Low molecular weight co-polymer for calcium scale inhibition at high temperature

Calcium scaling problem in production tubular is the most widespread among flow assurance problems. Well intervention in every 3-4 months are common to combat calcite deposition and rapid production decline. In order to minimize the formation of scale deposits, threshold scale inhibitor treatment with polycarboxylates or Phosphorous containing compounds (such as phosphonates or phosphate esters) are common practice in oil industry. In general the polycarboxylates rarely provide optimum performance against calcium carbonate. Higher molecular weight acrylate base products often precipitate as calcium salt. Phosphorous containing scale inhibitors has good overall treatment efficiency, however increasing pressure by environmental regulatory authorities has promulgated search of newer and greener threshold scale inhibitors. This paper describes synthesis, characterization and efficiency of a high temperature stable, threshold scale inhibitor which is found to work well in low doses at a wide range of pH and temperature. A low molecular weight, maleic acid base co-polymer is synthesized, characterized and inhibition efficiency was compared for calcium carbonate scaling. Molecular weight of the polymer was determined through GPC. FT-IR spectroscopy was used for functional group distribution pattern. Scale inhibition efficiency was measured through chemical screening test, dynamic tube block method and also through electrochemical technique such as constant potential electrolysis and electrochemical impedance techniques. XRD and SEM analysis demonstrated inhibited and un-inhibited crystal structure. The copolymers showed +90% efficiency in 15-20 ppm dosing at common wellbore temperature (upto 100°C). For even higher temperature (+120°C) dose requirement is more. Excellent inhibition property is demonstrated against calcium carbonate scale deposition. Electrochemical studies supported the static and dynamic test results. SEM images demonstrated the scale inhibition of the polymers through adsorption on the growing crystal phases of the nuclei, which resulted in distortion and retardation of crystal growth.