青海木里地区冻土层、断层分布特征与天然气水合物成藏条件分析

Fault and frozen soil distribution characteristics of Muli natural gas hydrate area in Qinghai Province

以往研究表明冻土层及断层是陆域冻土区天然气水合物重要成藏要素,为了研究木里天然气水合物地区的断层及冻土层分布情况和天然气水合物成藏条件,应用音频大地电磁测深对木里试验区进行了冻土层及断层构造调查。依据试验区电性结构划分出了5组断层和4个断层构造发育区,其中F_3断层发育规模最大。试验区冻土层发育不均匀,平面以岛状特征分布,平均厚度超过60 m,划分了3个冻土层发育区。分析了天然气水合物成藏与冻土层、断层构造之间的关系,结合冻土层及断层构造条件,试验区东部F_(3-3)至F_(3-5)及F_4断层附近为天然气水合物成藏有利区。

Previous studies show that frozen soil and fault are important reservoir-forming factors of natural gas hydrate in land-based frozen area. In order to study the fault and frozen soil distribution situations of natural gas hydrate in Mull area, the authors investiga- ted distribution characteristics of frozen soil layer and fault structures of the study area through electromagnetic test. Based on electri- cal characteristics of resistivity profile of the test area in combination with geological setting, the authors recognized five groups of fault layers in the study area, with four of them possessing the biggest development scale. Frozen soil layer development area within the study area can be divided into 3 sub-areas, and fault layer structure development area can be divided into 4 sub-areas. The au- thors also analyzed the relationship between natural gas hydrate reservoir-forming condition, frozen soil layer and fault layer structures. By combination of frozen soft layer with area of developed fault layer structure, the authors infer that the east part from F3.3 to F3.5 and the place near F4 fault layer are natural gas hydrate reservoir-forming favorable areas.