Electric potential source localization reveals a borehole leak during hydraulic fracturing

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. D93-D113 ◽  
Author(s):  
A. K. Haas ◽  
A. Revil ◽  
M. Karaoulis ◽  
L. Frash ◽  
J. Hampton ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Current Density ◽  
Electric Potential ◽  
Potential Distribution ◽  
Fluid Pressure ◽  
Acoustic Emissions ◽  
Least Square ◽  
Source Current ◽  
Electric Signals ◽  
Source Current Density

A laboratory experiment was performed to see if passively recorded electric signals can be inverted to retrieve the position of fluid leakages along a well during an attempt to hydraulically fracture a porous block in the laboratory. The cubic block was instrumented with 32 nonpolarizing sintered Ag/AgCl electrodes. During the test, several events were detected corresponding to fluid leakoff along the seal of the well. Each event showed a quick burst in the electric field followed by an exponential-type relaxation of the potential distribution over time. The occurrence of these “electric” events was always correlated with a burst in the acoustic emissions and a change in the fluid pressure. These self-potential data were inverted in two steps: (1) using a deterministic least-square algorithm with focusing to retrieve the position of the source current density in the block for a given snapshot in the electric potential distribution and (2) using a genetic algorithm to refine the position of the source current density on a denser grid. The results of the inversion were found to be in excellent agreement with the position of the well where the hydraulic test was performed and with the localization of the acoustic emissions in the vicinity of this well. This experiment indicates that passively recorded electric signals can be used to monitor fluid flow along the well during leakages, and perhaps monitor fluid flow for numerous applications involving hydromechanical disturbances.

Reduction of ocular artefacts in source current density brain mappings by ARX2 filtering

1995 ◽  
Vol 17 (4) ◽  
pp. 282-290 ◽  
Author(s):  
G.C. Filligoi ◽  
L. Capitanio ◽  
F. Babiloni ◽  
L. Fattorini ◽  
A. Urbano ◽  
...  
Keyword(s):  
Current Density ◽  
Ocular Artefacts ◽  
Source Current ◽  
Source Current Density

Self-potential monitoring of a salt plume

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. WA17-WA25 ◽  
Author(s):  
P. Martínez-Pagán ◽  
A. Jardani ◽  
A. Revil ◽  
A. Haas
Keyword(s):  
Real Time ◽  
Current Density ◽  
Potential Method ◽  
The Self ◽  
Contaminant Plume ◽  
Salty Water ◽  
Source Current ◽  
Self Potential ◽  
Over Time ◽  
Source Current Density

Nonintrusively monitoring the spread of contaminants in real time with a geophysical method is an important task in hydrogeophysics. We have developed a sandbox experiment showing that the self-potential method can locate both the source of leakage and the front of a contaminant plume. We monitored the leakage of a plume of salty water from a hole at the bottom of a small tank located at the top of a main sandbox. Initially, the sand was saturated by tap water. At a given time, a hole was opened at the bottom of the tank, allowing the salty water to migrate by diffusion and buoyancy-driven flow in the main sandbox. The bottom of the sandbox contained a network of 32 nonpolarizing silver-silver chloride electrodes with amplifiers, connected to a multichannel voltmeter. The self-potential response associated withthe migration of the salt plume in the sandbox was recorded over time. A self-potential anomaly was observed with amplitude varying from a few millivolts at the start of the leak to a few tens of millivolts after a few minutes. The self-potential data were inverted using a time-lapse tomographic algorithm to reconstruct the position of the volumetric source current density over time. A positive volumetric source current density was associated with the position of the leak at the bottom of the leaking tank, whereas a negative volumetric source current density was associated with the salinity front moving down inside the sandbox. These poles were well reproduced by performing a finite-element simulation of the problem. Using this information, we estimated the speed of the salt plume sinking inside the sandbox. Therefore, the self-potential method can be used to track, in real time, the position of the front of a contaminant plume in a porous material.

Seismoelectric numerical modeling on a grid

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. N57-N65 ◽  
Author(s):  
Seth S. Haines ◽  
Steven R. Pride
Keyword(s):  
Electric Fields ◽  
Electric Potential ◽  
Potential Distribution ◽  
Seismic Waves ◽  
Fresnel Zone ◽  
Near Field ◽  
Fluid Pressure ◽  
Heterogeneous Porous Media ◽  
Time Step ◽  
Electric Potential Distribution

Our finite-difference algorithm provides a new method for simulating how seismic waves in arbitrarily heterogeneous porous media generate electric fields through an electrokinetic mechanism called seismoelectric coupling. As the first step in our simulations, we calculate relative pore-fluid/grain-matrix displacement by using existing poroelastic theory. We then calculate the electric current resulting from the grain/fluid displacement by using seismoelectric coupling theory. This electrofiltration current acts as a source term in Poisson’s equation, which then allows us to calculate the electric potential distribution. We can safely neglect induction effects in our simulations because the model area is within the electrostatic near field for the depth of investigation (tens to hundreds of meters) and the frequency ranges ([Formula: see text] to [Formula: see text]) of interest for shallow seismoelectric surveys.We can independently calculate the electric-potential distribution for each time step in the poroelastic simulation without loss of accuracy because electro-osmotic feedback (fluid flow that is perturbed by generated electric fields) is at least [Formula: see text] times smaller than flow that is driven by fluid-pressure gradients and matrix acceleration, and is therefore negligible. Our simulations demonstrate that, distinct from seismic reflections, the seismoelectric interface response from a thin layer (at least as thin as one-twentieth of the seismic wavelength) is considerably stronger than the response from a single interface. We find that the interface response amplitude decreases as the lateral extent of a layer decreases below the width of the first Fresnel zone. We conclude, on the basis of our modeling results and of field results published elsewhere, that downhole and/or crosswell survey geometries and time-lapse applications are particularly well suited to the seismoelectric method.

