SEDIMENTARY TYPES AND CHARACTERISTICS OF LoWER CRETACEOUS RESERVOIR ROCKS IN TANZHUANG SAG, ZHOUKOU DEPRESSION, SOUTHERN NORTH CHINA BASIN

Sedimentary types and properties of the Lower Cretaceous clastic rock reservoirs in the Tanzhuang Sag,Zhoukou Depression,Southern North China Basin are studied in this paper based on data of core,well logging and thin-section.Two ways of sediment provenance exist in the Tanzhuang Sag during the Early Cretaceous.The south of the basin mainly develop fan delta facies from south.The north of the basin mainly develop delta facies from north and northwest.The center of the basin mainly develop lacustrine and turbidite fan.Reservoir rocks consist of glutenite and sandstone with low componential and textural maturities.Fine sandstone is the dominant rock type.Clastic reservoir properties are very poor due to low rock maturity,strong compaction and cementation as well as weak dissolution.Reservoirs with different generation types have different properties.Delta-plain sandstones buried less than 2 200 m deep have the most effective reservoir properties.As depth increases,the properties fall rapidly.At the same depth,reservoir properties reduce from fan delta front and fan delta plain to shore-shallow lacustrine.