多次波分阶模拟及最小二乘偏移成像

Multiples simulation by orders and least-square migration

地震正演模拟是地震数据反演及成像中极其重要的部分。基于波动方程的有限差分法是目前应用最广泛的正演模拟方法,该方法虽然精度高,但不能模拟某一特定成分的波场,缺乏灵活性。基于频率空间域单程传播算符的波场模拟方法(波场分阶模拟算符)不同于有限差分法,该方法可以分别模拟一次波与多次波(包含表面多次波和层间多次波)。在常规地震处理中,多次波往往被视为干扰信息,但多次波中包含着丰富且重要的地下结构信息,利用好这些信息将极大地提高地下结构的成像质量。通过分析多次波在常规偏移成像中的影响,利用波场分阶模拟得到一阶表面多次波以及一次波,并进行表面多次波最小二乘偏移成像研究,提高一次波的成像效果,压制表面多次波成像中的串扰,提高地下结构的成像质量。

Seismic forward modeling is an extremely important part of seismic data inversion and imaging. At present, the finite difference method based on wave equation is most widely used for modeling. Although the method has high precision, it cannot simulate the wave field of a certain component, thus lacking in flexibility. This paper puts forward a wave field simulation method based on the one-way propagation operator in the frequency-space domain (i.e., wave field by-order simulation operator), which is different from the finite difference method, and able to simultaneously simulate the primary wave and multiples (containing surface multiples and interlayer multiples). In the conventional seismic processing, multiples are often regarded as interference information and contain rich and important underground structure information, which can be used to greatly improve the image quality of underground structure. Through analyzing the influences of multiples on conventional migration imaging, the wave field by-order simulation is applied to obtain the first-order surface multiple and primary wave. Meanwhile, the least-square migration imaging research is conducted on surface multiples to improve the imaging effect of primary wave, suppress the crosstalk in surface multiple imaging and greatly upgrade the imaging quality of the underground structure.