A Development and Field Deployment of Novel Iron Sulfide Prevention Package

Abstract Iron sulfide scale is considered as a problematic scale in oil field. Due to its fast precipitation kinetics and complicated physical-chemical properties, the control of iron sulfide is challenging. The conventional chemical treatments for iron sulfide usually come with side effects. Prevention of the sulfide scale formation using this technology was proven a feasible and less hazardous approach. In this study, a high-performance iron sulfide control formulation is developed with successful field trial. An anoxic bottle test was developed for evaluating the performance of raw materials and candidate formulations. The bottle tests were conducted at 80F for 4 hours to mimic the condition and retention time in the field. The brine matrix contains 3,200 ppm calcium, 40 ppm iron(II) and 6 ppm sulfide with buffer to maintain the pH value at 7.0. The FeS dissolution rate and the water clarity after tests are applied as the criteria for performance evaluation. The FeS dissolution rate is calculated from the dissolved iron measured by ICP-OES, after the filtration using a 0.45 μm filter. A series of experiments were conducted to rank the performance of the raw materials and their combinations. A synergistic effect was found within a certain blend of the top performers. This synergistic blend was developed into a novel treatment package, which is capable of dissolving and dispersing the in-situ formed FeS. In the field water bottle test, the new product shows 25% lower MEC (minimum effective concentration) compared to the conventional THPS (tetrakis (hydroxymethyl)phosphonium sulfate). In a dynamic condition loop test with inline filter, the water treated with this formulation shows better injectivity compared to THPS. A field trial conducted in a 7,500 BWPD gathering facility in Permian Basin shows the synergistic blend to be effective in controlling in-situ formed FeS. This study systematically develops a novel iron sulfide control product combining the top-performing materials. The iron sulfide dissolution rate and synergistic effects are optimized for the blend. The cost-effectiveness is proved by dependency analysis and extensive laboratory data. The performance of the novel formulation was validated by field trial and laboratory tests.