INVESTIGATION ON POLYPHENOLIC COMPOUNDS DERIVED FROM TROPICAL HERBS FOR INHIBITING SILICATE SCALES

Silicate scale deposition in region around the wellbore or in any parts of the production system is a serious production problem. During hydrofluoric acidizing treatments, the release of silicon and aluminum sets off a series of reactions that include hydrolysis of silicic acid, condensation and eventual polymerization of amorphous silica. These reactions negate the original aim of inhibiting silicate scales. Currently, most chemical inhibitors are harmful and not environmental friendly. Therefore, environmental friendly scale inhibitors extracted from plants are beginning to get attention as possible alternative. This paper presents experimental findings on tropical herbs such as premna cordifolia, camellia sinensis, and piper betle and abelmoschus esculentus for preventing silicate scales. Effects of polyphenolic compounds were examined in mitigating the polymerization and condensation of the silicic acid. The performance of selected herbs was evaluated at different concentrations and a range of pH before comparing them against the conventional green inhibitor, polyaspartate (PASP). Experimentally, 100 ml samples of brines representing formation water were added with 100 ppm, 500 ppm and 1000 ppm polyphenolic compounds from the four herbs respectively. Observation was made for 24 hours at 90oC during the compatibility test and at interval of 1,2,3,4,5 and finally 24 hours for turbidity test at pH 1-5. The loss of transparency due to the presence of suspended particulate, colloidal material, or both represents the degree of turbidity. Results showed that green inhibitors at concentrations of 100 ppm, 500 ppm and 1000 ppm did not cause precipitation. Turbidity of all samples decreased when concentration of polyphenolic compounds increased. Camellia sinensis, due to its high content of polyphenolic compounds caused the least turbidite compared to the other green inhibitors. This finding justifies other published works where polyphenolic compounds had acted as a chelating agent in the form of silicon-polymerizing complexes to condense and polymerize silicic acid in brines to prevent formation of silicate scaling. Nevertheless, turbidity of all brines added with green inhibitors showed higher turbidity values than that of brines added with PASP. It might be attributed to the high concentration of chlorophyll since the extracts were used in their pure forms without other treatments.