Method for calculating apparent conductivity of electromagnetic field of frequency domain electrical source

Abstract

The invention discloses a method for calculating the apparent conductivity of an electromagnetic field of a frequency domain electrical source. The method comprises the following steps: (1) arranginga power supply electrode and a transmitting power supply in a specified exploration area; (2) arranging an observation network, and selecting a frequency range and an observation fan-shaped area; recording I of current information transmitted by a transmitter, and observing a tangential component E<phi> or a normal component E<r> of a multi-frequency-point electromagnetic field at one time at a receiver end; (3) calculating the derivatives round(E<phi>) / round(f) and round(E<r>) / round(f) of the electric field tangential component E<phi> or normal component E<r> of the corresponding frequency point combination to the frequency f by adopting a second-order difference technology, and storing the calculated partial derivative information; and (4) calculating the apparent conductivity of a frequency domain electric dipole source by using the derivatives round(E<phi>) / round(f) and round(E<r>) / round(f). The method is suitable for observing the electrical distribution of an underground structure in the whole domain. Only electric field data in one direction needs to be measured, the field acquisition cost is low, the observation efficiency is high, and the requirement for observation equipment is low.

Description

technical field [0001] The invention relates to the frequency domain electromagnetic method apparent conductivity measurement method applied in the field of geophysics, in particular to the normal component E of the measurement observation point r and the tangential component To calculate the conductivity method, this method can effectively improve the accuracy of apparent conductivity calculation. Background technique [0002] In the application of geophysical frequency domain electromagnetic prospecting, apparent resistivity (the reciprocal of apparent conductivity) is an important parameter to evaluate the conductivity of underground rocks (ores). Usually, the apparent resistivity is related to factors such as rock (ore) composition, structure and measuring devices of the underground medium, and it is a comprehensive effect of underground rock (ore). For example, Controlled Source Audio-frequency Magnetotellurics (CSAMT) is an active frequency-domain electromagnetic pr...

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Problems solved by technology

[0003] At present, studies on the calculation of the apparent resistivity of the whole region have been carried out at home and abroad. Most of the definition methods of the apparent resistivity of the whole region use the measurement of the electric field x component E in the Cartesian coordinate system. x To calculate, this method can solve most of the measurement area, but based on the tangential component of the observation point in the cylindrical coordinate system The observation area range is much larger than E x weight

In addition, by the electric field E x or To define the apparent resistivity of the whole area, it is usually necessary to select an appropriate initial value and use iterative solution formulas for iterative approximation to calculate the apparent resistivity parameters. The selection of initial values ​​and iterative formulas often result in apparent resistivity (apparent conductivity) Inaccurate calculations lead to numerical errors and affect the efficiency and accuracy of later data interpretation

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