Shell Australia secures approval to develop the Crux gas field in the Browse Basin
The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has accepted an Offshore Project Proposal (OPP) from Shell Australia to develop the Crux gas field in the Browse Basin, off the north coast of Western Australia.

Consisting of a platform and five production wells, the proposed Crux development would connect to the Prelude Floating Liquefied Natural Gas (FLNG) facility via a 165km export pipeline.

Today’s announcement follows a thorough and careful assessment process of almost two years. In line with statutory timeframes, this has included a public comment process and consideration of all feedback.

The Crux development is subject to further regulatory approvals prior to proceeding, including an accepted environment plan, a well operations management plan and facility safety case. All required regulatory approvals must be in place before activity can begin.

A statement of reasons and final OPP document will be published by NOPSEMA within 10 days of the acceptance decision, in accordance with the regulatory requirements.

Map source: NOPSEMA

Project description

Shell Australia Pty Ltd (Shell), together with joint venture partners Seven Group Holdings Energy and Osaka Gas, are progressing plans for the prospective development of the Crux gas field, located approximately 160 kilometres north-east of the Prelude field in the northern Browse Basin, offshore Western Australia. The Crux field is located in Commonwealth waters in the northern Browse Basin, 190 kilometres offshore north-west Australia and 620 kilometres north-north-east of Broome.

The Crux project has been identified as the primary source of backfill gas supply to the Prelude Floating Liquefied Natural Gas (FLNG) facility. The proposed Crux project consists of a not normally manned (NNM) platform in water depths of approximately 165 metres of water; with five production wells, minimal processing and utility systems, tied back to the existing Prelude FLNG facility via a 165 kilometre export pipeline. Crux will be operated remotely from the Prelude FLNG facility. Front-end engineering and design for the project is expected to commence in 2019 with the financial investment decision (FID) currently scheduled to occur in 2020. The project is anticipated to have a 20-year design life. However, subject to the future investment decisions, the project may extend.

The current project concept comprises:

• a NNM platform, which includes dry trees, processing facilities and associated utility systems
• five production wells with subsea wellhead system tied back through rigid concentric tubulars to the NNM platform and completed with dry trees 
• a 26-inch export pipeline, approximately 165 km long, which ties the platform back to the Prelude FLNG facility, and
• subsea integration system connecting the export pipeline system with Crux platform and the Prelude FLNG facility, comprising risers, subsea isolation facilities, pipeline inspection gauge receiver and associated control systems.

There is also a potential for future subsea developments that will provide hydrocarbons to the Crux platform. These developments are expected to comprise subsea production wells, completed with subsea trees, and associated subsea tie-back to the platform (e.g. flowlines, risers and manifolds).

From FID it will take approximately four to five years for the platform to be fully designed, constructed off-site and towed to location. Whilst the platform is being built, the subsea production wells would be drilled and suspended until installation of the platform facilities, after which the wells would be completed, hooked-up to the platform and brought online. Decommissioning will be undertaken at the end of field operations.

The key execution stages of the project are:

• development drilling, including tie-back and dry tree completion
• installation of the platform jacket and topsides 
• installation and hook up of export pipeline and subsea integration system to the platform facilities 
• commissioning 
• operations and maintenance (note, this includes any future subsea tie-back developments within the in-field development area), and 
• decommissioning.

Additional gas reservoirs within the in-field development area may be tied back to the Crux platform. The development of these reservoirs will broadly involve the same key stages and activities as those used in the development of the Crux field, with the exception of completion with subsea trees.

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