Influence Factors and Elimination on Iron Content Using ICP-AES Method in Oilfield Produced Water

¹ Shaanxi Province Key Laboratory of Environmental Pollution Control and Reservoir Protection Technology of Oilfields, College of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an Shaanxi 710065, China
² No.4 Oil Production Plant, Changqing Oilfield Company, Yulin, Shaanxi 718500, China
³ No.2 Gas Production Plant, Changqing Oilfield Company, Yulin, Shaanxi, 718500, China
⁴ Xi’an Key Laboratory of Tight oil (Shale oil) Development, College of Petroleum Engineering, Xi’an Shiyou University, Xi’an, Shaanxi, 710065, China

^* Corresponding author: xie_juan@xsyu.edu.cn

Abstract

ICP-AES method can be used to determine multiple metallic elements simultaneously, and has the advantages of high sensitivity, good repeatability and high accuracy. In the paper, the detection limit of iron content was determined by stepwise dilution method. The influence of the cationic concentration on the determination of iron element was studied, and the matrix matching method was proposed to eliminate the influence. The results show that, the determination limit of Iron element is 0.01 mg·L-1. Because the other cationic content is several times or even tens of times as much as iron ions, it has a great influence on the determination results of Iron element. The effects of cationic concentration can be effectively eliminated by establishing a standard curve using matrix matching. After digestion pretreatment on the oil and gas field produce water, The standard adding recovery rate was between 95% and 105%, and the RSD is less than 4%. Compare this method with o-phenanthroline spectrophotometry, its relative error is within 5%. Therefore, ICP-AES method can fully meet the requirements of determination of iron content in oil field produce water, and greatly improves the efficiency and accuracy of the laboratory analysis of oil and as field wastewater.