1981 Vol. 3, No. 4

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THE GEOCHEMICAL FEATURES OF OIL GENERATION IN DEVONIAN-CARBONIFEROUS OF XIANG-ZHONG DEPRESSION, HUNAN, AND THE DIRECTION IN OIL AND GAS EXPLORATION
Chen Zhengfu
1981, 3(4): 245-256. doi: 10.11781/sysydz198104245
Abstract:
Xiang-Zhong was an area of relatively stable and secular depression in Late paleozoic. It is thousands of metre thick with marine facies carbonate rocks as the bulk of the sedimentation which was possessed of certain oil forming geological conditions. In this paper, the abundance, type and evolution of organic matter are studied through the analysis of organic carbon,gaseous hydrocarbons, GR/G chloroform extracts, group compositon of the extracts, GC of saturated hydrocarbons, infrared and ultraviolet spectra of aromatic hydrocarbons; and the vitrinite reflectance, elemental composition, paramagnetic spectra,scanning electron microscopic observation thermal-thermogravimetric analysis of kerogen. Meanwhile, as well as computer simulation using the relationship of time versus temperature,the history of the formation of oil-gas is inferred.The basic suggestions are: The Middle Devonian Qiziqiao Formation and Lower Carboniferous of Xiang-Zhong depression; and the Upper Devonian Shetianqiao Formation of Xin Hua depression are the major horizons of oil generation. The evolution of oil-gas has reached a stage of overmature and the prospecting has to be focussed on natural gas. The Middle-Late Carboniferous and Permain were the main stage of oil formation. Around the episoda of the Indosinian movement there came the prosperous stage of the formation of natural gas. Therefore, the structure of early Indosinian and pre-Indosinian, and the Devonian-Carboniferous reef-bank facies provided favourable condition for forming pools. So, it should be a prior target for oil prospecting.
THE FORMING MECHANISM OF ZHUJIANGKOU BASIN
Jin Qinghuan
1981, 3(4): 257-263. doi: 10.11781/sysydz198104257
Abstract:
Zhoujiangkou basin was developed at the passive continental margin of South China.After the Middle and Late Eocene tectonic event, the basin underwent three evolution stages, i.e. fault down (rifting), warp down (subsidence) and depression. The basin has a tectonic pattern of south-north zonation(NEE trend) and east-west zonation (NE trend).The NE trending structure is formed under the tectonic regime of the early stage.While the NEE trending structure can be related to the north-south extention of South China Sea basin taking place about 32-17 million years ago. The intereaction of the two tectonic regimes created the inharmony between the NE trending structure on the land and the NEE trending structure of the sea area. The Zhujiangkou basin shows that the NEE newly formed structure superimposed on the NE trending inherited structure. The compression occurring in the lower part of the crust caused the extension of the upper part, and made the Zhoujiangkou a great basin. The Moho raised obviously, and a "converted image" is formed with convex at the bottom and hollow at the top. The characteristics of the local structures within the basin depended on the intensity of the movements and their time spans. Zhoujiangkou basin not only possesses some favourable conditions such as large area,thick sediments,and well developed local structure, but also has a rather high geothermal gradient and a rather low intensity in tectonic movement,favouring oil generation and accumulation. Therefore, Zhonjiangkou basin has a bright prospect in oil finding.
A PRELIMINARY DISCUSSION ON SECONDARY PETROLEUM GENERATION IN THE CARBONIFEROUS OF SOUTHWESTERN TARIUM BASIN
Zhou Xingxi, Yuan Rong
1981, 3(4): 264-273. doi: 10.11781/sysydz198104264
Abstract:
Based on studies of the burial depth and the history of thermal variation of the Carboniferous in Tarium Basin, the present paper indicates that there was possibility of secondary petroleum generation in the carboniferous of the basin. The author suggest that oil reservoirs originated from the carboniferous may, in all probabilites, be found in the area, if only enough organic matter was preserved in the carboniferous, i.e,it was located in the so-called "preservation window", at the end of the variacian movement and prio to the uplift, and was present in "oil-gas window" at the time of or after the formation of structural framework. Moreover, in the light of the history of the structural of evolution of the basin, the time of formation of structures of various stages of the basin is analysed and the hydrocarbon potentiality of the area assessed.
CHARACTERISTICS OF THE EVOLUTION OF PERMIAN OIL AND GAS OF SOUTHERN HUBEI
Ma Zuozhun
1981, 3(4): 274-281. doi: 10.11781/sysydz198104274
Abstract:
The Permian of Southern Hubei as a possible source rock is discussed in the light of sedimental environments and geochemical criteria. Based on the various criteria of hydrocarbon evolution such as burial depth, geothermal gradient, change of abundance of OM with depths, characteristic feature of DTA curve of kerogen, colour of conodonts, carbon isotope ratios of natural gases, etc. The evolution of OM in the Permian is discussed and divided into three substages, Late stage, last stage and last-destroyed stage. Hence an assessment of the oil and gas prospects of the Permian in Southern Hubei is made.
