Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of ...Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.展开更多
The age-accumulation effect of 40Ar in hydrocarbon source rocks was discussed in accordance with the decay law of radioactive elements. In terms of the mean values of 40Ar/36Ar, the old Sinian gas reservoirs (mean val...The age-accumulation effect of 40Ar in hydrocarbon source rocks was discussed in accordance with the decay law of radioactive elements. In terms of the mean values of 40Ar/36Ar, the old Sinian gas reservoirs (mean values of 40Ar/36Ar: 7009) were definitely distinguished from the Permian gas reservoirs (mean values of 40Ar/36Ar: 1017) in Weiyuan, Sichuan Province, and the gas source of the Permian gas reservoir (mean values of 40Ar/36Ar: 5222) in well Wei-7 with the Weiyuan structure is defined as the Sinian system. Based on the values of 40Ar/36Ar, the coal-type gases (The source rocks are of the C-P system; mean values of 40Ar/36Ar: 1125) are definitely distinguished from the oil-type gases (The source rocks are of the Tertiary system; mean values of 40Ar/36Ar: 590) in the Tertiary reservoirs of the Zhongyuan Oilfield. Besides, 40Ar/36Ar values also have a positive effect on the oil-source correlation of oil reservoirs in ancient hidden mountains. According to the crust-mantle interchange information reflected by 3He/4He values, petroliferous provinces in China can be divided into three major tectonic regions. (1) The eastern active region: The crust-mantle volatile matter exchanges actively, and the 3He/4He values are mainly around 10-6, partly around 10-7. (2) The central stable region: The 3He/4He values are all around 10-8. (3) The western sub-stable region: The 3He/4He values are mainly around 10-8, and around 10-7 on the edges of the basins. Helium contents of some gas wells in China’s eastern petroliferous region reach the industrial abundance (He≈0.05%–0.1%), the 3He/4He values reach 10-6, and the equivalent values for the mantle-source components in helium gas can reach 30%–50%. As viewed from this, a new type of crust-mantle composite helium resources has been proposed. Geneses of some CO2 gas reservoirs in the east of China and some issues concerning mantle-source methane were discussed in the light of the helium and carbon isotopes of CO2 and CH4 in natural gases. In the discussion on helium isotopic characteristics of inclusions in the reservoirs, it was discovered that the 3He/4He values are close to those in natural gases. That is to say, this phenomenon is related to regional tectonism. The 3He/4He, CO2/3He and CH4/3He data were used to discuss the tectonic activities of fault zones in a certain number of regions in China.展开更多
The natural gas generation process is simulated by heating source rocks of the Yacheng Formation, including the onshore-offshore mudstone and coal with kerogens of Type II2-III in the Qiongdongnan Basin. The aim is to...The natural gas generation process is simulated by heating source rocks of the Yacheng Formation, including the onshore-offshore mudstone and coal with kerogens of Type II2-III in the Qiongdongnan Basin. The aim is to quantify the natural gas generation from the Yacheng Formation and to evaluate the geological prediction and kinetic parameters using an optimization procedure based on the basin modeling of the shallow-water area. For this, the hydrocarbons produced have been grouped into four classes（C1, C2, C3 and C4-6）. The results show that the onset temperature of methane generation is predicted to occur at 110℃ during the thermal history of sediments since 5.3 Ma by using data extrapolation. The hydrocarbon potential for ethane, propane and heavy gaseous hydrocarbons（C4-6） is found to be almost exhausted at geological temperature of 200℃ when the transformation ratio（TR） is over 0.8, but for which methane is determined to be about 0.5 in the shallow-water area. In contrast, the end temperature of the methane generation in the deep-water area was over 300℃ with a TR over 0.8. It plays an important role in the natural gas exploration of the deep-water basin and other basins in the broad ocean areas of China. Therefore, the natural gas exploration for the deep-water area in the Qiongdongnan Basin shall first aim at the structural traps in the Ledong, Lingshui and Beijiao sags, and in the forward direction of the structure around the sags, and then gradually develop toward the non-structural trap in the deep-water area basin of the broad ocean areas of China.展开更多
