IN DEPTH TECHTALK: Floating wind-powered water injection

DNV GL-led WIN WIN joint industry project (JIP) results indicate that, especially for marginal oil & gas fields supplying production to a major field, floating wind-powered water injection is technically feasible in general. This specific application is claimed to offer an excellent business case too. A major contributing factor favouring the positive overall outcomes is the elimination of water flow lines. These are otherwise required in a conventional water injection setup for connecting to the main big reservoir of oil or gas platforms.

Operating experience with floating wind turbines is still limited to five full-scale single prototypes, but substantial advances have been made, especially in recent years. The first floating project commissioned in 2009 is Statoil’s 2.3MW Hywind Demo off the Norwegian coast, followed by Principle Power’s 2MW WindFloat in Portugal during 2011. Next came two 2MW floating Japanese turbines installed in 2013. The world’s biggest floating wind installation today, featuring a 7MW Mitsubishi turbine, was commissioned in 2015 off the coast of Japan near Fukushima.

Oil recovery

Water injection is a standard process used widely in industry as a highly effective means of increasing oil recovery from offshore reservoirs. Three barrels of sea water is the global volume for every barrel of oil produced. For specific fields the actual figure can vary greatly and is typically much more towards late-life of fields, and the consequence is high (fossil) power consumption and a costly physical infrastructure. Some other key statistics and industry facts in DNV GL’s WIN WIN report released in May this year are that one-third of the global oil and gas production originates from offshore fields. Water injection can increase reservoir recovery rates by up to 50 per cent, which could boost global oil production worth USD 500 million on a daily basis.

Are Kaspersen is the project manager for DNV GL’s WIN WIN (WINd-powered Water INjection) project. He said on the project background that the initial idea originated from DNV’s 150-year anniversary in 2014: “All divisions of the (current) DNV GL group developed a vision for the future. We focused on floating offshore wind power, and the idea of matching the competence, resources and need of the competence, resources and need of the oil industry with wind power was explored, resulting in the WIN WIN concept.”

Next, internal DNV GL experts assessed whether decentralised use of wind power could become a viable cost-effective alternative water injection method for increasing oil recovery from especially marginal offshore reservoirs. These small reservoirs are commonly located at 20 – 30 kilometres distance from main oil & gas platforms pumping oil or gas from big reservoirs, and their production flow lines feed to the main platform. If water injection is used in a marginal field as part of a conventional setup, water flow lines of roughly the same length are required too. Power to main platforms is typically supplied by gas engine generating sets.

Meeting requirements

To develop the concept further and in making sure that the concept met the industry’s need, DNV GL invited the industry to assess technical and economic feasibility in a join industry project.

The efforts led to the formation of a dedicated JlP team comprising seven participants from both the renewable and oil and gas industries led by DNV GL. The WIN WIN feasibility study commenced in early 2015, with a main focus at assessing the feasibility of the concept of using floating wind turbines to power a water injection system in detail, including technical and operational aspects as well as capital expenditure (CAPEX) and operational expenditure (OPEX). The JIP partners include oil and/or gas / energy companies ExxonMobil, ENI Norge, Nexen Petroleum UK Ltd., Statoil, and VNG Norge. The two additional partners are Norwegian pump specialist PG Flow Solutions, and UK-based technology innovation and research centre for offshore wind ORE Catapult.

Neither major challenges nor serious ‘show stoppers’ have been identified through the JIP study, said Kaspersen, and within this context he called oil platforms inherently complex and WIN WIN in comparison rather uncomplicated. He added that analyses of system performance examining site specific cases brought in by JIP partners showed that WIN WIN is indeed capable of meeting the operator’s key performance requirements. This includes specific operational and other issues such as injection volume targets, as well as reliability and minimized downtime.

Energy intensive

Kaspersen: “A main challenge using wind power for offshore oil and gas operations is the intermittent power supply. This makes water injection, a major power consumer, an ideal match for wind power, since water injection can tolerate variations in power supply, as long as the required volumes are injected over time.”

WIN WIN can be built using any proven floating wind turbine concept but the initial main focus from the onset was on Statoil’s Hywind concept. This is essentially a standard offshore turbine placed on a Statoil-owned ballasted spar type steel substructure anchored to the seabed. Because of the operational experience, Kaspersen considers Hywind and WindFloat to be the most mature concepts available. However, he keeps a keen eye at other developments too and does not exclude alternative options.

