structure, the weak reformation of the structure in southern Huaguoping composite syncline and western Sangzhi-Shimen composite syncline is expected to find an inherited oil and gas reservoir. Only a reconstructive type oil and gas reservoir can be found in the remaining lower part of the oil and gas generation assemblage in the center of Yidu- Hefeng composite syncline and the upper part of the oil and gas generation assemblage of the central composite syncline due to intensively reformed by the tectonic movement and the Silurian roof rock being eroded.

    APPLICATION OF ORGANIC CHEMISTRICAL METHOD IN DISCRIMINATING OIL-WATER STRATA IN TARIM CARBONATE ROCKS
    Chen Chuanping, Sun Weilin, Yuan Zhihua, Su Xiufang, Mi Jiliang, Huang Kenan
    2002, 23(3):  303-306.  doi:10.11743/ogg20020324
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    When oil content saturation in carbonate rock reservoirs is>50%,it is called oil layer; when oil content saturation is <10%,it is called water layer. In terms of medium oil, oil bearing rate in rock cores of carbonate rock and rock porosity can be gained by employing rock pyrolysis and interpretation of electrical logging, by calculating visible oil content saturation in the rocks and then reservoir nature can be discriminated. Visible saturation in light oil has no real meaning to discriminate reservoir nature. The discrimination of oil-water strata are mainly based on the gas chromatographic characteristics from organic solvent extractions. Oil-water layers discriminated in Tarim basin with this method have been proved by well drilling.