Diagenesis and genesis of effective sandstone reservoirs in the Sulige Gas Field

The He 8-Shan 1 reservoirs in the Sulige Gas Field compose basically of low permeability fluvial sandstone with the coal-bearing stratum diagenetic patterns. The strong compaction is the main reason for the low permeability and the effective reservoirs are those units with relatively high permeability. The depositional hydro-dynamics controls the structure and components of the sandstone, and then, the following diagenetic processes and porosity evolution. The coarse sandstone prove relatively high reservoir quality, with high content of hard quartzite clasts and quartz grains, which favored the preservation of primary pores and occurrence of secondary pores. The medium and fine grain sandstone are poor or none reservoirs, with high content of soft lithic fragments, which led to tight compaction, poor preservation of primary pores and poor development of secondary pores. Six lapidofacies are classified in the Gas Field. The distribution of effective sandstone can be predicted through the integrated studies of lapidofacies and sedimentary microfacies.