【摘要】 大容量气枪水库激发作为陆地震源的可行性与有效性已经得到成功验证.为进一步提高气枪震源激发效果,本文通过水库气枪激发试验对单枪容量为2000 in~3的气枪震源激发子波特征及规律进行了研究.依据近场水听器和远场短周期地震仪记录数据,分析气枪震源沉放深度、工作压力等不同激发条件对压力脉冲和气泡脉冲的影响.有助于人们根据不同尺度地下结构探测对震源激发信号的要求,调整气枪激发参数和激发环境,获得最佳激发效果.试验结果表明:(1)沉放深度对压力脉冲波形影响较小,其优势频率不随沉放深度而改变;(2)随着沉放深度从5 m增加到11 m,气泡脉冲的优势频率由5 Hz增加至7 Hz,其最大振幅亦近线性递增;(3)工作压力越大,激发压力脉冲能量越强,而对气泡脉冲的影响主要体现在主频降低.适合远距离深穿透地下结构探测的低频信号主要来自大容量气枪所激发气泡的反复振荡,由于气枪振荡过程非常复杂,本文通过较为简洁的数学和物理模型进行了解释.更多还原

【Abstract】 Large volume air-gun excited in a reservoir has been demonstrated successfully as an effective and feasible seismic source.In order to improve its efficiency further, the excitation characters of a 2000 in~3 air-gun were studied in a field experiment in a reservoir.Based on the records from near-field hydrophones and far-field seismographs, the dependence of the signature on the gun parameters including gun depth and firing pressure was analyzed.The results showed that;(1) pressure pulses were little affected by gun depth, its dominant frequency changed little with gun depth;(2) the dominant frequency of bubble pulses changed from 5Hz to 7Hz when the gun depth changed from 5m to 11m;(3) the energy of pressure pulses increased with firing pressure, but the dominant frequency of bubble pulses decreased.Low frequency signal fit for subsurface exploration in large scale is mainly created by the bubble oscillation, because of its complexity, a succinct Mathematical and Physical model was applied to explain the process.更多还原