發(fā)布時間：2019-01-17 08:36

【摘要】：在近地表傳播的地震波,由于地下巖層對地震波有吸收作用,使得它的高頻能量發(fā)生衰減。地震波的衰減主要包含：地震波傳播過程中的球面擴散效應,地層傳輸效應,巖石骨架的粘彈性性質,巖石的孔隙率,孔隙中的流體成分等。在這之中的前兩項衰減與地震波的頻率關系不大,后幾項的吸收衰減與頻率有很大關系,而prony變換可以描述頻率同吸收衰減系數之間的關系。因此,它可以應用于檢測吸收異常帶。一直以來,研究儲層的吸收作用,一般采用Fourier變換的方法,它通過線性濾波來間接的求取吸收系數,制約了預測的精度。而prony變換方法利用阻尼諧波對信號進行分解,通過非線性濾波直接求取吸收系數,同時擁有多級質控,提高了儲層含氣性預測的精度。本文首先介紹了地震波吸收衰減的各種機制,分別從宏觀和微觀上進行了列舉。從宏觀上看幾何擴散、非彈性衰減、傳輸損耗、波型轉換、散射以及折射角和臨界角；從微觀上看是摩擦作用、不可逆熱傳導作用、晶體不完整性、電化學影響、毛細管影響和液體流動作用。然后列舉影響地震波衰減的各種因素,例如巖性、頻率、壓力、溫度、應變振幅以及速度同孔隙流體飽和度。在地層吸收的基礎上,探討了地震波吸收衰減的參數如品質因子、吸收系數和對數衰減量以及衰減系數及其相互之間的關系。根據prony算法原理在matlab軟件中編寫prony變換的程序,實現prony變換的擬合,對信號的分析和重構。然后,通過prony變換的基本步驟,選取地震資料,進行prony變換,驗證prony算法的擬合。Prony方法能根據測量數據很快求得所需的信息,并且能夠很好地擬合數據。1999年,Mitrofanov基于模型研究了prony濾波的有效性。這些模型向我們預示了,在地震資料處理中,為獲取有關介質結構和含油氣遠景區(qū)帶的信息,prony濾波具有相當大的潛力。通過prony濾波的步驟以及最佳參數的設置,在地震剖面上進行吸收濾波處理,同時將原始的地震剖面圖與濾波結果圖進行對比,研究地層的含氣性分析。prony吸收衰減濾波技術通過阻尼諧波對地震信號進行非線性濾波,能夠直接獲取儲層的吸收系數。同時prony吸收濾波在多級質控的條件下,其對含氣性的預測精度比Fourier變換技術要高。經吸收濾波后的剖面,其響應特征是與輸入剖面相比同相軸弱化或者消失。根據參數選擇的結果可知,有必要增加井點的信息來確定prony吸收濾波的最佳參數。在含氣的儲層中傳播的地震波,會發(fā)生較強的能量吸收響應特征,但是這種現象在原始地震記錄上很難被發(fā)現。然而,經過吸收濾波后,這種現象就能夠被發(fā)現。這樣能方便我們更好的識別含氣儲層。
[Abstract]:The seismic wave propagating near the surface of the earth's surface attenuates its high frequency energy due to the absorption of the seismic wave by underground rock strata. The attenuation of seismic wave mainly includes: spherical diffusion effect, stratum transmission effect, viscoelastic property of rock skeleton, porosity of rock, fluid composition in pore and so on. The first two term attenuation has little relation to the frequency of seismic wave, while the absorption attenuation of the last few terms has a great relationship with frequency, and the prony transform can describe the relationship between frequency and absorption attenuation coefficient. Therefore, it can be used to detect absorption anomalies. For a long time, the absorption of reservoir is studied by Fourier transform, which indirectly calculates the absorption coefficient through linear filtering, which restricts the accuracy of prediction. The prony transform method decomposes the signal by damping harmonics and obtains the absorption coefficient directly by nonlinear filtering. At the same time, it has multistage quality control, which improves the accuracy of reservoir gas bearing prediction. In this paper, the mechanisms of seismic wave absorption and attenuation are introduced and listed from macro and micro aspects. From the macroscopic point of view, geometric diffusion, inelastic attenuation, transmission loss, wave type conversion, scattering, refraction angle and critical angle; From the microscopic point of view, it is friction, irreversible heat conduction, crystal imperfection, electrochemical effect, capillary effect and liquid flow. Then various factors affecting seismic wave attenuation such as lithology frequency pressure temperature strain amplitude and velocity with pore fluid saturation are listed. On the basis of stratigraphic absorption, the parameters of seismic wave absorption and attenuation such as quality factor, absorption coefficient and logarithmic attenuation amount, attenuation coefficient and their relationship are discussed. According to the principle of prony algorithm, the program of prony transform is written in matlab software, the fitting of prony transform is realized, and the signal is analyzed and reconstructed. Then, through the basic steps of prony transform, the seismic data are selected and the prony transform is carried out to verify the fitting of prony algorithm. Prony method can get the needed information quickly according to the measured data, and can fit the data very well in 1999. Mitrofanov studies the effectiveness of prony filtering based on model. These models indicate that in seismic data processing, prony filtering has considerable potential in order to obtain information about the structure of the medium and the potential zones of oil and gas. Through the steps of prony filtering and the setting of the best parameters, the absorption filtering is carried out on the seismic section, and the original seismic profile is compared with the filtering result. Prony absorption attenuation filtering technique can directly obtain the absorption coefficient of reservoir by nonlinear filtering of seismic signals by damping harmonics. At the same time, under the condition of multistage quality control, the prediction accuracy of prony absorption filter is higher than that of Fourier transform. After absorption filtering, the response of the profile is that the in-phase axis is weakened or disappeared compared with the input profile. According to the result of parameter selection, it is necessary to increase the information of well point to determine the best parameters of prony absorption filter. Seismic waves propagating in gas-bearing reservoirs have strong energy absorption response characteristics, but this phenomenon is difficult to find in the original seismic records. However, after absorbing and filtering, this phenomenon can be detected. This can facilitate us to better identify gas reservoirs.
【學位授予單位】：長江大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.4

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