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当井孔为钢套管井时,井间电磁层析成象的应用范围将受到限制。钢套管具有的导电率比井眼周围地层的导电率大8个数量级。因此,用套管内的天线无法发射或接收测定井间地层导电率时所需的高频信号。在套管内加入小的绝缘间隙,以便信号能产生并进入套管,使其成为电偶极子天线,这样即可解决以上问题。有间隙的套管可按短孔和开口孔方式制做。在短孔中,电压加载在震源孔中,在其余的短孔中测
When the wellbore is a steel cased hole, the application of cross-well electromagnetic tomography will be limited. The electrical conductivity of steel casing is eight orders of magnitude greater than the conductivity of the formation surrounding the borehole. Therefore, the antenna inside the bushing can not transmit or receive the high-frequency signals needed to measure the conductivity of the formation between wells. Add a small insulating gap in the ferrule so that the signal can be generated and entered into the ferrule, making it an electric dipole antenna, thus solving the above problems. Gap with a short hole and hole can be made by way of opening. In short holes, the voltage is loaded in the source hole and measured in the remaining short holes