EP Summary Fugro Geophysical Technical Gorgon Expansion

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    Gorgon Gas Development Fourth Train Expansion Project, Geophysical and Geotechnical Site Survey   Page 1  Environment Plan Public Summary

    GEOPHYSICAL AND GEOTECHNICAL SITE SURVEY GORGON GAS DEVELOPMENT FOURTH TRAIN EXPANSION PROJECT

    ENVIRONMENT PLAN: PUBLIC SUMMARY

    This summary of the Environment Plan for the Gorgon Gas Development Fourth Train Expansion Project Geophysical and Geotechnical Site Survey, which will be acquired on the North West Shelf (NWS) offshore from Western Australia (WA), has been submitted to the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA), to comply with Regulations 11(7) and 11(8) of the Offshore Petroleum and Greenhouse Gas Storage (Environment) Regulations 2009.

    INTRODUCTION

    The geophysical and geotechnical survey company Fugro Survey Pty Ltd proposes to undertake a geophysical and geotechnical site survey (Geophysical and Geotechnical Site Survey, Gorgon Gas Development Fourth Train Expansion Project), on the NWS offshore from WA. The proposed geophysical and geotechnical site survey comprise both shallow and deep water components in Commonwealth waters offshore from Barrow Island (Figure 1), and will be conducted to support marine aspects of Chevron’s Gorgon Gas Development Fourth Train Expansion Project. The key objective of the site survey is to gather sufficient geophysical and geotechnical information to provide Chevron with detailed data for the design and location of subsea structures and pipelines.

    The geophysical and geotechnical site survey is scheduled to occur in the period between November 2012 and April 2013, with expected durations of approximately eight weeks for the geophysical fieldwork and 12 weeks for the geotechnical fieldwork.

    COORDINATES OF THE PROPOSED ACTIVITY

    The proposed geophysical and geotechnical site survey will take place within a number of areas associatedwith the Gorgon Gas Development Fourth Train Expansion Project in Commonwealth waters on the NWS, offshore from Barrow Island, WA. This will include both shallow water (water depth range 25-200 m) and deep-water (water depth range 200-1,397 m) components (Figure 1). Data acquisition will take place in an operational area that covers ~7,180 km

    2 , which overlaps parts of 35 petroleum titles. Boundary coordinates

    for the operational area polygon, which encompasses all of the proposed site survey areas (Figure 2), are provided in Table 1 below.

    Table 1: Geophysical and geotechnical site survey operational area  – boundary coordinates

    Point Latitude (S) Longitude (E)

    Degrees Minutes Seconds Degrees Minutes Seconds

     A 19 46 36.01 114 05 02.95 B 19 46 36.01 114 02 09.59

    C 19 32 46.39 114 03 12.34

    D 19 31 09.25 114 07 14.08

    E 19 30 38.22 114 10 55.72

    F 19 35 21.82 114 30 04.17

    G 19 58 10.57 115 11 22.77

    H 20 40 14.11 115 20 56.38

    I 20 41 58.54 115 12 26.84

    J 20 38 13.24 115 07 28.03

    K 20 11 18.58 114 41 20.16 Datum: WGS84

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    Gorgon Gas Development Fourth Train Expansion Project, Geophysical and Geotechnical Site Survey   Page 2   Environment Plan Public Summary

    Figure 1: Location map  – geophysical and geotechnical site survey, Gorgon Gas Development Fourth Train Expansion Project

     At the closest point (Point H  –  see Figure 1), the geophysical and geotechnical site operational area is

    situated at a minimum distance of approximately 1.2 km from the WA State waters boundary, and approximately 7.3 km from the west coast of Barrow Island. All components of the operational area are located in Commonwealth waters. At the closest point, the inshore components of the operational area

    located approximately 6.5 km from the northern boundary of the Barrow Island Marine Park, and approximately 1.2 km from the boundary of the Barrow Island Marine Management Area. Water depths in the operational area range from ~25-1,397 m. There are no emergent features or shallow shoals or banks within the operational area (Figure 1).

