论文详情
衰减旅行时层析作为一种估计Q值的方法,其衰减旅行时计算的准确程度影响最终Q值反演结果的精度。为了提高衰减旅行时层析求解精度而得到更真实的地下Q值分布,提出了一种改进的衰减旅行时层析方法,提高了模型中的衰减旅行时计算精度和实际资料中的衰减旅行时拾取精度。在射线追踪计算模型中的衰减旅行时的过程中,用方向速度梯度代替传统的速度梯度,考虑不同射线在不同传播方向上的速度差异,提高了射线追踪计算旅行时和反射角的精度,从而提高衰减旅行时计算精度。从实际资料中拾取衰减旅行时的时候,采用对数谱比反演方法,利用多道反射波信息同时反演多道衰减旅行时,从而避免了传统方法中人为选择最优频带带来的误差,使反演结果更稳定。在反演过程中考虑反射波在不同界面内的旅行时之差,可以有效解决上覆地层的影响。模型数据测试和实际资料应用结果表明,该方法Q值估算结果更加准确,Q补偿偏移后的剖面更加符合实际地下介质情况,验证了方法的可行性和有效性。
Attenuated traveltime tomography is an efficient method for Q estimation,and the calculation accuracy of attenuated traveltimes is essential.An improved attenuation traveltime tomography method is proposed.The proposed method improves the calculation accuracy of attenuated traveltimes for model data,and the picking accuracy of attenuated traveltimes for field data.Considering various properties of seismic rays in different directions,the method defines the direction gradient in ray-tracing instead of the conventional velocity gradient.The calculated reflection angles and ray paths are more accurate,thus more accurate Q results could be obtained.Log spectral ratio inversion is designed for field data attenuation traveltime calculation.Reflections of multi offset traces are used for attenuated traveltime estimations of multi offset traces simultaneously.This method could avoid artificial error by manually selecting optimistic frequency band,and so can derive more robust results.In addition,the method can avoid the effect from overburden by considering the traveltime difference between different layers.Synthetic and field data tests demonstrated that Q estimation using the proposed method is more accurate,and that the migration profile after Q compensation is more reliable,compared with the conventional method.