基于菲涅尔高斯束正演的观测系统优化方法及应用

Optimization method of geometry and application based on Fresnel Gaussian beam forward modeling

基于正演模拟的观测系统优化是提高地震采集资料品质和降低采集成本的重要手段.在常规高斯射线束正演模拟理论的基础上,提出了基于菲涅尔带约束的高斯射线束(菲涅尔高斯束)正演模拟理论,相对于常规高斯射线束正演,菲涅尔高斯束在传播路径上由第一菲涅尔带约束,具有较小的有效半宽度,使得中心射线附近波场的走时和振幅计算更加准确.在中心射线终点处,提取目的层面元接收能量,建立能量均方差和平均能量分析函数,定量化分析评价不同观测系统下各目的层能量分布情况,预测后期偏移成像效果.基于目的层接收能量优化炮点加密方案,进而实现面向复杂地质目标的观测系统优化设计.该方法在胜利探区G94北区块应用,有效弥补了陡坡带上照明阴影区能量,改善了采集资料偏移成像效果.

The optimization design of geometry based on forward modeling is an important means to improve the quality of field data acquisition and reduce acquisition costs.Based on the conventional Gaussian beam forward simulation theory,the Fresnel band constrained Gaussian beam(Fresnel beam)forward simulation theory is proposed.Compared with the conventional Gaussian beam,the Fresnel Gaussian beam is constrained by the first Fresnel band on its propagation path and has a smaller effective half width,making the travel time and amplitude calculation of the wave field near the central ray more accurate,thus improving the accuracy of forward simulation.At the endpoint of the central ray,extract the received energy of the target layer,establish the energy mean square error and average power analysis functions,quantitatively analyze and evaluate the energy distribution of the target layers under different geometry,predict the later migration imaging effect,and optimize the shot points encryption scheme based on the received energy of the target layer,thus realizing the optimal design of the geometry for complex geological targets.This method has been applied in the G94 northern block of Shengli exploration area,effectively compensating for the energy of illumination shadow areas on steep slope zones and improving the migration imaging effect of data acquisition.