金属套管对电磁测井响应的影响

Influence of metal casing on electromagnetic logging response

石油大学,东营 257062

University of Petroleum, Dongying 257062

根据线圈系半径和金属套管半径之间的关系, 分3种情况讨论了均质地层和非均质地层中金属套管对电磁测井响应的影响, 给出了在均质地层中扣除套管影响的图版。在非均质地层中, 当发射线圈和接收线圈均在套管内时, 不能由含套管测井信号得到不含套管地层信号。当发射线圈在套管外而接收线圈在套管内时, 对于低电导率对比的非均质地层, 可根据含套管测井信号得到不含套管地层信号, 从而将套管的影响消除；当地层电导率对比度大时, 上述结论只适用于低频情况。当发射线圈和接收线圈均在套管外时, 在频率100～10kHz之间, 可以由合套管非均质地层信号得到不含套管地层的信号, 套管的影响能够消除。

The influence of metal casing on electromagnetic logging response in homogeneous and inhomogeneous formation is discussed according to three kinds of relation between the radii of coils and theradius of casing. The charts of subtracting the casing influence for homogenans formation are given. Ininhomogeneous formation, if both the transmitter and receiver lay inside the casing, the stratal signalswithout casing influence can not be obtained from the logging signals. If the transmitter lays outside thecasing and the receiver lays inside the casing, the stratal signals without casing influence can be obtainedfrom the logging signals for inhomogenaus formation of low conductivity contrast. Consequently the casing influence can be removed. For high-conductivity-contrast inhomogeneous formation, the above resultapplies only to low frequency circumstance. If both the transmitter and receiver lay outside the casing,for the frequency range of 100 Hz～10 kHz, the stratal signals without casing influence can be obtainedfrom the logging signals and the casing influence can be removed.