Diagenesis characteristics and their influence on Porosity and Permeability of sandstone from Yingcheng Formation in Jinshan field

In order to understand the diagenesis and its influence on porosity and permeability of sandstones from Yingcheng Formation in Jinshan field，applying thin sections，casting and scanning electron microscope， the authors studied petrography，diagenesis，porosity and permeability of Yingcheng Formation sandstone reser- voir． The results show that the reservoir of Yingcheng Formation is mainly composed of lithic arkoses． Sand- stones experienced compaction，pressolution，cementation，metasomatism and dissolution． The primary pores of the sandstones are undeveloped; most of pores are the secondary pores，which are mainly intragranular dissolu- tion pores in feldspar and debris． The compaction and cementation reduced the primary pores in sandstones， the porosity and permeability decreased; while the dissolution formed the secondary pores，resulting in the porosity and permeability increase． Due to compaction and cementation，the porosity and permeability are reduced with increasing of depth． There exists an abnormal enlargement of porosity and permeability within a depth range 2 310- - 2 450 m． In combination with analysis of petrology，the dissolution of feldspar and debris is most deve- loped in the depth range． Therefore，compaction，cementation and dissolution are the important factors which affect the porosity and permeability of sandstones．