天然气水合物层和游离气层的地震反演识别——布莱克海台USGS95-1测线应用实例  

Identification of Gas-hydrate Sediments and Free Gas Layer Using Seismic Inversion Method:A Case Study of Line USGS95-1 in Blake Ridge

作　　者：李敏锋[1] 刘学伟[1] 白杰[1] 童庆佳[2] 

机构地区：[1]中国地质大学"地下信息探测技术"教育部重点实验室,北京100083 [2]中国地质大学地球物理与信息技术学院,北京100083

出　　处：《现代地质》2007年第1期105-110,共6页Geoscience

基　　金：国家"863"计划项目(2001AA611020);国家重点基础研究发展规划项目(G20000467)

摘　　要：利用基于弹性波阻抗的AVO反演方法对美国布莱克海台实际水合物存在区域的USGS95-1测线进行处理,得到了地震纵波波阻抗和横波波阻抗,并据此计算出泊松比和拉梅系数等弹性参数。对反演得到的各弹性参数分析发现:与同沉积的水饱和地层相比,含水合物的地层具有高的波阻抗和拉梅系数;而游离气层具有低的纵波波阻抗、泊松比和拉梅系数。据此推断出该测线上水合物层和游离气层的分布范围。认为波阻抗剖面和拉梅系数剖面上的近似平行于海底的高值带指示水合物层,且水合物层下伏所圈闭的低泊松比和低纵波波阻抗区域指示游离气的存在;还发现该条测线上的BSR主要是由其下的游离气的聚集引起。Compressional-wave impedance and shear-wave impedance of line USGS95-1 from Blake Ridge are obtained using elastic-impedance inversion method. Also, they are used to calculate Possion＇s ratio and Lame parameter of this line. All these elastic parameters are analyzed to identify the gas-hydrate sediments and free gas layer. The results show that the impedance and Lame parameter of the sediments containing gas hydrates are higher than those of the media with saturated water at the same depth, but for free gas layer, these two kinds of elastic parameters, with Possion＇s ratio, become very low. Therefore, the gas-hydrate area and free gas area can be outlined respectively according to these characteristics. The zone of paralleling bottom with high impedance and Lame parameter indicates the gas-hydrate layer, and the area with low impedance and Possion＇s ratio trapped by gas-hydrate layer below it symbolizes the accumulation of free gas. The analysis also shows the main factor that causes the BSR of this line is the free gas below it.

关 键 词：弹性波阻抗 AVO 天然气水合物 泊松比 拉梅系数 

分 类 号：TE132.2[石油与天然气工程—油气勘探] P631.4[天文地球—地质矿产勘探]