The effect of diagenesis on pore structure of sandstones in third oil layer of Xingouzui Formation in Tuoshi area

Qianjiang Depression is discussed in this paper.The compaction and cementation decreased the pore throat and pore radius of the sandstones in different degrees

and caused the pores to disintegrate into micropores and intercrystal pores

the throats into schistose throats and tubebundle throats in sandstones.The dissolution increased the pore throat and pore radius of sandstones

turned the pores into coarse ones and tubular throat.The compaction resulted in better pore sorting

but the cementation and dissolution made it more complicated.In sandstones of compaction type and cemetation type

the permeability contributed peak position is inconsistent with that of the pore distribution peak position

and their permeability for air is usually less than 1 thousandth of square micron and devoted by few pore spaces with radius bigger than 8 micron.In sandstones of dissolution type

the permeability devoted peak position is usually consistent with that of the pore distribution

thus the main pore spaces of the sandstones are vadose pores.