MICRO-PORE STRUCTURE CHARACTERISTICS OF THE CHANG 6 MEMBER SANDSTONE RESERVOIR IN HUANGJIANG OILFIELD ORDOS BASIN CHINA

摘要

The Ordos Basin is the second largest sedimentary basin in China.The oil and gas resources in the basin are very rich,and there is great potential for oil and gas exploration and development.The Chang 6 member of the Triassic Yanchang Formation is the main oil-bearing formation of Huanjiang Oilfield.The Chang 6 reservoir of Huanjiang Oilfield currently has the problem of insufficient understanding of reservoir geological laws,especially in the southern part of the oilfield.In this paper,the microscopic pore structure of the Chang 6 member of Huanjiang Oilfield was systematically studied by means of mineral composition analysis,thin section analysis,scanning electron microscopy analysis and mercury intrusion experiments.Experimental results show that the Chang 6 reservoir in Huanjiang Oilfield is a low-porosity,ultra-low permeability reservoir,but there are still some relatively high porosity and high permeability reservoirs in some local areas.The Chang 6 reservoir has an average porosity of 7.43 and an average permeability of 0.15x10-3 qm2.The pore types of the target layer are mainly intergranular pores and feldspar dissolution pores,and a small amount of lithic dissolution pores,intergranular dissolution pores,intercrystalline pores and microcracks are also developed.The mercury intrusion experiment showed that the pores of the Chang 6 member were poorly sorted and the pore structure was complicated.Diagenesis is the main factor affecting the pore structures of the reservoir.