Prevent the Stank in your Tank

Virginia Wornstaff

Dear Friends and Colleagues,

In this buckle up and ride it out environment we are in, keep in mind we are all in this together, adapting as we go. We are experiencing new challenges daily as a result of unplanned idle time and not just the Netflix kind. On my mind, is the challenge of idle water. Currently due to the lack of completions activities and limited water re-use, as well as disposal volume restrictions (depending on where you reside), water stockpiles have the potential to sit stagnant for an unknown period of time. Idle water challenges include the below real-life examples:

  1. I want to keep my frac waters clean so I can start using them as soon as its economic to restart completion programs, but I don’t know how long that will be.
  2. My disposal well is starting to experience increased injection pressures and reduced volumes. Is this the result of bio-buildup or biomass plugging?
  3. The holding tanks at my disposal site are starting to smell. I’m worried the excess and slow-moving storage volumes are growing too many bugs. How and when should I be keeping it in check?
  4. I am taking waters from more sources for storage or disposal. The water qualities are inconsistent, and I don’t know how to adjust treatment to compensate.
  5. I am seeing corrosion in my disposal system. Could this be the result of microbiologically influenced corrosion (MIC)? What can I do?

I’m going to talk through some choices you have and be very real about doing nothing or doing too little. I don’t believe we need comprehensive prevention strategies right now – it’s just not going to happen. But we need to maintain a working knowledge of our waters to ensure our assets remain useful and sustainable.

Doing Nothing Is Free, Until Your Time Runs Out

I often recommend holding off treatment of waters until they are being used. The economics of maintaining microbial control of a source water tank are far higher than if you simply treat prior to use. The limiting factor here is time. This plan works up until the point that the microbial population exceeds the economics of an at-use treatment program. The problem with microbes, is that they are not a static contaminant. The level of microbes per mL will fluctuate based on the environmental conditions and food source in the water. Food sources can be that skim of oil carry-over from the last load, or some vegetation falling in from the trees or birds in the area. Treatments will knock down the bug population, but over time they will grow back. If the timeline is manageable, just wait until the water is required for use and treat it then.

At what point does this thought process begin to fail?

  1. If there’s enough food and a nice growth environment, the microbes will multiply to the point that there are too many to handle.
  2. Stubborn biofilms establish in your asset and begin to burp out microbes steadily.

Now that efficient biocide program you once had, requires extra fire power ($$$$) to bring the population back in check. This is where monitoring is your friend. When you are in idle conditions for an unknown amount of time, treat based on established KPI’s. Create a cheap but effective monitoring program and treat when necessary rather then at-use. ATP testing is a great option, offering accurate tailgate testing with results in less than 10 minutes.

A logistics tip that works with smaller storage volume tanks – transfer to a clean tank before use, leaving behind any biofilm build up, reducing biocide consumption at site. Your program will be more efficient with less biocide required if you are targeting planktonic (free floating) microbes, and not the build up on your tank walls (known as sessile). Remember to clean up the old tank before refilling using low cost methods such as thorough steam cleaning and/or biofilm penetrating chems.

Treating LESS Often, May Require a Different Biocide Choice

This works hand in hand with the above discussion. Sometimes maintenance is required for other reasons such as smell. This can be a stakeholder complaint or more seriously a safety issue such as sulfide producing microbes pushing H2S levels into dangerous concentrations (this is happening more often than many would like to believe). Either way, a sustainable treatment program is required. Our instinct is to go for a cheaper biocide option, as we expect multiple dosages will be required. Think oxidizers and quats here. Both are fast and effective surface and tank treating options however, they have very little longevity. This results in a higher frequency of treating, blowing your economics in a long-term idle situation like the one we are in. A biocide with a slightly higher price tag, can save you money if you dose half the time – every 2 weeks instead of every 5 days, for example. Again, a low cost, quick result monitoring program (ATP testing) can be used to optimize. Track regrowth cycles and change up chemistry to a longer lasting organic biocide. Stay in the sweet zone when it comes to your bank account and the odor on site.

Another logistics tip. Moving waters will aid in mixing biocides, keeping the dosages efficient. This helps prevent the layering of sulfide generating microbes in the lower areas of the tanks. If rolling, cycling or other mixing options are available, go for it.

