Abstract:

The deep sandstone of delta,fan delta and fluvial fan facies are low porosity low permeability or mid porosity low permeability reservoirs with filling micropores and intragranular pores.In general,the intragranular porosity decreased with the increasing of sandstone burial depth;the secondary enlargement of quartz,the filling of chlorite and kaolinite,the cementation of iron calcite and iron dolomite reduced the porstiy;solution in deep strata resulted in large amount of eroded pores.Late diagenesis could be divided into A,B and C diagenetic substages.Considerable organic acids in A substage caused solution pores in feldspar and debris;in the B substage,CH₄ and CO₂ existed,chlorite filled the pores,thus preserved micropores and solution pores;in the C substage,organic acids decreased and CH₄,CO₂ increased,thus forming fractures and improving reservoir property.

Key words: Jiyang Depression, deep sandstone, sedimentary facies, reservoir, diagenesis, evolution model