Geohazards and fluid seepage assessment on the mad dog field using bathymetry, ultra-high-resolution seismic and satellite seepage slick data

NRG Cope, M Huuse

    Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

    Abstract

    This paper reports an environmental assessment of the geohazards and seep phenomena of the Mad Dog field area of the Gulf of Mexico. The Mad Dog block, centered on US GOM block GC782, is located on the Sigsbee Escarpment in the Green Canyon region of the Gulf of Mexico, approximately 310 km south of New Orleans. The study area covers approximately 120 km2 and extends to water depths of 1300 m - 2170 m. The available data included a deep-tow multibeam bathymetry and ultra-high-resolution 2D seismic grid in combination with satellite seepage slick interpretations from the greater Mad Dog area. Hydrocarbon seep phenomena and SAR slick data were cross-examined to determine a relationship; however although some large slicks had been mapped by SAR in the project area, the slick density was lower than anticipated and correlation to sea-bed manifestations was not always well defined. The seabed displayed substantial relief and steep gradients across a salt-related graben structure in the northwest, associated with several potential gas-related seismic wipeout features, and scarps in the central survey area. Substantial geohazards occur in the escarpment region with slope gradients up to 28 degrees and abundant evidence for mass transport deposits. The presence of strong currents that run parallel to the base of the escarpment at up to 1 ms-1 (Bryant et al. 2000) form mega furrows. Associated erosional processes in this current could mask seep phenomena and therefore be lost during bathymetry and subsurface analysis. Eight possible seep structures were observed in the region and one coned shaped mound interpreted as a mud/asphalt volcano. When correlating the locations to SAR slick data it was hard to conclusively establish a relationship between seeps and slicks due to the unknown currents. In order to reduce the uncertainty of slick and seep correlations, sea current data at various depths throughout the water column would be needed at the time of SAR capture, and access to any seafloor cores would help ground truth interpreted seepage phenomena. A better understanding of the plumbing system can only be gained from examining deeper-penetration 3D seismic data that was unavailable for this study. Copyright 2014, Offshore Technology Conference.
    Original languageEnglish
    Title of host publicationhost publication
    Pages1326-1353
    Number of pages28
    Volume2
    Publication statusPublished - May 2014
    EventSEG - New Orleans
    Duration: 1 Jan 1824 → …
    http://www.scopus.com/inward/record.url?eid=2-s2.0-84945191060&partnerID=40&md5=49d6a264df665003677338d677a0191d

    Conference

    ConferenceSEG
    CityNew Orleans
    Period1/01/24 → …
    Internet address

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