The Junggar Basin is one of the major petroliferous basins with abundant oil and gas resources in onshore China. Around 2010 and thereafter, the hydrocarbon exploration for finding giant fields in the basin faced tough difficulties: in the northwestern margin area, no significant breakthrough has been made for long since seeking to “escape from the step-fault zone and extend to the slope area”; in the central part, the exploration for large lithologic-stratigraphic reservoirs stood still; since the discovery of the Kelameili gas field, no important achievement has been made in gas exploration. Under the guidance of “whole sag-oil-bearing” theory in the petroliferous basin, and based on the long-term study and thinking of the petroleum accumulation conditions and characteristics, the authors proposed several new concepts, i.e., a “thrust-induced second-order fault step” hiding under the northwestern slope area; six “hydrocarbon migrationward surfaces” favorable for hydrocarbon accumulation; promising natural gas resource. These concepts have played an important role in the discoveries of Wells Mahu1 and Yanbei1 as well as the confirmation and expansion of Permian-Triassic billion-ton-scale petroliferous areas in Mahu. The fairway of new discoveries has also appeared for natural gas exploration in Wells Fu26, Gaotan1 and Qianshao2, suggesting that the surrounding regions of the highly matured source kitchen are of high possibility to form gas accumulations. Key words: second-order fault step, hydrocarbon migrationward surface, favorable facies belt, lithologic-stratigraphic reservoir, whole sag-oil-bearing, natural gas, potential and direction, Junggar Basin
