Induction conductivity measurement of surrounding low-conductive medium from copper tube — Experimental verification

Scaled Experimental Verification of Single-Well Induction Conductivity Measurement Through Nonmagnetic Casing

“…In a preliminary study [17], we showed that there were no detectable differences in the amplitude and phase of the receiver signal when the tank was empty and full of tap water, whereas in the case of the tank filled with the saline solution, the amplitude remained unchanged, but the phase changed. The conclusion that this change is due to the inductive coupling with the surrounding medium, and not due to the capacitive coupling, was corroborated by the insensitivity to the negligibly conductive tap water and by the good agreement of the experimental results with the theoretical predictions.…”

“…In other words, the casing acts as a low-pass filter for which the inverse of its transfer function can be calculated for known casing properties. From (16), it follows that B z,C+R = |k R ||k C |B z,air exp (j(arg k R + arg k C )) (17) where B z,air is real valued. If it is possible to calculate B z,C from the measured casing properties, then Δϕ(σ R ) = arg B z,C+R − arg B z,C = arg k R (18) which corresponds to (1).…”

“…This scaled experimental study is a necessary step before designing the full-scale prototype device. This paper contains a substantially extended presentation of the experimental results first published in [17]. This paper is organized as follows.…”

Instrument Design for Detecting the Inner Damage of Casing

“…In order to accurately measure the conductivity of the well fluid, it is necessary not only to calibrate the conductivity cell constant with an accurate KCl solution but also to place a detection electrode with an accurate size to ensure that the detection electrode is in complete contact with the solution to be measured, thereby obtaining an accurate conductivity value [33], [34]. However, in the actual logging process, because of the complex electrolyte composition in the well fluid, the problem of dynamic liquid level, and the interference of various electromagnetic noises in the well, it is impossible to quantitatively determine the values of conductivity cell constant and electrode constant [35]. What we are more concerned about is whether a significant change in conductance can be observed on the detection electrode when the damaged area of the casing inner coating changes, so as to determine the relationship between the two and solve the practical engineering needs.…”