Foam Apparent Properties Study And Its Application In Heavy Oil Recovery

There were two sections in this paper. One was about the evaluation of foam apparent properties and their influencing factors. The other was about the foam stability mechanism study under high temperature and the stratum authigenic foam used in heavy oil recovery.Foam was an especial colloidal disperse system engendered by the dispersing of indiscerptible or tinily dissolved gas into liquid solution, which was used widely in petrochemistry, cosmetics, detergent chemistry, mineral floatation, food and so on because of its special properties.A series of foam properties evaluation methods were developed in this paper based on the former work, and systematic research work about foam generation way, foamability, foam stability, the ability to take and keep liquid, foam viscosity and foam size distribution had been done. And the effect of factors surfactant structure, surfactant concentration, surfactant synergism and polymer on the foam apparent properties were also studied, in order to find the relationship among foam apparent properties, micro mechanism and foam application.The formation of bubble was an energy increasing process, the energy needed to form a bubble increased with surface tension, so the lower surface tension it has, the better foamability it was. It was found in the paper that the foamability didn't have a linear relationship with the surface tension because of the introduction of gas and energy affected by bulk solution and foam, and it suggested that foamability should be evaluated at the situations that the foam was generated with the same energy.Foam stability was crucial for foam study and its application. The foam stability at temperature below 100℃ and above 100℃ was investigated by foam colume decay method and foam block in sand-pack pipe method.It was unsuitable to reflect the foam stability by half-life bucause of the sub-stable foam which was very sensitive to disturbance and useless for application. In the paper the foam stability was evaluated by half-life and foam decay curve together.Foam drainage was also very important for foam stability. Fast drainage resulted in fast foam break-up under no disturbance. In the paper electric conductivity method was used to measure foam drainge process, which was simple and accurate, and was very sensitive to the interfacial changes. The experimental results showed that, the ability for foam to take and keep liquid increased with surfactant concentration, and the foam drainage process was staved by adding polymer, but the polymer could not strengthen foam stability only if the surfactant could form stable interfacial films.Most reports on foam stability were under low temperature(<100℃), and the foam stability mechanism under high temperature was still unclear, while which is important for foam used at ultra-high temperature. Foam stability of surfactants with different hydrophobic chain length, was investigated by gas flow method and foam-block in sand-pack pipe method at different temperature. The experimental results showed that the foam stability increased with the chain length. Dynamic surface tension, interfacial rheometer and molecular simulation were used to study the stable mechanism of foam under high temperature in the paper, and a new foam stable mechanism was found out.The foam decay was dominated by foam drainage and gas dispersion through the foam film, and the foam decay was controlled by foam drainge when the temperature was low, because the foam drainage and gas dispersion rate was slowly. When temperature increased, the evaporation and gas dispersion increased and the foam stability was dominated by the film structure and strength. When the carbon number of the hydrophobic chain of surfactant was larger than 20, the hydration of the head group of surfactant could not support the chain to keep vertical and unattached, and the hydrophobic chain cross-link with each other, which result the viscoelastic modulus of the film increase sharply, then the foam film was strengthened, and the gas dispersion was decreased, so that the foam could be stable under high temperature.Besides, a new type of stratum authigenic foam mixture which could be used in heavy oil recovery was studied in the paper. A typical reaction which could released N² and CO₂ was chosen, and its reactive conditions including reactant concentration, reactive temperature and deflation rate were studied. The authigenic foam mixture still included a surfactant which could make the foam stable under high temperature, and had high oil/water interface activity. The oil recovery experiment results showed that, the reaction started and released gas after the authigenic foam mixture was injected into the sand-pack pipe with steam, and foam was generated in the sand-pack pipe and improve both vertical and horizontal sweep efficiency of the hot steam by plugging high permeability zones and the oil recovery was improved. The innovations in the thesis are as follows:1. A series of foam properties evaluation method were developed in this paper, systematic research work about foam generation way, foamability, foam stability, the ability to take and keep liquid, foam viscosity and foam size distribution had been done. And the effect of factors surfactant structure, surfactant concentration, surfactant synergism and polymer on the foam apparent properties were also studied.2. Foam stability of surfactants with different hydrophobic chain length at different temperature was investigated by foam decay method and foam-block in sand-pack pipe method. Dynamic surface tension, interfacial rheometer and molecular simulation were used to study the stable mechanism, and a new foam stable mechanism under high temperature was put forward.3. A new type of stratum authigenic foam mixture which could be used in heavy oil recovery was studied. The oil recovery room experiment results showed that, the reaction started in the sand-pack and gas was released after the authigenic foam mixture was injected into the sand-pack pipe with steam, by which foam was generated, both vertical and horizontal sweep efficiency of the steam were improved because high permeability zones were pluged by foam, and then the oil recovery was enhanced.