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    25 March 1983, Volume 4 Issue 1
    NOTES ON ANCIENT GLOBAL TECTONICS AND PALEOZOIC PETROLIFEROUS BASINS
    Zhu Xia
    1983, 4(1):  1-33.  doi:10.11743/ogg19830101
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    The author postulated about 20 years ago that petrolierous basings,as a specific kind of sedimentary basins,are the Products of geodynamic(geotectonical and geothermal)regimes which influence the globe as a whole and change with time throughout the geological history of the earth.As there are so many unidirectional changes in earth properties.it would not be unwise to consider the development of petroliferors basin an evolutionary instead of an uniformitaristic way,and to classify the Paleozoic and the Meso-Cenozoic basins on a dualistic basis in accordance with the respective regime of global tectonsics.For practical purposes,especiallyfot the evaluation of less-explored petroliferous basins.it is suggested(see fig.1 in Chinese text)to relate the 4M factors[material,maturity,migration versus nonmigration (trapping) and state of maintenance],which control the location(L) and the potential quantity(Q) of oil and gas,to the 4S conditions(subsidence,sedimentation,stress and style)of a basin taken as a whole.The basin,in its turn,is composed of one or several prototypes(P) Which owe its existence to the mechanisms of formation determinative with the tectonic setting and the thermal regime prevailing at the time of thei,formation(3T).Consequently,we ought to be able topredict the habitat of petroleum in different basin types of different geological agesthrough the analysis of T,S,M,and to treat them with different thoughts and methods of prospecting.To group the Paleozoic basins with the Meso-Cenozoic intraplate basins under the general heading of"cratonic basins"as some current classification schemes do,seems to be inadequate and would not but lead to the disappointing statement that cratonic basins are"deceptively simple",as they do not really be. "Plate tectonics offers a framework within which many of the processes of more recent continental evolution can be understood,but as we deal with increasingly ancient Portions of the continents,it is increasingly difficult to test the applicability of the plate-tectonic concepts".Continental tectonics,of which the development of "cratonic"basins and arches being important constituents,must be explainable asa part of a global geodynamic system,however,whose component processes may have changed through geological times.To reason with it,the author tends to differentiate on historical-geodynamical ground the formation of petroliferous basins since as early as late Proterozoic into 3 stages:1.The ancient global tectonic stage ranging in age from the break-up of the Proto-Supercontinent or Pangea E to the formation of Pangea B;2.An intermediate stage as the mobile Pangea B developped into Pangea A;and 3.A new global tectonics or plate tectonies stage related with the break-up of Pangea A in the latest 200 m.y.

    GEOLOGICAL CONDITIONS OF PERMO-CARBONIFEROUS COAL-FORMED GAS IN NORTH-CHINA PLATFORM AND ITS PROSPECTS
    Cai Qianzhong
    1983, 4(1):  34-44.  doi:10.11743/ogg19830102
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    Permo-Carboniferous system in North-Chjna platform is rich in coal,and has formed three enriched zones,the ages of which are getting younger. from north to south (fig.1). After Permian,the platform was activated and dismembered. The west part (Ordos) was depressed,the middle part (Shanxi plateau) uplifted and the east(the North-China plain) block-faulted. The coal beds underwent recoalification and formed a large amount of coal-formed gas as were deeply buried by Meso-Cenozoic sediments. It is observed that the coals in this platform are mainly cocking coal and anthracites,the major component of the gas is methane. Its potential reserve is up to 6?1012cu.m. with Ordos and the North-China plain to be the most favourable regions for gas prospecting. Three types of gas pools discovcred are also discussed in this paper: the water-sealed hysterogenitic gas pool (Yangquan Coalfield),the salt-sealed secondary gas pool(Wenliu Gasfield) and the argillaceous rock-sealed primary gas pool(Liujiazhuang Gasfield).

