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    25 September 1984, Volume 5 Issue 3
    NEAR-SURFACE DIAGENESIS OF PELLET-OOLITIC LIMESTONE OF JIALINGJIANG FORMATION IN SOUTHERN SICHUAN
    Zhao Xiafei
    1984, 5(3):  195-203.  doi:10.11743/ogg19840301
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    The most significant event in the diagenetic history of the carbonate rocks for the 1st and 2nd Members of Triassic Jialingjiang Formation in southern Sichuan might be the dissolution and infilling of carbonate grains in synsedi-mentary and early diagenetic stages.Whenever the carbonate sediments were stationed above sea level,the ool-pellet banks were drenched by meteoric water,the aragonite and high-Mg calcite constituting inner part of the grains were dissolved resulting in the appearance of dissolution hole inside the grains.Later,the underground water-table elevated,the lower holes within freshwater phreatic zone would be fully filled with freshwater calcite,and the upper dissolved holes still in the upper phreatic and vadose zone were only locally and partially filled with freshwater calcites.Then,new ooid and pellet carbonate layer was sedimented upon the previous bank while it was submerged under sea level.Again and again,these courses repeated in cycles,and so,a great deal of layers of the dissolvedholes remained so far in the section of Jialingjiang Formation.Consequently,la-yers of dissolved holes and its local distribution of mica-like calcite in the dis-solved holes might be a diagnostic feature of vadose zone or upper phreatic zone,and a textural set of dissolution and infilling of ooides and pellets represents a hiatus of sedimentation.As for oil and gas reservoirs,the most significant pore type of the 1st and 2nd Members of Jialingjiang Formation is the dissolved holes of ooid and pellet and that of the dedolomitized dolomites,the primary intergranular holes are of second importance,pores inside bioclasts and between crystals are almost negligible,while the existence of bitumen is harmful due to its role in blockage.

    UPGRADING EXPLORATION EFFECTS BASED ON COMPREHENSIVE STUDY OF SEISMIC INFORMATION IN HUANGHUA DEPRESSION
    Yang Huanran
    1984, 5(3):  204-210.  doi:10.11743/ogg19840302
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    Effectiveness of exploration for petroleum in Huanghua depression,Baohai-bay basin,is increased through comprehensive study of seismic and drillling infor-mation in conjunction with sedimentary environments,structural traps,detection of hydrocarbon and seismic modelling.Some new oil-fields are therefore to be found out,and geological reserve has been increased.

    A STUDY OF δ13C,δ34S AND δD OF CRUDE OILS
    Fan Pu, George E. Claypool
    1984, 5(3):  211-217.  doi:10.11743/ogg19840303
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    The enrichments of δ13C,δ34S and δD in crude oils gathered in various places,both in China and abroad,are studied and reported in this paper.For oils formed in salt lakes,their δ13C ranges from-24.70‰ to-28.30‰,averaging-25.86‰,δ34S from 12.30‰ to 1.00‰,averaging 7.57‰,and δDranges from-148‰ to-98‰,averaging-135.40‰.For oils formed in freshto brackish lakes,δ13C ranges from-24.61‰ to-29.60‰,averaging-27.49‰,δ34S from 17.02‰ to 4.51‰,averaging 10.48‰,and δD from-161‰ to-137‰,averaging-146.89‰.The enrichments of δ13C,δ34S and δD from salt lake oils and marine oils have some similarities.They are probably reflecting the primary types of organic matter as well as depositional environments,and may be influenced in some extent by the maturity of crude oil.