As compared to the device developed by our predecessors, the newly developed adsorbed gas degasification-collection device has a series of advantages such as wide sample application range, large sample inlet, high vac...As compared to the device developed by our predecessors, the newly developed adsorbed gas degasification-collection device has a series of advantages such as wide sample application range, large sample inlet, high vacuum, short-time sample smashing, low crushing temperature and water-free gas collection, which ensure the geochemical characteristics of acquired adsorbed gas samples to be the same as those of the adsorbed gases on corresponding hydrocarbon-source rocks. The results showed that the acquired adsorbed gases are composed mainly of hydrocarbon gas and carbon dioxide gas, with the hydrocarbon gas accounting for more than 80%, and can be measured reliably for their δ13C1-δ13C3 data, even δ13C4-δ13C5 data. The results of carbon isotope test and analysis satisfy the needs for the geochemical study and application of adsorbed gases. The above new techniques of experimental geochemistry are helpful for establishing the new direct natural gas-source correlation method, proving that the previous usual method of indirect natural gas-source correlation is scientific and authentic, thus providing the experimental basis for the study and application of adsorbed gases on hydrocarbon-source rocks.展开更多
No natural gas pool of industrial importance could be formed at the low-evolution stage of organic matter. In the 1980s, on the basis of the development in exploration practice, the hypotheses of bio-thermo-catalytic ...No natural gas pool of industrial importance could be formed at the low-evolution stage of organic matter. In the 1980s, on the basis of the development in exploration practice, the hypotheses of bio-thermo-catalytic transitional zone gases and early thermogenic gases were proposed. The lower-limit Ro values for the formation and accumulation of natural gases of industrial importance have been expanded to 0.3%―0.4%. In the light of the two-stage model established on the basis of carbon isotope fractionation in coal-type natural gases, the upper-limit Ro values have been set at 0.8%―1.0%. In terms of the geological practice in the low-mature gas zones and China's main coal-type gas fields, it is feasible and proper to set the upper-limit Ro value of low-mature gases at 0.8%. Supper-large gas fields such as the Urengoy gas field in western Siberian Basin should belong to low-mature gas fields, of which the natural gas reserves account for more than 20% of the global proven reserves, providing strong evidence for the significance of such a type of resources. The proven natural gas reserves in the Turpan-Hami Basin of China have almost reached 1000 × 108 m3. The main source rocks in this area are the Jurassic Xishanyao Formation, which occurs as a suite of coal series strata. The corresponding thermal evolution indices (Ro ) are mainly within the range of about 0.4%―0.8%, the δ 13C1 values of methane vary between-44‰ and-39‰ (correspondingly Ro =0.6%―0.8%), and those of ethane are within the range of-29‰―-26‰, indicating that natural gases in the Turpan-Hami Basin should be designated to coal-type low-mature gases. The light hydrocarbon evolution indices of natural gases also fall within the area of low evolution while the precursor type of light hydrocarbons also shows the characteristics of the coal-type. The geological background, carbon isotopic composition and light hydrocarbon index all provide strong evidence suggesting that the proven natural gases in the Turpan-Hami Basin are low-mature gases. In China a gas field with the gas reserves reaching 300 ×108 m3 can be defined as a large gas field, and thus the proven low-mature gases in the Turpan-Hami Basin are equivalent to the reserves of three large gas fields. Its existence is of great significance in research on and exploration of low-mature gases in China.展开更多
Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identif...Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas.Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses.The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane,high isoparaffin and low benzene.This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment.These features are consistent with the geological setting of the basin.Comparative studies of isoheptane,heptane,and the carbon isotopic compositions of methane in natural gases,and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams.The parent materials are of type III,and the maturation degree was in the low evolution stage.These are the fundamental characteristics of low-mature gas.Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China.It is likely that this resource will play an important role in future exploration and development of low-mature gas in China.展开更多
