| 海洋含水合物沉积层的速度频散与衰减特征分析 |
| |
| 引用本文： | 张如伟,李洪奇,文鹏飞,张宝金.海洋含水合物沉积层的速度频散与衰减特征分析[J].地球物理学报,2016,59(9):3417-3427. |
| |
| 作者姓名： | 张如伟 李洪奇 文鹏飞 张宝金 |
| |
| 作者单位： | 1. 中国石油大学(北京), 油气资源与探测国家重点实验室, 北京 102249;2. 国土资源部海底矿产资源重点实验室, 广州海洋地质调查局, 广州 510075 |
| |
| 基金项目： | 国家重点基础研究发展计划（2009CB219505）与国家高技术研究发展计划（2013AA092501）联合资助. |
| |
| 摘 要： | 随着水合物含量的增加,往往会引起纵、横波速度的增加,同时也会引起衰减的变化.针对含水合物沉积层的速度频散与衰减特征分析,有助于水合物含量的估计.本文以有效介质理论模型(EMT)为基础,研究了海洋未固结含水合物沉积层的纵、横波速度的非线性变化趋势.同时采用BISQ模型替代有效介质模型中的Gassmann方程,具体分析了全频带范围内海洋含水合物沉积层的速度频散与衰减特征.采用该模型,速度与衰减均随着水合物含量的增加而增加,且岩石孔隙度与泥质含量对衰减系数的影响较小.针对大洋钻探计划(ODP)164航次的实际数据,运用该模型方程计算采用声波测井数据(20kHz)与VSP数据(100Hz),分别获取了水合物稳定带的饱和度数据,平均在5%~7%之间,由于速度频散的影响,VSP估算结果要弱低于声波测井估算数据,均与实测保压取芯的甲烷含量数据、他人研究成果以及神经网络趋势预测结果均有着较好的一致性.对南海神狐海域三口钻位开展了水合物含量预测,与保压取芯结果有着较好的吻合关系.同时基于层剥离法提取该区域某地震测线BSR层的等效Q值,采用本文方法估算了该区域的等效天然气水合物含量15%~30%.数值模拟与实际应用结果表明:含水合物沉积层的速度频散与衰减特征均随着水合物含量的变化而变化,联合利用这一些变化特征,有助于天然气水合物含量的估计.
|
| 关 键 词： | 天然气水合物 有效介质理论 BISQ模型 速度频散 地震衰减 |
| 收稿时间： | 2015-04-18 |
The velocity dispersion and attenuation of marine hydrate-bearing sediments |
| |
| ZHANG Ru-Wei,LI Hong-Qi,WEN Pen-Fei,ZHANG Bao-Jin.The velocity dispersion and attenuation of marine hydrate-bearing sediments[J].Chinese Journal of Geophysics,2016,59(9):3417-3427. |
| |
| Authors: | ZHANG Ru-Wei LI Hong-Qi WEN Pen-Fei ZHANG Bao-Jin |
| |
| Institution: | 1. China University of Petroleum(Beijing), State Key Laboratory of Petroleum Resource and Prospecting, Beijing 102249, China;2. Key Laboratory of Marine Mineral Resources, Ministry of Land and Resources, Guangzhou marine Geological Survey, Guangzhou 510075, China |
| |
| Abstract: | P-wave and S-wave velocity will increase when the concentration of gas hydrate increases, and the attenuation will vary too. The analysis of velocity dispersion and attenuation for hydrate-bearing sediments (GHBS) would contribute to the estimate of gas hydrate concentration. Based on effective medium theory (EMT), we study the nonlinear variation feature of P-wave and S-wave velocity for marine unconsolidated hydrate-bearing sediments. Moreover, we use BISQ model to replace Gassmann equation in the EMT, and research the velocity dispersion and attenuation of hydrate-bearing sediments in the full frequency band. Based on this model, the velocity and attenuation always increase with the increasing amount of gas hydrate, and the rock porosity and clay content doesn't make any differences to the attenuation. After the numeral modeling, we apply the sonic logging (20 kHz) and VSP (100 Hz) data from Ocean drilling Program (ODP) leg 164 to obtain the concentration of gas hydrate stability zone (GHSZ). In the application, the average hydrate concentration of GHSZ from hole 995 in ODP leg 164 is about 5%~7%, consistent with the pressure core sample (PCA) data, Helgerud et al.'s research conclusions, and the prediction data from neural network (NN). Due to the velocity dispersion, the estimated hydrate concentration from VSP data is lower than the estimated results from sonic logging data. The prediction results of three hydrate stations (SH2, SH3 and SH7) from Shenhu area also coincide with the PCA, South China Sea. Moreover, based on the peak frequency method, the effective seismic quality factors (Q) of the BSR are estimated from the inline prestack seismic gathers. The Q-values suggest the effective saturation of gas hydrate estimated by this model fluctuates between 15%~30%. The results of numeral modeling and applications indicate that the velocity dispersion and attenuation of GHBS always vary with the concentration of hydrate. The study of velocity dispersion and attenuation feature for GHBS in the full frequency band would contribute to the estimate of gas hydrate concentration. |
| |
| Keywords: | Gas hydrate Effective medium theory BISQ model Velocity dispersion Seismic wave attenuation |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球物理学报》浏览原始摘要信息 |
| 点击此处可从《地球物理学报》下载免费的PDF全文 |
|
