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    25 June 1990, Volume 11 Issue 2
    BURIAL DIAGENETIC GEOTHERMOMETER AND RESERVOIR ZONING CHARACTERISTICS OF TERTIARY CLASTIC ROCKS IN SHENLI OILFIELD,SHANDONG
    Zhou Zili, Lü Zhengmou
    1990, 11(2):  119-126.  doi:10.11743/ogg19900201
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    To study burial diagenesis is very important for reservoir assesment.Petrological datafrom 66 wells suggest that the present temperature corresponding to the depth where burial diagenetic minerals occur is approximate or equal to the formation temperature.There-fore,the original formation temperature of the burial diagenetic minerals can be calculated by following equation.T=G(H-h)+14.5℃ where T is the original formation temperature of the burial diaganetic minerals;G isgeothermal gradient;H is the shallowest depth where this diagenesis occurs;h is the depth of constant temperature zone(assuming h=0 when T is calculated because it is very small in study area);14.5 is the annual average surface temperature in the area.Calcula-tion and error analysis show that the original formation temperature of different burial dia-genetic geother mometer are as follows.65±5℃ for weak over growth of quartz;90±5℃ for intensive over growth of quartz;92±5℃ for authigenic garnet;95±5℃ for late car-bonate cement(such as saddle dolomite);70±5℃ for authigenic kaolinite;140±10℃ for trans formation from kaolinite to illite.Based on all the diagenesis related to tempera-ture,four diagenetic zones can be divided,i.e.shallow,moderate,deep and superdeep zones.It is demonstrated that these zones can be used to classify and assess reservoir rocksand source rocks.

    TECTONIC CHARACTERISTICS AND EVOLUTION OF BAYANHOT BASIN,WESTERN INNER MONGOLIA
    Tang Xiyuan, Feng Qiao, Li Daosui
    1990, 11(2):  127-135.  doi:10.11743/ogg19900202
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    The Bayanhot Basin is a Meso-Cenozoic faulted basin,which is superimposed on dis-tinct crystalline basement.With Chaxan fault as the boundary,the north of it is the stable Alxa Massif,and the south is the active Qilian folded belt.The structures within the basin are characterized by normal faults associated with rolling anticlines.A few thrusts and compressive folds are distributed mainly over thesouth part.The direction of the structures is NWW trending in the south part,NE in north-west and near SN in the east.In the Middle Proterozoic-Early Palaeozoic,the northwest Part of the basin wasrosen,the south part was the passive continental margin of Qilian trough,and east parta aulacogen.In the Late Palaeozoic,its south part was a foredeep and the east part wasa impactogen.The region was widely uplifted and magmations and faults occurred during the Permian-Triassic,marked the beginning of fragmentation of Alxa Massif.A lot of minor faulted basins separately occurred in the Jurassic.It became an unitary sedimentarybasin in the Early Cretaceous.At the end of Early Cretaceous,the basin uplifted again andthe activity diminished gradually.The Carboniferous source bed has so far been evidenced in the basin,discoveringmany oil-bearing formations in it.Therefore,the east and the south depressed zones withthick Carboniferous sediments are the most favourable region in oil and gas potential.

    PRELIMINARY APPROACH TO RELATIONSHIP BETWEEN UPLIFTING HISTORY OF ALTUN MOUNTAINS AND SALT-FORMING CONDITION IN TARIM AND QAIDAM BASINS
    Zhu Yunzhu, Zhong Jianhua, Wu Bihao, Liu Chenglin
    1990, 11(2):  136-143.  doi:10.11743/ogg19900203
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    Altun Mountains were not boundary mountains between Tarim and Qaidam Basins after Indo-China movement or even earlier.It has been proved that the two basins werelinked up and connected to each other before the Quaternary.They share the same condi-tions of salt and sylvite generation.It was not until Post-Miocene that the mountains hadits embryonic shape of subaqueous uplifts;it further rose as island-like uplifts at the end of Neogene(2.6—2.10Ma.B.P.),and then became the boundary mountains to block the Tarim and the Qaidam Basins in Late Pleistocene(0.25Ma.B.P.).

