汶川地震断裂带科学钻探工程2号孔350～800m井段的钻探泥浆气体组分变化

VARIATION OF DRILLING MUD GAS COMPONENTS AT 350～800m INTERVAL OF No.2 BOREHOLE OF SCIENTIFIC DRILLING FOR WENCHUAN SEISMIC FAULTED ZONE

以汶川地震断裂带科学钻探工程(WFSD)2号孔350～800 m井段的钻探泥浆中某些气体组分测定数据,以及2009-10-10～2010-05-24钻孔附近断裂带范围内里氏震级ML≥3.5的目录、断裂带岩芯岩性为基础,探讨钻探泥浆脱气气体组分异常与构造环境、地震活动的关系。研究结果表明,660～680 m井段附近岩石破碎程度达到最大,各气体归一值也出现明显的正、负异常,得到的最大、最小值所对应的井段也是面波震级MS 3.0以上余震的频发处,气体异常多数出现在岩石的裂隙、破裂面、断层处。

Based on data of some gas components in drilling mud at 350～800 m interval of No.2 borehole for WFSD and Richter earthquake magnitude ML≥3.5 catalog as well as lithologic character of cores from the faulted zone of Wenchuan earthquake,the authors investigated the relationships of anomalies of drilling mud de-gas gaseous components to tectonic environment and earthquake activity.The results show that the shattering of rocks is maximum at the interval of 660～680 m,the normalized values of various gases also show obvious positive and negative anomalies,and the intervals corresponding to the maximum and minimum values are places where aftershocks higher than the magnitude MS 3.0 frequently occur.The gas anomalies mostly occur in cracks in rocks,surface of fractures and faults.