Based on the interpretation of high resolution 2D/3D seismic data, sedimentary filling characteristics and full- filled time of the Central Canyon in different segments in the Qiongdongnan Basin of northwestern South ...Based on the interpretation of high resolution 2D/3D seismic data, sedimentary filling characteristics and full- filled time of the Central Canyon in different segments in the Qiongdongnan Basin of northwestern South China Sea have been studied. The research results indicate that the initial formation age of the Central Canyon is traced back to 11.6 Ma （T40）, at which the canyon began to develop due to the scouring of turbidity currents from west to east. During the period of 11.6-8.2 Ma （T40-T31）, strong downcutting by gravity flow occurred, which led to the formation of the canyon. The canyon fillings began to form since 8.2 Ma （T31） and were dominated by turbidite deposits, which constituted of lateral migration and vertical superposition of turbidity channels during the time of 8.2-5.5 Ma. The interbeds of turbidity currents deposits and mass transport deposits （MTDs） were developed in the period of 5.5-3.8 Ma （T30-T28）. After then, the canyon fillings were primarily made up of large scale MTDs, interrupted by small scale turbidity channels and thin pelagic mudstones. The Central Canyon can be divided into three types according to the main controlling factors, geomorphology-controlled, fault-controlled and intrusion- modified canyons. Among them, the geomorphology-controlled canyon is developed at the Ledong, Lingshui, Songnan and western Baodao Depressions, situated in a confined basin center between the northern slope and the South Uplift Belt along the Central Depression Belt. The fault-controlled canyon is developed mainly along the deep-seated faults in the Changchang Depression and eastern Baodao Depression. Intrusion-modified canyon is only occurred in the Songnan Low Uplift, which is still mainly controlled by geomorphology, the intrusion just modified seabed morphology. The full-filled time of the Central Canyon differs from west to east, displaying a tendency of being successively late eastward. The geomorphology-controlled canyon was completely filled before 3.8 Ma （T28）, but that in intrusion-modified canyon was delayed to 2.4 Ma （T27） because of the uplifted southern canyon wall. To the Changchang Depression, the complete filling time was successively late eastward, and the canyon in eastern Changchang Depression is still not fully filled up to today. Difference in full-filled time in the Central Canyon is mainly governed by multiple sediment supplies and regional tectonic activities. Due to sufficient supply of turbidity currents and MTDs from west and north respectively, western segment of the Central Canyon is entirely filled up earlier. Owing to slower sediment supply rate, together with differential subsidence by deep-seated faults, the full-filled time of the canyon is put off eastwards gradually.展开更多
Deep-water canyon systems can provide important sandstone reservoirs for deep-water oil and gas exploration in the South China Sea;however,the sedimentary provenance of the Central Canyon in the Qiongdongnan Basin rem...Deep-water canyon systems can provide important sandstone reservoirs for deep-water oil and gas exploration in the South China Sea;however,the sedimentary provenance of the Central Canyon in the Qiongdongnan Basin remains controversial.In this work,detrital zircon grains from three drilling sandstones in the Upper Miocene Huangliu Formation in the western part of the Central Canyon were analysed by LA-ICP-MS for U-Pb ages,in order to constrain their provenance.One hundred and ninety-one zircon grains yield concordant U-Pb ages ranging from 28.6 to 3285 Ma.Most of them show oscillatory or linear zoning in CL-images and high Th/U ratios(>0.1),suggesting that they are magmatic zircons.Three major age clusters at about30 Ma(N=6),220–270 Ma(N=29),and 420–440 Ma(N=13),and five minor age clusters at 70–110 Ma(N=7),150–170 Ma(N=4),800–850 Ma(N=11),1800–2000 Ma(N=16),and 2400–2600 Ma(N=7),can be identified in the age spectrum,which are very similar to those of the Upper Miocene sandstones and modern river sands in the Red River area,but different from those of other nearby regions(e.g.,Hainan Island,the Pearl River area,and the Mekong River area)in Southeast Asia.The major age peak at about 30 Ma in our samples is consistent with the timing of tectonothermal events in the Red River Fault Zone.Therefore,we suggest that the provenance of the western part of the Central Canyon,in the Qiongdongnan Basin,was fed dominantly by the Paleo-Red River system during the Late Miocene.展开更多
