Citation

Jones, A.T., Logan, G.A., Kennard, J.M., O'Brien, P.E., Rollet, N., Sexton, M. & Glenn, K.C., 2005. Geoscience Australia Survey 267, Post Survey Report: Testing Natural Hydrocarbon Seepage Detection Tools on the Yampi Shelf, Northwestern Australia. Record  2005/015. Geoscience Australia, Canberra.

Abstract

Geoscience Australia Marine Survey 267 was undertaken aboard the Parmelia K, a 28 m pearling boat out of Broome. The survey departed Darwin on 3 March 2004 and terminated in Broome on 18 March 2004. The length of the survey was curtailed by unfavourable weather conditions associated with tropical cyclones Evan and Fay. The aim of the survey was to test and validate a range of techniques used in the detection/identification of natural hydrocarbon seepage. The Yampi Shelf in the northern North West Shelf was selected for the test bed as it is a known region of intense and widespread hydrocarbon seepage. One of the most significant findings of the survey was the direct observation of natural hydrocarbon seepage in the Timor Sea region of the North West Shelf, which has previously only been interpreted through remote sensing or automated water sampling techniques (sniffer). Seepage plumes were observed rising from pockmark fields or hard-grounds on the vessel's echosounder and the side-scan sonar. Gas bubbles with oily films were observed at the surface. Active seepage sites were detected in close associated with hydrocarbon related diagenetic zones (HRDZs) interpreted in 3D seismic coverage of the region. A towed fluorometer detected variations in the hydrocarbon concentration of the sea surface over the study areas. Seepage appeared to be most active in association with low-tide, and more suppressed during high tide. Multi-beam swath bathymetry of the study areas revealed channels between 2 and 20 m deep on the Yampi Shelf headland and in the vicinity of the major HRDZs. Tidal current directions measured by an acoustic doppler current profiler (ADCP) in the Yampi Shelf headland channels suggests that tidal shears over this headland may be giving a response on Synthetic Aperture Radar (SAR). Sediment samples were collected with a Smith-Macintyre Grab, a dredge and a gravity core, although coring was largely unsuccessful due to carbonate hard-grounds over the seepage sites. Grab and dredge samples suggest that the active seeps are zones of preferential macro-biotic distribution. Significant down-time was introduced through poorly functioning equipment and a lack of experience on behalf of the staff. This was primarily due to the fact that some of the equipment was leased from Seismic Asia Pacific Ltd. Therefore it is recommended for future surveys that an operator be supplied with leased equipment, or that the equipment is purchased by Geoscience Australia and staff are appropriately trained before the survey. It is also highly recommended that the survey have seismic acquisition capability, as the seismic data proved to be the best proxy for seepage site location.
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Product Type/Sub Type

nonGeographicDataset - GA Publication - Record

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2005

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Record
marine survey
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-c371-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2004-11-15

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays