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    25 June 1987, Volume 8 Issue 2
    A PRELIMINARY APPROACH ON GROWTH THRUST FAULT BELTS AND THEIR OIL AND GAS EXPLORATION
    Wu Qingfu
    1987, 8(2):  119-125.  doi:10.11743/ogg19870201
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    The growth thrust fault belts discussed in this paper are referred to as the thrust belts that are situated between the fold mountains around the compressive basins and marginal depressions of inland basins and regional thrust belts within the basins as boundary of the secondary structural units in West China. The evolution of this kind of thrust faults may be divided into 3 stages: 1. Early upthrusting stage with the upper wall as the active one; 2. Con-temporanous sliding stage with the bottom wall as the active one; 3. Upwardsgrowing stage dominated by diffefential sedimentation. These stages can be taken as a complete evolution cycle of the faults, and complicated thrust belts may be resulted from multicycles. Oil and gas exploration in the thrust belts needs a lot of money, and is fullof risks. Only subterranean thrust belts which are associated with oil-generation depression or which intensely thrusted at the early stage but weakened down at the late stage can be taken as exploration target.

    ON CARBONIFEROUS CHRONOSTRATIGRAPHIC SYSTEM IN CHINA
    Zhang Zuqi
    1987, 8(2):  126-137.  doi:10.11743/ogg19870202
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    At the present age, the concept that the Carboniferous bas two-fold division character. e.g., it has been subdivided into the Mississipian System and the Pennsylvanian System in North America and the Dinantian Subsystem and the Silesian Subsystem in West Europe. has been spreaded widely. But in my opinion, this two-fold division character is mainly the difference of sedimentary character, the boundary between them is a tectonic-facies one, but not a boundary of important development stage of organic world, nor does it coincide with a major change event of geomagnetic polarity. Therefore, they are not chronostratigraphic units, but just lithostratigraphic ones. The same "two-fold division" concept has different boundaries in North America and WestEurope. this is a good evidence. Now a new Carboniferous chronostratigra-phic system which differs from the ones proposed by A. Bouroz et al. (1977)and adopted by W. B. Harland et al. (1982) and by H. R. Lane et al. (1985)has been established by the author in this paper based on the development stage of many kinds of organisms seen in the continuous marine sections and also the paleomagnetic data (see Tab. 1 in the Chinese text). Because the bottom of the Asselian stage (Pseudoschwagerina zone) does not coincides neither with the significant development stage of any kind of organism. nor with the geomagnetic polarity change event, moreover, in the vast area of East, Europe. the Asselian strata generally over lap on the olderones of different ages with angular unconformities. So it is not suitable to take it as the Carboniferous-Permian boundary. Now the bottom of Montiparus (or Obsoletes) zone is proposed instead of it, because this boundary corresponds with the important development stage of many kinds of organisms which includes fusulinids, ammonoids, conodonts, brachiopods, plants, etc., it also coincide sroughly with the major change epoch of geomagnetic polarity in 295 Ma.B. Runnegar (1984) pointed out that Glossopteris, Gangamopteris and Eurydesma appeared almost synchronously about 290 Ma ago, an event which is taken to mark the beginning of the Permian in the Gondwanan Realm. Therefore, it seems that this boundary is an ideal all-global united boundary reflecting simul-taneously a great geohistorical development stage in the Laurasia and the Gondwana continental blocks. Three clear development stages of many kind of organisms may be foundin the continuous Carboniferous marine sections, so it is appropriate to divide the Carboniferous System into three series. The Lower Carboniferous Series includes the stratigraphic category from the bottom of Gattendorfia (≈CystophrentisSiphonodella sulcata) zone till first ap-pearance of fusulinids (Dainella-Pseudoendothyra-Eostaffella primitive fusulinid fauna). In China, it includes the Gelaohoan stage and the Liujiatangian stage. The Middle Carboniferous Serics includes the stratigraphic category from the appearance of fusulinids till disappearance of Gigantoproductidae-Striati-feridae-Daviesiellidae fauna or the top of Eumorphoceras zone. In China. itincludes the Xincunian stage, the Liannanian stage, the Shangsian stage andthe Dewuan stage. The Upper Carboniferous Series includes the stratigraphic category from the disappearance of Gigantoproductidae-Striatiferidae-Daviesiellidae fauna orthe bottom of Homoceras zone till the appearance of fusulinids with spiro-thecal keriotheca(i.e.,the bottom of Montiparus or Obsoletes zone).In China, it includes the Huashihban stage and the Dalan stage. The above-mentioned every "stage" represents respectively a specific development stage with distinctive characters in regional geology of China. Their standard fossil assemblages and the correlations of the strata have been given in Tab. 2 in Chinese text.

