1991 Vol. 13, No. 2

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ON THE RELATIONSHIP OF THE INTRAPLATE DEFORMATION AND THE SECONDARY FORMATION OF OIL/GAS POOLS——THE GENERAL REGULARITIES OF THE OIL/GAS FORMATION IN MARINE ENVIRONMENT OF THE YANGTZE AREA
Sun Zhaocai, Qiu Yunyu, Guo Zhengwu
1991, 13(2): 107-142. doi: 10.11781/sysydz199102107
Abstract:
A systematic theory centred by the linkage of intraplate deformation and the secondary formation of oil/gas pools in later stages is proposed through the "7th Five Year National Plan Project" OIL/GAS ASSESSMENT AND GEOLOGICAL STUDIES THROUGHOUT THE YANGTZE AREA. It consists of the following principals: 1. Under the guidance of the mobilism as the fundamental recent geo-science, the evolution models of the geodynamics throughout both the Yangtze Area and completed geological history have been established. Based on the analysis of the severe tectonic reworks by intra-continental mountain-chain buildings of the area in details, the stable regions such as the Sichuan, Central Hubei, Northern Jiangsu-Southern Yellow Sea, have been suggested as the favourable areas for oil/gas exploration. 2. As viewed from plate boundary and unhomogeneous lithsphere of the Yandtze Plate, a concept of "intracontinental mountain-chain" characterized intra-continental subductions has been put forward. This is a fold-thrusting zone with obvious orientations attributed to the orogenic system of the Tethys collisions and its front belt is the major play for oil/gas accumulation of the Yangtze Area. 3. Through the analysis of the typical oil/gas pools in the area, a concept of secondary formation of oil/gas pool is proposed with the following kernels: the phase transformation of oil/gas, solution-release and multiple sources for hydrocarbon. Therefore, the oil/gas prospects in the area have been defined unequivocally. 4. The assemplage of oil/gas pools in the area is outlined as the follows: effective oil/gas sources(S),reservior space(R), trap(T), seal(S), and the time(T)for oil/lgas formation. These understandings not only sum up the regularities of the formation for oil/gas pools in marine environment of the Yangtze Area, but also fill in gaps in the modes of consideration and methodology for oil/gas exploration in rather complex structural regions.
TECTONIC EVOLUTION AND OIL AND GAS POTENTIAL IN NORTHERN TARIM BASIN
Yang Fuzhong, Zhang Kai
1991, 13(2): 143-151. doi: 10.11781/sysydz199102143
Abstract:
The northern Tarim Basin has undergone 6 evolutionary phases since the middle Proterozoic:1)The development of Xinjiang paleoplate (Pt2-∈1); 2)The formation of the passive continental margin (∈2-O1); 3)The subduction of the Tarim paleoplate to the Yining-Middle Tianshan paleoplate (O2-C1); 4)The colliding foreland depression period(C2-P); 5)The depression period of colliding predmount(T-N1); 6)The colliding reactivated predmount depression(N2-Q). The northern Tarim Basin can be subdivded into 2 tectonic parts: i.e. the northern Tarim uplift belt and the Kuche-baicheng thrust fold belt. The former is a high basement uplift in which Paleozoic strata was erosed seriously, and ancient buried hills and anticlines were well developed. It is the most promising zone owing to its bordering on the Manjiaer and Ku-che oil generation depressions.The latter consists of a double-deck structure, the upper is characterized by a series of thrust faults and folds in the Meso-Cenozoic strata; the lower is made up of the Paleozoic strata. The sedimentary formation of the passive continental margin overridden by the south Tianshan nappe is important source rocks. Besides the oil-bearing Meso-Cenozoic strata, it is expected that there are a great amount of Paleozoic gas resources in this zone.
