Imbibition Oil Recovery System For Changqing Low Permeability Reservoir

How to develop the low permeability reservoir efficiently is the key problem to be solved in oil industry.Imbibition technology is a more economical method to improve oil recovery.Based on the experimental results,the different effects on imbibition oil recovery process in low permeability oil reservoirs were studied comprehensively,and the screening indexes and the evaluation criterion of the imbibing system were also investigated.The researching results are given as following:(1)The effect of the key factors effect on oil recovery of the imbibition agent system and the critical conditions for improving imbibition effects were investigated in laboratory through oil sands static imbibition experiments,considering the oil-water interfacial tension,contact angle,emulsion properties,viscosity,p H.(2)In Changqing low permeability oil reservoirs,the type of imbibing agent is anionic surfactant.In imbibition compounded oil flooding process,anionic surfactant should be the main chemical agent,which interfacial tension less than 1.0×10^-1m N/m has good imbibition effects.The low interfacial tension is a necessary but not sufficing condition for selection the imbibing agents,and the interfacial tension do not required to reach the super low when imbibition oil recovery process occurred.The imbibing agent system should have good wettability alteration.The wettability alteration improvement condition for Changqing low permeability oil reservoirs is the wettability of rock changes into hydrophilic,and the contact angle between water and rock surface should be less than 60 degrees.The oil sand static imbibition oil recovery rate of the system increase with the emulsion index increases.When the emulsion composite index is 0,imbibition cannot happen.In Changqing oilfield,when the emulsion composite index is 50?65,the imbibition oil recovery effect is the best.The results also indicate the oil-water interfacial tension and the water-rock contact angle have a negative correlation with the oil sand static imbibition recovery ratio,the p H,viscosity(without polymer)of the imbibing agent system and the emulsion composite index have a positively correlation.(3)Application SPSS statistical software,through multi-factor variance analysis,the data dependence analysis was carried out,the results indicate the effect sequence on static imbibition recovery is given as following:oil-water interfacial tension and emulsification performance index,contact angle,viscosity,and p H value of the system.Through the multiple linear regression analysis,the weights of each performance index of the imbibing agent system on the oil sand static imbibition oil recovery were obtained,and the results were consistent with the variance analysis.(4)Through the static and dynamic imbibition experiments,the results show clearly that the oil-water interfacial tension,emulsification and the wettability alteration of reservoir rocks are the important mechanisms in the process of oil displacement.The dynamic imbibition results are the embodiment of the effect of water flooding and imbibition process.Therefore,when selection the imbibition system process,the performance requirement difference between the two kinds of process should be considered,and make a reasonable choice.