Diagenesis of the Palaeogene clastic rocks in the Raoyang depression

The present paper deals,in the light of thin-section and SEM examinations,with lithology,diagenesis and diagenetic facies of the Palaeogene clastic rocks in the Raoyang depression.The sandstone reservoirs have low compositional and textural maturity and moderate roundness and sorting,and consist dominantly of feldspar sandstone and lithic feldspar sandstone.The diagenesis comprises compaction,cementation,metasomatic alteration and dissolution.The diagenetic facies associations from the sandstone reservoirs in the middle and deeper parts may be grouped into four types: cementation-dissolution,cementation,compaction-cementation and cementation-dissolution-metasomatism.