Corrosion Effects Of Alkali/Surfactant/Polymer Compound System On Second-class Reservoir In Lamadian

During production in Daqing Oilfield, alkali/surfactant/polymer flooding is a technologywhich can largely enhance oil recovery and at low cost, the application of alkali causes aseries of physical and chemical changes, and the products has some negative effect onreservoir, even causing stuck pump in production well and liquid production decrease. Basicon the existing researches, according to theory of reservoir engineering, petromineralogy andphysical chemistry, a series studies were carried out about influence that strong alkali andweak base on reservoir structure, reservoir structure after alkali flooding and dissolution toreservoir minerals and flow characteristics in core of displacement agent containing alkali.Results show that, strong alkali greatly affect pore structure of reservoir, and the effect ofweak base is not obvious. The dissolution of alkali is mainly to clay mineral and to feldsparand quartz is weaker, so the well wall would not fall down after alkali flooding. Theimmersion experiments showed that, as alkali concentration rises, the ratio of liquid to solidincreases and soaking time goes on, the corrosion is strengthened, and the major elements(silicon and aluminum) in core sample get into liquid to a certain extent. Compared to lye,alkali/surfactant system and alkali/surfactant/polymer system is of low corrosion capacity tocore under the same alkali concentration, showed that surfactant and polymer can reduce thecorrosion of alkali on rock minerals. After60days go on, molecules of silicic acid in liquidphase polymerize with each other and dehydrate into silica scale with the help of alkali. Theresult of the flow experiments showed that as alkali concentration rises, resistance factor andresidual resistance factor of solution increase and permeability of core decrease. The result isconsistent with immersion experiments, aluminum and silicon ion concentration in producedliquid of AS flooding and ASP flooding is lower than lye flooding, and the corrosion isweaker. In conclusion, lye corrodes rock seriously, followed by alkali/surfactant system andalkali/surfactant/polymer system. Compared to polymer, corrosion inhibition of surfactant isweaker and it does not much affect alkali corrosion to rock.