Abstract: The Permian of Shawan sag is spoon-shaped, shallow in the north and deep in the south, narrow in the north and wide in the south. From north to south, it can be divided into the northern onlap-truncation belt, the central nose-shaped uplift belt and the southern deep sag belt. The deep sag belt not only has well-developed strata, but also is rapidly thickened, which is the depocenter and hydrocarbon-generation center of the sag. According to the thermal evolution simulation results, large-scale gas generation occurred in the southern deep sag belt. Two second-order unconformities are developed in the Permian, and three sets of strata, i.e., Jiamuhe Formation, Fengcheng Formation and Shangwuerhe Formation, developed above and below the unconformities are the main reservoirs in Shawan sag. The conventional oil (gas)reservoir characterized with source-reservoir separation are developed in the northern onlap-truncation belt, the overpressure tight condensate gas reservoirs characterized with source-reservoir contiguity are developed in the central nose-shaped uplift belt, and the deep shale gas reservoirs characterized with source-reservoir integration are developed in the southern deep sag belt. Fengcheng Formation in the northern onlap-truncation belt is the reservoir as a whole, and its oil and gas enrichment is controlled by sedimentary facies. The high-quality reservoirs of coarse sand and small conglomerate in the northern onlap-truncation belt are developed in the distributary channel of fan delta front subfacies, which can provide the geological conditions for high and stable hydrocarbon yield. In Shawan sag, the dynamic and static configuration conditions of Permian oil and gas accumulation are superior, so the sag will be the most important exploration field of light oil and natural gas in Junggar Basin in the next 10 years.

Key words: Shawan sag, Permian, northern onlap-truncation belt, Fengcheng Formation, fan delta front

摘要： 准噶尔盆地沙湾凹陷二叠系呈现北浅南深、北窄南宽的"勺"状特征,自北向南划分为北部上超削蚀带(超削带)、中部鼻状隆起带(鼻隆带)和南部深凹带,其中,南部深凹带不仅地层发育齐全,而且地层迅速增厚,是沙湾凹陷的沉积中心和生烃中心。热演化模拟结果显示南部深凹带已达大规模生气阶段。沙湾凹陷二叠系内部发育2个二级不整合面,不整合面上下的佳木河组、风城组和上乌尔禾组为主力储集层。北部超削带发育源-储分离的常规油(气)藏、中部鼻隆带发育源-储相邻的超压致密凝析气藏、南部深凹带发育源-储一体深层页岩气藏。北部超削带风城组已整体成藏,其油气富集程度受沉积相带控制,发育扇三角洲前缘亚相分流河道粗砂—小砾岩优质储层,具备高产稳产的地质条件。沙湾凹陷二叠系油气成藏的动、静态配置条件优越,是准噶尔盆地未来10年轻质油和天然气勘探最重要的领域。

关键词: 沙湾凹陷, 二叠系, 北部超削带, 风城组, 扇三角洲前缘