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    Gorgon Gas Development Fourth Train Expansion Project, Geophysical and Geotechnical Site Survey   Page 3  Environment Plan Public Summary

    Figure 2: Geophysical and geotechnical survey components

    DESCRIPTION OF THE PROPOSED ACTIVITY

    The geophysical and geotechnical site survey is scheduled to occur in the period between November 2012 and April 2013, with expected durations of approximately eight weeks for the geophysical fieldwork and 12 weeks for the geotechnical fieldwork. Timing of commencement of the geophysical and geotechnical fieldwork is dependent on fair sea state conditions suitable for data acquisition, the availability of the survey vessel for conducting the survey, and granting of approvals from the appropriate government bodies.

    The site survey proposed is a typical geophysical and geotechnical survey similar to most others conducted in Australian marine waters (in terms of technical methods and procedures). No unique or unusual equipment or operations are proposed.

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    Gorgon Gas Development Fourth Train Expansion Project, Geophysical and Geotechnical Site Survey   Page 4  Environment Plan Public Summary

    Geophysical Component The geophysical site survey will use both vessel-based and autonomous underwater vehicle (AUV)-based survey sensors (multi-beam echo sounder, sub-bottom profiler; sidescan sonar) to acquire and process data to provide the following:

      Bathymetry: Accurate bathymetry (water depth measurements) via the acquisition of echo sounder and multi-beam echo-sounder data in conjunction with speed or sound in water measurements.

      Seabed topography: Multi-beam bathymetry data will provide a topographic map over the operational area outlining areas of differing water depth.

      Seabed heterogeneity: o  side scan sonar data will be used to determine areas of the seabed with contrasting acoustic

    properties that relate to different seabed sediment composition, sedimentary features and rock outcrops; and

    o  such features often are associated with changes in seabed depth and so the multi-beam derived topographic map will be used to augment interpretation.

      Seabed/shallow sub-surface mechanical properties: Sediment samples acquired via drop core or grab-sampler are required to ‘ground-truth’ the various seabed sediment types identified by the side -

    scan sonar to understand the nature of contrasting seabed types.   Seabed obstruction/contact map: The side scan sonar will locate any significant seabed anomaly

    present within the operational area such as geological features or manmade debris.

      To map the shallow subsurface geology: The chirp and boomer or sparker sub-bottom profiling systems will identify any subsurface geological feature that may provide impediments to proposed construction activities. Maps will be created to chart the location of these features.

    Geotechnical Component The purpose of the geotechnical site survey is to gather sufficient site-specific geotechnical data for the design and installation of subsea production equipment (wellheads, manifolds, umbilicals, flowlines, export pipelines) during the front end engineering design (FEED) phase of the Gorgon Gas Development Fourth Train Expansion Project. The geotechnical site survey will incorporate: cone penetration testing; T-bar testing; drilling and sampling; rock coring; piston coring; and box coring.

    The work scope for the geotechnical site survey is divided into two operations: shallow geotechnical investigation; and deep geotechnical investigation. Both field investigations will be performed from a dedicated geotechnical survey vessel.

    The shallow geotechnical investigation encompasses all of the pipeline routes locations as well as the geohazard study and a portion of the scarp crossing. The deep geotechnical investigation encompasses the piezo cone penetrometers tests (PCPT) and boreholes up to 40 m below the seabed at the subsea structure locations, pipeline crossings and scarp crossing.

    Survey Vessel Fugro proposes to conduct the geophysical and geotechnical site survey using a purpose-built geotechnical survey vessel, the MV Fugro Synergy , which is a dynamically positioned (DP), multi-purpose drilling, well

    intervention and geotechnical vessel. The Fugro Synergy  has all necessary certification/registration and is fully compliant with all relevant MARPOL and SOLAS convention requirements for a vessel of this size and purpose, including a Shipboard Oil Pollution Emergency Plan (SOPEP) in accordance with Regulation 37 of

     Annex I of MARPOL 73/78. During the survey, the Fugro Synergy  will be refuelled in port in Dampier. No at sea refuelling will take place during the survey. All crew changes and resupply of the vessel will take place in port.

    DESCRIPTION OF THE RECEIVING ENVIRONMENT

    The operational area for the proposed geophysical and geotechnical site survey is located in the Carnarvon Basin on the NWS (Figures 1 and 2), approximately 150 km west of Dampier. The NWS is scattered with islands, the largest of which is Barrow Island. The operational area is situated within the North-west Marine Region (NWMR), and overlaps parts of three key ecological fe