1996 Vol. 14, No. S1
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Display Method:
1996, 14(S1): 1-9.
Abstract:
The comprehensive studies on the sedimentary settings in the Jungger Basin, Tarim Basin and etc. show clearly that northwestern region of China was mainly marine sedimentary ronments, the basements of sedimentary basins were a number of ancient separated crystallinemassifs covered by sea water in the Palaeozoic, among which there were palaeo-ocean troughs or narrow palaereocean troughs. The marginal basins located along the trough between different massifs or the marginal zone between massifs and ocean troughs are favorable for oil andgas generation. DUring the mountain-building process with the compressional folding to the ocean trough, the ancient system of massif-trough transformed from the Palaeozoic marine environments to the Meso-Cenozoic continental sedimentary system of mountain-basin, during this time the ancient series of marine source rocks that deposited in the marginal basins were buried beneath the mountains around the basins, while oil and gas generating from the source rocks have partly migrated and accumulated into reservoir beds in the basins to form an oil and gaspool focalled the "out-generating and inner-reserving". Within this kind of basins, there coexist two series of source rocks: marine one and continental one, and two kinds of petroleum generating and reserving complexes: "inner generating-inner reserving" and "out generatinginner reserving". This new theory or model of petroleum formation and occurrence has been proved not only by the result of our recent petroleum geochemical research but also by the practice of exploration in some regions. The idea about petroleum generation from massiftrough's marginal zone has broken the traditional concept by which the formation and occurrence of the Palaeozoic petroleum only within modern basins, this could increase the potential of discovered petroleum resources and enlarge new fields for finding oils and gases in Northwest China.
The comprehensive studies on the sedimentary settings in the Jungger Basin, Tarim Basin and etc. show clearly that northwestern region of China was mainly marine sedimentary ronments, the basements of sedimentary basins were a number of ancient separated crystallinemassifs covered by sea water in the Palaeozoic, among which there were palaeo-ocean troughs or narrow palaereocean troughs. The marginal basins located along the trough between different massifs or the marginal zone between massifs and ocean troughs are favorable for oil andgas generation. DUring the mountain-building process with the compressional folding to the ocean trough, the ancient system of massif-trough transformed from the Palaeozoic marine environments to the Meso-Cenozoic continental sedimentary system of mountain-basin, during this time the ancient series of marine source rocks that deposited in the marginal basins were buried beneath the mountains around the basins, while oil and gas generating from the source rocks have partly migrated and accumulated into reservoir beds in the basins to form an oil and gaspool focalled the "out-generating and inner-reserving". Within this kind of basins, there coexist two series of source rocks: marine one and continental one, and two kinds of petroleum generating and reserving complexes: "inner generating-inner reserving" and "out generatinginner reserving". This new theory or model of petroleum formation and occurrence has been proved not only by the result of our recent petroleum geochemical research but also by the practice of exploration in some regions. The idea about petroleum generation from massiftrough's marginal zone has broken the traditional concept by which the formation and occurrence of the Palaeozoic petroleum only within modern basins, this could increase the potential of discovered petroleum resources and enlarge new fields for finding oils and gases in Northwest China.
1996, 14(S1): 18-24.
Abstract:
The formation of carbonate sequences is mainly controlled by the sea level change and subsidence of basement. Accordingly, we can construct a theoretical model (process model) to simulate the response of sedimentation at different sites on a shallow carbonate platform under the conditions of different sea-level changes and different subsidence rates of basement, so that we can understand the interaction among the factors affecting the formation of carbonate sequences. We can get some important conclusions from simulations. Under the premise of the definite subsidence rate of basement, the formation of carbonate sequences is controlled by sealevel change, and the sensitivity of its response to sea-level change decreases with water depth, so the meter-scale carbonate cycles forming on the different settings can not be compared with each other simply. The reflection of a third-order sea-level change cycle in geologic record is quite different on different depositional settings. Under the deep water, the relative water depth will show continuously falling, and under the shallow water, rising. So, if we want to construct a relative sea-level change curve about the whole basin or the globe depending on outerop or boring sections, we have to select proper sections where the relative sea-level change can be recognized from the geologic record, otherwise the comparison of relative sea-level changes will be impossible. The amplitude of the third-order sea-level change also affects the sequence, and the carbonate strata with high-frequent forth or fifth-order cycles certainly develop under the conditions of middle to low amplitude of the third-order sea-level change. If the third-order sequence is nearly symmetric, it is certain that the subsidence rate is very low, so the nearly symmetric third-order sequence is a token of a craton basin.
The formation of carbonate sequences is mainly controlled by the sea level change and subsidence of basement. Accordingly, we can construct a theoretical model (process model) to simulate the response of sedimentation at different sites on a shallow carbonate platform under the conditions of different sea-level changes and different subsidence rates of basement, so that we can understand the interaction among the factors affecting the formation of carbonate sequences. We can get some important conclusions from simulations. Under the premise of the definite subsidence rate of basement, the formation of carbonate sequences is controlled by sealevel change, and the sensitivity of its response to sea-level change decreases with water depth, so the meter-scale carbonate cycles forming on the different settings can not be compared with each other simply. The reflection of a third-order sea-level change cycle in geologic record is quite different on different depositional settings. Under the deep water, the relative water depth will show continuously falling, and under the shallow water, rising. So, if we want to construct a relative sea-level change curve about the whole basin or the globe depending on outerop or boring sections, we have to select proper sections where the relative sea-level change can be recognized from the geologic record, otherwise the comparison of relative sea-level changes will be impossible. The amplitude of the third-order sea-level change also affects the sequence, and the carbonate strata with high-frequent forth or fifth-order cycles certainly develop under the conditions of middle to low amplitude of the third-order sea-level change. If the third-order sequence is nearly symmetric, it is certain that the subsidence rate is very low, so the nearly symmetric third-order sequence is a token of a craton basin.
1996, 14(S1): 33-37.
Abstract:
Relations between sedimentology and stratigraphy, sedimentology and sequence stratigraphy, sequence stratigraphy and cyclostratigraphy are discussed with the principles of sedimentology being highly emphasized. Four types of equence boundaries are recognized. Hence, a sequence is defined as a series of genetically closely related sedimentary rocks formed in a longterm (third-or forth-order) transgrassive-regrassive cycle. Any rock surface between two different lithofacies which represent two slow long-term different transgrassive-regrassive cycles can be regarded as the sequence boundary. Sequence, stratigraphy, cyclostratigraphy, lithostratigraphy, biostratigraphy and etc. must be crossreferred.
Relations between sedimentology and stratigraphy, sedimentology and sequence stratigraphy, sequence stratigraphy and cyclostratigraphy are discussed with the principles of sedimentology being highly emphasized. Four types of equence boundaries are recognized. Hence, a sequence is defined as a series of genetically closely related sedimentary rocks formed in a longterm (third-or forth-order) transgrassive-regrassive cycle. Any rock surface between two different lithofacies which represent two slow long-term different transgrassive-regrassive cycles can be regarded as the sequence boundary. Sequence, stratigraphy, cyclostratigraphy, lithostratigraphy, biostratigraphy and etc. must be crossreferred.
1996, 14(S1): 49-56.
Abstract:
Bioherm sedimentary strutures were well-developed in sedimentary sequences of Middle -Late Cambrian in North China Platform. Bioherm-building organisms include cryptalgae,calcareous algae and non-algae multicelluar organisms which constutited simple type of thrombolite bioherm and composite five types of cryptalgalaminates: wave semispheroidal stromatolites bioherm (Ⅰ), wave-stacked semispheroidal stromatolites-Renalcis bioherm (Ⅱ),Epiphyton-columnar stromatolites bioherm(Ⅲ), wave-stromeatolites-EpiphytonGirvanella-columnar stromatolites bioherm (Ⅳ) and columnar stromatolites-crinoidea-sponge -wave stromatolites bioherm (Ⅴ). The complexity and diversity of bioherms indicate that bioherms can be formed in a wide area from tidal flat to deeper slope.The development process of bioherms underwent four stages: (1) basic stage; (2) pioneering stage; (3) flourishing stage and (d) decaying stage. Each stage was controlled by the relative sea-level changes which controlled the size of bioherms, organism components, inner structures and growing period.Study of sequence stratigraphy showed that most bioherm flourishing periods in the research area are the Gushan and Changshan stages, and bioherms are distributed in the early high system tract in the third-orde cyclic sequence. Bioherm types also change regularly in a sequence, for example, the composite types of Ⅴ, Ⅳ,Ⅲ, Ⅱ and simple type are successively well-developed from the bottom to the top in the sequence Ⅳ of the Dingjiatan section, Beijing west hills and in the sequence Ⅲ of the Xuankongshi section, Hunyuan County, Shanxi Province, This regularity is the products of the different stages of the third-order sea-level changes.The study on the distribution characteristics of bioherms, tempesitites and the research of glanconitic condensed section stated clearly that the latitude zone of Qinhuangdao-Tangshan (Hebei Provence)-Beijing West Hills-Datong (Shanxi Province) was a typical open middle shelf depositional environment in Late Cambrian. The depth was 40-80 meters. South of the zone was a wide inner-shelf belt, and north of the zone was a narrow outer-shelf environment. The conclusion provided the basic framework and important reference for studying the paleogeographic and sea-level changes.
