基于prony变换的地震波吸收衰减特性提取方法研究

发布时间：2019-01-17 08:36

【摘要】：在近地表传播的地震波,由于地下岩层对地震波有吸收作用,使得它的高频能量发生衰减。地震波的衰减主要包含：地震波传播过程中的球面扩散效应,地层传输效应,岩石骨架的粘弹性性质,岩石的孔隙率,孔隙中的流体成分等。在这之中的前两项衰减与地震波的频率关系不大,后几项的吸收衰减与频率有很大关系,而prony变换可以描述频率同吸收衰减系数之间的关系。因此,它可以应用于检测吸收异常带。一直以来,研究储层的吸收作用,一般采用Fourier变换的方法,它通过线性滤波来间接的求取吸收系数,制约了预测的精度。而prony变换方法利用阻尼谐波对信号进行分解,通过非线性滤波直接求取吸收系数,同时拥有多级质控,提高了储层含气性预测的精度。本文首先介绍了地震波吸收衰减的各种机制,分别从宏观和微观上进行了列举。从宏观上看几何扩散、非弹性衰减、传输损耗、波型转换、散射以及折射角和临界角；从微观上看是摩擦作用、不可逆热传导作用、晶体不完整性、电化学影响、毛细管影响和液体流动作用。然后列举影响地震波衰减的各种因素,例如岩性、频率、压力、温度、应变振幅以及速度同孔隙流体饱和度。在地层吸收的基础上,探讨了地震波吸收衰减的参数如品质因子、吸收系数和对数衰减量以及衰减系数及其相互之间的关系。根据prony算法原理在matlab软件中编写prony变换的程序,实现prony变换的拟合,对信号的分析和重构。然后,通过prony变换的基本步骤,选取地震资料,进行prony变换,验证prony算法的拟合。Prony方法能根据测量数据很快求得所需的信息,并且能够很好地拟合数据。1999年,Mitrofanov基于模型研究了prony滤波的有效性。这些模型向我们预示了,在地震资料处理中,为获取有关介质结构和含油气远景区带的信息,prony滤波具有相当大的潜力。通过prony滤波的步骤以及最佳参数的设置,在地震剖面上进行吸收滤波处理,同时将原始的地震剖面图与滤波结果图进行对比,研究地层的含气性分析。prony吸收衰减滤波技术通过阻尼谐波对地震信号进行非线性滤波,能够直接获取储层的吸收系数。同时prony吸收滤波在多级质控的条件下,其对含气性的预测精度比Fourier变换技术要高。经吸收滤波后的剖面,其响应特征是与输入剖面相比同相轴弱化或者消失。根据参数选择的结果可知,有必要增加井点的信息来确定prony吸收滤波的最佳参数。在含气的储层中传播的地震波,会发生较强的能量吸收响应特征,但是这种现象在原始地震记录上很难被发现。然而,经过吸收滤波后,这种现象就能够被发现。这样能方便我们更好的识别含气储层。
[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.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.4

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