ARTESIAN WELL CONTROL
Confined aquifers occur when groundwater is restricted under pressure by an overlying confining layers of clay, stone, and glacial till. If a well penetrates a confined aquifer, the water level in the well will rise above the top of the aquifer. Confined aquifers are also known as artesian aquifers. If the pressure in the aquifer causes the water level in the well to reach the ground surface, it is called a flowing artesian well and requires artesian well control. Wolverine Drilling Inc. is very familiar with artesian well control process and requirements to complete this successfully.
Flowing artesian wells can cause a few significant impacts. The run off from these artesian wells can be substantial. They always need a place to run too that does not cost loss of farm land, property or damages. Well packers are used to stop or reduce the flow of these wells, yet we have not found one well packer manufacturing company that will warrantee their packers. These wells can mushroom over with ice buildup during winter and temporarily stopping their flow. In some cases, the casing can crack and break during freezing and require a repair. We always recommend drilling with the heaviest walled PVC casing possible when drilling in areas that are known to have artesian wells. Currently this is a 250-series telescopic PVC casing. Threaded casing tends to leak at the threads, that can follow the annulus to surface. In some cases, this can not be corrected without pulling the casing out and screens out, and re-drilling with the proper 250 series casing. In some cases, heavy, pressurized grouting of the annulus can assist to reduce the leaking. It is best to prevent it in the first place.
When drilling in an area of Artesian wells, we are equipped to manage our drill muds to stabilize the hole upon contact and infiltration. We have 600gal of muds ready and a second trough feeding with concentration mix ready. We are one of the few drillers that have successfully manages 60ft flowing head pressures in areas that were not known to be artesian areas with relative ease. We are a company that often gets called in to correct and manage artesian wells that others struggle with.
Stainless steel screens are widely used in drilled wells because they have many advantages over slotted casings. They facilitate better well development, and result in much more efficient water wells. They are also strong, relatively well suited to withstand corrosive waters, and are much more conducive to well treatment. The screens are manufactured with various regularly shaped and sized slots to match the characteristics of the aquifer.
Slot Size Opening
The width of slot openings should be chosen to match the grain size of the aquifer. The slot openings should be small enough to permit easy entry of water into the well while keeping sediment out.
The width of openings needed can differ between wells in the same formation depending on whether the well is naturally developed or filter packed. Aquifers with coarse-grained materials can be developed naturally, whereas those featuring fine-grained homogeneous materials are best developed using a gravel pack.
In naturally developed wells, the screen slot is selected so that approximately 60% of the aquifer material will pass through during development. The remaining 40%, comprising the coarsest materials, will form a natural filter pack around the perforations or screen.
Artesian well control requires a strong understanding of the geological principles. With over 15 years water well drilling experience, Wolverine Drilling Inc. is confident in our ability to complete the project correctly the first time. Contact us directly should you have questions or require artesian well control.