North Sea Production Solutions for a Low Oil Price Era

North Sea Production Solutions for a Low Oil Price Era
Rigzone takes a look at a handful of engineering solutions designed to make marginal fields economic in a low oil price era.

The decline in the price of crude oil threatens to bring about the cancellation of many energy projects around the world. In regions where labor is expensive and oil exists in harsh conditions, such as the North Sea, around a third of currently-producing fields are uncommercial below $50 per barrel let alone at the current price of around $30 per barrel.

However, plenty of innovative minds in the oil and gas industry are looking at new ways to produce from currently uneconomic oil reserves. Here, we take a look at a few companies that are targeting their technology and know-how at marginal oilfields.

ABT's Production Buoy and NU-SIFT Solutions

ABT Oil & Gas is a UK firm based in Manchester and Aberdeen that sees opportunities in the North Sea for the development of marginal fields that have so far been ignored by operators who use traditional production systems. As well as being able to transform the value of undeveloped marginal fields, ABT reckons it can also boost the value of late life fields via redevelopment using its low-cost capital expenditures (CAPEX) and operational production (OPEX) production solutions.

ABT has two solutions it has been working on with a consortium of partners that are designed to make marginal fields economic. The first is a "Production Buoy" that is designed to be operated as a normally-unattended facility, with oil stored in a subsea tank and offloaded to an export tanker. It is tethered to a concrete gravity base that rests on the seabed. The tethered buoy is an inherently stable structure and can withstand very harsh weather conditions while undergoing the minimum of surge movements with almost no pitch or heave, according to the company.

Most of the equipment used by the Production Buoy is housed with a buoyance chamber below the surface, with topside structure, access tower and helideck located above the surface. ABT notes that using the buoyancy chamber in this way allows for a smaller structure and protects equipment against the elements. Process equipment within the chamber is connected to subsea wellheads via flexible risers and umbilicals.

Well fluids are processed in the buoyancy chamber, with water separated and either reinjected or treated and disposed of into the sea, while associated gas is used for power and heat generation. Produced oil is then stored in a seabed storage tank, andoil is offloaded using a seawater displacement system.

ABT's second solution is NU-SIFT, which stands for Normally Unattended Self Installing Fixed Tower. This is designed to be a low-cost production and storage facility that combines the benefits of a floating production storage and offloading vessel (FPSO), such as oil storage and the ability to redeploy it, with the benefits of a fixed platform (e.g. platform-based wells and the ability to operate unattended).

The NU-SIFT facility can process the produced liquids, separating the water before treating it and either reinjecting it into the well or disposing it overboard. It can also use produced gas as a fuel to power itself. Produced oil can be stored within the facility up to a capacity of at least 100,000 barrels or it can be exported by pipeline.

So far, ABT Oil & Gas is involved in a handful of projects in the North Sea and offshore Ireland that may end up using its marginal field solutions. The Fyne field, located on UK license P077 in the central North Sea, holds some 300 million-plus barrels of oil with wells drilled there previously flowing at up to 4,000 barrels of oil per day (bopd) in tests, while the Phoenix reservoir (also located in the central North Sea) is on trend with the producing Forties, Montrose and Nelson fields. Over in Ireland, wells on the Helvick and Dunmore fields in the North Celtic Sea Basin have flowed at 9,900 bopd and 2,100 respectively.

Dynamically Positioned FPSO

Aberdeen-based Amplus Energy Services is working with French oilfield services giant Technip S.A. to develop its dynamically-positioned FPSO concept that works at 4,000-to-5,000 bopd production in a $50 per barrel environment, according to the firm's managing director.

North Sea Production Solutions for a Low Oil Price Era
Aberdeen-based Amplus is developing a dynamically-positioned FPSO concept to bring down the cost of oil production in the North Sea.
Source: Amplus

Speaking to Rigzone in early January, Ian Herd said:

"Conventional FPSOs in the North Sea all have a mooring system, which is anchors and chains and other things to hold them to the seabed. And that, for an operator, will generally cost you somewhere between $30 million and $50 million of CAPEX for the mooring system alone – depending where it is and how deep the water is.

"We don't have any of that. We used dynamic positioning, which has been on the go for over 30 years now."

Herd explained that his company is well-suited to develop the concept, given that it is already a specialist in dynamic positioning, having used the technology in subsea vessels. Dynamic positioning in FPSO promises lots of advantages, according to Herd.

"You cut out a lot of the subsea architecture and the flowlines can be reduced. We can sit right above the well, more or less, whereas conventional FPSOs are generally sat a fair way off. This is because the moving parts that they have would then have to be looked at in conjunction with a potentially moving pattern for drilling rigs to get in to do any drilling work that was needed in the well," Herd said.

"So, we've got much lower upfront CAPEX. We can site much closer, so our subsea architecture costs are reduced. And at the end, of course, decommissioning costs are significantly reduced as well. So it's a much lower cost solution for the operator."

With oil at $30 per barrel, Herd recognizes that operating in the North Sea "is tough for everyone no matter who you are" but he points out that Amplus' production solution "is much lower cost than any conventional FPSO or platform".

The next step is to get a dynamic FPSO built. So far, the company has gone a long way down the road with two North Sea clients, according to Herd, while it has also had interest from other parts of the world.

"We thought when we started off that we'd be focused on the North Sea originally, but we also have people talking to us about Angola, Brazil, the Gulf of Mexico and Mexico itself... I thought when we started we'd predominantly focus on the small fields and the small reservoirs here, but we're getting a lot of interest in our ship for long-term early production in some of these more deepwater areas," Herd said.

"They like the idea of our ship being out there for a year or two, in order to see what the reservoirs are actually doing and then they will decide where the permanent facility is going to be, whether that's a million-barrel FPSO or a platform, and we'll stay there producing while they build their permanent facility. So it gets them early cash flow, it gets them some reservoir understanding and it generally gives them a much better place to make their final investment decision."

Wintershall's 'Minimum Facility' Platform

One company that is already operating an unmanned mini-platform in the North Sea is Wintershall. Although this facility is designed for gas production, the German firm believes that its so-called "Minimum Facility" platform – which was built in just nine months – could be one of the smallest topsides in an oil and gas application.

North Sea Production Solutions for a Low Oil Price Era
Wintershall believes its L6-B mini-platform, currently operating in the Dutch North Sea, has one of the smallest topsides in an oil and gas application worldwide.
Source: Wintershall

Anchored to the seabed through suction piles, the facility rises about 60 feet above the Dutch North Sea and has three decks. Its substructure weighs 1,100 tons, with the topside weighing 100 tons; other platforms in the vicinity weigh as much as 4,500 tons. It can accommodate a maximum of two producing wells, with a pipeline transporting gas produced at the well to a neighboring platform.

There is only minimum processing equipment on the platform, so the expected visit frequency is low, according to Wintershall.


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