Based on the sedimentologic theory and acoustic transit mechanism and by using logging data of wells drilled with oil-based and water-based mud

this paper systematically analyzes features and control factors of various acoustic impedances and actual wave impedances met in sandstone-mudstone section while logging.Logging acoustic impedances of fluvial strata are largely influenced by drilling mud.Under the condition of using water-base mud

alteration of argillaceous strata and borehole collapse can often lead to mismatch or pseudomorph in inversion of logging acoustic impedance.In contrast

stratigraphic actual wave impedance is mainly controlled by shale contents

and it reaches its maximum value when the shale contents is equal to the stratigraphic maximum effective porosity.Generally

values of wave impedance in argillaceous sandstone and sandy mudstone are relatively large

while that in mudstone is relatively small

and that in sandstone is situated between the two.