Study About Stability Of Water-Based Foam Under Harsh Conditions

Theoretical research and technology development about foam have attracted a lot attention for their important potential application, because aqueous foam has got successful utilization, not only in traditional regions, such as mineral floatation, detergent, and enhanced oil recovery, but also in many other advance fields recently, such as photoelectric barrier, infrared extinction or electromagnetic interference shielding, blast mitigation, and being used as soft bionic template for controllable synthesis of functional nanoparticles, etc. With the generation and quick development of the new technologies of foam, it has been imminent and urgent to develop the preferable foam systems meeting the requirement of more and more harsh conditions in the practical applications. For example, foam flooding can be applied to the reservoir with harsh conditions in enhance oil recovery, which provides promising prospects for the effective development of the high temperature and salinity reservoirs, heavy oil reservoirs and low permeability reservoirs, where crude oil is hard to be displaced. Besides, the using of carbon dioxide (CO2)and complex gases gotten from the flue gas as the foaming gas has been paid much attention, as it is very valuable because of its energy conservation and emissions reduction. However, the poor foam stability under harsh conditions, such as high temperature, high salinity, the existence of crude oil and using CO2as the foaming gas, has always been a problem.In this paper, foam stability under harsh conditions (high salinity, high temperature, the existence of oil and CO2being the foaming gas) was discussed and the mechanisms were studied to guide the development of application system and improve the process.This paper is divided into four parts:In the first part, the stability of foam stabilized by single surfactant at high salinity and high temperature was investigated. And the ultra stable aqueous foam stabilized by a kind of flexible connecting bipolar-headed surfactant alkyl polyoxyethylene sulfate (AE3S) with Mg2+coexisting was reported. Detailed molecular behavior of AE3S in foam film with divalent cationic Ca2+or Mg2+coexisting was investigated by molecular dynamic simulation, foam lamella stability evaluation and Infrared spectroscopy, comparing with traditional surfactant sodium dodecyl sulfate SDS, for the purpose of finding out how the micro character and array behavior of molecules in the foam film determined by molecular interaction effect the formation of Newton black film (NBF), and revealing the key mechanism maintaining ultra high foam film stability.The second part focuses on the mixed surfactants under various temperature and salinity. Optimized foam formulations for different application conditions were gotten. Mechanism of the enhanced foam stability by the synergism of AES and DSB was studied by molecular dynamics simulation, and the microscopic law to optimize foam stability by the surfactant synergism was proposed.In the third part, defoaming and antifoaming behaviors of the crude oil and several other kinds of oil were investigated. Microfiuidic device was designed to study the interaction between foam bubbles and emulsified oil droplets. Defoam and antifoam mechanisms were investigated by combining results of experimental and molecular dynamics simulation methods. And the feasibility of the application of low tension foam flooding on the oil displacement was discussed.Finally, the influences of foaming gas (nitrogen, composite gas and carbon dioxide) on the foamability and foam stability have been studied. The reasons for the instability of CO2foam were studied, and relatively stable CO2foam stabilized by SDS was found. Effluences of salinity, pH and surfactant concentration on CO? foam stability were studied. And the application probability of flue gas on the oil displacement was discussed.