Research and Application of Hydrogen Sulfide Absorbent for Acid Cleaning and Scale Removal

This paper analyzes the composition of the scale samples from the injected water and the pipe strings of Qinghai Gasi Oilfield and determines that the scale samples are mainly composed of carbonate components and contain 8%–10% ferrous sulfide. When hydrochloric acid is used as a scale solvent, it reacts with ferrous sulfide to generate highly toxic hydrogen sulfide gas, causing pipe string corrosion and personal injury. This paper presents the solution of synthesizing hydrogen sulfide absorbers to address this problem and systematically evaluates their various performances. In addition, the compatibility between the absorbent and the existing acid solution system is studied. The results show that the average sulfur capacity of the two hydrogen sulfide absorbents (BY-A, BY-B) is higher than 0.03 mg/g, and the average desulfurization efficiency is greater than 90%. In a hydrochloric acid solution with a concentration of 15%–25%, when a hydrogen sulfide absorbent with a concentration of 1% (volume ratio) is added, the hydrogen sulfide absorption efficiency is greater than 90%. By adding 0.5% (volume ratio) hydrogen sulfide absorbent to the existing acid system in the oilfield, the hydrogen sulfide absorption efficiency is greater than 90%. The hydrogen sulfide absorption speed is fast, which can meet the requirements for hydrogen sulfide concentration during the backflow of acidizing treatment. The hydrogen sulfide absorbent has good compatibility with the acid system and it does not affect the corrosion inhibition effect of the inhibitor. Furthermore, a rapid evaluation method for hydrogen sulfide absorbers has been designed and developed, and it is simple, feasible and reliable in results. This study innovatively develops efficient hydrogen sulfide absorbents, which have important practical significance for safe and efficient pickling and acidizing treatment of sulfur containing pipelines and reservoirs.