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在可控震源数据采集中,有两个主要问题:(一)输出的振幅控制和相位控制;(二)振源产生的谐波畸变的抑制,为分析可控震源—大地响应的野外试验已验证这一点。这项正在进行的研究证实上述问题在刚性地面上(例如冻土地带)要比在土壤上严重得多。试验结果表明,在冻土地区的可控震源—地面响应中40Hz 大振幅可控震源共振和更高频率的(等于或大于10■z)大地基板共振占优势。而对地面作用力实行自适应闭合回路振幅控制确实能消除基板—地面去耦效应。在使整个扫描的输出作用力达到最大的过程中,远场井下信号分析表明,对地面作用力的相位同步和振幅控制比对基板或反作用块加速度的相位同步能提供更加稳定的下行子波。井下信号和可控震源加速器信号的定量频谱分析说明它们存在着严重的谐波畸变,并举例说明了用小于180度的相位增量旋转连续扫描相位可抑制所有的偶次谐波和某些有害的奇次谐波。
There are two major issues with vibroseis data acquisition: (i) the amplitude and phase control of the output; (ii) the suppression of the harmonic distortion caused by the vibrating source, and the field test for the analysis of the vibroseis-earth response Verify this. This ongoing study confirms that the above problems are much worse on rigid ground (eg permafrost) than on soils. The experimental results show that in the permafrost region, the 40Hz large-amplitude vibroseis resonance and the higher frequency (equal to or greater than 10 ■ z) earth substrate resonance dominate. However, the implementation of adaptive ground closure force amplitude control loop can indeed eliminate the substrate - ground decoupling effect. In the process of maximizing the output force of the whole scan, far-field downhole signal analysis shows that the phase synchronization and amplitude control of ground force can provide more stable downlink wavelets to the phase synchronization of substrate or reaction block acceleration. Quantitative spectral analysis of downhole signals and vibroseis signals shows that they have severe harmonic distortion and illustrate that rotating a continuous sweep phase with a phase increment of less than 180 degrees suppresses all even harmonics and some deleterious Odd harmonics