The Study On Effect Of Gathering Pipeline Scaling By HPAM In ASP Flooding

With the wide application of Asp （alkaline–surfactant–polymer） flooding, the scalingbecomes more and more serious, which is harmful to the oilfield and environment. The papermainly studied the influence of HPAM （Hydrolyzed polyacrylamide）, as the polymer from aspflooding oilfield, on common scale such as calcium carbonate and the silica scale. Theconcentration and molecular weight of HPAM （Hydrolyzed Polyacrylamide） solutions,temperature, and pH were discussed in order to investigate the effects of HPAM on the scale.At the same time we also investigated the effects of the Asp component on the quantity ofscale. In order understand the effects on crystallization of CaCO₃by HPAM in Asp floodingwaste water, the crystallization of CaCO₃in HPAM solution was studied using NaHCO₃andCaCl2as reactive reagent. The composition and morphology of CaCO₃were assayed. Themicroscopic test methods such as X-ray diffraction （XRD）, Fourier transform infraredspectroscopy （FTIR）, Scanning electron microscope （SEM） were adopted to analyze themorphologies of CaCO₃.The microanalysis results showed that the crystallization of CaCO₃was stronglyinfluenced by HPAM. With adding HPAM, metastable vaterite, which is not easy forming inpure water, was obtained. Meanwhile, the morphologies of CaCO₃transformed from calcite tovaterite and aragonite. The paper analyzed the internal cause, and the results suggested: Thereasons leading to the change of morphology are carboxyl groups in polyacrylamide moleculeand Ca²⁺in solution form chelates by coordination bond. And the chelates are adsorbed on thesurfaces of the CaCO₃on solid-liquid interfaces so as to change the formation rate of calciumcarbonate crystal nucleus.Result of factors analysis indicated that HPAM with different molecular weightinfluenced the formation of CaCO₃. Compared with the blank sample, HPAM with differentmolecular weight all improved the concentration of the residual calcium ion. Theconcentration of the residual calcium ion with the HPAM added growthed with theconcentration of HPAM at first, then decreased and achieved at the maximum in300ppm.HPAM had the largest impact on CaCO₃formation when the reaction time is10h; the impactof the HPAM on CaCO₃formation increased with pH declined; at low temperature the HPAMhad the greatest impact on CaCO₃formation. HPAM with different molecular weight affectedsilica scale formation. Compared with the blank sample, HPAM with different molecularweight all enhanced the concentration of the residual silica ion. The concentration of theresidual silica ion in solution decreased with the concentration of HPAM at first, and thenincreased until it tends to be constant. With adding HPAM, the concentration of the residualsilica ion in solution decreased at first and then increased with reaction time extension;however it decreased at first and then increased with the pH rise and reach up to the minimumwhen the pH is8; it also decreased at first and then increased with the temperature rise. Theresearch provides a reliable basis for the mechanism research of the scaling problem in the oil extraction process of Asp flooding and the adoption of scale inhibition and scale inhibitor.