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A new enhanced oil recovery concept: wind powered water injection

14 August 2014

DNV GL is proposing a new concept that combines mature water injection technology with the newest developments in offshore wind power to achieve more cost effective Enhanced Oil Recovery (EOR). Initial studies show it will reduce the cost of water injection, avoid costly topside modifications and reduce greenhouse gas emissions.

International classification and consultancy group DNV GL has carried out studies to suggest there are opportunities for a new generation of autonomous injection systems to increase reservoir pressure using a wind-powered water injection system which could reduce both CAPEX and OPEX and drive innovation of new technology. It could be installed without costly retro-fittings on the platform, provide access to systems normally located subsea, increase the flexibility of injection location and reduce the installation time. The system would also be possible easy to move and use at new locations after the closure of a well or field.

DNV GL’s concept involves the integration of the compressor and water treatment equipment into the sub-structure of a floating wind turbine. These have recently emerged as one of the most interesting sources for offshore power generation, allowing relatively stable production and flexibility regarding locations and water depths.

The technical feasibility of floating wind turbines wasfirst proven with the successful deployment of Statoil’s Hywind in 2009 followed by Principle Power’s WindFloat a few years later. Arrays of up to five units are being planned for the near future, with advanced concept development carried out in the US, Europe and Japan.

Any of the three main types (spar-buoy, semi-submersible and TLP) would be feasible, with designs modified to accommodate storage systems,additional tank spaces and additional control systems as required.

Power from the floating wind turbines can be used with a variety of water injection technologies, ranging from raw seawater injection as the simplest to LowSal water injection (low salinity water from a reverse osmosis process) as the most complex.

In recent years several successful raw seawater injection systems have been implemented and new subsea water treatment technologies are under development, enhancing the methodologies and techniques used.

High-level indicators of economic and technical performance show an interesting window of opportunity for applications that can tolerate unprocessed seawater for injection in oil fields.

The simplest use case considered is powering a subsea pump with a local, offshore floating wind turbine to inject unprocessed seawater into an oil reservoir. Recent experience on a subsea water injection project on the Norwegian shelf has demonstrated the technical viability of injecting unprocessed seawater into an oil reservoir with suitable properties. Further, successful floating wind turbine demonstration projects have proven this new technology’s feasibility.

In the conventional solution for a subsea injection manifold, the costs associated with connecting a subsea power cable to the host platform, where the electrical power for the subsea injection pump is generated, can be substantial. Under the right circumstances and conditions, it may be possible to reduce costs significantly by powering the subsea pump with one or two offshore wind turbines that are placed in close vicinity (in the order of hundreds of metres) of the subsea manifold.

The reduced costs of this solution are enabled by the shorter subsea power cable, the elimination of incremental power generation on the host platform and, in the case of Norway, reduced taxes related to the incremental emissions of natural-gas turbine power generation for the subsea injection pump.

Christian Markussen, Subsea Business Development Leader at DNV GL Oil & Gas, said: “Our studies show that such a stand-alone system could quickly become cost competitive with traditional solutions for injection wells far from the platform, and even more when one considers retrofitting water injection equipment into an existing facility and coping with the disruptions that this modification can have on production. Operators can obtain a new and cost-efficient way to develop marginal reservoirs and enhance production in mature fields.”

He said the financial benefits would vary depending on factors such as the reservoir characteristics and step-out distance from the production well. Traditional injection systems normally have a significant CAPEX investment, CO2 tax, and exposure to fuel costs, and could therefore provide a substantial incentive for assessing alternative solutions.

No major technical barriers to the concept were uncovered in DNV GL’s high-level study. The main concerns related to system availability and operational challenges are considered to be manageable.

Johan Sandberg, Service Line Leader, Offshore Renewable Energy at DNV GL, said: “We want to take this concept further together with both the wind energy and O&G industries and invite them to participate in a Joint Industry Project (JIP) to carry out an in-depth study. The combination of the two technologies can open up an era of synergies and mutual benefit for both industries. I see this as an important part of the oil & gas industry’s work to reduce cost, with lower emissions as a positive effect.”

DNV GL presented a paper at OTC 2014 in Houston, Texas, which  highlights the technical and economic feasibility of wind powered subsea water injection. To access the paper, click on the link below.

 


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