Controls on enrichment and accumulation of Ordovician subsalt natural gas in the central and eastern Ordos basin

In recent years, a number of high-yield industrial gas flow wells and a number of low-yield and low-efficiency wells have been discovered in the subsalt reservoirs in the central and eastern parts of the Ordos basin, which fully demonstrates the complexity of subsalt natural gas distribution and increases the difficulties for exploration and deployment in the future.On the basis of previous research results, this paper aims to systematically study the law of enrichment of natural gas in the main subsalt reservoirs Ma5₇ subsection and Ma5₉ subsection by means of field outcrop geological survey, observation and description of drilling cores, microscopic identification and laboratory related experimental tests, and introducing numerical simulation of tectonic stress field and fluid potential field and structural curvature calculation technology.The sedimentary facies belt affects the reservoir’s property, and the natural crack affects the gas reservoir distribution.The natural gas on the plane is mainly distributed in the relatively thick granitic beach sedimentary microfacies of the central and western dolomite in the work area, mainly due to the development of the fracture system effectively improves the reservoir performance of the sedimentary microfacies reservoir.Under the action of tectonic stress field, natural gas migrates and enriches from high pressure and low porosity zone to low pressure and high porosity zone.The micro-structure has obvious controlling effect on gas reservoir enrichment.The high-production gas wells in this area are located on the nose and its sides position, which provides a geological basis for the exploration and deployment decision of the subsalt gas reservoirs in the future.