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Woollybutt Field Management, Plug and Abandonment and Equipment Removal

Activity type Decommissioning, dismantling or removing a facility
Activity subtypes Drilling
Lifecycle Classification Decommissioning
Submitted by Eni Australia Limited
Submission date 06 October, 2016
Subtype Revision
Decision date 20 February, 2017
RMS ID 3697
Status Finalised
Outcome Accepted
Link to previously accepted EP 1996 - Woollybutt Field Management, Plug and Abandonment and Equipment Removal

Tom Coolican
Eni Australia Limited
226 Adelaide Terrace
Tel: +61 8 6320 2639

Location map (click to enlarge)
Location map - Activity: Woollybutt Decommissioning Project (refer to description)

The Woollybutt Field is located approximately 80 km off the northwest coast of Western Australia in Lease Area WA‐25‐L. The Field is approximately 25 km west of the Barrow Island Marine Management Area and Marine Park boundary, and more than 50 km south‐west of the proposed Montebello Commonwealth Island Marine reserve.
The Woollybutt Field is presently shut‐in and will continue to be shut‐in during field management activities. A summary of the proposed field management activities is outlined below.
1. Field Management Activities
Field management activities that may be undertaken in accordance with this EP include cathodic protection surveys and visual inspections, these are undertaken using remotely operated vehicles (ROV). The methods used by Eni are well understood and do not represent any novel techniques or equipment. Details of the frequencies and durations of field management activities are provided in Table 1.
Table 1: Proposed field management activities with indicative frequencies and durations



Approx. Duration (days)

ROV Survey

Opportunistic – no more than once per year

3 – 7 days

1.1 ROV Surveys
Cathodic protection surveys and visual inspections of subsea structures will be undertaken using ROVs, deployed from a project vessel. Cathodic protection surveys are undertaken as part of an asset integrity. Cathodic protection readings have remained consistent over the last three surveys conducted in 2010, 2014 and 2016.
1.2 Project Vessels
Project vessels will be selected based on the activity that will be undertaken. All project vessels will be commercial vessels with a suitable survey class for activities in the Operational Area. The maximum credible spill scenario for all project vessels is 100 m³ (volume of largest tank). All project vessels will run on marine diesel; no intermediate or heavy fuel oils will be used. Typical vessel specifications are detailed in Table 2.
Table 2: Typical vessel specifications



Draft (max)

3.25 (max)

Gross tonnage

1475 Gt


Steel hull

Fuel type

Marine diesel

Total fuel volume

138.2 m3 (100%)

Volume of largest fuel tank

30.4 m3

Other Details
Locations North West, Pilbara
Commonwealth waters adjacent to Western Australia
Titles (or other instruments) WA-25-L
Current Documents (Finalised)
EP Document

Decision notifications

Location map