Inhibition of BaSO4 Scale Formation in Oilfield Equipment using Rutin from Sweet Orange (Citrus sinensis L) Mesocarp Extract (SOMEX)

The majority of commercial scale inhibitors used in the oilfield are synthetic, expensive, poisonous, non-biodegradable, ecologically harmful, and non-renewable. The search for a better, and more eco-friendly scale inhibitor alternative to the available ones has remain ongoing. Rutin obtained from sweet orange mesocarp extract (SOMEX) was modified using furfuraldehyde, and urea at varying molar ratios to form a novel green scale inhibitor, namely, Rutin (RU), Rutin-Furfural-modified polyphenolic resin (RFP) and Rutin-Furfuraldehyde-Urea- modified polyphenolic resin (RFUP). In order to create the scale inhibitors RFP and RFUP, the rutin extract, RU was first mixed with Furfuraldehyde in a 2:1 molar ratio and heated to 130oC with 2 ml of 1% w/v NaOH for 60 minutes to obtain RFP; then mixed with Furfuraldehyde and Urea in a 2:2:1 molar ratio, heated at 70oC with 2 ml of 1% w/v NaOH for 30 minutes to obtain RFUP. FTIR was used to characterise the inhibitors. Results of analyses show that RU, RFP and RFUP inhibitors are alkaline, thermally stable at a temperature of 130oC after 24 hours and compatible with the formation brine at a temperature of 25oC. The inhibitors' efficacy were assessed using BaSO4 brine and synthetic formation water that was generated according to the National Association of Corrosion Engineers (NACE) standard. From the results of the inhibitor dosage evaluation test, the lowest effective RU dose of 20 mg/L resulted in an inhibition rate of 70.40% on BaSO4 scales formation. As the inhibitor dose was raised above 20 mg/L, the rate of inhibition decreased. Longer contact times result in better inhibitor activity on the formation of BaSO4 scales at 71oC and 78oC respectively. Additionally, it was noted that the inhibition of RU, RFP, and RFUP on the formation of BaSO4 scale rose when the temperature was raised from 71oC to 90oC at a process time of 4 hrs. But when the process time was extended to 24 hrs the inhibition efficiency of the inhibitors initially increased with temperature increase up to a pick temperature of 78 oC, after which the inhibition efficiency starts to decrease slowly till it gets to the minimum. The findings of this study demonstrate that rutin derived from SOMEX and its derivatives has a good potential as green scale inhibitor for oilfield operations.