The Application Of Seismic Sedimentology In JUNIN4 Block,Venezuela Oil Field

JUNIN4 Block is located in the west of Orinoco Heavy Oil Belt in Venezuela oilfield and its oil reserves are huge.In order to achieve the effective exploration and development of heavy oil in this block,it is necessary to research the strata in detail.The large area,small number of wells,irregular well pattern distribution,unclear understanding of sedimentary facies type and phase distribution greatly restricts the next effective exploration and development of JUNIN4 Block.Therefore,this paper takes the Merecure Formation and the lower member of Oficina Formation in JUNIN4 Block as an example,aiming at the sedimentary characteristics of braided channels,meandering channels and distributary channels in the study strata.This paper synthetically applies sequence stratigraphy principle,seismic sedimentology theory,method technology and well-earthquake combination to establish isochronal stratigraphic framework.Under the constraints of isochronal stratigraphic framework,the distribution of braided channels,meandering channels and distributary channels sediments is studied by the application of technical methods of seismic sedimentology to provide some reference frame for the next step of the exploration and development.These following positive results have been achieved in the JUNIN4 research area.Firstly,the paper synthetically analyses the results of stratigraphic division by predecessors in the study area.On the basis of comprehensive application of core,well logging and seismic data,guided by the principle of sequence stratigraphy,combined with time-frequency analysis,frequency-division technology seismic techniques,the study strata are divided into three sand groups.The Merecure Formation is divided into one sand group,and the lower member of Oficina Formation is divided into two sand groups.The isochronal stratigraphic framework of the study area has been established by identifying and tracing isochronal stratigraphic interfaces in seismic section.Based on the regional geological background,the sedimentary characteristics of the target strata are researched by means of core observation and description,logging data analysis and seismic section characteristics analysis.Based on the comprehensive analysis of lithologic,logging and seismic facies markers,the Merecure Formation and the lower member of Oficina Formation in the study area are identified as typical river-delta sedimentary systems,and are divided into braided channel,channel bar,meandering channel,flood plain,crevasse splay,natural levee,distributary channel and interdistributary bay.Based on core and logging data,single well facies analysis and connected well facies analysis are carried out.Based on the characteristics of modern river-delta sediments,the sedimentary model of target strata in the study area is established.Under the guidance of sedimentary model,using the key technologies of seismic sedimentology,such as 90 degree phase conversion technology,stratum slice,spectrum analysis and seismic attribute analysis to study and analyse the profile and plane distribution characteristics of sedimentary microfacies and the vertical evolution history of the target interval in the study area.Combining with the verification of well data,the distribution characteristics and evolution rules of sedimentary facies in the target interval are revealed.Contrast the development characteristics of sedimentary microfacies of each sublayer in the target strata,favorable oil-bearing facies zones are found out,which provides important geological reference for the next exploration and development of the study area.