    ON THE PETROLEUM GEOLOGICAL FEATURES OF TERTIARY HALF-GRABEN IN EASTERN CHINA
    Tong Xiaoguang
    1984, 5(3):  218-227.  doi:10.11743/ogg19840304
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    Tertiary basins in Eastern China are mostly consisted of half-grabens,each of them can be subdivided into three tectonic zones,i.e.escarpment,deep sub-sidence and shallow slope.Along the slope,there are many faults varying in strikes and dips,formed at different times.Normal faults which dip antithetic to the basement(Pre-Tertiary)surface are often accompanied by draping structures,other swhich dip in the same direction as the basement are commonly accompanied by reverse drag structures.Up dip of the slope,sediments in the basin become progressively thin,with overlap,offlap and unconformity quite developed.Sand bodies often pinch out in various directions toward argillaceous rocks.In res-ponse to the not deeply buried basements connected with antithetic normal faults as shown in Fig.1 of this paper,stair-faulted blocks were formed,and inevitablly,structural,stratigraphic-lithologic traps are well developed along slope zones constituting an important oil and gas zone.Ten types of oil/gas pools are revealed,they are related to reverse drag structures,drape structures,faulted blocks,stratigraphic overlaps,stratigraphic uncomformities,buried hills,updip pinch-out of sandstones,fault-truncated sandstones,sandstone lens and proper carbonates.Types and enrichment of petroleum depend mainly on features of the slope.They are divided into three types according to their sedimentary blanket andtimes of formation,namely:稤epositional slope,the slope status of its basement exists prior to its suc-cessively overlapping sedimentary blanket.稴tructural slope,the tilting of its basement occurred after the sedimentation of its blanket,the thickness of the later is therefore almost uniform.稴edimento-structural slope,the basement surface tilted originally,but the filting strengthens gradually during the sedimentation of its blanket,within the later,onlap,offlap and erosion surfaces are common. Among them,the latter is of greater importance and possesses most of pool-types.

    THE DISCOVERY OF ZOOPHYCUS IN CHINA AND ITS ENVIRONMENTAL SIGNIFICANCE
    Yang Shipu
    1984, 5(3):  228-235.  doi:10.11743/ogg19840305
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    Trace fossil Zoophycus is widely distributed in shallow marine limestones of the Datang Fm of Lower Carboniferous in southern China,and the Middle Carboniferous Benxi Group and the Upper Carboniferous Taiyuan Group in northern China.Study of Zoophycus is of great importance for understanding environments of coal formation,they are often found in Carboniferous sediments of the Yangtze and Sino-Korea platforms,belonging to shallower marine environment.In this paper,4 ichnosp.of Zoophycus were described.They are Zoophycussp.1 from Lower Carboniferous,Zoophycus sp.2 and Zoophycus(palaeospira)wudaensis Yang ichnosp,nov.from Upper Carboniferous.

    SEDIMENTATION OF ANCIENT FAN-DELTAS IN EASTERN CHINA
    Gu Jiayu
    1984, 5(3):  236-245.  doi:10.11743/ogg19840306
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    Characteristics of lacustrine fan-deltas generally are as follows:1)Fan-deltas have steeper slope(average gradient of 0.6-15‰),but cover-ing smaller area;2)Texturally and mineralogically,fan-deltaic deposits are less mature and more coarse-grained,reflecting proximity to source areas;3)Fan-deltas have well-developed subaqueous distributary channels,but with little or poor-developed subaerial alluvial plain;4)Fan-deltaic deposits are often associated with the turbiditic deposits.According to features of ancient lacustrine fan-deltas in the eastern part of China,fan-deltaic system can be divided into seven sub-facies.1)Distributary channel sediments:they are developed within the upper part of fan-deltaic sequence.The depositional conditions are changed frequently because of the progradation of intermittent river-borne sediments directly into standing lake basin.These sediments are similar to those of braided rivers,with poor-sorted and immature sediments dominated by gravel and gravelly sands,cemented bymud,and grading upward into normal rhythms of fine-grained material.2)Interfan-mush sediments:they are poorly developed,comprised predomi-nately of silts and mud,sometimes intercalated with fine-grained gypsum and salts,poor bedding for bioturbation.3)Subaqueous distributary channel sediments:these constitute an important element in the fan-deltaic system.Their features of deposition are similar to those of braided rivers,but the uppermost mud is often absent because of later current erosion or reworking by waves.The probability cumulative curves of these sedi-ments show three populations,of which the traction population occupies 0-30%,saltation population 40-93%,while the suspension population occupies 10-20%.4)Subaqueous inter-distributary channel sediments:these sediments are dis-tributed aside from the subdistributary channels often reworked by waves or re-moved by currents along shore area.They are composed generally of fine-grained sands and silts,interbeded with mud characterized by flaser and convolute bed-dings,with normal or reverse rhythms.5)River mouth bars:sand bodies are mainly composed of well-sorted medium-grained sands,fine-grained sands and silts characterized by cross,hori-zontal,flaser and lenticular beddings with reverse rhythms.Sometimes deforma-tion layering and bioturbation structures can be seen in silty clays.6)Delta-front sheet sands.7)Prodeltaic mud.Fan-deltaic depositional models may serve as valuable tools for searching economic mineral deposits and fossil fuels.

