Research on Pseudo-2D Joint Inversion of TEM and CSAMT Based on Well Log Constraint

The transient electromagnetic method (TEM) and controlled-source audio-frequency magnetotellurics method (CSAMT) are commonly used in detecting water abundance of rock formation and faults in coal mines. However, these methods show low accuracy, given the multiplicity of their inversion results, especially for areas with minor differences in lithology and electrical property. To improve the accuracy of electromagnetic exploration, a pseudo-2D joint inversion is performed. The objective function of this pseudo-2D joint inversion is established, and the joint inversion process is constrained by resistivity logging data. Afterward, the symmetric successive over-relaxation (SSOR) is used to realize the pseudo-2D joint inversion calculation of TEM and CSAMT with well log constraint. The effectiveness of joint inversion is verified by combining synthetic and field data. Results show that the pseudo-2D joint inversion results of TEM and CSAMT with well log constraint correspond to the actual geological situation. Compared with either TEM or CSAMT, joint inversion has a significantly better capability of reflecting water abundance in rock formation and faults.

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Global optimization to retrieve borehole-derived petrophysical properties of carbonates

Geophysics ◽

10.1190/geo2018-0863.1 ◽

2020 ◽

Vol 85 (3) ◽

pp. D75-D82

Author(s):

Alireza Shahin ◽

Mike Myers ◽

Lori Hathon

Keyword(s):

Dielectric Constant ◽

Electrical Resistivity ◽

Global Optimization ◽

Joint Inversion ◽

Joint Modeling ◽

Carbonate Reservoir ◽

Dual Porosity ◽

Model Parameters ◽

Well Log ◽

Petrophysical Properties

Joint modeling and inversion of frequency-dependent dielectric constant and electrical resistivity well-log measurements has been addressed in literature in recent years. However, this problem is not studied for dual-porosity carbonate formations. Besides, the salinity and matrix dielectric constant are presumed to be known in previous studies. We have combined a model for brine dielectric constant and two laboratory-supported models for the electrical resistivity and dielectric constant of dual-porosity carbonates. Using this methodology, we replicate electrical resistivity and dielectric well-log measurements. Using a stochastic global optimization algorithm, we formulate a joint inversion workflow to estimate petrophysical properties of interest. For a constructed dual-porosity carbonate reservoir, we determine that the inversion workflow matches the forward-modeled data for the oil column, water column, and transition zone. We also found that our inversion workflow is capable to retrieve local model parameters (water-filled intergranular porosity and water-filled vuggy porosity) and global model parameters (matrix dielectric constant, lithology exponents for intergranular and vuggy pores, and salinity) with reasonable accuracy.

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Interpretation of 3-D effects in long‐offset transient electromagnetic (LOTEM) soundings in the Münsterland area/Germany

Geophysics ◽

10.1190/1.1443327 ◽

1992 ◽

Vol 57 (9) ◽

pp. 1127-1137 ◽

Cited By ~ 39

Author(s):

Andreas Hördt ◽

Vladimir L. Druskin ◽

Leonid A. Knizhnerman ◽

Kurt‐Martin Strack

Keyword(s):

Integral Equation ◽

Thin Sheet ◽

Three Dimensional ◽

Equation Modeling ◽

Data Sets ◽

Sign Reversal ◽

Near Surface ◽

Transient Electromagnetic ◽

Long Offset ◽

Geological Situation

The interpretation of long‐offset transient electromagnetic (LOTEM) data is usually based on layered earth models. Effects of lateral conductivity variations are commonly explained qualitatively, because three‐dimensional (3-D) numerical modeling is not readily available for complex geology. One of the first quantitative 3-D interpretations of LOTEM data is carried out using measurements from the Münsterland basin in northern Germany. In this survey area, four data sets show effects of lateral variations including a sign reversal in the measured voltage curve at one site. This sign reversal is a clear indicator of two‐dimensional (2-D) or 3-D conductivity structure, and can be caused by current channeling in a near‐surface conductive body. Our interpretation strategy involves three different 3-D forward modeling programs. A thin‐sheet integral equation modeling routine used with inversion gives a first guess about the location and strike of the anomaly. A volume integral equation program allows models that may be considered possible geological explanations for the conductivity anomaly. A new finite‐difference algorithm permits modeling of much more complex conductivity structures for simulating a realistic geological situation. The final model has the zone of anomalous conductivity aligned below a creek system at the surface. Since the creeks flow along weak zones in this area, the interpretation seems geologically reasonable. The interpreted model also yields a good fit to the data.

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Objective function analysis for electric soundings (VES), transient electromagnetic soundings (TEM) and joint inversion VES/TEM

Journal of Applied Geophysics ◽

10.1016/j.jappgeo.2017.09.016 ◽

2017 ◽

Vol 146 ◽

pp. 120-137 ◽

Cited By ~ 1

Author(s):

Cassiano Antonio Bortolozo ◽

Oleg Bokhonok ◽

Jorge Luís Porsani ◽

Fernando Acácio Monteiro dos Santos ◽

Liliana Alcazar Diogo ◽

...