Bioherm sedimentary strutures were well-developed in sedimentary sequences of Middle -Late Cambrian in North China Platform. Bioherm-building organisms include cryptalgae,calcareous algae and non-algae multicelluar organisms which constutited simple type of thrombolite bioherm and composite five types of cryptalgalaminates: wave semispheroidal stromatolites bioherm (Ⅰ), wave-stacked semispheroidal stromatolites-Renalcis bioherm (Ⅱ),Epiphyton-columnar stromatolites bioherm(Ⅲ), wave-stromeatolites-EpiphytonGirvanella-columnar stromatolites bioherm (Ⅳ) and columnar stromatolites-crinoidea-sponge -wave stromatolites bioherm (Ⅴ). The complexity and diversity of bioherms indicate that bioherms can be formed in a wide area from tidal flat to deeper slope.The development process of bioherms underwent four stages: (1) basic stage; (2) pioneering stage; (3) flourishing stage and (d) decaying stage. Each stage was controlled by the relative sea-level changes which controlled the size of bioherms, organism components, inner structures and growing period.Study of sequence stratigraphy showed that most bioherm flourishing periods in the research area are the Gushan and Changshan stages, and bioherms are distributed in the early high system tract in the third-orde cyclic sequence. Bioherm types also change regularly in a sequence, for example, the composite types of Ⅴ, Ⅳ,Ⅲ, Ⅱ and simple type are successively well-developed from the bottom to the top in the sequence Ⅳ of the Dingjiatan section, Beijing west hills and in the sequence Ⅲ of the Xuankongshi section, Hunyuan County, Shanxi Province, This regularity is the products of the different stages of the third-order sea-level changes.The study on the distribution characteristics of bioherms, tempesitites and the research of glanconitic condensed section stated clearly that the latitude zone of Qinhuangdao-Tangshan (Hebei Provence)-Beijing West Hills-Datong (Shanxi Province) was a typical open middle shelf depositional environment in Late Cambrian. The depth was 40-80 meters. South of the zone was a wide inner-shelf belt, and north of the zone was a narrow outer-shelf environment. The conclusion provided the basic framework and important reference for studying the paleogeographic and sea-level changes.
Mixed siliciclastic-Carbonate Sediments during the Lower-Middle Cambrian in the North China Platform
1996, 14(S1): 63-74.
Abstract:
Mixed siliciclastic-carbonate deposits from the Mandouian Formation to the Xuzhuangian Formation during the Early-Middle Cambrian in the North China Platform were interbeds of siliciclastic and carbonate rocks with high frenquency and mixed sediments with both siliciclastic and carbonate components. The former indicated interbeds of the mudstone and dolostone or the grainstone and silty shale, the latter formed the argillaceous dolostone, dolomitic mudstone, quartz calcarenite etc.The study on geochemistry of elements indicated the content of calcium gradually increased from the Mandouian to Xuzhuangian Formation with the increasing of limestone. But the content of magnesium decreased gradually with the decreasing of dolostone. Mg/Ca ratios were higher in Mandouianu Formation than in Maozhuangian and Xuzhuangian Formation.The content of trace element Sr was higher in limestone, 150-300×10-6 ;medium in argillaceous limestone, 100 ×10-6±;lower in argillaceous dolostone, mudstone and silty shale, 100 × 10-6. Sr/Ba1 in limestone, 1 in most mudstone and argillaceous dolostone. Mn=4000-13000 ×10-6in limestone,2500 ×10-6 in dolostone, 1000 × 10-6 in mudstone and argillaceous dolostone. The contents of Ti, Cr, Ni, V and etc. were higher in mudstone and silty shale, medium in argillaceous dolostone and dolostone, lower in limestone.The stable carbon and oxygen isotopic data of carbonate rocks indicated that the variant scale of isotopic values was greater in the Mandouian and in the lower part of Maozhuangian Formation, δ13C: - 2. 59‰─+1.14‰ (PDB) and δ18O:-14. 89‰── 4. 71‰ (PDB); while they were smaller in the upper part of Maozhuangian and in the Xuzhuangian Formation, ─2.25‰──0. 37‰ (PDB),─ 10. 07‰── 7. 95‰ (PDB) respectively. It could be deduced that the sea water was relatively shallow during the Mandouian and the early Maozhuangianstage,thus minor scale sea level changes could cause the changes of salinity, reduction-oxdation conditions, temperature and circulation of sedimentary environment, till the late Maozhuangian and Xuzhuangian, the sea water became relatively deep and sedimentary environment was stable.It was considered that transgression expanded gradually from the Early to Middle Cambrian in the North China Platform. The terrigenous deposits and dolostone decreased but limestone deposits increased from the Mandouian to Xuzhuangian. During Mandouian the transgressive cycles were deposits of parasyngenetic dolostone and regressive cycles were mud deposits, from Maozhuangian to Xuzhuangian the transgressive cycles were grainstone and regressive cycles were silty shales. The third sea level changes showed a model of rapid transgression and slow regression.
Mixed siliciclastic-carbonate deposits from the Mandouian Formation to the Xuzhuangian Formation during the Early-Middle Cambrian in the North China Platform were interbeds of siliciclastic and carbonate rocks with high frenquency and mixed sediments with both siliciclastic and carbonate components. The former indicated interbeds of the mudstone and dolostone or the grainstone and silty shale, the latter formed the argillaceous dolostone, dolomitic mudstone, quartz calcarenite etc.The study on geochemistry of elements indicated the content of calcium gradually increased from the Mandouian to Xuzhuangian Formation with the increasing of limestone. But the content of magnesium decreased gradually with the decreasing of dolostone. Mg/Ca ratios were higher in Mandouianu Formation than in Maozhuangian and Xuzhuangian Formation.The content of trace element Sr was higher in limestone, 150-300×10-6 ;medium in argillaceous limestone, 100 ×10-6±;lower in argillaceous dolostone, mudstone and silty shale, 100 × 10-6. Sr/Ba1 in limestone, 1 in most mudstone and argillaceous dolostone. Mn=4000-13000 ×10-6in limestone,2500 ×10-6 in dolostone, 1000 × 10-6 in mudstone and argillaceous dolostone. The contents of Ti, Cr, Ni, V and etc. were higher in mudstone and silty shale, medium in argillaceous dolostone and dolostone, lower in limestone.The stable carbon and oxygen isotopic data of carbonate rocks indicated that the variant scale of isotopic values was greater in the Mandouian and in the lower part of Maozhuangian Formation, δ13C: - 2. 59‰─+1.14‰ (PDB) and δ18O:-14. 89‰── 4. 71‰ (PDB); while they were smaller in the upper part of Maozhuangian and in the Xuzhuangian Formation, ─2.25‰──0. 37‰ (PDB),─ 10. 07‰── 7. 95‰ (PDB) respectively. It could be deduced that the sea water was relatively shallow during the Mandouian and the early Maozhuangianstage,thus minor scale sea level changes could cause the changes of salinity, reduction-oxdation conditions, temperature and circulation of sedimentary environment, till the late Maozhuangian and Xuzhuangian, the sea water became relatively deep and sedimentary environment was stable.It was considered that transgression expanded gradually from the Early to Middle Cambrian in the North China Platform. The terrigenous deposits and dolostone decreased but limestone deposits increased from the Mandouian to Xuzhuangian. During Mandouian the transgressive cycles were deposits of parasyngenetic dolostone and regressive cycles were mud deposits, from Maozhuangian to Xuzhuangian the transgressive cycles were grainstone and regressive cycles were silty shales. The third sea level changes showed a model of rapid transgression and slow regression.
1996, 14(S1): 84-89.