    PORE STRUCTURE AND ITS ORIGIN IN THE THIRD MEMBER OF HETAOYUAN FORMATION IN SHUANGHE OILFIELD
    Di Shixiang, Wu Pin, Li Jianwu
    1984, 5(3):  246-252.  doi:10.11743/ogg19840307
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    The 3rd Member of Hetaoyuan Fm constituting the reservoir of the Shuanghe Oilfield in the Biyang depression is represented by coarse clastics from rapid deposition.Pore spaces developed here are mainly of intergranular and corrosive types,and porosity in matrix is rare.There are four grades of pore space,from good to bad,as defind in this paper.However,majority of these pore spaces is of the good ones.The pore structure of reservoir is clearly improved due to the extensive development of secondary corrosive pore spaces.The development of secondary porosity is related both to rapid accumulation,poor maturity and lower compaction caused by earlier calcareous infilling andsubsequent cementation,and to the generation of water and carbon dioxde insource rocks during formation of hydrocarbons,These source rocks being coex-isted and interfingered with reservoirs contain mainly transitional types of kero-gen within a depth favourable to oil and gas generation,so the water and carbon dioxide generated inevitably would react with the early infilled carbonates and other minerals in adjacent reservoir rocks resulting in greater amount of secondary porosity.The development of the secondary porosity might also related to the structure of coarse grained rocks of the reservoir proper.

    APPLICATION OF DIPMETER LOGGING FOR STUDY OF GEOLOGICAL STRUCTURES
    He Dengchun, Tian Hong, Luo Dashan
    1984, 5(3):  253-259.  doi:10.11743/ogg19840308
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    Methodology and experiences are described for using dipmeter logging to examine the attitude of geological formations,types of faults and angular unconformities.Practice in Huanghua depression has proved that this log is a useful tool for study of geological structures.

    THE PETROLEUM POTENTIAL OF MIOCENE SERIES IN THE SOUTHWEST PART OF TARIM BASIN
    Zhou Yongchang, Qiu Dongzhou, Wang Yunlong
    1984, 5(3):  261-270.  doi:10.11743/ogg19840309
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    The Miocene is represented by clastics and argillaceous rocks intercalated with evaporites totalling 1,000—6,050m thick and is divided from bottom to top into Keziloi Fm,Anquan Fm and Pakabulake Fm.Lacustrine sediments of the Miocene are quite well developed.Among the others,the marine transgressive lacustrine facies of the bathyal Anquan Fm is the most developed,while the deltaic,fluvial and alluvial-fan facies,as well as the turbiditic facies of the Pakabulake Fm are also developed.The Anquan Fm formed in hemi-deep lacustrine area is the main source rock in upper Tertiary.Source rocks confined to thickness no less than 150m has an area about 17,000km2,while its total volume is up to 10,000km3.The lower part of the Pakabulake Fm is the most important target formation,in which commercial oil and gas of Kekeya oilfield have been found.Therefore,the Miocene rocks exhibit good conditions for looking both for Petroleum generated and accumulated in situ,and for petroleum generated within older source rocks but accumulated in newer reservoirs.Preliminary study demonstrates that the Kashi and the Yecheng areas can be considered as the first grade of target areas,the Maigaiti slope and thewestern uplift zone of Shache County are of second grade and the area south of the Mazatake line is of the third grade,while the Kezikealte fracture zone might be favourable in searching for oil and gas related to overthrusting.

