The Study On Sedimentary Microfacies Of Guantao Formation In The North Of Liuxi Oilfield Of Raoyang Sag

Guided by high resolution sequence stratigraphy,sedimentology and subsurface geology of oil and gas fields theory,through drilling,well logging,seismic and indoor test data analysis,it is believed that Guantao Formation in research area is divided into three reservoir group with seven sand group,among which Ng₂ reservoir group is subdivided into 7 single sand layers while Ng₃ reservoir group is subdivided into 13 single sand layers;According to the comprehensive study of key well core observation and description,laboratory analysis and test data and well logging curves characteristics,it is shown that the main sedimentary facies are meandering river facies and braid river facies in Guantao Formation of this area.The braided river can be further subdivided into four microfacies: diara,channel deposits,overbank origin and flood plain while the meandering river can be subfurther divided into six microfacies: point bar,channel deposits,natural levee,flood fan,abandoned channel,flood plain,and this paper summarizes all kinds of subfacies and microfacies identifiers.It systematically studies the plane distribution of sedimentary facies on the basis of the recognition of sedimentary microfacies and pointes that: the Ng₃3 sediment was deposited by typical braid river that the channel was large in scale with thick sand body connected into sheet on a flat surface;then the upper Ng₃2 and Ng₃1 sediment was deposited by braid river-low curved meandering river with relatively small-scale channel deposit.During sedimentary period of Ng₂,the main sedimentary facies was meandering river with widely distributed argillaceous sediment and thin and isolating distributed sand body.The sediment was deposited by braid river-low curved meandering river in Ng1 sedimentary period again with increasing scale of sand body and channel deposit.The distribution of sand body and channel was mainly controlled by tectonic,and the river mainstream line mainly extended in northeast direction in the west block,while in the east block it extended in northwest or nearly east-west direction.Finally,according to sand body and sedimentary microfacies distribution characteristics,combined with the analysis of reservoir forming condition in the research area and well test data,the paper predicted 6 favorable blocks of exploration and development in two valuable oil-bearing stratum of Ng₃2 and Ng₃1 sand group.