Significance of Lithology Analyses on the Researches of Conglomerate Reservoir Architecture of Alluvial Fan Sediments:Taking Alluvial Fan Reservoir in Some Area of Northwest Margin of Junggar Basin as an Example

As one of the most important kinds of reservoir,conglomerate reservoir has always been a key area to explorationists and developers of oilfield.It is characterized by quick changes of sedimentary facies and strong heterogeneity of reservoirs.Lithology of conglomerate and sand-conglomerate took the leading role.On the base of lithology analyses,the strata were divided into three sets.The first set is from S47to S327,and its lithology is dominated by sand-conglomerate.Sandstone,cobble conglomerate,pebble stone and fine conglomerate showed as a thin layer.The second set is from S317to S237,and its lithology is mainly of sandstone.Fine conglomerate,pebble stone and sand-conglomerate presented as thin layer.The third set is from S227to S36,and mudstone took the leading role.Sandstone,sand-conglomerate,fine conglomerate and pebble stone appeared as thin layer.Based on these researches,the reservoir architecture were carved up into thirteen types with four degrees such as channel flow conglomerate,laminar flow conglomerate and so on.During this process,well logging data and other information were combined.At the same time,relationship between lithology and reservoir architecture were studied.One or two types of lithology of sand-conglomerate and pebble stone took the leading role in reservoir architecture of channel flow conglomerate and channel beach conglomerate,and high-permeability belt often formed at their position.Although laminar flow conglomerate extended like schistose,the types of lithology of it changed quickly.And on type of lithology took the leading role.Some mudstone of fine grain lithology developed as boundary of reservoir architecture,and they strengthened the heterogeneity of reservoir.The difficulty of reservoir development increased.Sand-conglomerate and sandstone formed main body of braided channel and braided sandstone-conglomerate dam.Lithology characteristics of them were similar with laminar flow conglomerate.The influence of lithology and reservoir architecture to reservoir physical properties and reservoir development were discussed later.