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    基于梯度约束的全方位逆时偏移成像技术研究及应用

    Research and application of gradient-constrained full-azimuth reverse time migration technique

    • 摘要: 随着 "两宽一高" 采集技术规模化应用,地震数据蕴含的介质信息愈发丰富,常规成像算法已难以满足宽方位地震数据的高精度成像需求。为此,提出了一种基于梯度约束的全方位逆时偏移成像技术,实现地下有效信息的充分利用与复杂构造的精确成像。该技术首先通过引入波场空间梯度与时间梯度构建约束方程,利用能量目标泛函最小化迭代求解波场传播矢量,有效解决常规波前矢量方法的局部计算不稳定与不准确问题;进而利用局部传播角度几何关系准确提取地下方位角与反射角信息;最终依据角度信息归约成像值,实现全方位角度道集映射。模型和实际资料测试表明,该方法能够充分利用波场传播角度信息,输出高质量成像剖面和全方位角度道集,为偏移速度分析和油藏描述等工作提供有力支撑。

       

      Abstract: With the large-scale application of "wide azimuth, wide frequency band, and high density" acquisition technology, seismic data now contain increasingly rich subsurface media information, making it difficult for conventional imaging algorithms to meet the requirements of high-precision imaging from wide-azimuth seismic data. To address this challenge, this study proposes a gradient-constrained full-azimuth reverse time migration (RTM) imaging technique that enables efficient utilization of subsurface effective information and precise imaging of complex structures. First, the technique constructs constraint equations by incorporating spatial and temporal gradients of the wavefield, solving for the wavefield propagation vector through iterative minimization of an energy objective functional. This effectively addresses the issues of local computational instability and inaccuracy inherent in conventional wavefront vector methods. Subsequently, it accurately extracts subsurface azimuth and reflection angle information using local propagation angle geometry. Finally, imaging values are normalized based on these angle parameters to achieve mapping of full-azimuth angle gathers. Theoretical model tests and real data applications show that the proposed technique can fully utilize the propagation angle information of the wavefield to produce high-precision imaging profiles and high-quality full-azimuth angle gathers, thereby providing strong support for tasks such as migration velocity analysis and reservoir description.

       

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