Keyword(s):

Objective Function ◽

Function Analysis ◽

Joint Inversion ◽

Transient Electromagnetic ◽

Electromagnetic Soundings

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An application of the NSGA-II algorithm in Pareto joint inversion of 2D magnetic and gravity data

Geology, Geophysics and Environment ◽

10.7494/geol.2021.47.2.59 ◽

2021 ◽

Vol 47 (2) ◽

pp. 59-70

Author(s):

Katarzyna Miernik ◽

Elżbieta Węglińska ◽

Tomasz Danek ◽

Andrzej Leśniak

Keyword(s):

Pareto Front ◽

Joint Inversion ◽

Gravity Data ◽

Model Parameters ◽

Final Solution ◽

Inversion Process ◽

Nsga Ii ◽

Heat Map ◽

Real Model ◽

All Solutions

Joint inversion is a widely used geophysical method that allows model parameters to be obtained from the observed data. Pareto inversion results are a set of solutions that include the Pareto front, which consists of non-dominated solutions. All solutions from the Pareto front are considered the most feasible models from which a particular one can be chosen as the final solution. In this paper, it is shown that models represented by points on the Pareto front do not reflect the shape of the real model. In this contribution, a collective approach is proposed to interpret the geometry of models retrieved in inversion. Instead of choosing single solutions from the Pareto front, all obtained solutions were combined in one “heat map”, which is a plot representing the frequency of points belonging to all returned objects from the solution set. The conducted experiment showed that this approach limits the problem of equivalence and is a promising way of representing the geometry of the model that was retrieved in the inversion process.

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Detecting Grounding Grid Orientation: Transient Electromagnetic Approach

Applied Sciences ◽

10.3390/app9245270 ◽

2019 ◽

Vol 9 (24) ◽

pp. 5270 ◽

Cited By ~ 4

Author(s):

Aamir Qamar ◽

Inzamam Ul Haq ◽

Majed Alhaisoni ◽

Nadia Nawaz Qadri

Keyword(s):

Eddy Currents ◽

Comsol Multiphysics ◽

Electromagnetic Environment ◽

Diagonal Branch ◽

Transient Electromagnetic ◽

Grounding Grid ◽

The Status ◽

Mesh Spacing ◽

Grid Orientation ◽

Inversion Calculation

The configuration is essential to diagnose the status of the grounding grid, but the orientation of the unknown grounding grid is ultimately required to diagnose its configuration explicitly. This paper presents a transient electromagnetic method (TEM) to determine grounding grid orientation without excavation. Unlike the existing pathological solutions, TEM does not enhance the surrounding electromagnetic environment. A secondary magnetic field as a consequence of induced eddy currents is subjected to inversion calculation. The orientation of the grounding grid is diagnosed from the equivalent resistivity distribution against the circle perimeter. High equivalent resistivity at a point on the circle implies the grounding grid conductor and vice versa. Furthermore, various mesh configurations including the presence of a diagonal branch and unequal mesh spacing are taken into account. Simulations are performed using COMSOL Multiphysics and MATLAB to verify the usefulness of the proposed method.

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Fuzzy C-Mean Clustering and Joint Inversion of Well Log Data for Porosity Prediction

10.3997/2214-4609.202177057 ◽

2021 ◽

Author(s):

D.T. Kieu ◽

N. Pham Quy ◽

M. Ha Quang ◽

G. Pham Huy ◽

H. Doan Huy ◽

...

Keyword(s):

Joint Inversion ◽

Well Log ◽

Log Data

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A new petrophysical joint inversion workflow: Advancing on reservoir’s characterization challenges

Interpretation ◽

10.1190/int-2017-0225.1 ◽

2018 ◽

Vol 6 (3) ◽

pp. SG33-SG39 ◽

Cited By ~ 4

Author(s):

Fabio Miotti ◽

Andrea Zerilli ◽

Paulo T. L. Menezes ◽

João L. S. Crepaldi ◽

Adriano R. Viana

Keyword(s):

Reservoir Characterization ◽

Joint Inversion ◽

Oil Field ◽

Well Log ◽

Complementary Information ◽

Reservoir Properties ◽

Reservoir Rocks ◽

Controlled Source ◽

Fluid Properties

Reservoir characterization objectives are to understand the reservoir rocks and fluids through accurate measurements to help asset teams develop optimal production decisions. Within this framework, we develop a new workflow to perform petrophysical joint inversion (PJI) of seismic and controlled-source electromagnetic (CSEM) data to resolve for reservoirs properties. Our workflow uses the complementary information contained in seismic, CSEM, and well-log data to improve the reservoir’s description drastically. The advent of CSEM, measuring resistivity, brought the possibility of integrating multiphysics data within the characterization workflow, and it has the potential to significantly enhance the accuracy at which reservoir properties and saturation, in particular, can be determined. We determine the power of PJI in the retrieval of reservoir parameters through a case study, based on a deepwater oil field offshore Brazil in the Sergipe-Alagoas Basin, to augment the certainty with which reservoir lithology and fluid properties are constrained.

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