PORE STRUCTURE CHARACTERISTICS OF THE TRIASSIC TIGHT SANDSTONE RESERVOIRS IN ANSAI AREA ORDOS BASIN CHINA

Using constant-speed mercury intrusion technology, combined with conventional cast image, constant-pressure mercury intrusion, scanning electron microscopy and slice observation, the paper thoroughly analyzed and investigated the microscopic pore structure of tight sandstone reservoirs in the Ordos Basin Ansai Area. The result shows that the reservoir type of Chang9 tight sandstone in target area is large scale pore with thin throat, reservoir of different permeability levels has similar pore radius distribution, while throat radius varies; Reservoir permeable capability has little pertinence with the pore size, it is mainly controlled by the size of the throat and its distribution patterns. Compared with super-low permeability reservoirs, the throat distribution of ultra-low permeable reservoirs is more concentrated, it has tighter throat, the range of pore-throat ratio is wider and the heterogeneity is stronger. The allocation relation between pore and throat affects the development effectiveness of tight sandstone reservoirs.