摘要:
布莱克海域天然气水合物储量丰富,ODP164航次采集的地震资料中明显表现出丰富的BSR特征。结合测井提供的纵横波速度、密度等信息和地震角道集叠加数据开展叠前弹性波阻抗反演,对水合物藏准确识别取得显著效果。研究发现,反演效果的好坏与角道集的质量密切相关,因为,该海域地震资料是变道距采集,覆盖次数不均匀,不同角度的角度体质量差别大,为了给后续精细的叠前弹性波阻抗反演提供高质量的角度叠加数据,开展改善角道集质量的处理十分必要。研究采用高精度抛物线拉东变换和面元优化处理等技术,很好地补充了偏移距信息的缺失,角度信息更加均匀,提取的角道集振幅能量和同相轴连续性得到提高。正演模拟资料证明了该方法的保真性和可靠性。从实际资料叠前弹性波阻抗反演的敏感属性对比中也可以清楚看到,经过角道集优化处理后的反演剖面在反映水合物层丰度变化和BSR特征上有很大改善。该技术对其他海域类似采集方式得到的地震资料角度道集质量的提高有很好的借鉴意义。
Abstract:
The Blake Ocean is rich in marine gas hydrate. The seismic data from Leg ODP164 clearly shows an excellent indication of BSR.Combining the p-wave velocity, s-wave velocity, density information from well logging and seismic angle gathers stack data to do the pre-stack elastic wave impedance inversion, we achieved a significantly effective and accurate results for recognition of the gas hydrate zone. However, we found that the inversion is closely related to the quality of angle gathers. Because the acquisition in this area uses a changing-trace interval, making the fold uneven, the quality of angle data of different angle has a big difference. In order to provide high quality angle stack data for pre-stack elastic wave impedance inversion, it's necessary to carry out the process to improve the quality of the angle gathers. In this study, we adopt precise parabolic Radon transform and binning optimizing processing, better supplementing the information of the loss offsets. As the result, the angle information becomes more balanced, the energy of amplitude of angle gathers and the event's continuity are both improved. Moreover, the conclusion of forward modeling proves that the Radon transform will not cause significant change to the original channel data. According to the comparison of sensitive attribute, which is calculated from pre-stack elastic impedance inversion, we can see clearly that the inversion profile obtained from the optimized gathers has greatly improved the hydrate layer's abundance changes and the BSR characteristics. This method also gives a good reference to process similar seismic data before the pre-stack elastic impedance inversion.
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