# Plenty of Room at the Bottom: Nanotechnology as Solution to an Old Issue in Enhanced Oil Recovery
## 5 Conclusions  
Throughout this review, it was presented and discussed how nanotechnology can be employed in EOR applications in order to increase the efficiency of existing recovery techniques. Many authors agree that nanotechnology allows EOR issues to be addressed from a novel point of view. The special features found at the nanoscale enhance the properties and/or performance of common processes/materials in many branches of science. EOR techniques are not exempt, so new ways to improve the traditional methods using nanotechnology are highly advisable. For the purposes of this analysis, it has been considered that the employment of nanotechnology in EOR can be divided into three subgroups, namely: the use of nanoparticles in the synthesis of nanofluids, the creation of nanoemulsions with surfactants or nanoparticles, and finally the use of active metals that can act as nanocatalysts for the in-situ upgrading of heavy oil cuts. Besides this classification, other different topics have been introduced, such as nanoparticle manufacturing methods and concerns about the impact that nanotechnology may have on the environment. Clearly, nanotechnology is a recent branch of science, and although much progress has been made lately, there are still many questions to be answered. This can be appreciated in the fact that most of the literature found on direct applications at the nanoscale is recent, and numerous investigations are still being carried out. For instance, there are several environmental concerns regarding the application of nanoparticles, not only in EOR but in all branches of science. How these particles affect our health and their long-term effect on the environment are still being investigated. Production methods are also currently being researched in order to produce smaller sizes as well as less variability in the size. Among the possible uses in EOR, the employment of nanoparticles to create \"smart fluids\" or nanofluids is by far the most developed. Thanks to the pioneering work carried out by [PERSON] and [PERSON], the disjoining mechanism of the oil drop was also analyzed. The same procedure has also been adopted to analyze the nanoemulsions, which in laboratory tests have demonstrated improved stability characteristics. The main problem reported in the nanoemulsions--which should still be subjected to further investigation--is their stability under the harsh conditions usually found in reservoirs (high pressure, high temperature, and the presence of dissolved salts). Finally, the use of active metal nanoparticles acting as nanocatalysts was introduced and studied, predominantly for the recovery and upgrading of heavy oil cuts. These present numerous complications for extraction, such as reduced flowability due to their high content of resins and asphaltenes. Nanocatalyst employment has shown great potential, acting as an \"underground refinery\" which improves and pretreats the oil, increasing its mobility and reducing the viscosity. However, as was presented in this review, some research must still be done in this area to tackle some issues, such as improving the dispersion of nanocatalysts in the rock formation. As is presented in the literature, it is deemed that EOR is not an exclusive field belonging to a single discipline. The use of nanotechnology in EOR as a tool to enhance traditional techniques has demonstrated a promising future, although there are still many unanswered questions. Nanotechnology cannot be addressed as an independent recovery process in EOR, but instead as a way to enhance the standard recovery techniques. This cannot be described as a new branch of applied sciences but, such as every process in EOR, a combination of different disciplines working together for the greater good. It is the intersection of the already well-known disciplines in EOR together with nanotechnology, which lends its unique features, allowing the development of a whole new branch of research in the oil industry.