Now operating from two UK locations, Cirrus was formed in 1999 with a primary focus on the offshore sector and freshwater borehole-cleaning operations.

Director Craig Somerville says Cirrus has been using the AirBurst process for a few years now to rehabilitate, clean and develop water boreholes.

The company’s field of operations has been in France and the UAE, with some activity in the UK for Scottish Water, Anglian Water, Yorkshire Water and United Utilities. In France, Cirrus has worked on a number of radial wells in the Loire valley.

AirBurst Technology is a new, patented process that stimulates selected zones in a water well. A small volume of high-pressure inert gas is used to generate high-intensity ‘pressure pulses’ in the well. This pulses create high-frequency acoustic waves, which break up and remove mineral scales and
biofilm from the borehole wall or well screen.

The released gases create an air bubble that expands and collapses, and causes water to surge into and out of the formation adjacent to the tool. The expansion and collapse of the bubble produces an intense surging action that displaces fine sediment, mineral scale and biomass within the formation, and pulls the debris into the well bore.

Case study 1: Al Gharbia, UAE

Cirrus recently completed a project to rehabilitate boreholes in the UAE. Engineers for the Western Region Municipality revived three abandoned wells in Al Gharbia with AirBurst, reporting that it was a more effective alternative to solvents or explosives, while still at a fraction of the cost of drilling new wells.

While corrosive chemicals are still used elsewhere to unplug old wells, they can represent a danger to workers handling them. Newer, acid blends used for the job are less corrosive and non-polluting, but the Western Region Municipality wanted to find a chemical-free alternative.

Mr Somerville says the system works by firing acoustic waves and creating an explosion that “pushes water out at a fairly high velocity”. The residue is then pumped out so that the clean, fresh water below can be collected. He adds that the technology, based on offshore oil-drilling techniques, is used in hundreds of locations in the US, UK, Canada, France and Holland.

Cirrus estimates that the Emirates has about 70,000 boreholes in total. Mr Somerville says: “The UAE is one country that we’re interested in because the simple truth for Abu Dhabi is there are groundwater needs. If you’re using groundwater from a well, every week that you pump out you’re not actually getting those litres back in rainfall. Getting water benefits forestation projects, but you either have to spend a lot of money on desalination, which is not environmentally friendly, or look up better methods.”

Case study 2: Loire Valley, France

Cirrus was contacted by the operator of a water well field in the Loire Valley. The three wells in the field – St Maur 1, St Maur 2 and La Chesnaie – are of the radial or collector type. Cirrus worked on St Maur 1 a few years earlier, with good results.

St Maur 2 was to be a new project. La Chesnaie was of particular interest in that it had been taken out of production and replaced with a new well. This type of well poses a challenge in that it is impossible to gain access to the radial without draining the main chamber.

During routine ‘de-sanding’, all of the radial service valves are closed, the main chamber is drained and a high-volume service pump is installed. Once this pump is in place, a single radial is opened, and manual de-sanding and jetting can be performed. This process has been undertaken in all of the wells in this programme with a slight increase in production. However, based on previous work, it was felt that AirBurst would still yield a valuable improvement.

To undertake AirBurst in an efficient manner and minimise downtime, a modified approach was used that negated the need to drain the main chamber.

The main service valves were closed, as before, and a pump installed. The service valve for the radial to be treated was opened. A diver then inserted the AirBurst tooling and pushed it along the radial. Once the diver had surfaced, the service pump was activated and AirBurst operations commenced.

The treatment was repeated in the radial, as decided by the AirBurst operator.

For each well, the AirBurst process was used on day one. On day two, the additional material produced from AirBurst was removed by de-sanding. For the diving operations, a number of safety measures were implemented, from lock-out devices to back-up diver and safety-lift mechanisms. Full communications were maintained with the diver at all times during operation.

Slightly differing AirBurst techniques were used on each of the wells, and in all three cases good results were obtained. All works were undertaken in conjunction with local partner Bretagne Forage.