Table of Content

25 June 1982, Volume 3 Issue 2

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THE APPROXIMATE SOLUTIONS OF 1ST-ORDER REACTION EQUATION AND THEIR APPLICATION TO THE QUANTITATIVE PREDICTION OF OIL AND GAS

Yang Wenkuan

1982, 3(2):  99-112.  doi:10.11743/ogg19820201

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The thermal evolution of the carbon atoms which can gradually transmigrate from kerogen into bitumen and are called potential carbon or available carbon by the author is considered as an unimolecular 1st-order re-action.

A PRELIMINARY STUDY ON DIAPIRIC STRUCTURE IN OIL AND GAS—BEARING BASINS IN EASTERN CHINA

Fei Qi, Wang Xiepei

1982, 3(2):  113-123.  doi:10.11743/ogg19820202

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In the tectonic evolution of Meso-Cenozoic oil and gas-bearing basins in Eastern China,the diapirism,by which oil and gas structural traps are formed,are quite obvious.This paper will focus on the mechanism of salt and mud diapiric structural traps intruded at low temperature.In the meantime we will preliminarily probe the possibility of the existence of magmatic diapiric structures which are intruded at high temperature.It is emphasized that the distribution of soft mudstone are obviously much wider than that of salt and gypsum in the eastern basins of China,therefore,the diapirism of mudstone should be paid more attention to.

AN APPROACH TO GEOLOGICAL INTERPRETATION OF LANDSAT MULTISPECTRAL SCANNING IMAGES

Shao Zhen, Li Cuiying, Chen Zuyin, Zhong Youliang, Nie Jinzong

1982, 3(2):  124-134.  doi:10.11743/ogg19820203

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An attempt has been made at geological interpretation of the data of size able coverage areas obtained by Landsat by means of digital image processing and model identification.The method of non-supervise classification proposed in this study is essentially an improved variety of cluster algorithm.It is not only characterized by convenience rapidity and easier adaptation to minicomputer from the viewpoint of formation,disintegration and integration of initial condensation points,but also enhances the interactive function and makes the result of classification more satisfactory.The output result of classification displays the special distribution of soil types.Since the distribution of some soils corresponds to relative subsurface structures,a feasible approach is provided for geological interpretation of covered areas.

THE LATE PRECAMBRIAN TIDAL DEPOSITS IN NORTH CHINA PLATFORM

Chen Changmin, Chen Jingshan

1982, 3(2):  135-141.  doi:10.11743/ogg19820204

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The Late Precambriam tidal deposits are well developed and widely distributed in North China Platform.The major evidence of tidal sedimentation in these sediments includes herringbone cross bedding,lenticular beding,wavy bedding,flaser bedding,tidal channel-fill cross bedding,reactivation surfaces,various types of ripple marks and interference ripple marks,truncated ripple marks,washout structures,rill marks,mud cracks,and penecontemporaneous deformation structures.In addition,oolites,algae and stromatolites are very significant.The depositional sequences and models of clastic tidal flat,tidal-dominated delta,ferric algal flat and oolitic bank,and carbonate tidal flat(or platform)are discussed here.Four sketch map about these tidal deposits during the early and late Changchen(the Great Wall),the Jixian,and the Qingbaikou are also given.Finally,it is supposed that these tidal deposits were mainly formed in the epeiric seas on the platform margin.

ON THE PROBLEMS OF QUANTITATIVE EVALUTION OF SOURCE ROCKS——OPEN TO DISCUSSION WITH COMRADE LI

Huang Difan, Li Jinchao

1982, 3(2):  142-148.  doi:10.11743/ogg19820205

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Objection is lodged against the method used for calculating hydrocarbon production proposed in comrade Li's paper"A preliminary study of hydrocarbon production from various types of kerogen at different mature stage"(refer to"Oil & Gas Geology",Vol.2,No.3.).In this paper,a brief discussion is given on hydrocarbon productivity,its quantity from source rocks,its limit of cumulative hydrocarbon potential,as well as calculating method and related data etc.It is pointed out that not only Li's calculating method and result obtained are questionable,but also his basic data used for calculation are unreliable.The hydrocarbon productivity suggested in the paper is only the ratio of average hydrocarbon obtianed from kerogen elemental components.The author has suggested that calculating hydrocarbon must be based on its threshold.In addition,some concept has accordingly proposed for solving this important object in this study.

A BRIEF DISCUSSION ON OIL AND GAS POOLS IN WESTERN LIAOHE DEPRESSION AND THEIR REGULARITIES OF DISTRIBUTION

Wu Zhenlin

1982, 3(2):  149-157.  doi:10.11743/ogg19820206

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The western Liaohe depression began its developing at Oligocene and kept on sinking ever since.Now,the thickness of sediments with abundant organic matters reaches 5,000—6,000m.Because of the later Tertiary fracturings and foldings resulting from the progressive warping and epigenetic tectonic movements,sequences of source rocks and varieties of traps favourable to oil and gas generation and accumulation were formed.Four catigories of oil and gas pools are found,which are subdivided into nine types of different traps,such as:1).tectonic pools,including a).anticline;b).faulting blocks;and c).faulted structural noses;2).stratigraphycal pools,including d).overlaps;and e).uncomformities;3).basement pools,including f).latent ridges;and g).uncomformities of base-ment;and 4).lithological pools,including h).lenticular sandstones;and i).pinched layers.All these pools are regularly distributed in different parts,superimposing each other.They can be summarized as two series of oil and gas pools:1).anticlinal series and 2).slope series.They can be used as models for arranging exploration and appointing places favourable to oil and gas searching.The depression appears in shape of dustpan.Therefore,the oil and gas traps were formed in direction from margin to centre;whereas maturation of oil and gas began from central parts towards margin.This kind of relationship between tectonic and oil generation processes implies certain regularities of special distribution of oil and gas pools and can lead to discovering of possible pools in some places else.