Abstract:
Reseach on the alteration process and precipated products of feldspar from elastic rock in Tarim Basin was carried out by the way of scanning electron microscope and energy spectrum analyzed. The results show that there are two alteration ways of feldspar in the acid medium.The products are Kaolinite and authentic quartz when the porosity and Permeability of elastic rock is high, and in this case, the alkaline ions (K+, Na+ ) precipated from feldspar are carried away easily. Contrarily, the products are illite and smetite when the porosity and Permeability is lower. Especially, study on the alteration proceder of K-feldspar and it's products was carried out in this paper.
Reseach on the alteration process and precipated products of feldspar from elastic rock in Tarim Basin was carried out by the way of scanning electron microscope and energy spectrum analyzed. The results show that there are two alteration ways of feldspar in the acid medium.The products are Kaolinite and authentic quartz when the porosity and Permeability of elastic rock is high, and in this case, the alkaline ions (K+, Na+ ) precipated from feldspar are carried away easily. Contrarily, the products are illite and smetite when the porosity and Permeability is lower. Especially, study on the alteration proceder of K-feldspar and it's products was carried out in this paper.
1996, 14(S1): 100-106.
Abstract:
Pyrolysis was done by two methods, the Y series of experiments showed the process of comprehensive original organic matter evolved and the Z series showed the process of only kerogen evolved. The comprehensive original organic matter was composed of non-kerogen matter and kerogen, so based on the two series of experiments we can study deeply how triterpenoids are generated and how they change.From the result of pyrolysis, this paper showed the differences between the comprehensive original organtic matter generated from both non-kerogen matter and kerogen and from only kerogen, and approached geochemical significance of the triterpenoids.The comprehensive original organic matter generated much more pentacyclic triterpenoids than kerogen did, so most pentacyclic triterpenoids were yielded by the non-kerogen matter.In Z series, there were no 8, 14-secohopanes, it's clear that the kerogen didn't yield 8, 14secohopanes. In Y zeries, when the temperature was 400℃, the pentacyclic triterponoids disappeared but 8, 14-secohopanes remained and were abundant, so the pentacyclic triterpanoids changed into 8, 14-secohopanes in high temperature.Hopanes, hopenes and 8, 14-secohopanes are all able to indicate maturity. At 250℃ hopenes were very abundant, but at 300℃ they disappeared, so they can indicate immaturity.Biohopanes are instable, too, when it was 350℃ they disappeared, so they can indicate lowmaturity. Three hopanes parameters and two 8, 14-secohopane ones were calculated. With the rising of the temperature, the two parameters Ts/Tm and C31αβ22S/22 (S+R) increased slowly in the beginning, but when the temperature exceeded 300℃, the parameters increased quickly;when it changed from 250℃ to 300℃, the parameter C32αβ22S/22 (S+R) remained the same, but when it was higher than 300℃, it increased quickly ; the two 8, 14-secohopanes parameters C278β(H) /So (H) and C288β(H) /8α(H) decreased quickly when it was lower than 300℃, and decreased slowly when it was higher than 300℃. The five Parameters all varied greatly at 300℃, so they are nice maturity indexes.
Pyrolysis was done by two methods, the Y series of experiments showed the process of comprehensive original organic matter evolved and the Z series showed the process of only kerogen evolved. The comprehensive original organic matter was composed of non-kerogen matter and kerogen, so based on the two series of experiments we can study deeply how triterpenoids are generated and how they change.From the result of pyrolysis, this paper showed the differences between the comprehensive original organtic matter generated from both non-kerogen matter and kerogen and from only kerogen, and approached geochemical significance of the triterpenoids.The comprehensive original organic matter generated much more pentacyclic triterpenoids than kerogen did, so most pentacyclic triterpenoids were yielded by the non-kerogen matter.In Z series, there were no 8, 14-secohopanes, it's clear that the kerogen didn't yield 8, 14secohopanes. In Y zeries, when the temperature was 400℃, the pentacyclic triterponoids disappeared but 8, 14-secohopanes remained and were abundant, so the pentacyclic triterpanoids changed into 8, 14-secohopanes in high temperature.Hopanes, hopenes and 8, 14-secohopanes are all able to indicate maturity. At 250℃ hopenes were very abundant, but at 300℃ they disappeared, so they can indicate immaturity.Biohopanes are instable, too, when it was 350℃ they disappeared, so they can indicate lowmaturity. Three hopanes parameters and two 8, 14-secohopane ones were calculated. With the rising of the temperature, the two parameters Ts/Tm and C31αβ22S/22 (S+R) increased slowly in the beginning, but when the temperature exceeded 300℃, the parameters increased quickly;when it changed from 250℃ to 300℃, the parameter C32αβ22S/22 (S+R) remained the same, but when it was higher than 300℃, it increased quickly ; the two 8, 14-secohopanes parameters C278β(H) /So (H) and C288β(H) /8α(H) decreased quickly when it was lower than 300℃, and decreased slowly when it was higher than 300℃. The five Parameters all varied greatly at 300℃, so they are nice maturity indexes.
1996, 14(S1): 122-130.
Abstract:
This paper studies different kinds of source rocks including coals, carbonaceous mudstones, oil-shale, argillites and limestones collected throughout China and reports the important results as follows: There are great differences of vitrinite reflectance values (R0% ) formed under the thermal process with same simulating temperature among different kinds of source rocks. And the simulating temperature stages of high-peak production of liquid hydrocarbons produced during the thermally simulating process of organic materials from different kinds of source rocks are also apparently different. So, it is important to pay attentions to the influence of source rock properties and organic material types while vitrinite reflectance taken as an index to divide lithogenetic stages and oil-gas forming stages.
This paper studies different kinds of source rocks including coals, carbonaceous mudstones, oil-shale, argillites and limestones collected throughout China and reports the important results as follows: There are great differences of vitrinite reflectance values (R0% ) formed under the thermal process with same simulating temperature among different kinds of source rocks. And the simulating temperature stages of high-peak production of liquid hydrocarbons produced during the thermally simulating process of organic materials from different kinds of source rocks are also apparently different. So, it is important to pay attentions to the influence of source rock properties and organic material types while vitrinite reflectance taken as an index to divide lithogenetic stages and oil-gas forming stages.
1996, 14(S1): 136-142.
Abstract:
By now the Yangguo loess section is one of the most complete sections of the last 150, 000years. In this paper, the organic components that are bound up with the climatic variation have been studied by the mathematical methods. It can be seen that the probability distributions of loess and Paleosol from the Yangguo section are normal distributions which are differentiated by the mean and standard daviations, respectively. Four cycles stable which are 67.1Ka, 33. 5Ka, 25. 2Ka and 18. 3Ka, have also been recognized. The four periods mentioned above are consistent with the variations of the chemical components from the Luochuan section, and in line with oxygen isotopic values (δ18O) for deep-sea drilled cores and those calculated by Milankovitch for elements of Earth's orbits. That is because that the paleoclimatic evolution in the Quaternary period was controlled by some astronomical factors.
By now the Yangguo loess section is one of the most complete sections of the last 150, 000years. In this paper, the organic components that are bound up with the climatic variation have been studied by the mathematical methods. It can be seen that the probability distributions of loess and Paleosol from the Yangguo section are normal distributions which are differentiated by the mean and standard daviations, respectively. Four cycles stable which are 67.1Ka, 33. 5Ka, 25. 2Ka and 18. 3Ka, have also been recognized. The four periods mentioned above are consistent with the variations of the chemical components from the Luochuan section, and in line with oxygen isotopic values (δ18O) for deep-sea drilled cores and those calculated by Milankovitch for elements of Earth's orbits. That is because that the paleoclimatic evolution in the Quaternary period was controlled by some astronomical factors.
1996, 14(S1): 149-157.
Abstract:
Grain-size distributions of sediments contain important information on sedimentary source, dynamics and environment. The correct use of statistical techniques to extract as much as possible useful signals from grain-size data is of crucial significance. When applying multivariate analysis to grain-size data, however, the auther encountered the problem of "closure",which may mask true patterns significantly. The logratio statistics is an effective way to avoid this problem. This paper presents two case studies respectively in the western Baltic Sea and northern South China Sea. While the classical statistics failed in representing the natural clustering of sediment samples, the RQ-mode principal components analysis based on logratio transforms of grain-size data made a clear separation among sediment classes. The sedimentary regionalization based on this classification successfully reflects the spacial variation of sedimetary hydredynamic environments in these areas.
