非均匀介质中叠加剖面的横向分辨力估算

ESTIMATION OF LATERAL RESOLUTION FOR STACKED SECTION FROM INHOMOGENEOUS MEDIUMS

地质矿产部石油物探研究所

本文从地震勘探的实际条件出发,推导了连续介质中菲涅尔带半径公式,并按实际情况进行了必要的简化.文中分析了简化公与未简化公式的差别,进而将简化公式推广为一般非均匀介质中的菲涅尔带半径公式.在公式的推导过程中,波长λ的意义与N.S.Neidell和Sheriff所述的波长有所不同.前者为地表附近的波长,后二者为平均波长.按新公式算得的菲涅尔带半径比原公式所得结果小得多.根据实际资料都不见垂直入射这一事实,推导了非零入射角条件下非涅尔带半径公式.当取公式中的入射角为零时,公式退化为垂直入射的形式.这说明后者为前者的特例.随着入射角的增大,菲涅尔带也会增大.文章最后分析了未偏移的水平叠加剖面的横向分辨力问题.

Starting from the practice of seismic survey, the formula for extracting the radius of Fresnel zone in continuous medium was derived and simplified in accordance with the practical situation. Errors for both the simpfilied and unsimplified formulae were analyzed. The simplified formula was popularized to the inhomogeneous medium. In derivating the formula, the wavelength A is different in meaning from that defined by N.S.Neidell and Sheriff (See REFERENCE[2]). The former only represents the wavelength near surface and the later the average ones. The radius of the Fresnel zone from the new formula is much smaller than that from the original ones. Because of the real data does not obtain from normal incidence, hence, the radius formula of Fresnel zone for non-zero incidence angle was derived. If the incidenc angle becomes to zero, then, the formula will degenerate into the form of normal incidence ones. It shows clearly that the later is a particular case of the former. With the increasing of the incidence angle, the Fresnel zone will also be increasing. The lateral resolution of the unmigrated horizontal stack section was also examined in this paper.