Comprehensive analyses are conducted to characterize the Gaotaizi tight reservoir in Qijia area from macroscopic and microscopic perspectives

through Nano Micron CT

automatic mineral identification system (QEMSCAN)

MAPS image mosaic technology

and environmental scanning electron microscopy (ESEM).From the macroscopic perspective

lithologies are mainly siltstone and argillaceous siltstone.The sedimentary bedding structures are diversified-massive bedding are the majority but cross-bedding

wedge bedding and lenticular bedding are also present.The obvious sand-shale interlayer and complicated sedimentary beddings commonly contribute to the heterogeneity of the tight reservoirs

even though the massive bedding is the most favorable for the enrichment of tight oil.The microscopic perspective reveals more interesting characteristics.Pores are continuously distributed in the micro to nano meter level

with the peak of micro pore sizes concentrated in the range of 2-3 μm

and that of nano pores around 200-300 nm.Microscopic heterogeneity can be obviously displayed in the pore-throat spatial distribution and connectivity features of different 3D modeling areas.The main pore spaces are intergranular dissolved pore

intragranular dissolved pore and micro cracks.Moreover

high porosity generally corresponds to high concentration of organic acids

indicating the controlling of porosity by dissolution.