TEM Data Processing Method Research Based On The Dipole And Large-fixed Loop Devices

When exploring with TEM in the wild, several common devices are used which are Coincident loop,Central loop,Dipole device and Large-fixed loop combination.In contrast,The advantages of Dipole device are obvious which are small influence of first field,flexibility and convenient,strong ability to detect and identify,suitability of shallow exploration.Large-fixed loop combination has some advantages,such as large transmitting magnetic moment,deep-depth exploration,large area of exploration,high abnormity resolution, economic application.The present TEM data processing software can only be used to process and explain data for Coincident loop and Central loop.On this basis,this paper studies characteristics of Dipole device and Large-fixed loop combination,analyses the transient electromagnetic response characteristics of Dipole device and Large-fixed loop combination,deduces their expressions of kernel function,finishes calculating for apparent resistivity and apparent depth of Dipole device and Large-fixed loop combination,improves functions of TEM data processing software.These can provide software platform for processing data measured of the two devices.The main research work is as follows:1.Analyse the TEM response characteristics of the Dipole device and Large fixed-loop combination under a uniform half-space model.2.According to the different response characteristics of the different devices in different periods,the wavelet threshold value and three-point index approaching de-noise method are improved.For dipole devices and outside of Large fixed-loop,the wavelet threshold method value de-noise can be used to filter.For inside of Large fixed-loop,the three-point index nonlinear smoothing filtering methods is chosen,which can increase the signal to noise ratio.3.Analyse the sampling methods of the two devices,the design uses a combining method of the uniform-intensive sampling and approximate logarithm-interval sampling . In later days , still use the approximate logarithm-interval sampling and the number of sampling interval is 1.2.While in the early times,narrow sampling interval for sampling interval of 1.1,or directly use the uniform sampling method,not lose the useful early datas.4.For the ramp step effect,use the analytical method to correct the descend edge.5.Detailed Analyse transient response of the Dipole device in uniform half-space model,the function expressions between the solution of kernal function and the apparent resistivity are given,study the characteristics of kernal function , divide their monotonous variational interval , use the sub-iteration search fitting method to determine the solution of kernal function,calculate the apparent resistivity.When the measured unitary value is beyond the scope of the function,the Dipole devices use the early or later approximate formula to calculate the apparent apparent resistivity.6.Deduce transient response formula and kernal function expression of Large fixed-loop combination under the uniform half-space model,analyse the relationship between the solution of the kernal function and apparent resistivity , analyse the character of the kernal function and give its monotonous changing ranges,use the sub-iteration search fitting method to determine the solution of kernal function , calculate the apparent resistivity.Without the similar formulas,when measurements within the loop occur,the apparent resistivity is caculated using early and late approximate formulas of the central loop;on the contrary,when measurements outside the loop occur , the apparent resistivity is caculated using early and late approximate formulations of the Dipole mode.7.Apply the "Smoke Ring" theory of Nabigian to caculate the apparent depth of Dipole device and Large fixed-loop combination.8.On the basis of the original TEM data-processing software,use C++Builder software to develope the data-processing functions of Dipole device and Large fixed-loop combination.9.Use the developed software to process the measured datas origined from Caijia of Changchun and Dagang Oilfield field of Tianjin.Compare with the known geological information, prove the rationality and Correctness of the principles and methods discussed by this paper.