Abstract：It is difficult to determine the first-break timing(or initial point) of P-wave or S-wave when using transmitting method for measuring sonic velocity of core or solid.The impact of errors on mea-sured results is bigger when sonic frequency is lower.The paper uses phase analysis to study theproblem of selecting the initial point.First,usinggood isotropic and homogeneous white marble forfabricating standard parts and measuring the sonicwaveform from different propagation distance,then the propagation velocity can be got by using phasecompensation method;second,using the propagation velocity, the first-break timing and the corresponding time-delay constant of measurement sys-tem can be determined from measured waveform atdifferent distance;finally, the other position ofwaveform can be determined as time-delay constantcorresponding to first-break timing;therefore, weselect optimum first-break timing according tocharacters of practically measured waveform andget more precise sonic velocity by using corresponding time-delay constant.The model test showed that different positionof first-break timing may get different time-delay constant of measurement system,in other words,the time-delay constant of measurement system iscorresponding to selection of first-break timing.
沈建国. 用穿透法测量声速时初始点的选择问题[J]. 石油地球物理勘探, 2003, 38(1): 44-47.
Shen Jianguo. Selection of first-break timing in using transmitting method for measuring sonic velocity. OGP, 2003, 38(1): 44-47.