Grain-size distributions of sediments contain important information on sedimentary source, dynamics and environment. The correct use of statistical techniques to extract as much as possible useful signals from grain-size data is of crucial significance. When applying multivariate analysis to grain-size data, however, the auther encountered the problem of "closure",which may mask true patterns significantly. The logratio statistics is an effective way to avoid this problem. This paper presents two case studies respectively in the western Baltic Sea and northern South China Sea. While the classical statistics failed in representing the natural clustering of sediment samples, the RQ-mode principal components analysis based on logratio transforms of grain-size data made a clear separation among sediment classes. The sedimentary regionalization based on this classification successfully reflects the spacial variation of sedimetary hydredynamic environments in these areas.
1996, 14(S1): 164-170.
Abstract:
This paper introduces the application of the Image Analysis System (IAS) for the quantitative determination of microfeatures and composition of sedimentary rocks, such as mineral composition, percent of pores, morphologic features of fracture, and grain-size analysis. The results are compared with those through other methods. The authors agree that the IAS is faster, more accurate and with large statistic information. But, for most samples, the graylevel automatic detection of IAS seems difficult to be carried out. In this case, the semi-automatic determination is conducted by using the light-pen, and the operator must have geologic knowledge and experience. At last, comments are made on the prospect of the IAS used in ology.
This paper introduces the application of the Image Analysis System (IAS) for the quantitative determination of microfeatures and composition of sedimentary rocks, such as mineral composition, percent of pores, morphologic features of fracture, and grain-size analysis. The results are compared with those through other methods. The authors agree that the IAS is faster, more accurate and with large statistic information. But, for most samples, the graylevel automatic detection of IAS seems difficult to be carried out. In this case, the semi-automatic determination is conducted by using the light-pen, and the operator must have geologic knowledge and experience. At last, comments are made on the prospect of the IAS used in ology.
1996, 14(S1): 181-185.
Abstract:
A new method of flow unit approach to describe and predict reservoir petrophysical properties has been proposed recently. This paper describes a genetic approach to reservoir description, which combines lithofacies analysis with discriminant analysis and probability field simulation for the identification and characterization of flow units on the basis of core and log data.
A new method of flow unit approach to describe and predict reservoir petrophysical properties has been proposed recently. This paper describes a genetic approach to reservoir description, which combines lithofacies analysis with discriminant analysis and probability field simulation for the identification and characterization of flow units on the basis of core and log data.
1996, 14(S1): 192-197.
Abstract:
In this paper, n-alkanes of extracitable organic matter of airborne particulate samples, exhausted gas and smog dust were examined by GC-MS. The results were shown as follows:The concentration of n-alkanes is relative high but its variance depends on different seasons or areas; the comparison among n-alkanes from airborne particulates, exhausted gas and smog dust shows that the atomospheric pollution in Lanzhou results mainly from artificial factors and partly from natural factors with the former being heavier in winter than in summer.
In this paper, n-alkanes of extracitable organic matter of airborne particulate samples, exhausted gas and smog dust were examined by GC-MS. The results were shown as follows:The concentration of n-alkanes is relative high but its variance depends on different seasons or areas; the comparison among n-alkanes from airborne particulates, exhausted gas and smog dust shows that the atomospheric pollution in Lanzhou results mainly from artificial factors and partly from natural factors with the former being heavier in winter than in summer.
1996, 14(S1): 206-213.
Abstract:
The Fuhai area of north Xinjiang is situated in the convergent zone between Siberia Plate and Kazakstan Plate. This area was in an island arc and retroarc basin environment so that its structure activity is violent. There exists many kinds of depositional basins in the Upper Palaeozoic, such as oceanic basin, remnant oceanic basin, island-arc basin, bycontinentalarc basin, intracontinental basin, and so on. There are all kinds of lithofacies: deep-sea,shallow sea, coastal sea, deltaic and fluvial, lacustrine, and swamp facoes. Lots of mixed subfacies zones cause the complex distribution of factes zones. Because of the seawater's withdrawal, continental factes replaced marine factes completely in the Late Carboniferous. Resultantly,the Paleoclimate appeared remarkably different. The Palaeozoic deposition ceased by the end of Early Permian.
The Fuhai area of north Xinjiang is situated in the convergent zone between Siberia Plate and Kazakstan Plate. This area was in an island arc and retroarc basin environment so that its structure activity is violent. There exists many kinds of depositional basins in the Upper Palaeozoic, such as oceanic basin, remnant oceanic basin, island-arc basin, bycontinentalarc basin, intracontinental basin, and so on. There are all kinds of lithofacies: deep-sea,shallow sea, coastal sea, deltaic and fluvial, lacustrine, and swamp facoes. Lots of mixed subfacies zones cause the complex distribution of factes zones. Because of the seawater's withdrawal, continental factes replaced marine factes completely in the Late Carboniferous. Resultantly,the Paleoclimate appeared remarkably different. The Palaeozoic deposition ceased by the end of Early Permian.
1996, 14(S1): 10-17.
Abstract:
Detailed research has been done on organic petrology and geochemistry of the coalmeasure source rocks sampled from typical coal basins in China. The following acknowlegements have been obtained:1) Coals can generate a large amount of gas as well as some liquid hydrocarbons during the thermal-maturation evolution. The source matter which can generate oil in coals includes not only exinite, but also desmocollinite and even a part of telocollinite.2) Coal macerals are the main parameters to evaluate the hydrocarbon potential of coalmeasure source rocks. According to the Rock-Eval and element analysis results,the coalmeasure source rocks can be subdivided into four types: c, Ⅱ c,Ⅲ c and Ⅳ c.Ⅰc and Ⅱ c can generate a large amount of oils and may form coal-generated oil and gas fields under the suitable geological background. However,type Ⅲ c and Ⅳ c can mainly generate gas.3) The hydrocar bon-generating patterns of coals mainly depend on the types and amount of hydrocabron-generating macerals. On the base of the hydrocarbon-generating patterns of coal macerals, the hydrocarbon-generating mdel for the four types of coal-measure source rocks has been suggested. This model will be very useful to the evaluation and exploration of coal-measure source rocks of coal-bearing basins in China.
Detailed research has been done on organic petrology and geochemistry of the coalmeasure source rocks sampled from typical coal basins in China. The following acknowlegements have been obtained:1) Coals can generate a large amount of gas as well as some liquid hydrocarbons during the thermal-maturation evolution. The source matter which can generate oil in coals includes not only exinite, but also desmocollinite and even a part of telocollinite.2) Coal macerals are the main parameters to evaluate the hydrocarbon potential of coalmeasure source rocks. According to the Rock-Eval and element analysis results,the coalmeasure source rocks can be subdivided into four types: c, Ⅱ c,Ⅲ c and Ⅳ c.Ⅰc and Ⅱ c can generate a large amount of oils and may form coal-generated oil and gas fields under the suitable geological background. However,type Ⅲ c and Ⅳ c can mainly generate gas.3) The hydrocar bon-generating patterns of coals mainly depend on the types and amount of hydrocabron-generating macerals. On the base of the hydrocarbon-generating patterns of coal macerals, the hydrocarbon-generating mdel for the four types of coal-measure source rocks has been suggested. This model will be very useful to the evaluation and exploration of coal-measure source rocks of coal-bearing basins in China.
1996, 14(S1): 25-32.
Abstract:
Zhen'an basin, situated at the northern margin of South Qinling, is bounded to the north by the Shanyang fault and to the south by the Banyanzhen fault, respectively. It was a rifted basin and filled mainly with siliciclastic turbidites during Late Devonian.The turbidite system is made up of the Jiuliping formation (Upper Devonian), which can be divided spacially into two segments, the northern Jiuliping formation and southern Jiuliping formaion, according to facies characteristics. The lower part of the northern Jiuliping formation is composed of slope fine-grained sediments, inclusive of hemipelagites and fine-grained turbidites, but commonly cut by gullies which are filled with coarse-grained gravity-flow deposits. In contrast, the lower part of the southern Jiuliping formation consists of channel-levee and lobe deposits, but typical thinning-and-fining-upward, or thickening-and-coarseningupward sequences are not well developed. The channel-levee and lobe units are blanketed with basin plain deposits, they are then changed into thin-layered deep-water carbonate rocks.Clearly, the whole Upper Devonian sequences show a deepening-upward tendency. In addition, it is demonstrated on the basis of analysis of paleocurrents and source areas that the siliciclastic turbidite system was fed from a linear source area to the north, but turbidity current was deflected eastwards along the basin axis. The turbidite system studied is not a classical submarine fan but one that has much in common with the ramp turbidite system model.The turbidite system and basin development are apparently influenced by tectonism, sealevel fluctuation and sediment supply. The rifting leads to the drowning of Middle Devonian carbonate platform and the initiation of siliciclastic turbidite system, and the uppermost deepwater carbonate rocks or carbonate turbidites are believed to be related to sea-level rising. The Late Devonian initiation and development of Zhen'an Basin resulted from the peripheral upwell and induced extension in the upper crust at the northern margin of the subducting South Qinling plate in consideration of regional tectonism.
