托克逊凹陷伊拉湖构造成藏特点及其勘探意义

Hydrocarbon accumulation in the Yilahu structure and implication for exploration in the Toksun Sag, Turpan-Hami Basin

吐哈盆地托克逊凹陷伊拉湖构造1988年发现三叠系油气藏,此后该凹陷勘探未获新突破。从油源、储集层、盖层及油气运移条件看,伊拉湖构造至乌苏构造的区域属于同一成藏组合带,在中燕山期受乌苏断裂控制,晚燕山期以来受伊拉湖断裂控制。根据对伊拉湖构造成藏条件的解剖,该成藏组合带以二叠系为主要油源,以三叠系克拉玛依组和上三叠统下段为储集层,以上三叠统上段及以上地层为盖层和上覆岩层,具有较好的成藏条件。但包含伊拉湖构造的伊拉湖构造带南端晚侏罗世以后构造运动剧烈,油气藏保存条件较差,而伊拉湖断裂下盘沿乌苏断裂至乌苏构造的区域构造继承性发展,断裂发育较少,保存条件较好,是托克逊凹陷进一步勘探的有利方向。

The researches on oil and gas source, reservoir, cap rocks and oil and gas migration show that the Yilahu structure could be defined as a reservoir combination. The play was controlled by the Wusu fault in the Middle Jurassic and by the Yilahu fault in the Late Jurassic. The controlling factors of oil and gas accumulation in the Yilahu structure show that the play have good oil and gas accumulating conditions, with the Permian mudstone as the major source rock, sandstone of the Kelamayi Formation and the upper part of the Triassic as the reservoir, mudstone of the Upper Triassic and overlying strata as the cap rock. However, the Yilahu structure was transformed and the pools in it were damaged heavily by tectonic movements since the Cretaceous. Some anticlines between the Yilahu fault and the Wusu structure were developed successively on the early structures since the Cretaceous, because the faults were less developed in this area, the oil and gas migrated to these structures during Jurassic were preserved very well after Cretaceous, which should be the prospective exploration area in the Toksun Sag.