| Halahatang oilfield existed water cut in single well and water channeling in unit wells after injecting water,and the oilfield has the characteristics of high temperature to 160 ? and high salinity to 2.33×105 mg/L.It was the reason why the efficiency of water injection for oil reduced year by year.After studying on the properties of formation water,crude oil and reservoir rock,a kind of heat-tolerance and salt-resistance surfactant SDY-2 was developed.The heat tolerance,salt resistance,ability of changing wettability and efficiency of washing oil aimed to SDY-2 were evaluated.Lastly,the process scheme of injecting surfactant for displacing oil was designed,and 2 single wells and a connecting wells were tested for evaluating the application effect of SDY-2 in the field.The results showed that as follows: Halahatang oilfield was belonged to special high temperature with 160 ? and high salinity with 2.33×105 mg/L.Carbon number of normal alkanes were in the scope of C5C35,which was normal distribution.The main component of reservoir rock was calcite,with the content more than 95%.The charge of reservoir rock were positive,and contact angles of oil-formation water-rock were larger than 105°,which indicated Halahatang reservoir belong to oil-wet reservoirs.The heat-tolerance and salt-resistant of surfactant SDY-2 was developed based on the characteristics of reservoirs.The heat-tolerance of SDY-2 was up to 160 ? and the salt-resistance of that was 2.33×105 mg/L.And SDY-2 could reduce oil-water interfacial tension from 26.505 mN/m to 0.486 mN/m and improve the recovery by 18.5%,static efficiency of washing oil was more than 80%.Adsorption loss of SDY-2 was only 0.651 mg/g which was lower than the standard of 1 mg/g.In addtion,the oil-water interfacial tension and efficiency of washing oil basically remained unchanged,after aging 30 d in 160 ? high temperature,which indicated the ability of heat resistance for a long time was prominent.Efficiency of water injection for oil of HA13-X and XK4-X increased from 0.519 to 0.612 and from 0.106 to 0.151,and moisture contents of oil reduced from 48.5% to 40.7% and from 60.1% to 53.8%.For connecting oil wells,using profile control agent to block big channels and forcing activated water to flow through small cracks are suggested,which can improve the displacement efficiency. |
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