A NEW project is under way that aims to develop a downhole pump based on the principles of magnetic levitation.
The work is being undertaken by Norwegian company Ziebel, which recently secured operating company support for its innovative proposal technology with the help of the Aberdeen-based Industry Technology Facilitator (ITF).
The pump is targeted at gas well de-liquification. As gas reservoirs are produced and the pressure declines, the gas velocity decreases.
At a critical point, the gas velocity will no longer be able to lift all entrained liquids to surface. Therefore the liquids will accumulate in the wellbore.
If this accumulation is allowed to develop, the liquid will eventually form a “plug” which interferes with production, resulting in lost gas production and, ultimately, reduced recovery.
According to ITF, the “MagLev” pump therefore has the potential to deliver increased gas recovery from a field by pumping out the liquids which would otherwise plug the well and stop production of the valuable gas.
In the past, the principles of magnetic levitation have been used in a wide range of applications, including thruster motors on ships and high-speed train development, where magnetic forces have been used to suspend, guide and propel the trains,
This downhole pump technology uses permanent magnet technology to drive linear actuators/pistons.
“For those that are familiar with existing downhole artificial lift technology, you could think of ‘MagLev’ as an advanced piston pump being driven by a downhole motor using latest permanent magnet machine technology,” says project director Iain Maclean.
“Field trials for gas well dewatering are planned for 2009 and we are also working on several additional applications and have filed patents for subsea well retrofit solutions with downhole safety-valve requirements.”
The permanent magnet technology apparently offers some key advantages, including high power efficiency and high volumetric efficiency, which can enable smaller size pumps to be placed deeper into the wellbores and also have the ability for the pump to be economically retrievable – that is, recover to surface without pulling the production tubing.
Maclean says: “Perhaps when compared to a typical North Sea oil producer, the increased recovery from each gas well is relatively small.
“However, when you also consider the huge numbers of gas wells, the total increased recovery is very significant.
“In the US alone, there are about 70,000 gas wells greater than 1,524m (5,000ft) deep. Closer to home, in the Southern North Sea, there are several hundred offshore gas wells. Many of these are now starting to encounter liquid loading problems. This is what makes the ‘MagLev’ downhole pump such an interesting solution.”
According to ITF’s technology manager, David Liddle, this is a good example of proven technology being adapted and developed for oil&gas industry use.
The proposal was submitted in response to a call for proposals on the theme of production efficiency – which, along with increased recovery and maximisation of available resources, remains one of the underlying drivers for all the work ITF does. As far as Liddle is concerned, the “MagLev” project clearly has the potential to fulfil all of these objectives.