scholarly journals Getting started with controlled-source electromagnetic 1D modeling

2017 ◽  
Vol 36 (4) ◽  
pp. 352-355 ◽  
Author(s):  
Dieter Werthmüller
Keyword(s):  
Forward Modeling ◽  
Higher Dimensions ◽  
Hydrocarbon Exploration ◽  
Fine Scale ◽  
One Dimensional ◽  
Controlled Source ◽  
1D Modeling ◽  
Resistivity Anisotropy ◽  
Complex Models ◽  
Diffusive Term

Forward modeling is an important part of understanding controlled-source electromagnetic (CSEM) responses. The diffusive term in the electromagnetic wave equation is dominant over the displacement term at these frequencies. It is the diffusive behavior that makes it difficult to imagine the actual propagation of the signal. An important tool in gaining experience therefore is forward modeling, and lots of it. The advantage of one-dimensional (1D) forward modeling, besides its speed, is to study isolated effects (see for instance Key, 2009): What is the influence of resistivity anisotropy, or of fine-scale resistivity variations? What is the influence of the airwave? With 1D modeling you can quickly study these effects in isolation before you go on to more complex models in higher dimensions. For an introduction to CSEM for hydrocarbon exploration see, for instance, Constable (2010).

Application of 3D marine controlled-source electromagnetic finite-element forward modeling to hydrocarbon exploration in the Flemish Pass Basin offshore Newfoundland, Canada

Geophysics ◽  
2018 ◽  
Vol 83 (2) ◽  
pp. WB33-WB49 ◽  
Author(s):  
Michael W. Dunham ◽  
SeyedMasoud Ansari ◽  
Colin G. Farquharson
Keyword(s):  
Finite Element ◽  
3D Model ◽  
A Priori ◽  
Simulated Data ◽  
Forward Modeling ◽  
Modeling Method ◽  
Hydrocarbon Exploration ◽  
Tetrahedral Mesh ◽  
Controlled Source ◽  
Marine Csem

In recent years, marine controlled-source electromagnetic (CSEM) surveying has become an effective supplemental interpretation tool to the seismic reflection method to help mitigate risk in an offshore exploration setting. Interpretation of marine CSEM data is commonly achieved via finite-difference inversions on rectilinear meshes, which has its merits, but the results are typically of very low resolution. The alternative is forward modeling, which requires a model to be known a priori, but the detail of the model can be created to reflect realistic geologic conditions. What is typically seen in the literature are applications of EM forward modeling codes to synthetic, and sometimes complex synthetic, models. However, what the literature is missing is an application that overcomes the challenges of applying a 3D forward modeling method to real models constructed from real information. We have developed an application of a 3D marine CSEM finite-element forward modeling method to the Bay du Nord prospect in the Flemish Pass Basin offshore Newfoundland. The 3D resistivity model, composed of four topographical layers and the Bay du Nord reservoir body, was built using 2D seismic data, one well log, and a marine CSEM inversion. Although other mesh representations have their merits, we chose to discretize our 3D model into an unstructured tetrahedral mesh because its flexibility enabled the accurate representation of complex structures while minimizing the number of unknowns. The availability of measured marine CSEM data allowed for the resistivities of each layer in the 3D model to be refined, and it also allowed for the simulated data to be assessed in the context of the real noise levels. A subsequent sensitivity analysis of the forward modeling results provided insights regarding the detectability of the Bay du Nord reservoir.

Mineral exploration with 3-D controlled-source electromagnetic method: a synthetic study of Sukhoi Log gold deposit

2019 ◽  
Vol 219 (3) ◽  
pp. 1698-1716 ◽  
Author(s):  
M Malovichko ◽  
A V Tarasov ◽  
N Yavich ◽  
M S Zhdanov
Keyword(s):  
Finite Difference ◽  
Gold Deposit ◽  
Large Scale ◽  
Mineral Exploration ◽  
Mineral Deposit ◽  
Hydrocarbon Exploration ◽  
Contraction Operator ◽  
Inversion Algorithm ◽  
Controlled Source ◽  
Regularized Inversion

SUMMARY This paper presents a feasibility study of using the controlled-source frequency-domain electromagnetic (CSEM) method in mineral exploration. The method has been widely applied for offshore hydrocarbon exploration; however, nowadays this method is rarely used on land. In order to conduct this study, we have developed a fully parallelized forward modelling finite-difference (FD) code based on the iterative solver with contraction-operator preconditioner. The regularized inversion algorithm uses the Gauss–Newton method to minimize the Tikhonov parametric functional with the Laplacian-type stabilizer. A 3-D parallel inversion code, based on the iterative finite-difference solver with the contraction-operator preconditioner, has been evaluated for the solution of the large-scale inverse problems. Using the computer simulation for a synthetic model of Sukhoi Log gold deposit, we have compared the CSEM method with the conventional direct current sounding and the CSEM survey with a single remote transmitter. Our results suggest that, a properly designed electromagnetic survey together with modern 3-D inversion could provide detailed information about the geoelectrical structure of the mineral deposit.

