Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed ...Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation.The results show that due to the great sea level rise,the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta,and eventually to tide-dominated delta.Vertically,during the early stage of sedimentation of Oficina Formation,the distributary channels of the delta were dominated by braided river channels.While in the later stage,as the tidal effect was gradually intensified,the channel changed from braided channel to meandering channel.On plane,as a result of differential transgression,sedimentary framework and distribution of sand bodies vary across the study area.Compared with the eastern part,the western part has more braided channels,larger channel bars,less developments of distributary bay and higher ratio of sand to mud.Whereas the braided channels in the south are larger than those in the north.It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area.Factors like the structural and paleogeomorphological change,sea level variation,supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies.It is predicted that the major sandbody is more developed in the central south,which can guide the subsequent horizontal well development.展开更多
The channel of Bhagirathi River is the branches off from the Ganga at Nurpur (lower course of the Ganga). Bhagirathi River is one of the main rivers in Murshidabad district. Analyzing the image of the Bhagirathi River...The channel of Bhagirathi River is the branches off from the Ganga at Nurpur (lower course of the Ganga). Bhagirathi River is one of the main rivers in Murshidabad district. Analyzing the image of the Bhagirathi River in Murshidabad district through the year 1970, 1977, 1990, 2000 and 2006, it is found that significant changed has been occurred in souththern part of the river and less change is found in the middle part which is close to the Berhampore town. Toposheet of the year 1970 is also compared with the image data to observe the change. Water discharge, soil types and transportation of sediment is the major contributing factor of morphological changes like bar or shoal, ox-bow Lake, meander etc. Maximum erosion takes place at Dear Balagachi and after Baidyanathpur. A cut-off has take place at Baidyanathpur in 1984 [1]. It is found from the study that there is a possibility of natural meander cut-off at Dear Balagachi and near Majayampur. The traditional bank protection works, concrete walls, cemented stone and brick, play a significant role in the modification of the hydraulic aspect of the discharge values and in the interference in the water dynamics of erosive and depositional phenomena both upstream and downstream.展开更多
基金supported by the Important National Science Technology Specific Projects (number 2016ZX05031-001)
文摘Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation.The results show that due to the great sea level rise,the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta,and eventually to tide-dominated delta.Vertically,during the early stage of sedimentation of Oficina Formation,the distributary channels of the delta were dominated by braided river channels.While in the later stage,as the tidal effect was gradually intensified,the channel changed from braided channel to meandering channel.On plane,as a result of differential transgression,sedimentary framework and distribution of sand bodies vary across the study area.Compared with the eastern part,the western part has more braided channels,larger channel bars,less developments of distributary bay and higher ratio of sand to mud.Whereas the braided channels in the south are larger than those in the north.It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area.Factors like the structural and paleogeomorphological change,sea level variation,supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies.It is predicted that the major sandbody is more developed in the central south,which can guide the subsequent horizontal well development.
文摘The channel of Bhagirathi River is the branches off from the Ganga at Nurpur (lower course of the Ganga). Bhagirathi River is one of the main rivers in Murshidabad district. Analyzing the image of the Bhagirathi River in Murshidabad district through the year 1970, 1977, 1990, 2000 and 2006, it is found that significant changed has been occurred in souththern part of the river and less change is found in the middle part which is close to the Berhampore town. Toposheet of the year 1970 is also compared with the image data to observe the change. Water discharge, soil types and transportation of sediment is the major contributing factor of morphological changes like bar or shoal, ox-bow Lake, meander etc. Maximum erosion takes place at Dear Balagachi and after Baidyanathpur. A cut-off has take place at Baidyanathpur in 1984 [1]. It is found from the study that there is a possibility of natural meander cut-off at Dear Balagachi and near Majayampur. The traditional bank protection works, concrete walls, cemented stone and brick, play a significant role in the modification of the hydraulic aspect of the discharge values and in the interference in the water dynamics of erosive and depositional phenomena both upstream and downstream.
