1984 Vol. 6, No. 1

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SEISMIC REFLECTION CHARACTERISTICS OF SUBTLE TRAPS IN PETROLIFEROUS BASINS IN EASTERN CHINA AND THE EXPLORATION TECHNIQUE APPLIED
Yuan Bingheng, Lin Liang
1984, 6(1): 1-8. doi: 10.11781/sysydz198401001
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On the basis of the seismic data available, this paper introduces the seismic characteristics of various subtle traps in eastern China and makes a preliminary approach to their distribution regularity and the related seismic exploration technique. It is proposed that these subtle traps can be divided into nine kinds of four types according to their seismic characteristics. The horizontal and vertical distribution patterns of various subtle traps are discussed in this paper. It is accepted that most of these subtle traps are distributed along four kinds of zone, i.e., the erosional unconformity zone, the overlap unconformity zone, the pinch lithological zone and the major fault zone. It is advisable to predict and search for subtle traps along these zones from now on.
LITHOFACIES AND PALEOGEOGRAPHY OF THE LATE CRETACEOUS——PALEOGENE OF THE TARIM PLATFORM
Yong Tianshou
1984, 6(1): 9-17. doi: 10.11781/sysydz198401009
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During late Cretaceous the Tarim platform was divided roughly into three zones. They were the eastern Tarim depositional zone, the Kepin-Bachu erosion zone and the western Tarim depositional zone. This framework of the paleogeography of the Tarim platform was essentially kept on in Paleogene. The marine upper Cretaceous-lower Tertiary systems of the western Tarim depositional zone were foundamentally of supratidal and intertidal facies. These facies zones were not favourable for generating oil. The promising sections for oil generation were as follows: upper and medium Kukebai formation, Yigeziya formation, lower Qimgen formation, Karatar formation and lower Uragen formation. The organic matter in these formations is of sapropel type. They are regarded as poor source rocks according to various oil generation indicators.
DISCUSSION ON SLIDING FLOW OF CARBONATE AND ITS DEPOSITIONAL CHARACTERISTICS
Wang Yigang
1984, 6(1): 18-23. doi: 10.11781/sysydz198401018
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There develops a suit of conglomeratic carbonate sediments of gravitational flow origin in the slope facies zone of the early Triassic from southern Guizhou to western Guangxi. This kind of sediments contains a little calcareous clay matrix and pressolution phenomena are developed among the gravels. The sorting of the gravels is poor and the grains are orientationally arranged indicating sliding sedimentation. Judging from the facts observed in the fields and the results of laboratory experiments, we come to a conclusion that this kind of sediments must be resulted from massive flow caused by the sliding among gravels owing to the "lubricating and resistance reducing" effects of the small amount of calcareous mud matrix. On this basis, it is inferred as sediments of sliding flow and a preliminary study has been made on the origin and the supporting mechanism of the sliding flow. This paper also proposes that the carbonate sediments of sliding flow is a special indicator of carbonate slope facies.
DISCUSSION ON THE SEDIMENTARY ENVIRONMENT OF THE CARBONATE OF PALEOGENE YUANJIANG FORMATION IN THE DONGTING DEPRESSION
Cao Shuyun
1984, 6(1): 24-31. doi: 10.11781/sysydz198401024
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Microfossils of Ortonella,Hedstromia, Bevocastria, Cayeuxia, Sepulidea and Foraminifera and Foraminifera-like are fouad in carbonate samples from the Yuan Jiang formation of the Dongting depression for the first time. According to the characteristics of the carbonate, it is believed that sea water transgressed from the northeastern and northern parts of the Dongting depression during Paleogene. This brought the depression an environment of brackish water linking with the maritime basins. On this basis, the oil prospects of each part of the Dongting depression are discussed.
