Ros Davidson speaks with researchers at University of Texas’ Advanced Energy Consortium about how medical technologies are enabling “smart particles” and an MRI-like reservoir scanner
Perhaps now more than ever, there is a concerted push from the oil and gas industry to take in new technologies from other industrial sectors. In one such application, medical expertise is being transferred to the oilfield in new research coordinated by the University of Texas’ Bureau of Economic Geology in Austin. The researchers, backed by oil companies and including scientists at a number of other global universities, are looking to adapt smart particles the size of a grain of sand that could be used, for example, during fracking or in wellbore cement. They are also researching underground MRI-like imaging techniques which would allow them to “light up” a frack job, and developing a method of payload delivery using nanovehicles that could act like a time-release medication or release their contents when a certain chemical reaction takes place within the reservoir.
Why not? According to chemical engineer Jay Kipper and project manager Mohsen Ahmadian of the University’s Advanced Energy Consortium (AEC), these smart particles are computer chips about the size of a grain of sand. Their size and construction allows drillers to mix and inject them as part of conventional fracking fluid. “If you have smart dust and can throw it into a reservoir, you can do smarter things such as recover more hydrocarbons,” Kipper explains to InnovOil. The nanomaterial sensors, once injected, could measure temperature, pressure and chemical composition. What began as blue-sky research a few years ago has now progressed to the point at which lab and field tests are now occurring. The idea for the particles, originally came when Kipper and a colleague (AEC director Scott Tinker) attended a medical conference and heard about nanosensors which could be introduced into the human body: “We looked at each other and said, why not in the earth?” The scaled-down semiconductor sensors contain a battery, coding and flash memory, and measure pH, temperature, pressure and resistivity. The base is an integrated silicon transistor chip, while the battery is based on a proprietary chemistry that can withstand temperatures of about 125°C and pressure up to 7,500 psi. All of this is housed in an alloy package. The first generation being developed measure 8mm3 in size, but the team expects the next generation to be further miniaturised down to 1mm3, says Ahmadian. The particles could be injected into a fracture network along with the frack fluid, or they could be introduced via coil-tubing or tethers. The current particles would be able to take about 1,000 measurements during the lifetime of a battery, allowing for several deployments over a period of weeks. The battery can also be put to sleep to lengthen the time available on one charge. If the devices are used as a ‘smart proppant’, they would return to the surface in produced fluids, and would then be read and recharged wirelessly. Currently, they do not have the capability for communication while downhole, but the AEC is researching ways that this could be done. Likewise, if used in cement, they would remain in place over the well lifetime and could communicate information regarding cement integrity. However, this would require a different read-out mechanism and way of recharging – another area the team is exploring. Research remains in the development phase, although laboratory testing has now been concluded, and field testing will occur within the next couple of months in a wellbore in France. So far, the cost of the smart dust is relatively high, but when produced in volume, Ahmadian believes that it will become pennies per device. Even so, the cost is justified in the technology’s ability to offer data and information that was previously unavailable. “Without smart particles, you’re not currently getting those readings,” Kipper says.
Contrast agents Separate research is also being done on producing an MRI-like reading within a fracture network. A contrast agent is used so that an area of interest can be highlighted and analysed. “We can do a smarter frack job,” says Kipper. “It’s like having a set of eyes downhole.” The researchers say that this could be used to answer questions in planning stages – such as where a fracture should occur – or in post-frack analysis to determine where it did occur. Carbon-based conductive materials and iron oxide-based magnetic materials are used. A transmitter in the injection well would then pass a signal through the reservoir (and contrast medium) to a receiver array in the production well, producing an image in a manner not unlike an MRI machine. The contrast agents currently cost a few cents per pound, and should also become cheaper as the technique develops. The technique has been demonstrated in the laboratory with computer modelling, and a pilot study is currently being conducted in an oilfield not far from the university campus. Partial field results have been produced and, according to the team, so far they look very good and are in line with expectations. In fact, results were published last year from a small-scale frack job, and the team plans to look at mapping concepts for hydraulic fracturing, waterflooding, Enhanced oil recovery (EOR), and interwell reservoir characterisation applications. In a third area of research based on ideas borrowed from medical applications, payload could be delivered precisely to an area of interest in a wellbore or in reservoir. Material for acid stimulation, for example, could be encapsulated so that the wellbore is protected and corrosion is reduced. The capsule could then be time-released, or it could release its content when a controlled or known chemical reaction takes place. EOR materials could thus be delivered highly accurately using this method. For example, surfactants, detergents or polymers could be delivered to block a high-permeability zone, so that fluids are diverted to a low permeability zone. With a number of very promising pilots on the horizon or already underway, the AEC is all set for a busy 2017 – a year which will hopefully bring even more opportunities to ask – “Why not in the earth?”