Dissolvable technology has been an evolving success story — innovation answering necessity in an industry never short of challenges. Today, dissolving plugs are a frequent if not typical component of most well completions, in all wellbore or downhole environments. Dissolvable plugs have proven to be particularly effective in long laterals with higher stage density. In fact, a report by Stratview Research predicts that the global dissolvable frac plugs market is likely to reach $1,178.8 million in 2024, with the Americas.
“Inevitable” may be a more appropriate word than “effective.” As operators drill increasingly longer laterals requiring additional stages, dissolvable plugs are becoming a necessity, since additional depth increases difficulty of drill out. With the challenges posed by horizontal sections, producers have quickly refined and made great technological strides in less than a decade since dissolvables first emerged in the marketplace.
Known for being a tight reservoir, the Barnett Shale was a crucible for innovation in hydraulic fracturing. In the early 2000s when production began a sharp uptick, sliding-sleeve technology was the most popular method for completions. It featured a progressive ball-seat system in which successively larger balls were dropped to activate a seat, opening up the ports for hydraulic fracturing.
By this time, composite plugs had entered the picture. While a definite improvement over earlier cast-iron plug technology, the design still featured cast-iron slips that were difficult to drill out and remove from the wellbore. The coiled tubing procedure required for cleanout was extremely expensive — a significant portion of total completion budgets. In addition, the process was problematic, risky and time-intensive. The notion of a plug that would simply vanish, taking all of these problems with it, was not yet a tangible goal.
As operator use of composite plugs increased over time, it exposed some drawbacks to sliding-sleeve technology. Sometimes, the high pressure involved in the process would lodge the balls into the seats, requiring drillout.
In response, Magnum Oil Tools developed a dissolvable thermoplastic ball, which revolutionized sliding-sleeve technology. The inevitable next step was the dissolvable plug. Magnum’s prototype passed American Petroleum Institute inspection on its first test and quickly went into field trials. Within six months, the company had commercialized a product that was in high market demand.
An Early Competitive Advantage
Chemistry and temperature are two of the primary variables that determine the right dissolvable material composition for any given application. Most alloys used in today’s dissolvable plugs are magnesium-based, which requires that an operator know in detail the chemistry of the well fluid in order to predictably estimate how long it will take for that plug to dissolve.
However, downhole chemistry is never constant. It varies dramatically from the vertical section to the heel, and from there to the toe of the lateral. It can be different from one well to the next, even on a multi-well pad. It’s affected by the original water source and the fluid being pumped into the well. With so many variables, it’s complicated to predict time to plug dissolution.
By contrast, the commercial iteration of Magnum’s initial dissolvable prototype, called the Magnum Vanishing Plug™ or MVP, featured a thermoplastic material which dissolves according to the downhole temperature, not the chemistry.
The MVP, which established consistency and early market dominance, was a true industry disruptor as it proved the viability of the dissolvable plug proposition. When the product launched in 2014, operator demand was high for developments that could increase speed to production, making the advent of dissolvable technology perhaps the most significant advancement since the introduction of horizontal drilling. The potential of dissolvable plugs to ultimately eliminate the need for coiled tubing further justified their economic case.
Since then, plug technology and well services providers have continued to innovate new ways to increase production efficiency. The cost of producing a well today is approximately 60 percent of what it cost in 2014. The price tag for dissolvables has also dropped considerably, further promoting their appeal and acceptance industry-wide — or almost.
The Permian Problem, Solved
Since 2013, the Permian Basin has been one of the world’s busiest and most lucrative shale plays. However, while exceptionally effective at temperatures above 175°F, the industry’s original dissolvable plug was not ideally suited for the relatively lower-temperature environment of the Permian.
In light of this challenge, Nine Energy Service, which purchased Magnum Oil Tools in 2018, combined its engineering expertise with Magnum’s material knowledge to create a reliable dissolvable plug suitable for all temperature and salinity applications. The resulting technology, the Stinger™ Dissolvable Plug, achieves this goal and eliminates the need for a mandrel by using a wedge component to set and hold pressure.
Six years after dissolvable technology became commercially available, the industry now has access to a plug with proven ability to convey to depth; anchor, seal, and deploy from the setting sequence; properly act as a barrier during multi-stage stimulation; and predictably degrade across a full range of wellbore characteristics.
Making Sustainable Profitable
Another advantage to dissolvable plugs is their ability to reduce carbon emission intensity in a scalable way that can be applied on a per-well basis. According to a recent environmental impact study by Environmental Resources Management, a leading global provider of environmental, health, safety, risk, and social consulting services, there is a significant and immediate reduction in greenhouse gas emissions when using a dissolvable plug versus a composite plug.
Assuming a three-day coil tubing cleanout run, dissolvables reduce carbon footprint by 18 percent or about 13.3 metric tons of CO2e. Dissolvable plugs that can circumvent intervention entirely reduce carbon footprint by 91 percent, or roughly 67.3 metric tons of CO2e, over composites. On a six-well pad, this eliminates approximately 404 metric tons of CO2e, which equates to taking 84 cars off the road.
By improving site emissions, dissolvable plugs contribute to regulatory compliance. They also increase rate of return, as eliminating coiled tubing can save operators as much as 24 days per six-well pad in drillout time, reducing associated time, safety risks and service costs.
Innovations for 2020 and Beyond
What’s next for dissolvable plugs? Like personal computers, the trend is ever smaller. For example, the Stinger measures approximately 5.5 inches — much more compact than traditional dissolvables — which vastly reduces the amount of material to dissolve and debris to contend with.
As adoption of dissolvables becomes more pervasive, the need for expertise and support in selecting the right plug for specific wellbore conditions has expanded. With low-temperature magnesium plugs, for example, it’s necessary for manufacturers to maintain an adequate inventory of material to accommodate a wide variety of chemical fluid compositions. Smaller companies run the risk of overpromising and overleveraging with large inventories they can’t profitably maintain. Real engineering prowess is required to manage these variables and the risks that accompany them.
Savvy operators will heighten demand for means to generate detailed composition profiles including chloride content, suspended solids, and fluid content during pump down through return to surface to reveal the materials and ratios necessary for successful dissolution.
Dissolvable plugs have experienced a relatively quick evolution from innovative market disruptor to game-changing standard. The most recent incremental innovations have been a major factor in their acceptance. It’s a safe prediction that they are here to stay.