Study On Sand Body Enrichment Rule And Trap Distribution Prediction Of Fu-yang Oil Layer In Xinmin Oilfield, Songliao Basin

Xinmin oilfield is a high-yield block in the south of Songliao Basin,with Fuyu oil layer in the fourth member of Quantou Formation and Yangdachengzi oil layer in the third member of Quantou Formation as the main development series.For a long time,the sedimentary environment of the third and fourth members of Quantou Formation in Xinmin oilfield area has been considered as the meandering river-shallow water delta sedimentary system developed in the arid to semi-arid climate environment,in which the fourth member of Quantou Formation is considered as the shallow water delta sedimentary environment,while the third member of Quantou Formation is considered as the meandering river sedimentary environment,and the two sets of strata are often discussed separately without overall understanding.Fuyu oil layer in Xinmin oilfield has experienced nearly 30 years of exploration and development,and the conventional reservoir resources of thick delta branch channel have been gradually found out,so it is urgent to clarify the distribution and enrichment of thin sand body in the interval.However,Yangdachengzi oil layer in the third member of Quantou Formation,as the exploration horizon of Fuyu oil layer for a long time,has a low degree of exploration and development,and a weak understanding of sedimentary environment,sand body type and trap distribution rule.Therefore,it is of great scientific significance to discuss the sedimentary environment,the enrichment rules of various sand bodies and the prediction of favorable traps with the third and fourth members of Quantou Formation as a whole.Based on the theory of high-resolution sequence stratigraphy and the comprehensive use of logging,core and geophysical data,this paper expounds the evolution rule of meandering river shallow water delta system in the background of frequent base level changes in the third and fourth members of Quantou Formstion in Xinmin oilfield,summarizes the vertical superposition and spatial contact relationship between different types of sand bodies,and analyzes the distribution of favorable traps in combination with the structure background The favorable target area is predicted with the third member of Quantou Formation as the key point.The results show that:(1)there is a complete long-term base level cycle,a long-term rising half cycle and a long-term falling half cycle in the third and fourth members of Quantou Formation,which are divided into 10 middle-term cycles and 30 short-term cycles.(2)The upper part of the third member and the fourth member of Quantou Formation belong to shallow water delta sedimentary environment,and the middle part of the third member is meandering river sedimentary environment.(3)Meandering river channel sand,branch channel sand and sheet sand are the three main types of sand bodies.All kinds of channel sand bodies are controlled by the distribution of river channels and along the direction of material sources,while sheet sand bodies are controlled by the depth of water body,which are filled between underwater distributary channels.(4)Multiple types of composite sand bodies are formed vertically between different sand bodies,with multiple contact relationships in space,and the vertical distribution of sand bodies is from limited to continuous,from thick sand body to thin sand body.On the plane,the distribution of sand body shows the characteristics of thick layer zonal distribution to thin layer continuous distribution.(5)Fault lithologic trap is the main trap type in the study area.Sand body and faults control the spatial distribution of effective traps.The lithologic structural trap in the footwall of reverse fault and horst area is the most effective trap in the whole area.It is considered that the reverse fault step graben Horst area in the northwest of Xinmin and the high Horst area in the south are Fuyang oil layer,especially the effective trap development area of Yangdachengzi oil layer.