Isotopic composition characteristics and the significance of immature and low-mature oils are first systematically discussed. The carbon isotopes of the whole oil can be divided into two groups, one has δ13C main pea...Isotopic composition characteristics and the significance of immature and low-mature oils are first systematically discussed. The carbon isotopes of the whole oil can be divided into two groups, one has δ13C main peak values ranging from -30‰ to -29 and the other from -27‰ to -25‰, they are related to lacustrine and salt-lake facies or swamp facies, respectively. The carbon isotopic fractionation among different group components is relatively small, usually less than 2‰ and the biggest difference in fractionation often occurs between saturated and aromatic fractions. Their δD values vary between -180‰ and -130‰. The main peak of their δD values concentrates between -170‰ and -150‰, suggesting a domination of lacustrine facies. However, the secondary peak ranges from -160‰ to -150‰, showing a frequent salinization of paleo-water bodies. The average δ13C values of the methane vary between -50‰ and -52‰, about 10‰ lighter than those of mature oils. There is a relatively good展开更多
The influences of water media on the hydrogen isotopic composition of organic-thermogenic natural gas were tested in three series of experiments on coal pyrolysis, with no water, deionized water (δDH2O=?58‰), and se...The influences of water media on the hydrogen isotopic composition of organic-thermogenic natural gas were tested in three series of experiments on coal pyrolysis, with no water, deionized water (δDH2O=?58‰), and seawater (δDH2O=?4.8‰) added, respectively. The experimental results show that the productivities of H2 and CO2 obviously increased under hydrous condi tions and that the productivity of CH4 also remarkably increased in the high-evolution phase of hydrous experiments. Water was involved in the chemical reaction of hydrocarbon generation, and then the hydrogen isotopic composition of methane was affected. There is a linear correlation between the hydrogen isotopic composition of methane and its productivity, as reflected in the three series of experiments. In the case of the same CH4 productivity, the hydrogen isotopic composition of the methane produced in anhydrous experiments was the heaviest, that of the methane produced in seawater-adding experiments came se cond, and that of the methane produced in deionized water-adding experiments was the lightest. The hydrogen isotopic com position of natural gas/methane is affected by the following factors: 1) the characteristics of hydrogen isotopic composition of organic matter in source rocks, 2) the thermal evolution extent of organic matter, and 3) fossil-water media in the natural gas-generation period. The experimental results show that the influence of the fossil-water medium in the natural gas-generation period was lower than that of the other factors.展开更多
Study indicates that the elements rich in marine floor hydrothermal fluids have a positive in- fluence, not only on total organic carbon (TOC), but also on the abundance of SiO2 in some Middle-Upper Proterozoic strata...Study indicates that the elements rich in marine floor hydrothermal fluids have a positive in- fluence, not only on total organic carbon (TOC), but also on the abundance of SiO2 in some Middle-Upper Proterozoic strata. The TOC bears a better positive correlation with abundance of SiO2. By the correlation analysis between organic matter and sea-floor hot fluid characterized trace elements such as P, Cu, Zn, Ni, Ba, etc in marine carbonate rocks, we conclude that organic matter enrichment of carbonate rocks were related to marine floor hydrothermal activity in a part of layers. Some thin-layered cherts, which were thought to be the indicators of hydrothermal activity, frequently occurring in Gaoyuzhuang, Wumishan, Tieling and Xiamaling formation support our conclu- sion. With the increasing of trace elements in marine carbonate rocks, the TOC and Fe/Ti ratio is creasing. In contrast, the Al/(Al+Fe+Mn) ratio is usually de- creasing.展开更多
基金supported by the China National Key Basic Research and Development Program"973" (No.2009CB219506)
文摘Chemical and isotopic compositions have been measured for N2-He-rich bubbling gases discharging from hot springs in the Hainan Island, Southern China. Observed 3He/4He ratios （0.1-1.3 RA） indicate the occurrence of a mantle component throughout the island, which has been highly diluted by a crustal radiogenic 4He component. The occurrence of mantle-derived helium is high in the northern island （12%-16% of total He） and gradually decreases towards southern coast （1%-3% of total He）. Such a distribution pattern is most likely controlled by the Pleocene-Quaternary volcanic activities in the northern island and groundwater circulation along the deep major faults. The 4~Ar/36Ar and N2/Ar ratios suggest that N2 and Ar of the hot spring gases are mostly meteoric. Although 13C values of CO2 （-20%0 to -27%0） with low concentrations are consistent with the biogenic origin, the combination of SHe/4He and 51SCco2 suggests a two end-member mixing of mantle and crustal components with CO2/3He ratios of 2x 109 and 8 1011, respectively. However, the low CO2/3He ratios （1- 22106） can not be ascribed in terms of the simple mixing but has to be explained by the addition of radiogenic 4He and loss of CO2 by calcite precipitation in the hydrothermal system, which is most likely controlled by the degree of gas-water-rock interaction.
