摘要
天然气水合物的存在改变沉积地层的声学特征,使得多道地震勘探成为发现天然气水合物的主要手段。地震识别首先通过地震剖面上独特的地震反射特征初步判断,然后经过地震反演获得地层的速度场分布,从而确定天然气水合物的存在及分布。南海北部陆坡是天然气水合物形成并稳定存在的有利区域,其多道地震反射剖面上具有明显的天然气水合物存在标志,包括强振幅的似海底反射(BSR)、振幅空白带、BSR与地层斜交等典型地震反射特征。文章以南海北部陆坡区的多道高分辨率地震数据为基础,探讨了天然气水合物地震识别的地震成像和波阻抗反演这二个方面的关键技术;研究结果不但突出了含天然气水合物地层的地震反射特征,而且得到与天然气水合物最相关的地层岩性参数———声波速度;地震反射特征与速度场异常分别为天然气水合物的识别提供了定性和定量的地球物理证据;根据声波速度场的分布,可以推断存在于研究区地层的天然气水合物主要分布在靠近BSR的上覆沉积地层中。
The presence of gas hydrate changes the acoustic properties of sedimentary strata, which makes the multi-channel seismic exploration a major method for identifying gas hydrate. A preliminary judgment is first made according to the specific reflectance signatures on seismic profile, and distribution of strata velocity field is then obtained through seismic inversion, so as to determine the occurrence and distribution of gas hydrate. The northern slope of South China Sea has favorable conditions for the formation and steady preservation of gas hydrate. Significant seismic reflectance signatures that can indicate the occurrence of gas hydrate exist on the multi-channel seismic reflection profile, such as BSR, blank reflection and oblique crossing of BSR with strata. Based on the high resolution multi-channel seismic data in the study area, this paper discusses the key techniques in respects of seismic imaging and post-stack inversion for identification of gas hydrate. The seismic reflection signatures of gas hydrate-bearing strata are defined and the lithologic parameter closely related with gas hydrate, i.e. acoustic velocity, is identified. The seismic reflectance signatures and abnormal velocity field provide both qualitative and quantitative geophysical evidences for identification of gas hydrate. According to the distribution of velocity field, it is inferred that the gas hydrate is mainly distributed in the overlying sedimentary strata near BSR in the study area.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2006年第9期49-51,共3页
Natural Gas Industry
基金
国家"863"计划(编号:2003AA611020)的部分研究成果。
关键词
天然气
水合物
地震响应
速度
识别
南海
大陆坡
natural gas, gas hydrate, seismic response, velocity, identification, South China Sea, north, continental slope
