Abstract: Due to the low-permeability and tight sandstone reservoirs, as well as the huge thick insulating layer formed between the source rocks and the shallow reservoirs（Shihezi and Shiqianfeng Formation）of Upper Paleozoic in northern Shaanxi slope, Ordos basin, it is significant to study on the natural gas migration channels and it’s accumulation model. Based on the core and micro-fracture observation, logging interpretation, porosity-permeability analysis, and the analysis of diagenesis together with fractureforming time, we have focused on the matching relationship between fractures distribution in the insulating layers and the natural gas pools in the shallow reservoirs. It is believed that the mainly sheering fractures, developed between Late Jurassic and Early Cretaceous, improved permeability and provided migration channels for natural gas synchronously. According to the studies above-mentioned, it is proposed that the shallow gas reservoirs have a good coupling relationship with fractures in the insulating layers on time and space. Based on the fracture migration and sandstone storage, a natural gas accumulation model was presented to show the reservoirs of Shihezi and Shiqianfeng Formations, which is named as lithologic-fractural gas reservoir.

Key words: northern Shaanxi slope, Upper Paleozoic, fracture, migration channel, natural gas, accumulation