Marine Controlled Source Electromagnetics: Principles, Methodologies, Future Commercial Applications

Edwards, Nigel

doi:10.1007/s10712-005-1830-3

Cited by 130 publications

(82 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Alternatively several receivers are trailed in a chain behind a transmitter (e.g. Edwards, 2005;Evans, 2007;Schwalenberg et al, 2009). The penetration or diffusion depth of the EM signal generated by a source dipole on or close to the seafloor depends on the frequency and amplitude of the source, and the conductivity of the media.…”

Section: Fundamentals Of the Csem Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of marine near-surface sediments by electromagnetic profiling

Müller

2010

GEOPHYSICS

View full text Add to dashboard Cite

II PrefaceThe research, development and implementation of an electromagnetic seafloor profiler GEM Shark has been made possible through the joint funding of the Center for Marine Environ- The main part of this cumulative thesis (Chapters 2-4) consists of three journal manuscripts (one published, two ready for submission), which are for the most part based on my own theoretical and technical developments, programming, field work and data interpretation. AbstractThis thesis investigates the theory, develops the technology and demonstrates the applicabilities for synchronous in-situ mapping of the magnetic and electric signatures of marine near-surface sediments. A marine electromagnetic profiler has been developed for coastal and shelf operations in 5 to 500 m water depths. The system was designed to resolve subtle and gradual variations in silt and clay content, porosity and diagenesis state of marine sediments at a sub-meter scale. An electromagnetic (EM) induction sensor (Geophex GEM-3)was modified for submarine operations and mounted into a special bottom-towed sled.Seafloor magnetic susceptibility and electric conductivity were calculated from the in-phase and quadrature component of the secondary electromagnetic field using a half-space inversion algorithm. Seawater conductivity was measured synchronously by an integrated conductivitytemperature-depth (CTD) probe. The electric conductivity depends on porosity, the grain-size distribution and conductivity of the pore fluid. Magnetic susceptibility was used in this study as a proxy for fine-grained terrigenous clay/silt content, diagenetically forced magnetite depletion, as well as anthropogenic contaminants.The three attached manuscripts address different applications of the modified EM profiler.The first manuscript develops the physical and technical principles of the method and presents first results regarding the facies, early diagenesis, transport, and deposition of near-surface sediments on the NW Iberian shelf. The second manuscript combines high-resolution acoustic, magnetometric, and electromagnetic profiling with sample-based rock magnetic and geochemical analyses related to submarine groundwater discharge in a Baltic Sea estuary. The third manuscript is an application of the EM profiler to study the contamination of coastal areas by ferrous objects, organic matter and heavy metal pollution for coastal zone management of the Ría de Vigo, a NW Iberian estuary. Chapter 1

show abstract

Section: Fundamentals Of the Csem Methodsmentioning

confidence: 99%

“…Targets for CSEM surveys are, among others, mid-ocean ridges, hydrothermal vent systems, and gas hydrates (e.g. Baba, 2005;Edwards, 2005;Constable and Srnka, 2007).…”

Section: Marine Electromagnetic Soundingmentioning

confidence: 99%

Characterization of marine near-surface sediments by electromagnetic profiling

Müller

2010

GEOPHYSICS

View full text Add to dashboard Cite

show abstract

“…Consequently, the marine controlled-source electromagnetic (CSEM) technique (Constable et al 1998;Constable 2006;Key 2012) was modified to use higher transmitted frequencies and a fixed offset three-axis electric field receiver, to extend the CSEM capability to detect shallow and subtle resistivity anomalies with high resolution (Weitemeyer & Constable 2010). CSEM sounding is highly sensitive to volumetric changes in resistivity (Edwards 2005;Constable 2010), mainly related to pore fluid properties; therefore, it can detect robustly fluid migration pathways and quantify porosity (Harris & MacGregor 2006;MacGregor & Tomlinson 2014;Naif et al 2015).…”

Section: Marine Csem Surveymentioning

confidence: 99%

Controlled-source electromagnetic and seismic delineation of subseafloor fluid flow structures in a gas hydrate province, offshore Norway

et al. 2016

View full text Add to dashboard Cite

SUMMARYDeep sea pockmarks underlain by chimney-like or pipe structures that contain methane hydrate are abundant along the Norwegian continental margin. In such hydrate provinces the interaction between hydrate formation and fluid flow has significance for benthic ecosystems and possibly climate change. The Nyegga region, situated on the western Norwegian continental slope, is characterized by an extensive pockmark field known to accommodate substantial methane gas hydrate deposits. The aim of this study is to detect and delineate both the gas hydrate and free gas reservoirs at one of Nyegga's pockmarks.In 2012, a marine controlled-source electromagnetic (CSEM) survey was performed at a pockmark in this region, where high-resolution three-dimensional seismic data were previously collected in 2006. Two-dimensional CSEM inversions were computed using the data acquired by ocean bottom electrical field receivers. Our results, derived from un- constrained and seismically constrained CSEM inversions, suggest the presence of two distinctive resistivity anomalies beneath the pockmark: a shallow vertical anomaly at the underlying pipe structure, likely due to gas hydrate accumulation, and a laterally extensive anomaly attributed to a free gas zone below the base of the gas hydrate stability zone. This work contributes to a robust characterization of gas hydrate deposits within sub-seafloor fluid flow pipe structures.

show abstract

“…The receivers are sensors that, deposited on the ocean floor, can measure up to three components (X, Y, Z). More details on the method's theory can be obtained in Edwards (2005) and Constable and Srnka (2007). The CSEM method had its initial development around the 1970 decade, aimed at solving academic studies in the mapping of the resistivity structure of the marine floor at great depths (Constable & Cox 1996).…”

Section: Introductionmentioning

confidence: 99%

Marlim R3D: a realistic model for CSEM simulations - phase I: model building

Carvalho

Menezes

2017

Braz. J. Geol.

View full text Add to dashboard Cite

ABSTRACT:The marine controlled-source electromagnetic (CSEM) method provides complementary information to seismic imaging in the exploration of sedimentary basins. The CSEM is mainly used for reservoir scanning and appraisal. The CSEM interpretation workflow is heavily based on inversion and forward -modeling for hypothesis testing. Until the recent past, the effectiveness of a given workflow was achieved after the drilling results, as there wasn't any geological complex model available to serve as a benchmark. In the present paper, we describe the workflow to build up Marlim R3D, a realistic and complex geoelectric model. Marlim R3D aims to be a reference model of turbidite reservoirs of the Brazilian continental margin. Our model is based on seismic interpretation and constrained by the input of available well-log information. The workflow used is composed of seven steps: seismic and well-log dataset loading, well-tie, Vp cube construction, Vp resistivity calibration, time-depth conversion, resistivity cube construction, and quality-control check. As a result, we obtained an interpreted dataset composed by main stratigraphic horizons, pseudo-well logs, and the resistivity cubes. These elements were made freely available for research or commercial use, under the Creative Common License, at the Zenodo platform. KEYWORDS

show abstract

Marine Controlled Source Electromagnetics: Principles, Methodologies, Future Commercial Applications

Cited by 130 publications

References 31 publications

Characterization of marine near-surface sediments by electromagnetic profiling

Characterization of marine near-surface sediments by electromagnetic profiling

Controlled-source electromagnetic and seismic delineation of subseafloor fluid flow structures in a gas hydrate province, offshore Norway

Marlim R3D: a realistic model for CSEM simulations - phase I: model building

Contact Info

Product

Resources

About