Mahu sag is an important example of the application of the whole oil and gas system theory in the Junggar basin. The oil- gas reservoir pattern, which exhibits both normal and irregular distributions, corresponds to reservoir types with orderly distributions. To clarify the reservoir characteristics and controlling factors, data from drilling, logging, and laboratory studies of over 50 Permian reservoirs in the Mahu sag were analyzed. The Permian sedimentary rock reservoirs in the Mahu sag are characterized by orderly variations in lithology, facies, and reservoir properties from the edge of the sag to the depositional center. The lithology transitions from coarse clastic rocks to medium clastic rocks and finally to fine- grained sedimentary rocks, with grain size decreasing in an orderly, continuous, and sequential manner, corresponding to changes in sedimentary facies. Coarse clastic rocks can be classified into shale- rich conglomerate facies, shale- bearing conglomerate facies, and shale- lean conglomerate facies based on shale content. Fine- grained sedimentary rocks can be divided into argillaceous lithofacies and dolomitic lithofacies according to the content of felsic and livid components. The lean and argillaceous conglomerate facies, along with argillaceous rock facies, exhibit favorable reservoir properties, with large- scale conventional conglomerate and unconventional shale oil reservoirs discovered in these facies, respectively. Sedimentary facies control the orderly distribution of lithology, while gravity flows, torrents, traction flows, and the dynamics of heavy and light fluids are closely related to the orderly distribution of lithofacies. The content of argillaceous complex and the composition of felsic minerals have a decisive influence on the reservoir properties of coarse clastic rocks and fine- grained sedimentary rocks, respectively. Additionally, compaction diagenesis significantly impacts the reservoir properties of medium clastic rocks. The orderly distribution of sedimentary rocks and the regularity of their reservoir properties control the gradual transition of oil and gas from continuous unconventional reservoirs to discontinuous conventional reservoirs.