Graphene's star is rising as a material that could become essential to efficient, environmentally sound oil production. Rice University researchers are taking advantage of graphene's outstanding strength, light weight and solubility to enhance fluids used to drill oil wells.
The Rice University
lab of chemist James Tour and scientists at M-I SWACO, a Texas-based supplier
of drilling fluids and subsidiary of oil-services provider Schlumberger, have
produced functionalized graphene oxide to alleviate the clogging of
oil-producing pores in newly drilled wells.
patented technique took a step closer to commercialization with the publication
of new research this month in the American Chemical Society journalApplied
Materials and Interfaces. Graphene is a one-atom-thick sheet of
carbon that won its discoverers a Nobel Prize last year.
relationship with M-I SWACO began more than two years ago when the company
funded the lab's follow-up to research that produced the first graphene
additives for drilling muds. With traditional clay-enhanced muds, differential
pressure forms a filter cake, which both keeps the oil from flowing out and
drilling fluids from invading the tiny, oil-producing pores.
drill bit is removed and drilling fluid displaced, the formation oil forces
remnants of the filter cake out of the pores as the well begins to produce. But
sometimes the clay won't budge, and the well's productivity is reduced.
Group discovered that microscopic, pliable flakes of graphene can form a
thinner, lighter filter cake. When they encounter a pore, the flakes fold in
upon themselves, and look something like starfish sucked into a hole. But when
well pressure is relieved, the flakes are pushed back out by the oil.
was known two years ago. Since then, Tour and a research team led by Dmitry
Kosynkin, a former Rice postdoctoral associate and now a petroleum engineer at
Saudi Aramco, have been fine-tuning the materials.
a few issues that needed to be dealt with. First, pristine graphene is hard to
disperse in water, so it is unsuitable for water-based muds. Graphene oxide
(GO) turned out to be much more soluble in fresh water, but tended to coagulate
solution was to "esterify" GO flakes with alcohol. "It's a
simple, one-step reaction," says Tour, Rice's T.T. and W.F. Chao Chair in
Chemistry, as well as a professor of mechanical engineering and materials
science and of computer science. "Graphene oxide functionalized with
alcohol works much better because it doesn't precipitate in the presence of
salts. There's nothing exotic about it."
In a series
of standard American Petroleum Institute tests, the team found the best mix of
functionalized GO to be a combination of large flakes and powdered GO for
reinforcement. A mud with 2-percent functionalized GO formed a filter cake an
average of 22 micrometers wide – substantially smaller than the 278-micrometer
cake formed by traditional muds. GO blocked pores many times smaller than the
flakes' original diameter by folding.
making the filter cake much thinner, which would give a drill bit more room to
turn, the Rice mud contained less than half as many suspended solids; this also
would make drilling more efficient, as well as more environmentally friendly.
Tour and Andreas Lüttge, a Rice professor of Earth science and chemistry,
reported last year that GO is reduced to graphite – the material found in pencil lead and a
natural mineral – by common bacteria.
most exciting aspect is the ability to modify the GO nanoparticle with a
variety of functionalities," says James Friedheim, corporate director of
fluids research and development at M-I SWACO and a co-author of the research.
"Therefore, we can 'dial in' our application by picking the right organic
chemistry that will suit the purpose. The trick is just choosing the right chemistry
for the right purpose."
still a lot to be worked out," Tour says. "We're looking at the
rheological properties, the changes in viscosity under shear. In other words,
we want to know how viscous this becomes as it goes through a drill head,
because that also has implications for efficiency."
help graphene live up to its commercial promise, Tour says. "Everybody
thinks of graphene in electronics or in composites, but this would be a use for
large amounts of graphene, and it could happen soon," he asserts.
agrees. "With the team we currently have assembled, Jim Tour's group and
some development scientists at M-I SWACO, I am confident that we are close to
both technical and commercial success."