Study on Oil and Gas Inclusions and Oil and Gas Accumulation Stages in Majiatan Area, Western Margin of Ordos Basin

The western edge of the Ordos Basin has abundant oil and gas resources. To explore the stages and direction of hydrocarbon fluids migration in petroliferous basins, the hydrocarbon-bearing strata in the Majiatan area on the west margin of the Ordos Basin was analyzed based on petrographic observations, homogenization temperature, salinity and composition of inclusions. The inclusions can be identified as five types. Type I, II and III inclusions exhibit abundant hydrocarbon content, whereas Type IV and V show poor hydrocarbon content. Based on homogenization temperature and salinity analysis, the five types of inclusions can be divided into two-stage formation, Type I, II and III included in the early stage and Type IV and V formed in the late stage. The direction of the hydrocarbon fluid migration of the early and late stages was from the southeast to the northwest, and the difference between the two stages of hydrocarbon fluid migration and inclusions formation depends on the fault activity from the Triassic to the Jurassic. This study is of great significance for future exploration of oil and gas in the Ordos Basin's western margin.