Big bore boosts Angel production

June 10, 2010

In October 2008, 37 years after its discovery, the Angel field began producing to a not-normally manned platform. In the ensuing 18 months, this platform offshore Western Australia has seen 98% uptime. Jennifer Pallanich discusses the A$1.6 billion development of this field – the third platform of the North West Shelf Venture fields to begin production – and a few others in the region, such as Pluto, with operator Woodside.

When it came to designing a not-normally manned platform to be located 50km away from its control center – in this case, the North Rankin A platform in 125m of water – it was necessary to minimize complexity.


‘Our challenge was to challenge everything in, rather than challenge everything out,' says Eamonn McCabe, Woodside's VP oil & gas development/ projects. In other words, if a piece of equipment was going to hold its spot on the Angel platform, its merit had to be well defined, with no simpler way to accomplish the same task existing. Every design item was calculated to reduce maintenance costs and/or time. ‘We challenged the heck out of everything.'

One example McCabe likes to give is the drainage system. During the design phase, one of the operators asked why it was necessary to have the drains, suggesting instead a solution of using hoses to accomplish the same task in a different fashion.

‘A lot of people said: "You won't get it not-normally manned, but it's a great aspiration",' McCabe says. Indeed, the facility is now operating unmanned and is the largest gas processing platform of its kind in Australia. Woodside believes it is also the most complex, highest production, glycol dehydration notnormally manned facility in the world; it uses state-of-the-art environmental monitoring.


Essentially, says Feisal Ahmed, EVP, project development, the design was based on ‘if you were able to do it in an ideal world, what would it look like?' He adds the engineers had free reign to deliver the safest and most operable platform possible. There was no preconceived design.

The final platform is a simple one, but it took a lot of engineering to get there. Angel's processing facility has no power generation, seawater, firewater, no winch (lifeboat freefalls), permanent bulk diesel storage, emergency generator, subsea manifolding of flowlines, subsea umbilical distribution units, or regulator banks in the subsea hydraulic power unit.

The topsides, manufactured by Malaysia Marine Heavy Engineering, weigh in at 7500t. Chiwan Sembawang Engineering in China fabricated the 8000t jacket. The platform can handle two-phase, or dry, export. It has a self-extinguishing helideck and features new oil-in-water and water-incondensate technology analyzers for remote monitoring. The platform can accommodate three flowlines and three umbilicals for future tie-back projects.

Prysmian in Italy manufactured the power and fiber optics cable – a first for Australia.

The operations and project teams worked closely together to design the facility, which McCabe calls a key to the success of the platform. ‘It was a textbook project,' Ahmed says. To date, the Angel platform has had 98% uptime, and Woodside had targeted 96% uptime. ‘If you look at the success of Angel, compared to some of the other projects, you'd be hard-pressed to see what you'd do differently,' he adds.

The facility is remotely powered and operated from the North Rankin A platform. In fact, McCabe adds, Woodside modified the North Rankin A control room to operate Angel without having to shut down activity at North Rankin A. ‘That took a mindset change in the engineering and design for this platform,' McCabe says. Transfield Worley handled modifications at North Rankin A.

Those modifications include relocation and upgrade of the control room, relocation of telecom equipment, extension of the J tube to support installation of the submarine power and fiber optic cable to Angel, a new power transformer, and modification of the high-voltage switchboard and electrical tie-in for Angel power.

Another highlight of the project, according to the company, is the largest hot tap of its kind being carried out to tie in the Angel pipeline to the export line to the Karratha gas plant. The hot tap was carried out without disrupting supply from North Rankin A, and it was the first subsea tap in Australia. It tied in the 30in export pipeline from Angel into the trunkline to the Karratha gas plant.

When Angel went onstream in 2008, it was the year before the NWS Venture – operated by Woodside on behalf of partners BHP Billiton, BP, Chevron, Japan Australia LNG, and Shell – celebrated the silver anniversary of production.

‘The surprising, interesting fact is Angel has the capacity to produce 1bcf/d from three big bore wells,' Ahmed says. The field in 80m of water was producing at a rate of 800mmcf/d and 50,000b/d of condensate, and the whole North West Shelf Venture was producing about 3bcf/d of gas, 140,000b/d of condensate and 40,000b/d of oil.

A factor in Angel's high production rate, he says, is big bore technology. The nature of Angel's reservoirs at 3000m below the seabed meant that to maximize production, a high flowrate and large bore system were required. It's one of the first fields on which Woodside opted to use the technology, and the Aussie operator worked closely with FMC to make it happen. The system involved vertical christmas trees, a barrier in the vertical bore for greater well integrity at a high flow rate, and a separately retrievable module with a choke valve. Hydrates and sand management become flow assurance issues in big bore scenarios, according to Woodside. Mitigation techniques were selected on a case-by-case basis.