    APPLICATION OF TRACE ELEMENTS IN OIL SOURCE CORRELATION OF BAXIAN SAG
    Ding Zhimin
    1987, 8(2):  138-144.  doi:10.11743/ogg19870204
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    The emission spectra were used to determine the abundances of 18 trace elements contained in 75 crude oil samples and 360 source-rock samples from six strata of the Ordovician. Permo-Carboniferous and Paleogene of the Baxian Sag of the Jizhong Depression, Hebei Province, and 14 abundance ratios are calculated by the author. Based on these data, this paper made an oil-oil correlationby cluster analysis and established a discriminant funtion of source rocks by dis-criminant analysis, and made an oil-source rock correlation by secondary discri-minant analysis. The result shows that the Tertiary crude oil comes from Eogene source rocks; the Permo-Carboniferous condensate and light oil are from C-P coalseries; a part of Ordovician light oil is from C-P source rocks and the rest arefrom the Eogene.

    STUDY ON THE RESERVOIR POROSITY IN MESOZOIC LAMPROPHYRIC INTRUSIVE BODY, YIBEI OIL FIELD
    Zhou Zili
    1987, 8(2):  145-152.  doi:10.11743/ogg19870205
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    A rare oil pool of Mesozoic lamprophyric intrusive body has been found on the Yihezhuang Uplift in the Chezhen Depression, North Shandong. This paper deals with the origin and distribution of porosity in the particular reser-voir rocks. The study made by means of maay petrological methods shows that: 1. The lamprophyric reservoir rocks are characterized by rich intracrystal porosity of augite and hornblende, clearly different from ordinary sedimentary reservoir rocks; 2. The porosity (5.2-25.2%) and the permeability (0.12-30 mD) are higher than that of the top and bottom sand stone reservoir rocks; 3. The secondary porosity was formed in the course of deep buried stage andthe acid organic solution came from adjacent organic rich source rocks of the Lower Tettiary (short distance migration); 4. The tectonic fractures have provided favourable passage for the migration of acid organic solution and oil; 5. The rapit evolution that started from the generation of organic solvent to hydrocarbon maturation associated with adequate fluid flux is another favour-able condition for the formation of secondary porosity. The periphery of the oil generation depression and the uplift within it are favourable targets for oil exploration when their basement faults are connected with the depression and various rocks there have fractures and easily disso-luting component.

    SCREENING OF BIOMARKER INDICES BY GENERALIZED CORRESPONDENCE ANALYSIS——DISCUSSION ON CRUDE OIL MATURITY OF JIYANG DFPRESSION
    Zhou Guangjia
    1987, 8(2):  153-162.  doi:10.11743/ogg19870207
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    Based on the data of 30 biomarker indices of 39 crude oil samples and 29 source rock samples collected in the Jiyang Depression,Huabei Basin, the author screened these indices by generalized correspondence analysis. It is suggested that the 5α-C27 Sterane ββ/(αα+ββ) and 5α-C29 Sterane 20S/(20R+20S)are the main indices of crude oil maturity, while the relative abundance of rearranged Sterane, 4-methylsterane and Tm/Ts are of secondary importance.

