The analysis of permeable units of the reservoir rocks and distribution of the residual oil in the Fanjiachuan Oil Field, northern Shaanxi

The Fanjiachuan Oil Field lies at the juncture of the northern Shaanxi slope and Tianhuan depression. The reservoir rocks in the oil field within the nose or domal structures consist dominantly of the Jurassic Yan'an Formation, representing a succession of the fluvial-swamp terrigenous clastic coal-bearing formations. Now the oil field is in the later stages of development. The present paper deals with the division of the permeable units made by using the reservoir flow layer indicator (FZI) values, and the relationship between the genetic sandstones and the permeable units and the distribution of the residual oil so as to precisely evaluate the interformational residual oil potential and to ascertain the distribution of lower-grade nonhomogeneous reservoir units.