Zhen'an basin, situated at the northern margin of South Qinling, is bounded to the north by the Shanyang fault and to the south by the Banyanzhen fault, respectively. It was a rifted basin and filled mainly with siliciclastic turbidites during Late Devonian.The turbidite system is made up of the Jiuliping formation (Upper Devonian), which can be divided spacially into two segments, the northern Jiuliping formation and southern Jiuliping formaion, according to facies characteristics. The lower part of the northern Jiuliping formation is composed of slope fine-grained sediments, inclusive of hemipelagites and fine-grained turbidites, but commonly cut by gullies which are filled with coarse-grained gravity-flow deposits. In contrast, the lower part of the southern Jiuliping formation consists of channel-levee and lobe deposits, but typical thinning-and-fining-upward, or thickening-and-coarseningupward sequences are not well developed. The channel-levee and lobe units are blanketed with basin plain deposits, they are then changed into thin-layered deep-water carbonate rocks.Clearly, the whole Upper Devonian sequences show a deepening-upward tendency. In addition, it is demonstrated on the basis of analysis of paleocurrents and source areas that the siliciclastic turbidite system was fed from a linear source area to the north, but turbidity current was deflected eastwards along the basin axis. The turbidite system studied is not a classical submarine fan but one that has much in common with the ramp turbidite system model.The turbidite system and basin development are apparently influenced by tectonism, sealevel fluctuation and sediment supply. The rifting leads to the drowning of Middle Devonian carbonate platform and the initiation of siliciclastic turbidite system, and the uppermost deepwater carbonate rocks or carbonate turbidites are believed to be related to sea-level rising. The Late Devonian initiation and development of Zhen'an Basin resulted from the peripheral upwell and induced extension in the upper crust at the northern margin of the subducting South Qinling plate in consideration of regional tectonism.
1996, 14(S1): 38-48.
Abstract:
The formation of Baiwan Basin, which is situated in Zhengping County of Henan Province, has been controlled by a strike-slip fault system formed by the relative movement of the Huabei Plate and the Yangtze Plate on their boundaries since Late Triassic. Under the action of a right-lateral shear strike-slip structure and controlled by a partial tensile stress, a series of "Z" -shaped Mesozoic pull-apart basins have been formed, of which Baiwan Basin,as a narrow but deeply-depressed rhombic structural basin, is bounded by faults on both the north and the south, and the basin formed in the second episode of the Yanshan movement.In this basin Baiwan Formation of the Lower Cretaceous (K1) is unconformed with the lower part (K2a), Gaogou Formation, of the Upper Cretaceous, but the fault contact occurs on both the top and bottom of the Cretaceous System. Baiwan Formation of the Early Cretaceous is set up according to its Ostracoda fossil assemblage, which is dominated by Cypridea,subordinated by Rhinocypris, and occasionally accompanied with Darwinula Legurninella and Clinocypris, basically identical to the Cyprtidea-dominated fossil assemblage of the Early Cretaceous in other terrestrial sedimentary basins of the world. Its spore-Pollen fossils are constituted by Classopllis-Schizaeois porites for the lower assemblage ; by Classopollis-Schizaeoisporites-Jugella-Cicatricosisporites for the upper assemblage. The species of these two assemblages are generally the same except for the obvious difference in their concentrations. In addition, both the assemblages contain the disputable angiosperm pollen. In China, there were at least two quite different spore-pollen florae, the Huabei and the Huanan florae, during the Early Cretaceous. Baiwan Formation belongs to the Huanan flora but with small amount of spore-pollen components of the Huabei flora, being characteristic of a transitional zone. and its age, therefore, should be the Early Cretaceous before Aptian. The lower spore-pollen assemblage corresponds to Berriasion-Valanginian while the upper one to HauteriveBarremian. The dominance of xerophytes in the spore-pollen florae suggests that the climate at thattime was rather dry, but the climate of the upper spore-pollen assemblage was relatively humid compared with that of the lower one.The Cretaceous profile in Baiwan Basin is about 600 m in thickness. In the early stage of the lower Cretaceous, shore was flat due to weak fault and subsidence and the deposit system was dominated by alluvial fan - flood braided plain -shore and shallow labe; in the middle stage stronger fault and subsidence made shore steep, lake area enlarged and water body deepening. The deposit system became to fan delta-shallow lake and deeper lake. The alluvial fan consists of a suite of dark-brown and grey-white psephyte and psephytic compound sandstone and gravels are randomly distributed with the diameter ranging from 20cm to 1cm. The flood braided plain facies is composed of brown-red mudstone and sandy mudstone intercalat homochromatic psephytic compound sandstone. The fan delta is identical to alluvial fan in lithology except for the grey-green and grey-yellow color due to the submarine deposition.The psephyte contacts directly with green-grey and dark-grey paper-like shale and laminated marl of lake factes, constituting a 100m interbedding, and the latter belongs to a deeper lake factes, thus this suite of psephyte is regarded as a fan delta facies. The shallow lake facies of this profile is made up dominantly of grey-green and yellow-green mud shale intercalated with marl-bearing lenticular mud shale and laminated marl while the deeper lake factes contains dark-grey and dark-green paper-like, lamellar and medium-bedded marl interbedding with pyrite strip. This kind of marl is mainly controlled by a deep-water sedimentary environment, and secondly associated with relatively dry climate. It can be seen from the outcrop of the profile that secondary carbonate, filled in along the joint of mud shale and marl,has been weathered into beautiful honeycomb struc.
The formation of Baiwan Basin, which is situated in Zhengping County of Henan Province, has been controlled by a strike-slip fault system formed by the relative movement of the Huabei Plate and the Yangtze Plate on their boundaries since Late Triassic. Under the action of a right-lateral shear strike-slip structure and controlled by a partial tensile stress, a series of "Z" -shaped Mesozoic pull-apart basins have been formed, of which Baiwan Basin,as a narrow but deeply-depressed rhombic structural basin, is bounded by faults on both the north and the south, and the basin formed in the second episode of the Yanshan movement.In this basin Baiwan Formation of the Lower Cretaceous (K1) is unconformed with the lower part (K2a), Gaogou Formation, of the Upper Cretaceous, but the fault contact occurs on both the top and bottom of the Cretaceous System. Baiwan Formation of the Early Cretaceous is set up according to its Ostracoda fossil assemblage, which is dominated by Cypridea,subordinated by Rhinocypris, and occasionally accompanied with Darwinula Legurninella and Clinocypris, basically identical to the Cyprtidea-dominated fossil assemblage of the Early Cretaceous in other terrestrial sedimentary basins of the world. Its spore-Pollen fossils are constituted by Classopllis-Schizaeois porites for the lower assemblage ; by Classopollis-Schizaeoisporites-Jugella-Cicatricosisporites for the upper assemblage. The species of these two assemblages are generally the same except for the obvious difference in their concentrations. In addition, both the assemblages contain the disputable angiosperm pollen. In China, there were at least two quite different spore-pollen florae, the Huabei and the Huanan florae, during the Early Cretaceous. Baiwan Formation belongs to the Huanan flora but with small amount of spore-pollen components of the Huabei flora, being characteristic of a transitional zone. and its age, therefore, should be the Early Cretaceous before Aptian. The lower spore-pollen assemblage corresponds to Berriasion-Valanginian while the upper one to HauteriveBarremian. The dominance of xerophytes in the spore-pollen florae suggests that the climate at thattime was rather dry, but the climate of the upper spore-pollen assemblage was relatively humid compared with that of the lower one.The Cretaceous profile in Baiwan Basin is about 600 m in thickness. In the early stage of the lower Cretaceous, shore was flat due to weak fault and subsidence and the deposit system was dominated by alluvial fan - flood braided plain -shore and shallow labe; in the middle stage stronger fault and subsidence made shore steep, lake area enlarged and water body deepening. The deposit system became to fan delta-shallow lake and deeper lake. The alluvial fan consists of a suite of dark-brown and grey-white psephyte and psephytic compound sandstone and gravels are randomly distributed with the diameter ranging from 20cm to 1cm. The flood braided plain facies is composed of brown-red mudstone and sandy mudstone intercalat homochromatic psephytic compound sandstone. The fan delta is identical to alluvial fan in lithology except for the grey-green and grey-yellow color due to the submarine deposition.The psephyte contacts directly with green-grey and dark-grey paper-like shale and laminated marl of lake factes, constituting a 100m interbedding, and the latter belongs to a deeper lake factes, thus this suite of psephyte is regarded as a fan delta facies. The shallow lake facies of this profile is made up dominantly of grey-green and yellow-green mud shale intercalated with marl-bearing lenticular mud shale and laminated marl while the deeper lake factes contains dark-grey and dark-green paper-like, lamellar and medium-bedded marl interbedding with pyrite strip. This kind of marl is mainly controlled by a deep-water sedimentary environment, and secondly associated with relatively dry climate. It can be seen from the outcrop of the profile that secondary carbonate, filled in along the joint of mud shale and marl,has been weathered into beautiful honeycomb struc.
