Abstract
In the surfactant alternating gas injection, the injected surfactant slug is remained several days under reservoir temperature and salinity conditions. As reservoir temperature is always greater than surface temperature. Therefore, thermal stability of selected surfactants use in the oil industry is almost important for achieving their long-term efficiency. The study deals with the screening of individual and blended surfactants for the applications of enhanced oil recovery that control the gas mobility during the surfactant alternating gas injection. The objective is to check the surfactant compatibility in the presence of formation water under reservoir temperature of 90oC and 120oC. The effects of temperature and salinity on used surfactant solutions were investigated. Anionic surfactant Alpha Olefin Sulfonate (AOSC14-16) and Internal Olefin Sulfonate (IOSC15-18) were selected as primary surfactants. Thermal stability test of AOSC14-16 with different formation water salinity was tested at 90oC and 120oC. Experimental result shows that, no precipitation was observed by surfactant AOSC14-16 when tested with different salinity at 90oC and 120oC. Addition of amphoteric surfactant Lauramidopropylamide Oxide (LMDO) with AOSC14-16 improves the stability in the high percentage of salinity at same temperature, whereas, the surfactant blend of IOSC15-18 and Alcohol Aloxy Sulphate (AAS) was resulted unstable. The solubility and chemical stability at high temperature and high salinity condition is improved by the blend of AOSC14-16+LMDO surfactant solution. This blend of surfactant solution will help for generating stable foam for gas mobility control in the methods of chemical Enhanced Oil Recovery (EOR).
Highlights
After primary and secondary oil recovery methods, about one third of the Original Oil in Place (OOIP) are remained in the pore channels of existing reservoirs due to the decline in pressure
The surfactant solution was mixed with maximum brine salinity at high temperature. 10ml of each concentrated solution of surfactant was taken in a glass test tube, and allowed to settle for an hour in an oven at reservoir temperature of 90 and 120oC
The AOSC14-16 was stable in the maximum divalent ions for the composition of (Brine-C) as compared to the composition of (Brine-A and Brine-B)
Summary
After primary and secondary oil recovery methods, about one third of the Original Oil in Place (OOIP) are remained in the pore channels of existing reservoirs due to the decline in pressure. Thermal Stability and Compatibility of Surfactants in Presence of Formation Water Salinity under Reservoir Conditions injection process suffers by gravity override and fingering problems in the heterogeneous oil produced reservoirs. Anionic surfactant Alpha Olefin Sulfonate is generally preferred due to its wetting characteristics (because of modification in the water-wet system) and good foaming properties in crude oil. This type of surfactant provides extra ordinary detergency and biodegradability [4]. To overcome the problems of solubility and chemical stability anionic surfactants are used mostly at high temperature
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