Characterization of fluid properties is key in the petroleum engineering practice, especially in mutually soluble Solvent-based Enhanced Oil Recovery (SEOR). However, current techniques for fluid composition measurements inside enclosed spaces during SEOR are inconvenient and can cause leakage problems. Radio Frequency Identification (RFID) could offer a solution here. RFID is a wireless data-collection technology, which enables real-time, continuous information exchange. This book examines the feasibility study of using RFID technology for laboratory measurement of compositions of diethyl ether-brine-oil mixtures in solvent-enhanced imbibition experiments. Based on this study it can be concluded that it is possible to use RFID technology to measure fluid compositions with an accuracy of a few percent (0.02). Accurate fluid characterization using RFID could facilitate minimization of the amount of injected mutually soluble solvent used during SEOR, thus reducing its costs and environmental impact. As such, RFID technology could be a valuable measurement tool in the oil and gas industry.