The distribution of two formation pathways of biogenic methane, acetate fermentation and reduction of CO2, has been extensively studied. In general, CO2 reduction is the dominate pathway in marine envi- ronment where ...The distribution of two formation pathways of biogenic methane, acetate fermentation and reduction of CO2, has been extensively studied. In general, CO2 reduction is the dominate pathway in marine envi- ronment where acetate is relatively depleted because of SRB consuming. While in terrestrial freshwater or brackish environment, acetate fermentation is initially significant, but decreases with increasing buried depth. In this paper, character of biogenic gases is profiled in the XS3-4 well of the Sebei 1 gas field in the Sanhu depression, Qaidam Basin. It indicates that those two pathways do not change strictly with increasing buried depth. CO2 reduction is important near the surface (between 50 m and 160 m), and at the mesozone (between 400 and 1650 m). While acetate fermentation is the primary pathway at two zones, from 160 to 400 m and from 1650 to 1700 m. δ 13C of methane generated in those two acetate fermentation zones varies greatly, owing to different sediment circumstances. At the sec- ond zone (160-400 m), δ 13C1 ranges from ?65‰ to ?30‰ (PDB), because the main deposit is mudstone and makes the circumstance confined. At the fourth zone of the well bottom (1650-1700 m), δ 13C1 is lighter than ?65‰ (PDB). Because the deposit is mainly composed of siltstone, it well connects with outer fertile groundwater and abundant nutrition has supplied into this open system. The high con- centration of acetate is a forceful proof. δ 13C of methane would not turn heavier during fermentation, owing to enough nutrition supply. In spite of multi-occurrence of acetate fermentation, the commercial gas accumulation is dominated by methane of CO2-reduction pathway. A certain content of alkene gases in the biogenic gases suggests that methanogensis is still active at present.展开更多
To understand the biogas formation in geological basins, the present work investigated the reactive organic matter in sediments of the Sanhu depression of Qaidam Basin, a prolific region of biogenic gases with a prove...To understand the biogas formation in geological basins, the present work investigated the reactive organic matter in sediments of the Sanhu depression of Qaidam Basin, a prolific region of biogenic gases with a proved reserve of 300 bil steres. The ROC (reactive organic carbon) was obtained by ultrasonic extraction from sediment samples in the solution of 6 mol/L HCl and 5% K2SO4. To investigate the effect of early diagenesis, parts of the samples were heated at 80°C before extraction. The results showed that the ROC content at a constant temperature decreased with increasing burial depths, which should be attributed to the microbial consumption. For the same sample, the ROC content heated at 80°C was dramatically higher than the unheated. The increment of the ROC content for some samples was as high as 200% in the experiment. The dramatically increasing ROC by thermal action should be the major nutrient substrate for the deep biospheres in most geological basins. There is a positive correlation between the reactive organic carbon (ROC) and the traditional insoluble organic carbon (TOC), not only for its absolute content of the ROC, but also for the 'ROC' produced in thermal action, all of these are clearly related with TOC. These data showed that higher abundance of organic matter can contribute more to the reactive organic matter, and is more favorable to the formation of biogenic gases. In the Sanhu depression of Qaidam Basin, more than 85% of the biogenic gas reserves occur in the lower layers (K5-K13) with a relatively high abundance of organic matter. The exploration has provided further evidence that deposits with higher abundance of organic matter are effective biogas source rocks.展开更多
Emissions of biogenic sulfur gases(hydrogen sulfide(H_2S) and carbonyl sulfide(COS)) from Phragmites australis coastal marsh in the Yellow River estuary of China were determined during April to December in 2014 using ...Emissions of biogenic sulfur gases(hydrogen sulfide(H_2S) and carbonyl sulfide(COS)) from Phragmites australis coastal marsh in the Yellow River estuary of China were determined during April to December in 2014 using static chamber-gas chromatography technique with monthly sampling. The results showed that the fluxes of H_2S and COS both had distinct seasonal and diurnal variations. The H_2S fluxes ranged from 0.09 μg/(m^2·h) to 7.65 μg/(m^2·h), and the COS fluxes ranged from –1.10 μg/(m^2·h) to 3.32 μg/(m^2·h). The mean fluxes of H_2S and COS from the P. australis coastal marsh were 2.28 μg/(m^2·h), and 1.05 μg/(m^2·h), respectively. The P. australis coastal marsh was the emission source of both H_2S and COS over the whole year. Fluxes of H_2S and COS were both higher in plant growing season than in the non-growing season. Temperature had a dramatic effect on the H_2S emission flux, while the correlations between COS flux and the environmental factors were not found during sampling periods. More in-depth and comprehensive research on other related factors, such as vegetation, sediment substrates, and tidal action is needed to discover and further understand the key factors and the release mechanism of sulfur gases.展开更多
