The reservoir space types of various sizes and their connection patterns of the Paleogene shale in Jiyang Depression were characterized through core observation

polarizing microscope and argon ion milling-scanning electron microscopy (SEM) analyses

and high pressure mercury injection

as well as small angle X ray scattering experiment; in addition

the lower limits of effective pore diameter and porosity were clarified according to data such as porosity and oil saturation.A spatial development and distribution model of shale reservoir in Dongying sag was established to predict the favorable reservoir facies belt through integrating thermal maturity (R

o

) with the characteristics of lithofacies

formation pressure

and reservoir space (porosity and pore diameter).The results show that:(1) the pores of the shale reservoir in the study area are mainly intergranular pores

shrinkage pores in organic matter and clay minerals

and intercrystalline pores in carbonate

all of which are connected through a three-level pore-fracture network; (2) the intraparticle pores in clay minerals and intercrystalline pores in carbonate are the most effective pores with the highest contribution to the total porosity

averaging at 50% to 70%

followed by clay shrinkage cracks and tension fissure; (3) the lower limit of pore diameter for shale oil occurrence

the minimum pore diameter for free oil occurrence

and the threshold pore diameter of free oil enrichment are 5nm

10nm and 30mm

respectively; (4) the laminated shale rich in organic matter and carbonate minerals is the highest in total porosity

pore connectivity

and contribution of pores favorable for free oil storage to porosity

so it is a preferential lithofacies; (5) the development and distribution characteristics of shale reservoir space are controlled by the lithofacies type

diagenetic stage

formation pressure and fracture development degree

all of which also serve as important factors for the evaluation of shale oil sweet spots; the prediction of favorable reservoir facies belt is to identify laminated organic-rich shale with relatively higher thermal maturity

highly-developed fracture and high formation pressure under the guidance of graded evaluation scheme.