Researchers send molecules on assignment

‘Reporters’ Look for Leftovers

The petroleum industry is increasingly adept in devising new and innovative technology to recover the significant volumes of hydrocarbons that commonly remain in produced reservoirs.

In some instances, these “leftovers” may exceed 50 percent of the original volume.

Today, researchers have made considerable headway in an effort designed to send an unusual breed of reporter downhole and into the reservoir that later will return to the surface to be interrogated about what it saw – kind of like a spy returning from a clandestine assignment.

Don’t roll your eyes.

It may sound far out, but it’s for real.

Informally dubbed nano-reporters, these hydrophilic carbon clusters incorporate signaling molecules engineered to detect oil, water, certain chemicals, pressure, etc.

The structures are dated molecularly via chemical bar-coding and, upon recovery following a tour of the reservoir, they have a story to tell.

‘Keeping Them Small’

Nano-reporters are the smallest “next big thing” the industry has seen.

“The key is keeping them small, embedding all this information, the molecular coding, the ability to gather information and do that in a nano-sized entity that’s somewhere smaller than 300 nanometers (one nanometer equals one-billionth of a meter), and particularly smaller than 100 nanometers,” said Jim Tour at Rice University, “so they never plug up any orifices and can go into the smallest crevices.”

Tour, who is a professor of chemistry, computer, mechanical engineering and materials science at the Smalley Institute for Nanoscale Science and Technology (SINST) at Rice, is principal investigator for the nano-reporter research project.

The project is sponsored by the Advanced Energy Consortium (AEC), which is funding a comprehensive research program in the field of nanotechnology. The consortium is managed by the Bureau of Economic Geology at the University of Texas at Austin, and the SINST serves as a key technical partner.

The nano-reporters are being made and lab-tested at Rice where Tour is working alongside fellow profs Michael Wong and Mason Tomson from the chemical and environmental engineering departments, respectively.

Tour noted the AEC has a number of partner companies and said his group is partnering closely with Shell on the nano-reporter program.

The MO of these esoteric nano structures can be summarized quite simply:

“When this nano-sized entity goes downhole it will release the signaling molecules depending on what it sees,” Tour said. “Then when the nano-reporters come back up we’ll interrogate them and, based on the amount of material lost or retained, we’ll be able to assess how much oil they saw versus water.”

Using kinetics, it can be determined in the lab how much oil a cluster must have seen to be devoid of perhaps 98 percent of these molecules.

Getting a Complete Picture

Regarding the location of the oil in the reservoir, one only has to look at the bar code on the carbon clusters to determine if they were pumped in perhaps two years ago and just now surfacing.

“The time spent downhole will give us an assessment of how far away they were in what they saw,” Tour said. “Some may come up after a month, but they didn’t traverse as far and didn’t see as much oil – this begins to give the topology of what’s down there.

“Depending on what other molecules are there, you can do other things, like detecting how much hydrogen sulfide they saw, the pressure they saw,” he added.

Tour said the idea is to put clusters down weekly throughout the life of the well – say, in soda pop can-size volumes – to have constant reporting of what’s going on in the reservoir and what’s changing.

“They’re constantly coming up, so every week, or how often you can, you can take a little cup full of the mixture coming up from the production hole and in near real time analyze this,” Tour said.

“Technically all you have to see is one nano-reporter, but you don’t like to do that,” he said. “You like to get an average of what they all saw.

“You interrogate and use some spectroscopy, and you look at tens of thousands of them in near real time,” Tour noted.

“You get information on what they’re seeing, and you see changes over the life of the well,” he said, “which means we won’t leave as much (hydrocarbons) downhole.”

Eco-Friendly

More good news: This technology provides no ammunition to the environmental activist community.

“We looked at the toxicity of these things in cells in mammals in collaboration with the medical center in a number of different studies,” Tour noted.

“We’re using things similar to this for drug delivery,” he said, “and that’s how we could move on this so swiftly – if it’s the same thing being used for drug delivery, it has to be non-toxic.”

Nano-reporters inarguably could be a magic bullet of sorts to help operators tap into previously undetected volumes of hydrocarbons.

Tour cautioned, however, that even if the nano-reporters are injected early in the life of a well, it could take as long as several months or even several years for an operator to acquire the assessment needed.

And don’t look for these minuscule spies to appear soon in a reservoir near you.

They’re just now being tested in core plug samples.

“It’s at least a couple of years away before we start pumping these downhole,” Tour said. “It’s still basic research, not applied.

“But the energy sector is very aggressive,” he noted, “and if they get something they want to start injecting it.

“So I might be pleasantly surprised.”

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