摘要：The evolution of the quality of a reservoir in M iddle Permian P2hs sandstone was studied via pet- rographical analyses from wells in the Sulige gas field of the Ordos Basin. The P2hs sandstones are predom inately sublitharenites to litharenites. The average core porosity and perm eability range w idely from 0.56% to 18.5% and 0.004 to 7.43 mD, respectively, representing typical low -porosity and low - perm eability reservoirs. The diagenesis that affects reservoir quality includes compaction, cementation, dissolution of skeleton particles and cements, and obvious m ultistage diagenesis. Compaction processes, rather than cementation, accounts for the majo rity of destruction of the original sandstone porosity. However, cementation s till accounts for 45% of porosity loss, on average. Clay minerals occlude pores and decrease reservoir quality. However, when intercrystalline pores formed by cementation of clay minerals— m ainly kaolinite intercrystalline pores— develop, reservoir quality is improved. A dditionally, the dissolution of grains of lith ic fragments and carbonate cement are also the main driver of porosity enhancement in P2h8 sandstones. This study provides insights into how diagenesis can influence reservoir qualities of tight gas sandstones.
关键词：Reservoir quality;diagenesis;tight sandstone;Sulige gas field;Ordos Basin
