First, a fun fact: The prefix “nano” comes from the Greek language, a masculine form of the word “nanna,” which literally means “little aunt” or “little old lady.” Later it came to mean “dwarf,” at first a very small person, then a very small anything. At an international chemical conference in 1947, the word was adopted as a prefix for 10-9 part of something, or a billionth, as in nanometer or nanosecond.
The definition of “nanotechnology” is not based on size per se, although it does involve very tiny weights and distances, but on the manipulation of substances at an atomic or molecular scale. The word was coined in the 1970s, but it wasn’t until the invention of the scanning tunneling microscope in the early 1980s that the subject drew widespread attention and research. The discovery of fullerenes—hollow spheres or tubes of carbon atoms—in the mid-1980s initiated the first serious push toward practical application of nanotech.
Governments have been involved from the beginning. In the U.S., the National Nanotechnology Initiative (NNI) coordinates R&D research among 20 governmental departments and independent agencies. Since inception of the NNI, the U.S. has spent some $3.7 billion on various nanotech projects. Privately funded industry and academic groups have also participated.
Nanoparticles in the oil field. The Advanced Energy Consortium (AEC) was formed in 2008, with the very specific goal of developing “intelligent subsurface micro- and nano-sensors that can be injected into oil and gas reservoirs to help characterize the space in three dimensions, and improve the recovery of existing and new hydrocarbon resources.” AEC is comprised of The University of Texas’ Bureau of Economic Geology and Rice University’s Smalley Institute for Nanoscale Science and Technology, along with the participation of major firms Shell, Total, Petrobras, BP, Schlumberger, BG Group, Repsol and Statoil. In addition, some 30 universities, worldwide, contribute with academics and research.
A lot of the interest for petroleum has centered around graphene. This crystalline substance consists of a layer of carbon atoms in a flat sheet. Graphite is made of millions or billions of graphene sheets. When it occurs in a single layer, one atom thick, graphene is the thinnest material in the world, the closest thing you’ll find to a two-dimensional object. It is also the most conductive substance in the world, holding great potential in high-speed, low-power supercomputing. Because they are flat sheets, the edges of the graphene particles are wide open for adding other kinds of atoms and modifying its chemical properties.
As highly specialized as it is, several companies have begun manufacturing graphene for research, using various techniques. The oldest and simplest way to make graphene was the “scotch tape” method, picking up a layer of graphite with sticky tape, and repeatedly folding and peeling it to isolate thinner and thinner layers. More efficient techniques use a substrate of carbon and silicone, heating it to remove the silicon atoms, or heating carbon on a copper surface, which catalyzes graphene formation. Also, when you take tubular forms of fullerene, nanotubes, you can use a chemical process to split them longitudinally to form “graphene ribbons.”
Interrogating the informers. When an oil field is past initial production, the overriding question is: How much oil is left behind? Which fields are candidates for further recovery? Nanoparticles can be used as “reporters” downhole. Carbon black with specialized nanoparticle add-ins can be pumped downhole, and then recovered and “interrogated,” to find out how much oil the particles “saw” while there. The next generation of nanoreporters will not only tell how much oil they encountered, but where along the residence time, downhole, this occurred. Some particles can be configured as H2S detectors, to determine how sour the left-behind oil might be.
What about the next step, not only seeing the oil in the formation, but helping with recovery? AEC is hard at work in this direction, although few patents have been filed, and so there are a lot of hints without hard data. However, the work is very intriguing. One approach is to inject nanoparticles that are both hydrophobic and hydrophilic (water-resisting and water-loving), depending on temperature and pressure. That is, at low temperatures, they would stay in the aqueous phase, and at high temperature, they’d go in to the oil phase. With traditional surfactants, you have to remove them from the oil after it is produced, adding to trouble and cost. A new generation of surfactants might be made self-separating, moving back to the aqueous phase, once it reaches ambient temperatures and pressures.
Also nanoparticles can coagulate at the oil-water interface. If you have probes that can detect where these nanoparticles are amassing, then you have a clearer picture of the interface.
There is also progress in using nanotech to create conductive oil-based muds. This would allow LWD, even in shale where you can’t use water-based muds. LWD with oil-based muds is much more difficult, but nanoparticles can be added in fairly small amounts to increase the conductivity of the mud by orders of magnitude.
CO2 capture. Another new carbon nanomaterial (so new it is apparently not yet named), developed by a team led by Rice professor James Tour, has the property of absorbing nearly its weight in CO2 at elevated pressure, then releasing it when pressure drops. It is highly efficient at absorbing CO2, while not taking up natural gas. This creates the potential for economical removal of CO2 directly at the wellhead—highly significant, when you consider that many gas wells produce from 20% to as much as 70% CO2, along with natural gas.
Oil companies have shown great interest, because of the need for gas separation offshore, where traditional membrane-separation techniques require footprints much too large. Nanoparticles definitely lend themselves to small footprints.