Tools – Brushes, Plungers, Tremie Pipe
Tools can make a significant difference.
Brushes. The concept is to use the physical action of a brush to remove as much matter as possible, however without damaging the casing. Surely a stainless-steel casing of any age can handle the physical stress of aggressive brushing, mill slot steel casing as well.
However, aged steel louvered or wire wrap screen is a different story – and brushing with any aggression could damage the casing including the loss of the well. Why even use aggressive brushing is that it will reduce chemical demand and the physical removal is usually the least expensive?
Brushes, regardless of how aggressive, are not going to remove dense scale, nor do they remove nodules or dense tuberculation. They do and can however remove biomatter, as well as scarify biofilms (polysaccharide), allowing for more effective chemical penetration.
The more matter physically removed provides the ability to clean the well more – and a cleaner well will last longer because most wells are plagued with bacteria. The more bacteria removed, the longer it takes for them to recolonize the well and become problematic again, with or without scale. Most wells are problematic by bacteria at 14 years of service.
What is considered aggressive brushing is the maximum amount of stiff bristle that will NOT compromise the integrity of the casing or the perforations.
Spiral versus block bristles – Spiral will operate like a drill and with 720-degree coverage you can assure 2 passes on the same surface, 100% coverage, in one stroke. Likewise, the spiral operates like a drill pulling itself through. If by chance you get infill, it can spiral through the brush to the floor of the well, preventing a stuck tool/brush.
Plungers – We hear the term swabs and we see very little value in the use of a swab. To put this into context, we may use a swab to clean a toilet bowl, but we use a plunger to unclog drains. We promote plungers to move chemistry and energy though perforations and into the filter pack. But cautions have to be put onto place as too much plunging on the wrong casing could cause damage. Not designing the plunger correctly could be a waste of time and resources, and or cause the tool to get stuck downhole form infill.
Plungers are constructed to plunge, and they are V cut for multiple reasons, namely to allow the tool to generate the plunging but also to release any infill that may be dropped on top of the tool from the loss of filter pack. Note the plungers are usually double top and bottom, may have a divider at 5 ft. intervals, usually no longer than 20 ft., each disc is supported 60% by steel on both sides. The V cuts are designed by the number of V cuts and the width based on the amount of energy we may, or may not apply based on the casing and its’ durability.