Extracting the Benefits of Nanotechnology for the Oil Industry

Ramanan Krishnamoorti, University of Houston

While a great deal of hype has surrounded the advances in nanoscience and nanotechnology, in many application areas such as biomedical, space, and information, the promise of commercial success is not guaranteed nor likely to occur for 5 to 10 years. But nanotechnology is an enabler that has proved to be a game changer for exploiting fossil-based fuels and, over the next 30 years, will be a critical component in developing fossil-based energy technologies.

Nanotechnology represents the development and application of materials, methods, and devices in which critical length scale is on the order of 1–100 nm and where critical functionality is not a direct manifestation of the atomic or macroscale properties. Specifically, three broad areas in which such unprecedented properties of the materials will be significant enablers are materials, tools, and devices. These have exploited the unique combinations of mechanical, thermal, electronic, optical, magnetic, and chemical properties observed at these length scales.

Refining and conversion of fossil fuels have been pioneering areas for the development and maturation of nanotechnology principles for the past 20 years. For example, the development of mesoporous catalyst materials such as MCM-41 significantly changed downstream refining. Such applications of nanotechnology are anticipated to continue developing, with the focus shifting to heavy oil and tight gas applications, which will require the physical integration of at least some rudimentary downstream processing with drilling. Developing efficient chemical methods to remove impurities from heavy oil, efficiently implementing gas-to-liquids (GTL) technologies for stranded gas, and exploiting methane hydrates efficiently will continue to build on this extensive knowledge base of the use of nanocatalysts and other downstream applications of nanotechnology.

Interestingly, oil exploration has used nanotechnology in drilling muds for the past 50 years. The nanoparticles in drilling muds are made of clays and are naturally occurring 1-nm-thick discs of aluminosilicates. These nanoparticles exhibit extraordinary rheological properties in water and oil. But the most recent and promising successes of nanotechnology in drilling are likely to occur with synthetic nanoparticles, where size, shape, and chemical interactions are carefully controlled.

Structural Nanomaterials

Improved lightweight rugged structural materials are crucial for many applications, including weight reduction of offshore platforms, energy-efficient transportation vessels, and improved and better-performing drilling parts. Structural materials can be enhanced significantly by nanotechnology with the addition of engineered nanoparticles and hierarchical strategies inspired and implemented by nanoparticles. The large interfacial area afforded by, and the nanoconfinement resulting from, well-dispersed nanoparticles leads to fundamental property changes in matrix metal, ceramic, and plastic and to a significant alteration of the paradigm of filled systems. These are especially prominent for anisotropic nanoparticles such as rodike nanotubes (e.g., single-walled carbon nanotubes) and disklike clays (e.g., montmorillonite).

For instance, the implementation of filled polymer systems traditionally has been associated with a tradeoff between stiffness and toughness with increased filler loading. Such tradeoffs are defied by the emerging class of polymer nanocomposites, with the most prominent example being that of the nylon-6-based clay nanocomposite pioneered by Toyota during the past 15 years. With as much as 5 wt% of added clay, the nylon nanocomposites demonstrated a doubling of the modulus and an impact strength that was virtually unchanged from that of the matrix polymer. Additional benefits that emerged from such a nanocomposite included a reduction in the coefficient of thermal expansion and a decrease in water-vapor permeability, rendering these nanocomposites extremely versatile and attractive alternatives despite the increased cost.

Elastomers are critical components for drilling under the extreme conditions of temperature and pressure, and developing stronger, tougher, and more inert and reliable materials for deepwater and ultradeepwater drilling is critical. By engineering elastomer nanocomposites with carbon nanotubes and layered silicates, ensuring mixing at the molecular level and wrapping and interpenetrating network structures, a new class of elastomers has been developed that is strong, tough, environmentally resistant, and, most important, self-sensing for structural-health monitoring. Moreover, by using small quantities of nanoparticles to achieve materials with compressive moduli comparable to the traditional elastomers used in such applications, a significant weight reduction occurs with these engineered nanocomposites. Finally, such nanocomposites have the potential to be shape-memory materials, with the triggering of the shape change occurring as a result of changes in temperature, infrared light, electrical current, or pH. Such shape memory-soft materials would help define a new class of smart materials (e.g., as actuators) that could be used downhole or in surface applications.