    FEATURES OF PETROLEUM GEOLOGY IN QIJIA DEPRESSION,SONGLIAO BASIN
    Wang Hengjian
    1984, 5(3):  271-275.  doi:10.11743/ogg19840310
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    Rushing out firstly the oil flow off the wellhead from the delta-front sandbodies of Qingshankou Group,give rise to a new ground for exploration activties in Qijia depression,Songliao basin.Qijia depression measures about 2,000 km2 situated between Daqing anteclise and Taikong uplift.Its structures are quite simple,in addition to some faults,the positive structures are mainly anticlinal noses and mid-depression ridges,with 8 small anticlines found during detailed seismic examination.In this region,the lithofacies of Qingshankou and Yaojia Fms are complex.Deposition occurred mainly in transitional fluvio-lacustrine zone,therefore,a great many of sand-bodies were formed with different size and morphology.Under the control of above conditions,the main trap-types are supposed to be stratigraphic and composite stratigraphic-structural ones which may hold the larger part of poten-tial reserves.Now,the oil-gas exploration are well underway on a large scale.

    THE PETROLEUM POTENTIAL OF THREE MAJOR DEPRESSIONS IN TARIM BASIN
    Zhou Chaoji, Jiang Jianheng
    1984, 5(3):  277-284.  doi:10.11743/ogg19840311
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    In this paper,the writers point out that the development of stratigraphy and the tectonic characteristics of the Kashi subdepression,Yecheng subdepression and Maikaiti slope of southwestern depression of Tarim basin are controlled by the compressive and compresso-shaer stresses exerted from Tianshan and Kulun Mts.Secondary petroleum traps as Kekeya oilfield in Kashi and Yecheng subdepressions may be found in Neogene which measures 8,000—10,000mthick and various subtle faults developed below it are favourable in the forming of these traps.After a comprehensive study,the authors proposed that structures in the 2nd row from south of the Yecheng and Kashi subdepressions and Mai-kaiti Slope are more promising in petroleum prospecting.The Kuqa depression is formed mainly by Mesozoic differential block fault-ing and is filled with a series of coal seams and petroleum-generation source rocks.The Cenozoic compressive stress exerted from Tianshan Mt.gave rise to varietyof tectonic features and discordance between Mesozoic and Cenozoic groups.Because of the absence of good Cenozoic source rock and the existence of unpermeable salt rocks at the bottom of it,the exploration work should mainly be carried out in the north of Changmzituk fault within areas where Mesozoic rocks are well developed.Structures within the 2nd and 3rd rows from north and the footwall of the huge nappe of North Bygulu in the northern margin of this depression are also prospecting.Geologically the research level of east Tarim basin is rather low,but it has a broad area and its source rock of Triasic-Jurasic is believed thicker than the previous depressions,therefore,it would be proved abundant in oil and gas.

    SOME KNOWLEDGE AND ASSESSMENT OF GUIZHOU PETROLEUM PROSPECTING
    Liu Xiang
    1984, 5(3):  285-296.  doi:10.11743/ogg19840312
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    Guizhou is representative of those provinces in southern China where oil and gas reservoirs related to Palaeozoic marine carbonates might take place.Prospecting work for oil and gas has been carried out for 28 Nears since 1956.To summarize achievements obtained in these years,the author has analized both positive and negative conditions for oil prospecting.In view of geotectonic and paleogeographic conditions,Guizhou Province obviously has better struc-tural traps,and good source rocks which should be quite productive and could provide great amount of petroleum.However,it has also some negative factors,such as strong crustal disturbance,uplifting and folding occurred in the later stage of geological history,and resulting in sebsequent intensive erosion and extra exposure of target formations,besides of aged source rocks and extraor-dinary maturity of organic substance as well as poor time conjunction of oil generation with formation of structural traps.Therefore,discovery of commer-cial oil reservoirs could hardly be expected;however,it is still prospective to find some gas fields.While analizing experiences obtained in searchingfor oil and gas,the author suggested that:1)plans should be worked out based on the petroleum geology of the target area proper,and no experiences introduced from abroad could be used stiffly;2)local experience should be used only in combination with the regional ones,pay more attention to fundamental geological wo,no need to be eager for success,and do not treat the complicated problem of petroleum geology in an isolated and one-sided attitude;3)grass-roots unit of geological administration should be established according to the natural geological unit,neither to have its functioning at the limitation of province and such political boundary nor operating changefully;4)different specialities should work jointly with their techniques being continually renewed.Finally,the author has made some recommendations about plans of explora-tion task from now on.