基金Supported by the National "973" Project (Grant No. 2001CB209101)the Chinese Postdoctoral Science Foundation (Grant No. 2005037419) the NFSC (Grant No. 40603015)
文摘The distribution of two formation pathways of biogenic methane, acetate fermentation and reduction of CO2, has been extensively studied. In general, CO2 reduction is the dominate pathway in marine envi- ronment where acetate is relatively depleted because of SRB consuming. While in terrestrial freshwater or brackish environment, acetate fermentation is initially significant, but decreases with increasing buried depth. In this paper, character of biogenic gases is profiled in the XS3-4 well of the Sebei 1 gas field in the Sanhu depression, Qaidam Basin. It indicates that those two pathways do not change strictly with increasing buried depth. CO2 reduction is important near the surface (between 50 m and 160 m), and at the mesozone (between 400 and 1650 m). While acetate fermentation is the primary pathway at two zones, from 160 to 400 m and from 1650 to 1700 m. δ 13C of methane generated in those two acetate fermentation zones varies greatly, owing to different sediment circumstances. At the sec- ond zone (160-400 m), δ 13C1 ranges from ?65‰ to ?30‰ (PDB), because the main deposit is mudstone and makes the circumstance confined. At the fourth zone of the well bottom (1650-1700 m), δ 13C1 is lighter than ?65‰ (PDB). Because the deposit is mainly composed of siltstone, it well connects with outer fertile groundwater and abundant nutrition has supplied into this open system. The high con- centration of acetate is a forceful proof. δ 13C of methane would not turn heavier during fermentation, owing to enough nutrition supply. In spite of multi-occurrence of acetate fermentation, the commercial gas accumulation is dominated by methane of CO2-reduction pathway. A certain content of alkene gases in the biogenic gases suggests that methanogensis is still active at present.
基金supported by National Natural Science Founda-tion of China (Grant Nos.40603015,40873031)Petro China Scientific Research and Technological Development Projects (Grant Nos.2008A-0608,07-01-C-01-07)Important National Science & Technology Specific Projects (Grant No.2008ZX05)
文摘To understand the biogas formation in geological basins, the present work investigated the reactive organic matter in sediments of the Sanhu depression of Qaidam Basin, a prolific region of biogenic gases with a proved reserve of 300 bil steres. The ROC (reactive organic carbon) was obtained by ultrasonic extraction from sediment samples in the solution of 6 mol/L HCl and 5% K2SO4. To investigate the effect of early diagenesis, parts of the samples were heated at 80°C before extraction. The results showed that the ROC content at a constant temperature decreased with increasing burial depths, which should be attributed to the microbial consumption. For the same sample, the ROC content heated at 80°C was dramatically higher than the unheated. The increment of the ROC content for some samples was as high as 200% in the experiment. The dramatically increasing ROC by thermal action should be the major nutrient substrate for the deep biospheres in most geological basins. There is a positive correlation between the reactive organic carbon (ROC) and the traditional insoluble organic carbon (TOC), not only for its absolute content of the ROC, but also for the 'ROC' produced in thermal action, all of these are clearly related with TOC. These data showed that higher abundance of organic matter can contribute more to the reactive organic matter, and is more favorable to the formation of biogenic gases. In the Sanhu depression of Qaidam Basin, more than 85% of the biogenic gas reserves occur in the lower layers (K5-K13) with a relatively high abundance of organic matter. The exploration has provided further evidence that deposits with higher abundance of organic matter are effective biogas source rocks.
基金National Nature Science Foundation of China(No.41103036)Natural Science Foundation of Shandong Province,China(No.BS2009HZ013)
文摘Emissions of biogenic sulfur gases(hydrogen sulfide(H_2S) and carbonyl sulfide(COS)) from Phragmites australis coastal marsh in the Yellow River estuary of China were determined during April to December in 2014 using static chamber-gas chromatography technique with monthly sampling. The results showed that the fluxes of H_2S and COS both had distinct seasonal and diurnal variations. The H_2S fluxes ranged from 0.09 μg/(m^2·h) to 7.65 μg/(m^2·h), and the COS fluxes ranged from –1.10 μg/(m^2·h) to 3.32 μg/(m^2·h). The mean fluxes of H_2S and COS from the P. australis coastal marsh were 2.28 μg/(m^2·h), and 1.05 μg/(m^2·h), respectively. The P. australis coastal marsh was the emission source of both H_2S and COS over the whole year. Fluxes of H_2S and COS were both higher in plant growing season than in the non-growing season. Temperature had a dramatic effect on the H_2S emission flux, while the correlations between COS flux and the environmental factors were not found during sampling periods. More in-depth and comprehensive research on other related factors, such as vegetation, sediment substrates, and tidal action is needed to discover and further understand the key factors and the release mechanism of sulfur gases.
