Genetic type and structure pattern of the interlayer inside thick sandbody of Baobei block in Yanqi basin

Major reservoir of Baobei block in Baolang oilfield be- longs to Glutenite units in braided river of Sangonghe for- mation of Jurassic.The types and structure pattern of in- terlayer greatly affect the water-flooding development results.Based on the analysis of drilling core and well log,four types of interlayer have been identified:sand- stone interlayer,coaly interlayer,compact interlayer and calcareous interlayer.The study on interlayer structure and its distribution on two levels-between monolayers and inside monolayer provide geological guidance for oil- field development.From the angle of stability,four types are classified:stable,relatively stable,under stable and instable. With the combination of sedimentary micro-facies, the distribution patterns are summarized:interlayer be- tween monolayers commonly occurs at channel bay or the top of abandoned channel,or the end of channel;the in- terlayer inside monolayer sand body,mainly occurs inside braided distributary channel,secondly occurs at channel side and interdistributary bay,occasionally occurs at channel.