Rehabilitation, cleaning of wells and equipment recovery

  1. Water well rehabilitation by means of impulse generators (pulsing)

When constructing a new water well (1), the tubbing casing, the well bottom and the gravel pack should be free from debris. But even at newly drilled wells, bentonite or other drilling fluids can influence the proper performance of the wells. Often, after a certain period of well operation, little by little sediments/colmanates arise, which can be differentiated into interior (2) and exterior (3) sediments.

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Furthermore, in the course of time, the water creates so-called “micro-preference-channels”, causing an entry of foreign substances, impurities or pollutants.

The purpose of each well regeneration is not only to remove the visible sediments inside the casing (e.g. by means of brushing), but also the hidden sediments behind the casing, in order to achieve sustained cleaning success and thus an increased performance in the yield of the well. One of the most efficient technologies in this regards is the so-called “pulsing”.

Pulsing is a hydraulic pulse process, certified by the German DVGW technical bulletin W 130, based on the sudden expansion of highly compressed gas or liquids, mainly for:

  • increase and/or recovery of the productivity of wells and drillings;
  • re-establishment of the operability of groundwater measuring points;
  • mobilization of pollutants;
  • re-arranging the gravel pack
    • at newly drilled wells to settle the gravel properly
    • at old wells to avoid the entry of foreign substances or impurities.

The operating principle is based on the fact that by pulsating gas or water portions under high pressure effected by a pulse generator – which is brought into the well by a flexible pressure hose – pressure pulse strings are produced. The pulse generator is equipped with a valve system, being able to release accumulated energy in form of high-pressure gas or water in very short response times (milliseconds) by opening large cross sections developing hydraulic shock waves. At the same time, due to the sudden change in volume, a cavitation effect (hollow suction) is caused, resulting in a “vacuum blister”, producing a hydraulic “suction wave” after collapsing.

The alternating effect of the pressure load and release is causing a loosening of the fine fractions, sinterings, sedimentary depositions, etc. which were in-rinsed into the gravel filling and the pore area of the aquifer. The so-loosened colmanates is transported by the “suction wave” to the well center, where it is pumped off.

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Main characteristics:
  • the speed of the impulse generation amounts to approx. 2000 m/s and is adjustable in a specific spectrum during the operation
  • generation of a soft pressure impulse, whereby a wide variety of production materials such as (stainless) steel, polyvinyl chloride (PVC), stoneware, etc. can be processed
  • production of pressure pulse strings, whose chronology during the operation can be adapted – depending on the well characteristic the procedure can be adjusted “more intensive” or “more gentle”
  • the level of the initial pressure of the impulse is changeable, which enables an adjustment both to the production material and the actual condition of the well
  • fast, cost-efficient application by small operating expenses

The advantages over other technologies are that impulse generators feature the very best depth effect in penetrating the adjacent soil formation (up to 25 m), thus opening the pores of the water layers, mobilizing potential pollutants and re-arranging the gravel pack. The process specification offers the possibility of a specificly targeted, depth-orientated treatment of locally strongly contaminated areas. From ecological point of view this procedure remains completely harmless as during the application there is absolutely no input of environmentally hazardous or foreign substances like chemicals and explosive gases to permeate the well. But – in certain cases – pulsing shall be combined with chemical treatment, whereby pulsing highly intensifies the effect of chemicals during their residence time.

  1. Water well rehabilitation by means of Airjetting

In case pulsing is not applicable due to unsuitable well casings (materials like ceramic, asbestos cement etc.) or already damaged filter screens, airjetting is a simple and soft but effective method to clean wells, mains, drainage and/or other water pipes from ferric, manganese, humous, sludge, sand and other sediments and to avoid turbidity, unpleasant odour and taste.

A certain volume of air, which is either purified (cooled – oil-free – sterile) by a computerized air preparation facility or directly produced from compressed air bottles, is injected via an air-hose into the well. The down part of the air-hose is equipped with a special valve system, whereby high flow rates can be achieved. The turbulences and cavitation effects, created by the air-water mixture, cause an efficient loosening of all kind of sediments, debris or bio-foulings, which will be flushed out of the well by means of airlift.

Airjetting operates within a standard uniform and continuous pressure range and thus prevents a possible damage of casings, screens and pipes.

Fields of application:
  • up to 400 mm ID possible
  • in water wells:
    • casings & filter screens (cased hole) borehole walls (open hole)
    • Pereti cu orificii (orificii deschise)
  • in water pipes:
    • raising mains
    • fresh water pipes
Main advantages:
  • easy and effective method
  • improvement on pump operation
  • savings on energy costs for pumping
  • good cost-value ratio
  • preventive process of incrustation