scholarly journals Modeling of Self Potential (SP) Anomalies over a Polarized Rod with Finite Depth Extents

2019 ◽  
pp. 51-56
Author(s):  
T. S. Fagbemigun ◽  
M. O. Olorunfemi ◽  
S. A. Wahab
Keyword(s):  
Potential Distribution ◽  
Synthetic Data ◽  
Field Measurements ◽  
Finite Depth ◽  
Distribution Data ◽  
Geophysical Field ◽  
Dip Angle ◽  
Self Potential ◽  
Depth Of Burial ◽  
Sp Anomaly

Modeling is a powerful tool used by Geoscientists to provide pre-knowledge about the expectations of any geophysical field measurements. This study generates Self Potential (SP) anomalies over a typical dike-like structure to observe the influence of depth of burial and dip on SP anomalies. A computer program was developed from the potential distribution equation of an inclined polarized rod with a limited depth extent using Visual Basic (VB) programming language to produce synthetic data for potential distribution. The potential distribution data were used to generate theoretical SP anomaly curves for a polarized rod for varying depth of burial and dip. Twenty SP anomaly curves were generated with different dip values and depth of burial and from these curves, superimposed curves were also generated. The anomalies were analyzed for the effect of depth of burial and attitude or dip. The SP anomaly curves generated show that an increase in depth of burial causes a reduction in the peak negative amplitude of SP anomaly curves. For inclined polarized rod at relatively shallow depth (<2.0 m), the peak negative amplitude remains virtually the same with a positive shoulder over the down dip side of the target. Also as the dip angle decreases from 90o for a fixed depth of burial, the anomaly curves become asymmetrical. At 0o, the distance between the peak negative and peak positive amplitude of the anomaly curve is equal to the linear extent of the rod. Therefore, this study shows that the depth of burial inversely influences the amplitude of self-potential (SP) anomalies while the dip angle affects the form or symmetry of anomaly curves.

Thermoelectric self-potential and resistivity data localize the burning front of underground coal fires

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. B259-B273 ◽  
Author(s):  
A. Revil ◽  
M. Karaoulis ◽  
S. Srivastava ◽  
S. Byrdina
Keyword(s):  
Coal Seam ◽  
Joint Inversion ◽  
Synthetic Data ◽  
Ground Surface ◽  
Thermal Anomaly ◽  
Silica Sand ◽  
Geophysical Field ◽  
Burning Front ◽  
Resistivity Data ◽  
Self Potential

Self-potential signals and resistivity data can be jointly inverted or analyzed to track the position of the burning front of an underground coal-seam fire. We first investigate the magnitude of the thermoelectric coupling associated with the presence of a thermal anomaly (thermoelectric current associated with a thermal gradient). A sandbox experiment is developed and modeled to show that in presence of a heat source, a negative self-potential anomaly is expected at the ground surface. The expected sensitivity coefficient is typically on the order of [Formula: see text] in a silica sand saturated by demineralized water. Geophysical field measurements gathered at Marshall (near Boulder, CO) show clearly the position of the burning front in the electrical resistivity tomogram and in the self-potential data gathered at the ground surface with a negative self-potential anomaly of about [Formula: see text]. To localize more accurately the position of the burning front, we developed a strategy based on two steps: (1) We first jointly invert resistivity and self-potential data using a cross-gradient approach, and (2) a joint interpretation of the resistivity and self-potential data is made using a normalized burning front index (NBI). The value of the NBI ranges from 0 to 1 with 1 indicating a high probability to find the burning front (strictly speaking, the NBI is, however, not a probably density). We validate first this strategy using synthetic data and then we apply it to the field data. A clear source is localized at the expected position of the burning front of the coal-seam fire. The NBI determined from the joint inversion is only slightly better than the value determined from independent inversion of the two geophysical data sets.

