基于正交采样的随钻电阻率测量响应特性

LWD response characteristics based on orthogonal sampling

地层电阻率参数的精确测定是随钻电磁波电阻率测井仪器测量的关键,其测量的核心在于感应电磁波信号幅度比和相位差的计算。针对幅度比和相位差准确计算需求,采用正交采样方法,对相邻接收线圈处的感应电磁波信号进行预处理及正交采样,计算得到相邻接收线圈处感应电磁波信号的幅度比和相位差,并通过仿真实验分析线圈系结构穿过不同电阻率参数层状地层模型时相邻接收线圈处感应电磁波信号幅度比和相位差的响应特性,验证正交采样方法在幅度比和相位差准确计算方面的优势。结果表明:在感应电磁波信号数字采样时对每路信号进行多周期采样后取平均,提高了感应电磁波信号幅度比和相位差的计算精度;另外,通过正交采样方法对每路信号间隔T/4后进行采样,提高了计算速度。采用该方法能够满足随钻电磁波电阻率测井仪器对实时性的要求。

Accurate measurement of layer-earth resistivity parameters is a key task in the measurement of electromagnetic wave resistivity logging instruments while drilling. The kernel point of this measurement lies in calculation of the amplitude ratio and phase difference of the induced electromagnetic wave signal. According to the accuracy calculation requirements for the amplitude ratio and phase difference,we adopt an orthogonal sampling method,which preprocesses and orthogonally samples the induction electromagnetic wave signal adjacent to the receiver coil. The amplitude ratio and phase difference of the induction electromagnetic wave signal adjacent to the receiver coil were calculated. In the light of the simulation experiment,the response curves on the amplitude ratio and phase difference of the induction electromagnetic wave signal at the neighborhood receiver coils are analyzed,when the coil system structure passes through the layer-earth model with different resistivity parameters. The advantages of the quadrature sampling method in accurately calculating the amplitude ratio and phase difference of the electromagnetic wave signal were verified. The results demonstrate that each signal is averaged after multi-period sampling in the digital sampling of the induced electromagnetic wave signal,which improves the calculation accuracy of the amplitude ratio and the phase difference of the induced electromagnetic wave signal. In addition,by using the orthogonal sampling method,the calculation speed is improved after sampling each signal at T/4 intervals. This method can meet the real-time requirements of the electromagnetic wave resistivity logging instruments while drilling.