Untitled - Technische Universiteit Eindhoven

Chapter 1IntroductionThe subject of the thesis is reactive transport of an Oil-Soluble Chemical (OSC) intwo-phase systems. It was inspired by the need for new high-performance chemicalsto reduce water production in oil and gas production wells. The context or backgroundis discussed first, followed by a short description of the concept of OSCs for watercontrol. Related studies are briefly reviewed. Finally, the scope and outline of thethesis are discussed.1.1 Water control using gelsEach year many billions of barrels of water are produced world-wide, especially in thematuring oil fields. The produced water can stem from natural waterdrive or waterfloodthrough the mechanisms of coning, casing leaks or channeling [1]. The produced watercompromises the oil recovery and is expensive to dispose of. It was estimated that thecost-savings for the oil industry amount to about 100 million USD per year for each 1%reduction in produced water [1].Water control or water shut-off can be accomplished by several methods. The traditionalmethod is to squeeze a cement in the near-wellbore formation which hardens oncein place [2]. However, some problems are associated with cement squeeze [3]. First, theslurry is very viscous, so that a very low injection rate needs to be applied in order toremain under the critical fracturing pressure. Secondly, due to the brittle nature of cementsthe blocking capacity may be temporary. Furthermore, since the cement slurry isa dispersion of solids the risk exists that the permeability of the oil-producing zones isdamaged.In Enhanced Oil Recovery (EOR) [4] the water control procedure often involves theinjection of gel-forming chemicals (also referred to as gelants) into the near-wellbore formation.Ideally, the formed gel changes the permeability of the reservoir rock selectivelysuch that the oil flow is not hindered, whereas the water flow is reduced or blocked completely.The principle of this process in illustrated in Figure 1.1.Many gel systems have been tested and applied in the field. Often the results areunpublished, classified or reported in little detail. Nevertheless, 30–40% of the treatmentsproved to be successful over many years [3], whereas others were successful onlytemporarily or failed completely [5–7]. Depending on reservoir conditions and economicalrestrictions each problem faced requires a specific choice of gelant and treatment procedure.Most gel systems have been investigated in the laboratory on chemical behaviorand performance. The majority of the applied and tested gelants are aqueous based,1