准噶尔盆地中侏罗统西山窑组与头屯河组间不整合面特征及其油气勘探意义

准噶尔盆地侏罗系顶、底及其内部不整合广泛发育，其中中侏罗统下部西山窑组和上部头屯河组之间的角度不整合尤为清楚。它表现为区域性不整合，沉积间断时限达4～10 Ma，剥蚀厚度达100～340 m。该不整合“面”的结构由不整合面之上的砂岩、不整合面之下的风化粘土层和半风化岩石组成，以砂岩-泥岩-砂岩的组合为主，平均厚度达70～90 m。依靠风化粘土层，不整合面之上头屯河组的砂岩形成了地层超覆圈闭，不整合面之下西山窑组的砂岩形成了地层削截不整合遮挡圈闭。油气勘探实践表明：该不整合面上、下是油气聚集的重要场所；该不整合面的后期掀斜演变对油气聚集和调整再分配产生了重要影响。

Characteristics of unconformity between the Xishanyao Formation and Toutunhe Formation of Middle Jurassic in Junggar Basin and its significance in petroleum exploration

Unconformities are widespread at the base,  top and within the Jurassic in Junggar Basin. Among these unconformities，the unconformity is quite distinct between the Xishanyao Formation in the lower part of Middle Jurassic and the Toutunhe Formation in the upper part of Middle Jurassic.With an  eroded thickness of 100～340 meters， it is a regional unconformity，and has a lacuna （or hiatus） of 4～10 Ma. On the unconformity，sandstones were deposited and immediately below it were the weathered clay interval and the semi weathered rocks just below the unconformity. Generally，the unconformity shows a succession of sandstone mudstone sandstone with a thickness of 70～90 meters. Based on the weathered clay intervals，the sandstones of the Toutunhe Formation formed a series of the stratigraphic onlap traps sealed by the weathered clay intervals at the bottom，while the sandstones of the Xishanyao Formation formed the truncated traps sealed by the weathered clay intervals at the updip. The petroleum exploration has proved that the areas above or below this unconformity are favourable areas for oil and gas accumulation. The late stage tilting of the unconformity has played an important role in the oil and gas accumulation, and adjustment and reallocation.