基于遗传算法的天然气水合物似海底反射层速度结构全波形反演  

The genetic algorithm based velocity structure waveform inversion for gas hydrate bottom simulating reflection (BSR)

作　　者：霍元媛[1,2] 张明[3] 

机构地区：[1]中石化华北分公司勘探开发研究院,河南郑州450006 [2]中国地质大学(北京),北京100083 [3]广州海洋地质调查局,广东广州510760

出　　处：《石油地球物理勘探》2010年第1期55-59,共5页Oil Geophysical Prospecting

基　　金：国家863计划"南海北部天然气水合物首钻目标优选关键技术"课题(编号2005AA611050)

摘　　要：似海底反射层的速度异常是识别天然气水合物的重要标志。本文基于遗传算法提出了一种针对天然气水合物似海底反射层的全波形反演方法。这种方法分为全局搜索与局部搜索两部分,即首先使用遗传算法进行旅行时反演得到背景速度模型,然后以其作为初始模型,使用共轭梯度算法进行全波形反演。对含噪数据的数值试验表明,该算法具有较高的稳定性,并确定了进行天然气水合物似海底反射层全波形反演的遗传算子。将这种波形反演方法应用于我国南海北部海域的天然气水合物研究,得到了分辨率高于常规速度分析的似海底反射层速度结构,并识别出似海底反射层的速度异常,为准确识别天然气水合物层和游离气层及研究其分布特征和形成机制提供了基础;反演结果也同时证明了本文方法的高稳定性以及对天然气水合物似海底反射层速度结构研究的适用性。The velocity anomaly of Bottom Simulating Reflection (BSR) is an important sign for detection of gas hydrate.Based on genetic algorithm a full waveform inversion method which can be utilized to identify gas hydrate BSR was presented in this paper.The method contains two steps,the global searching and the local searching,at first the genetic algorithm is utilized to conduct travel time inversion so that the background velocity model is obtained,then with the velocity model as initial model the full wave form inversion is conducted by using of conjugate gradient algorithm.Numerical testing for noisy data shows that the algorithm has a good stability,and the generic operator which is used to conduct gas hydrate BSR full wave form inversion was determined.By applying the wave form inversion algorithm in gas hydrate studies in northern part of South China Sea,The BSR velocity structure whose resolution is higher than routine velocity structure is obtained,and the velocity anomaly of the BSR was also identified,the studies laid foundation for detection of gas hydrate layers and free gas layers and for studies of their distribution and formation.The inversion results proved that the algorithm is very stable and it is applicable for studies of gas hydrate BSR's velocity structure.

关 键 词：似海底反射层 天然气水合物 波形反演 遗传算法 速度结构 共轭梯度算法 南海北部海域 速度异常 

分 类 号：P744.4[天文地球—海洋科学]