Characteristics and influence factor analysis of the Chang 8 reservoir in Yanchang formation of Maling oilfield,Ordos Basin

This paper studies the Chang 8 reservoir of Yanchang formation in Maling oilfield of Ordos Basin by using relevant data of cores,logging,cast thin section,and scanning electron microscope.The result indicates that the Chang 8 reservoir is dominated by lithic arkose and feldspathic lithic sandstone,has low compositional maturity;the reservoir presents diverse pore types with the dominant intergranular pores and feldspathic dissolved pores as major reservoir spaces;it is a typical low porosity and low permeability reservoir;reservoir properties obviously subject to sedimentary facies and diagenesis.The best reservoir property is found in underwater distributary channels with thick deposition and coarse grain size,then in mouth bars,and the poorest property is in delta front sheet sands;diagenesis obviously controlled reservoir properties;compaction and cementation had deteriorated reservoir properties;and dissolution had improved reservoir properties.