A rapid graphical method for the interpretation of the self‐potential anomaly over a two‐dimensional inclined sheet of finite depth extent

Geophysics ◽  
1988 ◽  
Vol 53 (8) ◽  
pp. 1126-1128 ◽  
Author(s):  
H. V. Ram Babu ◽  
D. Atchuta Rao
Keyword(s):  
Graphical Method ◽  
Amplitude Ratio ◽  
Finite Depth ◽  
Ore Deposits ◽  
Characteristic Features ◽  
Zero Potential ◽  
Depth Extent ◽  
Self Potential ◽  
Sp Anomaly ◽  
Inclined Sheet

The inclined sheet is an important model for interpreting self‐potential (SP) anomalies over elongated ore deposits. Many techniques (Roy and Chowdhurry, 1959; Meiser, 1962; Paul, 1965; Atchuta Rao et al., 1982; Atchuta Rao and Ram Babu, 1983; Murty and Haricharan, 1985) have been proposed for interpreting SP anomalies over this model. We propose a simple graphical procedure for locating the upper and lower edges of an inclined sheet of infinite strike extent from its SP anomaly V(x) using a few characteristics points including [Formula: see text] [Formula: see text], and [Formula: see text] The amplitude ratio [Formula: see text], is shown to vary with θ, the dip of the sheet, making it possible to estimate θ. The two edges of the sheet are equidistant from the abscissa of [Formula: see text] the zero potential point. The sheet, when extrapolated onto the line of observation, meets the x‐axis at a point where [Formula: see text] From these characteristic features of V(x), the sheet can be located easily using the simple geometrical construction presented below.

scholarly journals Measurement of unsaturated meltwater percolation flux in seasonal snowpack using self-potential

2021 ◽  
pp. 1-16
Author(s):  
Wilson S. Clayton
Keyword(s):  
Method Development ◽  
Water Saturation ◽  
Field Measurements ◽  
Time Domain Reflectometry ◽  
Electrode Spacing ◽  
Glacier Mass Balance ◽  
Wetting Front ◽  
Electrical Field Strength ◽  
Water Redistribution ◽  
Self Potential

Abstract This paper presents a feasibility study of in situ field measurements of unsaturated meltwater percolation flux within the vertical profile of a snowpack, using the self-potential (SP) method. On-site snowmelt column tests calibrated the SP measurements. The SP data measured electrical field strength with an electrode spacing of 20 cm, and coincident water saturation (Sw) measurements using time domain reflectometry allowed calculation of SP-modeled vertical percolation flux (qsp), expressed as Darcy velocity. The results reflected transient diurnal snowmelt dynamics, with peak flux lagging arrival of a saturation wetting front. Peak daily qsp was 60 to >300 mm d−1, whereas daily snowmelt was 20–50 mm w.e. Surface refreezing events appeared to cause upward flow, possibly representing water redistribution toward the freezing boundary. Calculated fluxes were comparable to actual fluxes, although average errors ranged from −15 to +46% compared to average of melt expected from surface energy-balance and ablation stake measurements. By advancing method development to measure unsaturated meltwater percolation flux in snowpacks this study creates opportunities to study fundamental snowmelt processes, may improve mathematical modeling and may supplement glacier mass-balance studies and studies of snowmelt interactions with avalanches, groundwater and surface water.

scholarly journals Implications of Self-Potential Distribution for Groundwater Flow System in a Nonvolcanic Mountain Slope

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Tada-nori Goto ◽  
Kazuya Kondo ◽  
Rina Ito ◽  
Keisuke Esaki ◽  
Yasuo Oouchi ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
General Trend ◽  
Flow System ◽  
Ground Surface ◽  
Mountain Slope ◽  
Infiltration Process ◽  
Groundwater Flow System ◽  
Self Potential ◽  
Sp Anomaly ◽  
Fft Analysis

