October 2021

What's new in Production

Functionalized surfaces
Willard C. (Bill) Capdevielle, P.E. / Contributing Editor

Continuing on my quest to introduce various nanotechnologies to the oil and gas community, I would like to bring you the power of functionalized surfaces. This area of nanotechnology involves modifying substrate surfaces on the nanoscale, either with specially created patterns or unique chemistries through the attachment and integration of nanoparticles. While this has been understood and played around with in research labs and universities, implementing this technology at large scales has proven to be cost-prohibitive and logistically challenging.

In our business, we deal with two categories of liquids: hydrocarbons and water. Ultimately, of course, we like to keep them in separate streams—and move them from one point to another as efficiently as possible. But in practice, they are often found together.

Many of you will be familiar with a phenomenon called wetting. When a surface tends to attract a liquid, such that the liquid wets to surface, that surface is called liquid-wet. If the liquid is water, then the surface is water-wet. Another term that can be used to describe this condition is hydrophilic. If the surface repels the water, then it is hydrophobic. The common measure of the -phylicity or -phobicity of a surface is the contact angle between the surface and the liquid, as shown in Fig. 1.

Fig. 1. Hydrophilic and hydrophobic contact angles
Fig. 1. Hydrophilic and hydrophobic contact angles

I also should mention that surfaces can be functionalized to be phylic or phobic to oil (oleophilic or oleophobic). Similarly, surfaces can be functionalized to be phylic or phobic to both oil and water omniphilic or omniphobic. This column will deal primarily with the water side of things. Even though we may primarily care most about the harmful effects of water on production operations, having the option to also repel oil-based liquids at the same time opens up new ideas for saving money and protecting equipment

Here are a few oil and gas industry applications.

Corrosion protection. Corrosion is a huge problem in oil and gas production. Its prevention and mitigation comprise a significant portion of capital and operating expenses. By applying a surface treatment that repels and is impervious to all corrosive fluids, then corrosion can be mitigated, because the fluid doesn’t contact the underlying substrate. An example of this is a technology called Anhydra, first developed by Oceanit Laboratories for the U.S Navy, to allow for long-term active corrosion protection of ships and equipment at sea.

Flow enhancement. The pressure drop within a transport pipeline (in laminar flow) is proportional to the friction factor, pipe length, and flowrate, and inversely proportional to the diameter of the pipe. With a surface that has been functionalized to be repellent to that fluid, the overall friction factor can be greatly reduced, as the liquid is able to glide across the pipeline interior surface without sticking or causing turbulence. Field measurements have shown that friction losses due to drag can be reduced simply through manipulation of wetting—by up to 30%. This means that you can reduce the initial pressure required by up to 30%, or increase your throughput by up to 30% without needing to invest in significant pipeline replacement, simply through careful manipulation of the pipeline internal surface. Figure 2 captures the flow performance of hydrophilic versus hydrophobic flow.

Fig. 2. Hydrophilic vs. hydrophobic flow.
Fig. 2. Hydrophilic vs. hydrophobic flow.

Now, this 30% factor is only for laminar flow of fluids (liquids and gases). At this point in time, I am uncertain of the effect of surface functionalization in other flow regimes. I am also uncertain of how it affects the onset of various other issues that affect flow characteristics, such as liquid holdup and slugging in producing wells.

It is not hard to also envision the effect of reducing pipeline pressure drop on decarbonization efforts—less wear and tear on pumps and compressors can easily lead to significantly lowered maintenance costs, and reduced usage on individual compressors can lead to greatly lowered CO2 emissions.

The only expense is the (capital) cost of the surface functionalization. No flow enhancement chemicals are required. Building off years of research and development efforts with both public and private customers, Oceanit Laboratories has a turnkey surface Functionalization technology that can be applied

And once again, thinking small has the potential to yield values to upstream oil and gas operations.

About the Authors
Willard C. (Bill) Capdevielle, P.E.
Contributing Editor
Willard C. (Bill) Capdevielle, P.E. has 45 years of upstream industry experience. He has held various technical and managerial positions and is retired from both Mobil Oil and Hess. Bill has spent equal portions of his career supporting producing operations, in upstream technology centers, and in capital project support.
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