基金supported by the Chinese Natural Science Foundation Project (40673018)
文摘The age-accumulation effect of 40Ar in hydrocarbon source rocks was discussed in accordance with the decay law of radioactive elements. In terms of the mean values of 40Ar/36Ar, the old Sinian gas reservoirs (mean values of 40Ar/36Ar: 7009) were definitely distinguished from the Permian gas reservoirs (mean values of 40Ar/36Ar: 1017) in Weiyuan, Sichuan Province, and the gas source of the Permian gas reservoir (mean values of 40Ar/36Ar: 5222) in well Wei-7 with the Weiyuan structure is defined as the Sinian system. Based on the values of 40Ar/36Ar, the coal-type gases (The source rocks are of the C-P system; mean values of 40Ar/36Ar: 1125) are definitely distinguished from the oil-type gases (The source rocks are of the Tertiary system; mean values of 40Ar/36Ar: 590) in the Tertiary reservoirs of the Zhongyuan Oilfield. Besides, 40Ar/36Ar values also have a positive effect on the oil-source correlation of oil reservoirs in ancient hidden mountains. According to the crust-mantle interchange information reflected by 3He/4He values, petroliferous provinces in China can be divided into three major tectonic regions. (1) The eastern active region: The crust-mantle volatile matter exchanges actively, and the 3He/4He values are mainly around 10-6, partly around 10-7. (2) The central stable region: The 3He/4He values are all around 10-8. (3) The western sub-stable region: The 3He/4He values are mainly around 10-8, and around 10-7 on the edges of the basins. Helium contents of some gas wells in China’s eastern petroliferous region reach the industrial abundance (He≈0.05%–0.1%), the 3He/4He values reach 10-6, and the equivalent values for the mantle-source components in helium gas can reach 30%–50%. As viewed from this, a new type of crust-mantle composite helium resources has been proposed. Geneses of some CO2 gas reservoirs in the east of China and some issues concerning mantle-source methane were discussed in the light of the helium and carbon isotopes of CO2 and CH4 in natural gases. In the discussion on helium isotopic characteristics of inclusions in the reservoirs, it was discovered that the 3He/4He values are close to those in natural gases. That is to say, this phenomenon is related to regional tectonism. The 3He/4He, CO2/3He and CH4/3He data were used to discuss the tectonic activities of fault zones in a certain number of regions in China.
基金The Western Light Talent Culture Project of the Chinese Academy of Sciences under contract No.Y404RC1the National Petroleum Major Projects of China under contract No.2016ZX05026-007-005+2 种基金the Key Laboratory of Petroleum Resources Research Fund of the Chinese Academy of Sciences under contract No.KFJJ2013-04the Science and Technology Program of Gansu Province under contract No.1501RJYA006the Key Laboratory Project of Gansu Province of China under contract No.1309RTSA041
文摘The natural gas generation process is simulated by heating source rocks of the Yacheng Formation, including the onshore-offshore mudstone and coal with kerogens of Type II2-III in the Qiongdongnan Basin. The aim is to quantify the natural gas generation from the Yacheng Formation and to evaluate the geological prediction and kinetic parameters using an optimization procedure based on the basin modeling of the shallow-water area. For this, the hydrocarbons produced have been grouped into four classes（C1, C2, C3 and C4-6）. The results show that the onset temperature of methane generation is predicted to occur at 110℃ during the thermal history of sediments since 5.3 Ma by using data extrapolation. The hydrocarbon potential for ethane, propane and heavy gaseous hydrocarbons（C4-6） is found to be almost exhausted at geological temperature of 200℃ when the transformation ratio（TR） is over 0.8, but for which methane is determined to be about 0.5 in the shallow-water area. In contrast, the end temperature of the methane generation in the deep-water area was over 300℃ with a TR over 0.8. It plays an important role in the natural gas exploration of the deep-water basin and other basins in the broad ocean areas of China. Therefore, the natural gas exploration for the deep-water area in the Qiongdongnan Basin shall first aim at the structural traps in the Ledong, Lingshui and Beijiao sags, and in the forward direction of the structure around the sags, and then gradually develop toward the non-structural trap in the deep-water area basin of the broad ocean areas of China.
