【作者】 王瑞敏；

【导师】 童思友； 刘怀山；

【作者基本信息】 中国海洋大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 南海海域是油气资源富集区,石油储量约有230-300×109t,天然气约338×1013m3,其中70%分布在深海区域,勘探前景非常广阔。尤其是近几年,随着陆上资源的日益枯竭,为扩大资源量,地震勘探由陆地、浅海逐步向深海发展,引发了一系列海域资源开采权的争夺。南海作为我国最大的边缘海,也是最具争议的海域,而对有争议海域油气资源开采,惯用规则是搁置争议、共同开发,这也就意味着海上油气资源的竞争就要靠先进技术来比拼,而与勘探为一体的深海地震资料处理技术的改进也就变得尤为重要。为此,选择南海地震资料多次波压制技术研究作为选题。本课题来源于国家南海专项《中深层地震多次波压制关键技术研究》。根据搜集到的南海地质资料,结合工区已有的钻井资料,建立了南海深海地质模型,应用声波方程有限差分法进行数值模拟。通过对模拟数据进行多次波速度谱分析、炮集多次波时距关系分析、海水速度叠加、共偏移距道集自相关分析等方法,系统地研究了南海多次波的特征。通过分析发现,南海海底全程多次波和层间多次波发育,尤其是海底全程多次波,周期较长,在近偏移距道处表现出明显的周期性,随着偏移距的增大,周期性逐渐变差。实际资料多次波也表现出与模型数据一致的多次波特征。在深海地震勘探中,近偏移距相对于海水深度来说可以趋近于零,地震波在海水中以很小入射角入射到海底以下地层,可近似看作垂直入射。因此,在近偏移距条件下,地震波的传播过程可以看作在海水中法向传播并入射到海底以下地层中传播。基于该思路推导了深海反射波时距曲线公式,该理论公式考虑在深海条件下海水深度对地震波传播的影响,使得近偏移距处求取的自激自收时间较目前常用的均方根公式更为精确。基于对深海多次波特征的分析,采用了多域压制多次波的技术流程。结合SRME技术特点和预测反褶积的优势,可以较好的压制深海近偏移距长周期多次波和短周期多次波。抛物线Radon变换滤波法根据有效波和多次波时差可以分离中远偏移距的多次波,但当远偏移距数据不满足双曲线特征时,将带来空间假频,能量泄露等问题。针对深海地震勘探排列较长的特点,将高阶动校正方法应用于大偏移距数据,得到较好的动校正结果,然后进行抛物线Radon变换,从而可以解决Radon变换压制大偏移距多次波效果差的问题,最终形成了一套适合南海深海地区的多域组合压制多次波的技术流程。将多域组合压制多次波的方法应用于琼东南盆地深海区正演地质模型数据和多条测线的地震资料数据的处理,取得了良好的效果。更多还原

【Abstract】 The South China Sea is rich in oil and gas resources with 230-300×109t oil and 338×1013m3 of gas, which has a very bright exploration prospects. In recent years, in order to expand the amount of resources, the seismic exploration was developing from the shallow to the deep-sea, which led to a series of disputation about the exploitation of marine resources. As the largest marginal sea, the South China Sea is the most controversial area. As for the exploitation of the disputed oil and gas resources, the regulation is shelving disputes and exploring together, which means that competition in the marine oil and gas resources depends on advanced technology. So it is important to improve the processing techniques.According to the deep-sea geological information and combining with the existing drilling information of the work area, the geological model was built. And applied the finite-difference numerical simulation of acoustic wave to simulate it. By analyzing the velocity spectrum of multiples and the time and distance relation of multiples of shot gathers, the sea velocity stacking and correlation analysis of trace gathers with the minimum offset, the features of multiple waves had been discussed. The whole multiples and interbed multiples developed in the seafloor, especially the whole multiples with a long period. It had an obvious periodicity and its periodicity was gradually weaker as offset increased. The feature of multiple waves of the actual data was similar with the model data.In the deep sea seismic exploration, near offset can be close to zero compared with the water depth, seismic waves can be approximated as normal incidence. Therefore, in the conditions of near offset, seismic wave propagation can be seen as the normal incidence in the, sea and spread into the seabed. Based on this thought, a theory formula of the seismic wave propagation was deduced. The theory considered the effect of the sea depth to the seismic wave propagation, which make the initial time of near offset department more precise than the commonly used RMS formula, and the shape of the curve is also closer to the actual wave propagation.Based on the analysis of deep-sea multiple characteristics, the multi-domain suppression technique was applied. Combined with the advantage of SRME and predictive deconvolution, the long-period and shot period multiples of near offset in the deep sea can be effectively suppressed. The parabolic Radon transform filter method can separate the multiples with the middle and far offset. When the far offset data isn’t satisfied the hyperbola characteristics, there will be spatial aliasing and energy leak. According to the character that the seismic exploration array of the deep sea is longer, applying the high order NMO to the far offset data to obtain the better NMO result, which can resolve the problem that the effect is bad using Radon transform to suppress the long offset multiples. The thesis selected the method matched the actual data according to the deep sea seismic wave propagation characteristics and the problem that the various multiples developed which made the suppression effect using the single method was not perfect, by making best use of advantages and bypass the disadvantages, optimizing combination and iteration of many techniques to suppress the multiples reasonably and form the multiple suppression workflow suitable with the deep sea area of the South China sea.The combined method was applied to process the forward geological model data and the seismic data of many measure lines of Qiongdongnan basin, which had achieved good effect.更多还原