Radiation of charge moving in one-dimensional fine-scale random medium

1991 ◽  
Vol 34 (7) ◽  
pp. 691-693
Author(s):  
F. G. Bass ◽  
S. I. Khankina
Keyword(s):  
Random Medium ◽  
Fine Scale ◽  
One Dimensional

An introduction to marine controlled-source electromagnetic methods for hydrocarbon exploration

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. WA3-WA12 ◽  
Author(s):  
Steven Constable ◽  
Leonard J. Srnka
Keyword(s):  
Data Streams ◽  
Oceanic Lithosphere ◽  
Academic Community ◽  
Hydrocarbon Exploration ◽  
Reflection Seismology ◽  
Deep Drilling ◽  
Controlled Source ◽  
Electromagnetic Methods ◽  
Military Applications ◽  
Geophysical Technique

Early development of marine electromagnetic methods, dating back about 80 years, was driven largely by defense/military applications, and use for these purposes continues to this day. Deepwater, frequency-domain, electric dipole-dipole, controlled-source electromagnetic (CSEM) methods arose from academic studies of the oceanic lithosphere in the 1980s, and although the hydrocarbon exploration industry was aware of this work, the shallow-water environments being explored at that time were not ideally suited for its use. Low oil prices and increasingly successful results from 3D seismic methods further discouraged investment in costly alternative geophysical data streams. These circumstances changed in the late 1990s, when both Statoil and ExxonMobil began modeling studies and fieldtrials of CSEM surveying in deep water (around [Formula: see text] or deeper), specifically for characterizing the resistivity of previously identified drilling targets. Trials offshore Angola in 2000–2002 by both these companies showed that CSEM data can successfully be used to evaluate reservoir resistivity for targets as deep as several thousand meters. Both companies leveraged instrumentation and expertise from the academic community to make swift progress. The resulting rapid growth in the use of marine EM methods for exploration has created a demand for trained personnel that is difficult to meet; nevertheless, at this time, CSEM data represent a commercial commodity within the exploration business, and acquisition services are offered by three companies. The ability to determine the resistivity of deep drilling targets from the seafloor may well make marine CSEM the most important geophysical technique to emerge since 3D reflection seismology.

Optimal Design of Sandwich Beam With Frequency Constraints

2007 ◽  
Author(s):  
Vladimir B. Gantovnik ◽  
Alexander V. Lopatin ◽  
Lubov V. Shumkova
Keyword(s):  
Equations Of Motion ◽  
Sandwich Beam ◽  
Vibrational Analysis ◽  
Optimal Parameters ◽  
One Dimensional ◽  
Sandwich Plates And Shells ◽  
Complex Models ◽  
Plates And Shells ◽  
Transversal Vibrations ◽  
Selection Of

In this paper, we analyze selection of optimal parameters of sandwich beam in the presence of constraints on the frequencies of the transversal vibrations. The employed equations of motion take into account the transverse shear deformations in the core and rotatory inertia of the beam cross-section. The expressions for the transversal vibrations are obtained. The results show that one-dimensional model of the sandwich beam can be used for preliminary vibrational analysis of more complex models of sandwich plates and shells.

Improved One-Dimensional Unsteady Modeling of Thermally Choked Ram Accelerator in Subdetonative Velocity Regime

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Tarek Bengherbia ◽  
Yufeng Yao ◽  
Pascal Bauer ◽  
Marc Giraud ◽  
Carl Knowlen
Keyword(s):  
Mach Number ◽  
Combustion Zone ◽  
Control Volume ◽  
Theoretical Calculations ◽  
Combustion Process ◽  
Cfd Modeling ◽  
Thrust Coefficient ◽  
One Dimensional ◽  
Ram Accelerator ◽  
1D Modeling

The subdetonative propulsion mode using thermal choking has been studied with a one-dimensional (1D) real gas model that included projectile acceleration. Numerical results from a control volume analysis that accounted for unsteady flow effects established that the thrust coefficient versus Mach number profile was lower than that obtained with a quasi-steady model. This deviation correlates with experimental results obtained in a 38-mm-bore ram accelerator at 5.15 MPa fill pressure. Theoretical calculations were initially carried out with the assumption that the combustion process thermally choked the flow about one projectile length behind the projectile base. Thus the control volume length used in this 1D modeling was twice the projectile length, which is consistent with experimental observations at velocities corresponding to Mach number less than 3.5. Yet the choice of the length of the combustion zone and thus the control volume length remains a key issue in the unsteady modeling of the ram accelerator. The present paper provides a refinement of the unsteady one-dimensional model in which the effect of control volume length on the thrust coefficient and the projectile acceleration were investigated. For this purpose the control volume length determined from computational fluid dynamics (CFD) as a function of projectile Mach number was applied. The CFD modeling utilized the Reynolds-averaged Navier-Stokes (RANS) equations to numerically simulate the reacting flow in the ram accelerator. The shear-stress transport turbulence and the eddy dissipation combustion models were used along with a detailed chemical kinetic mechanism with six species and five-step reactions to account for the influence of turbulence and rate of heat release on the length of the combustion zone. These CFD computational results provided Mach number dependent estimates for the control volume length that were implemented in the 1D modeling. Results from the proposed improved 1D unsteady modeling were compared and validated with ram accelerator experimental data with significant improvements in terms of the predicted thrust dependence on Mach number.

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