基于弹性波模拟的逆时偏移以及地震数据解释
发布时间：2018-07-24 11:56
【摘要】：地震偏移成像是一种优秀数据处理技术,它将地表接收到的地震记录投影到其源头从而构建地下结构图像。在现有的各种偏移成像技术中,由于其相对于其他传统偏移技术所的具有优异性能,逆时偏移(RTM)是被当今勘探工业界以及学术界所公认的标准成像技术。尽管逆时偏移计算量大所需计算时间长,但是它能有效地综合应对复杂地质情况、陡倾角反射面以及强横向速度扰动。逆时偏移将地表记录到的地震信号视作边界条件,然后将这些信号在时间上进行反传直至满足成像条件。这个方法可以使用与波场正演模拟相同的模拟算法。传统的地震波场外推理论假设地表是水平的,而在模拟地震波传播的时候必须考虑到不规则地表的影响,这并不总是一项简单的工作,但是我们能够通过我们的正演模拟算法正确地处理起伏地表的问题。这项工作采用了曲线网格有限差分方法(CG-FDM)来模拟起伏地表条件下的弹性地震波传播。其中,贴体网格的被用来避免人为散射同时使网格与自由地表相一致。我们使用高阶优化的同位网格DRP/opt MacCormack算法来求解一阶速度应力方程组,因为这种算法使得计算效率和计算精度达到最好的平衡。在解决了正演模拟问题后,通过在时间上对地表记录进行翻转并最终利用反转后的记录做逆时外推,进而完成波场的逆时外推。成像准则和成像条件是逆时偏移的核心,震源归一化的互相关成像条件被用来对下行以及上行波场在相对应时刻进行互相关。我们用过以Marmousi模型作为真实模型的合成数据实验来研究我们方法的优缺点,与此同时,其他的一些简单模型也被用于测试。我们用垂直方向有限差分图像处理技术来消除互相关结果中的低频噪音,这个方法对水平结构的成像是非常有用的,由它得到的消除低频噪音后的结果非常显著。我们重点关注弹性波传播而不是声波是因为地球本身表现出弹性体的特征。各种模型测试得到的逆时偏移结果令人满意,我们的偏移算法能完美应用于商业用途。另一方面,对位于巴基斯坦Punjab地台的Nandpur气田潜在反射层的实际地震数据的解释工作已经完成。出于这个目的,在巴基斯坦政府的官方批准下,Nandpur气田的实际数据被用来更加清晰实际地阐述地震数据解释。我们用地震和地球物理测井资料用来做结构解释并最终通过地球物理测井技术评估该区域碳氢化物存在的可能。结果表明,这片区域具有很大的油气开发前景。
[Abstract]:Seismic migration imaging is an excellent data processing technology, which projects the seismic records received from the surface to its source to construct the underground structure image. Among the existing migration imaging techniques, because of their excellent performance compared with other traditional migration techniques, inverse time migration (RTM) is a standard imaging technology recognized by the exploration industry and academia. Although the computation time of inverse time migration is long, it can effectively deal with complex geological conditions, steep dip reflection surface and strong lateral velocity disturbance. Inverse time migration regards seismic signals recorded on the surface as boundary conditions and then transmits them back in time until the imaging conditions are satisfied. This method can use the same simulation algorithm as the forward simulation of the wave field. The traditional extrapolation theory of seismic wave field assumes that the surface of the earth is horizontal, but the influence of irregular surface must be taken into account when simulating the propagation of seismic wave. This is not always a simple task. But we can deal with the problem of undulating surface correctly through our forward simulation algorithm. A curved grid finite difference method (CG-FDM) is used to simulate elastic seismic wave propagation under undulating surface conditions. Among them, the body-fitted grid is used to avoid artificial scattering and make the mesh consistent with the free surface. We use the high-order optimization DRP/opt MacCormack algorithm to solve the first-order velocity stress equations because the algorithm achieves the best balance between computational efficiency and accuracy. After solving the forward modeling problem, the inverse time extrapolation of the wave field is accomplished by flipping the surface record in time and finally making use of the inverted record to do inverse time extrapolation. Imaging criteria and imaging conditions are the core of inverse time migration. The normalized cross-correlation imaging conditions are used to cross-correlate the downlink and uplink wave fields at the corresponding time. We have used the Marmousi model as the real model to study the advantages and disadvantages of our method. At the same time, some other simple models have also been used for testing. We use the vertical finite-difference image processing technique to eliminate the low frequency noise in the cross-correlation result. This method is very useful for the imaging of horizontal structure, and the results obtained from the method are very significant after the elimination of low frequency noise. We focus on the propagation of elastic waves rather than sound waves because the Earth itself exhibits the characteristics of elastic bodies. The results of inverse time migration obtained by various model tests are satisfactory, and our migration algorithm can be used perfectly for commercial purposes. On the other hand, the interpretation of the actual seismic data of the potential reflectors of the Nandpur gas field at the Punjab platform in Pakistan has been completed. To this end, actual data from the Nandpur gas field, with the official approval of the Pakistani government, have been used to explain the seismic data more clearly and practically. We use seismic and geophysical logging data for structural interpretation and ultimately evaluate the possibility of the presence of hydrocarbons in the region through geophysical logging techniques. The results show that this area has great prospects for oil and gas development.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P631.4