    STRATIGRAPHIC OIL POOL IN EOGENE SUBAQUEOUS ALLUVIAL FAN IN DONGYING DEPRESSION
    Yang Shenpiao, Yang Ruichi, Liu Taicheng
    1983, 4(1):  45-52.  doi:10.11743/ogg19830103
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    Dongying depression has experienced evolution of blockfaulting,erosion and overlapping during Eogene,resulting,in a gently Waved erosional surface of basement rocks on its north steep slope where lacustrine embayments were separated by basement;noses and subaqueous alluvial fans well developed,These paleomorphological and paleotopographical features have obviously controllcd the size and geometry of fans,which can be divided into three types:1) lacustrine cliff fans;2) faulted scarp fans:and 3) terraced fans,with the first one being the dominant type. They are coalescing each other to form a kind of skirt-hem. The fans are sand and conglomerate bodies formed by rapid deposition of flood turbidite near the source area.It has become a new field for the exploration of oil and gas,since it may contain important stratigraphical types of oil traps. Different parts of these fans form different traps The model roughly is: the innerfans form stratigraphical overlapping traps;the mid-fans lithologic traps sealed by faults;the outerfans lenticular lithologic traps. The basement noses are the prerequisite ground for oil accumulation. The mid-fan front and channels,having a lot of secondary pores and good reservoir properties,may be prolific in oil and gas.

    EARLY TRASSIC CARBONATE GRAVITY FLOW ALONG THE NORTH MARGIN OF SHIWANDASHAN BASIN AND ITS GEOLOGICAL SIGNIFICANCE
    Gao Zhengzhong, Liu Huaibo
    1983, 4(1):  53-65.  doi:10.11743/ogg19830104
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    The lower Trassic developed on the north-west slope of Shiwandashan basin in Guangxi is represented predominently by marine carbonate sediments,which can be subdivided into two opposite lithofacies zones according to their sedimentaty attributes. The north facies zone,occurred at carbonate platform,is featured by oolitic limestone,894-970m thick;while the southern one,developed in a basin environment,is represented by lamellar limestones,warty limestones and shales,as well as psephitic and calcarenites,the thickness of which varies from 307-521m. The lamellar limestones,warty limestones and the shales are autochthonous rocks,whereas psephitic and calcarenites are allochthonous sediments,i.e. carbonates of gravity flow origin. Gravity flow in present region can be divided into three types,notably debris,turbidity and grain. Of them,the most important one is debris flow which have givrn rise to more than a hundred meters of sediments. varying from bedded to massive coarse calcirudites and occupying 80-90% of the total thickness.Turbidity flow is composed of fine calcirudites and calcarenitos with positive gradation. This type of rocks is widely distributied and characterized by minor thickness for each individual bedding. Grain flow consists of medium calcirudites to calcarenites,with a rather unighe texture. On probability diagram showing gradation,all kinds of gravity flow sediments exhibit gentle and smooth curves covering a wide size range of particles,but each type of sediments have its own attributes. They are clearly different in their size range parameters and have distinction both on CM and scatering diaagrams. Gravity flow sediments were derived mainly from the simultaneous carbonate platform sediments(extraclasts),and also from micrites consolidated to some extent in the basin (intraclasts). A steeper slope primarily existed between the platform and the basin,the depth of which at the end of Trassic might be 800-1000m. The study on carbonate gravity flow not only can make direct contribution to dealing with sedimentary environment and compilation of lithofacies-paleoge-ographical map,but also give important guidance to petroleum prospecting and exploration.

    PALEOHYDROLOGICAL CONDITIONS IN RELATION TO OIL AND GAS OF TAIZHOU REGION
    Gong Yujin
    1983, 4(1):  66-75.  doi:10.11743/ogg19830105
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    Underground waters were involved in the entire proeesses of betroleum generation,migration,concentration and deterioration,An important approach for recognizing regularities of oil and gas distribution,therefore,is to study the evolution and motion of underground waters in oil- and gas-bearing basins. As for the case of Taizhou,Jiangsu proyince,hydrological phases and subphases are divided according to paleotectonic and sedimentary settigns. It is suggested that the form ation and preservation of oil and gas are related to hydrological subphases of deposition waters,while remigration,evolution and deterioration ofoil and gas to hydrological subphases of percolation waters. Based on paleogeo-logic characteristics and paleohydrodynamics,promising zones for oil and gas migration and concentration,i.e. the fault-step zones,and complicated hydrological patterns of deposition or/and percolation waters are described. Paleonydrological environments and tectonic traps which may produce negative influence to reservoirs are also discussed in terms of indensity index of water interechange,hydrochemistry,physical and chemical properties of petroleum and content end distribution of superficial minerals. Finally,a principle for evaluation of oil potentiality is given from the hydrological point of view.

