沙漠区可控震源“黑三角”干扰波分析及压制方法

Suppression of“black triangle”interference in vibroseis seismic data from desert areas

沙漠区可控震源地震资料存在“黑三角”强振幅干扰波,给资料处理带来极为不利的影响,“黑三角”干扰波压制困难是目前沙漠区可控震源资料处理的技术瓶颈之一。探讨了沙漠区可控震源“黑三角”干扰波的形成机理,借助数值模拟正演,结合多地沙漠区可控震源和炸药震源实际地震记录,对比分析了可控震源与井炮的“黑三角”干扰波的区别。认为“黑三角”干扰波的特点有:近震源附近能量最强,随着离震源的距离加大能量逐渐变弱,呈杂乱不相干状态,频带从几赫兹到近百赫兹;能量强弱与探区的地震地质条件密切相关;分布范围与低降速带的速度密切相关。开展了防假频时频分析异常振幅衰减、子波统计的异常振幅衰减、f-x域分频异常振幅衰减和非均匀相干噪声衰减等技术应用研究,进行了沙漠区可控震源和炸药震源实际地震资料的“黑三角”干扰波压制处理和RTM偏移成像,结果表明:可控震源资料浅层的处理结果比炸药震源的好,其深层的处理结果比炸药震源的稍差。防假频时频分析异常振幅衰减方法和非均匀相干噪声衰减方法串联应用可获得较好的“黑三角”干扰波压制效果,同时依据多块三维地震资料的处理结果认为:在一般厚度的沙漠区的中浅层勘探中可控震源是可行的,但在巨厚沙漠区的深层勘探中可控震源还存在一定问题,采用深井炸药震源会更好。

The suppression of“black triangle”interference(BTI)is one of the technical bottlenecks in the processing of vibroseis data from desert areas.In this study,the formation mechanism of“black triangle”interference noise was discussed,and the differences between“black triangle”interference waves from vibroseis and explosive sources were analyzed.The following characteristics of“black triangle”interference were identified:the noise energy is the strongest in the near field and gradually decreases moving away from the source;the noise appears chaotic,with a frequency content from several Hz to nearly 100Hz.The energy intensity is closely related to the seismic and geological conditions of the exploration area,whereas the energy distribution is strongly controlled by the velocity of the seismic waves in the low-velocity zone.In this study,non-uniform coherent noise attenuation was implemented,as well as three abnormal amplitude attenuation techniques,namely anti-aliasing time-frequency analysis,wavelet statistics,and f-x domain frequency division.Interference suppression processing and reverse time migration on field data from vibroseis and explosive sources with“black triangle”interference were conducted.The results showed that the quality of the shallow layer obtained from vibroseis data processing was higher than that from explosive source data.However,the quality of the deep layer from vibroseis data was slightly worse compared to that from explosive source data.The combination of anomaly amplitude attenuation of anti-aliasing time-frequency analysis with non-uniform coherent noise attenuation can effectively suppress the“black triangle”interference.The application of the vibroseis technique to the exploration of intermediate and shallow layers in desert areas with ordinary thickness is feasible.Conversely,the implementation of such technique in the exploration of desert areas with thick accumulation of sand is not feasible,for which the use of deep-well explosive sources is preferable.