The Controlled Source Electro‐Magnetic (CSEM) Method in shallow water: a calibration survey

2010 ◽  
Author(s):  
Mathieu Darnet ◽  
Peter Van Der Sman ◽  
Folkert Hindriks ◽  
Alessandro Sandrin ◽  
Philip Christian ◽  
...  
Keyword(s):  
Shallow Water ◽  
Controlled Source ◽  
Electro Magnetic

Deep Controlled Source Electro-Magnetic Sensing: A Cost Effective, Long-Term Tool for Sequestration Monitoring

2017 ◽  
Author(s):  
Douglas LaBrecque ◽  
◽  
Russell D. Brigham ◽  
Conny Schmidt-Hattenburger ◽  
Evan Um ◽  
...  
Keyword(s):  
Cost Effective ◽  
Magnetic Sensing ◽  
Controlled Source ◽  
Electro Magnetic

scholarly journals Source modification for efficiency enhancement of marine controlled-source electromagnetic method

2021 ◽  
Vol 18 (2) ◽  
Author(s):  
Amir Rostami ◽  
Noorhana Yahaya ◽  
Hassan Soleimani ◽  
Muhammad Rauf ◽  
Tadiwa E Nyamasvisva ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Shallow Water ◽  
Method Of Moments ◽  
Experimental Setup ◽  
Efficiency Enhancement ◽  
Shooting Methods ◽  
Detection Capability ◽  
Controlled Source ◽  
Element Simulation ◽  
Electromagnetic Source

Abstract Controlled-source electromagnetics is a strongly efficient technique to explore deep-water marine hydrocarbon reservoirs. However, the shallow-water unsolved limitations of electromagnetic shooting methods still exist. In this regard, this work aims to alter the existing conventional electromagnetic source such that it can converge the down-going electromagnetic wave while simultaneously dispersing the up-going electromagnetic energy to minimise the airwave in shallow water. This work presents computed electric current distribution inside a modified transmitter, using a method of moments. Simulation and an experiment-based methodology are applied to this work. Finite element simulation of the response of the modified transmitter displayed the capability of the new transmitter in dispersing the airwave, by 15%. The experimental setup confirmed a better performance of the new transmitter, showing hydrocarbon delineation of up to 48%, compared to the existing conventional transmitter, with 25% oil delineation at the same depths in the same environment. Modification of the electromagnetic source to unbalance the up-down signals may have the potential to enhance the delineation magnitude of the target signal and, as a result, significantly improve oil detection capability.

scholarly journals Boat-towed radio-magnetotelluric and controlled source audio-magnetotelluric study to resolve fracture zones at Äspö Hard Rock Laboratory site, Sweden

2019 ◽  
Vol 218 (2) ◽  
pp. 1008-1031 ◽  
Author(s):  
Shunguo Wang ◽  
Mehrdad Bastani ◽  
Steven Constable ◽  
Thomas Kalscheuer ◽  
Alireza Malehmir
Keyword(s):  
Shallow Water ◽  
Penetration Depth ◽  
Large Scale ◽  
Hard Rock ◽  
High Water ◽  
Fracture Zones ◽  
Geological Structures ◽  
Near Surface ◽  
Controlled Source ◽  
Rock Laboratory

SUMMARY Boat-towed radio-magnetotelluric (RMT) measurements using signals between 14 and 250 kHz have attracted increasing attention in the near-surface applications for shallow water and archipelago areas. A few large-scale underground infrastructure projects, such as the Stockholm bypass in Sweden, are planned to pass underneath such water zones. However, in cases with high water salinity, RMT signals have a penetration depth of a few metres and do not reach the geological structures of interest in the underlying sediments and bedrock. To overcome this problem, controlled source signals at lower frequencies of 1.25 to 12.5 kHz can be utilized to improve the penetration depth and to enhance the resolution for modelling deeper underwater structures. Joint utilization of boat-towed RMT and controlled source audio-magnetotellurics (CSAMT) was tested for the first time at the Äspö Hard Rock Laboratory (HRL) site in south-eastern Sweden to demonstrate acquisition efficiency and improved resolution to model fracture zones along a 600-m long profile. Pronounced galvanic distortion effects observed in 1-D inversion models of the CSAMT data as well as the predominantly 2-D geological structures at this site motivated usage of 2-D inversion. Two standard academic inversion codes, EMILIA and MARE2DEM, were used to invert the RMT and CSAMT data. EMILIA, an object-oriented Gauss–Newton inversion code with modules for 2-D finite difference and 1-D semi-analytical solutions, was used to invert the RMT and CSAMT data separately and jointly under the plane-wave approximation for 2-D models. MARE2DEM, a Gauss–Newton inversion code for controlled source electromagnetic 2.5-D finite element solution, was modified to allow for inversions of RMT and CSAMT data accounting for source effects. Results of EMILIA and MARE2DEM reveal the previously known fracture zones in the models. The 2-D joint inversions of RMT and CSAMT data carried out with EMILIA and MARE2DEM show clear improvement compared with 2-D single inversions, especially in imaging uncertain fracture zones analysed in a previous study. Our results show that boat-towed RMT and CSAMT data acquisition systems can be utilized for detailed 2-D or 3-D surveys to characterize near-surface structures underneath shallow water areas. Potential future applications may include geo-engineering, geohazard investigations and mineral exploration.