ON THE SUBDIVISION AND CORRELATION OF THE CRETACEOUS SYSTEM OF SANSHUI BASIN OF GUANGDONG
Zhang Xianqiu
1984, 6(1): 32-40. doi: 10.11781/sysydz198401032
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Subdivision and correlation of the Cretaceous system of Sanshui basin are made through paleontological study on over 60 wells. The lower Cretaceous is called the Baihe formation. This formation is determined as of late Early Cretaceous (Aptian-Albian) according to the research on fossils of the plants, sporo-pollen and Charophyta. The upper Cretaceous can be divided into Sanshui formation and Dalang-shan formation. The fossil therein can be correlated with the typical sections (the Nanxiong formation and the Pingling member of Shanghu formation) of the upper Cretaceous in China. The Sanshui formation are comparable with the middle and lower parts of the Nanxiong formation. Their age is determined to be the early-middle stage of Late Cretaceous, whereas the Dalangshan formasion is comparable with the upper part of the Nanxiong formation and the lower part of the Shanghu formation, their age being considered to be the late stage of Late Cretaceous.
DISCUSSION ON PRIMARY MIGRATION OF HYDROCARBONS
Li Mingcheng
1984, 6(1): 41-47. doi: 10.11781/sysydz198401041
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In general, capillary is a resistance to primary migration of hydrocarbons. Only under certain conditions can capillary pressure be effective. As regards the closed regime of capillary, gas is more easily sealed than oil. Migration stage changes with hydrocarbon generation stage. In fact, there is no fixed migration stage. It is better to make use of compaction curve in combination with geochemistry data to define the migration stage. Compaction and abnormal highpressure are closely related to each other. During migration of petroleum an important role is assigned to geopres-sure. But in practice, how to correctly understand this role and how to judge from the compaction curve stilll remain unsolved.
1984, 6(1): 47-47. doi: 10.11781/sysydz198401047
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COMPOSITIONS OF THE THERMO-DEGRADATIONAL PRODUCTS OF OIL SHALE AND LOW RANK COAL KEROGEN AND THEIR GEOCHEMICAL SIGNIFICANCE
Zhang Dajiang, Huang Difan, Ge Xiuli, Li Jinchao
1984, 6(1): 48-60. doi: 10.11781/sysydz198401048
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This paper deals with the study on kerogen using Py-GC method. Samples were heated to 500℃ rapidly and stayed for 10 minutes. All the thermo-degradational products were collected and analysed on a Varian-3700 Gas Chromatograph. The components determined were classified into normal alkane, normal alkene, isoprenoid alkane, isoprenoid al-kene and alkyl benzenes (naphthalene) and so on. After analyzing and comparing components of thermo-degradational products of two low rank coal kerogens and two oil shales, reliable informations on the composition of precursors, organic type, maturity and sedimentary environment of organic matter in source rocks study are acquired.
1984, 6(1): 61-66. doi: 10.11781/sysydz198401061
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RICHNESS OF ORGANIC MATTER AND ITS EVOLUTIONAL CHARACTERISTICS IN CARBONATE SOURCE ROCKS
Hao Shisheng
1984, 6(1): 67-71. doi: 10.11781/sysydz198401067
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For a long time, there is an argument about the lower limit of the richness of organic matter for a carbonate to be source rocks. It is a key problem in evaluating oil and gas prospects in carbonate rock area. However, the richness indicators for carbonate source rocks used in China are set on lower levels. Based on a preliminary study on the richness and loss of organic carbon during thermal evolution, considering the difference of diagenesis between shales and carbonate rocks, it is suitable to take 0.3-0.5% as the lower limit of organic carbon and 100 ppm or more as that of hydrocarbon content. Thermal simulation experiments on several samples showed that the threshold of carbonate source rocks is at about 420℃, but the lower limit is at 470℃ which was acquired from the maximum pyrolysls temperature. The experiment also shows that the hydrocarbon content decreases with thermal evolution and 8-9% organic carbon was lost during the whole maturation stage. Organic carbon loss increased to 16% In the mid-period of overmaturation stage and 20% at the later stage.
1984, 6(1): 72-75. doi: 10.11781/sysydz198401072
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1984, 6(1): 76-77. doi: 10.11781/sysydz198401076
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1984, 6(1): 78-80. doi: 10.11781/sysydz198401078
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1984, 6(1): 81-83. doi: 10.11781/sysydz198401081
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1984, 6(1): 84-84. doi: 10.11781/sysydz198401084
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1984, 6(1): 85-85. doi: 10.11781/sysydz198401085
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1984, 6(1): 86-86. doi: 10.11781/sysydz198401086
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