Comprehensive evaluation of coal-bearing tight sandstone reservoir logging in the Benxi Formation, east-central Ordos Basin

The tight sandstone reservoirs of the Benxi Formation are characterized by low pore and low permeability inhomogeneity, etc. It is important to conduct a comprehensive evaluation study on the characteristics and logging of the tight sandstone reservoirs of the Benxi Formation for exploration and development. The study focuses on the application of imaging logging data such as nuclear magnetic resonance (NMR) and array acoustic wave, combined with conventional logging, to carry out the characterization and comprehensive logging evaluation of coal-bearing tight sandstone reservoirs. The study shows that the rock types of tight sandstone of Benxi Formation include quartz sandstone and rock chip quartz sandstone; the porosity is mainly distributed in (1.5%~4.5%) and the permeability is mainly distributed in (0.01mD~0.3mD). The porosity was solved by NMR logging; the permeability was solved by SDR calculation model; the water content saturation was solved by Indonesian equation considering the influence of mud; and the mud content of logging curve was solved by CGR, all of which achieved good agreement with the results of assay analysis. Various methods were used to discriminate the gas content of the reservoir. The rock brittleness indices calculated using sonic imaging and lithology scanning logs are consistent with each other.