1981, 3(4): 282-284. doi: 10.11781/sysydz198104282
Abstract:
AN APPROCH ON GEOLOGICAL CONDITIONS OF THERMOGENIC GAS IN THE DONGMING DEPRESSION AND IT’S GEOCHEMICAL MARKERS
Huang Jingcheng
1981, 3(4): 285-292. doi: 10.11781/sysydz198104285
Abstract:
This paper describes the geological distribution and the burial depth of Carboniferous and Permian coal beds in the Dongming depression and points out that the coalification has reached a higher degree so that the coal series have become an important source rock of thermo-genic gas. The analytical reasults of the geological conditions for gas accumulation and preservation shows that the Dongming depression is a favorable area for prospecting thermogenic gas. A gas deposit was discovered in Wen-Liu anticline in the north of the depression. The gas is produced from the fouth number of the Sha-hejie Formation.The data of stable carbon isotopic composition of the gas indicate that the type of organic matter in its source rock is humus. The gas was derived from the Carboniferous and Permian coal series. This example shows clearly that there exists thermogenic gas in the depression. Nitrogen occurring within sedimentary rocks in the depression seems to have something to do with the thermogenic gas. This paper also points out the favorable structures for prospecting thermogenic gas.
CLASSIFICATION AND EVALUATION OF SANDSTONE RESERVOIR
Wang Yuncheng, Yang Baoxing, Huang Yangzhou
1981, 3(4): 293-298. doi: 10.11781/sysydz198104293
Abstract:
This paper briefly describes the pore types of sandstone reservoir which are located in some regions of China.Then, according to the pore type and pore-size distribution data, the sandstone reservoirs are classified and evaluated with repect to oil production capacity.Studies indicates that sandstone reservoir in China can roughly be divided into three categories: (i) Sandstones which mainly involves intergranular pores and dissolved corrosion pores possess good physical properties. Their capillary pressure curves show rough-skewness and well sorting, their natural production capacities are high; (ii) Sandstones which mainly involves micropores, interstitial pores and cement intercrystal pores in matrix possess poor to medium physical properties. Their capillary pressure curves show fine-skewness and poorly sorting, so they have only medium to low natural production capacities; (iii) Sandstone reservoir loses its commercial value when its radius of an essential part of pore-throat-size are smaller than 0.68 micrometre.Table of classification and evaluation is listed in this paper. Unquestionably, it gives petroleum geologists much convenience for accelerating the discovery of benifitial accumulation zone in benifitial lithofacies zones.
STUDIES ON THE COMBINATIVE FORM OF KEROGEN WITH PYRITE AND THE SEPERATION OF FeSO4 AND Fe2(SO4)3
Zhu Meiqian
1981, 3(4): 299-306. doi: 10.11781/sysydz198104299
Abstract:
In this paper, the combinative form of kerogen with pyrite are observed and studied under scanning electron microscope. Experiments of the seperation of FeSO4 and Fe2(SO4)3 were carried out. The experiment indicated that the effect of the seperation is closely related to the combinative form of pyrite.
APPLICATION OF INFRARED SPECTROPHOTOMETRY IN STUDYING THE EVOLUTION OF KEROGEN
Zhou Xuanmi, Chen Meiqian, He Zhigao
1981, 3(4): 307-316. doi: 10.11781/sysydz198104307
Abstract:
The main points in this paper are: 1. The influences of various ratios of pyrite, quartz, kaolin, and reagent treatments of NaBH4, HF, HCl on the IR spectra of kerogen are studied. 2. The IR spectrum data of pyrolysis simulation of kerogen are studied. 3. A synthetical appraise of the changes of 1700cm-1/1600cm-1, and 2900cm-1/2000cm-1 in IR spectra together with their significance and applicable range are made. 4. A new Index——The shifting rule of bands of aromatic ring is proposed. Along with the increase of the evolution of kerogen, the bands of aromatic ring skeleton vibration of 1600cm-1 shifts regularly toward low wavenumber.This Index is suitable for comparing highly mature kerogen. Therefore it has great significance in study of Paleozoic carbonate rocks which are widely spread in China. Meanwhile the method of wavenumber shift is meaningful in developing the application of infrared spectrophotometry in petroleum geochemistry.
1981, 3(4): 317-319. doi: 10.11781/sysydz198104317
Abstract: