基于Q补偿的黏弹介质逆时偏移成像研究

发布时间：2018-08-21 10:35

【摘要】：偏移成像是地震勘探中关键环节,逆时偏移成像技术能够适应复杂速度模型,成像结果更为精确,成为当前地震勘探研究热点之一。地震勘探中得到的地震记录常存在介质黏弹性导致的地震波衰减影响,受强烈衰减的记录中能够精细刻画深层地区的信息模糊不清,使得勘探分辨率降低,更接近实际介质假设的偏移方法越来越受到关注。黏弹性模型能够更准确表征实际地下介质地震波传播过程,考虑黏弹介质吸收衰减规律和波场传播特征的逆时偏移方法能够指导地震勘探资料处理解释,帮助解决油气勘探面临的复杂问题,以提高勘探精度。基于此论文开展了基于Q补偿的黏弹介质逆时偏移成像研究,在逆时偏移波场延拓过程中对黏弹介质的衰减影响进行处理,准确的补偿衰减和校正相位畸变效应,得到更高分辨率的偏移成像结果。主要研究内容和成果如下:1)论文从地震勘探频带内较为准确的常Q黏弹模型出发,推导了分数阶时间偏导黏弹介质波动方程,利用拉普拉斯算子将分数阶时间偏导转换至空间偏导,得到了伪谱法常Q模型黏弹介质拉普拉斯分数阶波场延拓算子,实现了伪谱法黏弹介质波动方程正演数值模拟。基于常Q模型的黏弹波动方程能够较好模拟地震波黏弹介质中传播相位延迟振幅减弱的衰减现象,受强烈黏弹性衰减影响的地震记录偏移时存在多分量波场混合和有效反射波受衰减信号较弱的问题。2)论文研究了弹性波逆时偏移成像方法以应对黏弹地震记录数据多分量波场混和问题。利用波场分离,得到了纵横波分离的弹性波逆时偏移成像结果。为压制逆时偏移过程中低频噪音,发展了一阶速度应力能量范数成像条件的弹性波逆时偏移方法,引入了中间应变分量,发展了一阶速度应力方程能量范数成像条件逆时偏移波场分量更新方式。基于能量范数的弹性波逆时偏移能够有效压制低频干扰得到较高分辨率弹性波逆时偏移结果。3)论文发展了补偿黏弹逆时偏移波场延拓算子构建思路,改造了相位与振幅衰减解耦的黏弹介质波动方程,重新构建了相位振幅变化类波场延拓算子。重构的相位校正类黏弹算子波场延拓过程能够独立校正相位不衰减振幅,振幅补偿类黏弹算子模拟波传播过程中能够独立补偿振幅不改变相位。相位延迟校正和振幅衰减补偿算子可以相互组合,构成了灵活变化黏弹波场延拓技术序列。4)论文给出了基于Q补偿黏弹逆时偏移框架,以解决黏弹地震记录偏移需要校正相位振幅的问题。发展了补偿的黏弹逆时偏移方法,提出了互相成像条件类和震源归一化类成像条件补偿黏弹逆时偏移策略。互相成像条件类选用相位衰减振幅波场黏弹算子,震源归一化类成像条件采用仅相位延迟和相位延迟振幅衰减黏弹算子,实现了补偿黏弹逆时偏移成像算法;发展了纵横波波场分离的补偿黏弹逆时偏移技术。补偿黏弹逆时偏移成像算法在正反传波场延拓中进行相位校正和振幅补偿,能够得到更高分辨率偏移结果。论文研究过程中主要创新之处为:1)发展了一阶速度应力方程能量范数成像条件弹性波逆时偏移方法。该方法能够有效压制弹性波逆时偏移过程中低频噪音,取得较好成像效果。2)构造了相位与振幅变化的黏弹波动方程波场延拓算子。构建的算子能够独立用于补偿黏弹逆时偏移正反传波场延拓中相位与振幅的解耦校正,解决了普通波场延拓算子难以进行黏弹波场中相位振幅校正补偿的问题。3)发展了基于Q补偿的黏弹介质波动方程逆时偏移方法。该方法同时考虑黏弹波场多分量复杂性和黏滞性衰减效应,在波场延拓过程中对地震波相位和振幅准确校正补偿,减小因黏弹介质衰减效应导致偏移结果不准确的影响,得到更高分辨率偏移结果。
[Abstract]:Migration imaging is a key link in seismic exploration. Reverse-time migration imaging technology can adapt to complex velocity model and its imaging results are more accurate. It has become one of the hot topics in seismic exploration. Viscoelastic model can more accurately characterize the seismic wave propagation process in actual underground media, and reverse-time migration method considering the absorption and attenuation law of viscoelastic media and wave field propagation characteristics can guide. Seismic exploration data processing and interpretation help to solve the complex problems faced by oil and gas exploration and improve exploration accuracy. Based on this paper, the inverse time migration imaging of viscoelastic media based on Q compensation is studied. The attenuation effect of viscoelastic media is processed in the process of inverse time migration wave field continuation, and the attenuation and phase distortion are corrected accurately. The main research contents and achievements are as follows: 1) Based on the more accurate constant Q viscoelastic model in seismic exploration frequency band, the wave equation of fractional order time-derivative viscoelastic medium is deduced, and the fractional order time-derivative is converted to spatial derivative by Laplace operator, and the pseudospectral constant Q is obtained. The forward numerical simulation of wave equation in viscoelastic media using pseudo-spectral method is realized by using Laplace fractional wave field continuation operator in the model.The viscoelastic wave equation based on constant Q model can simulate the attenuation of phase delay amplitude in seismic viscoelastic media and the migration of seismic records affected by strong viscoelastic attenuation. The problem of multi-component wavefield mixing and weak attenuated signal of effective reflection wave is existed. 