Abstract：The existing borehole-restricted inversion methods,such as SLIM,BCI,ROVIM and so on,usually consist of the following steps:·Synthetic seismogram is forward obtained by using convolution model after we repeatedly modify not only the wave impedance and thickness of formation but also wavelet,then it is taken to estimate its errors to a real seismic trace.·Make perturbation,in terms of these errors,to revise wave impedance mode1 until the errors reduce to minimum.However,the inversion of high-frequency informations is not correct because high-frequency seismic informations are usually unreliable. It is proved that highfrequency seismic informations outside effective frequency band will always result in multiple solutions,without any useful restriction. High-frequency informations can not be checked reasonably by convolution model.An easy logging-restricted inversion method is recommended here. Its principle involves the following essential points:·The wave impedance informations of mid-frequency seismic contents in effective seismic frequency band are obtained by using ordinary Seislog,Glog methodsand so forth.·The wave impedance informations of low and high-frequency seismic con-tents can be derived only from interpolation and extrapolation of logging data,andherewith the interprllation direction is controlled only by horizon informations of seismic data.Three wave impedance sections corresponding to low-,mid- and high-frequency seismic contents are combined to form the final inversion result.
