Abstract：Nowaday commercial seismic inversion softwares only offer users the log velocity curves for depth-time conversion after horizon calibration，without the raw log velocity curves after depth-time conversion. Such practice is feasible only in Glog softwares in which requirements for horizon calibration are not strict. F-lowever，in new wide-band restriction inversion，horizon calibration quality results in success or failure of this inversion because different horizon calibrations bring different wavelets. Thus,forward-inversive horizon calibration technique is advanced to cope with the problem. The new technique consists of the following steps:Derive synthetic seismogram from log velocity，density and reflection coeffident.Compare the synthetic seismogram with borehole-side seismic trace so as to get the revised reflection coefficients for better synthetic seismogram until the new synthetic seismogra- desirably coincides with the borehole-side seismic trace.lifter forward horizon calibration，inversions of synthetic seismograms which were derived respectively from drifted and non-drifted acoustic log curves are conducted to obtain drifted log velocity curve and raw log velocity curve.The drifted and raw log velocity curves are compared each other to revise reflection coefficient series until the drifted log velocity curve coincides desirably with raw log velocity curve.This technique produces satisfactory horizon calibration result and inversion effect. In our 3-D wide-band restriction inversion，wavelet interpolations in P-wave and S-wave sections are done to make multi-borehole 3-D seismic inversion very satisfactory.
