本文選題：子波模型 + 立體槍陣�。� 參考：《中國海洋大學》2015年博士論文

【摘要】：海上氣槍陣列被廣泛用于海上地震勘探。因其具有能量大、穩(wěn)定性好、應用范圍廣等特點而成為地球物理學家研究的熱點。隨著海上高分辨率地震勘探的發(fā)展,海上寬頻震源已成為高分辨率地下成像的基礎。立體氣槍陣列可以很好地解決有震源虛反射引起的陷波效應,拓寬震源信號的有效頻帶,獲得理想的寬頻地震波信號。氣槍震源的遠場子波是不僅是衡量震源性能的重要指標,還是地震資料處理中的重要輸入數(shù)據(jù)。實際中可通過現(xiàn)場實際測量來獲取確定性的遠場子波記錄,但對于氣槍震源來說,其設計具有很大的靈活性與多樣性,需要反復試驗來獲得最佳槍陣設計。如果僅通過現(xiàn)場實測的方法來進行驗證,則會耗費大量時間和費用。氣槍子波模型則可以方便地對槍陣的遠場子波進行模擬,極大地提高了槍陣設計的效率,并且可以對槍陣信號進行全面的研究,包括其氣泡半徑、氣泡壁速度、槍陣信號的方向性等。而氣槍本身的子波一致性和穩(wěn)定性保證了這種方法的可靠性。氣槍子波模型方法的實現(xiàn)主要依賴于模型本身的合理性和準確度,因此,進行氣槍信號模擬研究,建立精確的氣槍子波模型具有很高的研究價值和實際意義。本文首先對氣槍的運作原理及其信號產(chǎn)生及影響因素過程進行了詳細描述,總結了前人建立的氣槍子波理想模型,以及對理想模型的各種修正。在現(xiàn)有的范氏氣體氣槍子波模型的基礎上,考慮震源虛反射對單槍氣泡振蕩過程的影響。震源虛反射是海面對氣槍上行壓力波的反射,因此也會連同靜水壓力對氣泡產(chǎn)生壓力影響,從而對信號子波有改造作用。由于不同類型的氣槍在構造上的差異而造成了在相同激發(fā)參數(shù)和條件下產(chǎn)生的信號子波有所差異,因此需要對依賴于實際氣槍類型的參數(shù)根據(jù)實測子波進行標定。而對子波進行實際測量時,記錄系統(tǒng)本身存在的頻率響應和采樣周期會對采集到的信號子波產(chǎn)生一定的影響,因此在進行標定過程中需要將模擬所得的子波進行濾波和重采樣之后再與實際資料進行比對,以保證標定結果的準確性。最終模擬的子波與實測結果非常相近。在建立的氣槍單槍子波模型基礎上發(fā)展了氣槍陣列子波模型,考慮了槍陣內(nèi)氣槍間的相互干擾作用等因素,最終的模擬結果與實測資料比較接近。研究立體延時氣槍陣列激發(fā)理論,建立了延時激發(fā)的氣槍陣列子波模型。對立體槍陣設計方法及其效果進行了研究,探討了立體槍陣的深度組合、深度間隔以及氣槍層數(shù)等對虛反射壓制效果的影響。根據(jù)已有的立體震源設計方法,結合信號子波模擬模型,針對實際海上勘探要求和實際條件,設計并對比了兩層和四層氣槍震源,最終試驗效果證明了所設計的立體槍陣的優(yōu)勢,取得了良好的應用效果。
[Abstract]:Offshore air gun arrays are widely used in offshore seismic exploration. Because of its large energy, good stability and wide range of application, it has become a hot spot of geophysicists. With the development of offshore high-resolution seismic exploration, offshore broadband seismic source has become the basis of high-resolution underground imaging. The stereoscopic air-gun array can solve the notch effect caused by virtual reflection of the source, widen the effective frequency band of the source signal, and obtain the ideal wide-band seismic wave signal. The far-field wavelet of air-gun source is not only an important index to measure the source performance, but also an important input data in seismic data processing. In practice, deterministic far field wavelet records can be obtained by field measurements, but for air gun source, its design is flexible and diverse, so it is necessary to repeatedly test to obtain the best gun array design. If it is verified only by the method of field measurement, it will cost a lot of time and cost. The air gun wavelet model can simulate the far field wavelet of the gun array conveniently, greatly improve the efficiency of the gun array design, and can conduct a comprehensive study of the gun array signal, including its bubble radius, bubble wall velocity. Directionality of gun array signals, etc. The wavelet consistency and stability of the air gun itself ensure the reliability of this method. The realization of the air gun wavelet model mainly depends on the rationality and accuracy of the model itself. Therefore, it is of great research value and practical significance to study the air gun signal simulation and establish an accurate air gun wavelet model. In this paper, the operating principle of the air gun and its signal generation and influencing factors are described in detail, and the wavelet ideal model of the air gun established by the predecessors is summarized, as well as the modification of the ideal model. Based on the existing van's gas gun wavelet model, the effect of hypotopic reflection on the oscillating process of single gun bubble is considered. The virtual reflection of the seismic source is the reflection of the upward pressure wave of the air gun on the sea surface, so it will also influence the bubble pressure together with the hydrostatic pressure, thus the signal wavelet can be modified. Due to the difference in structure of different types of air gun, the signal wavelet produced under the same excitation parameters and conditions is different, so it is necessary to calibrate the parameters depending on the actual type of air gun according to the measured wavelet. In the actual measurement of wavelet, the frequency response and sampling period of the recording system will have a certain impact on the signal wavelet. Therefore, in order to ensure the accuracy of calibration results, it is necessary to filter and resample the simulated wavelet and compare it with the actual data in the process of calibration. The simulated wavelet is very close to the measured results. The air gun array wavelet model is developed on the basis of the single gun wavelet model, and the interaction between the air guns in the air gun array is considered. The simulation results are close to the measured data. In this paper, the theory of stereoscopic delay air gun array excitation is studied, and the wavelet model of air gun array excited by delay excitation is established. The design method and effect of stereo gun array are studied, and the effects of depth combination, depth interval and number of air gun layers on the effect of virtual reflex suppression are discussed. According to the existing methods of stereo seismic source design, combined with the signal wavelet simulation model, according to the actual requirements and actual conditions of offshore exploration, the two-layer and four-layer air-gun seismic source is designed and compared. Finally, the experimental results show the advantages of the designed stereo gun array, and good application results are obtained.
【學位授予單位】：中國海洋大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：P631.46

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本文編號：1832609