English abstract
The utilization of Alkyl Aryl Ether Sulfonate surfactant, as an enhance oil recovery option from Yibal oilfield in Oman, has been investigated. This was accomplished through the experimental protocol based on the following criteria: i) compatible with reservoir brine, ii) ultralow interfacial tension (IFT) between oil and brine, iii) optimum solubilization at brine- crude oil interface, iv) least adsorption onto reservoir rock. AES-802, AES-805 and AES-808 were chosen in this study. All surfactants were compatible with brine reservoir, characterized by high salinity (TDS = 200g/L) and elevated temperature (T = 75°C), where no precipitation was observed at wide concentration (0.05% - 0.5%). AES-808 showed even better compatibility up to 1%. The interfacial tension behavior was strongly dependent on surfactant concentration and structure. Three different patterns are observed. In the low range of surfactant concentration (0.001-0.005 w/v%), the interfacial tension decreases rapidly with time from an initial value of 12 mNm to an equilibrium value after few hours. At 0.01% surfactant concentration, the IFT first decreases very rapidly to an ultralow transient value (ymin = 1.1 x 10-3 mNm", 4.5x10-2 mNm-' for AES-808 and AES-808 respectively), followed by a gradual increment to an equilibrium value of 9.1 x 102 mNm- for both surfactants. At higher surfactant concentrations (0.05-0.1%), the decrease of the IFT from the initial value of 12 mNm- could not be observed. The increment from transient value to the equilibrium value was observed. Gel is formed at brine- crude oil interface at low concentration (0.001-0.005%) whereas at higher concentrations up to 5% the phase behavior consists of oil in water microemulsions in equilibrium with excess oil, The investigated surfactant show strong affinity for adsorption at carbonate, reservoir formation, and they showed "S" type adsorption isotherm. The adsorption strongly dependent on surfactant structure; where the adsorption plateau for AES-802 stand at 14mg/g that was higher than the adsorption plateau for AES-805 and AES-808 valued 5mg/g. On the other hand, the adsorption isotherm was independent on both temperature and solid- liquid ratio. Future work will be carried out of nonionic surfactant to reduce surfactant adsorption. Alternatively, scarifying agent should be used or nonionic surfactant with cloud point higher than average temperature reservoir.