基金financially supported jointly by the National Natural Science Foundation of China (No. 41102090)the National Key Basic Research Planning Project (No.2012CB214801)the Important National Oil & Gas Special Project (No. 2011ZX05005-001)
文摘As compared to the device developed by our predecessors, the newly developed adsorbed gas degasification-collection device has a series of advantages such as wide sample application range, large sample inlet, high vacuum, short-time sample smashing, low crushing temperature and water-free gas collection, which ensure the geochemical characteristics of acquired adsorbed gas samples to be the same as those of the adsorbed gases on corresponding hydrocarbon-source rocks. The results showed that the acquired adsorbed gases are composed mainly of hydrocarbon gas and carbon dioxide gas, with the hydrocarbon gas accounting for more than 80%, and can be measured reliably for their δ13C1-δ13C3 data, even δ13C4-δ13C5 data. The results of carbon isotope test and analysis satisfy the needs for the geochemical study and application of adsorbed gases. The above new techniques of experimental geochemistry are helpful for establishing the new direct natural gas-source correlation method, proving that the previous usual method of indirect natural gas-source correlation is scientific and authentic, thus providing the experimental basis for the study and application of adsorbed gases on hydrocarbon-source rocks.
基金the Leading Scientific Research Project "The Rules of Accumulation of Low-mature Gases and Biogenic Gases and Techniques for Resource Assessment" undertaken by PetroChina Company Limited
文摘No natural gas pool of industrial importance could be formed at the low-evolution stage of organic matter. In the 1980s, on the basis of the development in exploration practice, the hypotheses of bio-thermo-catalytic transitional zone gases and early thermogenic gases were proposed. The lower-limit Ro values for the formation and accumulation of natural gases of industrial importance have been expanded to 0.3%―0.4%. In the light of the two-stage model established on the basis of carbon isotope fractionation in coal-type natural gases, the upper-limit Ro values have been set at 0.8%―1.0%. In terms of the geological practice in the low-mature gas zones and China's main coal-type gas fields, it is feasible and proper to set the upper-limit Ro value of low-mature gases at 0.8%. Supper-large gas fields such as the Urengoy gas field in western Siberian Basin should belong to low-mature gas fields, of which the natural gas reserves account for more than 20% of the global proven reserves, providing strong evidence for the significance of such a type of resources. The proven natural gas reserves in the Turpan-Hami Basin of China have almost reached 1000 × 108 m3. The main source rocks in this area are the Jurassic Xishanyao Formation, which occurs as a suite of coal series strata. The corresponding thermal evolution indices (Ro ) are mainly within the range of about 0.4%―0.8%, the δ 13C1 values of methane vary between-44‰ and-39‰ (correspondingly Ro =0.6%―0.8%), and those of ethane are within the range of-29‰―-26‰, indicating that natural gases in the Turpan-Hami Basin should be designated to coal-type low-mature gases. The light hydrocarbon evolution indices of natural gases also fall within the area of low evolution while the precursor type of light hydrocarbons also shows the characteristics of the coal-type. The geological background, carbon isotopic composition and light hydrocarbon index all provide strong evidence suggesting that the proven natural gases in the Turpan-Hami Basin are low-mature gases. In China a gas field with the gas reserves reaching 300 ×108 m3 can be defined as a large gas field, and thus the proven low-mature gases in the Turpan-Hami Basin are equivalent to the reserves of three large gas fields. Its existence is of great significance in research on and exploration of low-mature gases in China.