1996, 14(S1): 57-62.
Abstract:
Biyang Depression is a Mesozoic-Cenozoic interior oil-bearing basin, with an area of 1000 km2, in eastern China. The lacustrine carbonate rocks of the Eogene Hetaoyuan Formation deposited in the center of this basin. They are mainly composed of mudstone, dolomitic mudstone, argillic dolostone, dolostone, silty dolostone and intercalated with alkali beds. The alga fossils from the lacustrine carbonate rocks in the upper third to the second member of Hetaoyuan Formation were studied. They could be dentified as three assemblages, Fromea chytra assemblage, Dictyotidium assemblage and Rugasphaera-Dictyotidium-Concentricystes It reflected that the palaeo-lake water salinity changed from the higher to lower successively. In addition, the vertical alga distribution assumed a cyclical change of flourishing and declining. The higher silinity alga assemlage and the lower one alternately appeared in the algae flourishing periods. It was showed that the palaeo-lake water salinity might undergo three relatively Salty water stages and two relatively fresh water stages under the brackish water setting and the palaeclimate period might include two relatively warm and wet stages and three relatively hot and dry stages in the depositional period of the upper third to the second member of Hetaoyuan Formation.
Biyang Depression is a Mesozoic-Cenozoic interior oil-bearing basin, with an area of 1000 km2, in eastern China. The lacustrine carbonate rocks of the Eogene Hetaoyuan Formation deposited in the center of this basin. They are mainly composed of mudstone, dolomitic mudstone, argillic dolostone, dolostone, silty dolostone and intercalated with alkali beds. The alga fossils from the lacustrine carbonate rocks in the upper third to the second member of Hetaoyuan Formation were studied. They could be dentified as three assemblages, Fromea chytra assemblage, Dictyotidium assemblage and Rugasphaera-Dictyotidium-Concentricystes It reflected that the palaeo-lake water salinity changed from the higher to lower successively. In addition, the vertical alga distribution assumed a cyclical change of flourishing and declining. The higher silinity alga assemlage and the lower one alternately appeared in the algae flourishing periods. It was showed that the palaeo-lake water salinity might undergo three relatively Salty water stages and two relatively fresh water stages under the brackish water setting and the palaeclimate period might include two relatively warm and wet stages and three relatively hot and dry stages in the depositional period of the upper third to the second member of Hetaoyuan Formation.
1996, 14(S1): 75-83.
Abstract:
Based on the sedimentary microfactes and bioecologic analysis of the Qixia formation of three sections in studied area, this paper summaries the depositional rhythms, cycles and sedimentary environment of the Qixia formation, and further analyses the characteristics of its sedimentary evolution. The results suggest that the Qixia formation was formed in a subtidal,low energy, open and non-barrier carbonate ramp belt.
Based on the sedimentary microfactes and bioecologic analysis of the Qixia formation of three sections in studied area, this paper summaries the depositional rhythms, cycles and sedimentary environment of the Qixia formation, and further analyses the characteristics of its sedimentary evolution. The results suggest that the Qixia formation was formed in a subtidal,low energy, open and non-barrier carbonate ramp belt.
1996, 14(S1): 90-99.
Abstract:
The carbonate source-rocks of the Ordovician are relatively poor in organic matter (Corg 0.24% ). According to the result on gas/source-rock correlation, it could be suggested that the carbonates with mean over 0. 2% organic carbon content at stage of over maturity should be able to form largescale oil-gas accumulation. Furthermore, this paper proposed in the carbonates with mean over 0. 15% organic carbon content the expulsion, migration and accumulation of hydrocarbons can happen based on fluorescence thin-section observation.The paper had listed the carbonate source-rocks from five kinds of sedimentary environments which have the different content of organic matter and original potential of hydrocarbon generation, and put stress on the comparison of calcareous alga-bearing carbonates with cryptalgal-bearing carbonates as well. The Cryptalgal-bearing carbonates are main sourcerocks of natural gases in the central gas-field. Finally this paper suggested following views:(1) The carbonates, rich in non-skeleton algae or other organic-shell living bodies, are good source rocks.(2) The content of organic matter in carbonates mainly depends on the oxidationreduction condition of deposition, shallow burial and the content of mudstone.(3) The oxidation-reduction condition also influences original properties of kerogen. In reduction system there is a high residual ratio to bio-remains, and original lipid properties of kerogen could be protected because oxidization not only reduces the content of organic matter,but also damages lipid properties of primary kerogen and decrease the potential of the kerogens. Although almost all kerogen in the Early Palaeozoic Period originated from precursers such as algae, plankton and palaeo-bacteria etc., they may have different potential. Based on analysis and calculation, generally, the carbonate with lower organic carbon content was merely medium potential (IH0=250±) of hydrocarbons generation, however, it might have high efficiency of expulsion of hydrocarbons.
The carbonate source-rocks of the Ordovician are relatively poor in organic matter (Corg 0.24% ). According to the result on gas/source-rock correlation, it could be suggested that the carbonates with mean over 0. 2% organic carbon content at stage of over maturity should be able to form largescale oil-gas accumulation. Furthermore, this paper proposed in the carbonates with mean over 0. 15% organic carbon content the expulsion, migration and accumulation of hydrocarbons can happen based on fluorescence thin-section observation.The paper had listed the carbonate source-rocks from five kinds of sedimentary environments which have the different content of organic matter and original potential of hydrocarbon generation, and put stress on the comparison of calcareous alga-bearing carbonates with cryptalgal-bearing carbonates as well. The Cryptalgal-bearing carbonates are main sourcerocks of natural gases in the central gas-field. Finally this paper suggested following views:(1) The carbonates, rich in non-skeleton algae or other organic-shell living bodies, are good source rocks.(2) The content of organic matter in carbonates mainly depends on the oxidationreduction condition of deposition, shallow burial and the content of mudstone.(3) The oxidation-reduction condition also influences original properties of kerogen. In reduction system there is a high residual ratio to bio-remains, and original lipid properties of kerogen could be protected because oxidization not only reduces the content of organic matter,but also damages lipid properties of primary kerogen and decrease the potential of the kerogens. Although almost all kerogen in the Early Palaeozoic Period originated from precursers such as algae, plankton and palaeo-bacteria etc., they may have different potential. Based on analysis and calculation, generally, the carbonate with lower organic carbon content was merely medium potential (IH0=250±) of hydrocarbons generation, however, it might have high efficiency of expulsion of hydrocarbons.
1996, 14(S1): 115-121.
