To get features of rare earth elements （REEs） fractionation, 106 surface sediment samples from eastern South China Sea were determined for REEs combined with major and trace elements by ICP-MS. The distribution patt...To get features of rare earth elements （REEs） fractionation, 106 surface sediment samples from eastern South China Sea were determined for REEs combined with major and trace elements by ICP-MS. The distribution pattern of REEs, strong correlation between REEs and Al, North American shale composite （NASC） normalization all suggest a dominant crustal source for REEs in the research area. However distinct fractionation among REEs was observed in surface sediment from area with water depth over 2000 m, confirmed by the strong positive correlation among light rare earth elements （LREEs） and among heavy rare earth elements （HREEs） but weaker relationship between LREEs and HREEs. Eluviation by Cl- might be a key role on the fiactionation of REEs, comparing with factors such as grain size, co-precipitation with Fe and Mn hydroxide, calcareous and siliceous biogenic precipitation. The fractionation among REEs could be used as index to illustrate the sedimentary environment in reverse.展开更多
Coal-type source rocks include both coal and terrigenous marine source rocks.By studying the distribution of secondary depressions,uplifts,as well as the characteristics of peat formation and accumulation in the north...Coal-type source rocks include both coal and terrigenous marine source rocks.By studying the distribution of secondary depressions,uplifts,as well as the characteristics of peat formation and accumulation in the northern marginal sea basin of the South China Sea,and combining them with coal formation characteristics observed in other basins,five genetic theories on the relationship between peat accumulation and dispersed organic matter accumulation are proposed.The northern marginal sea basin of the South China Sea is characterized by“disadvantageous coals formation and favorable terrigenous marine source rocks formation.”This paper provides a distribution map of coal seams and terrigenous marine source rocks in the Qiongdongnan Basin and determines their distribution patterns.Research shows that the migration of sedimentary facies in the basins and inner depressions led to the formation and migration of the peat accumulation centers.In addition,the vertical migration of the peat accumulation centers led to planar migration,which is actually a type of coupling relationship.Previous research results have revealed that the formation of coal-type source rock is multi-phased.The marginal sea basin is composed of several fault-depression basins,with each basin developing a second order of depression and uplift.There is no unified basin center or depositional center to be found.As a result,the concentration centers of coal-forming materials also vary greatly.Based on the distribution characteristics of coal-type source rocks in different basins within the marginal sea basins of the South China Sea,the research results have practical significance and provide guidance for exploring coal-type oil and gas reservoirs in this area.展开更多
Oligocene(fan)delta-associated coal measures and marine source rocks are the main gas-generating source rocks in the Qiongdongnan Basin,and(fan)delta sand bodies are the dominant types of reservoirs.By comprehensively...Oligocene(fan)delta-associated coal measures and marine source rocks are the main gas-generating source rocks in the Qiongdongnan Basin,and(fan)delta sand bodies are the dominant types of reservoirs.By comprehensively utilizing a large amount of 2D and 3D seismic data and new drilling data,the distribution of(fan)deltas and three types of Oligocene fault fan systems were systematically identified;these are thought to have had joint control over the development of hydrocarbon source rocks and reservoirs.The three types of Oligocene fault fan coupling relationships in the Qiongdongnan Basin were found to be fault bend,fault gully,and fault tip.The fault bend type of(fan)delta developed at the bend of the fault and was distributed in the downthrown block of Fault Nos.5 and 2.The fault tip type developed where the fault died out toward the source direction and was distributed near the eastewest faults on the north and south sides of Baodao and Changchang Sags.The fault gully type developed along the fault trend in the downthrown block and was mainly distributed in areas including the northern part of Ya'nan Sag and the Fault No.3 downthrown block.The fault bend(fan)delta is surrounded by a relatively closed bay environment,and the terrigenously dominated marine source rocks in the still water bay environment were developed with a high hydrocarbon generation index and high hydrocarbon generation potential.Fault tip and fault gully types of(fan)delta plain facies have a wide distribution of plain subfacies,which is conducive to the development of coal-measure source rocks that have excellent gas potential.During sedimentation of the fault gully and the fault tip delta,the terrain was relatively flat,with sand bodies strongly reworked by hydrodynamic force;the reservoir quality of the sand bodies in the underwater distributary channel and estuary dam are good,and the sand bodies have wide distribution.The sand bodies of the fault bend type of(fan)delta were deposited rapidly near the source kitchen,and the degree of sorting and rounding was poor,which resulted in the poor physical properties of the plain subfacies.In the southern and northern step-fault zones of Baodao Sag in the eastern part of this basin,the fault bend,fault tip,and fault trench(fan)deltas were inherited and further developed,and the source-reservoir configuration conditions were favorable.Exploration deployment was carried out in the Baodao 21 area in the northern step-fault zone and the Yongle 10 area in the southern step-fault zone,where new discoveries in natural gas exploration have been realized.In the eastern part of this basin,the fault bend,fault tip,and fault gully(fan)deltas in the southern and northern fault step zones of Baodao Sag were successively developed,which were beneficial for favorable sourceereservoir configuration conditions.The natural gas exploration successes in the Baodao-21 area in the northern fault step zone and the Yongle-10 area in the southern fault step zone are beneficial for new discoveries in natural gas exploration in the Qiongdongnan Basin.展开更多
基金National Basic Research Program of China(2006FY220400)National Natural Science Foundation of China(40706057)+1 种基金Natural Science Foundation of the Zhejiang Province(Y5100117)Zhejiang Provincial Department of Education Project(N20100420)
文摘To get features of rare earth elements （REEs） fractionation, 106 surface sediment samples from eastern South China Sea were determined for REEs combined with major and trace elements by ICP-MS. The distribution pattern of REEs, strong correlation between REEs and Al, North American shale composite （NASC） normalization all suggest a dominant crustal source for REEs in the research area. However distinct fractionation among REEs was observed in surface sediment from area with water depth over 2000 m, confirmed by the strong positive correlation among light rare earth elements （LREEs） and among heavy rare earth elements （HREEs） but weaker relationship between LREEs and HREEs. Eluviation by Cl- might be a key role on the fiactionation of REEs, comparing with factors such as grain size, co-precipitation with Fe and Mn hydroxide, calcareous and siliceous biogenic precipitation. The fractionation among REEs could be used as index to illustrate the sedimentary environment in reverse.
