Xinglongtai oil reservoir is characterized

in terms of micro heterogeneity

by obvious distinctions on component and structure of rock between underlayer series and upper one. Rock assemblage in upperlayer series mostly consists of sandstones without gravel which are mainly feldspar rock-fragment ones

whereas rock assemblage in underlayer series is chiefly composed of sandstone with gravel which are mainly feldspar rock fragments. The sorting of sandstone grains is poorer in underlayer series than that in upper one. The particle size in underlayer series is thicker than that in upper one. Macro heterogeneity shows uneven growth of sand body and obvious variations of porosity and permeability.Vertically

the thickness of single sand body and the frequency of sand body as well as the density of sand rock are all smaller in upperlayer series than that in under one.Horizontally

the sand body in the upperlayer series is divided into two parts locating in the east and west which gradually join together upwards. The distribution of sand bodies in the underlayer series is wide. Whereas the distribuition area gradually decreases upwards. Inter-layer

internal and plane heterogeneity of porosity and permeability is obvious

moreover the inter-layer heterogeneity is intense than internal heterogeneity which gradually gather head from bottom to top.Primary reasons leading to reservoir heterogeneity are sedimentary environment and tectonism.