非均匀套管井中的过套管电阻率测井响应

Responses simulation of through-casing resistivity logging in heterogeneous-casing wells

套管井壁的电势分布包含了金属套管和地层模型的信息,套管电阻率的变化对过套管电阻率测井有重要影响,本文考虑了套管电阻率的变化对传输线方程系数的影响,给出了非均匀套管壁电势分布的计算方法.利用套管井壁电势分布实现了非均匀套管测井响应的计算,考察了套管电阻率变化对过套管电阻率测井响应的影响,模拟结果表明,套管的变薄或变厚对测井响应均有一定影响。当套管电阻突然变小(套管变厚)或突然变大(套管变薄)时过套管电阻率测井异常发生在套管电阻突变界面附近.模拟结果还显示电极距对测井结果有明显影响.

Because the potential distribution on the metal casing contains the information of metal casing and formations, the change of resistivity of metal casing has an important effect on through-casing resistivity logging responses. The effect due to the change of casing resistivity on the coefficients of transmission line equation（TLE） is considered, and the calculation method of potential distribution on the heterogeneous casing is also given. On the basis of the potential distributions obtained from TLE, through-casing resistivity logging responses of heterogeneous casing are calculated, and the effects of the change of metal casing resistivity on the resistivity logging response are analyzed. The computation results show that the casing change whether thinner or thicker has an obvious effect on the logging responses, and the abnormalily of logging response appears where the casing resistance suddenly decreases or increases. The computation results also show that the spacing of electrodes has an important effect on through-casing resistivity logging responses.