疏松地表对震源信号的影响与施工方法的改进

Impact of loose surface on vibrator signal and the improvement in field operation

(中国石油集团东方地球物理勘探有限责任公司采集技术支持部，河北涿州072751)

Acquisition Technical Support Department, BGP,CNPC，Zhuozhou 072751, China

在疏松地表地区，可控震源及其与地表的耦合问题是引起振动信号畸变的主要因素。振动信号的畸变包括振幅畸变和相位畸变，这些畸变会降低相关信号的质量，而相位畸变对相关信号的影响尤为严重。在伊朗AMK三维工区，从表层条件、震源质量控制参数(重点讨论了平均相位和峰值相位)、不同相位延迟下相关信号的变化，以及相位与相关信号质量的关系几方面，对相位畸变产生的原因以及对相关信号质量的影响进行了探讨，提出了降低相位畸变程度和改善相关信号质量的措施。实际资料分析表明，在速度较低的疏松地表地区，振动信号容易发生畸变，使相关信号的旁瓣增大，而引起畸变的主要原因是可控震源与疏松地表之间的耦合问题。为此，提出了增加一次空振的扫描方式，即第一次振动的扫描信号不予记录，而是压实地表，改善可控震源与疏松地表之间的耦合关系，然后再按常规方式进行震源扫描。实际应用结果表明，该方法使记录质量得到了较大的改善，分辨率和信噪比都得到了提高。

In the area with loose surface, the coupling problem between the vibroseis and the surface is the main factor for vibrating signal distortion. The vibrating distortion includes amplitude distortion and phase distortion, which may low down the quality of correlation signal, especially the phase distortion. In the loose surface farmland of 3-D survey in AMK area, Iraq, the phase distortion is quite serious. The reasons for phase distortion and the impact for the quality of related signals were discussed in several aspects, such as surface condition, vibrator quality control parameters (mainly about average phase and peak phase), changes of related signals under different phase delays, and the relationship between phase and quality of related signals. Some measures were proposed to decrease the phase distortion and improve the quality of related signals. The actual dada analysis indicates that vibrating signals easily get distorted and the side lobe of related signal bigger in the area with low velocity and loosing surface mainly because of the coupling condition between vibroseis and loosing surface. Therefore, the sweep means of adding one time no-vibrating was proposed before conventional vibroseis scanning, which means that 1) the sweep signal of the first vibration will not be recorded, 2) the surface is impacted to improve the coupling condition between vibroseis and loosing surface, and 3) the regular means is utilized to scan the vibroseis. The results show the recording quality has been greatly improved and the resolution and S/N ratio increased.