The sources and enrichment of organic matter in a sediment core in the first member of the Xiagou Formation(K_1g^1) from the Chang 2-2 borehole of the Jiuquan Basin,NW China,have been examined using Rock-Eval,maceral,...The sources and enrichment of organic matter in a sediment core in the first member of the Xiagou Formation(K_1g^1) from the Chang 2-2 borehole of the Jiuquan Basin,NW China,have been examined using Rock-Eval,maceral,carbon isotopes and biomarker data.This data indicates that highly variable organic matter sources and preservation conditions in response to climate change.TOC content,HI,and δ^(13)C value were strongly correlated with the abundance of gammacerane,woody organic matter content,steranes/hopanes ratio,and C_(29) sterane content.This correlation demonstrates the importance that the control of the salinity of the depositional environment and organic matter sources can have upon the enrichment,type,and carbon isotopic composition of organic matter.In the Jiuquan Basin's relatively high temperature and arid climate,high salinity lakes with high primary productivity of algae,planktons,and bacteria,and good organic matter preservation conditions(anoxic bottom water) resulted in the enrichment of isotopically-light algae-bacterial organic matter.In the Jiuquan Basin's regions with a relatively low temperature and wet climate,fresh lakes with low primary productivity of algae,planktons,and bacteria received significant terrigenous high plants input,resulting in the deposition of a low abundance of isotopically heavier terrestrial organic matter.展开更多
The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drill...The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor mi-neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential. Other applications of the S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.展开更多
Gypsum-salt rocks and coccolith calcareous shale are widely deposited in the lower part of the Paleogene Shahejie Formation in the Dongying Sag, Sbandong Province. The gypsum-salt rock is believed to be formed during ...Gypsum-salt rocks and coccolith calcareous shale are widely deposited in the lower part of the Paleogene Shahejie Formation in the Dongying Sag, Sbandong Province. The gypsum-salt rock is believed to be formed during the earlier deposition in salt lake, while the overlying coccolith shale in saline lake with relatively low salinity. By comparing the lake environment and la- custrine microbial communities between ancient and recent lakes, cyanobacteria are regarded as the main representative of productivity during the formation of gypsum-salt strata series, with the annual productivity of 1500-2000 gC m-2 yr1. Based on the research of ultramicrofossils in the calcareous shale, coccolith is considered as the main contributor to the productivity during the formation of calcareous shale. On the basis of statistic data of sedimentary rates, shale laminations, and coccolith fossils in each lamination, the quantitative value of productivity is calculated, with the annual productivity of 2250 3810 gC m 2 yr-1 （averagely 3120 gC m-2 yr-1）. Statistic data of large amount of pyrite framboids indicate that the lower water col- umn was persistently in sulfidic or anoxic conditions during the deposition of gypsum-salt strata series, but it changed to be dysoxic when the coccolith calcareous shale was deposited. Both of these water conditions are favorable for the preservation of organic matter. It is estimated that the organic carbon burial efficiency of the Lower Paleogene salt lakes and saline lakes of Dongying Depression is about 10%-15%, which is calculated and analyzed using the multi-parameter geobiological model.展开更多
基金financially supported by CNPC Major Science and Technology Project (NO. 2012E330)CNPC Fourth Petroleum Resources Assessment (NO. 2013E-050209)
文摘The sources and enrichment of organic matter in a sediment core in the first member of the Xiagou Formation(K_1g^1) from the Chang 2-2 borehole of the Jiuquan Basin,NW China,have been examined using Rock-Eval,maceral,carbon isotopes and biomarker data.This data indicates that highly variable organic matter sources and preservation conditions in response to climate change.TOC content,HI,and δ^(13)C value were strongly correlated with the abundance of gammacerane,woody organic matter content,steranes/hopanes ratio,and C_(29) sterane content.This correlation demonstrates the importance that the control of the salinity of the depositional environment and organic matter sources can have upon the enrichment,type,and carbon isotopic composition of organic matter.In the Jiuquan Basin's relatively high temperature and arid climate,high salinity lakes with high primary productivity of algae,planktons,and bacteria,and good organic matter preservation conditions(anoxic bottom water) resulted in the enrichment of isotopically-light algae-bacterial organic matter.In the Jiuquan Basin's regions with a relatively low temperature and wet climate,fresh lakes with low primary productivity of algae,planktons,and bacteria received significant terrigenous high plants input,resulting in the deposition of a low abundance of isotopically heavier terrestrial organic matter.
文摘The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor mi-neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential. Other applications of the S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.
基金supported by National Science and Technology Major Project (Grant No. 2009ZX05009)National Basic Research Program of China (Grant No. 2011CB808800)+1 种基金National Natural Science Foundation of China (Grant Nos. 41172036, 40730209)the "111" Project (Grant No. B08030)
文摘Gypsum-salt rocks and coccolith calcareous shale are widely deposited in the lower part of the Paleogene Shahejie Formation in the Dongying Sag, Sbandong Province. The gypsum-salt rock is believed to be formed during the earlier deposition in salt lake, while the overlying coccolith shale in saline lake with relatively low salinity. By comparing the lake environment and la- custrine microbial communities between ancient and recent lakes, cyanobacteria are regarded as the main representative of productivity during the formation of gypsum-salt strata series, with the annual productivity of 1500-2000 gC m-2 yr1. Based on the research of ultramicrofossils in the calcareous shale, coccolith is considered as the main contributor to the productivity during the formation of calcareous shale. On the basis of statistic data of sedimentary rates, shale laminations, and coccolith fossils in each lamination, the quantitative value of productivity is calculated, with the annual productivity of 2250 3810 gC m 2 yr-1 （averagely 3120 gC m-2 yr-1）. Statistic data of large amount of pyrite framboids indicate that the lower water col- umn was persistently in sulfidic or anoxic conditions during the deposition of gypsum-salt strata series, but it changed to be dysoxic when the coccolith calcareous shale was deposited. Both of these water conditions are favorable for the preservation of organic matter. It is estimated that the organic carbon burial efficiency of the Lower Paleogene salt lakes and saline lakes of Dongying Depression is about 10%-15%, which is calculated and analyzed using the multi-parameter geobiological model.
