The Study On Sedimentary Evolution And Sand Body Distribution Of MPE3 Block In The Eastern Venezuela Basin On The Condition Of The Discrepancy Of Miocene Transgression

The Eastern Venezuelan basin is a world-class petroliferous area,with the sedimentary environment controlled by the interaction between the Caribbean plate and the American plate.The MPE3 block has huge potential for heavy oil extraction,which is an important development block in the eastern Orinoco heavy oil belt in the basin,Therefore,in order to achieve the 20% recovery requirement,it is necessary to optimize the development method at different stages.In order to meet the demand,such as horizontal well cold recovery,thermal recovery and SAGD,we have to deep understanding of reservoir depositional environment;and in order to have a deep understanding of the sedimentary evolution model of the tidal-controlled tidal delta.This paper is based on the MPE3 block in the Carabobo area of the eastern Orinoco heavy oil belt,combined with the regional geological background data,paleostructural data,and analysis data of the core,logging template,3D seismic data and the description of the sand body scale based on the horizontal wells.we learned the types of sedimentary systems,vertical evolution processes,and types of river channel conversion and sand body distribution.The following points are summarized as follows:(1).With the theories and methods in sequence stratigraphy to identify the sequence interface through the core of a single well and the well logging,combined with the identification of the interface on the 3D seismic profile,we can dividing the destination section into a Three-level sequence and separates five four-level cycles from the lower of the Morichal to the top of the Jobo in the Miocene.Based on the division of the sequence,the four segments of the Oficina group were further subdivided into 10 small layers according to the principle of cyclical comparison,from bottom to top O-13?O-12i-2?O-12i-1?O-12s-2?O-12s-1?O-11i-2?O-11i-1?O-11s?Jobo-inf?Jobo-sb.(2).The sea level of the Morichal section of the study area continues to rise,and the transgression during the O-11 i sand formation is relatively obvious.And,there are significant differences in the effects of transgression in the eastern and western regions of the study area,through analysis the formation dip,clay mineral content,and spores,we can conclude that the rate of transgression in the eastern region of the study area is relatively slow,and sea level changes are gentle,but the scope and duration of transgression are longer.On the other hand,because of the dip of the stratum and the topography of the paleo-uplift in the western region,the northwestern part of the area is affected more by the effects of transgression than the eastern part,and the sea level changes drastically and frequently.(3).Combined with regional geological background,paleostructural,and study of cores,logging patterns,sandstone thickness distribution maps,and plane seismic attributes and horizontal wells for sand body scale characterization,the analysis concludes that the Morichal section of the study area is mainly developed delta plain sub-facies controlled by braided river,including the braided river channel,diara,floodplain,diversion bay,etc.The O-11 s stratum and Jobo stratum mainly develops the tidal delta front sedimentary facies.including the tidal channel,tidal sand bars and sheet sand,sand flat,etc.(4).The O-13 and O-12 in the lower part of the Morical section develop Far-source sandy braided river delta including the braided river channel,diara and other dominant sand bodies.The sand bodies on the flat surface are in the southwest-northeast direction.O-11 i in the upper part of the Morichal section is in the period of transgressive system,sea level rises rapidly,and tide-affecting braided delta sediments are developed.During this period,muddy or silt fine sediments were observed in the whole area,the ratio of sand to land is low.when the Jobo period is a highstand systems tract,the sea level gradually shifts from ascending to relative decline.The southern region of the research is characterized by the development of tidal sandbars and tidal channels,while the northern region is composed of large layers of thin sand which distributed Contiguous.(5).Combined with the tectonic of the foreland basin in the eastern Venezuelan Basin,the depositional effects of the delta depositional model evolution and the influencing factors of the distribution of the sand bodies are attributed to changes in paleogeomorphology,palaeoclimate and source material supply differences.