Researches On Stimulating Techniques Of The Seismic Waves In The Deep Sea

The basic source which was used in the marine seismic exploration at the early stage was the explosive one. However, the explosive source has some obvious disadvantages in the course of using. Firstly, the exhaust gases produced by the explosives can form shocks in the water, which is a kind of interference in the seismic survey of high-resolution. What's more, it is unacceptable to install all the explosives on the detonators since the explosives are extremely dangerous, and the detonators can only be installed while using. Therefore, the method of common midpoint cannot be effectively achieved if the interval of blasting is too long. In addition, it is inevitable to generate the water pollution for using the explosives. As a result, the non-explosive source appeared in the marine seismic exploration, and the air-gun source as a new force soon occupied the main position.The air-gun source was invented in 1964 by Stephen Chelminski from Bolt, an American company. In late 60s to early 70s of the 20th century, Anton Ziolkowski, Schulze Gattermann R, etc. established the theoretical model of the air-gun arrays according to the reducing method of the air-gun bubble oscillations, which became the theoretical base of using the air-gun source.The marine seismic exploration of high-resolution is extremely demanding to the source excitation technique in the conditions of complex geological structure, and the good excitation technique of seismic waves can produce better sub-waves and bring many conveniences for process the seismic information, so the source research is of great significance. The air-gun has lots of characteristics, such as producing similar sub-waves, stable performance, wide frequency range, abundant components of high frequency and low frequency, to name just a few. Nowadays the air-gun source has been used most widely in the marine seismic exploration. The far-field sub-wave as a very important parameter of the air-gun source costs too much manpower and too many material resources in the actual measurement, but compared with the actual measurement, the theoretical model of the air-gun arrays which can solve a series of problems effectively appearing in the conditions of different excitation and different reception in the course of designing the actual air-gun arrays has incomparable advantages. At present, the researches in this aspect remain in the stage of applying the imported air-guns and related software. There are almost no further researches on the transformation and improvement of the air-gun arrays in the conditions of complex geological structure in deep water areas.According to the theory of free bubble oscillation, the source in the work process will produce shocks which can reduce the quality of collected seismic data and the height of signal to noise ratio. On the basis of the nucleus software this thesis will carry out a systematic study of air-guns source used in the marine seismic exploration from the following aspects:1. The research on the single guns, the cluster guns, and the stimulation wavelet and sub-array of coordinate guns2. The stimulation wavelet with numerous sub-arrays and the optimization of air-guns3. The stimulation and research of the source wavelets of different capacity and depth4. The stimulation and research of sub-wave in different depth of sub-wave and different delay of air-gun5. The research on the amplitude of sub-wave, the peak-peak, the p/b ratio and the spatial distribution and direction of capacity6. The research on the volume array and the delayThis thesis aims to present the best space of cluster guns, the relationship between the sinking depth of sub-array and the primary and p/b ratio of the wavelet, the relationship between the space of sub-array and the primary and p/b ratio and get the source design of the volume array and the delay, which will pave the way for the establishment of the wavelet library, provide the theoretical foundation and basis for the seismic exploration in the deep sea, and form an optimized source design for the marine seismic exploration.