    TYPE,GENERATION MECHANISM AND OIL POTENTIAL OF HALF-GRABEN BASINS IN MESO-CENOZOIC SEDIMENTARY BASINS IN CHINA
    Yang Kesheng
    1990, 11(2):  144-155.  doi:10.11743/ogg19900204
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    Sedimentary basins formed in the platform actived period on China's continent and shelf used to be classified into extensional,central transitional and west compressionalhydrocarbon-bearing basins by geological circles.The study of long seismic sections across these basins in recent years led to the conclusion that all the basins in China underwent both tensional and compressional movements.The hydrocarbon-bearing basins in EastChina did not only undergo tensional movement,but also compressional movement.Theearly half graben-like basins resulted from tensile stress,but the overlying fault-depressed basins reflect compression.In the west part of China,the compressional basins did not onlyundergo compression.The early half graben-like basins are also the result of tensile stress.The difference of the west part to the east part is that the normal faults on the boundaries of the half graben-like basins were replaced by overthrusts resulted from intensive com-pression in late stage,the overlying compressional basins were the result of compression.According to their evolution characteristics,assemblage pattern and relation to overly-ing strata,these half graben basins can be divided into inward-tilted,outward-tilted andunidirectional tilted types which can be subdivided into nine subtypes,namely fault-depressed inward-tilted subsidence,fault-depressed inward-tilted compression,singleinward-tilted,fault-depressed outward-tilted subsidence,fault-depressed outwards tilted compression,single outward-tilted,fault-depressed unidirectional-tilted subsidence,fault-depressed unidirectional tilted compression and single unidirectional-tilted subtypes.The half-graben basins are formed due to the rise of paleo-uplifts within the basins,thus faulting the weakest parts of resistant to tensile strength,The rise of paleo-uplifts can beexplained as follows:since the paleo-uplifts are usually distributed at paleocontinental kernels,and the kernels are situated at mountain roots where silica-alumina layer developewell due to the fold of paleogeosynclines,when new geosynclines or plates subducted toward paleoplatforms or paleocontinents to make lithosphere above soft mantle regionaltensility and less crowded,then the light silica-alumina mountain roots float upward forspheric balance of soft mantle,resulting the rise of paleo-uplifts gradually.As the subduc-tion angle increased during the late stage,the plates compressed or collided towards paleo-continents,thus forming the depressed basins overlying the half graben-basins.It has beenproved by prospecting practice that the mid stage of the formation of half graben-likebasins is usually the main oil-forming period.So the half graben like basins and its synde-posit mid-stage formations should be taken as the main targets for oil prospecting.

    APATITE FISSION TRACK ANALYSIS AS A PALEOTEMPERATURE INDICATOR FOR HYDROCARBON EXPLORATION
    P. F. GREEN, I. R. DUDDY, A. J. W. GLEADOW, J. F. LOVERING
    1990, 11(2):  156-177.  doi:10.11743/ogg19900205
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    Apatite Fission-Track Analysis(AFTA)is emerging as an important new tool for ther-mal history analysis in sedimentary basins.At temperatures between approximately 20℃ and 150℃ over times of the order of 1 to 100 million years,fission tracks in apatite are an-nealed.This is due to a rearrangement of the damage present in unetched tracks,with theresult that less of a track is etchable than in fresh,newly created tracks.Because of this,thelength of an etched fission track reduces with increasing annealing,and in turn,the track den-sity(and hence the fission-track age) is also decreased.In selected boreholes in the Otway Basin,southeastern Australia,apatites from the Otway Group show reduction in confinedfission-track length and apparent fission-track age,in a fashion characteristic of a simple ther-mal history in which samples are at or near their maximum temperatures at the present day.Track lengths show a steady decrease from lengths of approximately 15μm in outcrop ornear surface samples,to zero at about 125℃.Fission-track ages however show little or nodecrease in age until tempera tures exceed about 70℃.Above this temperature,ages rapidlyreduce to zero at about 125℃.Fission-track data from the Otway Basin contain more information than the simplede crease of age and length.The distributions of single grain ages show characteristic pat-terns,particularly above 90℃.The distribution of track lengths is also diagnostic of tempera-ture.In particular,in samples at present temperatures between 102℃ and 110℃,the distribu-tion of lengths is almost flat,with tracks of all lengths from approximately 1μm to 16μm.The temperature-sensitive,fission-track parameters observed in the Otway Basin may beapplied in other basins to elucidate paleo temperature details.In cases of mixed provenance,individual grain ages may be identified using the external detector method.Fission-tracklengths in apatites containing a significant track record at the time of deposition are generally characterised by one of two types of distributions,greatly simplifying inter pretation of distri-butions of track lengths in samples showing significant down-hole annealing.Presence of an inherited track component,or conversely of a total loss of tracks at some time since deposition,can be identified by a comparison of the stratigraphic age with thelength-corrected fission-track age.Investigation of five fission-track parameters then allowssemi-quantitative constraints to be placed on thermal history.Experiments are in progress toplace this procedure on a more rigorous,quantitative basis.AFTA offers numerous advantages over the other thermal history analysis techniques including the ability to provide a chronology of events.The method is now established in hydrocarbon exploration as a quantitative maturation indicator,and should find common application.

    REE GEOCHEMICAL CHARACTERISTICS OF MUDSTONES FROM EOGENE SHAHEJIE FORMATION IN DONGPU DEPRESSION
    Yu Huilong, Zhang Jinliang, Xu Lunxun
    1990, 11(2):  178-186.  doi:10.11743/ogg19900206
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    The total content of REE(ΣREE)from mudstones of the Eogene Shahejie Forma-tion in Dongpu Depression is relatively high,the average value is 215.34 ppm.Ce is thehighest of the REE group,ΣCe is richer than ΣY and ΣCe/ΣY is also high(2.73 on aver-age).These mudstones yield right declined W-shapped curves with negative Ce and Euanomalies,therefore,their REE distribution patterns are parallel to each other.In addi-tion,the REE parameters(Ce/Ce,Eu/Eu,Sm/Nd,ΣCe/ΣY,LaN/SmN and CeN/YbN) only vary with in a narrow range with small deviations.This indicates that theywere deposited in a lake basin environment.

