Study Of The Effects Of The New-born Materials From Alkali-surfactant-polymer Flooding Liquids On The Separation Characteristics Of The Produced Liquids

Polymer flooding and ASP (alkaline, surfactant, polymer) flooding have been widelytested in Daqing Oilfield. While significant decrease of water-cut of produced liquid andincrease of oil production have been achieved, the stability of produced liquid wasenhanced and the difficulty of oil-water separation was significantly increased. The earlyresearch was mainly focused on the influence of ASP components on the emulsification,stabilization and destabilization of ASP flooding produced liquid. However, few studieshave been done on the effect of the new-born minerals, which was produced by theinteraction between the injection liquids and reservoir core in the separation performanceof produced fluid.In this work, the interaction between reservoir core and the injection liquids ofalkali-surfactant-polymer(ASP) flood was systematically studied. The interaction wassimulated using dynamic immersion method under constant temperature45℃.In order to investigate the variation of ASP Components during the interactingprocess, viscosity, concentration of OH-and surfactant of the supernatant from the mixtureunder different immersion conditions was analyzed. Kinetic model of alkali consumptionwas established. To determined the change of reservoir core, the composition anddissolution characteristics of the core after immersion were analyzed using scanningelectron microscope, energy spectrum, and x-ray diffraction analysis. For confirming thedissolution of ions from the reservoir core, inductively coupled plasma mass spectrometrywas used to analyze the supernatant. Then, the simulated produced water was prepared bythe supernatant and water contained Ca, Mg ion etc. after7days aging process, the solidparticles existed in simulated produced water were separated and characterized forrevealing the new-born minerals produced by the interaction between the injection liquidsand reservoir core. Finally, the influence of the new-born minerals on the separation characteristics of simulated produced fluids was studied.The main conclusions of this paper were as follows.(1) ASP components eroded the natural core and its main composition, such as quartz,feldspar, illite and kaolinite, at different degree. There were no visible new-born mineralson the core. The main water-soluble content was Si4+and Al3+.(2) The injection liquids of ASP flood mixed with formation water after the reactionwith reservoir core. This resulted in the formation of supersaturated aqueous. New-bornminerals such as calcite and amorphous silica particles etc. were formed. In the process,the presence of alkaline earth metal ions alone has little influence on the formation amountof the new-born minerals. The combination of CO32-and alkaline earth metal ions led tothe increase of new-born minerals in produced liquid.(3) Calcite and amorphous silica particles, which was formed during the interactionamong reservoir core, the injection liquids of ASP flood and formation water, adsorbed onthe oil-water interface, produced steric hindrance. which hindered the oil dropletcoalescence with each other and increased the difficulty of oil-water separation.