No injection is currently planned at Angel at this time, the company says.

Aside from the uptime and the safety factor, Woodside has seen some other benefits from the not-normally manned approach.

‘The implications? That many fewer helicopter rides, that many fewer changes of crew, the cost aspect of it, efficiency and safety,' Ahmed says. By taking the not-normally manned approach at Angel, Woodside anticipates saving operations expenditures of $110 million over the life of the field.

The list goes on, including sustainability and operability. The project was also carried out on time and under budget. It requires only 5500 planned maintenance hours per year with visits by crew of up to 16 every six weeks.

Given the success with Angel, it's natural that Woodside would consider even more ambitious projects.

‘We want not-normally manned TLPs or spars on Browse,' McCabe says about one of the projects the operator is about two years away from sanction on. A major lure to the not-normally manned design is that they're ‘inherently safe,' McCabe adds.

On the LNG train

The company has seen quite a bit of growth.

Formed in 1954, Woodside initially focused on exploring oil off Australia's south coast. A series of discoveries off the Western Australian coast in the 1970s changed the company's focus. Today, Woodside's LNG equity output is just below 3mtpa, and the company aims to reach 20mpta of equity production by 2017. To reach that level, Woodside is relying not just on its operated North West Shelf Venture project but also a series of other LNG projects that are expected to come online in the next seven years.

The North West Shelf Venture – the project that pinned Western Australia and Woodside to the global gas map – so far has three producing platforms: North Rankin A online since 1984, Goodwyn A in 1995, and Angel 13 years later.

The venture has other projects under way, including a new platform with compression facilities, the North Rankin B topsides (which will weigh in at 23,000t and are under construction at the Hyundai Heavy Industries yard in Ulsan, Korea) and jacket (under construction at the McDermott yard in Batam, Indonesia), and a replacement FPSO for the Cossack Pioneer.

The former FSO Okha is under conversion at Keppel's yard in Singapore and is due to begin production by year's end at the Cossack, Wanea, Lambert and Hermes fields. The North Rankin B effort alone extends the life of the North Rankin and Perseus fields to 2040 under an A$5 billion project, Ahmed says.

The Pluto LNG project is targeted to produce first gas from the field by the end of this year and to produce first LNG in early 2011.

The Pluto platform is in 85m of water. This year, it will see quite a bit of activity as hook-up and completion activities are carried out. Once it's online, however, it too will function as a not-normally manned facility.

Woodside took on an ambitious schedule for this field, taking it from discovery to first gas in five years. This is ‘unheard of for a greenfield LNG project,' Ahmed says. That's an approach the operator plans to use again. Woodside awarded the front end engineering and design contracts for the Pluto LNG expansion, Trains 2 and 3 late last year.

The Browse project is in the basis-ofdesign phase, and the company expects to make a final investment decision in June 2012. Right now, it appears Woodside will develop the three fields in the area with dry tree units such as TLPs tied back to a central processing facility with a jacket and topsides on the shelf in 100m water depth with multiple onshore and LNG processing trains. Woodside aims to have Browse ready for start up in 2017.

Another highlight on the Woodside horizon is the Greater Western Flank gas project, which contemplates the development of up to 14 fields in water depths of around 100m.

At this point, Woodside is leaning toward tying the fields back to the Goodwyn A platform on the North West Shelf and potentially bringing in an FPSO to handle the oil. The project is in concept selection phase, so there's still a bit of time for the operator to finalize project details.


For Sunrise in the Timor Sea, where water depths range from 100m to over 600m, Woodside said it expects a JV decision shortly on whether it would pursue development through an FPSO with an LNG gas train at the existing plant in Darwin or through floating LNG. Given the extensive amount of work done to date and a preliminary field development plan approval in 2010, the field is expected to begin production in 2017. ‘That's quite a long piece of work that we've already started on,' McCabe says.

With such a list of projects lined up, it's impossible not to consider the human resource challenge that Woodside must be facing to pull it all off.

Ahmed says the company uses three main methods to build up personnel: home grow the talent, hire contractors and hire externally.

A bonus, McCabe says, is that many people want to work on the world-class projects Woodside is behind. He sees the stream of projects as a way to continue building up the company's capability. ‘The team from the Pluto pipeline project have moved on to the Browse project to determine the optimal design of the gas pipeline,' McCabe points out. The expectation, he adds, is that a team will roll from one project to another, learning and refining methods along the way. ‘We're growing together.'

For now, the industry itself is in a major growth mode in the Western Australia region.

‘It's a breath of fresh air to be involved in nothing but growth,' says Ahmed, whose 34 years in the oil & gas business include many years when the cyclical industry was in the doldrums.

‘It's nice to be on the building end as opposed to the reduction end.' OE



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