E&P Case Study: Inline Static Mixer Improves Chemical Results

Sometimes the seeds of innovation are sown almost by accident.

The Tellerus inline static mixer started with a seemingly happenstance view of a gelatinous mass of chemical buildup deposited on the outside diameter of the top 20 to 30 joints of tubing pulled from a well on a freezing-cold Montana December morning. It led to the creation of a simple yet useful tool that would increase the effectiveness of treatment chemicals so their use could be reduced by 40% to 80%.

At the time of this discovery in 2005, producers were looking to improve the effectiveness of their chemicals—and in today’s world what was an interest has turned into necessity. As chemical treatments can consume up to 10% or more of the cost of production, a device that could reduce the amount needed by mixing them more completely into the flow could save tens of thousands of dollars per year across just a few wells.

However, most producers lack the expertise to evaluate chemical costs themselves. Instead, they rely on the supplier to decide the mix and dosage—and few chemical suppliers are interested in finding a way to sell less product.

Development and application of the Tellerus inline static mixer came in two phases:

1. Phase 1 concentrated on a more effective mix; and
2. Phase 2 discovered that the improved mix could actually reduce the amount of chemicals needed.

Testing in Montana

Tests showed that the Montana tubing deposit mostly consisted of the treatment chemicals, combined with a bit of the scale and iron sulfide they were intended to treat. From this sample, it was obvious that the majority of chemicals injected never reached their destination, so they could not accomplish their purpose.

Frequent failures of the fields electric submersible pumps (ESPs) led credence to the idea that chemicals were not as effective as they needed to be.

This remote field consisted of stripper wells producing 500 bbl/d to 4,000 bbl/d with a massive 96% water cut. Most producers used ESPs that had to be replaced every 3.5 years at a cost ranging from $75,000 to $125,000 each, a huge cost for such a small amount of sellable product.

There needed to be some way to get the chemicals to blend better with the fluid/carrier stream they were injected into.

The team experimented with the insertion of an inline static mixer into the side stream flow, at the point of chemical injection right before it’s discharged into the casing, then dropping into the fluid column.

The mixer’s purpose would be to create a consistent condition of mass transfer according to a Reynolds number value. The resulting turbulence in the pipe would induce a mixing action similar to a blender turning an assortment of fruits into a smoothie.

For decades, other industries have used static mixers for the same purpose, so it was almost surprising that it had never been tried in the upstream oil and gas sector.

Thus, Tellerus was formed in 2007. The company’s name is a variation on the Greek word for earth (the actual Greek word was already in use) for the purpose of creating and testing this static mixer idea. 

Phase 1: creating and testing

Any mixer design would need to be flexible enough to accommodate the fact that various chemical formulations could encounter either a single phase or three-phase fluid mass. A single phase would involve oil alone, with a small amount of produced water. Three-phase conditions would treat gassy fluids containing perhaps a 50% water/oil mix.

Tellerus created a mixer containing baffles and vanes inside the pipe. These elements would roil the fluid, creating the needed Reynolds effect to completely mix chemicals and fluid in the pipe below the mixer.

The earliest model used carbon steel due to its lower cost, but in field tests these devices succumbed to corrosion within a few months. The turbulence caused dissolved H₂S and CO₂ to bubble out, which is what caused the problems.

A switch to stainless steel solved the issue. In more than 10 years since the switch to stainless, regular inspections have revealed almost no leaks or replacements, even in harsh conditions.

Further design improvements have driven up efficiency and reduced the amount of welding required. Welded or bolted flange fittings are available, and most components are threaded for easy field installation, inspection, documentation and repair. Some prefer welded joints for pressures above 125 psi. Mixers come in lengths ranging from 2 ft to 8 ft.

Tests began in 2008 in the basin where the problem was first observed. Mixers were installed in the treatment side stream of wells where ESPs failed at the 3.5-year cycle stated above.

In 2020, 12 years after the installation, the ESPs on those wells are still in operation, never having been replaced during that time.

Phase 2: reducing chemical injection amounts

In Phase 1 the static mixer reduced pump replacement costs for the clients. But during the 2015 downturn, the Phase 1 clients began to look for further production costs cuts. Producers from the original tests asked Tellerus to evaluate results of cutting back on scale and corrosion-reducing chemicals. The operator’s goal was to slash chemical costs by up to 50%.

Tellerus began by reducing injection rates to 60% of previous levels with the same chemical mix. Five years later, there have been no operating issues with corrosion or scale since the change.

Another set of leases under test all used various emulsion breakers to separate and clean up heavy black oil (18º API), cold (55ºF). The chemical use rates were excessively high but effective. The objective was to reduce chemical injections and expenses at these five leases by 40% to 80%. The inline mixer did just that and vastly improved predictable oil delivery to the sales tanks, even in cold winter conditions of the northern Rockies.

Various other applications are successfully using the mixing tools to improve chemical performance of reverse breakers and water clarifiers for better water/oil separation within high volume water discharge systems.

Trials have since been expanded to include other treatments such as multifunction inhibitors, with similar success.

Conclusion

Today’s headline-grabbing developments are mostly in software and electronics, but occasionally a purely mechanical invention like a piece of pipe with turbulence-inducing baffles is also worth noting.

In 2019, the National Association of Corrosion Engineers (NACE) listed the Tellerus mixer among its finalists for its Corrosion Innovation Award, an international competition. The technology department of a major E&P company is also considering adopting this design.

The Tellerus inline static mixer device reduces the amount of chemicals needed by 40% to 80% and extends the life of protected equipment by, in some cases, more than a decade. While testing has been mostly done on smaller wells, the Reynolds number equations indicate that it should find similar success on larger wells and bigger fields.