层速度反演效果影响因素分析

AN ANALYSIS OF FACTORS AFFECTING THE EFFECT OF INTERVAL VELOCITY INVERSION

在利用VSP初至时求取层速度的方法中,广义线性反演方法是一种相对准确、可靠的方法。本文在介绍此方法后,对其具体实施作了简要说明,并用合成资料作了反演试算,效果令人满意。最后,文中分析了初至时误差、界面过井深度误差、倾角误差及假设地层水平对反演效果的影响。分析结果表明,在小井源距情况下,初至时误差是影响层速度反演精度的主要因素;在大井源距时,假设界面水平及倾角误差是影响精度的重要原因。

Among the methods of obtaining interval velocities from VSP direct traveltimes, ageneralized linear inversion method is relatively precise and credible. In this paper, themethod is introduced by illustrating briefly the realization of inversion with syntheticdata. The results of the inversion are satisfactory. The influence of traveltime errors, errors of interface crosshole, dip errors and supposed horizontal interface on the effect of inversion are analysed respectively. Apparently, among the above affecting factors, thetraveltime errors are dominative in case of a smaller offset and, in case of a greateroffset, the supposed horizontal interface and the dip errors will dramatically affect the accuracy of the reconstructed velocities. And finally, from this a significant conclusion isdrawn that raising accuracy of determination and estimation is important for improving theeffect of interval velocity inversion.