LITHOLOGIC IDENTIFICATION OF CAMBRIAN AND ORDOVICIAN IN NORTH CHINA AND THEIR OIL POTENTIALS

An Taixiang, Wang Xinping, An Zuoxiang

1982, 3(2):  158-169.  doi:10.11743/ogg19820207

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There are many oil showings in Cambrian and Ordovician systems in North China,which have drawn the attention of petroleum geologists for years.In this paper,lithologic identification is made up of 8 formations:the Houjiashan Stage,the Mantou-Xuzhuang Stage,the Changxia Stage,the Upper Cambrian,the Lower Ordovician,the Lower Majiagou Stage,the Upper Majiagou Stage and the Fengfeng Stage.Based on formation thickness and paleontologic data,paleogeographic changes are reviewed.Marine transgression of limited extent took place along the depression zone in the inner flanks of the Inner Mongolia,the Jiaoliao and the Huaiyang oldlands during the Houjiashan age.Clastic rocks and mudstones were well developed at the outset.Till the Changxia age carbonate rocks began to be widespread.During the late Cambrian,dolomites occured progressively from the north and reached their greatest thickness to the south,accompanied by a gradual lowering of horizons.In the Early Ordovician,the southern boundary of the sea basin shifted northward,but it expanded again during the early Middle Ordovician,more dolomites among carbonates were deposited.Clay and gypsum beds became widespread during the late Middle Ordovician when the sea area being contracted.All the isopach contours extend in an E-W direction.

REVIEW AND DISCUSSION ON DISCOVERING OF JIANGHAN PETROLEUM PROVINCE

Lu Xichu

1982, 3(2):  170-176.  doi:10.11743/ogg19820208

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Most of the oil and gas reserves in Jianghan basin occurs in series of salt-lacustrine sediments deposided in a highly restricted rifting environment during the later Eogene.Their accumulation is governed both by sandstones derived from subaqueous alluvial fans at north part of the salt lake and halokinetic anticlines in a vortex structural system.This is a particular type different from any other reservoirs known.During exploration,the study of regional geology has played an important part in successful locating potential source sag and selecting main target bedds.But enough attention had not been paid to oil accumulation governed by lithofacies,and necessary means of exploration had been lacked,we had gone a wrong way for a period of time in predicting oil fields.However,as soon as the horizons of sandstones and composite components of structures necessary for oil accumulatoin have been identified,a series of oil fields which contain majority of oil reserves in the basin has been under way of discovering.According to the recognition summed up in this paper,some suggestions has been proposed for future prospecting.

THE FORAMINIFERAL FAUNAS OF THE LATER EARLY CARBONIFEROUS IN CENTRAL HUNAN AND THEIR STRATIGRAPHICAL SIGNIFICANCE

Qiu Songyu, Lin Jiaxing

1982, 3(2):  177-183.  doi:10.11743/ogg19820209

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In recent years,the writers have obtained a lot of foraminiferal fossils from the late Early Carboniferous(Datang Stage)in the Liangyuan-Shaoyang region of central Hunan Province and carried out a detailed stuty on them.Based on their character,3 foraminiferal assemblage zones can be established in an ascenting order:1.Dainella gumbeica-Plectogyra posneri assemblage zone;2.Eodiscus-Lituotubella glomospiroides assemblage zone;3.Endothyranopsis crassus-Archaediscus krestovnikovi assemblage zone.Among them,the,Zimenqiao Group is the representative deposit of Endothyranopsis crassus-Archaediscus krestovnikovi assemblage zone;the other two zones represent respectively the deposits of upper or lower part of Shidengzi Group(see fig.1).The foraminiferal of the Datang Stage shows obviously the aspect of the later Early Garboniferous System and is similar to that of the Visean Stage in Moscow Basin of Soviet Union.It should be stressed that the Shidengzi Group is not only a comparatively favorable reservior rocks,but also a fine source rocks.In addition,the coalbearing beds of Ceshui Group and the gypsiferous beds of Zimenqioa Group are excellent covers.Therefore,in comparison with the other conditions as concerning the combination of source-reservior-cap rocks in present region,the Datang Stage should be a considerably favorable oil & gas bearing beds.

AN GEOLOGICAL OUTLINE OF ISLANDS AND SEDIMENTARY BASINS IN EASTERN SEAS OF CHINA

Ding Peimin

1982, 3(2):  184-190.  doi:10.11743/ogg19820210

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Thousands of islands are scattered around in the Yellow and East China Seas,comprising Changshang Island in the north,the Southern Penghu Islands in the south and Diaoyu Dao in the east.Rock outcrops in these islands,which constitute basements of sedimentary basins,play an important part in their development.The Yellow Sea basin,with Meso-Cenozoic sediments of 6,000m thick,contains source rocks and several dozens of tectonic traps favourable to oil and gas accumulation.Being centrolled by tectonic system,it has undergone two stages of development,i.e.the early fault-bound depression and the later regional depression,both accompanied by sedimentation.The East China Sea basin,being filled with Cenozoic sediments of 10,000m thick,is rich in organic matters brought into the basin by the Yangtze and other rivers,and complicated by clusters of enormous juxtaposed tectonic belt and zones,becomes most potential for oil and gas exploration.The basin is a back-arc one,its origin and development are controlled in some extent by the interaction between the Pacific and Eurasia plates.