青海三露天井田天然气水合物成藏的构造控制作用

自2008年中国首次在青藏高原祁连山冻土区钻获天然气水合物实物样品,木里煤田三露天井田已成为研究热点地区之一,但对于天然气水合物形成及保存的控制因素及分布规律的研究尚浅,阻碍了资源的勘探与开发。通过对三露天井田天然气水合物钻孔实际资料的统计,分析了井田构造格局,提出了研究区天然气水合物的形成过程,综述了构造对其成藏的控制作用。结果表明:1)天然气水合物是由烃类气体聚集成藏后随着青藏高原的快速隆起而抬升进入温压稳定带后形成水合物藏;2)研究区的构造分区分带性控制了天然气水合物在平面上的展布规律,构造运动决定了中侏罗煤系的沉降-生烃史和温压稳定带的形成,构造形态则可以为烃类气体的聚集提供通道、盖层及储存空间,而后期构造作用又会对前期形成的气藏及天然气水合物藏造成破坏。

Structural control of reservoir forming for natural gas hydrate in Sanlutian Well Field,Qinghai

In 2008, practical samples of natural gas hydrate(NGH)were drilled out in the frozen soil region of the Qilian Mountain in the Qinghai-Tibetan Plateau for the first time in China, and since then the Sanlutian Well Field in the Muli Coalfield becomes a research focus. But the lack of studies of the controlling factors of the NGH's formation and storage and the NGH's distribution hinders the NGH's exploration and exploitation. An analysis of the materials taken out of the NGH's boreholes in the Sanlutian Well Field and the well field's structural framework reveals the NGH's formation process in the study area, including the structure's role in controlling the NGH reservoir forming. It is concluded that: 1) a reservoir of the NGH is formed by hydrocarbon gases first, and then the NGH enters the temperature-pressure stable zone with Qinghai-Tibetan Plateau's rapid uplift to form a hydrate reservoir; 2) the study area's structure features of partition and zoning control the NGH's flat spreading; the structural movement decides the middle Jurassic coal measures' sedimentation, the hydrocarbon generation and the temperature-pressure stable zone's formation; the structural shape provides the channels, the cap rocks and the storage areas for hydrocarbon gases' enrichment; the later tectonism destroys the earlier gas reservoir and the NGH reservoir.