Study On The Sedimentary Facies Of Dainan Formation In Longgang Area Of Jinhu Depression

The JinHu sag is a secondary sag of the SuBei basin,located in the west of the dongtai depression.In the plane of Longgang area,there are two deep depressions in tongcheng fault zone and Yangcun fault zone,which are sandwiched by three structural high belts.At present,it has been found that the source rocks of sanhe and Longgang in sub-concave fusi section have strong oil generation capacity,and have the condition of forming a certain scale reservoir.The mature source rock distribution area of fusi section and the favorable reservoir and cap combination development area of Dainan formation are favorable zones for the formation of Dainan reservoir.Previous studies mainly focused on the whole golden lake depression,and there were few detailed studies on theLonggang area.However,due to the influence of structure,lithology and other factors,the sedimentary microfacies in different areas of Longgang were quite different.Moreover,due to the particularity of the sedimentary system,there were constant disputes.Therefore,the detailed study of sedimentary micro facies in this area is very important,which can provide reasonable guidance for oil and gas exploration and development.In this paper,the mudstone color index plan,ZTR index plan,sand thickness and sand ground ratio plan of Longgang area in Jinhu depression were drawn,and combined with the single-well facies analysis,core photo and regional sedimentary background comprehensive analysis of Jinhu depression,it was concluded that the mineral source of the Dainan formation in the study area came from northwest,southwest and southeast directions.The mudstone in the study area is mainly brownish yellow,light grey and grey.The color index distribution range of the mudstone is mainly within the range of-50 to 50,indicating that the study area is in the coastal and shallow lake environment of weak oxidation to weak reduction.The type of sandstone in the study area is dominated by feldspar quartz sandstone,and the content of stable components is less.The whole body shows the characteristics of "high quartz,low feldspar,high debris".The analysis shows that the yangcun fault zone in the study area is deltaic,and the western slope and tongcheng fault zone are offshore and shallow lake.Based on the analysis of the sand body and microfacies in the sedimentary period,the sand body thickness plan,sedimentary microfacies plan and sedimentary microfacies section map of the Daian formation in Longgang area were drawn,and the sedimentary model of the delta deposition and the coastal and shallow lake system in the study area was finally established,and the distribution characteristics and space-time evolution of the sand body were clarified.