中国大陆科学钻探孔区的数字三分量反射地震调查

Three-component seismic profiling at the Chinese Continental Scientific Drilling site

本文将简要介绍在大陆科学钻探孔区进行数字三分量地震勘探试验数据采集处理技术，以及取得的初步成果．鉴于结晶岩地区波场的复杂性，在剖面调查之前要先进行波场特征调查，才能确定三分量地震调查观测系统采集参数．数据处理中与水平分量处理有关的三个困难环节包括静校正、速度分析与动校叠加，必须有所创新．在大陆科学钻探工程中，三分量数字地震调查之所以放在终孔后才进行，主要是因为三分量地震解释要以钻孔资料和VSP成果为基础．如果没有岩芯物性测定资料或VSP纵横波速度计算曲线，横波速度剖面模式就难以建立，水平分量数据处理和解释就难以进行．与单分量地震调查相比，水平分量采集处理提供了转换波信息，可反映独特的很有意义的地质信息．在三分量数字地震调查X分量深度叠加剖面左半边深度2600—3400m区段出现密集的水平反射层，与Z分量反射剖面和变质岩片倾向不一致．对比主孔气体异常曲线可知，这些水平反射是地层中流体含量升高的反映．

This paper introduces the data-acquisition and processing method applied in the 3-component seismic investigation in Chinese Continental Scientific Drilling site as well as some primary results of the survey. In order to obtain good converted wave signals, primary wave-field investigation is required for designing the seismic configuration parameters. There are three difficulties should be overcome in the 3-component data processing, they include statics, S-wave velocity analysis and converted-wave stacking. The reason why the 3- component survey is usually performed after completion of the drilling and VSP investigation is because the dataprocessing and interpretation need drilling and VSP data. For instance, without core velocity measurements or VSP interval velocity data, one can hardly establish a reliable S-wave velocity model, and complete the X- and Y- component data processing and interpretation. Comparing with common Z-component surveys, horizontal components show the converted reflectors that can provide particular and significant information related to fluids or anisotropy of deep rocks. On the left part of the X-component depth-stack profile, a special layer of dense horizontal reflectors appears at depth 2600 - 3400 m, which is different from P-wave reflection profile and correlated to gas anomalies of CH4 and CO2, implying a newly-developed fluid and fracture zone.