面炮叠前深度偏移与控制照明技术

基于波场延拓的叠前深度偏移是实现复杂构造地质体成像的最可靠方法,但存在着计算量大、对观测系统适应性差等缺点。面炮偏移是波动方程实现精确叠前成像的另一类方法,具有较高的计算效率,不存在偏移孔径问题,而且可以通过控制照明方法,解决平面波在目标区域的能量补偿问题。本文采用面炮成像技术进行叠前深度偏移成像,通过对面炮震源下行波场的质量控制以及射线参数的个数和范围的选取,以达到最佳的成像效果。采用不同深度点上的控制照明技术,较大地提高了目标地层的成像精度。数据实验表明面炮成像技术是一种快速有效的方法,其成像精度与单平方根算子的共炮点道集偏移和双平方根算子的共中心点道集偏移相当,但在计算速度上要快得多,而且易于并行计算。

Plane wave shot PSDM and controlled illumination techniques

The Pre-Stack Depth Migration (PSDM) method based on wavefield continuation is the most reliable method for imaging complex structure in the subsurface,although there are large computational costs and poorly adaptive geometry.Plane wave shot migration is another method to perform exact wave equation prestack imaging with high computational efficiency and without the migration aperture problem.Moreover,wavefield energy can be compensated at the target zone by controlled illumination.In this paper,plane wave shot PSDM was implemented by the control of the plane down-going wavefield and selection of number and range of the raypaths in order to optimize the imaging effect.In addition. controlled illumination techniques are applied to enhance the imaging precision of interesting areas at different depths.Numerical calculation indicates that plane wave shot imaging is a rapid and efficient method with less computational cost and easy parallel computation compared to the single-square-root operator imaging for common shot gathers and double- square-root operator imaging for common midpoint gathers.