A marine electromagnetic survey to detect gas hydrate at Hydrate Ridge, Oregon

Weitemeyer, Karen; Constable, Steven; Tréhu, Anne M.

doi:10.1111/j.1365-246x.2011.05105.x

Cited by 84 publications

(40 citation statements)

References 75 publications

(107 reference statements)

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“…The comparison can be limited further to resistivities in areas of hydrate presence derived from CSEM studies only for a like-to-like comparison. Resistivities of 3-12 m in the Hikurangi Margin, offshore New Zealand (Schwalenberg et al 2010a), around 4 m in Porangahau Ridge, offshore New Zealand (Schwalenberg et al 2010b), 3-5 m in the Cascadia margin (Schwalenberg et al 2005), and no greater than 5 m for the Hydrate Ridge (Weitemeyer et al 2006b(Weitemeyer et al , 2011 were reported, which are comparable to the values of resistivity reported here. These sites, however, were all in deeper water, with a more distal sediment supply without any glaciogenic component.…”

Section: Interpretation Of Resistivity Modelssupporting

confidence: 75%

“…The use of marine CSEM for hydrate detection was first suggested by Edwards (1997) and has been successful in various academic studies (e.g. Schwalenberg et al 2005;Weitemeyer et al 2006a;Schwalenberg et al 2010a,b;Weitemeyer & Constable 2010;Weitemeyer et al 2011;Goswami et al 2015;Attias et al 2016). It was also used commercially in Japan for hydrate exploration (referenced within Constable et al (2016)).…”

Section: Introductionmentioning

confidence: 99%

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Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

Goswami¹,

Weitemeyer

Minshull³

et al. 2016

Geophys. J. Int.

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S U M M A R YThe Arctic continental margin contains large amounts of methane in the form of methane hydrates. The west Svalbard continental slope is an area where active methane seeps have been reported near the landward limit of the hydrate stability zone. The presence of bottom simulating reflectors (BSRs) on seismic reflection data in water depths greater than 600 m suggests the presence of free gas beneath gas hydrates in the area. Resistivity obtained from marine controlled source electromagnetic (CSEM) data provides a useful complement to seismic methods for detecting shallow hydrate and gas as they are more resistive than surrounding water saturated sediments. We acquired two CSEM lines in the west Svalbard continental slope, extending from the edge of the continental shelf (250 m water depth) to water depths of around 800 m. High resistivities (5-12 m) observed above the BSR support the presence of gas hydrate in water depths greater than 600 m. High resistivities (3-4 m) at 390-600 m water depth also suggest possible hydrate occurrence within the gas hydrate stability zone (GHSZ) of the continental slope. In addition, high resistivities (4-8 m) landward of the GHSZ are coincident with high-amplitude reflectors and low velocities reported in seismic data that indicate the likely presence of free gas. Pore space saturation estimates using a connectivity equation suggest 20-50 per cent hydrate within the lower slope sediments and less than 12 per cent within the upper slope sediments. A free gas zone beneath the GHSZ (10-20 per cent gas saturation) is connected to the high free gas saturated (10-45 per cent) area at the edge of the continental shelf, where most of the seeps are observed. This evidence supports the presence of lateral free gas migration beneath the GHSZ towards the continental shelf.

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Section: Interpretation Of Resistivity Modelssupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

Goswami¹,

Weitemeyer

Minshull³

et al. 2016

Geophys. J. Int.

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“…Here, we demonstrated that by using various synthetic inversions we were able to determine both the horizontal and depth sensitivity of the inversions, as well as distinguish between real resistive anomalies and those that are artefacts which appear beneath the CNEO3 pockmark. The magnitude of the main resistivity anomaly (>3 Ωm) beneath CNE03 that emerged from our inversions is consistent with the magnitudes found in other gas hydrate exploration studies (Schwalenberg et al 2005(Schwalenberg et al , 2010Weitemeyer et al 2011;Sun et al 2012).…”

Section: 1supporting

confidence: 79%

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

et al. 2016

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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.

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“…The recent upsurge in mCSEM applications for hydrocarbon exploration has led to intensive research and knowledge generation, including insights from synthetic studies (Weiss and Constable, 2006;Um and Alumbaugh, 2007;Commer and Newman, 2008;Sasaki and Meju, 2009) as well as real data inversions (e.g., Newman et al, 2010;Schwalenberg et al, 2010;Li et al, 2011;Weitemeyer et al, 2011;Súilleabháin et al, 2012). Whereas the physics of the method is the same for surveys on land, inversion of land CSEM data poses several challenges not equally encountered in mCSEM.…”

Section: Introductionmentioning

confidence: 99%

3D inversion and resolution analysis of land-based CSEM data from the Ketzin CO2 storage formation

2014

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We evaluated 3D inversion of land controlled-source electromagnetic (CSEM) data collected across the Ketzin CO 2 storage formation. A newly developed, parallel and distributed 3D inversion code, which is based on a direct forward solver, has been used. This inversion scheme allowed us to calculate the Jacobian matrix explicitly within a reasonable time and use it to calculate regularization parameters, inspect survey coverage, and carry out resolution analysis. After demonstrating that the magnetic field components are sensitive to conductors only, whereas the electric field components are sensitive to all features of interest, we continued to work with electric field data only. Estimates of data uncertainty obtained from robust processing were used for automated data preselection and weighting during inversion. We tested different regularization techniques and a range of starting models to explore the model space and assess the influence of regularization on the inversion images. We further demonstrated an approach for handling numerical singularities due to sources located inside the inversion domain. We estimated survey coverage, horizontal and vertical resolution, and depth penetration using cumulative sensitivity, point spread functions, and depth-resolution plots. Based on data fit analysis, we determined a preferred subsurface conductivity model, which we compared to an independent regional structural geologic model, and we provided an interpretation for the structures resolved. The inversion approach we used provides robust results in good agreement with known geology, offers new possibilities for model assessment, and should be transferable to other CSEM data sets.

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A marine electromagnetic survey to detect gas hydrate at Hydrate Ridge, Oregon

Cited by 84 publications

References 75 publications

Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

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

3D inversion and resolution analysis of land-based CSEM data from the Ketzin CO2 storage formation

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