Fig. 1 - Structural materials can be enhanced significantly by nanotechnology

Advanced drilling fluids based on polymers that are physically or chemically associated with nanoparticles along with amphiphilic surfactants or polymers have been developed as stimuli-sensitive materials. The mechanical and flow properties of these materials can be altered in response to a change in stimuli such as temperature, salinity, and pH, and these materials can be used in reservoir conformance, flooding, and completion fluids. Designing specific hydrophobic or hydrophilic character into such smart fluids, through the use of novel organic chemistry on the surface of high-surface-area functionalized nanoparticles, will significantly alter the mode of operating and organizing waterfloods and surfactant floods. Moreover, by tailoring the responsivity of these smart fluids, they can be used either to block or to increase the porosity and tortuosity of the formations where they are injected.

Engineered nanoparticles, and in particular, nanocrystalline materials, in combination with advanced drilling fluids, are likely to increase drilling speeds and decrease wear of drilling parts significantly. Additionally, the development of methods to control the incorporation and distribution of such nanocrystalline materials in metal matrices would lead to stronger and lighter-weight pipelines for transportation of oil and natural gas. These are likely to be especially important for the exploitation of stranded gas.

Sensors and Imaging

Because of the significant alterations in their optical, magnetic, and electrical properties (in comparison to their bulk analogs) along with their ability to form (electrically and/or geometrically) percolated structures at low volume fractions, nanomaterials make excellent tools for the development of sensors and the formation of imaging-contrast agents. Additionally, using the anisotropic nature of many nanoparticles, the percolation is a strong function of orientation, and, thus, for appropriately processed materials, highly anisotropic electrical and mechanical properties are observed in different directions.

Such nanomaterials, when combined with smart fluids, can be used as extremely sensitive sensors for temperature, pressure, and stress downhole under extreme conditions. Perhaps the most significant value as sensors results both from the ability to interrogate the parameters of interest (e.g., temperature, pressure, stress) without requiring contact and from the amplification of signals by use of unique optical signatures (such as absorption and fluorescence) of the nanoparticles as surrogate probes of the parameters of interest.

Similarly, when combined with significantly enhanced magnetic and spectroscopic probes and improved computational methods, nanoparticles have substantial potential as markers for imaging. By chemical modification, the nanoparticles preferentially segregate into different fluid regions or to the pores, allowing for improved sizing and characterization of the reservoir and the efficacy of sweep methods employed to enhance the recovery of oil by monitoring the flow of fluids and by real-time monitoring of the reservoir. The use of nanoparticles (as opposed to the macroscale analogs) for such imaging is crucial because of the size of the pores, the increased surface area of the nanoparticles, and the mobility associated with them. Finally, the increased sensitivity of the probes and the strength of the optical and spectroscopic signatures of the nanoparticles require only small amounts of nanoparticles, which could lead to the development of instrumentation and methods for evaluating small test holes that minimize the footprint of the drill and reduce drilling costs for exploratory wells.

Nanomembranes

The convergence of top-down and bottom-up synthesis that is typical of nanomaterials has led to the development of large-scale, lightweight, and sturdy nanomembranes. Inspired by the success of zeolites (materials capable of separating small gases such as oxygen and nitrogen) and the development of top-down and bottom-up synthetic methods, a new generation of nanomembrane materials is being developed and deployed for the separation of metal impurities in heavy oil and impurity gases in tight gas. By exploiting methods common in the microelectronics industry, the cost of manufacturing highly uniform and reproducible membranes is quite competitive. These nanomembranes will enhance the exploitation of tight gas significantly by providing efficient methods for removing impurities, separating gas streams, and enabling GTL production.

The three subtopics above provide a glimpse of the application of nanotechnology in the oil and gas industry that will complement its large-scale use in the refining and processing sectors. Some issues of concern include the uncertainty of the health effects of nanoparticles in general, the environmental effect of nanoparticles, the cost of deploying large quantities of nanoparticles for production applications, and the development of appropriate quantitative tools for the analytical and chemical characterization of nanoparticles. All of these issues are being pursued actively by the scientific and technological community and will be settled over the next few years. Clearly, the true exploitation of nanotechnology over the long term would be the harmonious integration of refining and environmental issues (such as CO2 sequestration) with drilling.

Ramanan Krishnamoorti is a professor of chemical and biomolecular engineering and chemistry at the U. of Houston. He is also currently the Associate Dean for Research in the Cullen College of Engineering at the U. of Houston. His research interests include structure/processing/property relations for multiphase polymers, with emphasis on biomaterials and nanotechnology, polymer crystallinity, thermodynamics and viscoelasticity of polymer blends and copolymers, structure and viscoelasticity of macro- and nanocomposites, and developing and understanding polymers for drug delivery and biomedical applications. Krishnamoorti has published more than 85 peer-reviewed journal articles and has two patents. He earned a PhD degree in chemical engineering from Princeton U.