Abstract: The reservoir strata of the first member of Yaojia Formation of Changjiaweizi region in the northern part of Songliao basin, are mainly composed of fine feldspathic debris sandstone with A-substage of late diagenesis. And mass appearance of secondary pore improve the capability of gathering, even the primary pores were poorly preserved. The pore types, porosity, permeability and control factors of the reservoir were studied by observing normal and casting thin section, micropolariscope, core testing, mercury intrusion test，scanning electron microscope(SEM), cathode light and so on. The main reservoir pores were composed of corrode expanding intergranular pore and corrode inner pore; pore structures mainly belong to ⅡA,ⅡB; porosity rangs from 10% to 15% and permeability rangs from 0.01×10^-3μm² to 1×10^-3μm²; the reservoir is an axial canal and a low permeability layer; the reservoir quality is mainly influenced by micro sedimentary facies, grain size and dissolution; the permeability is influenced mainly by the type and filling form of hydrosyalite.

Key words: reservoirs, reservoir in the first member of Yaojia Formation, influence factor, Changjiaweizi region, Songliao basin