APPROACH OF THE GEOLOGIC TECTONIC CHARACTERISTICS IN HONG KONG-KOWLOON
Yan Kaijian
1991, 13(2): 152-157. doi: 10.11781/sysydz199102152
Abstract:
Hong Kong-KowLoon region is divided by Tolo Channel-Tsuen Wan fault zone into two parts-the south and north terranes. The north terrane has complicated structures, in which Paleozoic and Meso-Cenozoic strata crop out, and experienced the nappe compressions of SE-NW and N-S directions. The new and old geologic sheet-bodies of overlap appear broadly inverted succession, the dynamic metamorphism and deformation widely took place in pre early Cretaceous strata. North allochthone napped and docked into south autochthone along Tolo Channel-Tsuen wan fault, then resulted in a great number of the fenster and klippe associations, in last nappe activity. The nappe structural features with SE-NW trend consisting of Repulse Bay Formation klippe and mid-acid plutonic rock, and accompanied imbricate fault structures in south Tolo Channel-Tsuen Wan fully indicate that the autochthone of late nappe activity is also non-root allochthone in early period. The overlap of the north terrane surpass present position of Tolo Channel-Tsuen wan fault, therefore the actual front of the nappe would be in south Lautau Island klippe belonging to the north terrane formerly. The collision of the north terrane also has an intensive effect on underlying terrane, which give rise to a series of dome-shape and basin-shape structures in the position of tectonic syntaxis, such as the Tuen Mun and ShaTin-KowLoon dome-shape antiform in the same EW belt,the Lautau Island and HongKong Island (south) basin-shape synforms etc. The nappe activity With NW trend took place in K2-E.The nappe structure features with EW trend not only destroys the structure features with NE trend but also have an effect on E stratum. The southward nappe activity might occurin E2 or QP.
STUDY OF GLASTIC-COQUINA DIAGNESIS AND FLUID ENCLOSURE IN DAANZHAI MEMBER OF JURASSIC, NORTHERN SICHUAN
Chen Rpnglin, Li Xianxiang
1991, 13(2): 158-163. doi: 10.11781/sysydz199102158
Abstract:
In the Paper, the study of clastic-coquina diagnesis in Daanzhai Member of Jurassic of Northern Sichuan is taken as an example. With the application of fluid enclosure data, the temperature range resulted in diagnesis can be determined; on the basis of which the stages of diagnesis may be distinguished, and the time when the diagnesis occurred and palaegeothermal history as a function of sedimentary history can also be predicted. The direction and the dating of hydrocarbon migration will be determined by a preliminary study of a few hydrocarbon-bearing enclosures.
STUDY OF ORGANIC MACERALS IN EOGENE SOURCE ROCKS IN XIHU AND OUJIANG DEPRESSIONS OF EAST CHINA SEA SHELF BASIN
Ou Lexian, Zhu Xiaojing
1991, 13(2): 164-174. doi: 10.11781/sysydz199102164
Abstract:
The organic macerals from Eogene source rocks in Xihu and Oujiang Depressions are studied in the paper, using reflected light and reflected flourescent light, and it is suggested that the source materials dominated by lignin and cellulose in the area mainly derived from terrestrial higher plants.The degradation products of amorphous lignin and cellulose in kerogen of mudstone are the characteristic compositions of the area. The coal samples containing higher lipitinite from Pinghu Formation of Xihu depression are of source rocks that should not be underestimated. Futhermore, the classifications of sourc rocks for the study area are made according to the characteristics of macerals, and the relation to hydrocarbons is approached.
1991, 13(2): 175-178. doi: 10.11781/sysydz199102175
Abstract:
1991, 13(2): 179-184. doi: 10.11781/sysydz199102179
Abstract:
MICROPALAEONTOLOGICAL ASSEMBLAGES IN SONGNAN WELL NO.15 AND STRATIGRAPHICAL SIGNIFICANCE
Qiu Songyu
1991, 13(2): 185-199. doi: 10.11781/sysydz199102185
Abstract:
In recent year, the author has obtained a lot of sporopollen, Charaphy-ta, and Ostracoda from the first member of Nenjiang Formation and the Qi-ngshankou Formation in Songnan Well No.15 located in the Huaide County, Jilin Province, and carried out a detailed study on them.Among the fossils, the sporo-pollens are especially rich, which may be divided into an assemlage sub/one and an assemblage zone, in ascending order as follows: l.Schizaeoisporites-Tricolporopollenites assemblage zone 2.Proteacidites-Schizaeoisporites assemblage subzone The first member of Nenjiang Formation is the representative strata of Proteacidites-Schizaeoisporites assemblage subzone.The Schizaeoisporites-Tricolporopollenites assemblage zone represents the strasa of the Qingshan-kou Formation.The two sporo-pollen assemblages provided the reliable bi-ostratigraphical basis for dividing and correlation of strata and distinguishing the suite of seismic reflection wave, on which the strata in Songnan Well No.15 were redivided and the suite of seismic reflection waves was revised(see table 2).