Five Biocide Myths That May Be Hurting The Bottom Line

Optimizing a microbial control program that considers the life cycle of oil and gas operations is essential to the success of well production. Over the years an integrated approach to microbial control—one that takes into account the impact of the drilling, completion and production stages—has proven effective in controlling the growth of problem-causing microorganisms. Such an approach, however, elicits a bewildering array of options when it comes to selecting the most effective microbial control program.

Looking specifically at the completion process, for example, it’s important that a program addresses the three distinct phases of water treatment in hydraulic fracturing: preparing the water for entering the well, decontaminating the well and protecting the reservoir.

There are several prevalent myths surrounding the microbial control treatments being used today for the completion process such as the popular and seemingly cost-effective option of using oxidizing biocides like chlorine dioxide (ClO₂).

It’s a myth that using chlorine dioxide alone is an effective means of protection from microbial-related problems. In fact, it’s a “quick-kill” option that only lasts minutes topside, leaving the wellbore and reservoir vulnerable to contamination, microbial-induced corrosion and souring in the longer term. By trying to save costs around biocide programs, producers may actually be costing themselves a great deal of money.

Myth 1: All biocides offer the same benefits

All biocides are not created equal. While some are specifically designed to offer the quick-kill topside protection previously mentioned, others provide extended protection under extreme downhole conditions, including high temperature and salinity. As every shale play and well is unique, it’s important to realize there is no silver bullet when it comes to microbial control. Depending on the environmental conditions and properties of the water within a particular geographic location, operators will need to define an optimized treatment program that may include selecting a different biocide or utilizing a combination of biocide chemistries.

Today a broad portfolio of biocides, including technologies that provide a quick kill for topside treatment and others that can sustain antimicrobial efficacy in downhole environments, are available to the industry.

Some examples of microbial control solutions for near wellbore efficacy include glutaraldehyde and tetrakis (hydroxymethyl) phosphonium sulfate (THPS), while tris (hydroxymethyl) nitromethane, dimethyloxazolidine, and (chloroallyl)-triaza-azoniaadamantane chloride provide extended long-term protection. These biocides can provide protection for weeks to months.

Myth 2: An oxidizing biocide is sufficient for treatment

The rapid results of oxidizers are impressive and hard to ignore. The use of ClO₂ has increased in the past five years due to the lure of its quick-kill qualities. However, the benefits stop topside. Operators are setting a dangerous precedent for themselves by using oxidizers alone, as the performance of these biocides end following the initial topside kill, thereby making the well, reservoir and produced water susceptible to microbial contamination.

Myth 3: Save more money by not using a biocide

In the current economic condition, operators are evaluating all cost-saving options, including removing microbial control programs from operations entirely. While this provides short-term cost savings, untreated systems are open to uncontrolled microbial contamination, which can cause costly souring, corrosion and plugging issues throughout the life cycle of the well.

So operators may save an initial investment by not purchasing biocides, but they also may end up spending far more money in the long term by having to deal with the fallout of sour gas, cleaning costs and equipment failure.

Myth 4: No long-lasting biocide, nor perhaps any treatment, is needed in extreme temperatures

This is one of the more misunderstood myths circulating today as it has some basis in science and has thus dissuaded many producers from investing in an integrated biocide program. But the truth is more complicated than the headlines suggest.

Certain types of bacteria known as thermophiles are able to grow in environments up to 120 C (248 F). Recently, some researchers have reported that adding a biocide to fracturing fluid isn’t always necessary because temperatures may exceed 120 C at the depths that biocide- treated water is injected. However, there is a temperature gradient stretching from surface operations/equipment to the wellbore that does not necessarily exceed the thermophilic temperature survival threshold even in shale plays, in which the extreme downhole environment is greater than 120 C. Bacteria will begin to thrive in these cooler niches, possibly resulting in microbially induced corrosion, equipment plugging and souring.

Myth 5: ClO₂ is a cost-efficient solution

When evaluating the cost of a biocide program, it is important to distinguish between cost per unit and total cost to treat. Despite ClO₂’s perceived low cost, typical non-oxidizing oil and gas biocides such as THPS, glutaraldehyde and glut/quat blends can help save 10% to 50% on an annual basis. Effective microbial control can prevent costs related to compatibility issues, sweetening soured hydrocarbons, replacing corroded equipment or removing biofilm.

As oil and gas operators continue to adjust to fluctuations in the market, it is important to have confidence that they are using the right biocide program. Microbial control expertise, a broad product portfolio and advanced testing capabilities allow a biocide supplier to design an integrated microbial control program that helps operators unearth oil and gas that is ready to be delivered to refiners as quickly and cost-effectively as possible.