WorldWide Drilling Resource®

Notes from the Groundwater Guy by Thomas E. Ballard, P.G., C.H.G. Southeast Hydrogeology, PLLC Common Causes of Well Failure - Neglect All the causes of well failure we have talked about in recent posts have been controllable. Neglect is probably the most common cause of well failure, while at the same time, one of the most preventable. Yet, the most common well management technique out there is to run wells until they quit pumping water. Of course, wells never experience catastrophic failure at convenient times - it is most likely to be something like 3:00 a.m. on a holiday! In the normal course of operation, and dependent on groundwater chemistry and other factors, wells will plug up due to silt and clay plugging, biofouling, and development of mineral incrustations, all of which will plug the formation, gravel pack, and screens over time until, eventually, the well will cease to be able to produce water at anywhere near the required rate or perhaps no water at all. Although these processes also affect open-hole bedrock wells, they can manifest themselves in some- what different ways, but the effect is still the same - the pathway of water into the well and the pump becomes restricted and well production is reduced over time. While these are natural processes occurring in all wells, they can be managed through properly timed well rehabilitation. Well rehabilitation methods should be specifically tailored to the problems the well is experiencing and take into account groundwater chemistry, microbiological parameters, the condition of the well, and other factors - or the rehabilitation efforts may experience limited success. So how do we know when to rehabilitate a well? Some well owners schedule rehabilitation on a routine basis - maybe every five years - and this technique can certainly work, but such an interval should be based on actual plugging rates expe- rienced in the well, otherwise intervals between rehabilitation may be too long, resulting in the need for more aggressive and more expensive techniques to restore well performance. By employing a well health check process that takes into account the condition of the well and its primary plugging factors established by video logging, analytical data, bacterial loads, and well design, an effective rehabilitation program can be designed for the well that will have the greatest chance of success in restoring and maintaining well performance. By per- forming the rehabilitation when well conditions indicate, the cost of each rehabilitation can be reduced while at the same time allowing the well to maintain a long productive life, free from the problems of neglect. Tom Tom Ballard may be contacted via e-mail to michele@worldwidedrillingresource.com 31 WorldWide Drilling Resource ® JANUARY 2020 WTR