基于尖脉冲子波的高分辨率气枪震源设计

Optimization design of high-resolution air gun source based on spike wavelet

1.中海石油(中国)有限公司天津分公司,天津 300459;
2.中国海洋大学海洋地球科学学院,山东青岛 266100

1. Bohai Petroleum Institute,Tianjin Branch of CNOOC(China) Limited,Tianjin 300459,China;
2. College of Marine Geosciences,Ocean University of China,Qingdao 266100,China

高分辨率气枪震源的设计是海上油气资源勘探的关键环节之一。分析震源子波形态与分辨率的关系,确定以尖脉冲子波作为震源优化的依据。基于非理想气体条件气枪子波模型对不同容量气枪的子波进行模拟,定量分析了不同容量气枪的主脉冲峰值及达到峰值的时间。提出通过调整阵列中不同容量气枪延迟激发时间和沉放深度,使阵列中各气枪主脉冲峰值同相叠加以构建尖脉冲子波的方法。在常规阵列的基础上设计了两种尖脉冲气枪阵列,并与常规阵列进行子波和频谱对比,结果表明:水深为20m的条件下,基于尖脉冲子波设计的阵列较常规阵列虚反射效应和陷波点效应的压制效果更好;主峰值、峰-峰值和初泡比分别增大11.6%,12.4%,16.4%;兼顾了高频和低频,有效频宽增大14.5%;能谱展布范围更广,能量下传能力更强,提高了信噪比和分辨率。

The optimization design of high-resolution air gun source is crucial to offshore hydrocarbon exploration.According to the relationship between source wavelet form and seismic resolution,the spike wavelet is used as the basis for source optimization.Based on wavelet simulation for different air gun capacities using a wavelet model in non-ideal gas conditions,quantitative analysis is performed on the peak value of the main pulse and the time to reach the peak for different air gun capacities.Thus,a spike wavelet is constructed by adjusting the delayed excitation time and setting depth of air guns with different capacities in the array to achieve in-phase stacking of main pulse peaks.We design two kinds of spike-wavelet air gun arrays on the basis of conventional arrays and investigate their wavelets and spectra.The results show that spike-wavelet arrays perform better than conventional arrays in suppressing ghost reflections and trapped waves.Main peak value,peak-to-peak difference and amplitude ratio of the first pressure pulse to the first bubble pulse increase by 11.6%,12.4% and 16.4%,respectively.Both high frequencies and low frequencies are expanded;the effective bandwidth is increased by 14.5%;more energy could travel downward to improve signal-to-noise ratio and resolution.

国家自然科学基金项目(91958206)和中海石油(中国)有限公司“七年行动计划”重大科技专项(CNOOC-KJ135ZDXM36TJ08TJ)共同资助。

10.12431/issn.1000-1441.2024.63.04.004