利用多次波数据提高成像精度方法研究

发布时间：2018-04-11 19:56

本文选题：OBS + 多次波　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：随着海上油气勘探的发展,过去的地震采集技术已经很难满足当下人们对油气开采的需求,OBS作为新的地震采集技术引起了广泛的关注。不论是在利用拖缆数据采集还是利用OBS地震数据采集方法,海上油气勘探中的多次波问题始终是地震数据处理的关键技术之一。经过研究发现多次波与一次波一样携带了大量的地下信息,尤其是在构造复杂地区,多次波数据却能够更好的成像。在OBS(海洋地震仪)勘探中,由于是将OBS置于海底,并且其每个OBS的间隔通常是大于200米的,在利用常规一次波进行偏移成像时,其海底浅层的成像受海底异常体影响大,成像效果很糟糕。然而,我们利用多次波进行成像时,不仅能够获得较为宽广的照明,对海底能够进行很好的成像,并且能够有利于浅层地区的成像,获得较好的偏移效果。尤其是在OBS数据缺失的时候,由于多次波旅行时较长,受海底异常体影响小,能够获得比一次波更加可靠连续的成像结果。因此,我们在水合物勘探或者是海底稳定性研究时,利用多次波成像的特点,可以为我们更好的完成地球物理调查任务。就利用多次波数据提高成像精度的方法研究而言,本次论文主要从OBS多分量数据的波场分离、射线追踪速度建模、逆时偏移三个方面入手来实现。首先介绍了OBS的勘探原理以及多次波的识别与衰减,然后介绍了逆时叠前深度偏移的原理及实现,最后利用射线追踪建立速度模型并实现了逆时偏移。在研究的过程中先探讨了的一次波与多次波在理论模型中逆时叠前深度偏移的结果,再对影响成像精度的因素进行了探讨,对比分析了一次波和多次波的成像结果,最后研究了由于OBS的位置和子波的频率或延迟等对多次波成像结果所造成的的影响。经过理论模型与实测数据的研究,我们发现其利用多次波数据确实能够提高海底浅层的成像,有利于我们水合物的勘探,且逆时偏移能够在大倾角处成像比单程波更具有优势。逆时偏移方法能够适应于OBS特殊的观测系统,它不需要保证炮点和检波点在同一基准面上,成像更具有灵活性。
[Abstract]:With the development of offshore oil and gas exploration, the past seismic acquisition technology has been difficult to meet the current demand for oil and gas production. As a new seismic acquisition technology, OBS has attracted wide attention.Whether using towed cable data acquisition or OBS seismic data acquisition method, the multiple wave problem in offshore oil and gas exploration is always one of the key techniques of seismic data processing.It is found that multiple waves carry a lot of underground information just like primary waves, especially in complex structures, but multiple data can be better imaged.In ocean seismograph exploration, because the OBS is placed on the seabed and the interval of each OBS is usually more than 200m, the imaging of the shallow layer of the seabed is greatly affected by the seabed anomaly when the conventional primary wave is used for migration imaging.The imaging is very poor.However, when we make use of multiple waves, we can not only obtain broad illumination, but also make good imaging of the seabed, which is beneficial to the imaging of shallow area and obtain better migration effect.Especially in the absence of OBS data, because of the long travel time of multiple waves and the small influence of seafloor anomaly, we can obtain more reliable and continuous imaging results than the first wave.Therefore, in hydrate exploration or submarine stability research, we can make use of the characteristics of multiple wave imaging to complete the geophysical survey for us.As far as the method of improving imaging accuracy is concerned, this paper mainly focuses on three aspects: wave field separation of OBS multi-component data, ray tracing velocity modeling and inverse time migration.This paper first introduces the exploration principle of OBS and the recognition and attenuation of multiple waves, then introduces the principle and realization of inverse time prestack depth migration. Finally, the velocity model is established by ray tracing and the inverse time migration is realized.In the course of the study, the results of the inversion prestack depth migration of the primary wave and the multiple wave in the theoretical model are discussed first, and then the factors affecting the imaging accuracy are discussed, and the imaging results of the primary wave and the multiple wave are compared and analyzed.Finally, the effects of the position of OBS and the frequency or delay of wavelet on the imaging results are studied.Through the study of theoretical model and measured data, we find that the multiple wave data can really improve the imaging of shallow seabed, which is beneficial to the exploration of hydrate, and the inverse time migration is more advantageous than the single-pass wave in imaging at large dip angle.The inverse time migration method can be adapted to the special observation system of OBS. It does not need to ensure that the shot point and the detection point are on the same datum level and the imaging is more flexible.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.46

【参考文献】