Chemical enhanced oil recovery and the role of chemical product design

The current and prospective worldwide energy demands have led either to start exploiting the more difficult and costly unconventional oil reserves, or to maximize the exploitation of conventional oil sources. This triggered the development of enhanced oil recovery processes in order to improve the efficiency and lifetime of mature oilfields. Chemical Enhanced Oil Recovery is one of the most interesting group of methods nowadays. The use of chemical products such as polymers, surfactants, alkalis and polymeric surfactants has been continuously increasing during the last decades. However, these chemicals should be designed to withstand the harsh conditions present in the reservoir (e.g., dissolved salts, pH, temperature, presence of bacteria) and increase the efficiency of the process. One of the key factors in this development is the (macro)molecules' architecture and its influence on the physical properties of the fluids being injected: from linear to branched polymers, from monomeric to gemini surfactants. Furthermore, the combination of these chemicals has showed a great potential due to the synergy between them, creating a new spectrum of techniques in chemical Enhanced Oil Recovery. This review presents the work done in this field with an analysis of the products and technologies employed, including their limitations and possible ways to improve their performance. All in all, the need of advanced products for oil recovery and new, or improved, energy sources has set off a new field of research wherein chemical product engineering plays a major role.