基金The National Natural Science Foundation of China under contract Nos 42072188,42272205 and 41872172。
文摘Coal-type source rocks include both coal and terrigenous marine source rocks.By studying the distribution of secondary depressions,uplifts,as well as the characteristics of peat formation and accumulation in the northern marginal sea basin of the South China Sea,and combining them with coal formation characteristics observed in other basins,five genetic theories on the relationship between peat accumulation and dispersed organic matter accumulation are proposed.The northern marginal sea basin of the South China Sea is characterized by“disadvantageous coals formation and favorable terrigenous marine source rocks formation.”This paper provides a distribution map of coal seams and terrigenous marine source rocks in the Qiongdongnan Basin and determines their distribution patterns.Research shows that the migration of sedimentary facies in the basins and inner depressions led to the formation and migration of the peat accumulation centers.In addition,the vertical migration of the peat accumulation centers led to planar migration,which is actually a type of coupling relationship.Previous research results have revealed that the formation of coal-type source rock is multi-phased.The marginal sea basin is composed of several fault-depression basins,with each basin developing a second order of depression and uplift.There is no unified basin center or depositional center to be found.As a result,the concentration centers of coal-forming materials also vary greatly.Based on the distribution characteristics of coal-type source rocks in different basins within the marginal sea basins of the South China Sea,the research results have practical significance and provide guidance for exploring coal-type oil and gas reservoirs in this area.
基金funded by the National Natural Science Foundation of China under contract number 91528303the National Science and Technology Major Project under contract numbers 2016ZX05026,2011ZX05025,and 2008ZX05025+1 种基金the National Basic Research Program(973 Program)of China under contract number 2009CB219400the Science and Technology Project of China National Offshore Oil Corporation under contract number KJGG2022-0101.
文摘Oligocene(fan)delta-associated coal measures and marine source rocks are the main gas-generating source rocks in the Qiongdongnan Basin,and(fan)delta sand bodies are the dominant types of reservoirs.By comprehensively utilizing a large amount of 2D and 3D seismic data and new drilling data,the distribution of(fan)deltas and three types of Oligocene fault fan systems were systematically identified;these are thought to have had joint control over the development of hydrocarbon source rocks and reservoirs.The three types of Oligocene fault fan coupling relationships in the Qiongdongnan Basin were found to be fault bend,fault gully,and fault tip.The fault bend type of(fan)delta developed at the bend of the fault and was distributed in the downthrown block of Fault Nos.5 and 2.The fault tip type developed where the fault died out toward the source direction and was distributed near the eastewest faults on the north and south sides of Baodao and Changchang Sags.The fault gully type developed along the fault trend in the downthrown block and was mainly distributed in areas including the northern part of Ya'nan Sag and the Fault No.3 downthrown block.The fault bend(fan)delta is surrounded by a relatively closed bay environment,and the terrigenously dominated marine source rocks in the still water bay environment were developed with a high hydrocarbon generation index and high hydrocarbon generation potential.Fault tip and fault gully types of(fan)delta plain facies have a wide distribution of plain subfacies,which is conducive to the development of coal-measure source rocks that have excellent gas potential.During sedimentation of the fault gully and the fault tip delta,the terrain was relatively flat,with sand bodies strongly reworked by hydrodynamic force;the reservoir quality of the sand bodies in the underwater distributary channel and estuary dam are good,and the sand bodies have wide distribution.The sand bodies of the fault bend type of(fan)delta were deposited rapidly near the source kitchen,and the degree of sorting and rounding was poor,which resulted in the poor physical properties of the plain subfacies.In the southern and northern step-fault zones of Baodao Sag in the eastern part of this basin,the fault bend,fault tip,and fault trench(fan)deltas were inherited and further developed,and the source-reservoir configuration conditions were favorable.Exploration deployment was carried out in the Baodao 21 area in the northern step-fault zone and the Yongle 10 area in the southern step-fault zone,where new discoveries in natural gas exploration have been realized.In the eastern part of this basin,the fault bend,fault tip,and fault gully(fan)deltas in the southern and northern fault step zones of Baodao Sag were successively developed,which were beneficial for favorable sourceereservoir configuration conditions.The natural gas exploration successes in the Baodao-21 area in the northern fault step zone and the Yongle-10 area in the southern fault step zone are beneficial for new discoveries in natural gas exploration in the Qiongdongnan Basin.
