Laboratory Study On Emulsifying-surfactant Flooding In High Temperature And High Salinity Reservoir

For high temperature and high salt reservoir,the oil displacement effeciency of common surfactant is poor.Taking Sha second 2+3 block in west of Pucheng oilfield for an example, surfactants that are suitable for this block were selected, the effect of emulsification on improve oil recovery are studied, the emulsifying capacity under static and porous medium cases are evaluated,the emulsifying-surfactant was selected,laboratory surfactant flooding experiments are also conducted in this paper.The experimental results show: the interfacial tension of SHY-1, YD-G1 and crude oil can reach the order of 10-3mN/m with the concentration range of 0.05%~0.9%,the interfacial tension of NPES-458 and crude oil can reach the order of 10-3mN/m with the concentration range of 0.3%~0.5%. The interfacial tension between these surfactants solution and crude oil can reach the ultra-low level of 10-3 mN/m before and after them were put into a constant temperature oven of 120℃30 days, which shows them have good heat and salinity tolerance capability. These surfactants has relatively strong ability to alter water wettability to oil wettability for quartz,while they has no obvious change for water wet quartz, the absorption amount of them in reservoir are relatively large, the performances of oil washing efficiency of YD-G1 are strongest among them.The the emulsifying capacity evaluation experiments of these surfactants under the emulsifying capacity under static and porous medium cases show that,YD-G1 has the best emulsifying capacity among them. The capacity of reduce interfacial tension, the emulsifying power, the stability of emulsification combinated with the index of composite emulsifying ability evaluation, YD-G1 was called as the emulsifying-surfactant. Researchs show that the emulsifying ability of surfactant is a key factor for improve oil recovery, the stronger emulsifying capacity the surfactant has, the better the oil displacement efficiency is. The emulsifying-surfactant flooding can combine the profile modification of emulsion with the oil displacement of surfactant flooding,it can use emulsion for mobility control, which can improve the oil displacement effect effectively.The optimum injection mass percentage, volume and rate were determined to be 0.6%, 0.5PV and 0.5m L/min by optimization of laboratory experiments. In this condition, surfactant flooding can improve a recovery ratio of 13.8%. The best slug combination mode are 1%(0.17PV) +0.3%(0.33PV) under the condition of homogeneity, which can improve oil recovery 20.7%. The oil displacement efficiency of YD-G1 degraded with the increase of the permeability contrast under the condition of heterogeneity.