Strong Base ASP Flooding Block Cause Analysis And Solution Technology Of Plugging Study

Alkaline/ surfactant/ polymer(ASP) flooding in daqing oilfield has obtained good results of stabilizing oil precipitation, which has entered the stage of popularization and application of industrialization. But in the practice of the ASP flooding, Because the uncertainty of reservoir parameter, The complexity of mineral composition and the dissolution between reservoir minera and alkali, Part of the well of ASP have difficulties in injecting, which bring serious influence to the production of oilfield. Based on reservoir engineering, physical chemistry and polymer material science as the theoretical guidance, chemical analysis, instrument detection and physical simulation as technical means, xingshugang reservoir geology and fluid as the research object, evaluation of the adaptability between ASP system and reservoir,the dissolution of the reservoir rock and its influence on seepage characteristics have been studied, On the basis of which we did research on injection well blockage composition analysis, bockage effects on reservoir fluid absorption ability and plug solutions. The results show that ASP system reservoir adaptability is affected by rock permeability, heterogeneity, the relative molecular mass of polymer, the concentration of polymer and Shear strength. The most suitable parameters: polymer relative molecular mass 1200×104 and polymer concentration 2000mg/L or polymer relative molecular mass 1900×104 and polymer concentration 1500mg/L. With the increase of alkali concentration, reaction time, the proportion of liquid and solid, the dissolution between core and alkali increase. Compared with pure alkali liquor, The alkali/surfactant dual system and the alkali/surfactant/polymer ternary system dissolution of rock is weaker, which shows that the surfactant and polymer can reduce alkali dissolution of rock. In the process of alkali and sample dissolution, Ca2+ and Mg2+concentration decreased, which shows that carbonate precipitation formation cause pore flow cross-section decrease, seepage resistance increase.Poor compatibility between polymer relative molecular mass and reservoir pore throat and scaling phenomenon caused by alkali and mineral formation reaction are both the reason of injection difficulty, broken down technology is difficult. Blockage in injection well is another cause of the injection difficulties, due to a blockage mainly stranded in near wellbore area, using a small amount of plugging agent can remove plugging. Plugging agent solution formula:the oxidant(0.4%ClO2)+ the composite acid(12%HCl+3%HF+1%CH3COOH+0.6% the cationic quaternary ammonium salt +0.5%KCl+0.5%YC-SY). The recommended injection sequence:the oxidant→the composite acid.