Physical Methods

Swabbing, by wire brushes or other methods, can be used to remove encrusted materials on the inside of a well screen. The material can be removed from the well by pumping or bailing. Swabbing is often used prior to chemical treatment. Care must be taken in using swabs to insure that the well screen is not damaged. Improper technique may transfer loosened material and cause further plugging of perforations in the casing or screen.

Jetting is sometimes used in well treatment for problems due to mechanical blockage. When used in conjunction with polyphosphates, jetting can loosen and wash out fine grained materials in the vicinity of the well screen.

Sonar-Jetting is a well stimulation technique designed to reopen plugged perforations and wash deep into water bearing formations. This technique consists of two physical actions working simultaneously. First, a mild harmonic frequency of shock waves loosens mineral, bacterial, or other type deposits adhering to the screen and casing. Second, pulsating, horizontally directed gas pressure jets fluid at high velocity back and forth through the perforations to deep clean the aquifer. Light "shooting" with prima-cord can also physically break hardened scale from the casing or screen.

Chemical Methods

The use of polyphosphates, surfactants, and physical agitation has been successful in some cases for improving well performance due to mechanical blockage. Fine grained soil materials can be dispersed by polyphosphates and surfactants. Surfactants are a group of chemicals called "Surface Active Agents" that have the ability to reduce the surface tension of water and allow particulates to move more freely in the formation pore space. These compounds cause the fine particles to repel each other and move through the gravel pack and screen and out of the well. Physical agitation can act to accelerate this process. Detergents and surfactants may also be used to improve the performance of wells in which drilling fluids were not fully developed out of the well during construction.

Acids are used to chemically dissolve encrustation formed in a well. Acids can dissolve calcium and magnesium mineral deposits. Although acids are not typically effective at killing bacteria, they are used to dissolve iron and manganese oxides formed because of bacteriological growth. Physical cleaning methods, such as brushing, swabbing, or Sonar-Jetting can be used to supplement the acid treatment.

Disinfectants are chemicals which are used to kill bacteria present in the immediate vicinity of a well. Chlorine compounds are the most widely used disinfectants because they are inexpensive, readily available, and proven effective against many types of bacteria. Bacteriological plugging is typically treated by a combination of methods to destroy bacteria and to remove iron encrustation. This treatment often consists of alternating chlorine and acid solutions, combined with physical treatment methods.

Chemicals may be placed in a well in several manners. One typical procedure involves the introduction of the chemical into the well through the well pump. This procedure does not require the expense of pulling and resetting the pump. However, this procedure may allow the pump to be damaged by concentrated chemical solutions. Also, this procedure does not ensure thorough mixing of the chemical throughout the entire length of screen. Often the chemicals dissipate through the unplugged portions of the well screen and do not penetrate the area of greatest need.

Alternative procedures for placing chemicals in a well screen include the use of surge blocks to accurately place the chemicals in specific zones of the screen, and the use of a bailer. These procedures require that the well pump be pulled from the well.
All chemicals used during a well cleaning process must be carefully removed from a well and properly disposed. Water should be pumped from the well until the water quality is essentially the same as prior to treatment.