哈拉湖冻土区地震波场特征与天然气水合物成矿潜力分析

摘要

Halahu depression in the south of Qilian Mountain is a key region in gas hydrate exploration.The results of seismic exploration show that the shallow lateral velocity reversion discloses that the frozen zone is well developed,and seismic reflection section and three-instantaneous information reveal that Halahu Depression is a composite basin:After the Indosinian orogenic eruption and the Himalayan movement,the Late Paleozoic-Mesozoic residual basin which was developed on the crystalline base of the Caledonian phase furthcr formed as a foreland basin deep in the south and shallow in the north,with the deposition of Cenozoic loose sediments about 300 ～ 1200 m in thickness.Under the influence of complex tectonic movement,the strata were severely damaged;in addition,the quality of hydrocarbons source rock was also poor,the formation time of the permafrost was too late to preserve natural gas because the early faults could lead to gas escaping and regional cap layer was nonexistent.In summary,applying hydrate mineralization theory,the authors consider that the metallogenic potential is poor.%南祁连盆地哈拉湖坳陷地处青藏高原东北缘,是我国高原冻土区水合物勘查的重点区域,通过地震勘查发现:浅层倒转叠加速度场揭示了测区冻土层比较发育,反射剖面结果和三瞬信息则揭示了哈拉湖坳陷为复合型盆地:加里东期结晶基底上发育的古生代—中生代盆地,经过印支期造山剥蚀后,在喜马拉雅运动作用下,进一步形成南深北浅的前陆盆地,并沉积了约300～1 200m厚的新生代松散沉积物.测区受复杂构造运动的影响,地层破坏严重,且烃源岩品质较差,冻土形成时间晚,与导气断裂形成时间耦合性也差,区域性盖层缺乏,应用水合物成矿理论综合分析测区水合物成矿潜力较差.