【作者】 王立明；

【导师】 刘保华；

【作者基本信息】 长安大学 ， 地球探测与信息技术， 2010， 博士

【摘要】 空气枪是海上地震勘探重要的人工震源。气枪震源子波信号的特征是影响勘探效果最重要的因素,同时震源子波还是地震资料处理解释中十分重要的参数,特别是叠前处理与地震模型正演和反演中必须输入的关键参数。气枪激发的高频震源子波信号能量强,频带宽,能探测浅部地层精细结构；而气枪激发的低频震源子波信号能远距离探测深部地壳甚至上地幔结构,把海上和陆上地壳、地幔结构联系起来。实际应用中,无论是单枪还是气枪阵列激发生成的子波,都可以通过现场实测得到,但通过实测得到的子波,需要耗费大量的人力、物力和财力,要求外部环境条件也较苛刻。气枪子波模型不但能方便的模拟出与实测值一样的子波波形,而且所要花费的成本很低,很大程度上有效的解决了气枪阵列设计过程中的难题,具有实测方法无法相比拟的优势。研究和实例表明,气枪震源性能稳定,激发子波一致性好,不随使用期增长而改变,保证了模拟子波正确性和可靠性。因此,开展气枪子波信号模拟研究有着非常重要的理论意义和实际应用价值。本文依据空气枪原理、特性及影响因素,总结了模拟实测子波信号的各种理想气体单枪子波模型。通过分析这些子波模型的模拟子波与实测子波差异问题,探索和发展了新的理想气体单枪子波模型,就是在新的子波模型中引入理想气体条件下的准静态开放式热力学系统。该模型在气枪工作压力较小时,模拟子波接近于实测子波；但是随着气枪工作压力不断增大,模拟子波越来越偏离实测子波,不能准确反映实测子波特性。针对这一问题,展开了工作并分析了原因,认为随着气枪工作压力增大,气枪内气体不再符合理想气体条件,所以用理想气体状态方程会造成很大误差。建立了范氏气体单枪子波模型。利用范德瓦尔斯非理想气体理论,把气枪内气体看成与气体实际行为相符合的范氏气体。由此引入比理想气体状态方程精度更高的范德瓦尔斯方程,通过与范氏气体条件下的准静态开放式热力学系统和气体气泡运动方程相结合,建立了范氏气体单枪子波模型。同时由于不同类型气枪激发出来的子波信号存在差异,所以范氏气体单枪子波模型能确定各类气枪参数,模拟相同类型不同容量气枪的子波信号。测试结果显示,增大气枪工作压力时,范氏气体单枪子波模型模拟的子波结果与实测子波偏离很小,仍然保持接近。发展和完善了范氏气体GI枪子波模型和范氏气体气枪阵列子波模型。由于范氏气体单枪子波模型能保证模拟子波正确性和可靠性,因此在此基础上建立了这两个子波模型。范氏气体GI枪子波模型是通过设置最高气体喷出量来控制子波信号；范氏气体气枪阵列子波模型是根据无论气枪阵列中的枪与枪间距有多远都会相互影响的思路建立。通过测试表明,这两个子波模型的模拟子波都能很好的与实测子波波形接近。根据上述理论和算法,研发了范氏气体气枪子波模拟软件。它能针对野外生产中的实际困难和要达到的目标,高效、准确、快速、节省的实现气枪阵列设计,得到性能优越的海上震源。采用范氏气体气枪子波模拟软件设计气枪阵列,得到的参数运用于海上地震勘探中,取得了很好的效果。更多还原

【Abstract】 Air-guns are the important artificial seismic source in offshore seismic prospecting. It is the most important factor that wavelet characteristics of air-guns affect the effect of seismic exploration. And the signature is also a very important parameter in seismic data processing and interpretation, which has to be inputted on pre-stack processing and seismic forward and inverse model. High frequency signature stimulated by air-guns prospects fine structure of shallow oceanic crust. Low frequency signature stimulated by air-guns explores deep oceanic crust and upper mantle from far distance.In practice, signature stimulated by air-guns or air-gun arrays may be obtained in actual measurement, but the measurements need much manpower, material resources and consume besides good external environment conditions. Not only signature simulated by the air-gun wavelet model can be close to measured signature, but also the air-gun wavelet model expends a little quantity of cost. The wavelet model has solved these questions easily and is superior to wavelet measurement. Researches and examples show that the performance of air-gun source is steady and the wavelet has good compatibility, which is unable to change with the lifetime rise. The wavelet model has these characteristics of validity and authenticity. Therefore, it has important value of the theory and application to study signature simulation.According to the principles, behaviors and influential factors of air-guns, various wavelet models of the single air-gun are concluded. Then the new single air-gun wavelet model of Ideal Gas is established from the difference between the modeling wavelet and the measured wavelet. The open quasi-static thermodynamic system in conditions of Ideal Gas is drawn in the new wavelet model. The modeling wavelet is close to the measured wavelet when the air-gun operation pressure is small. But with increase of the operation pressure the modeling wavelet greatly deviates from the measured wavelet. In view of the problem, the author judges that gas in the air-gun does not correspond to the conditions of Ideal Gas with increase of the operation pressure. So there is very big error caused by Ideal Gas Equation of State.The single air-gun wavelet model of Van der Waals Gas is established. When gas in the air-guns is regarded as Van der Waals Gas and Van der Waals Equation is drawn, the single air-gun wavelet model of Van der Waals Gas based on the open quasi-static thermodynamic system and the bubble oscillation theory is established. At the same time, the wavelets stimulated by different types of air-guns are non-uniform. The single air-gun wavelet model of Van der Waals Gas can determine various types of air-gun parameters to simulate signature of the same air-guns of different volume. Test results show that the signature simulated by the model remains close to the measured wavelet when the air-gun operation pressure increases.The GI gun wavelet model of Van der Waals Gas and the air-gun array wavelet model of Van der Waals Gas are developed. The single air-gun wavelet model of Van der Waals Gas has these characteristics of validity and authenticity, so the two wavelet models are established. The former controls the signature by setting the gas ejection. The latter is established by interaction between air-guns in the air-gun array. Acceptance tests demonstrate that the two models can be close to measured wavelet.Based on the theories and algorithms, the air-gun wavelet simulation software of Van der Waals Gas is programmed. Aimed at the difficulty and target in practice, it can efficiently, correctly, sparingly achieve the design of the air-gun arrays and the marine seismic source of predominant performance is obtained. It is good effects that the air-gun array parameters obtained by the design of the air-gun wavelet simulation software of Van der Waals Gas are applied into offshore seismic prospecting.更多还原