The Tordis Improved Oil Recovery (IOR) system, which was commissioned by Statoil, is the world's first full field subsea separation boosting and injection system. It is at the cutting edge of design and technology and owes much of its success to the strong working partnership between FMC Technologies and Tracerco, part of the Johnson Matthey Group.
The collaboration has resulted in an impressive subsea separation monitoring system that combines Tracerco's separator measurement experience with FMC Technologies' knowledge of subsea process design and project execution.
In 2005 Statoil contracted FMC Technologies to deliver a full-field separation facility to enable reinjection of bulk water into a non-hydrocarbon reservoir and send hydrocarbons through a multi-phase pump back to the Gullfaks C platform. By installing a full-field subsea separation facility, Statoil expects to improve the Tordis Field's recovery factor from 49% to 55%. Along with other upgrades to the field, FMC's separation system will allow Statoil to extract roughly 35 MMbbl extra from the Tordis Field.
Six of Tracerco's state-of-the-art separator level measurement instruments are central to the project and are being used in the separator and desander vessels. The company has more than 40 years experience in developing innovative specialist measurement solutions and has redesigned its successful topside TRACERCO Profiler unit to cope with the unique subsea environment.
Andy Hurst, managing director at Tracerco said: "This is a hugely exciting project and we are delighted to be involved. During the next decade, subsea separating techniques will be used more and more as operators try to make the most of hydrocarbon reserves. The Tordis project will not only make this activity more viable but also sets the industry standard for this type of activity. Through subsea separating technology, energy firms will have the opportunity to maximise well returns and ensure the longevity of field life. "We have been working with FMC Technologies for the last five years to develop a measurement system that can provide the most accurate image of the internal separator vessel available on the market. When we took on the project we knew in theory that the technology would not be a problem but the environmental conditions gave us a steep learning curve to turn theory into practice".
The Profiler works by giving a density profile of the cross section of the vessel and then gives a visual interpretation of the data much in the same way an MRI scanner would provide a slice of a human body, essentially giving the operator "insight onsite". The scan of the vessel provides a range of data that can be interpreted to identify the oil / water interface and any emulsion / foaming layers that may be forming.
The unit is based on gamma radiation measurement principle, using long-term stable Geiger-Muller detectors and consists of a number of density measurement detectors, installed vertically inside the separator vessel. The measured change in density – the process profile – is presented graphically to the operator. The measured interface levels from Digital Control System (DCS) input for separator control and shutdown, including foam, liquid, emulsion, water and sand levels. The information provided by the subsea profile gives engineers the most accurate vision of the density patterns in the vessel and helps maximise efficiency. During qualification for the subsea use through FMC Technologies, the system underwent thorough testing and reliability analysis.
The Tordis field is located in block 34/7 of the Tampen area in the Norwegian North Sea The IRO system was installed last month (September) and will be fully commissioned imminently.
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