Simple Do’s and Don’ts to Well Rehabilitation

Avoid serious pitfalls with these guidelines.

By Edd Schofield

The key to any successful water well chemical cleaning is set in a three-step process.

First, we need to identify the type and the magnitude of the problem, understanding the nature and extent of the blockage. Then we need to determine the condition of the well structure itself and the full extent of any damage or degradation that has occurred.

If we’re serious in thoroughly getting the well’s issues properlydiagnosed and subsequently treated, we will need to pull the pump. This access will allow for running a (pre-treatment) video. This will also assist in identifying any potential patches, mechanical repairs, or design oddities that might affect your treatment decisions. Such an examination will greatly assist you in determining how aggressive you can get without jeopardizing the physical condition of the well structure.

Early identification of holes in the casing or existing patches will likely affect your decision as to how aggressively you are willing to physically work over the well prior to chemical treatment. Well rehab projects typically vary by individual well conditions, and as such, each well exhibits unique issues based on the integrity of the well structure itself.

The author presented on the topic of this article to a standing-room-only crowd at Groundwater Week 2024.

Gather Well Information Before Selecting Options

We need to select the appropriate mechanical and ultimately chemical treatment options.

Along with the video logging to determine the physical condition of the well, ask the well owner what all has been done to the well prior to your arrival. If possible, determine what has been successful and what was not. Often you are going to be asked to fix the mistakes of a previous rehab attempt. So, it’s best to ask how we got to this junction.

Don’t just assume that what worked great on your last well rehab project is the best option here on this upcoming rehab. Every well is uniquely different, and you need to keep that in mind when making treatment decisions based solely on previous projects. Strive to select the best acid type and acid enhancers carefully, read up on each product, and consider the benefits and detractors.

There are numerous articles from Water Well Journal that discuss the merits of various acid types and their advantages and disadvantages. We also must realize there are no magic or silver bullets. As such we need to balance the economic and viable treatment recommendation to the customer.

We cannot introduce chemistry into a well and anticipate a miraculous recovery when so much mineral deposition and plugging have brought us to the point where we’ve been called to address inefficiencies or production declines. Simple mechanical agitation in concert with chemical introduction is going to have the highest potential of success in any well rehabilitation.

Read the suppliers’ technical brochures as well as taking advantage of the suppliers’ online resources and chemical calculators that should provide you not only dosages but complete chemical treatment procedures to follow. Carefully review all your options and specific chemical properties and weigh those with what your own operational capabilities and experiences are before moving forward.

Vigorous mechanical activity will greatly improve removal of any blockage and facilitate chemical distribution back behind the pipe where the greatest impact is most needed.

Setup and Process Guidelines

Lastly, be prepared for the full well rehabilitation process by carefully laying out and positioning your equipment and bulk chemistry on site.

Anticipate the ultimate equipment layout with safety considerations and the final neutralization process in mind. The same mix tank should suffice for surface neutralization of the returns. Anticipate your ultimate discharge and related neutralized volumes.

In addition, just as you would not guess on your treatment volumes, don’t guess as to sufficient neutralization dosages of say soda ash or magnesium hydroxide. It is recommended that you have some additional acid on site in case the chemical reaction downhole warrants additional acid to maintain a pH below 3.

Also, keep more than a sufficient supply of your neutralizer on site as well in anticipation of any unforeseen emergency. Always test your lines and pumps with water prior to mixing any chemistry to assure a secure setup and have adequate soda ash on site in case of any leaks during the treatment.

Be sure to pump water through the treatment lines, once having spotted the acid, to eliminate splashing of any solution onto the crew. Observe prudent safety precautions whenever mixing the acid into the treatment water within the surface tanks. Always have a full eyewash station nearby and discuss emergency preparedness protocols as part of your tailgate in case of a leak or spill.

I’ve personally closed a couple of highways to traffic and even a golf course over my years, thanks to downhole issues. I had a treatment line rupture that ran down a busy street and a billowing cloud of gas spew forth from a wellhead, all while treating wells, so be prepared! Know your immediate environment and keep track of the wind directions.

Once acid remediation work is initiated, remember the optimal acid cleaning occurs at a pH less than 3. That means to be most efficient, we need to periodically sample the downhole solution to ensure a pH of less than 3 to sustain a fully effective cleaning chemistry. Once the acid is in play, if possible, every hour sample the solution with a disposable bailer and check it with pH strips to ensure we still are effectively attacking the mineral scale downhole and not just wasting time.

If the pH is allowed to rise while downhole, then we often initiate or encourage re-precipitation of the very material that we just solubilized once pH readings exceed 5.

The acid solution should be pumped or injected across the entire screen interval to facilitate even and uniform placement. Another key to any successful well rehabilitation is the agitation of the solution downhole.

Vigorous mechanical activity will greatly improve removal of any blockage and facilitate chemical distribution back behind the pipe where the greatest impact is most needed. This affords sufficient exposure of fresh treatment solution against fresh scale or biofilm deposits.

Evacuation Guidelines

Once successful acid treatment is concluded, we need to evacuate the well of all the treatment solutions and the byproducts left at the bottom of the well. All of this is done against a continued backdrop of a pH of 3 or less.

Neutralizing downhole considered by many as harmless is nothing but misguided—as the very material we worked so hard to solubilize will re-solubilize downhole as the pH is allowed to rise. So be blunt: Do not neutralize any acid solution downhole. Don’t even dilute the acid solution downhole.

Bring it up hot with the solubilized mineral scale and neutralize it above ground. This is where additional storage on the surface of two tanks comes in handy. Our returns are brought up and neutralized back to a pH of 7 in one tank and then transferred to the second tank, allowing for sufficient time for the solids to completely settle out before disposal.

In today’s environment, we need to recognize proper disposal protocols. SDS sheets are good to have readily available to address local site regulations concerning diversion or disposal of the neutralized material.

At the end of the day, we need to assure ourselves we’ve done no harm to the well structure in addition to returning all the chemical treatment solution to the surface and properly disposing of all the material in a safe and efficient manner, all while being aware of our environment.

Edd Schofield is the technical sales manager–chemicals for Johnson Screens and has been with the company since 1988. He served as the Groundwater Foundation’s McEllhiney Distinguished Lecturer in Water Well Technology in 2007. He can be reached at edd.schofield@johnsonscreens.com.