    EVOLUTION OF PLATE TECTONICS OF THE NORTHEASTERN JUNGGAR BASIN AND ITS CONTROL OVER OIL AND GAS
    Xu Weixin, Zhang Kai, Gao Mingyuan, Yao Huijun
    1987, 8(2):  163-170.  doi:10.11743/ogg19870208
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    The Junggar Basin is a large superimposed basin bated on a Pre-Cambrian massif. Since the Cambrian, the plate tectonic evolution of the northeastern Junggar Basin can be divided into 4 periods as follows: 1. The passive continental margin phase (Pz1); 2. The transform phase from passive continental margin to continental collision (D1-C1); 3. The collision foreland basin phase (C2-P1); 4. The down warping inland phase (P2-Q). The evolution of plate tectonics controlled the development of the sedimentary basin. Corresponding to the plate tectonic history, the northeastern Junggar Basin consisted of a miogeolinai prism (C-C1), a collision foreland basin(C2-C1),and a down warping basin (P2-Q) ect,. They gave abnudant organicmaterial for the formation of petroleum. The evolution of plate tectonics also controlled the geometric shape, the structure, the sedimentation and the thermal evolution of the basin, and so thus controlled the generation, migration aad accumulation of oil and gas.

    QUANTITATIVE LOG INTERPRETATION OF FRACTURE RESEKVOIR
    Tan Tingdong
    1987, 8(2):  171-176.  doi:10.11743/ogg19870210
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    This paper discusses the method for determining the porosity, water-saturation and permeability of the carbonate reservoir by log data. A cube model is used,so that the rock-blocks and fractures can be distinguished and get interpretation respectively.

    LOG CATEGORIES AND ENVIRONMENTAL INTERPRETATION——EXAMPLE WITH THE MAIN PETROLIFERONS SERIES OF THE OAOYOU SAO, NORTH JIANGSU
    Qiu Fukang, Zhang Guodong
    1987, 8(2):  177-188.  doi:10.11743/ogg19870211
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    To interprete sedimentary environment, it is necessary to master the three foundamental elements with marking features: amplitude, shape and assemnlage. Accondng to the analysis and comparison on the petroliferous series in the Gaoyou Depression, North Jiangsu, the curves' shape and sequence assem-blages of subaqueous alluvial fan, delta, fluvial and deep-water turbidite fan aresummarized as below: 1.Subaqueous alluvial fan: From bottom to top, SP appears to be a sequence assemblage changed from low-amplitude, serrated tank shape or positive serrated shape to middle-high amplitude serrated box shape or bell (funnel)shape to low-amplitude reverse serrated shape; R changes from dense serrated high resistance to serrated high-middle resistance and then disperse serrated middle-low resistance. 2.Delta: The logs of regressive constructive deltas show that the appears to be a sequence assemblage changing from smooth line associated with low-middle amplitude funnel shape to funnel, finger or box shapes of middle-high amplitude to box or bell shape of middle-high amplitude,and R is relatively low. 3.Fluvial: Land-based rivers are developed gradually from braid channels to meandering channels; SP shows shapes from box with fine sawtooth to bellor separated box to bell assemblage maintained by middle amplitude. R changes from serrated middle-high value to middle-lower value. 4.Deep-water turbidite fan: These curves are difficult to be distinguished from that of subaqueous alluvial fan, it is therefore necessary to see about its occurrence location.

