Glauconitic sandstone with high GR value of the Cretaceous Napo Formation, developed in the slope of the Oriente Basin, is a new discovered subtle oil-bearing target. This paper is focused on glauconitic sandstone reservoir to reveal its components, porosity structure, diagenesis, petrophysics. Integrated with source rock evaluation and oil distribution, hydrocarbon accumulation and enrichment of glauconitic sandstone are analyzed. Glauconitic sandstone is composed of quartz and glauconitic minerals, characterized by grain-supported framework. Glauconitic sandstone reservoir is low-mid porosity and permeability, characterized by residual intergranular pores. NMR data shows bimodal pore structure and high bound water content. Glauconitic sandstone is the product of phase A of middle diagenetic stage, based on evidences of quartz overgrowth cementation Ⅱ, feldspar dissolution, iron carbonate cements, low-value of smectite in I/S ratio, and high Tmax. Large-area type Ⅱ1 matured shale closes to glauconitic sandstone is probably the oil kitchen in the gentle slope of Oriente Basin. Widespread glauconitic sandstone reservoir and adjacent shale form an excellent source-reservoir-cap assemblage. Glauconitic sandstone play is characterized by closing to source rock, late migration and single accumulation type. It provide a paradigm for petroleum exploration of glauconitic reservoir in similar basin.