Petrography and diagenesis of Permian sandstone reservoirs in Zhoukou Depression, Southern North China Basin

The petrography and diagenesis of the Permian tight sandstone reservoirs in the Zhoukou Depression of the Southern North China Basin were studied using sedimentology, petrology and petroleum geology based on field outcrops, drilling cores observations and laboratory experiments. The main contributive sandstone reservoirs include the Hushi sandstones in the Taiyuan Formation, the Dazhan sandstones in the Shanxi Formation, the Shaguoyao sandstones in the Lower Shihezi Formation, the Tianjiagou sandstones in the Upper Shihezi Formation and the Pingdingshan sandstones in the Sunjiagou Formation. In the sandstones, quartz content is relatively higher. There are larger pores among quartz particles. But many pores disappeared and even the particles were broken because of pressure. Feldspar content is lower and most of which is potash one. The interstitial materials are mainly muddy, siliceous, calcareous and chlorite. Four types of diagenesis can be found, which include compaction-pressolution, cementation, dissolution and metasomatism. Many diagenesis indexes were studied in detail in order to con firm diagenetic stages, which is in the stage B of the middle diagenesis phase or the late diagenesis phase.