Subsurface Technologies Incorporated (STI)

- Water Well Cleaning & Restoration Technology


Over time, it is very common for water wells to experience lost capacity as well as a variety of water quality problems requiring some form of well rehabilitation. Most of these problems are a result of fouling material becoming deposited on the surfaces (rock surfaces, gravel pack, well screen) in water environments. Once these deposits become significant,  wells and aquifers will experience lost capacity and water quality changes like discoloration, taste and odor problems as well as 'unsafe' (Total Coliform Positive) bacterial problems.

It is very common for a well to have years of operation prior to experiencing loss of capacity. With age it is common to see these lost capacity problems frequently. The increased frequency of lost capacity and the need for well cleaning and rehabilitation treatments is due to the incomplete removal of plugging deposits from prior rehabilitation efforts, thereby not maintaining the original pore volume of the gravel pack, well screen, or fractured formation.

Effective water well rehabilitation requires the removal of all deposited material thereby allowing the specific capacity and pore volume to be restored. There are many different strategies and methods used in water well rehabilitation, some successful, others less successful.  The success in using many of the physical and chemical methods is dependant on the user being able to fully identify the plugging material, or combination of plugging material and design a specific chemical treatment to dissolve that material.  This becomes a daunting task due to the variability of the complex geochemical and microbiological underground environment and the reliance of the user to perfectly design a specific chemical combination required to fully remove the plugging, while not effecting well construction.

Aqua Freed is relatively broad ranging in its ability to effectively disrupt and remove a wide variety of plugging deposits, in a wide variety of well construction types and materials, offering superior deposit removal and more complete pore volume recovery, without adversely effecting well construction.

The Aqua Freed water well cleaning and rehabilitation process uses gaseous and liquid carbon dioxide to restore water wells. Since 1988, theAqua Freed process has been used on more than six-thousand wells worldwide with excellent results. The Aqua Freed process has been used on a wide variety of wells including vertical wells, horizontal wells, collector wells, directional wells, angle wells and extraction wells, from shallow to very deep wells, from small diameter to large diameter, screened and open hole. Many of the wells treated have been rock open-hole wells that do not have a well screen but are completed in fractured formations of limestone, dolomite, granite and sandstone.

The Aqua Freed process is more effective at removing deposits from both inside the well screen and the formation surrounding the well. One of the active components from the injected gas is carbonic acid, a mild acid, which under atmospheric conditions produces a pH of +/-6.0.  However, there is pressure in an aquifer or a sealed well, allowing the pH values to become reduced to as low as 5.0., still relatively mild.   When the pressure is released the pH will return above pH 6.0 and therefore does not become a neutralization or disposal concern. There is also the effect of localized freezing and and more importantly, agitation, as the liquid carbon dioxide is injected at approximately 0°F. The Aqua Freed process is not an overly aggressive process, yet is capable of delivering the necessary energy required to be effective in wells constructed using PVC or HDPE wells, without problems.
Aqua Freed equipment

The success is not achieved through the freezing but rather a combination of carbonic acid, agitation, and localized freezing resulting in superior disruption and detachment of the encrusted and plugging material.  The bulk of the activity is due to phase changes. The expansion rate from a liquid to a gaseous state of the carbon dioxide is 570 times in volume. The agitation achieved with liquid carbon dioxide is the same action as when dry ice is placed in water. There is agitation as the carbon dioxide changes, in this case, from a solid to a gaseous state. The Aqua Freed® process is the controlled injection of carbon dioxide, as injection pressure and down-hole pressure are monitored to regulate the feed rate the well will comfortably accept. The rate and volume of carbon dioxide injected is regulated to assure that the pressures (and energy) going down the well can dissipate into the surrounding formations.

Gaseous and liquid carbon dioxide contain tremendous energy, described as energy of dissolution, energy of detachment and energy of agitation. This energy results in the detachment, dissolution and removal of sediments and encrustation from the surfaces within the well screen and the surrounding aquifer.

Mechanical Well Rehabilitation that STI offers include:

  • Wire Brushing
  • Swabbing
  • Simultaneous airlift swabbing

STI can offer chemical rehabilitation with a variety of chemicals commonly used in Well Rehabilitation. However, chemical treatments are generally less effective than Aqua Freed® in the removal of deposited plugging material and therefore only partial deposit removal is often achieved.

The chemicals that are commonly used during chemical well rehabilitation include:
Acids: Hydrochloric, Sulfamic, Hydroxyacetic, Citric, Phosphoric.
Disinfectants: Sodium Hypochlorite, Calcium Hypochlorite.

Safe, Effective, Economical Well Restoration

Compare Aqua Freed® to other water well rehabilitation methods.

Because Aqua Freed® does not use any harmful acids or chemicals, there is no adverse environmental impact. In fact, the Aqua Freed® process was recently awarded 'Canada's First Environmental Choice' for well rehabilitation.

Traditional chemical, or mechanical treatment efforts, result in localized effectiveness. The Aqua Freed® process achieves excellent penetration into formations at greater distances from the well, where plugging is often difficult to remove.
The Aqua Freed® process can fully restore water well capacity. It can also improve the quality of water degraded by biochemical activity.
Results are demonstrably superior.
Because fewer steps are required, Aqua Freed® can often return wells to service in less time than traditional methods. A typical treatment time averages three days.
The superior penetration achieved by the Aqua Freed® process results in greater cost effectiveness because it often extends the life of the treatment well beyond that of the other methods. Since carbon dioxide dissipates naturally, there are no hauling or disposal costs.

Aqua Freed® is excellent for gravel pack wells, open hole wells, horizontal collector wells, environmental monitor and recovery wells.

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