Virtual electrode current injection using seismic focusing and seismoelectric conversion

doi:10.1111/j.1365-246x.2012.05700.x

Cited by 11 publications

(1 citation statement)

References 27 publications

(39 reference statements)

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“…Sava and Revil (2012) simulate the electric field caused by the seismic wave using this method. The electromagnetic field is quasistatic because the wavelength of the electromagnetic wave is much larger than the source-to-receiver distances and borehole radius.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Simulation of the borehole quasistatic electric field excited by the acoustic wave during logging while drilling due to electrokinetic effect

Zheng

Guan

et al. 2015

GEOPHYSICS

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Acoustic logging while drilling (LWD) is an important commercial technology for oil and gas exploration. However, the collar wave in the full waveform has been found to interfere with signals from the formation, making it difficult to obtain formation compressional and shear velocities from acoustic LWD signals. We investigated seismoelectric LWD to solve this problem. We focused on the feasibility of obtaining the formation acoustic compressional and shear velocities from electric signals that go with acoustic waves near the borehole due to the electrokinetic effect. The theoretical full waveform of the seismoelectric LWD was simulated by one-way conversion approximation. The full waveform of acoustic pressure was simulated first, with a viscoelastic formation medium. The pore pressure was then estimated by confining pressure. The electric field excited by the elastic wave was seen as quasistatic and was simulated by solving the Poisson equation under the borehole conditions with an inhomogeneous term generated by the acoustic disturbance. In the full waveform of the synthesized electric field, there was a signal traveling with the collar wave speed, as well as signals accompanying compressional, shear, and similar guided wave groups. The converted electric collar wave signal was weaker than its acoustic counterpart, in terms of their amplitudes relative to other wave groups in their respective full waveforms.

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Section: Mathematical Formulationmentioning

confidence: 99%

Simulation of the borehole quasistatic electric field excited by the acoustic wave during logging while drilling due to electrokinetic effect

Zheng

Guan

et al. 2015

GEOPHYSICS

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Seismo‐electromagnetic thin‐bed responses: Natural signal enhancements?

Grobbe

Slob

2016

JGR Solid Earth

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We study if nature can help us overcome the very low signal‐to‐noise ratio of seismo‐electromagnetic converted fields by investigating the effects of thin‐bed geological structures on the seismo‐electromagnetic signal. To investigate the effects of bed thinning on the seismo‐electromagnetic interference patterns, we numerically simulate seismo‐electromagnetic wave propagation through horizontally layered media with different amounts and thicknesses of thin beds. We distinguish two limits of bed thickness. Below the upper limit, the package of thin beds starts acting like an “effective” medium. Below the lower limit, further thinning does not affect the seismo‐electromagnetic interface response signal strength anymore. We demonstrate seismo‐electromagnetic sensitivity to changes in medium parameters on a spatial scale much smaller than the seismic resolution. Increasing amounts of thin beds can cause the interface response signal strength to increase or decrease. Whether constructive or destructive interference occurs seems to be dependent on the seismo‐electromagnetic coupling coefficient contrasts. When the combined result of the contrast, between upper half‐space and package of thin beds and the internal thin‐bed contrast, is positive, constructive interference occurs. Destructive interference occurs when the combined contrast is negative. Maximum amplitude tuning occurs for thicknesses of thin‐bed packages similar to the dominant pressure and shear wavelengths. Artifacts due to model periodicity are excluded by comparing periodic media with random models. By simulating moving oil/water contacts during production, where the oil layer is gradually being thinned, seismo‐electromagnetic signals are proven very sensitive to oil/water contacts. An oil layer with a thickness of <1% of the dominant shear wavelength is still recognized.

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Comparison of full and quasi‐static seismoelectric analytically based modeling

Gao

Huang

2017

JGR Solid Earth

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Quasi‐static electromagnetic (EM) approximation was frequently used in numerical modeling of the seismoelectric wavefields, but the computational error it brings is unclear. In this study, we investigate the error caused by the quasi‐static EM approximation based on a horizontally layered model. With such an approximation we obtain a simplified set of Pride's equations and present an analytically based algorithm to solve the seismoelectric responses to an explosive source. First, we solve the seismic wavefields by ignoring the influence of the converted EM fields on the propagation of the seismic waves. Second, we simplify Maxwell equations to a Poisson equation of the electric potential, from which the EM signals are solved. The solved EM signals are compared with the solutions solved from the full Pride's equations to investigate the error caused by the quasi‐static EM approximation. The result shows that the quasi‐static EM approximation causes the loss of the electric field accompanying the S waves and yields errors in modeling the coseismic magnetic fields accompanying the S waves. The errors tend to become smaller when increasing the frequency and decreasing the salinity, implying that the quasi‐static EM approximation seems to be more suitable for simulating the coseismic EM signals under high‐frequency and low‐salinity conditions. The quasi‐static EM approximation also affects the simulation of the interfacial EM waves. Only under the condition that the wavelength of the EM wave is much larger than the source‐receiver distance, the quasi‐static method is valid in simulating the EM wave.

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Virtual electrode current injection using seismic focusing and seismoelectric conversion

Cited by 11 publications

References 27 publications

Simulation of the borehole quasistatic electric field excited by the acoustic wave during logging while drilling due to electrokinetic effect

Simulation of the borehole quasistatic electric field excited by the acoustic wave during logging while drilling due to electrokinetic effect

Seismo‐electromagnetic thin‐bed responses: Natural signal enhancements?

Comparison of full and quasi‐static seismoelectric analytically based modeling

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