高精度地震探测陆域天然气水合物的有效性研究

摘要

In order to cooperate with the exploration of natural gas hydrate resources,the authors conducted the validity of the experimental study of high precision seismic reflection method in Muli area for the detection of natural gas hydrate in 2010.192 receive channels,2 m group spacing,8 m shot spacing,and 24 folds were used in reflection seismic survey.60 Hz geophone string (with 6 geophones) each received channel received seismic wave in the form of point array.Excitation sources were explosives,shot depth was 3～ 4 m,and shot charge was 1.2 ～ 2.4 kg.The seismic sections obtained by the method possessed high S/N ratio and resolution as well as obvious structural form characteristics.On the basis of a comprehensive analysis and interpretation of reflection seismic,well logging and geological data,the enrichment zones of natural gas hydrate were explained and validated borehole location was determined.The detection results were verified by DK9 borehole drilling in 2013.The gas hydrate reservoirs with large thickness were found 450m southwest of DK3 borehole.Experimental results show that it is difficult to detect natural gas hydrate directly by seismic method in the lower gas hydrate content's area,but through a comprehensive analysis of geophysical,geochemical and geological data in combination with drilling data,the enrichment zones of natural gas hydrate can be detected by seismic exploration.%为配合天然气水合物资源勘探工作,2010年在木里地区开展了高精度反射地震方法探测天然气水合物的有效性试验研究.反射地震采用192道接收,道间距2m,炮间距8m,覆盖次数24次,每道采用6个60 Hz检波器单点组合接收.激发震源使用炸药,井深为3～4m,激发药量为1.2～2.4 kg.采用该工作方法得到地震剖面的信噪比和分辨率较高,构造形态特征明显.综合分析解释反射地震和测井及地质资料,推断解释了天然气水合物富集地带,提出了验证孔位.2013年,该探测结果得到了DK9钻孔验证,在距离已发现天然气水合物DK3钻孔SE方向约450m处发现了厚度较大的天然气水合物.试验研究结果表明:在天然气水合物含量较低的测区,利用地震方法直接探测天然气水合物难度较大,但综合分析测区物化探和地质资料,结合钻井资料,能够通过反射地震探测天然气水合物的富集地带.