A Direct Induced-Polarization Decoupling Scheme by Chop-Wave

Abstract

It is known that the electromagnetic coupling effect is a disturbance factor in induced‐polarization measurements. Based on the different appearances of EM coupling effect and IP effect in measured dual‐frequency waveform, a direct decoupling scheme by chop‐wave is presented in this paper. The method is able to eliminate EM coupling effect directly during the field data acquisition, and it does not suffer loss of IP information by and large. This paper has mainly discussed several aspects, which include the fundamentals of chop‐wave, the distortion of normal dual‐frequency wave resulting from chopping wave, chopper of existing pure EM coupling effect and IP effect's loss due to chop‐wave. The numerical results show that the scheme reduces and eliminates EM coupling effect markedly and can provide some parameter bases for the development and design on the correlative instrument. Thereby, it is worth generalizing the chop‐wave for decoupling scheme in the induced polarization method.

Research on 3D SIP Conjugate Gradient Inversion Algorithm with Parameter Range Constraints

“…G (i,j) herein represents the field generated by element j as the source at the center of element i or to say Green's coefficient of element j at element i. Assuming that the relative position of element i and j stay invariant, the value of G (i,j) should be the same like G (1,2) � G (2,3) ; thus, this matrix conforms to the structure of the Toeplitz Matrix.…”

“…QL approximation theory assumes that [11], in the anomaly region, the abnormal filed and setting field bear a linear relation. Plugged into equation (2), the approximate quasi-linear solution is worked out:…”

“…Convert the data of apparent resistivity and phase position from forward modeling above into electric field E X for inversion modeling. By subdividing the inversion region evenly in squares with the side length of 40 m in x × y × z � 20 × 12 × 10 � 2400 elements, the inversion modeling focuses on three aspects: (1) the feasibility of SIP inversion in intermediate gradient, (2) the impact of the selected initial model upon inversion result and the reason, and (3) the intermediate gradient QL inversion's resistance against the noise. Refer to Table 1 for the correlation of inversion result with the initial model and noise and Figure 3 for the inversion result under different initial models with each random noise level.…”

“…e previous SIP method overlooked the electromagnetic effect's impact or separated it in the approximation formula. For the past few years, the SIP forward and inversion method, taking the frequency domain Maxwell equation and Cole-Cole model as basis, or to say, taking both electromagnetic effect and IP effect into account, has deepened the research and understanding on the electromagnetic effect by leaps and bounds [2][3][4]. Nevertheless, difficulties still exist in both theoretical study and practical application, of which the electromagnetic effect and 3D inversion are of the greatest concern [5][6][7].…”

Choice of Electrode Material for Detecting Low Frequency Electric Field in Sea Water

“…Marine low-frequency and extremely low frequency electric field, whose field strength are weak, are produced by superposition of direct electric fields, alternating electric field and syntonic electric field [2].As disturbed by these electric fields, the DC resistance and AC impedance of electrodes change. Some researches show that [3], less resistance and impedance of electrode without disturbance can improve the measurement accuracy of detecting electrodes. In addition, different potential of electrodes is an important characteristic parameter of electrode, and little voltage difference can improve the accuracy of weak signal detection.…”