Diagenetic Facies and Their Controls on the Quality of Tight Sandstone Reservoirs: A Case Study from the Upper Paleozoic Gas Reservoir in the Eastern Ordos Basin, North China

Figure 11

Photomicrographs of a representative sample from each diagenetic facies. (a) Diagenetic facies of siliceous cemented intergranular pores showing quartz sandstone, secondary growth of quartz, and development of siliceous cement and original residual pores. (b) Diagenetic facies of calcareous dissolution pores showing lithic sandstone and calcareous cement filled with intergranular pores is dissolved. (c) Diagenetic facies of mixed matrix dissolution pores showing detrital quartz sandstone, with the mixed matrix being all dissolved. (d) Cutting dissolution hole diagenetic facies showing detrital sandstone and flexible metamorphic rock cutting dissolution. (e) Strong compacted diagenetic facies of heterobasic alteration showing heterobasic alteration and strong deformation, with compacted dense structure. (f) Undissolved calcareous cementation metasomatism and dense diagenetic facies showing debris quartz sandstone with compacted structure and calcite cementation without dissolution.