A Marine Survey to Investigate Seal Integrity Between Potential CO2 Storage Reservoirs and Seafloor in the Caswell Sub-basin, Browse Basin, Western Australia - Grain size and carbonate concentrations of seabed sediment.  

Authors / CoAuthors

Howard, F.J.F.

Abstract

Geoscience Australia (GA) conducted a marine survey (GA0345/GA0346/TAN1411) of the north-eastern Browse Basin (Caswell Sub-basin) between 9 October and 9 November 2014 to acquire seabed and shallow geological information to support an assessment of the CO2 storage potential of the basin. The survey, undertaken as part of the Department of Industry and Science's National CO2 Infrastructure Plan (NCIP), aimed to identify and characterise indicators of natural hydrocarbon or fluid seepage that may indicate compromised seal integrity in the region. The data collected during this survey complement sequence stratigraphic studies in the Caswell Sub-basin that provide constraints on the most suitable areas for storage of CO2 and help to identify potential CO2 storage reservoirs. The results of this work are published in GA Record, Geocat 83120. The survey was conducted in three legs aboard the New Zealand research vessel RV Tangaroa, and included scientists and technical staff from GA, the NZ National Institute of Water and Atmospheric Research Ltd. (NIWA) and Fugro Survey Pty Ltd. Pre-survey site selection was informed by mapping fault networks and potential fluid-flow pathways connecting the regional seal to the seabed over interpreted CO2 storage play fairways and through interpretation of associated amplitude anomalies in 2D and 3D seismic data. Shipboard data (survey ID GA0345) collected included multibeam sonar bathymetry and backscatter over 12 areas (A1, A2, A3, A4, A6b, A7, A8, B1, C1, C2b, F1, M1) totalling 455 km2 in water depths ranging from 90 - 430 m, and 611 km of sub-bottom profile lines. Seabed samples were collected from 48 stations and included 99 Smith-McIntyre grabs and 41 piston cores. An Autonomous Underwater Vehicle (AUV) (survey ID GA0346) collected higher-resolution multibeam sonar bathymetry and backscatter data, totalling 7.7 km2, along with 71 line km of side scan sonar, underwater camera and sub-bottom profile data. Eighteen Remotely Operated Vehicle (ROV) missions collected 31 hours of underwater video, eight grabs and one core. Shipboard and AUV multibeam bathymetry and sub-bottom profiler data indicated the presence of recently active faults in the area, some with significant seafloor surface expression (i.e. fault scarps with up to 40m offset). Some of these faults were visually inspected by the ROV which also confirmed the presence of diverse biological communities. Possible indications of shallow gas were observed on sub-bottom profiles, including amplitude anomalies, cross-cutting reflectors and zones of signal starvation. Water column observations including sidescan sonar, single-beam and multibeam echosounders, underwater video and photography did not conclusively identify hydrocarbon or other fluid seepage. Strong currents encountered during parts of the survey may have interfered with the direct detection of seeps in the water column. While no active signs of seepage were observed, the geochemical and biological sampling undertaken will aid in baseline environmental investigations for this region. This catalogue entry refers to grain size data and carbonate concentrations of the upper ~2cm of seabed sediment. Sediment samples were first wet sieved to determine the proportions of mud, sand and gravel as a percentage. By wet sieving fine particles are removed from the sand and gravel fractions, allowing an accurate measurement each component. The grain size of the mud fraction (<63 m) was determined using a Mastersizer laser granulometer. Sediment > 63 um diameter were dried, and dry sieved at values between 4 and -4 phi corresponding to the Wentworth (1922) grain size boundaries between the major sediment classes. The samples were then submitted for measurement of carbonate content by mass using the carbonate digestion method described in Müller and Gastner (1971).

Product Type

dataset

eCat Id

89712

Contact for the resource

Keywords

• Data Package

( Theme )

• Exclusive Economic Zone

( Theme )

• sedimentology

( Theme )

• marine survey

( Theme )

• geological storage of CO2

( Theme )

• marine environmental baselines

• Australian EEZ

Australian and New Zealand Standard Research Classification (ANZSRC)

• Marine Geoscience

• Published_Internal

Publication Date

2015-01-01T00:00:00

Creation Date

Security Constraints

Australian Government Security ClassificationSystem    

Classification - unclassified

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Creative Commons Attribution 4.0 International Licence    

Access - license

Use - license

Status

Purpose

Maintenance Information

asNeeded

Topic Category

oceans

Series Information

Lineage

Version 1

Parent Information

Extents

[-14.29, -12.8678, 122.39, 124.6521]

Reference System

Spatial Resolution

Service Information

Associations

Downloads and Links

Source Information

Dataset collected in WGS84. Source extent for the metadata recod however is GDA94 to be consistent with other source extnets of GA products 122.3883 124.6521 -14.2865 -12.8678