Upstream Scale Inhibition in Carbonate Reservoir – Evaluation of a Green Chemistry

Oil well scale inhibition with green scale inhibitor is a relatively unexplored area. Huge amount of produced water containing various types and amounts of residual scale and corrosion inhibitors is discharged into the environment everyday, which has brought focus of environmental regulatory bodies and encouraged operators to look for greener chemicals. Tannic acid, a type of hydrolysable tannin that widely exists in nature and has an excellent environmental profile, such as having high biodegradation potential and nontoxic. Although it's acidic it prevents corrosion through passivation of steel surface through chelation mechanism. This specific property has encouraged us to further investigate its scale inhibition efficiency at wellbore condition.

Static and dynamic studies show that tannic acid could be a potential scale inhibitor for produced water with high scaling tendency, tested upto 110°C for a offshore reservoir fluid chemistry. Characterization of inhibited scale crystals through various methods (FT-IR, XRD & SEM) revealed structural deformation of crystals which explained scale prevention mechanism. HT-HP core flow studies along with quantitative measurement through UV spectroscopy revealed poor adsorption and fast release of tannic acid in carbonate formation. The study suggested that tannic acid is an excellent and cheap green chemical, for continuous injection into the wellbore below bubble point region for controlling carbonate scale. Due to its poor adsorption and retention characteristics it can not be suggested for use as squeeze inhibitor in its original form.