Photo: Barossa field; Source: Santos

Santos preparing for Barossa drilling and completions campaign

Australian energy giant Santos has filed its environmental plan with the country’s authorities for the development drilling and completion of wells on the Barossa gas field development off Australia.

The Santos-operated Barossa gas field is located 300 kilometres offshore Darwin in Australia. The development will backfill gas supply to the existing Darwin LNG facility at Wickham Point. Santos NA Barossa, as the operator, on behalf of co-venturers SK E&S Australia and Santos Offshore, is currently executing the development, with the first gas production targeted for the first half of 2025.

Barossa map - Santos
Barossa map; Source: Santos

The Barossa development was accepted by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) in March 2018. As part of the approved development, Santos is planning to start the development drilling and well completions campaign within Commonwealth petroleum production licence NT/L1 in 2Q 2022. The campaign will continue on a 24-hour basis until completed.

The ‘operational area’ encompasses the entire petroleum production licence. Water depths over the operational area range from approximately 204 m to 376 m. The operational area is approximately 33 km from the Oceanic Shoals Australian Marine Park.

The Barossa environmental plan (EP) identifies and evaluates credible environmental impacts and risks associated with the drilling and completions campaign and ongoing management of the completed wells.

According to the EP, six subsea production wells are planned to be drilled and completed around the future locations of three subsea production manifolds, with two wellheads adjacent to each manifold. If required, up to two contingency production wells could be drilled and completed at any manifold (eight wells in total).

The Barossa EP provides for drilling and completing the wells using a semi-submersible mobile offshore drilling unit (MODU) and light well intervention (LWI) vessel, and the ongoing management of the complete wells until future commissioning and production phases.

Activities included in this EP are the movement of the MODU within the operational area, MODU and vessel commissioning and demobilising activities, deployment and recovery of the MODU anchors and mooring lines, drilling operations, and well completions, including perforating and well flowback.

Furthermore, the activities include the installation of Christmas trees, contingency activities such as side-track drilling, re-drilling sections, re-spud and abandonment, well intervention, ongoing well inspection, maintenance and management, and general operations associated with the use of a MODU, vessels, helicopters and remotely operated vehicles (ROVs) within the operational area.

A petroleum safety zone will extend in a 500-m radius around the MODU surface location (at each drill centre) and completed subsea well location. During drilling activities at Barossa, a cautionary zone will be placed around the MODU and anchors which may extend up to 2.5 km from the MODU.

This EP will remain valid from the date that it is accepted by NOPSEMA, until 31 December 2025.

The Barossa will be developed with an FPSO with a processing capacity for up to 800 million standard cubic feet per day (MMSCFD) of gas and design capacity of 11,000 barrels per day of stabilised condensate. BW Offshore will deliver the FPSO under a contract awarded in March 2021 worth about $4.6 billion. The project was sanctioned later that month.

BW has already completed the $1.15 billion project debt financing for the construction and operation of the Barossa FPSO and entered into a partnership with international global infrastructure investors for the equity financing of the vessel.