Jadestone Energy (Eagle) Pty Ltd (Jadestone Energy) plans to remove three wellheads, Montara-1, 2 and 3 from the Montara Field which lies approximately 690 km (373 nautical miles) east of Darwin in a water depth of approximately 80 m. The Montara Field was discovered in 1988 with the drilling of the exploration well Montara-1, and later appraised with the drilling of appraisal wells Montara-2 and Montara-3, in 1991 and 2002, respectively. The wells were suspended with annual monitoring undertaken by remotely operated vehicle (ROV).
In 2021, both the primary and secondary barrier envelopes were verified, and the wells confirmed to be plugged and abandoned as per the NOPSEMA accepted Well Operations Management Plan (WOMP) (accepted on 22/06/21). A final abandonment report was submitted to NOPSEMA for these wells in September 2021.
This EP provides for the removal of three wellheads: Montara-1, -2 and -3 within production Licence AC/L7. It includes for remote operated vehicle (ROV) activities such as “as found” and “as left” surveys, marine growth removal and wellhead area preparation. Jadestone have included multiple methodologies for the wellhead removal activity to allow for vessels and tools of opportunity over the validity of this EP: Abrasive Water Jet Cutting (AWJC), external cutting using diamond wire saw (DWS) or equivalent and mechanical internal cutting.
The duration of the activity at each wellhead is expected to be approximately 2 days, however, to allow for mobilisation and demobilisation of the vessel and unforeseen delays due to weather or equipment (for example), an allowance of approximately 14 days has been provided including mobilization, seabed surveys, wellhead removal and demobilization. One vessel is required to complete this activity with the capacity to recover the subsea infrastructure to deck. The dismantling and disposal of the wellheads is anticipated to be completed within 12 months of arrival at the receiving port and waste management facility. The wellhead composition is predominantly mild steel and it is anticipated that most of each wellhead and associated is able to be recycled or repurposed.
Wellhead removal will be subject to the availability of a suitable vessel, and wherever feasible will be a vessel of opportunity that is mobilising to the Montara field for other activities. Therefore, the exact timing of the wellhead removal is unknown. Removal activities may be undertaken any time during the life of the EP which is 5 years from acceptance.