Aeration can be both a beneficial and detrimental option. Aeration promotes aerobic growth (microbes that utilize oxygen). These microbes will outcompete the anaerobic ones that produce the smelly sulfides. The downside is that oxygen loving microbes will flourish, resulting in the overall microbial load spiking. This makes treating down the line harder. And if these waters are injected it can result in increased potential of biomass plugging.

Treating at the Right Spot Will Save You Money

Some of our systems are more dynamic than others. Turn-over rates may be higher. Taking on more waters may also include varied water quality and fluctuating contaminant concentrations. Treating at the inlet may be the prime location for these types of handling facilities. When a tank is filled, apply a biocide into the new waters entering at the inlet. This is also a good way to ensure mixing and full contact with the fluids. It also ensures no untreated raw waters enter your system. The other method is to dose based on turn-over rates. If all storage vessels see a complete turn over in 4 hours, you will have to dose based on that frequency to ensure you are maintaining control. If timing is not consistent, dose anything new that enters so you don’t have to watch the clock, or risk missing nasty fluids.

How do you dial in the dosage in this scenario? For ease of application I would choose a static rate to apply at the inlet, based on experience and perhaps a few test results. This dosage will be on the lower end of the scale of what’s appropriate to keep things economical. Again, monitoring is key to ensure spikes are handled. Also just use human instinct. If you smell it or see something out of the norm perhaps you increase the rate for that load. Keep an easy to apply, fast acting biocide on hand to handle spikes. A great option is a water-soluble solid biocide that can be applied as needed to tanks that get out of hand.

All of this is under the assumption that the waters are significantly contaminated with microbes causing issues like odor or plugging downstream at disposal. If the water quality issues are few, employ monitoring protocols. Keep the fast acting, easy to apply biocides on hand for when the unplanned happens like a slow day under the hot sun, or a single batch of something extra buggy enters the system.

Corrosion & Plugging in Disposal Wells is a Layered Problem

Disposal wells have a multitude of contaminates to deal with: scale, paraffin, suspended solids, hydrocarbon carry-over, residual chemicals and biomass. Corrosion inhibitors or acid workovers may be the better option in many cases as they target primary or multiple contributing factors in a single application. Determining if a biocide is an effective choice will depend on either testing results indicating the issue is microbial in nature, or an evaluation treatment. Corrosion failure evaluations that include a failure site swab for DNA testing will aid in determining if microbes are a contributing factor. Even if corrosion is initiated by another means, microbes can and often will accelerate corrosion rates. We frequently apply a 10-fold multiplier to the risk analysis of assets with MIC related microbes in their fluids.

When determining if increasing injection pressures are caused by microbes, there are two practical options. First, if you are at the point of a cleanout, grab samples from the waters and solids coming to surface and run tests on them. Examining the solids for microbes easily with ATP testing, can point a finger at a biofilm or biomass that might be building up. If this isn’t possible, an evaluation treatment may get you closer (a clean out with biocide or application of a continuous biocide into the well for an appropriate amount of time based on injection rates). If the evaluation treatment indicates success (removal of biomass blockages), consider doing an aggressive biocide clean-out and create a control program further upstream in the system.

Testing Programs Will Keep You Optimized

No matter the microbial challenge, the goal is to maintain control with the smallest spend possible to keep our systems in good working order. In order to optimize, you must have data to make decisions. To know your minimum dosage requirements, or when your tanks are creeping up in microbe counts, you must test. There are a lot of options available either as an onsite kit, or a service. Testing frequencies need not be cumbersome or excessive. In the beginning, a few extra man-hours may be required to establish baselines, but for most systems a weekly or as-needed program can work very efficiently. ATP testing can be as little as $14 per test and save you $1000’s in unnecessary chemical use.

During this period of idle time maintain the long-term health of your assets and be ready for the moment activity begins ramping up. Don’t hesitate to reach out to myself or the team at OSP to discuss options specific for you. We are your trusted partner in knowledge-based solutions, proven chemical products and enhanced microbial testing technology. Stay safe and healthy.

~Virginia