Water Well Journal Q&A

DONALD TEETERS
The founder of Continental Technologies Inc. shares how successful rehabilitation or development depends on reaching the problems where they exist.

By Mike Price

Industry veteran Donald Teeters loves the challenges that come with well rehabilitation.

Donald Teeters

Teeters, a licensed Kansas water well contractor since 1995, is widely known for his ability to find solutions for the rehabilitation of problem wells. He has worked on some of the worst wells in the United States and discovered what’s effective.

As founder of Continental Technologies Inc. in 1991, Teeters’ consulting firm also manufactures a chemical line used to rehabilitate water wells with scaling or bacterial issues. He has presented on well rehabilitation at past Groundwater Weeks, and most recently in 2024, led the workshop “Why Did My Last Rehabilitation Not Meet Expectation?”

Water Well Journal caught up with Teeters to learn more about what he shared with attendees and examples of mechanical and chemical applications along with their effects.

Water Well Journal: Considering your Groundwater Week 2024 workshop title, what are the most common mistakes that you see in failed well rehabilitation efforts?
Donald Teeters: There is no silver bullet. When I first got into the well rehab business, I had a friend in Texas who wanted to handle the distribution of the product we designed to dissolve iron bacteria. He began contacting people who were into rehab and had little success as we recommended mechanical surge blocking along with chemicals to restore well production, and the drillers were not ready for that step in 1991.

The directions for use on other products were merely to dump the granular product into the well and come back 24 hours later and pump it out. Now everyone recommends mechanical energy in the rehab process. Make sure you use the right products for the problem you are trying to solve and always do the extra work like brushing and surge blocking to get the most out of the rehabilitations. In well rehab, you get out of it what you put into it. There is no silver bullet!

Teeters has worked on some of the worst wells in the United States and discovered what’s effective. Photos courtesy Teeters.

WWJ: You mentioned in your workshop that you commonly see drilling fluid (mud) damage in wells needing rehabbed due to polymers being present. How should one calculate the volume of treatment needed and the preferred ratio of the chemical treatment with a surfactant?
Teeters: We are all getting better at development as time goes along. Breaking old habits can sometimes be hard as we have been told forever to set your development pump above the screens and pump slow. This is a good process to begin with as you do not pump materials fast into the face of the formation and gravel pack.

When you consider velocity carries fines, it is good to start slow to get many of the fines out, then increase the flow to bring more in. If you can remove the fines from a larger area around the wellbore, you effectively reduce the velocity and carry less fine materials into the well. All wells make fines. Increased velocity increases them.

Mud damage can be a problem especially when there are polymer muds. From my oil business days and fracking wells, you break down polymerized water that carries the frac materials with chlorine. If you add a good surfactant to this solution and place it where the mud damage occurred, it makes the process easier. Generally, this solution has to be at least three times the casing volume to reach the damage. You will accomplish nothing by treating the water in the casing as the damage is in the formation. It came from the drilling efforts before the well was cased and gravel packed.

WWJ: The presence of formation fines in all wells was another topic you raised that lowers water production. What’s the relationship between formation fines and iron bacteria (or other bacteria for that matter) in relation to well rehabilitation?
Teeters: We do not generally see fines or have to deal with them on properly developed wells. As time goes on, bacterial contamination and mineral deposits change the percent of open screens and therefore slow the fines from coming into the well. Once the fines start to accumulate, it is easier for them to screen out behind the accumulation and increase.

If the bacteria stopped the water flow, it would also stop its food source and be counter-productive for its existence. We find more often it is the accumulation of fines in the face of the formation and gravel pack that cause production loss. We watch for the fines we remove to come into the hole through surge blocking and do not believe we are done with the rehab until we see some.

WWJ: For new wells, you’ve seen upfront success in well development time decreasing drastically with the use of biocide treatment to kill both bacteria and break down polymers from drilling fluid. What made you try this treatment protocol on new wells, and do you see this practice becoming more common in the industry?
Teeters: We’ve seen this process become more common in recent times. I have drillers who have adopted our development techniques in many areas. Again, it is hard to break old habits and some of what we do is not generally accepted by second- and third-generation drillers. With the addition of aquifer depletion, we are seeing the need to do more initial development than previously required.

A good well will oftentimes develop itself. This is based on pressure and volume. Volume is a result of porosity, permeability, and pressure. What made us originally try chlorine and surfactant was a well in the Central Valley of California’s Water District that was not performing like the others in the area.

The well we worked on was only capable of 300 GPM when all others were over 3000 GPM. This District had electric logs on its well and indications were the porosity as well as permeability were similar so the wells should produce closely to the same amounts.

The gentleman in charge said his board wanted to plug the well only making 300 GPM and drill another. We got that well to producing 3300 GPM with a chlorine and surfactant combination. We used a frac tank and mixed 200 pounds of calcium hypochlorite and 20 gallons of surfactant in the 20,000 gallons of water and ran it in and out of the formation, proving it was mud damage and not a bad well. We have repeated this process on many others in many states since that one in 1995.

WWJ: You’ve seen successful results by switching the order of treatment, with biocide treatment first, then acid. Why the switch and why the success?
Teeters: We do our biocide treatment exactly opposite of what all others do. The reason behind this is the bacterial colonies cannot be dissolved with chlorine, but it will kill all bacteria it comes in contact with that is not colonized yet.

