Audio Frequency Electrical Penetration Data Inversion

Mine Audio-frequency electrical penetration is a direct-current electrical exploration method which measures electric field. This paper gives a modeling simulation inversion method of Audio-frequency electrical penetration in layered medium. Direct-current electrical exploration does traditional methods with measurement rock resistivity . Electric current through two grounding electrodes Provide to earth. And through another two grounding electrodes observation electric potential or potential difference information whith must use for Calculated rock resistivity. Form this theory proceed from. First make use of Ohm's law, again according to Ohm's law derived the whole space potential expression. This expression containing one A re-integration, make use of integration function property, this expression was discrete path integration, and choose higher accuracy methods the realization of the calculation, this methods is direct numerical integration.When programming to compute, there are two problems need to be solved. One is how to calculate undefined coefficient in potential expression, the other is how to calculate resistivity methods. For undefined coefficient, the relationship of undefined coefficient of each layer can be derived through boundary condition, then the undefined coefficient could be calculated by program; For resistivity algorithm, this paper uses matrix inversion calculated , and the result shows that this method has high precision.In the calculation of value is not obtained at the same time the value of resistivity is also different, even the earth will calculate the value of the resistivity of the impact of abnormal body on the ground floor of the existence of the resistivity of the influence of the calculated values are compared, so that the resistivity of the election calculated value of the smallest error.The modeling result of several kinds of layered medium shows that the Audio-frequency electrical penetration's results is mainly influenced by the border of medium. When the medium is uniform whole space, the direction of current line does not influenced by the medium, so when Point source and observation points exchange, potential curve patterns exactly the same. For layered medium, As a result of resistivity different, potential changes comparison obviously, in sub-interface current line direction change. Sub-interface from top to bottom resistivity different the greater the potential curve changes range. In addition, potential curve's max and min were related with ray pass through layered medium's distance length, is each generation unit's distance length. When Point source and observation points distance near, because of ray go through distance relatively small, potential value more; When Point source and observation points distance far, electric field in response to curve was influence with segment section in layered medium, and segment produce electric field have relations with underground media the distribution of. In layered medium, surface and border calculation accuracy relatively low, in regional subdivision the middle part of calculation accuracy high. When containing resistivity anomalous body in underground media, the results of calculated was influence with surface and border other than resistivity anomalous body.Several modeling result in this paper shows that the expression of point source and isomerism point source is correct. And the compute method is quick and precise.The analysis of result shows that Audio-frequency electrical penetration is fit for layered medium survey. It can reflect depth and resistivity of medium well, and can plot out stratum in borehole survey. But after all Audio-frequency electrical penetration is conductive electric prospecting method, when the thickness or the depth of medium is too large or the resistivity of overlay layer is too large, Audio-frequency electrical penetration can not get good result.