基金supported by the National Petroleum Major Projects (2008ZX05008-001)the National Natural Science Foundation of China (40703001)
文摘Theoretical and practical knowledge regarding low-mature gasses is of significant importance to identifying potential natural gas resources.Light hydrocarbon parameters and C and H isotopes are useful tools to identify low-mature gas.Twenty gas samples were collected from the Turpan-Hami Basin for light hydrocarbon analyses.The results showed that the light hydrocarbon components of natural gases contain high methylcycloxane,high isoparaffin and low benzene.This implies that the gas-generating parent materials are of typical humus type and the paleoenvironment is a fresh water sedimentary environment.These features are consistent with the geological setting of the basin.Comparative studies of isoheptane,heptane,and the carbon isotopic compositions of methane in natural gases,and other maturity indices indicated that natural gases in the Turpan-Hami Basin are dominated by low-mature gas formed during the low evolution stage of Jurassic coal seams.The parent materials are of type III,and the maturation degree was in the low evolution stage.These are the fundamental characteristics of low-mature gas.Results of light hydrocarbon research provided further evidence to suggest that the Turpan-Hami Basin is a large-scale gas producer of low-mature gas in China.It is likely that this resource will play an important role in future exploration and development of low-mature gas in China.
基金This work was supported by the China Petroleum & National Gas Limited Corp. (Project No. 960006) the National Natural Science Foundation of China (Grant No. 49973010).
文摘Isotopic composition characteristics and the significance of immature and low-mature oils are first systematically discussed. The carbon isotopes of the whole oil can be divided into two groups, one has δ13C main peak values ranging from -30‰ to -29 and the other from -27‰ to -25‰, they are related to lacustrine and salt-lake facies or swamp facies, respectively. The carbon isotopic fractionation among different group components is relatively small, usually less than 2‰ and the biggest difference in fractionation often occurs between saturated and aromatic fractions. Their δD values vary between -180‰ and -130‰. The main peak of their δD values concentrates between -170‰ and -150‰, suggesting a domination of lacustrine facies. However, the secondary peak ranges from -160‰ to -150‰, showing a frequent salinization of paleo-water bodies. The average δ13C values of the methane vary between -50‰ and -52‰, about 10‰ lighter than those of mature oils. There is a relatively good
基金supported jointly by National Natural Science Foundation of China (Grant No. 40703001) the "Western Doctors’ Project under the Western Light Program" sponsored by the Chinese Academy of Sciences
文摘The influences of water media on the hydrogen isotopic composition of organic-thermogenic natural gas were tested in three series of experiments on coal pyrolysis, with no water, deionized water (δDH2O=?58‰), and seawater (δDH2O=?4.8‰) added, respectively. The experimental results show that the productivities of H2 and CO2 obviously increased under hydrous condi tions and that the productivity of CH4 also remarkably increased in the high-evolution phase of hydrous experiments. Water was involved in the chemical reaction of hydrocarbon generation, and then the hydrogen isotopic composition of methane was affected. There is a linear correlation between the hydrogen isotopic composition of methane and its productivity, as reflected in the three series of experiments. In the case of the same CH4 productivity, the hydrogen isotopic composition of the methane produced in anhydrous experiments was the heaviest, that of the methane produced in seawater-adding experiments came se cond, and that of the methane produced in deionized water-adding experiments was the lightest. The hydrogen isotopic com position of natural gas/methane is affected by the following factors: 1) the characteristics of hydrogen isotopic composition of organic matter in source rocks, 2) the thermal evolution extent of organic matter, and 3) fossil-water media in the natural gas-generation period. The experimental results show that the influence of the fossil-water medium in the natural gas-generation period was lower than that of the other factors.
文摘Study indicates that the elements rich in marine floor hydrothermal fluids have a positive in- fluence, not only on total organic carbon (TOC), but also on the abundance of SiO2 in some Middle-Upper Proterozoic strata. The TOC bears a better positive correlation with abundance of SiO2. By the correlation analysis between organic matter and sea-floor hot fluid characterized trace elements such as P, Cu, Zn, Ni, Ba, etc in marine carbonate rocks, we conclude that organic matter enrichment of carbonate rocks were related to marine floor hydrothermal activity in a part of layers. Some thin-layered cherts, which were thought to be the indicators of hydrothermal activity, frequently occurring in Gaoyuzhuang, Wumishan, Tieling and Xiamaling formation support our conclu- sion. With the increasing of trace elements in marine carbonate rocks, the TOC and Fe/Ti ratio is creasing. In contrast, the Al/(Al+Fe+Mn) ratio is usually de- creasing.
