三维VSP资料波动方程叠前深度偏移研究

Wave equation of prestack depth migration of 3-D VSP data

中国石油化工股份有限公司石油勘探开发研究院南京石油物探研究所, 江苏 南京 210014

Institute of Geophysical Prospecting, SINOPEC Re- search Institute of Petroleum Exploration and Development, Nanjing 210014, China

已有的一些三维VSP资料处理方法,存在保幅性较差、对复杂构造不能正确归位、成像分辨率低、噪声强和计算效率低等问题,为此,提出了三维VSP资料波动方程叠前深度偏移成像方法,其实质是把地表数据的三维单程波动方程叠前深度偏移成像方法推广应用到三维VSP数据。对方法进行了阐述,其基本原理是将三维VSP数据按井中检波器的位置抽成共检波点道集,对共检波点道集进行三维叠前深度偏移。实现过程为将VSP波场分解为背景波场和扰动波场,背景波场采用相移法偏移,扰动波场采用频率空间域有限差分法偏移,然后对偏移后的上下波场进行相关处理,获得成像结果。数值模拟证明方法正确可行,实际应用表明方法实用。

The existing 3-D VSP data processing methods have several problems such as poor amplitude preservation, improper migration on complex structure, low imaging resolution, big noise, and low computational efficiency. So the wave equation of prestack depth migration imaging method is proposed. The essence of this method is to make the 3-D one-way wave equation of prestack depth migration imaging method of terrene data to be applied in the 3-D VSP data. Its basic principle is to draw the 3-D VSP data into a com-mon-geophone gather according to the position of geophones in wells and to realize the 3-D prestack depth migration of the com-mon-geophone gather. In this process, the VSP wave field is resolved into background wave field and disturbed wave field. Of the two wave fields, the background wave adopts phase shift method to migrate, and the disturbed wave utilizes frequency spatial domain finite difference approach to migrate. After migration, correlation processing is made for upper and down wave fields to obtain the final image. The numerical simulation proves that the method is correct and feasible and the actual application shows it is practicable.