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Scarborough gas field is located approximately 270km north-west of Onslow in the Carnarvon Basin in the Northwestern Shelf, offshore Western Australia.
The field lies in the WA-1-R license in water depths of 900m to 1,500m.
The WA-1-R license was previously owned by ExxonMobil subsidiary Esso Australia Resources (50%), BHP Billiton (25%) and Woodside Petroleum (25%).
Woodside acquired ExxonMobil’s 50% interest in the license in March 2018.
The license is now owned by Woodside (75%) and BHP Billiton (25%).
A final investment decision for the proposed development of the Scarborough gas field is expected to be made by 2020. The gas field is expected to achieve first gas by 2023.
Scarborough gas field discovery, geology and reserves
The Scarborough field was discovered by the Scarborough-1 well, which was originally drilled in 1979 at a water depth of around 900m.The field is a simple anticlinal structure located at depths of approximately 1,800m and contains 7.3 trillion cubic feet of natural gas reserves.
Its reservoir comprises high-quality gas accumulated in the Barrow Group Flag sandstone of the Zeepaard Formation.
The gas contained within the field is classified as ‘sweet’, without traces of hydrogen sulphide and only trace levels of carbon dioxide.
The field’s reserves are considered to be one of the most remote gas resources in the Carnarvon Basin.
Appraisal drilling on the Scarborough gas field
A seismic survey of the field was completed in 1996, which covered an area of 2,440km².
The survey was conducted before the commencement of the appraisal well drilling programme.
The first appraisal well to be established at the field was known as Scarborough-2 and was drilled in June 1996 to a total depth of 2,068m.
BHP Billiton carried out a 3D seismic survey spanning 912km² at the field in 2004, which was followed by a three-well appraisal drilling programme that began in December the same year.
The appraisal drilling was conducted until early 2005 and involved the drilling of three appraisal wells named Scarborough-3, Scarborough-4A and Scarborough-5.
Wells were plugged and abandoned before being tested and data was subsequently collected.
Scarborough gas field project development details
The plan for the development of the Scarborough field includes the drilling of 12 daisy-chained subsea gas wells, which will be tied-back to a semisubmersible platform moored in 900m of water.
A total of seven horizontal and high-angle wells are planned to be drilled at a depth of 2,500m as part of the initial phase of development.
The gas field will be developed using a floating production unit (FPU), which will comprise of topside with a production capacity of up to 9t a year installed over the semi-submersible hull.
The natural gas processing unit installed on the topside of the FPU will include gas separation, dehydration and compression along with Mono Ethylene glycol (MEG) regeneration and water handling systems.
Onshore development details
Processed gas from the platform will be transported via a 430km-long carbon steel pipeline to the onshore existing Pluto liquefied natural gas (LNG) facility located on the Burrup Peninsula covering an area of 80ha.
Pluto LNG facility, operated by Woodside, was commissioned in 2012. It comprises a single LNG processing train and possesses at a production rate of approximately 4.9 million tonnes per annum (Mtpa).
Woodside is undertaking the expansion of the Pluto LNG facility by adding the second LNG train with a capacity of 5Mtpa.
The new LNG train will process natural gas sourced from the Scarborough offshore facility. Commencement of the LNG train operations is planned for 2024.
Ocean Infinity was contracted by Woodside to provide deepwater geophysical survey data for the Scarborough offshore field development.
Wood was awarded a contract by Woodside in August 2018, for supporting the execution of concept definition related to the FPU, sea umbilicals, risers and flowlines, flow assurance and associated equipment for the Scarborough gas field development project.
McDermott was awarded the front-end engineering and design (FEED) contract for the FPU, which is set to be installed at the Scarborough project, in February 2019.
Woodside awarded a FEED contract to Bechtel for the second train at Pluto LNG facility associated with the Scarborough project in December 2018.
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