2) The elastic wave inverse migration imaging method is studied to deal with the problem of multi-component wavefield mixing of viscoelastic seismic data. In low-frequency noise, an elastic wave inverse migration method based on first-order velocity-stress energy norm imaging condition is developed, and the intermediate strain component is introduced. A new method for updating the wave field components of first-order velocity-stress equation inverse migration based on energy norm imaging condition is developed. High-resolution elastic wave inverse migration results. 3) The idea of constructing wave field continuation operator for compensating viscoelastic inverse migration is developed in this paper. The wave equation of viscoelastic medium decoupled by phase and amplitude attenuation is modified, and the phase-amplitude variation wave-like field continuation operator is reconstructed. The reconstructed phase-corrected wave field continuation process of viscoelastic operator can be independent. The phase delay correction and amplitude attenuation compensation operators can be combined to form a flexible viscoelastic wave field continuation technique sequence. 4) A Q-compensated viscoelastic inverse time migration framework is proposed to solve the problem. Viscoelastic seismic migration requires correction of phase amplitude.A compensated viscoelastic inverse-time migration method is developed.A strategy of compensating viscoelastic inverse-time migration based on mutual imaging conditions and source normalization imaging conditions is proposed.The phase attenuation amplitude wave field viscoelastic operator is used for mutual imaging conditions and source normalization imaging conditions are used only. The phase delay and phase delay amplitude attenuation viscoelastic operator are used to compensate viscoelastic inverse time migration imaging algorithm, and the compensation viscoelastic inverse time migration technique for P-S wave field separation is developed. The main innovations in this paper are as follows: 1) An energy norm imaging conditional elastic wave inverse migration method for the first-order velocity-stress equation is developed, which can suppress the low-frequency noise effectively during the inverse migration of elastic wave and obtain better imaging effect. 2) The wave field continuation operator for the viscoelastic wave equation with phase and amplitude variations is constructed. The constructed operator can be used independently to compensate for the decoupling correction of phase and amplitude in forward and backward propagation wave field continuation of viscoelastic inverse time migration. The problem that ordinary wave field continuation operators are difficult to compensate for phase and amplitude in viscoelastic wave field is solved. The multi-component complexity and viscous attenuation effect of viscoelastic wave field can correct and compensate the phase and amplitude of seismic wave accurately in the process of wave field continuation, reduce the influence of inaccurate migration result caused by the attenuation effect of viscoelastic medium, and obtain higher resolution migration result.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P631.4

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