This study elucidates sedimentary evolution history of the Central Canyon System(CCS),a large axial submarine canyon in the Qiongdongnan Basin(QDNB),northern South China Sea.Thegeomorphological characteristics and inf...This study elucidates sedimentary evolution history of the Central Canyon System(CCS),a large axial submarine canyon in the Qiongdongnan Basin(QDNB),northern South China Sea.Thegeomorphological characteristics and infill architectures of the CCS are summarized based on theanalysis of two-and three-dimensional seismic data.Based on a comparative analysis of the CCS indifferent segments and evolutionary stages and in consideration of the tectono-sedimentary conditionsof the QDNB four stages of the sedimentary evolution of the CCS can be divided,i.e.initialdevelopment stage in the Late Miocene(11.6-5.7Ma),erosion-infilling stage in the Early Pliocene(5.7-3.7 Ma),tranquil infilling stage in the Late Pliocene(3.7-1.81 Ma),and rejuvenation stage sincethe Pleistocene(1.81 Ma to present).In the 1ate Middle Miocene(~11.6 Ma),the rudiment of CCswas developed by a regional tectonic transformation in the eastern part of the basin.In the EarlyPliocene,the CCS was further developed from west to east and restrained in the central depressionbelt of the basin due to abundant sediment supplies from the northwestern and northem provenances,the blocking effect of the southern uplift belt,and the restrictive geomorphological features of theeastern part of the basin.In the Late Pliocene,changes in the sedimentary environment resulted in thedevelopment of the CCS in the eastern part of the basin only.Since the Pleistocene,the joint action ofclimatic factors and geomorphological features of the eastern part of the basin led to the rejuvenationof the CCS.展开更多
The deepwater of the northwestern South China Sea is located in the central to southern parts of the Qiongdongnan Basin （QDN Basin）, which is a key site for hydrocarbon exploration in recent years. In this study, th...The deepwater of the northwestern South China Sea is located in the central to southern parts of the Qiongdongnan Basin （QDN Basin）, which is a key site for hydrocarbon exploration in recent years. In this study, the authors did a comprehensive analysis of gravity-magnetic data, extensive 3D seismic survey, cores and cuttings, paleontology and geochemical indexes, proposed the mechanism of natural gas origin, identified different oil and gas systems, and established the model of hydrocarbon accumulations in the deep-water region. Our basin tectonic simulation indicates that the evolution of QDN Basin was controlled by multiple-phased tectonic movements, such as Indochina-Eurasian Plate collision, Tibetan Uplift, Red River faulting and the expansion of the South China Sea which is characterized by Paleogene rifting, Neogene depression, and Eocene intensive faulting and lacustrine deposits. The drilling results show that this region is dominated by marine- terrestrial transitional and neritic-bathyal facies from the early Oligocene. The Yacheng Formation of the early Oligocene is rich in organic matter and a main gas-source rock. According to the geological-geochemical data from the latest drilling wells, Lingshui, Baodao, Changchang Sags have good hydrocarbon-generating potentials, where two plays from the Paleogene and Neogene reservoirs were developed. Those reservoirs occur in central canyon structural-lithologic trap zone, Changchang marginal trap zone and southern fault terrace of Baodao Sag. Among them, the central canyon trap zone has a great potential for exploration because the various reservoir- forming elements are well developed, i.e., good coal-measure source rocks, sufficient reservoirs from the Neogene turbidity sandstone and submarine fan, faults connecting source rock and reservoirs, effective vertical migration, late stage aggregation and favorable structural-lithological composite trapping. These study results provide an important scientific basis for hydrocarbon exploration in this region, evidenced by the recent discovery of the significant commercial LS-A gas field in the central canyon of the Lingshui Sag.展开更多