Abstract:
This paper studed the thermally simulated oils from Pinus pollen grains by GC, GC-MSand so on. The results showed that sporopollen is a kind of good terrigenous oil-generating material. The main composition of the pyrolysis oils is aromatic hydrocarbons with subordinate saturated hydrocarbons subordinate. The low-temperature pyrolysis stage (400℃) is characterized by generating large amount of saturated hydrocarbons, and the high-temperature stage (400℃), aromatic hydrocarbons. As for the aromatic hydrocarbons, monocyclic and dicyclic ones are their main components.Normal alkanes are the most abundant compounds of the thermally decomposed oils, the carbon number distribution is from C4 to C28, and C12 is the highest peak in the most cases.The gas-chromatogram spectra of the oils in the high temperature stage are distributed in a form of double-peaks. The former peak is even-carbon domination and the latter one, an order-carbon domination. The light hydrocarbon chromatographic parameters, e. g., nC6/iC6,nC7/iC7, nC6/cC6 etc. decrease with the increase of pyrolysis temperature and reach to the maximum at 450℃ (R0=1. 88). Then all the ratios mentioned above decrease with the continuous increase of the temperature, so the point at 450℃ may be thought as the upper limit of the high peak oilgeneration. The content of C15+ heavy hydrocarbons is greater than that of C15- light hydrocarbons in the low-temperature stage, contrarily in the high-temperatue stage the light hydrocarbons are abundant. That is to say that sporopollen can generate oils in which either heavy hydrocarbons or light ones can be the main components, just depending on the different pyrolytic temperatues. It shows, furthermore, that the material of higher plant origins can generate both gases and oils.Besides n-alkanes, there are higher contents of alkyl-benzene series, alkyl-cycloherane series, alkyl-cyclopentane series and alkyl-phenol series in the thermals simulated oils. The carbon number distribution is C7-C21 for the former three series, and C7-C11 for the latter one.All of those series are common components of Petroleum, it means that sporopollen is a kind of widespread Oil-source materials. The compounds with phenol structure are one of the characteristics of higher plants, thus the detection of the phenol structure compounds in the pyrolysis oils from Pinus pollen supplies a direct evidence for those kinds of compounds derived from higher plants in continental oils.The parameters of Pr/Ph, Pr/nC17 and Ph/nC18 ratios vary to a great degree at different temperature stages. It is shown that those parameters may greatly change in different maturestages even though organic materials are of the same kind. So the mature stages must be considered when those parameters mentioned above are used to classify sedimentary environments of source rocks.
This paper studed the thermally simulated oils from Pinus pollen grains by GC, GC-MSand so on. The results showed that sporopollen is a kind of good terrigenous oil-generating material. The main composition of the pyrolysis oils is aromatic hydrocarbons with subordinate saturated hydrocarbons subordinate. The low-temperature pyrolysis stage (400℃) is characterized by generating large amount of saturated hydrocarbons, and the high-temperature stage (400℃), aromatic hydrocarbons. As for the aromatic hydrocarbons, monocyclic and dicyclic ones are their main components.Normal alkanes are the most abundant compounds of the thermally decomposed oils, the carbon number distribution is from C4 to C28, and C12 is the highest peak in the most cases.The gas-chromatogram spectra of the oils in the high temperature stage are distributed in a form of double-peaks. The former peak is even-carbon domination and the latter one, an order-carbon domination. The light hydrocarbon chromatographic parameters, e. g., nC6/iC6,nC7/iC7, nC6/cC6 etc. decrease with the increase of pyrolysis temperature and reach to the maximum at 450℃ (R0=1. 88). Then all the ratios mentioned above decrease with the continuous increase of the temperature, so the point at 450℃ may be thought as the upper limit of the high peak oilgeneration. The content of C15+ heavy hydrocarbons is greater than that of C15- light hydrocarbons in the low-temperature stage, contrarily in the high-temperatue stage the light hydrocarbons are abundant. That is to say that sporopollen can generate oils in which either heavy hydrocarbons or light ones can be the main components, just depending on the different pyrolytic temperatues. It shows, furthermore, that the material of higher plant origins can generate both gases and oils.Besides n-alkanes, there are higher contents of alkyl-benzene series, alkyl-cycloherane series, alkyl-cyclopentane series and alkyl-phenol series in the thermals simulated oils. The carbon number distribution is C7-C21 for the former three series, and C7-C11 for the latter one.All of those series are common components of Petroleum, it means that sporopollen is a kind of widespread Oil-source materials. The compounds with phenol structure are one of the characteristics of higher plants, thus the detection of the phenol structure compounds in the pyrolysis oils from Pinus pollen supplies a direct evidence for those kinds of compounds derived from higher plants in continental oils.The parameters of Pr/Ph, Pr/nC17 and Ph/nC18 ratios vary to a great degree at different temperature stages. It is shown that those parameters may greatly change in different maturestages even though organic materials are of the same kind. So the mature stages must be considered when those parameters mentioned above are used to classify sedimentary environments of source rocks.
1996, 14(S1): 131-135.
Abstract:
In this paper the hydrogen isotope compositions of methane, crude as well as light oils and kerogen and their relationship with the depositional environments and the maturity of source rocks were discussed in detail. The hydrogen isotope compositions of methane are mainly related to depositional environments of source rocks. Methane of terrestrial fresh water environments has lighter hydrogen isotope compositions, and that of brackish to salt water environments has heavier hydrogen isotope compositions. Simultaneously, the hydrogen isotope compositions of methane are also related to the maturity of source rocks, i. e., with the increasing maturity of source rocks, the δD of methane becomes heavier. When using the δD of methane to differentiate depositional environments of source rocks, the effect of the maturity of source rocks on the δD of methane should be considered. The hydrogen isotope compositions of crude and light oils are mainly related to depositional environments of source rocks. Oils derived in fresh water environments have lighter δD, and those in brackish to salt water environments have heavier δD. The hydrogen isotope compositions of kerogen are also controlled by depositional environments, i. e., kerogens derived from fresh water environments have lighter δD,and those from brackish to salt water environments have heavier δD.
In this paper the hydrogen isotope compositions of methane, crude as well as light oils and kerogen and their relationship with the depositional environments and the maturity of source rocks were discussed in detail. The hydrogen isotope compositions of methane are mainly related to depositional environments of source rocks. Methane of terrestrial fresh water environments has lighter hydrogen isotope compositions, and that of brackish to salt water environments has heavier hydrogen isotope compositions. Simultaneously, the hydrogen isotope compositions of methane are also related to the maturity of source rocks, i. e., with the increasing maturity of source rocks, the δD of methane becomes heavier. When using the δD of methane to differentiate depositional environments of source rocks, the effect of the maturity of source rocks on the δD of methane should be considered. The hydrogen isotope compositions of crude and light oils are mainly related to depositional environments of source rocks. Oils derived in fresh water environments have lighter δD, and those in brackish to salt water environments have heavier δD. The hydrogen isotope compositions of kerogen are also controlled by depositional environments, i. e., kerogens derived from fresh water environments have lighter δD,and those from brackish to salt water environments have heavier δD.
1996, 14(S1): 143-148.
Abstract:
Non-oxygen thermo-analysis at three different temperatures was Performed for the 19 biogas source rock samples from Ying-Qiong Basin in South China Sea and Qaidam Basin in Qinghai Province. The results showed that the thermo-decomposing temperature was 260-270℃ for polysaccharides (such as cellululose, semi-cellose) and lipid compounds. Also, the thermo-decomposing temperature was lower than 320℃ for most of nucleic acids and proteins.Therefore, the thermo-decomposing value at 330℃ for 1 hr. could be used to estimate the production abundance of biochemical methane.
Non-oxygen thermo-analysis at three different temperatures was Performed for the 19 biogas source rock samples from Ying-Qiong Basin in South China Sea and Qaidam Basin in Qinghai Province. The results showed that the thermo-decomposing temperature was 260-270℃ for polysaccharides (such as cellululose, semi-cellose) and lipid compounds. Also, the thermo-decomposing temperature was lower than 320℃ for most of nucleic acids and proteins.Therefore, the thermo-decomposing value at 330℃ for 1 hr. could be used to estimate the production abundance of biochemical methane.
The Polystage Evolution of the Subsidence Downwarping Region and Formation of Petroleum Accumulation
1996, 14(S1): 158-163.
Abstract:
The subsidence downwarping region in petroleum bearing basins was found to be characteristic of polystage and polycycle development. The characteristics of tectonic movement controlled the formation and devolopment of sediment subsidence and petroleum bearing depression center, and also influenced the sedimentary rock sequence and formation of hydrocarbon source rocks. The process of successive subsidence or interruptly polystage subsidence existed during the formation of petroleum bearing downwarping region as a result of the vertical superposition of prototype basins in the geologic time. This process controlted the polystage successivety hydrocarbon-generating process in the thermal evolution of sonroe rocks, in the condition of continuously being buried.Multiphase tectonic movements formed faults shatter belts regional, unconformity and fissure system of structural culmination, which together with good primary porosity-Permeability and secondary porosity-permeability system in the process of diagenesis supplied different phases and types of oil and gas under the condition of migration and entrapment.
