【摘要】 常规VSP偏移距校正方法是基于地下介质各向同性的前提下,利用井口、激发点、观测深度三者位置之间的距离关系,校正偏移距引起的纵向时间偏差,这种方法随着各向异性加剧和观测深度的减小而校正时间误差增大,不能满足用户对VSP资料的精度要求。研发了一种新的偏移距校正方法,它是以反射波双程旅行时水平同向程度作为目标,求出常规校正前、后时差随深度变化曲线,取这条时差曲线的中值对VSP时深关系中的时间作校正,实际应用表明,这种方法可提高时深关系的精度,可减小超过50%的时间误差。此外,地质层位标定与时差随深度变化曲线联合使用,通过确定临界时差和临界深度,可定量确定受偏移距影响井段,更合理地使用VSP资料,以提高地震勘探的精度。更多还原

【Abstract】 Conventional VSP offset correction is a method based on the premise of underground medium isotropic homogeneity,using distance relationship among wellhead,shot point and observation depth location to correct longitudinal time deviation caused by offset. With increase of anisotropy and decrease of observation depth,the corrected time error given by this method may increase and can not meet the requirement of the user on the VSP data accuracy. In this paper,a new offset correction method with the goal of horizontal homogeneous degree of reflection two-way travel time is presented,using the mid-value of travel time-depth curve before and after conventional correction to correct the time of VSP time-depth relationship. The case study shows that this method can improve the accuracy of the time depth relationship,with error reduced more than 50% of the time. In addition,the geologic horizon calibration combined with time-depth curve can be used to quantitatively determine the intervals affected by the offset through determination of the critical travel time and critical depth,thus realizing more reasonable use of VSP data.更多还原