Innovative Solution to Dissolve Highly Challenging Iron Sulfide Scales

Abstract Iron sulfide scales are an inorganic deposition, highly acid soluble, that block oil and gas wells, and are usually formed from H2S and reservoir/well reactive iron reactions, since HCl reaction with iron sulfide generates toxic and corrosive H2S gas, several alternative dissolvers including simple organic acids and more complex chelates have been utilized, our main objective is to evaluate the efficiency of a new synergetic of alternative dissolvers to provide economically satisfying treatments in Iron Sulfide scale defected wells. To judge the dissolution capabilities of the new solutions, four different synergies have been evaluated for HPHT solubility considering the effect of pressure and temperature, screening soaking time and solution pH influences, with aid of catalytic additives at different scale to dissolver ratios to be able to conclude the optimum treatment design. Furthermore, corrosion testing for proposed treatment, and reaction product Fourier Transmission Infrared Spectroscopy (FTIR) were performed, to find out the treatment corrosivity and the functional group of reaction products. An oil contaminated Iron Sulfide scale sample was tested, using different dissolver concentrations, with and without surfactant/solvent pre-soak, the best performed solution could achieve a minimum of 55% weight dissolution at 1:10 scale to dissolver ratio, a minimum of 61% weight dissolution at 1:20 scale to dissolver ratio, a minimum of 85% weight dissolution at 1:30 scale to dissolver ratio, by applying 6 hrs surfactant/solvent pre-soak and 24 hrs of static treatment soak, at 90 °C and 300 psig, the best performed solution was tested for corrosion and found corrosive at 250 deg F for 48 hrs on C95 corrosion coupon so that a compatible corrosion inhibitor was added to the treatment, the reaction products were reported water soluble. Based on the experimental data and recommended treatment design, fluid was pumped successfully and satisfying outcomes have been reported. This paper presents novel and additive information to the existing body of literature on Iron Sulfide scale dissolution, the developed product is a blend of organic salts in cationic surfactant solution, that provides an outperforming alternate economic solution to currently used Iron Sulfide scale dissolvers with high affinity to other mixed scales, and at less concertation and soak.