By integrating core observations,logging data and seismic interpretation,this study takes the massive Cretaceous carbonates in the M block of the Santos Basin,Brazil,as an example to establish the sequence filling pat...By integrating core observations,logging data and seismic interpretation,this study takes the massive Cretaceous carbonates in the M block of the Santos Basin,Brazil,as an example to establish the sequence filling pattern of fault-bounded isolated platforms in rift lake basins,reveal the control mechanisms of shoal-body development and reservoir formation,and reconstruct the evolutionary history of lithofacies paleogeography.The following results are obtained.(1)Three tertiary sequences(SQ1-SQ3)are identified in the Lower Cretaceous Itapema-Barra Velha of the M block.During the depositional period of SQ1,the rift basement faults controlled the stratigraphic distribution pattern of thick on both sides and thin in the middle.The strata overlapped to uplift in the early stage.During the depositional period of SQ2-SQ3,the synsedimentary faults controlled the paleogeomorphic reworking process with subsidence in the northwest and uplifting in the northeast,accompanied with the relative fall of lake level.(2)The Lower Cretaceous in the M block was deposited in a littoral-shallow lake,with the lithofacies paleogeographic pattern transiting from the inner clastic shoals and outer shelly shoals in SQ1 to the alternation of mounds and shoals in SQ2-SQ3.(3)Under the joint control of relative lake-level fluctuation,synsedimentary faults and volcanic activity,the shelly shoals in SQ1 tend to accumulated vertically in the raised area,and the mound-shoal complex in SQ2-SQ3 tends to migrate laterally towards the slope-break belt due to the reduction of accommodation space.(4)The evolution pattern of high-energy mounds and shoals,which were vertically accumulated in the early stage and laterally migrated in the later stage,controlled the transformation of high-quality reservoirs from“centralized”to“ring shaped”distribution.The research findings clarify the sedimentary patterns of mounds and shoals and the distribution of favorable reservoirs in the fault-controlled lacustrine isolated platform,providing support for the deepwater hydrocarbon exploration in the subsalt carbonate rocks in the Santos Basin.展开更多
Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation seq...Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.展开更多
基金Supported by the China National Science and Technology Major Project(2025ZD1403000)CNPC Major Science and Technology Project(2023ZZ19).
文摘By integrating core observations,logging data and seismic interpretation,this study takes the massive Cretaceous carbonates in the M block of the Santos Basin,Brazil,as an example to establish the sequence filling pattern of fault-bounded isolated platforms in rift lake basins,reveal the control mechanisms of shoal-body development and reservoir formation,and reconstruct the evolutionary history of lithofacies paleogeography.The following results are obtained.(1)Three tertiary sequences(SQ1-SQ3)are identified in the Lower Cretaceous Itapema-Barra Velha of the M block.During the depositional period of SQ1,the rift basement faults controlled the stratigraphic distribution pattern of thick on both sides and thin in the middle.The strata overlapped to uplift in the early stage.During the depositional period of SQ2-SQ3,the synsedimentary faults controlled the paleogeomorphic reworking process with subsidence in the northwest and uplifting in the northeast,accompanied with the relative fall of lake level.(2)The Lower Cretaceous in the M block was deposited in a littoral-shallow lake,with the lithofacies paleogeographic pattern transiting from the inner clastic shoals and outer shelly shoals in SQ1 to the alternation of mounds and shoals in SQ2-SQ3.(3)Under the joint control of relative lake-level fluctuation,synsedimentary faults and volcanic activity,the shelly shoals in SQ1 tend to accumulated vertically in the raised area,and the mound-shoal complex in SQ2-SQ3 tends to migrate laterally towards the slope-break belt due to the reduction of accommodation space.(4)The evolution pattern of high-energy mounds and shoals,which were vertically accumulated in the early stage and laterally migrated in the later stage,controlled the transformation of high-quality reservoirs from“centralized”to“ring shaped”distribution.The research findings clarify the sedimentary patterns of mounds and shoals and the distribution of favorable reservoirs in the fault-controlled lacustrine isolated platform,providing support for the deepwater hydrocarbon exploration in the subsalt carbonate rocks in the Santos Basin.
基金Supported by the National Science and Technology Major Project of China(2016ZX05033-002-008).
文摘Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.