Over the past several years, a number of hydrocarbon reservoirs have been discovered in the deepwater area of Qiongdongnan Basin, northwestern South China Sea. These oil/gas fields demonstrate that the evolution of th...Over the past several years, a number of hydrocarbon reservoirs have been discovered in the deepwater area of Qiongdongnan Basin, northwestern South China Sea. These oil/gas fields demonstrate that the evolution of the deepwater sedimentary environment are controlling the formation and distribution of large-scale clastic reservoirs. Integration between seismic and borehole data were necessary to best clarify the distribution and quality of these deepwater reservoirs. Geochemical and paleobiological evidence from discrete samples was also applied to document specific information regarding the sedimentary environment. Results show that the Qiongdongnan Basin has existed as a thriving marine environment since Oligocene, when several rifting depressions developed throughout the entire Qiongdongnan Basin. Triggered by the faults activities, several distinct provenances supplied the coarse sediments, transporting and depositing them in deep parts of the rifting depressions. A fan delta system then formed nearby the source in the deeper area of these rifting depressions. The sedimentary environment of Qiongdongnan gradiationally became deepwater since early Miocene. Consequently, abundances of sediments were transported from Hainan Island and Southern Uplift, and then sunk into the basin center. The submarine fans revealed by many boreholes in this area verified them as good reservoir. Because the area reached its lowest sea level at late Miocene and the Southern Uplift subsidenced under sea level, not providing any sediment, so that the carbonate mesa and biorhythms characteristic of this area also developed during this period. In the west part of Qiongdongnan Basin, sediments transported from Vietnam increased in response to the Tibetan Uplift. Consequently, a central canyon developed along the center of Qiongdongnan Basin, which has been confirmed by several boreholes as a favorable hydrocarbon reservoir. The clarification of the deepwater sedimentary environment’s evolution is potentially highly beneficial to future hydrocarbon exploration in the deepwater area of Qiongdongnan Basin.展开更多
基金The National Natural Science Foundation of China under contract Nos 41372112 and 91028009the National Key Projects of Oil and Gas under contract No.2011ZX05025-002-02the Open Fund of Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences),Ministry of Education under contract No.TPR-2012-05
文摘Based on the interpretation of high resolution 2D/3D seismic data, sedimentary filling characteristics and full- filled time of the Central Canyon in different segments in the Qiongdongnan Basin of northwestern South China Sea have been studied. The research results indicate that the initial formation age of the Central Canyon is traced back to 11.6 Ma （T40）, at which the canyon began to develop due to the scouring of turbidity currents from west to east. During the period of 11.6-8.2 Ma （T40-T31）, strong downcutting by gravity flow occurred, which led to the formation of the canyon. The canyon fillings began to form since 8.2 Ma （T31） and were dominated by turbidite deposits, which constituted of lateral migration and vertical superposition of turbidity channels during the time of 8.2-5.5 Ma. The interbeds of turbidity currents deposits and mass transport deposits （MTDs） were developed in the period of 5.5-3.8 Ma （T30-T28）. After then, the canyon fillings were primarily made up of large scale MTDs, interrupted by small scale turbidity channels and thin pelagic mudstones. The Central Canyon can be divided into three types according to the main controlling factors, geomorphology-controlled, fault-controlled and intrusion- modified canyons. Among them, the geomorphology-controlled canyon is developed at the Ledong, Lingshui, Songnan and western Baodao Depressions, situated in a confined basin center between the northern slope and the South Uplift Belt along the Central Depression Belt. The fault-controlled canyon is developed mainly along the deep-seated faults in the Changchang Depression and eastern Baodao Depression. Intrusion-modified canyon is only occurred in the Songnan Low Uplift, which is still mainly controlled by geomorphology, the intrusion just modified seabed morphology. The full-filled time of the Central Canyon differs from west to east, displaying a tendency of being