Induced polarization response of porous media with metallic particles — Part 3: A new approach to time-domain induced polarization tomography

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. D345-D357 ◽  
Author(s):  
Deqiang Mao ◽  
André Revil
Keyword(s):  
Current Density ◽  
Time Domain ◽  
Induced Polarization ◽  
Charge Carriers ◽  
Secondary Source ◽  
Metallic Particles ◽  
Secondary Voltage ◽  
Source Current ◽  
Self Potential ◽  
Source Current Density

The secondary voltage associated with time-domain induced polarization data of disseminated metallic particles (such as pyrite and magnetite) in a porous material can be treated as a transient self-potential problem. This self-potential field is associated with the generation of a secondary-source current density. This source current density is proportional to the gradient of the chemical potentials of the [Formula: see text]- and [Formula: see text]-charge carriers in the metallic particles or ionic charge carriers in the pore water including in the electrical double layer coating the surface of the metallic grains. This new way to treat the secondary voltages offers two advantages with respect to the classical approach. The first is a gain in terms of acquisition time. Indeed, the target can be illuminated with a few primary current sources, all the other electrodes being used simultaneously to record the secondary voltage distribution. The second advantage is with respect to the inversion of the obtained data. Indeed, the secondary (source) current is linearly related to the secondary voltage. Therefore, the inverse problem of inverting the secondary voltages is linear with respect to the source current density, and the inversion can be done in a single iteration. Several iterations are, however, required to compact the source current density distribution, still obtaining a tomogram much faster than inverting the apparent chargeability data using the classical Gauss-Newton approach. We have performed a sandbox experiment with pyrite grains locally mixed to sand at a specific location in the sandbox to demonstrate these new concepts. A method initially developed for self-potential tomography is applied to the inversion of the secondary voltages in terms of source current distribution. The final result compares favorably with the classical inversion of the time-domain induced polarization data in terms of chargeability, but it is much faster to perform.

scholarly journals Análise comparativa do desempenho elétrico de isoladores tipo pino sob diferentes condições de poluição

2019 ◽  
Vol 1 (47) ◽  
pp. 160
Author(s):  
Bruno Albuquerque Dias ◽  
Edson Guedes Costa ◽  
Larissa Diniz ◽  
Antonio Francisco Leite Neto ◽  
João Marcos Leal Rocha ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Electric Field ◽  
Current Density ◽  
Electric Potential ◽  
Potential Distribution ◽  
Electric Potential Distribution ◽  
Pollution Levels ◽  
Pollution Intensity ◽  
Distribution Lines

<p>This paper analyzes the performance of insulators subjected to pollution levels related to two topologies of 15 kV voltage class polymeric distribution isolators. A software was used to simulate the influence of various levels of pollution on the operation of insulators. Pollution layers with the variation of conductivity and permittivity parameters were modeled on the surface of the insulators and the electric potential, the electric field and the current density in the polymeric isolators were obtained by computer simulation. The results showed the increase of the electric potential distribution, the electric field and the current density of the insulators as the pollution intensity increases. The results proved that the topology with four sheds performs better in polluted conditions. Thus, it can be concluded that in long distribution lines different insulator topologies can be used, according to the region and microclimate that the insulators are exposed.</p>

A novel variant of the H-Φ field formulation for magnetostatic and eddy current problems

2019 ◽  
Vol 38 (5) ◽  
pp. 1545-1561 ◽  
Author(s):  
Jasmin Smajic
Keyword(s):  
Magnetic Field ◽  
Numerical Method ◽  
Frequency Domain ◽  
Current Density ◽  
Eddy Current ◽  
Content Type ◽  
Multiply Connected ◽  
Multiply Connected Regions ◽  
Source Current ◽  
Source Current Density

Purpose The paper presents a new variant of the H-Φ field formulation for solving 3-D magnetostatic and frequency domain eddy current problems. The suggested formulation uses the vector and scalar tetrahedral elements within conducting and non-conducting domains, respectively. The presented numerical method is capable of solving multiply connected regions and eliminates the need for computing the source current density and the source magnetic field before the actual magnetostatic and eddy current simulations. The obtained magnetostatic results are verified by comparison against the corresponding results of the standard stationary current distribution analysis combined with the Biot-Savart integration. The accuracy of the eddy current results is demonstrated by comparison against the classical A-A-f approach in frequency domain. Design/methodology/approach The theory and implementation of the new H-Φ magnetostatic and eddy current solver is presented in detail. The method delivers reliable results without the need to compute the source current density and source magnetic field before the actual simulation. Findings The proposed H-Φ produce radically smaller and considerably better conditioned equation systems than the alternative A-A approach, which usually requires the unphysical regularization in terms of a low electric conductivity value within the nonconductive domain. Originality/value The presented numerical method is capable of solving multiply connected regions and eliminates the need for computing the source current density and the source magnetic field before the actual magnetostatic and eddy current simulations.

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