    PROF.XIE JIARONG AND ENERGY GEOLOGY IN CHINA
    An Yankai
    1984, 5(3):  297-299.  doi:10.11743/ogg19840313
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    Professor Xie Jiarong(1896—1966),a famous geologist of China,was graduated from the Geological Institute,Ministry of Agriculture and Trade in 1916,then 1920—1922 studied in the Wisconsin University,USA,and 1929—1930 worked on coal petrology in Germany.He was the head of the Qingyuan Fuel Division,National Geological Survey, and the director of the Peiping Geological Survey.He was promoted professor and the geological department head of Peijing University,assigned to a post of chief of the Mineral Explor-ation Division and also was appointed chief geologist of the Ministry of Geo-logy.He was elected president of the 10th council of the Geological Society of China,editor in chief for GEOLOGICAL REVIEW and a member of the Earth Science Division,Academia Sinica.He made a great contribution to energy geology.Prof.Xie was a pioneer of petroleum geology in China.Since 1921 he had made an extensive geological investigation on petroleum in Gansu,Shanxi,Guangxi,Sichuan and Hebei and published 27 papers on petroleum geology and a volume of PAPERS ON PETROLEUM GEOLOGY(1957).He expounded his views on the characteristics of petroleum geology of China and made important proposals for petroleum prospecting and prospective evaluation,He was one of the leading members for the first national mineral prospecting campaign in the fifties and made a great contribution to the discovery of the Daqing and North China oilfields.Prof.Xie was also a pioneer of coal geology and a founder of coal petrology in China.From his 44 related contributions,12 dealt with coal petrology.He was engaged in coal petrology in early years and discovered a new kind of coal in China.The discovery of Bagongshan coal mine in Huainan,Anhui Province,was an outstanding contribution to coal geology.

    A REVIEW OF EVOLUTION AND HYDROCARBON GENERATION MECHANISM OF TERRESTRIAL ORGANIC MATTER
    Fu Jiamo
    1984, 5(3):  302-303.  doi:10.11743/ogg19840315
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    The scientific monograph mentioned above with 203 pages,123 figures and 16 plates written by the senior research fellow Huang Difan et al.of the Scien-tific Research Institute of Petroleum Exploration and Development,Beijing is recently published by the Petroleum Industry Press.In this book,the writers have deeply discussed the kernel problems such as the evolution of continental organic matter and its mechanism of hydrocarbon generation.Based on the simulating tests and plentiful data made by various modern experimental technology,they have summed up on a molecule and con-figuration level the results of geochemistry research of the institute in recent years.The type and its evolution characteristics of the organic matter in various mature stage,the biogenetic substances of hydrocarbon,the biomarker,the evolution model and mechanism of hydrocarbon generation of various organic matter have been discussed;some new ideas,such as the X-shaped diagram of kerogen pyrolysis classification,the relationship between the threshold of principal oil generation zone and the molecule parameters of sterane and terpane have been presented.The authors conclude in this book that the distributions of semi-deep and deep lacustrine facies developed in deep depression and its inheritance in geo-logical history are the essential requirements for petroleum generation in con-tinental sediments.The monograph is essentially a summary of their own research,the enor-mous excellent work made by other geochemists in China are less concerned.