Characteristics of Reservoir Microscopic Pore Structure and Its Controlling Factors of Chang-6 in Jiyuan Area of Ordos Basin

Based on analyses of casting thin sections,scanning-electron micro-scopes,X-ray,constant-rate mercury injection of the reservoir sandstones in Jiyuan area of Ordos Basin,the characteristics and microscopic pore structure of reservoir were studied.The results show that reservoir sandstones mainly consist of feldspathic sandstone and lithic-feldspathic sandstone,the types of reservoir pores are various,the dominating pore type is inter-granular pore and feldspar-dissolved pore.The data of constant-rate mercury injection indicate that the characteristic parameters,such as the average throat radius,the effective throat volume,the average pore radius,the effective pore volume and the pore-to-throat ratio,are correlative with the porosity and permeability of reservoir.For the rock samples with higher permeability,the average throat radius and mainstream throat radius are better while the pore-to-throat ratio is lower.The throat is the basic factor to strain permeability of reservoir.The sedimentary facies and diagenesis were the main factors for controlling reservoir pore evolution.The different sedimentary environment resulted in the different texture maturity and composition maturity of reservoir,and resulted in the difference of reservoir pore further.Compaction and carbonate cements were the main factors for destroying pore of reservoir,while dissolution were constructive for pore of reservoir.