    DIAGENESIS OF OLIGOCENE SHA-3 (3) SUBMEMBER IN MACHANG REGION,DONGPU DEPRESSION AND ITS RELATION TO HYDROCARBON
    Shou Jianfeng, Yuan Zhengwen
    1990, 11(2):  187-194.  doi:10.11743/ogg19900207
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    The Oligocene Sha-3 (3) submember in Machang region,Dongpu Depression is a large progressive deltaic deposit.It mainly underwent component-dissolution and dissolved-precipitation during the process of burial diagenesis.The first dissolution oc-curred prior to the peak period of hydrocarbon generation,and the dissolved pores areavailable spaces for hydrocarbon accumulation;the second dissolution happened after thepeak period and prior to the formation of cracking gas,the pores formed may have consid-erable significance for gas accumulation in deep and superdeep strata.

    DISTINGUISHING OF VOLCANICS LITHOLOGY IN JIAMUHE FORMATION OF PERMIAN SYSTEM,5-8 DISTRICTS,KARAMAY OILFIELD
    Kuang Lichun
    1990, 11(2):  195-201.  doi:10.11743/ogg19900208
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    Since the volcanics has a quite complicated composition,it is difficult to evaluate the content of different minerals in vlcanics by log data.The volcanics of the Jiamuhe Forma-tion of Permian System,5-8 distrcts,Karamay Oilfield is divided into volcanic breccia,basalt and rhyoporphyry based on the data of cross section,and distinguished using cross-plots.The paper also provides the values of density,neutron porosity,cross section index of effective photoelectric absorption and uranium,thorium,potassium contents.

    GEOCHEMICAL FEATURES OF CRUDE OIL/SOURCE ROCK IN FS SAG,HAINAN ISLAND
    He Jiaxiong, Zan Lisheng, Zhang Hongyou
    1990, 11(2):  202-204.  doi:10.11743/ogg19900209
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    Crude oil in FS Sag is a kind of paraffin type generated from source rock of the Eogene Liushagang Formation.The kerogen types are mixed ones.The oil threshold depthis 2400 m.

    CO2 GAS SEEPAGES OF ZEGULONG AREA,PINGYUAN COUNTY,GUANGDONG PROVINCE
    Dai Jinxing, Chen Xueliang, Zeng Guanyun
    1990, 11(2):  205-208.  doi:10.11743/ogg19900210
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    CO2 gas seepages near Zegulong Village,Pingyuan County,Guangdong,are distributed along Shaowu-Heyuan deep fault.δ13C-value is -3.39‰ to -4.79‰.The authors consider that the CO2 come from upper mantle.

    DISCOVERY OF UPPER CARBONIFEROUS TAIYUAN FORMATION CONODONTS IN XINGGONG-XINMI COAL FIELDS,WESTERN HENAN
    Zhang Nianmao
    1990, 11(2):  209-213.  doi:10.11743/ogg19900211
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    The conodont assemblage(Streptognathodus elongatus-S.gracilis-S.wabaunsensis)inTaiyuan Formation of Xinggong-Xinmi Coalfields is recognized for the first time in thispaper.As compared with the conodonts of the standard section in North China—theTaiyuan Formation in Xishan,Taiyuan,Shanxi Province,the Taiyuan Formation in thestudying area should belong to the middle to late stage of Late Carboniferous.

    HYDROCARBON ACCUMULATION FACTORS AND POOL TYPES IN NORTH SLOPE OF BIYANG DEPRESSION
    Qiu Ronghua
    1990, 11(2):  214-219.  doi:10.11743/ogg19900212
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    Biyang Depression covers an area of 1000 km2.Within it,530 km2 belongs to its north slope.The 4 oilfields discovered before 1985 are distributed in the south slope and the central deep subsided area.In recent years,5 oilfields have been discovered in the north slope,the prospected and controlled hydrocarbon reserves occupies above 40% ofthe total reserves of the depression,and this percentage may even rise as the explor ationcarrying on.Favourable conditions for hydrocarbon accumulation in the north slope are:1.Thesuccessional sedimentation-structure complex slopes are the target area for hydrocar bonmigration;2.Multiple sandbodies provide good reservoirs;3.A series of nose-structuresare in control of hydrocarbon accumulation;4.Two sets of faults provide the conditionof shelter for hydrocarbon accumulation;5.Cap rocks on regional unconformity makeswell preservation for shallow pools in slope.There are various kinds of oil pools,within which fault-nose,fault-block and uncon formity ones are the main types.