渤海海域气枪子波时空传输特征研究

Temporal and Spatial Transmission Characteristics of Air Gun Wavelet in Bohai Sea

渤海海域蕴藏着丰富的油气资源,具有很大的开发潜力,是当前我国最为重要的海上油气产地之一。海洋地震勘探作为最主要的勘探方法来探测渤海海域的油气资源及其他地质构造时,通常采用气枪阵列作为最主要的震源。由于渤海水深较浅,气枪子波的传输受海面和海底影响较大,气枪震源与接收点之间存在多个反射传播路径,会导致不同时间到达的波发生叠加,传播超过几公里的气枪子波是复杂的。本文系统地对影响气枪子波传输的许多因素进行了研究和分析,详细地分析了这些因素可能会对气枪子波传输造成的影响。建立了用来衡量气枪子波接收能量水平的参数,即均方根声压级(Root-Mean-Square-Level,SPLrms)参数与声暴露级(Sound-Exposuse-Level,SEL)参数,以及用来进行频率域分析的1/3倍频程分析方法,并且将其应用到了在渤海海域采集到的实际数据中,最终得出结论:均方根声压级参数与声暴露级参数较好地显示气枪子波接收能量水平大小及其随传输距离的变化,帮助从空间域上进行气枪子波传输特征的分析。而1/3倍频程分析方法也较好地体现了气枪子波在不同频带内的传输损耗及传输特征,从频率域上对气枪子波的低频部分与高频部分进行的分析和对比以及准确地观察某个频带内接收能量水平的具体变化。

The Bohai Sea contains abundant oil and gas resources and has great development potential.It is currently one of the most important offshore oil and gas producing areas in China.Marine seismic exploration is the main exploration method to detect oil and gas resources and other geological structures in the Bohai Sea,and airgun arrays are usually used as the main seismic source.Due to the shallow depth of the Bohai Sea,the transmission of airgun wavelets is greatly affected by the sea surface and the seabed.There are multiple reflection propagation paths between the airgun seismic source and the receiving point,which will cause the superposition of waves arriving at different times,and airgun wavelets that propagate more than a few kilometers.The propagation of airgun wavelet over several kilometers complicated.Many factors affecting the airgun wavelet transmission are systematically studied and analyzed,and the possible impacts of these factors on the airgun wavelet transmission are analyzed in detail.The parameters used to measure the received energy level of airgun wavelet,namely,the root-mean-square sound pressure level(SPLrms)parameters and the sound-exposuse-level(SEL)parameters,as well as the 1/3 octave analysis method used for frequency domain analysis,are established and applied to the actual data collection in the Bohai Sea.Finally,it is concluded that the root mean square sound pressure level parameter and the sound exposure level parameter better show the airgun wavelet.The received energy level and its change with the transmission distance help to analyze the characteristics of airgun wavelet transmission in the space domain.The 1/3-octave analysis method also better reflects the transmission loss and transmission characteristics of the airgun wavelet in different frequency bands.The low frequency part and high frequency part of the gasgun wavelet are analyzed and compared from the frequency domain,and the specific changes of the received energy level in a certain frequency band are accurately observed.