Technology Study On Removal/Inhibition Scale In Alkalescent Alkaline/Surfactant/Polymer Flooding Of Daqing Oilfield

"NaOH/Surfactant/Polymer" ASP flooding as a new improve recovery technology has significantly increased oil recovery and good economic, but in the process of ASP flooding, emulsification and scaling problems caused by NaOH have been restricting its mass industrial applications. In recent years, in order to reduce adverse effects of scale for the normal production of oilfield, Daqing Oilfield tries to use Na₂CO₃ to substitute NaOH, and carried out the pilot test has been in Sabei Oilfield. Alkalescent ASP Flooding solve the emulsified and scaling problems of production system, but the scaling problem which happen in the injection system and stratum near wellbore of alkalescent ASP system still have serious impact to the normal production. Therefore, the study on removal/inhibition scale in alkalescent ASP system has important theoretical significance and application value for perfect the alkalescent ASP flooding. On the basis of current research results, the author analysis the scale samples elements of injection system using the instrument testing and theoretical analysis method. This paper proposes the technical ideas of Cr³⁺ polymer gel improve the profile control in injection wells. Article carried out the experiment research on the polymer gel optimized formulation, nature evaluation and the compatibility with alkalescent ASP system, and discussed the removal scale mechanism of Cr³⁺ polymer gel. In addition, the pilot test has been carried out in the Beisanxi 2-1-P56 well of Daqing Oilfield. Research results show that different with the alkali ASP flooding which scaling occurs mainly in the production system and scale sample give priority to silicon/aluminum material, alkalescent ASP flooding scaling occurs mainly in injection system and scale sample give priority to calcium carbonate. In produced water conditions, Cr³⁺ ion can cross-linking reaction with polymer molecules, formation Cr³⁺ polymer gel. Cr³⁺polymer gel not only has the strong profile ability, but also has good compatibility with alkalescent ASP system. Field experiment results show that in the end of Cr³⁺ polymer gel injection, the injection pressure decreased obviously, profile control improved obviously, reached double functions on scavenge and blanking off high permeability zone, this provide effective approach for enhance the alkalescent ASP flooding oil recovery.