When you put the chlorine solution ahead of the acid solution, it has a dual purpose. First, it goes further into the formation killing the free-swimming bacteria further back in, and secondly, allows you to know when you have the full treatment solution back. If you cannot smell or test chlorine, you have your entire treatment back and can hook it up to the delivery lines.

There is one more benefit to this way of doing the treatment. That is when the two mix down hole, the interface produces chlorine gas and hypochlorous acid which both are one hundred times more powerful as a biocide than the hypochlorite ion. You should never mix an acid and an oxidizer on the surface. If it happens down hole in a controlled environment, it can be an aid in disinfection.

WWJ: You’re adamant that contractors do the math when it comes to calculating volumes of casing, filter pack, and distance of bacterial contamination to determine the treatment dosage needed. What are the key equations needed?
Teeters: It is a complete waste of time and money to try to disinfect a well or to especially dissolve a bacterial colony by adding something to the casing and circulating the well. Nothing moves below the intake of the pump and the problems exist further back in the formation. The screens can be 95 percent clogged and still by design allow the same amount of water to come into the casing. The problem that affects water output is in the formation or at least the gravel pack.

Unless the borehole size is greater than normal for the size of the casing, the following values can be used with success: One-and-one-half times the casing volume will generally fill the casing and the gravel pack. Three times the casing volume is required to get to mud damage as it occurs while drilling before there is a gravel pack and casing. So, if you are doing acid and biocide treatment, one-and-one-half times the casing
volume for acid and biocide equally are required. If it is a biocide and surfactant treatment for well development and mud damage only, then you use three times the hole volume.

WWJ: You say getting behind the well screen is key for rehab. Which methods do you prefer to do so?
Teeters: This is a judgement call by the contractor. We have found you may not generate nearly as much energy in 4-inch cased holes by surge blocking as you can by dumping in and pumping out and repeating this. It takes energy and movement in and out to keep the chemistry from having a spent space next to the scale or bacteria you are trying to remove. The more action you can get, the better results you will have.

Roscoe Moss Company, the casing and well screen manufacturer, put out a paper showing the energy created and how far into the gravel pack and formation it goes that is interesting. Surge blocking delivers the most energy the furthest back behind the screen area of anything you can do.

WWJ: What should contractors know about the use of chlorine types for well rehabilitation?
Teeters: It really makes no difference to me what type of chlorine is used as long as the part per million is around 500. I have personally seen it take 400 ppm to meet demand, so if a solution of 300 ppm was used, it would not have had a successful kill on the bacteria.

One good thing to remember is if you do not have a smell of chlorine when you pump to waste, you need to repeat the chlorination. Sodium hypochlorite gasses off in the container fairly rapidly, so what you think you have might not be as strong. I personally use calcium hypochlorite and have had great success, and it is easier for me to transport and mix.

WWJ: What have been the results in rehabbing wells only mechanically vs. only chemically?
Teeters: The results only mechanically can be seen when pumping to waste after surge blocking before a chemical treatment. The results from chemical only is still a little bit misunderstood, and as we have stated, there is no silver bullet and all chemical treatments consist of some mechanical energy whether it is surging back and forth or some type of movement to keep hot chemicals on the scale or bacteria to be removed.

The combination of surge blocking and chemical treatments have had the best results of everything we have done for the last 30-plus years. The removal of the loosened debris after mechanical energy before the chemical treatment has proven to be the best practice as well. Get rid of everything you loosened up mechanically and let the chemicals dissolve what you did not get mechanically.

WWJ: What should contractors expect from their rehab, and what does long-term success look like in your mind?
Teeters: When setting expectations for acceptable results, you must look at the aquifer depletion. If the static water level is the same depth as it was when the well was making more water, you should get back to the original volume. Poor well design can have an effect on this though.

If the driller promised a sand-free well and placed a gravel pack material smaller than the fines that normally come from the well, this can cause a pump-to-fail scenario. If the fines cannot be brought through the gravel pack in a rehab situation, the well cannot be brought back to original production.

We like to rehab the wells and bring them back to new standards and sometimes better than new and do a maintenance treatment consisting of a chlorination only the same size as the chlorine and acid treatment we used in the rehabilitation and do this once a year to keep them clean. You can do this without pulling the equipment and we have seen the wells last as many as 15 years without requiring the pulling, surge blocking, and acidizing to keep production.

WWJ: Lastly, how do you respond to those who say you lose 10 percent of a well’s production every time you rehab it?
Teeters: Chemicals and techniques have advanced so much that this is not the case any longer. As long as the right products and mechanical energy are implemented in the rehabilitation efforts and expectations are realistic based on aquifer depletion and other completion techniques, the wells will have great success. A great success cannot be measured by getting back to original production unless the static water level is near the same as it was during the original testing.

If the static water level is the same as before, the well was designed properly, and no outside influence is noted, a well that does not come back to near original production is not finished yet.

We have taken wells that were 25 years old and down to 10 percent of their original volume and brought them back to their original volume. Don’t give up on one that just needs a little more work. The well will let you know when it is done and ready to put back online.

Mike Price is the senior editor of Water Well Journal. In addition to his WWJ responsibilities, Price contributes to the Association’s scientific publications. He can be reached at mprice@ngwa.org, or at (800) 551-7379, ext. 1541.