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Precipitation of carbonate and sulfate salts of alkaline earth metals on equipment surfaces is a major challenge in oilfeld applications. The deposition of these salts results in formation damage, equipment wear, and fow line blockage. Polymeric additives are used in the formulations to control deposition of unwanted salts. This article presents comparative data on the performance of biopolymers and synthetic polymers as strontium sulfate precipitation inhibitors.
Scales commonly encountered in many industrial processes-desalination plants, geothermal wells, steam generators, wastewater treatment plants, petroleum drilling, phosphoric acid production, etc.-include sparingly soluble carbonates and sulfates of calcium, barium, and strontium. Although they are not as common as calcium carbonate (CaCO3) and calcium sulfate (CaSO4) scales, barium sulfate (BaSO4) and strontium sulfate (SrSO4) deposits have long plagued oilfield and gas production operations. The deposition of BaSO4 and SrSO4 scales on tubes and vessels can result in plant shutdown, production losses, equipment replacement, and cleaning costs.1 In addition, scaling is often accompanied by corrosion damage. Therefore, scale and corrosion are two of the greatest challenges facing plant designers, operators, and water technologists. The influence of low dosages (just a few ppm) of inhibitors to prevent or retard the formation of Ca, Ba, and Sr sulfate salts has attracted the attention of academic and industrial researchers. Common inhibitors tested include homopolymers of aspartic acid, acrylic acid, maleic acid, itaconic acid, and methacrylic acid; copolymers containing maleic acid or acrylic acid; and other monomers containing different functional groups. Dogan, et al.,2 using the spontaneous precipitation technique, investigated the influence of poly(ethylene oxide) and poly(methacrylic acid) (PMAA) polymers as CaSO4 growth inhibitors. Results of their study reveal that inhibition increases with acid content of the polymer. Amjad3 showed that polymeric additives containing the carboxyl (-COOH) group, such as poly(acrylic acid) (PAA), poly(maleic acid), and poly(itaconic acid), were particularly effective as CaSO4 dihydrate (CaSO4·2H2O) growth inhibitors.
The inhibitory effect of environmentfriendly biopolymers such as carboxymethyl inulin (CMI) has been the subject of numerous investigations. CMI is a chemical derivative produced by the carboxylation of inulin, a polysaccharide-based polymer present in the roots of the chicory plant. The performance of CMI as an inhibitor for CaCO3, BaSO4, and calcium oxalate has been reported.4-6 Results of these studies show that CMI is an effective inhibitor...