The subsidence downwarping region in petroleum bearing basins was found to be characteristic of polystage and polycycle development. The characteristics of tectonic movement controlled the formation and devolopment of sediment subsidence and petroleum bearing depression center, and also influenced the sedimentary rock sequence and formation of hydrocarbon source rocks. The process of successive subsidence or interruptly polystage subsidence existed during the formation of petroleum bearing downwarping region as a result of the vertical superposition of prototype basins in the geologic time. This process controlted the polystage successivety hydrocarbon-generating process in the thermal evolution of sonroe rocks, in the condition of continuously being buried.Multiphase tectonic movements formed faults shatter belts regional, unconformity and fissure system of structural culmination, which together with good primary porosity-Permeability and secondary porosity-permeability system in the process of diagenesis supplied different phases and types of oil and gas under the condition of migration and entrapment.
1996, 14(S1): 171-180.
Abstract:
The reasearch area of polymetallic nodules is located between Clariion Fracture and Clipperton Fracture, where polymetallic nodule resources are most abudant. The authors have investigated in this area for many times, and have obtainted a lot of materials and samples. The todorokite existing in nodules as the most useful manganese mineral is in a close relationship with many metallic elements. To analyse the distribution of todorokite and its relative factors is meaningful for probing into the nodules' formation mechanism. For its poor crystallinity and tiny grain, to identify todorokite is very difficult. By all sorts of analysis methods, the authors tried to prove the existence of todorokite, to study its mineral features and the relationships among its main metallic elements, and then to provide scientific basis for ore dressing and metallurgy.The study result reveals: 1) There exists todorokite in marine nodules that act as the most important manganese mineral phase. Its optic characteristic, x-ray diffraction analysis data and cell parameters are close to those of manganese. Infrared analysis also show typical todorokite spectrums. Electron microscope analysis suggests that the manganese in crystallizing band is mainly todorokite and its Mn, Cu, Ni contents are higher than those in amorphous band. 2)The todorokite content in coarse-surface nodules in deep-sea plain is often richer than that in smooth-surface nodules found in seamount. Todorokite is abundant when the substratum structure is laninar, compact, or taxitic.The paper suggests that the factors causing todorokite distributed in such a way are mainly related with the local geochemical environment. The reduction-oxidation potential value is a direct factor which affects the formation of todorokite. The low reduction-oxidation potential is helpful. The isomorph of some metal elements such as Mn, Ni, Cu, Zn, is positively related to manganese. The slight reduction-oxidation environment and peneliquid substratum are an ideal horizon which is favourable not only to the migration of the Mn ion, but also to the accumulation of Mn. The metal elements engendered by dissolution of the living beings can promote the formation of manganese noudules. Recrystalization also changes a part of amorphous body into todorokite.Based on the study of the nodules' mineralogy, it is suggested that the best mineral resource for ore dressing and metallurgy is rough-surface nodules and semi-rough-surface nodules.
The reasearch area of polymetallic nodules is located between Clariion Fracture and Clipperton Fracture, where polymetallic nodule resources are most abudant. The authors have investigated in this area for many times, and have obtainted a lot of materials and samples. The todorokite existing in nodules as the most useful manganese mineral is in a close relationship with many metallic elements. To analyse the distribution of todorokite and its relative factors is meaningful for probing into the nodules' formation mechanism. For its poor crystallinity and tiny grain, to identify todorokite is very difficult. By all sorts of analysis methods, the authors tried to prove the existence of todorokite, to study its mineral features and the relationships among its main metallic elements, and then to provide scientific basis for ore dressing and metallurgy.The study result reveals: 1) There exists todorokite in marine nodules that act as the most important manganese mineral phase. Its optic characteristic, x-ray diffraction analysis data and cell parameters are close to those of manganese. Infrared analysis also show typical todorokite spectrums. Electron microscope analysis suggests that the manganese in crystallizing band is mainly todorokite and its Mn, Cu, Ni contents are higher than those in amorphous band. 2)The todorokite content in coarse-surface nodules in deep-sea plain is often richer than that in smooth-surface nodules found in seamount. Todorokite is abundant when the substratum structure is laninar, compact, or taxitic.The paper suggests that the factors causing todorokite distributed in such a way are mainly related with the local geochemical environment. The reduction-oxidation potential value is a direct factor which affects the formation of todorokite. The low reduction-oxidation potential is helpful. The isomorph of some metal elements such as Mn, Ni, Cu, Zn, is positively related to manganese. The slight reduction-oxidation environment and peneliquid substratum are an ideal horizon which is favourable not only to the migration of the Mn ion, but also to the accumulation of Mn. The metal elements engendered by dissolution of the living beings can promote the formation of manganese noudules. Recrystalization also changes a part of amorphous body into todorokite.Based on the study of the nodules' mineralogy, it is suggested that the best mineral resource for ore dressing and metallurgy is rough-surface nodules and semi-rough-surface nodules.
1996, 14(S1): 186-191.
Abstract:
This paper introduces an identification of sedimentary microfactes by the pattern recognition approach using neural network. The approach firstly established the relationship between the logging facies and geological facies according to the key-well study as an identified pattern,then obtained intelligent knowledge by learning from the identified pattern, and finally applied the knowledge to identify the microfacies in unknown wells and sites again. The approach was successfully applied in the recognition and subdivision of sedimentary microfacies of the 4th member of the Shahejie formation, Wenlin Area, Zhongyuan Oilfield.
This paper introduces an identification of sedimentary microfactes by the pattern recognition approach using neural network. The approach firstly established the relationship between the logging facies and geological facies according to the key-well study as an identified pattern,then obtained intelligent knowledge by learning from the identified pattern, and finally applied the knowledge to identify the microfacies in unknown wells and sites again. The approach was successfully applied in the recognition and subdivision of sedimentary microfacies of the 4th member of the Shahejie formation, Wenlin Area, Zhongyuan Oilfield.
1996, 14(S1): 198-205.
Abstract:
This paper has studied the nature, source and maturity of organic matter in the Bijiashan lead-zinc deposits by analysis of extractable organic matter in the ores and adjacent rocks.The probably primary migration form of organic matter, probable genesis of ore-forming fluids and ore-forming environment are discussed. The fractions of chloroform extracts and distributional features of biomarkers reflect that organic matter is mainly composed of aquatic organism and bacteria and comes from the ore source bed of carbonate rocks. Based on analysis of the data of geology and geochemistry of the ore deposits, it is believed that the primary migration form of organic matter in the ore deposits probably is humic acid, and that the ore fluids probably are derived from diagenetic solutions in carbonate rocks. Low ratios of Pr/Ph and existence of βcarotane indicate that the ore deposits are formed under a strongly reducing environment.Those results are important in understanding genesis of the ore deposits.
This paper has studied the nature, source and maturity of organic matter in the Bijiashan lead-zinc deposits by analysis of extractable organic matter in the ores and adjacent rocks.The probably primary migration form of organic matter, probable genesis of ore-forming fluids and ore-forming environment are discussed. The fractions of chloroform extracts and distributional features of biomarkers reflect that organic matter is mainly composed of aquatic organism and bacteria and comes from the ore source bed of carbonate rocks. Based on analysis of the data of geology and geochemistry of the ore deposits, it is believed that the primary migration form of organic matter in the ore deposits probably is humic acid, and that the ore fluids probably are derived from diagenetic solutions in carbonate rocks. Low ratios of Pr/Ph and existence of βcarotane indicate that the ore deposits are formed under a strongly reducing environment.Those results are important in understanding genesis of the ore deposits.
1996, 14(S1): 214-219.
Abstract:
Plenty of geochemical analyses were carried out on natural gas, oil and condensate samples collected from two wells in Tarim Basin and results were employed in interpreting their sources and distinguishing one from the other. The chemical compositions of gases from the both wells showed that they are of oilfied associated gas with a low dry coeffieient. Their carbon isotopic compositions might indicate a mixture of gas sources, and the input of the mantle-derived materials was denied by the isotopic parameters of noble gases, such as 3 He4He and4 He/20Ne ratios. The age of gases from these two wells was identified to be the Palaeozoic by the 40Ar/36Ar ratio.
Plenty of geochemical analyses were carried out on natural gas, oil and condensate samples collected from two wells in Tarim Basin and results were employed in interpreting their sources and distinguishing one from the other. The chemical compositions of gases from the both wells showed that they are of oilfied associated gas with a low dry coeffieient. Their carbon isotopic compositions might indicate a mixture of gas sources, and the input of the mantle-derived materials was denied by the isotopic parameters of noble gases, such as 3 He4He and4 He/20Ne ratios. The age of gases from these two wells was identified to be the Palaeozoic by the 40Ar/36Ar ratio.
