The diagenesis and its influence on Chang-9 reservoirs in Xunyi area of Ordos Basin is studied by means of thin section, casting film, mercury injection. Pore evolution of Chang-9 reservoirs is analyzed, then diagenetic facies of the reservoirs are identified. The major rock types of the reservoir are mainly feldspar sandstone and lithic arkose sandstone. Compaction and cementation result in loss of the reservoir property. The porosity of the reservoirs decreased by 15.5% as a result of compaction, then the porosity of the reservoirs decreased by 13.6% due to cementation. After wads, the improvement of the reservoir pore as a result of dissolution is not obvious, only contributing the increase of porosity by about 1.98%. Base on analysis results, four types of diagenetic facies are identified, namely chlorite film-intergranular pore facies, feldspar solution pore-pore facies, carbonate cementation facies and soft lithic fragments compaction facies. The chlorite film-intergranular pore facies and feldspar solution pores-intergranular pore facies are the favorable diagenetic facies, which is mainly distributed in the central region of underwater channel sand bodies of delta front.
Liu Jiangbin Ren Zhanli Li Wenhou Hu Guilin . Diagenesis and diagenetic facies in the Chang-9 reservoirs of the Triassic Yanchang Formation in Xunyi area，Ordos Basin[J]. Chinese Journal of Geology, 2017, 52(2): 440-452.