In the off-grid (not electrically connected to a central electricity network) autonomous WIN WIN system, the upper part of the spar foundation also serves as a platform for the water injection system. This system uses filtered seawater, which is pumped up using lift pumps, and injected into the reservoir with the aid of positive displacement injection pumps. An incorporated electric micro grid enables a controlled start-up and shutdown of the system, and ensures that power demand matches power supply during operation. A battery pack ensures power supply to critical safety and communication functions during periods of no wind, and communication with the main (host) platform is enabled through a satellite link.

Cost reduction

A January 2016 Statoil presentation quotes for the 2.3MW Hywind Demo a cumulative production of 50GWh since September 2009, with an overall capacity factor of 41.4 per cent. A 30MW Hywind Pilot Park planned for commissioning in Q4 2017 off the Scottish coast will comprise five Siemens 6MW turbines and an up-scaled substructure design. The new design was at the Global Offshore Wind conference in Manchester quoted as offering 60 – 70 per cent cost reduction per megawatt compared to the initial Hywind Demo.

“Supplying clean power to oil & gas installations was part of the original idea behind Statoil’s Hywind concept”, said Hanne Wigum, Head of Renewable Technology Development at Statoil: “The WIN WIN concept represents an alternative source of electricity and has the potential to open up new opportunities for field development.” She added that the costs for wind powered water injection have been compared with a conventional alternative where water is injected via a flow line from the host platform. While the WIN WIN technology has higher OPEX compared to a conventional alternative, the significantly lower ow27-8-1CAPEX means that it compares favourably over the long term. WIN WIN is therefore a commercially competitive alternative in a range of cases, particularly when host platform capacity is limited or injection wells are located far away.

Elaborating on optimal turbine size, Kaspersen said that a 6 – 7MW base case matches well with typical 2 – 8MW electric power demand for driving water injection pumps and auxiliary equipment in marginal fields. He in parallel prefers some degree of turbine ‘oversizing’ for improving overall system performance by reducing variability in turbine output.

Modest

According to Kaspersen, the main focus of the project is access from the host platform. He added: “Access to the WIN WIN system for maintenance is assumed to be done by mobilizing service personnel and crew transfer vessels from the host platform. Alternatives could be to mobilize service personnel onshore, which is mainly an alternative if the WIN WIN system is located in proximity to shore, or to have service agreements with other offshore wind farms in the area if possible. On the implementation potential for WIN WIN installations he said that there are at the moment about 600 water injection wells in the Norwegian North Sea, and 20 – 30 new wells are drilled each year. This works out to potentially five to ten new WIN WIN installations annually.

Kaspersen also called for caution: “Making any such estimates is tricky, since this is highly case dependent, and reservoir data are generally highly confidential and not shared openly in the industry.”

To develop the WIN WIN concept further, a next envisaged step would be to test critical subsystems in a small-scale laboratory physical setup. The key objective is to gain assurance that components integrated in this configuration will offer satisfactory performance over time and by accepting variable power input.

Kaspersen: “DNV GL currently explores a possible next phase of the project together with some of our current JIP-partners. Potential pilots are also being discussed with the industry, but the ownership to such projects will have to come from the industry partners themselves. We hope to see a WIN WIN pilot by 2020, and we know that there are industry players who are keen on moving this even faster forward.”

Stand-alone

The WIN WIN project focuses on a stand-alone system for wind-powered water injection. Two main options were found particularly attractive from a business perspective said Kaspersen: “The first is tie-backs from marginal fields where WIN WIN saves the cost of water flowlines, and secondly cases where WIN WIN is an alternative to modifications and/or retrofitting of existing platforms to expand the water injection capacity. In that case WIN WIN saves the modification costs, and these are generally high. DNV GL further considers a wider expanded use of the technology.”

Perspectives

Meanwhile, various JIP partners already offered different views and perspectives on the future potential and the role of wind in oil and gas exploration.

“We are encouraged by recent advances in wind technology, particularly for niche applications such as offshore oil and gas operations,” said for instance Sara Ortwein, President of ExxonMobil Upstream Research Company. “Such technological advances improve the economic feasibility for wind to contribute to the overall energy supply mix.”

Remi Eriksen, Group President and CEO of DNV GL remarked finally: “For the first time we can now see renewable energy as a large scale source of power to offshore oil & gas operations. By utilising the recent developments of floating offshore wind turbines this concept can offer a clean, reliable, and cost effective alternative for powering water injection in offshore locations. The WIN WIN project showcases that the oil and gas industry can become a creative force in solving the world’s energy trilemma by driving development of reliable, clean and affordable technologies. This is a win for both the oil and gas and for the wind power industries.”

 

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