Distribution Of Useful Information In Transient Electromagnetic Logging And Experimental Study On Ultrasonic Detection Of Wall Leakage

In this paper,the useful information distribution and leakage ultrasonic experiment of transient electromagnetic logging are studied based on real axis integration method.Transient electromagnetic original logging waveform records the transient response of transmitting coil conduction,turn-off,reverse wizard and reverse turn-off between400 ms.The response at each time will reflect the characteristics of the casing,the cement ring and the formation,respectively.In this paper,the response waveforms of electrical conductivity,cement ring conductivity,casing conductivity and magnetic permeability in different strata are calculated by real axis integral method.The change of casing conductivity(and permeability)has a great influence on the shape of response waveform.After subtracting the response waveform of different casing conductivity,positive and negative peaks and extreme values appear.After subtracting the measured waveform,the peak value and the response at zero point were drawn into a curve.It was found that the curve at the peak time had a large amplitude at the collar,and the response at the peak value mainly reflected the characteristics of the casing.The response amplitude at zero point is very small,the collar is hardly shown,and the response at this point is independent of the casing.Similarly,after subsuming the waveforms obtained by different formation conductivity,there is also a peak value and a zero value.The curve formed by taking the peak position changes obviously with the depth,which is consistent with the conductivity curve measured by the open hole well,while the curve formed by the response near the zero point has nothing to do with the formation conductivity.The peak values caused by the casing and the formation are very close,overlap,and interact.Therefore,the formation conductivity curve obtained from the response at the peak of the response difference when the formation conductivity changes needs to be corrected for casing effect.In this paper,piezoelectric tube is used as the acoustic wave receiving probe to establish the eight-channel acoustic acquisition system.The acoustic wave experiment is carried out on the wall leakage model and the frequency curve of time difference is obtained by phase-shift.Distinguished by detecting the abnormal position of sound velocity,thus providing an experimental device and a specific implementation method for detecting the surface and wall leakage by measuring the sound velocity with the acoustic probe.The wave impedance of the water-resisting curtain is quite different from the soil layer.When the vibration is excited in the observation well near the waterresisting curtain,the acoustic surface wave on the surface of the water-resisting curtain will propagate along the surface,and its amplitude is large,and reflected wave will be generated in the leakage position.At the same time,the transmitting and receiving probes were moved to measure the full wave shape at different depths.In the vicinity of the leakage position,the acoustic surface and its reflected wave at the leakage position can be seen in the follow-up waves of the full wave shape.The ultrasonic attenuation coefficient of sand body was measured.Measurements were made near the water-resisting curtain with an ultrasonic instrument.Measurements were made in the borehole of the one-piece wall.The actual ultrasonic wave form of foundation pit waterresisting curtain is given.Through the phase method,the velocity of sound is obtained,which is of some significance to judge the leakage of water curtain,and can be integrated with the dc electrode method to judge the location of leakage,and improve the accuracy of judging the leakage of water curtain.