Self-potential (SP) measurements were conducted at Mt. Tsukuba, Japan, which is a nonvolcanic mountain, to infer groundwater flow system in the mountain. Survey routes were set around the northern slope, and the reliability of observed SP anomaly was checked by using SP values along parallel survey routes; the error was almost within 10 mV. The FFT analysis of the spatial SP distribution allows us a separation of raw data into two components with shorter and longer wavelength. In the shorter (altitudinal) wavelength than ∼200 meters, several positive SP peaks of more than 100 mV in magnitude are present, which indicate shallow perched water discharges along the slope. In the regional SP pattern of longer wavelength, there are two major perturbations from the general trend reflecting the topographic effect. By comparing the SP and hydrological data, the perturbation around the foothill is interpreted to be caused by heterogeneous infiltration at the ground surface. The perturbation around the summit is also interpreted to be caused by heterogeneous infiltration process, based on a simplified numerical modeling of SP. As a result, the SP pattern is well explained by groundwater flow and infiltration processes. Thus, SP data is thought to be very useful for understanding of groundwater flow system on a mountain scale.

REAL-TIME 2.5D INVERSION OF LWD RESISTIVITY MEASUREMENTS USING DEEP LEARNING FOR GEOSTEERING APPLICATIONS ACROSS FAULTED FORMATIONS

2021 ◽  
Author(s):  
Kyubo Noh ◽  
◽  
Carlos Torres-Verdín ◽  
David Pardo ◽  
◽  
...  
Keyword(s):  
Deep Learning ◽  
Real Time ◽  
Fault Plane ◽  
Synthetic Data ◽  
Field Measurements ◽  
Geological Structure ◽  
Inversion Method ◽  
Adaptive Finite Element ◽  
Resistivity Measurements ◽  
Lwd Resistivity

We develop a Deep Learning (DL) inversion method for the interpretation of 2.5-dimensional (2.5D) borehole resistivity measurements that requires negligible online computational costs. The method is successfully verified with the inversion of triaxial LWD resistivity measurements acquired across faulted and anisotropic formations. Our DL inversion workflow employs four independent DL architectures. The first one identifies the type of geological structure among several predefined types. Subsequently, the second, third, and fourth architectures estimate the corresponding spatial resistivity distributions that are parameterized (1) without the crossings of bed boundaries or fault plane, (2) with the crossing of a bed boundary but without the crossing of a fault plane, and (3) with the crossing of the fault plane, respectively. Each DL architecture employs convolutional layers and is trained with synthetic data obtained from an accurate high-order, mesh-adaptive finite-element forward numerical simulator. Numerical results confirm the importance of using multi-component resistivity measurements -specifically cross-coupling resistivity components- for the successful reconstruction of 2.5D resistivity distributions adjacent to the well trajectory. The feasibility and effectiveness of the developed inversion workflow is assessed with two synthetic examples inspired by actual field measurements. Results confirm that the proposed DL method successfully reconstructs 2.5D resistivity distributions, location and dip angles of bed boundaries, and the location of the fault plane, and is therefore reliable for real-time well geosteering applications.

Promising Map-Aided Aircraft Navigation Systems

2021 ◽  
Vol 29 (1) ◽  
pp. 32-51
Author(s):  
E.V. Karshakov ◽  
◽  
B.V. Pavlov ◽  
M.Yu. Tkhorenko ◽  
I.A. Papusha ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Field Measurements ◽  
Navigation Systems ◽  
Geophysical Field ◽  
Airborne Measurements ◽  
Aircraft Navigation ◽  
Navigation Accuracy ◽  
Development Prospects

The paper analyses the development prospects for aircraft navigation systems using onboard geophysical field measurements. Prospective systems that are not widely applied yet are considered: magnetic gradiometers measuring the stationary magnetic field gradient, gravity gradiometers measuring the gravity field gradient, and electromagnetic systems measuring the alternating part of magnetic field. We discuss the main problems to be solved during airborne measurements of these parameters and give an overview of algorithms and hardware solutions. We analyse the results of onboard measurements and estimate the possible navigation accuracy.

scholarly journals An adaptable technique for comparative image assessment: Application to crosswell electromagnetic survey design for fluid monitoring

