Abstract:

The process of displacement and imbibition is alternative in the cyclic water injection.If the time of imbibition is short than needed time，the balance of imbibition can not be attained，which makes insufficient exchange of fluid.Based on that，the concept of balance time is introduced，the one dimension core simulation is used，the mechanism of imbibition of practical reservoir is analyzed and the influence of viscosity ratio of oil and water，capillary，water saturation to balance time of imbibition are studied.The results show it will make the balance time increase for the big viscosity ratio of oil and water，small capillary and high water saturation，which will make the balance of imbibition be unable to be attained and the effect of cyclic water injection not good.Especially in the period of high water cut，owing to the high water saturation and low capillary pressure，the process of imbibition needs more time to attain balance.When the time of stopping production is less than the balance time of imbibition，the cyclic water injection would not achieve the expected effect.It offers the effective assist to the establishment of rational work system through the research of mechanism of imbibition in cyclic water injection.

Key words: cyclic water injection, imbibition process, balance time, capillary pressure, numerical simulation