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 futu展开更多
Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea ...Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea that includes Paleo SCS and New SCS tectonic cycles.The latter includes continental marginal rifting,intercontinental oceanic expansion and oceanic shrinking,which controlled the evolution of basins,and the generation,migration and accumulation of hydrocarbons in the deepwater basins on the continental margin of the northern SCS.In the Paleogene,the basins rifted along the margin of the continent and were filled mainly with sediments in marine-continental transitional environments.In the Neogene–Quaternary,due to thermal subsidence,neritic-abyssal facies sediments from the passive continental margin of the SCS mainly filled the basins.The source rocks include mainly Oligocene coal-bearing deltaic and marine mudstones,which were heated by multiple events with high geothermal temperature and terrestrial heat flow,resulting in the generation of gas and oil.The faults,diapirs and sandstones controlled the migration of hydrocarbons that accumulated principally in a large canyon channel,a continental deepwater fan,and a shelf-margin delta.展开更多
The mechanisms causing quality variations and key control factors of submarine-fan reservoirs in the gas field X of the Rovuma Basin,East Africa are analyzed based on core and well-log data in this paper.Depositional ...The mechanisms causing quality variations and key control factors of submarine-fan reservoirs in the gas field X of the Rovuma Basin,East Africa are analyzed based on core and well-log data in this paper.Depositional fabric,lithofacies difference and characteristics of genetic units are the fundamental reasons of reservoir quality variations.In the case of weak cementation,porosity and permeability of submarine-fan reservoirs are controlled by grain sorting and clay content,respectively.Reservoir quality variations for 5 main lithofacies are related to variable depositional fabrics and calcite cementation.Among them,massive medium-coarse sandstones with weak cementation have the highest porosity and permeability,and coarser or finer sandstones have poorer reservoir quality.The existence of bottom current can develop laminated sandstones,improving the pore structure and physical properties greatly.Lithofacies vary among different types,locations and stages of genetic units,and they control the distribution patterns of submarine-fan reservoir quality:the physical properties of channel shaft or lobe main body are better than those of the channel or lobe edge.The sandstone sorting and physical properties are gradually improved from near-source to far-source.When multi-stage sand bodies are superimposed,the sand-mud ratio in the later stage is higher than that in the earlier stage,making the physical properties get better in the later stage.展开更多
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 futu
基金supported by the National Science and Technology Major Project(Grant nos.2016ZX05026,2016ZX05026–007–007)the National Natural Science Foundation of China(Grant nos.91528303,41502127)+1 种基金the Opening Foundation of State Key Laboratory of Continental Dynamics,Northwest University,the Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2017JM4013)the Scientific Team Foundation of Department of Geology,Northwest University,Xi’an。
文摘Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area.The South China Sea(SCS)is a typical marginal sea that includes Paleo SCS and New SCS tectonic cycles.The latter includes continental marginal rifting,intercontinental oceanic expansion and oceanic shrinking,which controlled the evolution of basins,and the generation,migration and accumulation of hydrocarbons in the deepwater basins on the continental margin of the northern SCS.In the Paleogene,the basins rifted along the margin of the continent and were filled mainly with sediments in marine-continental transitional environments.In the Neogene–Quaternary,due to thermal subsidence,neritic-abyssal facies sediments from the passive continental margin of the SCS mainly filled the basins.The source rocks include mainly Oligocene coal-bearing deltaic and marine mudstones,which were heated by multiple events with high geothermal temperature and terrestrial heat flow,resulting in the generation of gas and oil.The faults,diapirs and sandstones controlled the migration of hydrocarbons that accumulated principally in a large canyon channel,a continental deepwater fan,and a shelf-margin delta.
文摘The mechanisms causing quality variations and key control factors of submarine-fan reservoirs in the gas field X of the Rovuma Basin,East Africa are analyzed based on core and well-log data in this paper.Depositional fabric,lithofacies difference and characteristics of genetic units are the fundamental reasons of reservoir quality variations.In the case of weak cementation,porosity and permeability of submarine-fan reservoirs are controlled by grain sorting and clay content,respectively.Reservoir quality variations for 5 main lithofacies are related to variable depositional fabrics and calcite cementation.Among them,massive medium-coarse sandstones with weak cementation have the highest porosity and permeability,and coarser or finer sandstones have poorer reservoir quality.The existence of bottom current can develop laminated sandstones,improving the pore structure and physical properties greatly.Lithofacies vary among different types,locations and stages of genetic units,and they control the distribution patterns of submarine-fan reservoir quality:the physical properties of channel shaft or lobe main body are better than those of the channel or lobe edge.The sandstone sorting and physical properties are gradually improved from near-source to far-source.When multi-stage sand bodies are superimposed,the sand-mud ratio in the later stage is higher than that in the earlier stage,making the physical properties get better in the later stage.