scholarly journals Analogy between electro-magnetic waves in cold unmagnetized plasma and shallow water inertio-gravity waves in geophysical systems

2021 ◽  
Author(s):  
E. Heifetz ◽  
L. R. M. Maas ◽  
J. Mak ◽  
I. Pomerantz
Keyword(s):  
Dispersion Relation ◽  
Shallow Water ◽  
Gravity Waves ◽  
Collisionless Plasma ◽  
Water System ◽  
Phase Speed ◽  
Rotating Shallow Water ◽  
Unmagnetized Plasma ◽  
Electro Magnetic ◽  
Magnetic Waves

Abstract The fundamental dispersion relation of transverse electro-magnetic waves in a cold collisionless plasma is formally equivalent to the two-dimensional dispersion relation of inertio-gravity waves in a rotating shallow water system, where the Coriolis frequency can be identified with the plasma frequency, and the shallow water gravity wave phase speed plays the role of the speed of light. Here we examine this equivalence and compare between the propagation wave mechanisms in these seemingly unrelated physical systems.

Exploring with Controlled Source Electro-Magnetic (CSEM) methods: from 2D profiling to 3D multi-azimuth surveying

2010 ◽  
Author(s):  
M. Darnet ◽  
P. Van Der Sman ◽  
R.E. Plessix ◽  
J.L. Johnson ◽  
M. Rosenquist
Keyword(s):  
Controlled Source ◽  
Electro Magnetic

Three methods for mitigating airwaves in shallow water marine controlled-source electromagnetic data

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. F89-F99 ◽  
Author(s):  
Jiuping Chen ◽  
David L. Alumbaugh
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Data Set ◽  
Oil And Gas Exploration ◽  
Controlled Source ◽  
Lateral Wave ◽  
Electromagnetic Data ◽  
Stripping Method ◽  
Resistivity Model

In the past several years, marine controlled-source electromagnetic (MCSEM) techniques have been applied successfully in deep water (depth > 1 km) for oil and gas exploration. The application of this technology in shallow water is challenged, however, because of “airwaves” that mask the signal from the target reservoir at depth. Based upon the understanding that an airwave is a lateral wave, which can be analytically expressed in a dual-half-space resistivity model, we propose three airwave-mitigation approaches to reduce the effects of these airwaves on MCSEM data. In the EM “x-bucking” approach, the effect of the airwaves can be “bucked” out from two measurements by using the analytic expression of the airwave. The frequency derivative (dE/dFreq) approach takes advantages of the unique characteristics of the airwaves in frequency domain, enhancing the reservoir signals while suppressing the airwave. The magnetotelluric (MT) stripping method uses the plane-wave feature of the airwaves and subtraction of the lateral wave electric component, which is obtained from measured marine MT impedance and controlled-source electromagnetics (CSEM) data, to generate a new data set in which the effects of the airwaves are removed substantially. By comparing the detectability, which is defined as the ratio of inline Ex fields between a reservoir model and a corresponding baseline model, for a reservoir target in deep water versus shallow water with a moderate 2D bathymetry, we show that the effects of the airwaves in shallow water can be reduced in the data, leading to greater reservoir detectability. In addition, these approaches have been applied successfully to a real shallow water MCSEM data set in which the detectability to the deeper resistive basement is enhanced.

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