Angle domain common image gathers (ADCIGs), commonly regarded as important prestacked gathers, provide the information required for velocity model construction and the phase and amplitude information needed for subsurface structures in oil/gas exploration. Based on the constant-density acoustic-wave equation assumption, the ADCIGs generated from reverse time migration ignore the fact that the subsurface density varies with location. Consequently, the amplitude versus angle (AVA) analysis extracted from these ADCIGs is not accurate. To partially solve this problem and to improve the accuracy of the AVA analysis, we developed amplitude-preserving ADCIGs suitable for density variations with the assumption of acoustic approximation. The Poynting vector approach, which is efficient and computationally inexpensive, was used to calculate the high-resolution wavefield propagation. The ADCIGs generated from the velocity and density perturbations match the theoretical AVA relationship better than ADCIGs with constant density. The extraction of the AVA analysis of the various combinations of the subsurface medium indicates that the density is non-negligible, especially when the density contrast is sharp. Numerical examples based on a layered model verify our conclusions.

中文翻译：

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用变密度声波方程提取角域公共图像道集

角域公共图像道集（ADCIGs）通常被认为是重要的叠前道集，它提供了速度模型构建所需的信息以及油气勘探中地下结构所需的相位和幅度信息。基于恒定密度声波方程假设，逆时偏移生成的 ADCIG 忽略了地下密度随位置变化的事实。因此，从这些 ADCIG 中提取的幅度与角度 (AVA) 分析并不准确。为了部分解决这个问题并提高 AVA 分析的准确性，我们在声学近似的假设下开发了适用于密度变化的保幅 ADCIG。Poynting 矢量方法，高效且计算成本低，用于计算高分辨率波场传播。由速度和密度扰动产生的 ADCIG 比具有恒定密度的 ADCIG 更符合理论 AVA 关系。对地下介质的各种组合的 AVA 分析的提取表明密度是不可忽略的，特别是当密度对比鲜明时。基于分层模型的数值例子验证了我们的结论。