    DISTRIBUTION REGULARITY AND EXPLORATION METHOD OF HYDROCARBON POOLS IN THE DAMINTUN SAG
    Huang Zhu'an
    1987, 8(2):  189-200.  doi:10.11743/ogg19870213
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    The Damintun Sag, situated in the Liaohe Valley of the north part or the Bohai Bay Basin, is a small oil-generation sag of the Meso-Cenozoic. It co-vers an area or 800km2. The greatest thickness of sedimental rocks is up to 6600m. Oil exploration was initiated in 1970. but once stopped due to the existence of the red bed on the basin bottom, the basalt within the basinand humic mother substance and high condensate point in the oil nature. Since 1981, we carried out a thoroughly comprehensive geological research for key problems which we have no knowledge of basement strucures,covering structures,the greatest thickness and the productivity of the high condensate oil by adopting new technique of the digital seismics and thermal recovery to reevaluateoil productivity and to choose the most favourable traps for prior drilling. As the result, high yield oil pools in a buried-hill were discovered. By means of tectonic geology and seismic stratigraphy, the sedimentary system ofthe main hydrocarbon-bearing formations as well as the assemblage and distribution regularity of complex pools were further known and Tertiary hydrocarbon resources were consecutively discovered. The source beds in the seg are the 3rd and 4th members of the Shahejie Formation, the reservoir rocks are carbonate rocks of the Proterozoic, andthe mixed rocks and granite gneiss of the Archaeozoic in the buried-hill, the sandstone of the 3rd member of the Shahejie Formation. The sag contains 3 secondary uplift and subsidence belts respectively, in which not only the up-lifts are oil-bearing, but also the subsidence belts contain either source beds or oil reservoirs. Therefore, in later belts, complex hydrocarbon pools will also be expected to be discovered.

    ON THE DEPOCENTER OF PETROLIFEROUS BASINS IN CHINA
    Wu Shoucheng
    1987, 8(2):  201-213.  doi:10.11743/ogg19870214
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    An attemps is made by the author on the basis of plate movement to studythe relations between subsidence, depositional-and oil-generation center. It issuggedted that: 1. The depocenter is controlled by the velocity and ratio of subsidence while the oil-generation center is controlled by organic matter and its thermo-maturity. 2. The depocenter is related to the system and classification of the basin,and has influence on the remigration of hydrocarbon. 3. The optimum period of the source beds for the tensile basins in East China must satisfy the boundary condition, that is to say, Vt≥3.5 Vs (here Vt issubsidending velocity,and Vs is depositing velocity);While for those compressivebasins in West China, it is important to find favourable sedimental facieszones and traps in wide synclines of nappes to the basins' boundaries. 4. The trace of depocenter in giant basins of the Chinese plate suggests that, (1) They have cyclicity (appeared as "O" or "S" shape); (2) There was differential before and after the Indosinian movement; (3) Different geological times have different development stages. 5. All the plates in China were connected as a whole in the Meso-Cenozoic,and the trace of the Mesozoic shows a left-lateral "O" style, but that the Cenozoic emerges a movement from west to east.

    GEOLOGICAL FEATURES OF CO2 POOL IN HVANGQIAO REGION, NORTH JIANGSU AND ITS GENESIS
    Cheng Shilin
    1987, 8(2):  214-218.  doi:10.11743/ogg19870215
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    Natural gas is discovered in 4 wells in Huangqiao region, north Jiangsu.The gas is composed mainly of CO2 with small amount of hydrocarbon, helium and argen. The δ13C-values of CO2 range from -5.88 to -2.874‰, and that of methane ranges from -40.10 to -37.643‰. The pool may propably be mixed one of multisource.

    MARKOV CHAIN SIMULATION ON FLYSCH RHYTHMIC SEQUENCES OF THE UPPER ORDOVICIAN IN WEST ZHEJIANG
    Lu Hongbo, Xia Bangdong
    1987, 8(2):  219-230.  doi:10.11743/ogg19870217
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    The Early Paleozoic sedimentary basin in western Zhejiang was a wedge-shaped basin with a total area of 2000 km2. In the Iater Ordovician, a flysch formation of 1000-2000 m thick developed in the basin. Based on the grain sizes of the sediments, patterns of beddings, bedding plane feature and grading. 8 states are selected. All data mentioned above are calculated by computer. The matrixes of frequency transition, probability transition, limit probability, replacement and fixed vectors and entropies are resulted respectively. The results show that the flysch basin in the western Zhejiang can be onviously divided into two logitudinal sedimental zones. the south east zone was a littoral area. and the north West zone was the axis of along and narrow basin. The hydrodynamic scele or the later was bigger andmore complicated than the tirst one. The entropy types and the projections of systematic entropy values have further improved the shallow-water origin of the flysch.