    A OPTIMAL METHOD OF DIGITAL PROCESS FOR LOG INTERPRETAION OF COMPLICATED STRATA
    Ouyang Jian, Wang Yunwei, Hu Shufen
    1983, 4(1):  76-88.  doi:10.11743/ogg19830106
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    Oil exploration of Jiyang depression has recently been proved that Mesozoic,formations are favorable to hydrocarbon accumulation,and some oil reservoirs heve,therefore,been discovered. Based on well loge and. other imformation .available,the authors systematically studied the mineral composition,physical .pro-perties and distribution of reservoirs of petrologically complicated,Mesozoic in present region,and have developed a new .method. of log interpretation supported by an computer program. This method is based on geophysical inversion theory using optimization.method for calculation. It covers a log interpretation model established for lithologically complicated formation,and may be used for analyzing errors of well logs,correcting influence of various environmental factors for logs and checking geological parameters calculated. Geological results obtained by this. method in. processing log data on .Mesozoic formations of Jiyang depression are obviously.better than that by coventional digital processing method.

    GONANES AND TERMNES FROM CRUDE OIL AND SOURCE ROCKS IN JIZHONG DEPRESSION
    Zhang Zhencai, Wang Zhongran, Chen XianZhong, Zeng Xianzhang
    1983, 4(1):  89-99.  doi:10.11743/ogg19830107
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    Crude oils and source rocks in Raoyang and Beijing-Tianjin sags as well as in the east slope of Ningjin uplift of Jizhong(central Hebei)depression are compared by the parameters of gonane and terpane stereoisomers.It is shown in a preliminary way that oils in Sinian buried hills of Renqiu Oilfield might come from different sources around,i.e.from the 1st and 3rd members of Shahejie Formation (E3s);oils in Ordovician in the north slope of this field from Kongdian Formation (E2k)of Bacian sag;oils Beijing-Tianjin region primarily from the 4th member of Shahejie Formation and Kongdian Formation,whereas oils in the 3rd member of Shahejie Formation might come from insitu.Oils in the 4th member of Shahejie Formation in th east slope of Ningjin uplift still preserved clear marks of terpanes,though they were subjected to biological degradation,this implies that these oil might come from the saline 4th member of Shahejie Formation. Thermal evolution of source rocks in Jizhong depression is discussed with three gonane and terpane parameters,which can accurately reflect the threshold depth and the peak of oil generation.According to the abundance of gonanes and terpanes,as well as the amount of gammacerane in saturated hydrocarbons,the authors suggest that the organic matters in Raoyang sag is better than that in Beijing-Tianjin sag.

    SOME PROBLEMS CONCERNING LITHOFACIES AND PALEOGEOGRAPHY OF CARBONATES
    Feng Zengzhao
    1983, 4(1):  100-108.  doi:10.11743/ogg19830108
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    Study on carbonate lithofacies is rapidly developed during last 20 years and great achievrments have been made.However,the method used for graphic compilation is out-of-date,and does not fit the progress made in studying lithofacies.The author holds that the following problems should be duly considered in work of lithofacies study:1)avoidance of schematic illustrations;2)Strength ening the study on the of rocks,especially of dolomites ;3)correct interpretation of isopach map,for instance.zero isoline might not mean old land;what is more important is the existence of marginal sediments;4)petrofabrie method which is liable to mix up rocks of different origin not suitable for elucidating sedimentary fecies and paleoseomrphology. All these factors and variables,such as structure and texture of rocks,biological assemblages and ecology,etc.which could independently reflect certain aspect of sedimentary environment,should be counted up according to mapping units so as to make regional isogram.Thus,a paleogeographic map in.numericalquantities can be conpiled after overall considering regularities of variation of individual While making the Huabei and Ordos paleogeorraphic maps of Yehli stage (Early Ordovician),the author has used single factors such as thickness,gtsins,colour and penecontemporaneous dolomite,etc,as well as terrigenous detritus,intrabasin detritus,open sea biota,calcareous algae and gypsum,and obtained a good result.