successively late eastward. The geomorphology-controlled canyon was completely filled before 3.8 Ma （T28）, but that in intrusion-modified canyon was delayed to 2.4 Ma （T27） because of the uplifted southern canyon wall. To the Changchang Depression, the complete filling time was successively late eastward, and the canyon in eastern Changchang Depression is still not fully filled up to today. Difference in full-filled time in the Central Canyon is mainly governed by multiple sediment supplies and regional tectonic activities. Due to sufficient supply of turbidity currents and MTDs from west and north respectively, western segment of the Central Canyon is entirely filled up earlier. Owing to slower sediment supply rate, together with differential subsidence by deep-seated faults, the full-filled time of the canyon is put off eastwards gradually.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41372112, 91028009)the National Key Projects of Oil and Gas (Grant No. 2011ZX05025-002-02)+1 种基金the Programme of Introducing Talents of Discipline to Universities (Grant No. B14031)the Open Fund of the Key Laboratory of Marine Geology and Environment, China Academy of Sciences (Grant No. MGE2013KG02)
文摘Deep-water canyon systems can provide important sandstone reservoirs for deep-water oil and gas exploration in the South China Sea;however,the sedimentary provenance of the Central Canyon in the Qiongdongnan Basin remains controversial.In this work,detrital zircon grains from three drilling sandstones in the Upper Miocene Huangliu Formation in the western part of the Central Canyon were analysed by LA-ICP-MS for U-Pb ages,in order to constrain their provenance.One hundred and ninety-one zircon grains yield concordant U-Pb ages ranging from 28.6 to 3285 Ma.Most of them show oscillatory or linear zoning in CL-images and high Th/U ratios(>0.1),suggesting that they are magmatic zircons.Three major age clusters at about30 Ma(N=6),220–270 Ma(N=29),and 420–440 Ma(N=13),and five minor age clusters at 70–110 Ma(N=7),150–170 Ma(N=4),800–850 Ma(N=11),1800–2000 Ma(N=16),and 2400–2600 Ma(N=7),can be identified in the age spectrum,which are very similar to those of the Upper Miocene sandstones and modern river sands in the Red River area,but different from those of other nearby regions(e.g.,Hainan Island,the Pearl River area,and the Mekong River area)in Southeast Asia.The major age peak at about 30 Ma in our samples is consistent with the timing of tectonothermal events in the Red River Fault Zone.Therefore,we suggest that the provenance of the western part of the Central Canyon,in the Qiongdongnan Basin,was fed dominantly by the Paleo-Red River system during the Late Miocene.
基金This work was funded by the Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology,Ministry of Land and Resources(MRE201305)the Key Laboratory of Marine Geology and Environment,China Academy of Sciencess(MGE2013KG02).
文摘This study elucidates sedimentary evolution history of the Central Canyon System(CCS),a large axial submarine canyon in the Qiongdongnan Basin(QDNB),northern South China Sea.Thegeomorphological characteristics and infill architectures of the CCS are summarized based on theanalysis of two-and three-dimensional seismic data.Based on a comparative analysis of the CCS indifferent segments and evolutionary stages and in consideration of the tectono-sedimentary conditionsof the QDNB four stages of the sedimentary evolution of the CCS can be divided,i.e.initialdevelopment stage in the Late Miocene(11.6-5.7Ma),erosion-infilling stage in the Early Pliocene(5.7-3.7 Ma),tranquil infilling stage in the Late Pliocene(3.7-1.81 Ma),and rejuvenation stage sincethe Pleistocene(1.81 Ma to present).In the 1ate Middle Miocene(~11.6 Ma),the rudiment of CCswas developed by a regional tectonic transformation in the eastern part of the basin.In the EarlyPliocene,the CCS was further developed from west to east and restrained in the central depressionbelt of the basin due to abundant sediment supplies from the northwestern and northem provenances,the blocking effect of the southern uplift belt,and the restrictive geomorphological features of theeastern part of the basin.In the Late Pliocene,changes in the sedimentary environment resulted in thedevelopment of the CCS in the eastern part of the basin only.Since the Pleistocene,the joint action ofclimatic factors and geomorphological features of the eastern part of the basin led to the rejuvenationof the CCS.
