Azimuth decomposition of SBL data

Maaø, Frank A.; Johnstad, S.E.; Gabrielsen, Pål T.; Panzner, Martin

doi:10.1190/1.2792484

Cited by 8 publications

(7 citation statements)

References 3 publications

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“…The effect of resistive targets on the field values is subtle in the MCSEM method. In order to make that effect more apparent it is customary to show the field magnitudes normalized by the data from a reference receiver, which supposedly is in a position where there is no influence of the resistive target (Røsten et al, 2003;Johnstad et al, 2005;Maaø et al, 2007). In theoretical studies this normalization is made with field values calculated for a model with a homogeneous earth.…”

Section: Resultsmentioning

confidence: 99%

Influence of sea water resistivity on MCSEM data

Luz

Régis

2007

10th International Congress of the Brazilian Geophysical Society &Amp; EXPOGEF 2007, Rio De Janeiro, Brazil, 19-23 November 200

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ABSTRACT. The Marine Controlled Source ElectroMagnetic (MCSEM) method is a geophysical tool for the detection of resistive targets in the subsurface of the oceanic floor. In this work we model MCSEM data in one-dimensional environments, including variations in the resistivity of the ocean water, as horizontal layers of uniform resistivity. Such variations can arise from the influence of marine currents, temperature gradients or any other source of influence on the water salinity.We study the effect of such variations on the MCSEM data. Our results show that the interpretation can be strongly influenced, especially for normalized data. We see that changes in the water resistivity have a similar effect on the data as changes in the water depth, and that both affect the attenuation of the so called "air-wave".Keywords: MCSEM, modeling, sea water resistivity. RESUMO. O Marine Controlled Source ElectroMagnetic (MCSEM)é um método geofísico para a detecção de camadas resistivas contidas abaixo do assoalhooceânico. Neste trabalho nós modelamos os dados do MCSEM em um ambiente unidimensional, incluindo variações na resistividade daágua do mar, na forma de camadas de resistividades uniformes. Estas variações na resistividade daágua podem surgir devidoà influência de correntes marinhas, gradientes de temperatura ou mudança na salinidade daágua. Nós estudamos o efeito destas variações nos dados do método MCSEM. Nossos resultados mostram que a interpretação pode ser fortemente influenciada, principalmente quando são analisados os dados normalizados. Vimos que as mudanças na resistividade daágua têm um efeito sobre os dados similaràquele de mudanças na profundidade da lâmina d'água, sendo que ambos influenciam na atenuação da chamada "air-wave".Palavras-chave: MCSEM, modelagem, resistividade daágua do mar.

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Section: Resultsmentioning

confidence: 99%

Influence of sea water resistivity on MCSEM data

Luz

Régis

2007

10th International Congress of the Brazilian Geophysical Society &Amp; EXPOGEF 2007, Rio De Janeiro, Brazil, 19-23 November 200

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“…The processing included an approximate up-down wavefield decomposition [9] and azimuth processing [10].…”

Section: Data Processingmentioning

confidence: 99%

Application of Electromagnetic Scanning to an Australian Frontier Basin with Complex Bathymetry

David¹,

Ross²,

Roth³

et al. 2008

Proceedings of Offshore Technology Conference

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“…Decomposition of the CSEM response into radial and azimuthal components assumes a plane layer earth model (Maaø et al 2007). However, this assumption can be violated in azimuth decomposition for attribute analysis when the azimuth angle, θ, is less than 45° (Maaø et al 2007). Broadside data with short source‐receiver offsets, giving high azimuth angles (>45°) and smaller radial field components, are not comparable with the in‐line data.…”

Section: Azimuth Decompositionmentioning

confidence: 99%

Controlled source electromagnetic three‐dimensional grid‐modelling based on a complex resistivity structure of the seafloor: effects of acquisition parameters and geometry of multi‐layered resistors

Bhuyian

Thrane

Landrø

et al. 2010

Geophysical Prospecting

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A comprehensive controlled source electromagnetic (CSEM) modelling study, based on complex resistivity structures in a deep marine geological setting, is conducted. The study demonstrates the effects of acquisition parameters and multi‐layered resistors on CSEM responses. Three‐dimensional (3D) finite difference time domain (FDTD) grid‐modelling is used for CSEM sensitivity analysis. Interpolation of normalized CSEM responses provides attributes representing relative sensitivity of the modelled structures. Modelling results show that fine grid, 1 × 1 km receiver spacing, provides good correlations between CSEM responses and the modelled structures, irrespective of source orientation. The resolution of CSEM attributes decreases for receiver spacing >2 × 2 km, when using only in‐line data. Broadside data in the grid geometry increase data density by 100 – approximately 200% by filling in in‐line responses and improve the resolution of CSEM attributes. Optimized source orientation (i.e., oblique to the strike of an elongated resistor) improves the structural definition of the CSEM anomalies for coarse‐grid geometries (receiver spacing ≥3 × 3 km). The study also shows that a multi‐resistor anomaly is not simply the summation but a cumulative response with mutual interference between constituent resistors. The combined response of constituent resistors is approximately 50% higher than the cumulative response of the multi‐resistor for 0.5 Hz at 4000 m offset. A gradual inverse variation of offset and frequency allows differentiation of CSEM anomalies for multi‐layered resistors. Similar frequency‐offset variations for laterally persistent high‐resistivity facies show visual continuity with varying geometric expressions. 3D grid‐modelling is an effective and adequate tool for CSEM survey design and sensitivity analysis.

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Azimuth decomposition of SBL data

Cited by 8 publications

References 3 publications

Influence of sea water resistivity on MCSEM data

Influence of sea water resistivity on MCSEM data

Application of Electromagnetic Scanning to an Australian Frontier Basin with Complex Bathymetry

Controlled source electromagnetic three‐dimensional grid‐modelling based on a complex resistivity structure of the seafloor: effects of acquisition parameters and geometry of multi‐layered resistors

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