Untreated source water can contaminate your reservoir post hydraulic fracturing

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It all begins with source water selection.

The control of microbes in reservoirs, wellbores and production systems continues to be a challenge. Why? Hydraulic Fracturing introduces high volumes of ‘foreign fluids’ into a well. In the absence of effective microbial testing, the fluid treatment is a guessing game. Which chemistry? How much? Check the box and apply 250ppm?

Microbes are living breathing components of our oilfield waters. Driven by survival, microbial communities naturally fluctuate. Each water will provide different nutrients and experience different environmental changes. If your water changes, so will your microbial community. Problematic microbe contamination within or near the wellbore can lead to sulfide production resulting in FeS or H2S. Take the time to care about the microbes in your frac waters by testing and treating for what is present in the fluid.

Proven Chemical Products For Hydraulic Fracturing Fluid Applications

Hydraulic fracturing utilizes large volumes of water to achieve improved hydrocarbon recovery. These fluid and proppant systems may vary in formula, but the carrier waters used will inevitably contain varying levels of microbes that have the potential to cause long term issues downhole. Many reservoirs provide conditions optimal for microbial growth, and upon introduction by fracturing operations, can contaminate the reservoir by establishing communities in the fracture networks.

The primary issues caused by a microbiologically contaminated reservoir are souring (H2S production by sulfide producing microbes) and microbiologically influenced corrosion (MIC). MIC may occur within the wellbore, or the microbes may be carried throughout an entire gathering system and into processing facilities potentially increasing corrosion risk of many assets.

In order to prevent microbial related issues, registered biocides can be applied at appropriate places in the hydraulic fracturing process to maintain microbial control. This ensures the health of the well not only during initial recovery but for the remaining production life.

Hydraulic Fracturing Proven Chemical Products

Did you know?

Within the frac process it is important to select the right biocide for the job and to test the effectiveness for the duration of the frac job.
All biocides provide a method of kill. Some offer a quick kill, immediately knocking down the microbial load. Others are work horses, offering long term reliability. It is important to think about the following:
1. How long does water sit on location before pumping?
2. How long is the pumping time?
3. How long is the shut-in period?

Complete a kill study that takes into consideration:
1. Source water
2. Microbial load
3. Length of time
4. Overall desired kill

READ MORE: Pro-active Steps to Avoid Post Frac Souring

Untreated source water can contaminate the reservoir.
Microbial contamination of reservoirs via the hydraulic fracturing process can lead to souring of production fluids. How? Frac source waters can comprise of microbes capable of producing sulfide, leading to well souring if allowed to flourish down hole. For this reason, microbial strategies are important in controlling contamination of a well.

READ MORE: What microbial community is present in my production fluid?

Not every hydraulic frac is equal but what every frac has in common is the use of water.
Hydraulic fracturing provides bountiful opportunities for microbial contamination if not properly controlled with a microbial control program. Pro-actively manage problematic microbes. Test the selected source water for active microbes including souring microbes. Then design the optimal biocide program based on your findings.

READ MORE: Produced Water Selection for Frac Operations

It may not be plausible to choose water with zero microbes. But that doesn’t mean we need to (or should) blindly accept using what’s available. Every water is different and has a different microbial community. Two waters could have the exact same number of microbes: one source has all harmless, non-threatening microbes, and the other has all microbes capable of well-souring. Ideally, given the choice, you wouldn’t frac with the souring-related microbes. By knowing the microbial threats in each source you can adjust your biocide treatment program accordingly.

READ MORE: Produced Water Selection for Frac Operations

Every time water is used, the quality of that water degrades.
Think of it the same as you would tires. The more you drive, the more the tire treads wear over time. The more they wear, the balder your tires become. This increases the risks every time you leave your driveway of a flat or worse, an accident. Water is no different. When we put water to use, the degradation process begins. Every time water is reused, we increase the load that water must carry. It is water plus everything else, inclusive of sand, inhibitors, friction reducers, other chemistries and debris. With this knowledge, we need to make wise choices with water and understand when it is time to ‘change the tires’.

Killing it in Completions

When asked about frac kill studies, Virginia Wornstaff, CTO, responded with some words of wisdom from her extensive experience. During frac operations, frac studies are often run for the duration – often a 48 hour test. Regularly, the waters are in the reservoir for a lot longer when taking into consideration the time before load waters are fully recovered. Also, the time between frac and production facility tie in can take weeks or even months. Based on this, the selected biocide will be challenged to maintain control for this extension in time. When working with clients who get random well souring in fields with consistent frac programs and treatments, we often see the difference is in the time between frac and production activities. This extension of time creates a little incubator full of warm, stagnant, nutrient-rich conditions. Now in charge of disrupting this reservoir Petri dish, the treatment program should be adjusted to compensate for the new performance demand. Completing a three-week study or a re-inoculation procedure allows for measurement of residual biocide effects after extended periods of time. With a goal of preventing long-term contamination of the reservoir, wellhead testing 30 days after your well comes on production is going to give you the best indication of success.

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