基于套管井中电磁测井响应的研究

Research on the electromagnetic logging responses in the cased hole

在套管井中通过测量电磁响应的方法获取套管外的地层信息时,套管对地层信号有很大的影响。为了得到更趋近于实际的测井数据,研究套管对电磁测井响应的影响规律具有非常重要的意义。文章以麦克斯韦电磁场理论为基础,建立了井眼、套管、地层三层柱状介质模型,推导了井中电磁响应的理论公式,分析了套管井中电磁测井对地层电阻率变化的灵敏度,以及套管参数对电磁测井响应的影响。数值计算结果表明,电磁响应对于电阻率较低的地层比较灵敏,套管参数对井中电磁测井响应的影响有一定的规律。

Based on the Maxwell's electromagnetic field theory,this paper derives the theoretical formula for the electromagnetic logging in the casing borehole of multi-cylindrical-layer model about borehole,the casing and the formation. The effects of the casing measurements and the sensitivity of the electromagnetic response to the formation resistivity were analyzed. At low frequency band,most of the magnetic lines can pass through the casing and electromagnetic responses are more sensitive to the low resistivity layers. Numerical simulation results show that the amplitude of the formation actuated signal decreased with the increase of the casing wall thickness. The numerical results of different permeability of the casing show that we can reduce the shielding effect by the method of decrease the permeability of the casing.