高频感应测井相位差与源距近似线性关系

Approximate linear relationship of phase difference and source-detector separation in high-frequency induced current logging

高频阵列感应测井仪器与普通声波时差测井仪器一样,均测量2个不同源距波形的相位差。通常情况下,由于相位在地层水平分界面上突变,所测量的相位差在界面上也有很大的变化,影响实际使用。在不考虑井眼影响的情况下,高频感应测井测量的相位差与源距存在近似线性关系,其斜率与地层电阻率成单值关系。为了去掉地层界面对相位差测量的影响,设计基于该斜率的阵列感应测井仪器,需要研究不同频率、不同地层电阻率条件下的相位差与源距的线性关系。在地层电阻率小于110Ω.m的范围内,给出了3个线性关系,线性关系所产生的误差均小于3%;如果相对误差小于3.5%,则可以用一个线性函数来描述源距与相位差的关系。

The high-frequency array induced current logging instrument is the same as the ordinary interval transit time logging instrument, which surveys the phase difference of two different source-detector separation profiles. Usually, because the phase has the sudden change in the stratum horizontal interface, the surveyed phase difference also has the very big change on the contact surface, which influences actual use. Ignoring the borehole effect, phase difference surveyed by high-frequency induced current logging and source-detector separation have the approximate linear relationship. Its slope and the formation resistivity are the monodromy relations. In order to remove the influence that the bed boundary produces for surveying phase difference, array induced current logging instrument, based on this slope,is designed. Linear relationship of phase and source-detector separation needs to be studied under the different frequency and different formation resistivity condition. In the scope of formation resistivity less than 110Ω·m, three linear relationships are given,and the errors that linear relationships produce is all smaller than 3%;If the relative error is smaller than 3.5 % ,then the relation of source-detector separation and phase difference may be described by a linear function.