Abstract:Synthetic acoustic log is a widely-used method for converting seismic reflection datainto interval velocities.Only in the case of zero-phase all-pass wavelets,can the method offer good interval velocity variations.So far as the response of a single interface,lack of high-frequency contents results in poor clarity of interface,lack of low-frequency contents brings distorted velocities,and lack of both of them causes the above two phenornena.Concise diagram of interface response can show the response feature of singlebed synthetic acoustic log.Lack of high frequency contents only darnages the clarity ofthick bed,but influences both interval velocity and apparent thickness of thin bed.Lackof low-frequency contents brings little influence on very thin bed;and it causes higher velocity distortion for thicker bed,even terrible inverse velocity anomaly in formation.Lack of both low-frequency contents and high-frequency contents causes the influenceon thin bed which is similar to that resulting from lack of high-frequency,but brings the influence upon thick bed which is analogous to that caused by lack of low-frequency contents.The relative width of frequency band(the ratio of high-cut frequency to low-cut frequency)determines the upper limit of velocity accuracy.