高分辨率感应测井仪器线圈系设计

A Design of Induction Logging Coil System for High Resolution

受感应测井条件所限,高电阻率地层对低电阻率地层电阻率的测量结果影响较小,而低电阻率地层对高电阻率地层电阻率的测量结果影响较大。提出了新的高分辨率感应测井仪器线圈系设计方法。线圈系包括主线圈、屏蔽线圈和聚焦线圈等3部分。主线圈、屏蔽线圈和聚焦线圈分别由多个单发单收线圈对组成,每个发射线圈和接收线圈都具有相同的线圈匝数。把每个接收线圈的接收信号按一定的权值进行叠加就可得到仪器的测量信号,应用仪器常数就可得到地层电阻率。其最大优点是每个线圈可得到所需要的任意匝数(也可是非整数匝数)。主线圈和屏蔽线圈的权值是固定的,而聚焦线圈的权值则是可变的。根据井眼大小调整聚焦线圈的权值,使井眼的影响降低到最小程度。

Suggested is a idea on design of induction logging coil system for high resolution: the coil system are composed of 9 sets of main coil,auxiliary coil and focusing coil,each set has its own transmitter-receiver coil pair,every transmitter coil or receiver coil has same turns,signals received by each receiver are superposed with certain weight to form the measurement signal,then formation resistivity will be got by calibration factor.The weight of main coil and auxiliary coil is fixed while the weight of the focusing coil can be adjusted according to borehole size to minimize borehole effect.The calculated results of vertical and radial geometric factor of each coil set are presented,the performance of the coil system are shown with simulated logging responses.