Research On Reservoir Characteristics And Accumulation Conditions Of Chang 8 Oil-bearing Group In Huangling Area, Ordos Basin

Ordos Basin is the main petroliferous basin in China,and Triassic Yanchang Formation of Ordos Basin is the most important oil-bearing series.With the discovery of oil and gas reservoirs in the southeastern margin of Ordos Basin,exploration on the periphery of the basin was made a great attention.Researches about the structure characteristics and sedimentary systems in Huangling area of Ordos Basin were made considerable progress,but the sandstone distribution regulation and reservoir properties were unclear,also fracture occurrence and its influence on the control of hydrocarbon migration and accumulation were not verified,studies on reservoir-forming pattern and its factors were not promoted.Investigating these researches will have important reference significance for the further exploration as well as the development of the hydrocarbon accumulation theory.Based on the reservoir porosity and permeability standard evaluation and the statistics of sandstone type,particle sorting and rounding,interstitial material characteristics,it is fund the reservoir of Chang 8 is tight,but the physical properties exist huge difference in different well blocks of the studied area.Caused by carbonate cementation,single layered thick sandstone has a better physical property than multilayered thin sandstones,so the physical properties of south area are relatively good.Through the statistics of fracture development and distribution rules,it was certain that fracture not only improved the reservoir physical properties,but also provided pathway systems for hydrocarbon migration.Fracture forming period was studied and homogenization temperatures of hydrocarbon bearing fluid inclusions were handled in the previous work,the hydrocarbon infilling stages were approximately confirmed.Equivalent-depth method were adopted to calculate depth differences in equivalent pore structure,residual pressure of Chang 7 mudstone was gotten by calculating pore pressure and ordinary pressure in the underground.Among these researches,it is cleared that residual pressure is the main driving force for primary migration in the studied area.According to the above researches,hydrocarbon accumulation controlling factor are analyzed.It is cleared that relatively good physical property,fracture development and closing to the source rocks are important conditions for the hydrocarbon accumulation in the studied area.