本文编号：2141300
[Abstract]:Seismic migration imaging is an excellent data processing technology, which projects the seismic records received from the surface to its source to construct the underground structure image. Among the existing migration imaging techniques, because of their excellent performance compared with other traditional migration techniques, inverse time migration (RTM) is a standard imaging technology recognized by the exploration industry and academia. Although the computation time of inverse time migration is long, it can effectively deal with complex geological conditions, steep dip reflection surface and strong lateral velocity disturbance. Inverse time migration regards seismic signals recorded on the surface as boundary conditions and then transmits them back in time until the imaging conditions are satisfied. This method can use the same simulation algorithm as the forward simulation of the wave field. The traditional extrapolation theory of seismic wave field assumes that the surface of the earth is horizontal, but the influence of irregular surface must be taken into account when simulating the propagation of seismic wave. This is not always a simple task. But we can deal with the problem of undulating surface correctly through our forward simulation algorithm. A curved grid finite difference method (CG-FDM) is used to simulate elastic seismic wave propagation under undulating surface conditions. Among them, the body-fitted grid is used to avoid artificial scattering and make the mesh consistent with the free surface. We use the high-order optimization DRP/opt MacCormack algorithm to solve the first-order velocity stress equations because the algorithm achieves the best balance between computational efficiency and accuracy. After solving the forward modeling problem, the inverse time extrapolation of the wave field is accomplished by flipping the surface record in time and finally making use of the inverted record to do inverse time extrapolation. Imaging criteria and imaging conditions are the core of inverse time migration. The normalized cross-correlation imaging conditions are used to cross-correlate the downlink and uplink wave fields at the corresponding time. We have used the Marmousi model as the real model to study the advantages and disadvantages of our method. At the same time, some other simple models have also been used for testing. We use the vertical finite-difference image processing technique to eliminate the low frequency noise in the cross-correlation result. This method is very useful for the imaging of horizontal structure, and the results obtained from the method are very significant after the elimination of low frequency noise. We focus on the propagation of elastic waves rather than sound waves because the Earth itself exhibits the characteristics of elastic bodies. The results of inverse time migration obtained by various model tests are satisfactory, and our migration algorithm can be used perfectly for commercial purposes. On the other hand, the interpretation of the actual seismic data of the potential reflectors of the Nandpur gas field at the Punjab platform in Pakistan has been completed. To this end, actual data from the Nandpur gas field, with the official approval of the Pakistani government, have been used to explain the seismic data more clearly and practically. We use seismic and geophysical logging data for structural interpretation and ultimately evaluate the possibility of the presence of hydrocarbons in the region through geophysical logging techniques. The results show that this area has great prospects for oil and gas development.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P631.4
【参考文献】
相关期刊论文 前1条
1 王祥春;刘学伟;;起伏地表三维声波方程地震波场模拟(英文)[J];Applied Geophysics;2007年01期
，本文编号：2141300
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