Characteristics and controlling factors of low-permeability reservoirs in Silurian Kepingtage Formation, 10th tectonic belt in the Tazhong area, Tarim Basin

The basic characteristics of low-permeability reservoirs in the upper unit of Silurian Kepingtage Formation, 10th tectonic belt in the Tazhong area were investigated and the controlling factors associated with sedimentology, diagenesis and tectonism were determined based on core observation, thin section, scanning electron microscopy (SEM), cold-cathode luminescence microscopy (CL) coupled with petro-physical property testing. The results indicate that the low-permeability sandstone reservoirs are mainly composed of litharenite and sublitharenite and the studied reservoirs belong to low-porosity and low-permeability reservoirs. The reservoir space mainly includes residual primary pores, intergranular dissolution pores and tectonic microfractures. The reservoir development was controlled by sedimentology, diagenesis and tectonism. The reservoirs in tidal channel and sand-flat microfacies deposited in strong hydrodynamic environments have substantial primary pores and obviously later acidic dissolution. The resulting reservoirs have good petro-physical properties and are targets for high-quality reservoirs. The controlling factors associated with diagenesis are evidenced by porosity reduction due to compaction and cementation, whereas the reservoir petro-physical properties can be enhanced by dissolution. Microfactures induced by tectonism can improve permeability capability and play some positive role in enhancing reservoir petro-physical properties.