Alkali-based Displacement Processes in Microfluidic Experiments: Application to the Matzen Oil Field
Research output: Research › Master's Thesis
The Austrian Matzen oil field is producing under waterflooding since more than 50 years. By waterflooding, in average 35% of the oil can be recovered. This means that the majority of the oil stays behind after applying conventional production methods, i.e. after primary and secondary production stages. It is also safe to assume that a large portion of hydrocarbons in the Matzen field cannot be produced further using secondary oil recovery methods. Tertiary methods, also called enhanced oil recovery (EOR), comprise techniques that aim to increase the recovery by targeting unrecovered trapped oil at the end of conventional production. Chemical flooding is one of these EOR techniques, which include the injection of alkali, surfactants and a variety of their combination. Alkaline flooding is believed to be the cheapest chemical EOR method and OMV is showing a growing interest in employing it in the Matzen field. In this thesis, glass microfluidic devices (micromodels) are implemented to study pore-level alkaline-flooding mechanisms and their interactions with Matzen oil-field samples. Furthermore, microchips preparation and cleaning procedures have been developed and are proposed in the frame of the present thesis. The experiments have been performed using the two most common alkali types; aqueous solutions with different concentrations of sodium hydroxide and sodium carbonate were injected into microchips, saturated with high TAN oil samples, supplied by OMV from Matzen (8th TH and 16th TH reservoirs). Likewise, a sample from the Flysh reservoir, which has a low TAN has been used to investigate the importance of petroleum acid constituents. The injection experiments were performed in secondary and tertiary recovery modes. The Flysh oil sample showed the highest recovery in pure-waterflood experiments, likely because of a more favorable mobility ratio. In this case, no recovery enhancement was detected by injecting alkaline solutions. On the other hand, higher recoveries were recorded in alkaline flooding experiments using high TAN oil samples. The injection of sodium carbonate solution was much more efficient compared to sodium hydroxide. Furthermore, water in oil (W/O) and oil in water (O/W) emulsions were observed depending on the solution concentration and oil type. Large oil-water interfaces and oil threads were noticed as a sign of low interfacial tension. Finally, experiments indicated higher overall oil recovery in secondary injection scenarios in comparison to conventional waterflooding and subsequent tertiary alkaline floods.