基金China National Major Special Project under contract No.2011ZX05025-002
文摘The deepwater of the northwestern South China Sea is located in the central to southern parts of the Qiongdongnan Basin （QDN Basin）, which is a key site for hydrocarbon exploration in recent years. In this study, the authors did a comprehensive analysis of gravity-magnetic data, extensive 3D seismic survey, cores and cuttings, paleontology and geochemical indexes, proposed the mechanism of natural gas origin, identified different oil and gas systems, and established the model of hydrocarbon accumulations in the deep-water region. Our basin tectonic simulation indicates that the evolution of QDN Basin was controlled by multiple-phased tectonic movements, such as Indochina-Eurasian Plate collision, Tibetan Uplift, Red River faulting and the expansion of the South China Sea which is characterized by Paleogene rifting, Neogene depression, and Eocene intensive faulting and lacustrine deposits. The drilling results show that this region is dominated by marine- terrestrial transitional and neritic-bathyal facies from the early Oligocene. The Yacheng Formation of the early Oligocene is rich in organic matter and a main gas-source rock. According to the geological-geochemical data from the latest drilling wells, Lingshui, Baodao, Changchang Sags have good hydrocarbon-generating potentials, where two plays from the Paleogene and Neogene reservoirs were developed. Those reservoirs occur in central canyon structural-lithologic trap zone, Changchang marginal trap zone and southern fault terrace of Baodao Sag. Among them, the central canyon trap zone has a great potential for exploration because the various reservoir- forming elements are well developed, i.e., good coal-measure source rocks, sufficient reservoirs from the Neogene turbidity sandstone and submarine fan, faults connecting source rock and reservoirs, effective vertical migration, late stage aggregation and favorable structural-lithological composite trapping. These study results provide an important scientific basis for hydrocarbon exploration in this region, evidenced by the recent discovery of the significant commercial LS-A gas field in the central canyon of the Lingshui Sag.
基金The National Science and Technology Major Project of China under contract No.2011ZX05025-002-02the National Natural Science Foundation of China under contract Nos 41476032 and 41372112
文摘Over the past several years, a number of hydrocarbon reservoirs have been discovered in the deepwater area of Qiongdongnan Basin, northwestern South China Sea. These oil/gas fields demonstrate that the evolution of the deepwater sedimentary environment are controlling the formation and distribution of large-scale clastic reservoirs. Integration between seismic and borehole data were necessary to best clarify the distribution and quality of these deepwater reservoirs. Geochemical and paleobiological evidence from discrete samples was also applied to document specific information regarding the sedimentary environment. Results show that the Qiongdongnan Basin has existed as a thriving marine environment since Oligocene, when several rifting depressions developed throughout the entire Qiongdongnan Basin. Triggered by the faults activities, several distinct provenances supplied the coarse sediments, transporting and depositing them in deep parts of the rifting depressions. A fan delta system then formed nearby the source in the deeper area of these rifting depressions. The sedimentary environment of Qiongdongnan gradiationally became deepwater since early Miocene. Consequently, abundances of sediments were transported from Hainan Island and Southern Uplift, and then sunk into the basin center. The submarine fans revealed by many boreholes in this area verified them as good reservoir. Because the area reached its lowest sea level at late Miocene and the Southern Uplift subsidenced under sea level, not providing any sediment, so that the carbonate mesa and biorhythms characteristic of this area also developed during this period. In the west part of Qiongdongnan Basin, sediments transported from Vietnam increased in response to the Tibetan Uplift. Consequently, a central canyon developed along the center of Qiongdongnan Basin, which has been confirmed by several boreholes as a favorable hydrocarbon reservoir. The clarification of the deepwater sedimentary environment’s evolution is potentially highly beneficial to future hydrocarbon exploration in the deepwater area of Qiongdongnan Basin.