    PRELIMINARY STUDY ON PETROLEUM POTENTIAL OF UPPER PALEOZOIC IN NORTHERN ORDOS BASIN
    Sun Guofan, Liu Jingping, Miao Yongwang
    1983, 4(1):  109-115.  doi:10.11743/ogg19830109
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    Ordos basin was part of the North-China platform in the early Paleozoic,while the western Qilian geosynelins was located on oceanic crust.In between them,there was a trunsitional continental slope inclined westward.This tectonic setting had played a evident part in controlling the formation of marginal depression in western Ordos from Paleozoic to Jurassic.The hinge line of the westward dipping continental slope mightbe located at about 107癊.Carboniferous sediments of "depression type"are developed to the west of 117癊 along the mid-north segment of the west margin ordos basin,and farther east are sediments of "wide-spread type"The later distributed widely in the northern Ordos basin are less worth oil and gas prospecting.The hinge zone is lithologically developed with various transitional facies and altenated each other where the best association of oil source and reservoir rocks may occur.Moreover,oil and gas.originated in the marginal depression might have migrated toward the eastern area since the Late Paleozoic.So,there should be an area of good hope for oil and gas prospecting.

    IS MT. XUEFENG A NAPPE? WHERE IS OIL AND GAS OF CENTRAL HUNAN?
    Guan Shicong, Yuan Jie, Xu Mingguang
    1983, 4(1):  116-120.  doi:10.11743/ogg19830110
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    Mt.Xuefeng is considered by some people to be one of the nappes stressed from E.to W.in the south of Yangtze R.,and they suggest that oil traps might occurred in Lower Paleozoic or Anyuan coal series(T3-J1)under the so-called basement ramp. Through field observation,we learnt that this mountain is composed mainly by Banxi Group(Pt3)and Lungshan Series(PZ1)set vertically in occurrence,high augle thrust might be seen here and there along both sides of the range,and they stressed mostly from west to east,but not the opposite.Therefore,we have to say that this mountain is rooted,not napped.Paleozoic carbonate formations,as good overing beds,might somewhere overthrust upon the Anyuan coal series.But exactly the distribution of the later is rather limited,and then,the prospecting for oil and gas is not so good. And where is the oil and gas of Central Hunan?We have always considered that the upper Paleozoic formations in Qiyang Arc would be the most hopeful one.

    GEOCHEMICAL CHARACTERISTICS OF CRUDE OILS FROM QAIDAM BASIN
    Wang Youxiao, Cheng Xuehui, Wu Yihua, Chuan Lanlan
    1983, 4(1):  121-127.  doi:10.11743/ogg19830111
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    Crude oils of different ages (J2,E3-N21,and N22)from Qaidam basin can be divided into three types according to the patterns of distribution of hydrocarbons on chromatogram.Among them.the maturity of crude oil J2 is higher.The main peak carbon of normal pararffins is C15,and the pristane to phytane ratio is 2.44—2.90.Crude oils E3-N21 are characterized by higher Phytane peak than other.The pristane/phytane ratio 0.86—0.52,and the main peak carbonof normal paraffins commonly is C22.It is obvious that even carbons play a dominant role on chromatogram of normal paraffins.For crude oil N22,the light components take a prevailing place.The main peak carbon of normal paraffins is C13,while the pristane/phytane ratio is 1.26.In N1 and N21,there are some crude oils formed by degradation,in which the action of microbes is of prime importance.Neady all normal paraffins are degraded by microbes,therefore,the isoprenoids are the foremost on the whole hydrocarbon chromatogram.Questions of migration of crude oils are also tentatively discussed here.

    RELATIONSHIP AMONG THE SHOUCHANG,HENGSHAN AND GUANTOU,FORMATIONS IN ZHEJIANG
    Chen Qishi
    1983, 4(1):  128-130.  doi:10.11743/ogg19830112
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    Relative positions of the Shouchang Hengshan and Guantou Formations are discussed on the basis of Laozhu section(Lishui countr)combined with some regional data available。 The mafn conclusions are follows: 1.The Hengshan Formation should be underlain the Guantou Formation but overlain the Shouchang Formation. 2.The boundary between Jurassic and Cretaceous continental sediments in Zhejiang should lie between the shouchang and Hengshan Formation.