Abstract: The Upper Paleozoic reservoirs in the Linxing block, Ordos Basin, were tight sandstones. Fractures characteristics and its
effects on gas accumulation were unclear. This limited the prediction of sweet spots in the region. Based on the data and analyses of
outcrop, core, thin section and well logging, the development characteristics of the fractures in the study area was analyzed, and their
effects on tight gas accumulation were discussed. Results show that the Upper Paleozoic reservoirs of the Linxing block mainly
developed high-angle fractures, followed by mid-low-angle and horizontal fractures. According to the relationship between fractures and
mineral grains, the intragranular fractures, the grain-edged fractures and grain-crossed fractures could be identified microscopically, of
which the grain-edged fractures were the most developed. Influenced by the plastic mudstones, vertical extension of the fracture was
poor, and thus the fractures usually disappeared in the mudstones after stretching one to two meters. Due to the northwest-southeast
ground stress in the Yanshanian period, the fracture strike was mostly northeast-southwest in trending, and the fracture density was two
to five every meter. The fractures could improve the reservoir’s porosity and gas filling efficiency. In the fracture areas, permeability
can be increased by one to two orders of magnitude and gas saturation is higher. In addition, the fractures were the effective pathway of
gas migration and affected the enrichment of tight sandstone gas. In the future exploration and development, the fracture-developed
area should be fully explored and further fracturing should be carried out to obtain higher production.period.

Key words: fracture, hydrocarbon enrichment, tight sandstone gas, Upper Paleozoic, Linxing block