Geophysics ◽  
2021 ◽  
Vol 86 (3) ◽  
pp. E239-E256
Author(s):  
Michael Commer ◽  
David L. Alumbaugh ◽  
Michael Wilt ◽  
Abdullah Cihan ◽  
Evan S. Um ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Carbon Capture ◽  
Goodness Of Fit ◽  
Survey Design ◽  
Synthetic Data ◽  
Field Measurements ◽  
Logistic Function ◽  
Monitoring Method ◽  
Vertical Arrays ◽  
Spatial Volume

Reservoir integrity stewardship accompanying carbon capture and sequestration considers fluid extraction and reinjection as a risk-mitigating method against overpressuring that could lead to caprock damage and ensuing [Formula: see text] leakage. Crosswell electromagnetics offers a technically viable monitoring method with the spatial volume coverage necessary for reservoir-encompassing pressure management. However, a certain logistic dilemma for deep gas sequestration into saline and thus electrically conductive aquifers is that crosswell magnetic-field measurements underperform in the imaging of more resistive plume bodies, further exacerbated when vertical arrays intersect, as opposed to surround, plumes. Comparative synthetic-data plume imaging of such scenarios rates the information content of magnetic-field versus electric-field 3D crosswell layouts for reservoir and infrastructure conditions of a representative pilot site in a coastal area in Florida. The image quality of the resulting plume replications can be ranked numerically through a newly proposed semblance qualifier, appraising the model goodness of fit to a given reference. In contrast to common least-squares measures for goodness of fit, the semblance formulation uses classifying logistic function types, thus enabling a better distinction of predefined anomaly features.

scholarly journals PEMODELAN KONTINU 2-D BERBASIS EFEK ELEKTOKINETIK DENGAN FINITE ELEMENT PENDEKATAN GALERKIN

2019 ◽  
Vol 4 (2) ◽  
pp. 93
Author(s):  
Delia Meldra
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fluid Flow ◽  
Potential Distribution ◽  
Current Source ◽  
Velocity Modeling ◽  
Distribution Modeling ◽  
Fluid Flow Velocity ◽  
Self Potential ◽  
Element Method

Method refers to a measurement of naturally electric potential on the surface. Self Potential is one of thegeophysical methods that can be used to identify fluid flow in the subsurface. Finite element method hasbeen used to fluid flow velocity modeling, current source, and potential distribution modeling based onelectrokinetic effect in 2-D profile. The sign of potensial respon (negative or positive) is an important factorfor the interpretation of self-potential anomalies. Finite element method is one of the numerical methods forsolve the boundary value problems and the boundary conditions in the form of differential equations in SelfPotentialmodeling

scholarly journals New Distribution Data for Prussian Carp Carassius gibelio (Bloch 1782) in the Middle Black Sea Region of Turkey

2021 ◽  
Vol 79 (2) ◽  
pp. 83-88
Author(s):  
Serdar Yedier ◽  
Derya Bostanci ◽  
Nazmi Polat
Keyword(s):  
Invasive Species ◽  
Black Sea ◽  
Current Distribution ◽  
Potential Distribution ◽  
Morphological Data ◽  
Distribution Data ◽  
Black Sea Region ◽  
Prussian Carp ◽  
Carassius Gibelio ◽  
New Distribution

Abstract In this study, the new occurrence of Carassius gibelio belonging to the genus Carassius in Ulugöl Plateau Pond (Mesudiye-Ordu, Turkey) and Perşembe Plateau Pond (Aybastı-Ordu, Turkey) in the Middle Black Sea Region (Turkey) is reported. The distribution data of Prussian carp was updated in the Middle Black Sea Region of Turkey in comparison to the previously known data. Presenting morphological data of samples collected from two different areas in the Middle Black Sea Region may contribute to revealing the current distribution status of this invasive species and determining the potential distribution areas.

scholarly journals Field Measurements of Wave Directionality in Water of Finite Depth

2003 ◽  
Vol 25 (4) ◽  
pp. 437-446 ◽  
Author(s):  
Constantine Memos ◽  
Athanassios Ziros
Keyword(s):  
Field Measurements ◽  
Finite Depth ◽  
Wave Directionality
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